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Journal Cover Plant Physiology and Biochemistry
  [SJR: 1.041]   [H-I: 70]   [7 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0981-9428
   Published by Elsevier Homepage  [2969 journals]
  • Silybin content and overexpression of chalcone synthase genes in Silybum
           marianum L. plants under abiotic elicitation
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Hoda A.S. El-Garhy, Salah Khattab, Mahmoud M.A. Moustafa, Rania Abou Ali, Ahmed Z. Abdel Azeiz, Abeer Elhalwagi, Fadia El Sherif
      Silymarin, a Silybum marianum seed extract containing a mixture of flavonolignans including silybin, is being used as an antihepatotoxic therapy for liver diseases. In this study, the enhancing effect of gamma irradiation on plant growth parameters of S. marianum under salt stress was investigated. The effect of gamma irradiation, either as a single elicitor or coupled with salinity, on chalcone synthase (CHS) gene expression and silybin A + B yield was also evaluated. The silybin A + B content in S. marianum fruits was estimated by liquid chromatography–mass spectrometry (LC-MS/MS). An increase in silybin content was accompanied by up-regulation of the CHS1, CHS2 and CHS3 genes, which are involved in the silybin biosynthetic pathway. The highest silybin A + B production (0.77 g/100 g plant DW) and transcript levels of the three studied genes (100.2-, 91.9-, and 24.3-fold increase, respectively) were obtained with 100GY gamma irradiation and 4000 ppm salty water. The CHS2 and CHS3 genes were partially sequenced and submitted to the NCBI database under the accession numbers KT252908.1 and KT252909.1, respectively. Developing new approaches to stimulate silybin biosynthetic pathways could be a useful tool to potentiate the use of plants as renewable resources of medicinal compounds.


      PubDate: 2016-07-25T14:31:29Z
       
  • Kinetic commitment in the catalysis of glutamine synthesis by GS1 from
           Arabidopsis using 14N/15N and solvent isotope effects
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Caroline Mauve, Nicolas Giraud, Edouard R.A. Boex-Fontvieille, Ingrid Antheaume, Illa Tea, Guillaume Tcherkez
      Glutamine synthetase (GS, EC 6.3.1.2) catalyzes the production of glutamine from glutamate, ammonium and ATP. Although being essential in plants for N assimilation and recycling, kinetic commitments and transition states of the reaction have not been clearly established yet. Here, we examined 12C/13C, 14N/15N and H2O/D2O isotope effects in Arabidopsis GS1 catalysis and compared to the prokaryotic (Escherichia coli) enzyme. A14N/15N isotope effect (15 V/K ≈ 1.015, with respect to substrate NH4 +) was observed in the prokaryotic enzyme, indicating that ammonium utilization (deprotonation and/or amidation) was partially rate-limiting. In the plant enzyme, the isotope effect was inverse (15 V/K = 0.965), suggesting that the reaction intermediate is involved in an amidation-deamidation equilibrium favoring 15N. There was no 12C/13C kinetic isotope effect (13 V/K = 1.000), suggesting that the amidation step of the catalytic cycle involves a transition state with minimal alteration of overall force constants at the C-5 carbon. Surprisingly, the solvent isotope effect was found to be inverse, that is, with a higher turn-over rate in heavy water (D V ≈ 0.5), showing that restructuration of the active site due to displacement of H2O by D2O facilitates the processing of intermediates.


      PubDate: 2016-07-25T14:31:29Z
       
  • 24-Epibrassinolide ameliorates salt stress effects in the symbiosis
           Medicago truncatula-Sinorhizobium meliloti and regulates the nodulation in
           cross-talk with polyamines
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Miguel López-Gómez, Javier Hidalgo-Castellanos, Carmen Lluch, José A. Herrera-Cervera
      Brassinosteroids (BRs) are steroid plant hormones that have been shown to be involved in the response to salt stress in cross-talk with other plant growth regulators such as polyamines (PAs). In addition, BRs are involved in the regulation of the nodulation in the rhizobium-legume symbiosis through the alteration of the PAs content in leaves. In this work, we have studied the effect of exogenous 24-epibrassinolide (EBL) in the response to salinity of nitrogen fixation in the symbiosis Medicago truncatula-Sinorhizobium meliloti. Foliar spraying of EBL restored the growth of plants subjected to salt stress and provoked an increment of the nitrogenase activity. In general, PAs levels in leaves and nodules decreased by the salt and EBL treatments, however, the co-treatment with NaCl and EBL augmented the foliar spermine (Spm) concentration. This increment of the Spm levels was followed by a reduction of the membrane oxidative damage and a diminution of the proline accumulation. The effect of BRs on the symbiotic interaction was evaluated by the addition of 0.01, 0.1 and 0.5 μM EBL to the growing solution, which provoked a reduction of the nodule number and an increment of the PAs levels in shoot. In conclusion, foliar treatment with EBL had a protective effect against salt stress in the M. truncatula-S. meliloti symbiosis mediated by an increment of the Spm levels. Treatment of roots with EBL incremented PAs levels in shoot and reduced the nodule number which suggests a cross-talk between PAs and BRs in the nodule suppression and the protection against salt stress.


      PubDate: 2016-07-25T14:31:29Z
       
  • Silicon addition to soybean (Glycine max L.) plants alleviate zinc
           deficiency
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): M Blanca Pascual, Virginia Echevarria, M José Gonzalo, Lourdes Hernández-Apaolaza
      It is well established the beneficial role of silicon (Si) in alleviating abiotic stress. However, it remains poorly understood the mechanisms of the Si-mediated protection against metal deficiency, especially the zinc (Zn) one. Recently, it has been proposed that Si may act by an interaction with this biometal in the root apoplast contributing to its movement through the plant, as in the case of Fe deficiency. In the present work, the effect of initial or continuous Si doses in soybean Zn deficient plants has been studied. For that purpose, plants grown in hydroponic culture were treated with different Si doses (0.0, 0.5 and 1.0 mM) under Zn limiting conditions. SPAD index in leaves, several growth parameters, mineral content in the whole plant and the formation of Zn pools in roots were determined. An initial addition of 0.5 mM of Si to the nutrient solution led to an enhancement of plants growth, Zn and Si content in leaves, and a higher storage of Zn in the root apoplast. The results suggest that this treatment enhanced Zn accumulation on roots and its movement to shoots when needed, mitigating Zn deficiency symptoms.


      PubDate: 2016-07-20T14:06:51Z
       
  • Purification of recombinant tissue plasminogen activator (rtPA) protein
           from transplastomic tobacco plants
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Maryam Abdoli Nasab, Mokhtar Jalali Javaran, Rosa M. Cusido, Javier Palazon
      Plants are low cost platforms for the production of recombinant proteins, but their complexity renders the purification of plant recombinant proteins more difficult than proteins expressed in yeast or bacteria. Plastid transformation enables high-level expression of foreign genes and the accumulation of recombinant proteins in plastid organelles. Histidine (His) tags are widely used for affinity purification of recombinant proteins in a nickel column. The human tissue-type plasminogen activator (tPA) is one of the most important pharmaceutical recombinant proteins involved in the breakdown of blood clots in different parts of the body. The truncated form of the tissue plasminogen activator (K2S) has a longer plasma half-life, better diffusion into the clot, and higher fibrinolytic activity. In a construct designed to insert the K2S gene in the tobacco chloroplast, the sequence of six histidines and a factor Xa protease site was fused to the C-terminus of the K2S protein. The presence and amount of tPA recombinant protein in transplastomic tobacco plants was estimated by ELISA analysis using a specific antibody. The protein was purified from total soluble protein, insoluble protein aggregates and the protein was extracted from the isolated chloroplast using nickel resin and a chromatography column. After digestion of the purified protein with factor Xa, the presence of the purified tPA protein was confirmed by western blot analysis.


      PubDate: 2016-07-20T14:06:51Z
       
  • Arabidopsis thaliana MRP1 (AtABCC1) nucleotide binding domain contributes
           to arsenic stress tolerance with serine triad phosphorylation
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Ayan Raichaudhuri
      Multidrug resistance protein AtMRPs belong to the ATP binding cassette (ABC) transporter super family. ABC proteins are membrane proteins involved in the transport of a broad range of amphipathic organic anions across membranes. MRPs (ABCCs) are one of the highly represented subfamilies of ABC transporters. Plant MRPs also transport various glutathione conjugates across membranes. Arabidopsis thaliana MRP1 is already known to be involved in vacuolar storage of folates. Using heterologously expressed AtMRP1 in yeast and its C-terminal nucleotide binding domain (NBD2) in E scherichia coli, it has been shown that Casein kinase II (CKII) mediated phosphorylation is a potential regulator of AtMRP1 function. AtMRP1 showed enhanced tolerance towards arsenite As(III) in yeast. CKIIII/CKII mediated phosphorylation of AtMRP1 was found to be involved in As(III) mediated signaling. AtMRP1-NBD2 and its serine mutants showed distinct change in secondary structure in the presence of arsenite and methotrexate (MTX) controlled by serine triad phosphorylation. Results showed that AtMRP1 is important for vacuolar accumulation of antifolates as well as tolerance against arsenic, both of which involved phosphorylation in the serine triads at the C terminal NBD of AtMRP1. The experiments provide an important insight into the role of AtMRP1 serine triad phosphorylation under AsIII stress conditions.


      PubDate: 2016-07-20T14:06:51Z
       
  • Different metabolite profile and metabolic pathway with leaves and roots
           in response to boron deficiency at the initial stage of citrus rootstock
           growth
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Xiaochang Dong, Guidong Liu, Xiuwen Wu, Xiaopei Lu, Lei Yan, Riaz Muhammad, Asad Shah, Lishu Wu, Cuncang Jiang
      Boron (B) is a microelement required for higher plants, and B deficiency has serious negative effect on metabolic processes. We concentrated on the changes in metabolite profiles of trifoliate orange leaves and roots as a consequence of B deficiency at the initial stage of growth by gas chromatography-mass spectrometry (GC-MS)-based metabolomics. Enlargement and browning of root tips were observed in B-deficient plants, while any obvious symptom was not recorded in the leaves after 30 days of B deprivation. The distinct patterns of alterations in metabolites observed in leaves and roots due to B deficiency suggest the presence of specific organ responses to B starvation. The accumulation of soluble sugars was occurred in leaves, which may be attributed to down-regulated pentose phosphate pathway (PPP) and amino acid biosynthesis under B deficiency, while the amount of most amino acids in roots was increased, indicating that the effects of B deficiency on amino acids metabolism in trifoliate orange may be a consequence of disruptions in root tissues and decreased protein biosynthesis. Several important products of shikimate pathway were also significantly affected by B deficiency, which may be related to abnormal growth of roots induced by B deficiency. Conclusively, our results revealed a global perspective of the discriminative metabolism responses appearing between B-deprived leaves and roots and provided new insight into the relationship between B deficiency symptom in roots and the altered amino acids profiling and shikimate pathway induced by B deficiency during seedling establishment.


      PubDate: 2016-07-20T14:06:51Z
       
  • Genome-wide identification, characterization and expression profiling of
           LIM family genes in Solanum lycopersicum L.
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Khadiza Khatun, Arif Hasan Khan Robin, Jong-In Park, Nasar Uddin Ahmed, Chang Kil Kim, Ki-Byung Lim, Min-Bae Kim, Do-Jin Lee, Ill Sup Nou, Mi-Young Chung
      LIM domain proteins, some of which have been shown to be actin binding proteins, are involved in various developmental activities and cellular processes in plants. To date, the molecular defense-related functions of LIM family genes have not been investigated in any solanaceous vegetable crop species. In this study, we identified 15 LIM family genes in tomato (Solanum lycopersicum L.) through genome-wide analysis and performed expression profiling in different organs of tomato, including fruits at six different developmental stages. We also performed expression profiling of selected tomato LIM genes in plants under ABA, drought, cold, NaCl and heat stress treatment. The encoded proteins of the 15 tomato LIM genes were classified into two main groups, i.e., proteins similar to cysteine-rich proteins and plant-specific DAR proteins, based on differences in functional domains and variability in their C-terminal regions. The DAR proteins contain a so far poorly characterized zinc-finger-like motif that we propose to call DAR-ZF. Six of the 15 LIM genes were expressed only in flowers, indicating that they play flower-specific roles in plants. The other nine genes were expressed in all organs and at various stages of fruit development. SlβLIM1b was expressed relatively highly at the later stage of fruit development, but three other genes, SlWLIM2a, SlDAR2 and SlDAR4, were expressed at the early stage of fruit development. Seven genes were induced by ABA, five by cold, seven by drought, eight by NaCl and seven by heat treatment respectively, indicating their possible roles in abiotic stress tolerance. Our results will be useful for functional analysis of LIM genes during fruit development in tomato plants under different abiotic stresses.


      PubDate: 2016-07-20T14:06:51Z
       
  • Genome-wide identification and domain organization of lectin domains in
           cucumber
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Liuyi Dang, Els J.M. Van Damme
      Lectins are ubiquitous proteins in plants and play important roles in a diverse set of biological processes, such as plant defense and cell signaling. Despite the availability of the Cucumis sativus L. genome sequence since 2009, little is known with respect to the occurrence of lectins in cucumber. In this study, a total of 146 putative lectin genes belonging to 10 different lectin families were identified and localized in the cucumber genome. Domain architecture analysis revealed that most of these lectin gene sequences contain multiple domains, where lectin domains are linked with other domains, as such creating chimeric lectin sequences encoding proteins with dual activities. This study provides an overview of lectin motifs in cucumber and will help to understand their potential biological role(s).


      PubDate: 2016-07-20T14:06:51Z
       
  • The effect of kinetin on wheat seedlings exposed to boron
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Ahmet Eser, Tülin Aydemir
      The objective of this study was to examine relationship between boron (B) induced oxidative stress and antioxidant system in boron sensitive and tolerant wheat cultivars Bezostaya and Kutluk, and also to investigate whether Kinetin (KN) enhances the level of antioxidant system, relative growth, concentration of hydrogen peroxide (H2O2), malondialdehyde (MDA) and proline and chlorophyll content in both cultivars exposed to B stress. B treatments diminished growth and chlorophyll content whereas, it enhanced accumulation of H2O2, MDA and proline, and various antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and lipoxygenase (LOX) in the shoot and root of both cultivars. However, the follow-up application of KN to the B stressed plants improved growth and chlorophyll content and further enhanced the mentioned antioxidant enzymes and level of H2O2, MDA and proline. This study thus suggests that KN improves B tolerance of the studied cultivars grown under B toxicity.


      PubDate: 2016-07-20T14:06:51Z
       
  • Metabolomic profiling of the halophyte Prosopis strombulifera shows sodium
           salt- specific response
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Analía Llanes, Vicent Arbona, Aurelio Gómez-Cadenas, Virginia Luna
      Primary and secondary metabolite profiles were analyzed in roots and leaves of the halophytic shrub Prosopis strombulifera in response to control plants (no salt added in the growing media) and to lowering the osmotic potential to −1.0, −1.9, and −2.6 MPa generated by NaCl, Na2SO4, and the iso-osmotic combination of them at 24 h after reaching such potential. A rapid production of metabolites in response to sodium salt was found, which was correlated with modifications in growth parameters. Analysis of polar metabolite profiles by GC-MS rendered a total of 108 significantly altered compounds including 18 amino acids, 19 secondary metabolites, 23 carbohydrates, 13 organic acids, 4 indole acids, among others. Primary metabolites showed a differential response under the salt treatments, which was dependent on salt type and concentration, organ and age of plants. Most of identified compounds showed the strongest accumulation at the highest salt concentration assayed for Na2SO4-treated plants, which was correlated with damaging effects of sulfate anion on plant growth. Roots of NaCl-treated plants showed a higher number of altered metabolites (analyzed by UPLC-ESI-QqTOF-MS) compared to other treatments, while leaves of Na2SO4-treated plants showed the highest number of altered signals. A low degree of overlapping between secondary metabolites altered in roots and leaves of NaCl and Na2SO4-treated plants was found. However, when both NaCl and Na2SO4 salts were present plants always showed a lower number of altered metabolites. Three compounds were tentatively identified: tryptophan, lysophosphatidylcoline and 13-hydroxyoctadecadienoic acid. Increasing knowledge on P. strombulifera metabolism will contribute to unravel the underlying biochemical mechanism of salt tolerance.
      Graphical abstract image

      PubDate: 2016-07-20T14:06:51Z
       
  • Proteomic analysis of JAZ interacting proteins under methyl jasmonate
           treatment in finger millet
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Saswati Sen, Sangeeta Kundu, Samir Kr. Dutta
      Jasmonic acid (JA) signaling pathway in plants is activated against various developmental processes as well as biotic and abiotic stresses. The Jasmonate ZIM-domain (JAZ) protein family, the key regulator of plant JA signaling pathway, also participates in phytohormone crosstalk. This is the first study revealing the in vivo interactions of finger millet (Eleusine coracana (L.) Gaertn.) JAZ protein (EcJAZ) under methyl jasmonate (MJ) treatment. The aim of the study was to explore not only the JA signaling pathway but also the phytohormone signaling crosstalk of finger millet, a highly important future crop. From the MJ-treated finger millet seedlings, the EcJAZ interacting proteins were purified by affinity chromatography with the EcJAZ-matrix. Twenty-one proteins of varying functionalities were successfully identified by MALDI-TOF-TOF Mass spectrometry. Apart from the previously identified JAZ binding proteins, most prominently, EcJAZ was found to interact with transcription factors like NAC, GATA and also with Cold responsive protein (COR), etc. that might have extended the range of functionalities of JAZ proteins. Moreover, to evaluate the interactions of EcJAZ in the JA-co-receptor complex, we generated ten in-silico models containing the EcJAZ degron and the COI1-SKP1 of five monocot cereals viz., rice, wheat, maize, Sorghum and Setaria with JA-Ile or coronatine. Our results indicated that the EcJAZ protein of finger millet could act as the signaling hub for the JA and other phytohormone signaling pathways, in response to a diverse set of stressors and developmental cues to provide survival fitness to the plant.


      PubDate: 2016-07-16T13:59:19Z
       
  • MYC2, MYC3, and MYC4 function redundantly in seed storage protein
           accumulation in Arabidopsis
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Chenhao Gao, Shuanghui Qi, Kaige Liu, Dong Li, Changyu Jin, Zhuowei Li, Gengqing Huang, Jiangbo Hai, Meng Zhang, Mingxun Chen
      Basic helix-loop-helix transcription factors (TFs), namely MYC2, MYC3, and MYC4, interact with Jasmonate Zim-domain proteins and are their direct targets. These TFs have been shown to function synergistically to control Arabidopsis growth and development. Our results showed similar MYC2, MYC3, and MYC4 expression patterns during Arabidopsis seed development, which remained relatively high during seed mid-maturation. MYC2, MYC3, and MYC4 acted redundantly in seed size, weight control, and in regulating seed storage protein accumulation. Triple mutants produced the largest seeds and single and double mutants’ seeds were much larger than those of wild type. The weight of triple mutants’ seeds was significantly higher than that of wild-type seeds, which was accompanied by an increase in seed storage protein contents. Triple mutants’ seeds presented a marked decrease in 2S amounts relative to those in wild-type seeds. Liquid chromatography tandem mass spectra sequencing results indicated that both the relative abundance and the peptide number of CRA1 and CRU3 were greatly increased in triple mutants compared to wild type. The expression of 2S1–2S5 decreased and that of CRA1 and CRU3 increased in triple mutants relative to those in wild types during seed development, which might have contributed to the low 2S and high 12S contents in triple mutants. Our results contribute to understanding the function of MYC2, MYC3, and MYC4 on seed development, and provide promising targets for genetic manipulations of protein-producing crops to improve the quantity and quality of seed storage proteins.


      PubDate: 2016-07-16T13:59:19Z
       
  • Identification of structural elements involved in fine-tuning of the
           transport activity of the rice ammonium transporter OsAMT1;3
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Dongli Hao, Shunying Yang, Yanan Huang, Yanhua Su
      Ammonium transporters (AMTs) are major routes for plant uptake of the NH4 +-form nitrogen. Plant AMTs mediate predominantly the uptake of NH4 + and to a lesser extent, its organic analog methylammonium (MeA+). Mutagenesis studies on potential phosphorylation residues have achieved solid recognition that alteration of the phosphorylation status can result in allosteric regulation and impair the functionality of plant AMTs. However, molecular insights to the fine-tuning of a functional ammonium transporter remain less clear. In this report, we demonstrate that the rice root expressed OsAMT1;3 (Oryza sativa ammonium transporter 1;3) functions as a typical high-affinity NH4 + transporter and is weakly permeable to MeA+ using growth assays in NH4 + uptake defective yeast cells and electrophysiological measurements in Xenopus oocytes. Upon screening of six point mutations generated with the transporter, we identified two amino acid residues involved in the functional modulation of OsAMT1;3. The H199E mutation caused loss of transport activity whereas other five mutations retained the functionality of OsAMT1;3. Furthermore, the L56F mutation enabled respectively 5- and 3.5 -fold increased capability for NH4 + and MeA+ uptake with several-fold decreased affinity (K m ) and accelerated V max values. Surprisingly, yeast cells expressing the L56F mutation shown increased Na+ toxicity leading to a speculation that enhanced Na+ permeation occurred with this mutation. The phenomenon was further supported by the observation of significant Na+ uptake current in oocytes. Our results seemingly support a speculation that the L56F mutation of OsAMT1;3 widens the substrate passage tunnel and allows enhanced permeability to NH4 + and larger ions MeA+ and Na+.


      PubDate: 2016-07-16T13:59:19Z
       
  • Impact of cadmium stress on two maize hybrids
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Zuzana Vatehová, Anna Malovíková, Karin Kollárová, Danica Kučerová, Desana Lišková
      Some physiological parameters and composition of the root cell walls of two maize hybrids (monocots), the sensitive Novania and the tolerant Almansa were studied after treatment with cadmium cations. After 10 days of Cd2+ treatment (1 × 10−5 M and 5 × 10−5 M), plant growth inhibition, in the sensitive hybrid in particular, as well as a certain alteration in root structure and pigment content were observed. The Cd2+ accumulation was ten times higher in the roots than in the shoots. Chemical analyses and atomic absorption spectroscopy proved that Cd2+ modified the composition of the root cell walls by a significant increase in the content of alkali-soluble polysaccharide fractions, particularly in the tolerant hybrid. An increase in the content of phenolic compounds, mainly in the tolerant hybrid, and a decrease in protein content were observed in the presence of Cd2+ in the alkali fractions. The results indicate that the changes in the cell wall polysaccharide fractions and their proportion to lignin and cellulose are obviously involved in the tolerance and/or defence against Cd2+ of the maize hybrids studied.
      Graphical abstract image

      PubDate: 2016-07-16T13:59:19Z
       
  • Involvement of vacuolar processing enzyme SlVPE5 in post-transcriptional
           process of invertase in sucrose accumulation in tomato
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Ning Wang, Narendra Duhita, Toru Ariizumi, Hiroshi Ezura
      Enhancing the flavor of fruits plays a fundamental role in improving fruit quality, and volatile compositions as well as acid and sugar accumulation are significant factors that have an impact on the acceptability of sensory responses by human beings. Vacuoles in plants not only function as cell compartments that store amino acids, sugars and other metabolites but also act as lytic organelles where vacuolar proteins are post-translationally processed into mature forms or degraded by the action of vacuolar processing enzyme (VPE). We have previously characterized VPE genes (SlVPE1-5) during fruit development in tomato and discovered that the VPE enzyme activity negatively interfered with sugar accumulation in mature fruits. Comparative proteomic analysis demonstrated that acid invertase was one of the molecular targets of SlVPE5, which is involved in the hydrolysis of sucrose. This study also showed that decreased VPE enzyme activity due to suppression of SlVPE5 by RNAi strategy (RNAi-SlVPE5) accompanied with decreased enzyme activity of acid invertase. Further, we identified the enzyme activity of acid invertase was not well correlated with mRNA levels in the RNAi-SlVPE5 line. These results suggest that SlVPE5 regulates post-transcriptional processing through de novo synthesis of the acid invertase protein to suppress enzyme activity, thereby eventually ensuring sucrose hydrolysis.


      PubDate: 2016-07-16T13:59:19Z
       
  • Magnesium decreases leaf scald symptoms on rice leaves and preserves their
           photosynthetic performance
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): S.D. Tatagiba, F.M. DaMatta, F.A. Rodrigues
      The aim of this study was to investigate the effect of magnesium (Mg) on the photosynthetic gas exchange parameters ([net CO2 assimilation rate (A), stomatal conductance (g s), and internal CO2 concentration (C i)], chlorophyll (Chl) fluorescence a parameters {minimal fluorescence (F 0), maximum fluorescence (F m), maximum quantum yield of photosystem II (F v/F m), photochemical quenching coefficient (q p), yield of photochemistry [Y(II)], yield of regulated energy dissipation [Y(NPQ)] and yield of non-regulated dissipation losses [Y(NO)]} as well as on the concentrations of chloroplastidic pigments in rice plants grown in a nutrient solution containing 0.5 or 1.5 mM of Mg (-Mg or + Mg plants, respectively) and non-inoculated or inoculated with Monographella albescens. A higher Mg supply decreased the leaf scald symptoms in addition to partially preserving the photosynthetic performance of rice leaves challenged with M. albescens. Photosynthetic impairments were associated with photochemical and biochemical dysfunctions at the chloroplast level. The images of Chl a fluorescence evidenced increases in both the Y(II) and q p coupled with decreases in Y(NPQ) associated with a higher Mg supply regardless of inoculation, suggesting increased electron transport rates and lower energy dissipation as heat. Notably, as the leaf scald developed, the use of light energy through photochemical reactions was continuously lost, especially for the inoculated -Mg plants. Interestingly, the lower values for F 0, F m, and F v/F m for -Mg plants were associated with greater photochemical dysfunctions and a progressive loss of photosynthetic pigments during the infection process of M. albescens. The underlying mechanism through which Mg can affect rice resistance against M. albescens remains to be fully elucidated.


      PubDate: 2016-07-12T13:44:21Z
       
  • Sulphur interferes with selenium accumulation in Tartary buckwheat plants
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Aleksandra Golob, Drena Gadžo, Vekoslava Stibilj, Mirha Djikić, Teofil Gavrić, Ivan Kreft, Mateja Germ
      Tartary buckwheat (Fagopyrum tataricum Gaertn.) and common buckwheat (Fagopyrum esculentum Moench.) plants grown in the field were treated foliarly with 126 μM solutions of selenate and/or sulphate in order to study the effect of sulphur (S) on selenium (Se) concentration in plants. In both species, the concentration of Se in all plant parts was similar in control and S treated plants. In Tartary buckwheat the concentration of Se was higher in S and Se treated plants than in plants treated with Se alone. S was shown to enhance Se accumulation in Tartary buckwheat. It was also shown that it is possible to produce grain and herb of Tartary and common buckwheat containing appropriate amounts of Se for food without affecting the yield of the plants.
      Graphical abstract image

      PubDate: 2016-07-12T13:44:21Z
       
  • Molecular characterization of biotic and abiotic stress-responsive MAP
           kinase genes, IbMPK3 and IbMPK6, in sweetpotato
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Ho Soo Kim, Sung-Chul Park, Chang Yoon Ji, Seyeon Park, Jae Cheol Jeong, Haeng-Soon Lee, Sang-Soo Kwak
      Plants are continually exposed to numerous environmental stresses. To decrease damage caused by these potentially detrimental factors, various stress-related signaling cascades are activated in plants. One such stress-responsive signaling pathway, the mitogen-activated protein kinase (MAPK) module, plays a critical role in diverse plant stress responses. Here, we functionally characterized biotic and abiotic stress-responsive MAPK genes, IbMPK3 and IbMPK6, from sweetpotato. IbMPK3/6 contain totally 11 MAPK conserved subdomains and the phosphorylating motif TEY. Bacterially expressed IbMPK3/6 could be autophosphorylated in vitro, and these proteins phosphorylated universal kinase substrate, such as myelin basic protein. IbMPK3/6 transcripts were expressed in leaf, stem, and root of sweetpotato cultivars with storage roots of various colors. IbMPK3 and IbMPK6 were induced by various biotic/abiotic stress treatments. Furthermore, the kinase activity of IbMPK3/6 was induced during early NaCl, SA, H2O2, and ABA treatment. IbMPK3/6 were predominantly localized to the nucleus. To determine the biological functions of IbMPK3/6, we transiently expressed the IbMPK genes in tobacco (Nicotiana benthamiana) leaves, which resulted in enhanced tolerance to bacterial pathogen and increased expression of pathogenesis-related (PR) genes. These data demonstrate that IbMPK3 and IbMPK6 play significant roles in plant responses to environmental stress.


      PubDate: 2016-07-12T13:44:21Z
       
  • Expression of a repressor form of the Arabidopsis thaliana transcription
           factor TCP16 induces the formation of ectopic meristems
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Nora G. Uberti-Manassero, Ezequiel R. Coscueta, Daniel H. Gonzalez
      Plants that express a fusion of the Arabidopsis thaliana class I TCP transcription factor TCP16 to the EAR repressor domain develop several phenotypic alterations, including rounder leaves, short petioles and pedicels, and delayed elongation of sepals, petals and anthers. In addition, these plants develop lobed cotyledons and ectopic meristems. Ectopic meristems are formed on the adaxial side of cotyledon petioles and arise from a cleft that is formed at this site. Analysis of the expression of reporter genes indicated that meristem genes are reactivated at the site of emergence of ectopic meristems, located near the bifurcation of cotyledon veins. The plants also show increased transcript levels of the boundary-specific CUP-SHAPED COTYLEDON (CUC) genes. The results suggest that TCP16 is able to modulate the induction of meristematic programs and the differentiation state of plant cells.


      PubDate: 2016-07-12T13:44:21Z
       
  • The molecular cloning and functional characterization of MdMYC2, a bHLH
           transcription factor in apple
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Jian-Ping An, Hao-Hao Li, Lai-Qing Song, Ling Su, Xin Liu, Chun-Xiang You, Xiao-Fei Wang, Yu-Jin Hao
      The basic helix-loop-helix (bHLH) Leu zipper transcription factor MYC2 is an important regulator in the Jasmonic acid (JA) signaling pathway. In this study, the apple MdMYC2 gene was isolated and cloned on the basis of its homology with Arabidopsis thaliana MYC2. Quantitative real time PCR (qRT-PCR) analysis demonstrated that MdMYC2 transcripts were induced by Methyl Jasmonate (MeJA) treatment and wounding. The MdMYC2 protein interacted with itself and bound the G-Box motif of the AtJAZ3 gene. MdMYC2 interacted with the MdJAZ2 protein, which is a repressor protein in the JA signaling pathway. Furthermore, we obtained transgenic apple calli that either overexpressed or suppressed the MdMYC2 gene. Expression analysis with qRT-PCR demonstrated that the transcript levels of JA-regulated anthocyanin biosynthetic genes, such as MdDFR, MdUF3GT, MdF3H and MdCHS, were markedly up-regulated in the MdMYC2 overexpressing calli and down-regulated in the suppressing calli compared with the WT control. As a result, the overexpressing calli produced more anthocyanin, and the suppressing calli produced less. Finally, the MdMYC2 gene was ectopically expressed in Arabidopsis. Both phenotypic investigation and expression analysis demonstrated that the MdMYC2 transgenic Arabidopsis lines were more sensitive to MeJA than the WT control. Together, these results indicate that the apple MdMYC2 gene plays a vital role in the JA response.


      PubDate: 2016-07-12T13:44:21Z
       
  • Physiological and biochemical characterization of two Amaranthus species
           under Cr(VI) stress differing in Cr(VI) tolerance
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Gausiya Bashri, Parul Parihar, Rachana Singh, Samiksha Singh, Vijay Pratap Singh, Sheo Mohan Prasad
      The present study was undertaken to evaluate Cr(VI) toxicity tolerance in two Amaranthus species viz. Amaranthus viridis and Amaranthus cruentus exposed to hexavalent chromium [Cr(VI)] stress. To ascertain this, both Amaranthus species were grown under various concentrations (0, 10 and 50 μM) of Cr(VI) in the hydroponic system. After 7 days of Cr(VI) treatment, various traits such as growth, Cr accumulation, photochemistry of photosystem II (PS II) (JIP-test), oxidative stress and antioxidant defense system were analyzed. Cr(VI) treatments caused inhibition in growth and PS II photochemistry, which was accompanied with increased accumulation of Cr that results into enhanced generation of reactive oxygen species (ROS): O2 − and H2O2, which subsequently induced the peroxidation of lipids and leakage of electrolyte in both the Amaranthus species. Cr(VI) accumulation, lipid peroxidation and electrolyte leakage were more pronounced in A. viridis than in A. cruentus. On the other hand, A. cruentus seedlings showed higher activities of enzymatic antioxidants: SOD, POD, CAT and GST, and non-enzymatic antioxidants: cysteine and non-protein thiols (NP-SH) levels than A. viridis. The overall results suggest that A. cruentus is more tolerant than A. viridis due to its higher antioxidant defense system that protected seedlings under Cr(VI) stress.


      PubDate: 2016-07-07T12:49:49Z
       
  • Genome-wide characterization of pectin methyl esterase genes reveals
           members differentially expressed in tolerant and susceptible wheats in
           response to Fusarium graminearum
    • Abstract: Publication date: November 2016
      Source:Plant Physiology and Biochemistry, Volume 108
      Author(s): Alessandra Zega, Renato D’Ovidio
      Pectin methyl esterase (PME) genes code for enzymes that are involved in structural modifications of the plant cell wall during plant growth and development. They are also involved in plant-pathogen interaction. PME genes belong to a multigene family and in this study we report the first comprehensive analysis of the PME gene family in bread wheat (Triticum aestivum L.). Like in other species, the members of the TaPME family are dispersed throughout the genome and their encoded products retain the typical structural features of PMEs. qRT-PCR analysis showed variation in the expression pattern of TaPME genes in different tissues and revealed that these genes are mainly expressed in flowering spikes. In our attempt to identify putative TaPME genes involved in wheat defense, we revealed a strong variation in the expression of the TaPME following Fusarium graminearum infection, the causal agent of Fusarium head blight (FHB). Particularly interesting was the finding that the expression profile of some PME genes was markedly different between the FHB-resistant wheat cultivar Sumai3 and the FHB-susceptible cultivar Bobwhite, suggesting a possible involvement of these PME genes in FHB resistance. Moreover, the expression analysis of the TaPME genes during F. graminearum progression within the spike revealed those genes that responded more promptly to pathogen invasion.


      PubDate: 2016-07-07T12:49:49Z
       
  • Oxidative stress in spring barley and common radish exposed to quaternary
           ammonium salts with hexafluorophosphate anion
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Robert Biczak, Arkadiusz Telesiński, Barbara Pawłowska
      Quaternary ammonium salts (QAS), including ionic liquids (ILs), constitute a huge group of substances, which due to their desirable physical and chemical properties still attracts great interest in many industrial sectors. An increased concentration of this compound in the environment may lead to the contamination of the natural environment and may pose a potential threat to all organisms, including terrestrial higher plants. The present study demonstrates the interaction of three QAS with PF6 − anions – tetramethylammonium [TMA][PF6], tetrabutylammonium [TBA][PF6], and tetrahexylammonium [THA][PF6] hexafluorophosphates – and its impact on the physiological and biochemical changes in spring barley seedlings and common radish plants. A similar study was also carried out by introducing the inorganic salt – ammonium hexafluorophosphate [A][PF6] to the soil; the results showed the soil became highly toxic to both plants. All the salts used led to significant changes in the metabolism of both spring barley and common radish which can be evidenced, for example, by a decrease in the content of chlorophyll a (Chla), chlorophyll b (Chlb), and total chlorophyll (Chla + b), as well as carotenoids (Car). The decrease in assimilation pigments was linearly correlated with an increasing concentration of QAS in the soil. QAS and [A][PF6] led to the formation of oxidative stress in both experimental plants, as evidenced by an increase in malondialdehyde (MDA) content in their cells and the changes in H2O2 level. In response to stress, the plants synthesized enzymatic free radicals (ROS) scavengers that lead to changes in the activity of superoxide dismutase (SOD) and catalase (CAT), as well as significantly increased peroxidase (POD) activity. A decrease in the content of assimilation pigments and an increased POD activity are the most reliable indices of oxidative stress, and concurrently the signs of premature plants aging. Common radish proved to be more resistant to the presence of QAS in the soil compared to spring barley.
      Graphical abstract image

      PubDate: 2016-06-18T18:22:11Z
       
  • Arbuscular mycorrhiza improves yield and nutritional properties of onion
           (Allium cepa)
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Piotr Rozpądek, Maria Rąpała-Kozik, Katarzyna Wężowicz, Anna Grandin, Stefan Karlsson, Rafał Ważny, Teresa Anielska, Katarzyna Turnau
      Improving the nutritional value of commonly cultivated crops is one of the most pending problems for modern agriculture. In natural environments plants associate with a multitude of fungal microorganisms that improve plant fitness. The best described group are arbuscular mycorrhizal fungi (AMF). These fungi have been previously shown to improve the quality and yield of several common crops. In this study we tested the potential utilization of Rhizophagus irregularis in accelerating growth and increasing the content of important dietary phytochemicals in onion (Allium cepa). Our results clearly indicate that biomass production, the abundance of vitamin B1 and its analogues and organic acid concentration can be improved by inoculating the plant with AM fungi. We have shown that improved growth is accompanied with up-regulated electron transport in PSII and antioxidant enzyme activity.
      Graphical abstract image

      PubDate: 2016-06-18T18:22:11Z
       
  • Protein synthesis is the most sensitive process when potassium is
           substituted by sodium in the nutrition of sugar beet (Beta vulgaris)
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Franziska Faust, Sven Schubert
      Potassium ions (K+) and sodium ions (Na+) share many physical and chemical similarities. However, their interchangeability in plant nutrition is restricted. Substitution studies showed that K+ can be replaced by Na+ to a large extent in the nutrition of Beta vulgaris L. However, the extent of substitution without negative impacts is not unlimited. The aim of the present study was to identify the process which is most sensitive during the substitution of K+ by Na+ in nutrition of young sugar beet plants. We focused on transpiration, growth, and net protein synthesis. Plants were grown under controlled environmental conditions. With transfer of seedlings into nutrient solution, plants were cultivated in different substitution treatments. For all treatments the sum of K+ and Na+ (applied as chloride) was fixed to 4 mM. The extent of substitution of K+ by Na+ in the nutrient solution was varied from low (0.25% substitution: 3.99 mM K+, 0.01 mM Na+) to almost complete substitution (99.75% substitution: 0.01 mM K+, 3.99 mM Na+). The supply of 3.99 mM K+ in 0.25% substitution treatment guaranteed the absence of K+ deficiency. Transpiration was not affected by the substitution. Growth was inhibited at a substitution level of 99.75%. Net protein synthesis was already affected at a substitution level of 97.50% (0.10 mM K+, 3.90 mM Na+). Hence, net protein synthesis was most sensitive to the substitution and limited the extent of substitution of K+ by Na+ in the nutrition of young sugar beet plants.


      PubDate: 2016-06-18T18:22:11Z
       
  • Quinclorac-habituation of bean (Phaseolus vulgaris) cultured cells is
           related to an increase in their antioxidant capacity
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Asier Largo-Gosens, María de Castro, Ana Alonso-Simón, Penélope García-Angulo, José L. Acebes, Antonio Encina, Jesús M. Álvarez
      The habituation of bean cells to quinclorac did not rely on cell wall modifications, contrary to what it was previously observed for the well-known cellulose biosynthesis inhibitors dichlobenil or isoxaben. The aim of the present study was to investigate whether or not the bean cells habituation to quinclorac is related to an enhancement of antioxidant activities involved in the scavenging capacity of reactive oxygen species. Treating non-habituated bean calluses with 10 μM quinclorac reduced the relative growth rate and induced a two-fold increase in lipid peroxidation. However, the exposition of quinclorac-habituated cells to a concentration of quinclorac up to 30 μM neither affected their growth rate nor increased their lipid peroxidation levels. Quinclorac-habituated calluses had significantly higher constitutive levels of three antioxidant activities (class-III peroxidase, glutathione reductase, and superoxide dismutase) than those observed in non-habituated calluses, and the treatment of habituated calluses with 30 μM quinclorac significantly increased the level of class III-peroxidase and superoxide dismutase. The results reported here indicate that the process of habituation to quinclorac in bean callus-cultured cells is related, at least partially, to the development of a stable antioxidant capacity that enables them to cope with the oxidative stress caused by quinclorac. Class-III peroxidase and superoxide dismutase activities could play a major role in the quinclorac-habituation. Changes in the antioxidant status of bean cells were stable, since the increase in the antioxidant activities were maintained in quinclorac-dehabituated cells.
      Graphical abstract image

      PubDate: 2016-06-18T18:22:11Z
       
  • Gibberellins regulate the stem elongation rate without affecting the
           mature plant height of a quick development mutant of winter wheat
           (Triticum aestivum L.)
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Ning Zhang, Yong-Dun Xie, Hui-Jun Guo, Lin-Shu Zhao, Hong-Chun Xiong, Jia-Yu Gu, Jun-Hui Li, Fu-Quan Kong, Li Sui, Zi-Wei Zhao, Shi-Rong Zhao, Lu-Xiang Liu
      Gibberellin (GA) is essential for determining plant height. Alteration of GA content or GA signaling results in a dwarf or slender phenotype. Here, we characterized a novel wheat mutant, quick development (qd), in which GA regulates stem elongation but does not affect mature plant height. qd and wild-type plants did not exhibit phenotypic differences at the seedling stage. From jointing to heading stage, qd plants were taller than wild-type plants due to elongated cells. However, wild-type and qd plants were the same height at heading. Unlike wild-type plants, qd plants were sensitive to exogenous GA due to mutation of Rht-B1. With continuous GA stimulation, qd seedlings and adult plants were taller than wild-type. Thus, the GA content of qd plants might differ from that of wild-type during the growth process. Analysis of GA biosynthetic gene expression verified this hypothesis and showed that TaKAO, which is involved in catalyzing the early steps of GA biosynthesis, was differentially expressed in qd plants compared with wild-type. The bioactive GA associated gene TaGA20ox was downregulated in qd plants during the late growth stages. Measurements of endogenous GA content were consistent with the gene-expression analysis results. Consistent with the GA content variation, the first three basal internodes were longer and the last two internodes were shorter in qd than in wild-type plants. The qd mutant might be useful in dissecting the mechanism by which GA regulates stem-growing process, and it may be serve as a GA responsive semi-dwarf germplasm in breeding programs.


      PubDate: 2016-06-18T18:22:11Z
       
  • Physiological characterization and true-to-typeness evaluation of
           in vitro and ex vitro seedlings of Pinus elliottii: A
           contribution to breeding programs
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Sandra Nunes, Conceição Santos, José Moutinho-Pereira, Carlos Correia, Helena Oliveira, José Miguel Ferreira de Oliveira, Vanessa Tolentino Pereira, Tânia Almeida, Liliana Marum, Maria Celeste Dias
      Pinus elliottii var. elliottii is a pine species with enormous economic value particularly for timber and resin industries, and is subject of high pressure for genetic improvement and cloning elite genotypes. We have recently developed a robust micropropagation protocol for this species. Plantlets performance needs to be evaluated to validate this protocol for further mass propagation. Micropropagated plantlets and seed-derived plants with similar age and shoot length were compared regarding photosynthesis, carbohydrates and pigments content, water status, DNA content and cell cycle dynamics. Micropropagated plantlets had an overall physiological performance similar to seed-derived plants. In particular, except for the transpiration rate (E), CO2 assimilation rate (A) and total soluble sugars (TSS) content, no major differences between plantlets and seedlings in terms of relative water content (RWC), chlorophyll a fluorescence and pigments content were found. Genetic fidelity analyses support that the micropropagation protocol neither induce DNA content changes nor alterations in cell cycle dynamics.


      PubDate: 2016-06-15T09:03:18Z
       
  • RNA interference of the nicotine demethylase gene CYP82E4v1 reduces
           nornicotine content and enhances Myzus persicae resistance in Nicotiana
           tabacum L
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Dan Zhao, Li-Jun Qin, De-Gang Zhao
      The CYP82E4v1 gene was identified to encode nicotine demethylase, which catalyzed the conversion of nicotine to nornicotine. In this study, we constructed CYP82E4v1-RNAi vector and genetically transformed tobacco variety K326. The determination results of nicotine and nornicotine content via HPLC demonstrated that there was significant increase of nicotine content and reduction of nornicotine content in transgenic plants compared with those in wild-type plants. Exogenous application of IAA or GA3 could reduce the nicotine content in tobaccos, while ABA or 6-BA could increase the content of nicotine. And the more significant difference of nicotine content change in transgenic plants. Aphid-inoculation experiment demonstrated the number of aphid population in transgenic plants was significantly lower than wild-type plants at 12 d after aphid-inoculation. Meanwhile, the activity of AOEs and PAL in transgenic and wild-type tobacco plants after aphid-inoculation was measured. At 3 d after aphid-inoculation, both AOEs and PAL activity were significantly higher than controls, including wild-type plants with aphid-inoculation and transgenic plants with mock-inoculation. Also, the relative expression of these genes involved in salicylic acid/jasmonic acid (SA/JA) signaling pathways was analyzed at different stages after aphid-inoculation and the results demonstrated that there was significantly higher expression of JA-induced LOX gene in both transgenic and wild-type plants inoculated by aphid than the non-inoculated ones while no significant difference in the expression of SA-induced PR-1a gene among them was found, which indicated the JA-mediated resistance response was activated during aphid infestation. Moreover, although the expression level of BGL (another JA-induced gene) was less significant between the two inoculated tobaccos, it was significantly higher than the plant without inoculation, which was 1.4 and 2.2 folds higher than the non-inoculated controls respectively. To sum up, the improvement of aphid-resistance in transgenic tobaccos was based on nicotine accumulation which might cause nerve and antifeed toxicity and JA-mediated resistance response by enhancing the activities of AOEs and PAL.


      PubDate: 2016-06-15T09:03:18Z
       
  • Characterization of plant growth promoting traits of bacterial isolates
           from the rhizosphere of barley (Hordeum vulgare L.) and tomato (Solanum
           lycopersicon L.) grown under Fe sufficiency and deficiency
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): M. Scagliola, Y. Pii, T. Mimmo, S. Cesco, P. Ricciuti, C. Crecchio
      Plant Growth Promoting Bacteria (PGPB) are considered a promising approach to replace the conventional agricultural practices, since they have been shown to affect plant nutrient-acquisition processes by influencing nutrient availability in the rhizosphere and/or those biochemical processes determining the uptake at root level of nitrogen (N), phosphorus (P), and iron (Fe), that represent the major constraints for crop productivity worldwide. We have isolated novel bacterial strains from the rhizosphere of barley (Hordeum vulgare L.) and tomato (Solanum lycopersicon L.) plants, previously grown in hydroponic solution (either Fe deficient or Fe sufficient) and subsequently transferred onto an agricultural calcareous soil. PGPB have been identified by molecular tools and characterized for their capacity to produce siderophores and indole-3-acetic acid (IAA), and to solubilize phosphate. Selected bacterial isolates, showing contemporarily high levels of the three activities investigated, were finally tested for their capacity to induce Fe reduction in cucumber roots two isolates, from barley and tomato plants under Fe deficiency, significantly increased the root Fe-chelate reductase activity; interestingly, another isolate enhanced the reduction of Fe-chelate reductase activity in cucumber plant roots, although grown under Fe sufficiency.


      PubDate: 2016-06-15T09:03:18Z
       
  • Chilling temperature stimulates growth, gene over-expression and
           podophyllotoxin biosynthesis in Podophyllum hexandrum Royle
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): De Long Yang, Ping Sun, Meng Fei Li
      Podophyllotoxin (PPT) and its derivatives, isolated from the rhizome of Podophyllum hexandrum Royle (P. hexandrum), are typically used in clinical settings for anti-cancer and anti-virus treatments. Empirical studies have verified that P. hexandrum had stronger tolerance to chilling, due to involving PPT accumulation in rhizome induced by cold stress. However, the cold-adaptive mechanism and its association with PPT accumulation at a molecular level in P. hexandrum are still limited. In this study, the morpho-physiological traits related to plant growth, PPT accumulation and key gene expressions controlling PPT biosynthesis were assessed by exposing P. hexandrum seedlings to different temperatures (4 °C and 10 °C as chilling stress and 22 °C as the control). The results showed that chilling significantly increased chlorophyll content, net photosynthetic rate, stomatal conductance, and plant biomass, whereas it greatly decreased transpiration rates and intercellular CO2 concentration. Compared to the control, the chilling treatments under 4 °C and 10 °C conditions induced a 5.00- and 3.33-fold increase in PPT contents, respectively. The mRNA expressions of six key genes were also up-regulated by chilling stresses. The findings are useful in understanding the molecular basis of P. hexandrum response to chilling.


      PubDate: 2016-06-15T09:03:18Z
       
  • Cumulative effect of heterologous AtWRI1 gene expression and endogenous
           BjAGPase gene silencing increases seed lipid content in Indian mustard
           Brassica juncea
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Surajit Bhattacharya, Natasha Das, Mrinal K. Maiti
      The production of vegetable oil in many countries of the world, including India has not been able to keep pace with the increasing requirement, leading to a very large gap in the demand-supply chain. Thus, there is an urgent need to increase the yield potential of the oilseed crops so as to enhance the storage lipid productivity. The present study describes a novel metabolic engineering ploy involving the constitutive down-regulation of endogenous ADP-glucose pyrophosphorylase (BjAGPase) enzyme and the seed-specific expression of WRINKLED1 transcription factor (AtWRI1) from Arabidopsis thaliana in Indian mustard (Brassica juncea) with an aim to divert the photosynthetically fixed carbon pool from starch to lipid synthesis in the seeds for the enhanced production of storage lipids in the seeds of transgenic mustard plants. The starch content, in both the vegetative leaf and developing seed tissues of the transgenic B. juncea lines exhibited a reduction by about 45–53% compared to the untransformed control, whereas the soluble sugar content was increased by 2.4 and 1.3-fold in the leaf and developing seed tissues, respectively. Consequently, the transgenic lines showed a significant enhancement in total seed lipid content ranging between 7.5 and 16.9%. The results indicate that the adopted metabolic engineering strategy was successful in significantly increasing the seed oil content. Therefore, findings of our research suggest that the metabolic engineering strategy adopted in this study for shifting the anabolic carbon flux from starch synthesis to lipid biosynthesis can be employed for increasing the storage lipid content of seeds in other plant species.


      PubDate: 2016-06-15T09:03:18Z
       
  • Effect of exogenous GA3 and its inhibitor paclobutrazol on floral
           formation, endogenous hormones, and flowering-associated genes in
           ‘Fuji’ apple (Malus domestica Borkh.)
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Songwen Zhang, Dong Zhang, Sheng Fan, Lisha Du, Yawen Shen, Libo Xing, Youmei Li, Juanjuan Ma, Mingyu Han
      Gibberellins (GAs) reduce apple (Malus domestica) flowering rates; however, the mechanism of their action is not fully understood. To gain a better insight into gibberellin-regulated flowering, here, 5 year-old ‘Fuji’ apple trees were used to explore the responses of hormones [GA1+3, GA4+7, indole-3-acetic acid (IAA), zeatin-riboside (ZR), and abscisic acid (ABA)], and gibberellin- and flowering-associated genes, to applications of gibberellin acid (GA3) and paclobutrazol (PAC). Results showed that GA3 relatively stimulated vegetative growth and delayed floral induction. Moreover, GA3 spraying significantly affected contents of all endogenous hormones and all the genes tested in at least one time points: the content of endogenous GAs was increased instantly and that of ZR was reduced at 44 days after fullbloom (DAF), which might constitute an unfavorable factor for flower formation; MdKO (ent-kaurene oxidase gene) and MdGA20ox (GA20 oxidase gene) were significantly repressed by a high level of GAs through the negative feedback regulation of GA; additionally, the MdSPLs (SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE) in this study were all significantly repressed by GA3 but promoted by PAC; the expression of MdFT1/2 (FLOWERING LOCUS T), MdSOC1 (SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1) and MdAP1 (APETALA1) in GA3-treated buds changed in the same way, and they were repressed at 44 DAF. We suppose that GA3 spraying disrupts the balance between ZR and GAs, and inhibits floral induction, probably by suppressing MdSPLs and the floral integrators in flower induction, which ultimately contributed to inhibiting flower formation.


      PubDate: 2016-06-15T09:03:18Z
       
  • Silver and titanium dioxide nanoparticle toxicity in plants: A review of
           current research
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Ashley Cox, P. Venkatachalam, Shivendra Sahi, Nilesh Sharma
      Nanoparticles (NPs) have become widely used in recent years for many manufacturing and medical processes. Recent literature suggests that many metallic nanomaterials including those of silver (Ag) and titanium dioxide (TiO2) cause significant toxic effects in animal cell culture and animal models, however, toxicity studies using plant species are limited. This review examines current progress in the understanding of the effect of silver and titanium dioxide nanoparticles on plant species. There are many facets to this ongoing environmental problem. This review addresses the effects of NPs on oxidative stress-related gene expression, genotoxicity, seed germination, and root elongation. It is largely accepted that NP exposure results in the cellular generation of reactive oxygen species (ROS), leading to both positive and negative effects on plant growth. However, factors such as NP size, shape, surface coating and concentration vary greatly among studies resulting in conflicting reports of the effect at times. In addition, plant species tend to differ in their reaction to NP exposure, with some showing positive effects of NP augmentation while many others showing detrimental effects. Seed germination studies have shown to be less effective in gauging phytotoxicity, while root elongation studies have shown more promise. Given the large increase in nanomaterial applications in consumer products, agriculture and energy sectors, it is critical to understand their role in the environment and their effects on plant life. A closer look at nanomaterial-driven ecotoxicity is needed. Ecosystem-level studies are required to indicate how these nanomaterials transfer at the critical trophic levels affecting human health and biota.


      PubDate: 2016-06-10T08:35:13Z
       
  • Genome-wide survey and expression analysis of the amino acid transporter
           superfamily in potato (Solanum tuberosum L.)
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Haoli Ma, Xiaoli Cao, Shandang Shi, Silu Li, Junpeng Gao, Yuling Ma, Qin Zhao, Qin Chen
      Amino acid transporters (AATs) are integral membrane proteins responsible for the transmembrane transport of amino acids and play important roles in various physiological processes of plants. However, there has not yet been a genome-wide overview of the StAAT gene family to date and only StAAP1 has been previously studied in potato. In this paper, a total of 72 StAATs were identified using a series of bioinformatics searches and classified into 12 subfamilies based on their phylogenetic relationship with known Arabidopsis and rice AATs. Chromosomal localization revealed their distribution on all 12 chromosomes. Nearly one-third of StAAT genes (23 of 72) were derived from gene duplication, among which tandem duplication made the greatest contribution to the expansion of the StAAT family. Motif analysis showed that the same subfamily had similar conserved motifs in both numbers and varieties. Moreover, high-throughput sequencing data was used to analyze the expression patterns of StAAT genes and was verified by quantitative real-time RT-PCR. The expression of StAAT genes exhibited both abundant and tissue-specific expression patterns, which might be connected to their functional roles in long- and short-distance transport. This study provided a comprehensive survey of the StAAT gene family, and could serve as a theoretical foundation for the further functional identification and utilization of family members.


      PubDate: 2016-06-10T08:35:13Z
       
  • Involvement of ABA- and H2O2-dependent cytosolic glucose-6-phosphate
           dehydrogenase in maintaining redox homeostasis in soybean roots under
           drought stress
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Huahua Wang, Lidan Yang, Yan Li, Junjie Hou, Junjun Huang, Weihong Liang
      The roles of abscisic acid (ABA) and hydrogen peroxide (H2O2) in inducing glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) activity and the possible roles of G6PDH in regulating ascorbate-glutathione (AsA-GSH) cycle were investigated in soybean (Glycine max L.) roots under drought stress. Drought caused a marked increase of the total and cytosolic G6PDH activities and triggered a rapid ABA and H2O2 accumulation in soybean roots. Exogenous ABA or H2O2 treatment elevated the total and cytosolic G6PDH activities, whereas suppressing ABA or H2O2 production inhibited the drought-induced increase in total and cytosolic G6PDH activities, suggesting that ABA and H2O2 are required for drought-induced increase of total G6PDH activity, namely cytosolic G6PDH activity. Furthermore, ABA induced H2O2 production by stimulating NADPH oxidase activity under drought stress. Moreover, drought significantly increased the contents of AsA and GSH and the activities of key enzymes in AsA-GSH cycle, while application of G6PDH inhibitor to seedlings significantly reduced the above effect induced by drought. Taken together, these results indicate that H2O2 acting as a downstream signaling molecule of ABA mediates drought-induced increase in cytosolic G6PDH activity, and that enhanced cytosolic G6PDH activity maintains cellular redox homeostasis by regulating AsA-GSH cycle in soybean roots.


      PubDate: 2016-06-10T08:35:13Z
       
  • Carbon allocation, osmotic adjustment, antioxidant capacity and growth in
           cotton under long-term soil drought during flowering and boll-forming
           period
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Rui Wang, Min Gao, Shu Ji, Shanshan Wang, Yali Meng, Zhiguo Zhou
      Responses of plant to drought largely depend on the intensity, duration and developmental stage at which water stress occurs. The purpose of this study was to analyze the dynamic of cotton physiology response to different levels sustained soil water deficit during reproductive growth stage at leaf basis. Three levels of steady-state water regimes [soil relative water content (SRWC) maintained at (75 ± 5)%, (60 ± 5)% and (45 ± 5)%] were imposed when the white flowers had opened on the first fruiting position of the 6–7th fruiting branches (FB6-7), which was the first day post anthesis (i.e. 1 DPA) and lasted to 50 DPA. Results showed decreasing SRWC slowed cotton growth on the base of biomass and leaf area. However, carbon metabolites levels were globally increased under drought despite of notably inhibited photosynthesis throughout the treatment period. Clear diurnal pattern of sucrose and starch concentrations was obtained and sucrose levels were evaluated while starch concentration was reduced with decreasing soil water content during a 24-h cycle. Osmotic adjustment (OA) was observed at most of the sampling dates throughout the drought period. K+ was the main contributor to osmotic adjustment (OA) at 10 and 24 DPA then turned out to be amino acid at 38 and 50 DPA. The stressed cotton gradually failed to scavenge reactive oxygen species (ROS) with increasing days post anthesis, primarily due to the permanent decrease in SOD activity. Elevated carbohydrates levels suggest cotton growth was more inhibited by other factors than carbon assimilation. OA and antioxidant could be important protective mechanisms against soil water deficit in this species, and transition of these mechanisms was observed with drought intensity and duration increased.


      PubDate: 2016-06-10T08:35:13Z
       
  • Lithium toxicity in plants: Reasons, mechanisms and remediation
           possibilities – A review
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Babar Shahzad, Mohsin Tanveer, Waseem Hassan, Adnan Noor Shah, Shakeel Ahmad Anjum, Sardar Alam Cheema, Iftikhar Ali
      Lithium (Li) is a naturally occurring element; however, it is one of the non-essential metals for life. Lithium is becoming a serious matter of discussion for the people who do research on trace metals and environmental toxicity in plants. Due to limited information available regarding its mobility from soil to plants, the adverse effects of Li toxicity to plants are still unclear. This article briefly discusses issues around Li, its role and its essentiality in plants and research directions that may assist in inter-disciplinary studies to evaluate the importance of Li’s toxicity. Further, potential remediation approaches will also be highlighted in this review. Briefly, Li influenced the growth of plants in both stimulation and reduction ways, depending on the concentration of Li in growth medium. On the negative side, Li reduces the plant growth by interrupting numerous physiological processes and altering metabolism in plant. The contamination of soil by Li is becoming a serious problem, which might be a threat for crop production in the near future. Additionally, lack of considerable information about the tolerance mechanisms of plants further intensifies the situation. Therefore, future research should emphasize in finding prominent and approachable solutions to minimize the entry of Li from its sources (especially from Li batteries) into the soil and food chain.
      Teaser Lithium (Li) not only reduces but also stimulates plant growth, depending on its concentration in growth medium. Li interferes with numerous physiological and metabolic processes to influence plant growth.

      PubDate: 2016-06-05T00:05:57Z
       
  • Analysis of the carbohydrate-binding-module from Fragaria x ananassa
           α-L-arabinofuranosidase 1
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): I.N. Sin, M.A. Perini, G.A. Martínez, P.M. Civello
      α-L-arabinofuranosidases (EC 3.2.1.55) are enzymes involved in the catabolism of several cell-wall polysaccharides such as pectins and hemicelluloses, catalyzing the hydrolysis of terminal non-reducing α-L-arabinofuranosil residues. Bioinformatic analysis of the aminoacidic sequences of Fragaria x ananassa α-L-arabinofuranosidases predict a putative carbohydrate-binding-module of the family CBM_4_9, associated to a wide range of carbohydrate affinities. In this study, we report the characterization of the binding affinity profile to different cell wall polysaccharides of the putative CBM of α–L-arabinofuranosidase 1 from Fragaria x ananassa (CBM-FaARA1). The sequence encoding for the putative CBM was cloned and expressed in Escherichia coli, and the resultant recombinant protein was purified from inclusion bodies by a Nickel affinity chromatography under denaturing conditions. The refolded recombinant protein was then subjected to binding assays and affinity gel electrophoresis, which indicated its ability to bind cellulose and also high affinity for homogalacturonans.


      PubDate: 2016-06-05T00:05:57Z
       
  • Combined herbicide and saline stress differentially modulates hormonal
           regulation and antioxidant defense system in Oryza sativa cultivars
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Faisal Islam, Basharat Ali, Jian Wang, Muhammad A. Farooq, Rafaqat A. Gill, Shafaqat Ali, Danying Wang, Weijun Zhou
      Plants are simultaneously exposed to a combination of biotic and abiotic stresses in field conditions. Crops respond to the combined stress in a unique way which cannot be understood by extrapolating the results of individual stress. In the present study, effects of individual and combined stress of herbicide (2,4-dichlorophenoxyacetic acid) and salinity (NaCl) on two Oryza sativa cultivars (ZJ 88 and XS 134) were investigated. Both herbicide and saline stress affected the plant growth differentially and produced oxidative stress in rice cultivars. Interestingly, the combination of herbicide and salinity showed a significant protection to both rice cultivars by reducing ROS (H2O2, O2 −) and lipid peroxidation through modulation of enzymatic (SOD, POD, CAT and APX) and non-enzymatic (TSP, sugars, phenolic and proline) antioxidants. In addition, active regulation of transcript levels of genes encoding Na+ and K+ (OsHKT1;5, OsLti6a,b, OsHKT2;1, OsSOS1, OsCNGC1, OsNHX1 and OsAKT1) transporter proteins reduced sodium and enhanced potassium accumulation under combined stress, resulted a better growth and ionic homeostasis in both rice cultivars. The production of ABA and IAA was significantly higher in cultivar XS 134 compared to cultivar ZJ 88 under control conditions. However, combined herbicide and saline stress enhanced the accumulation of phytohormones (IAA and ABA) and transcription of ethylene in cultivar ZJ 88, which might be one of the factors responsible for poor salt tolerance in sensitive cultivar. These findings indicated that herbicide application under saline stress confers tolerance to salinity in rice cultivars, likely by reducing oxidative damage, modulating mineral absorption, upgradation of antioxidant defense and by dynamic regulation of key genes involved in Na+ and K+ homeostasis in plants.


      PubDate: 2016-06-05T00:05:57Z
       
  • Photosynthetic adaptation strategy of Ulva prolifera floating on the sea
           surface to environmental changes
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Xinyu Zhao, Xuexi Tang, Huanxin Zhang, Tongfei Qu, Ying Wang
      For 8 consecutive years, a green tide has originated in the southern Yellow Sea and spread to the Qingdao offshore area. The causative species, Ulva prolifera, always forms a very thick thallus mat that is capable of drifting long distances over long periods. During this process, although the thalli face disturbance by complex environmental factors, they maintain high biomass and proliferation. We hypothesized that some form of photosynthetic adaptation strategy must exist to protect the thalli. Therefore, we studied the different photosynthetic response characteristics of the surface and lower layers of the floating thallus mats, and investigated the physiological and molecular-level adaptation mechanisms. The results showed that: (1) U. prolifera has strong photosynthetic capability that ensures it can gain sufficient energy to increase its biomass and adapt to long-distance migration. (2) Surface layer thalli adapt to the complex environment by dissipating excess energy via photosynthetic quantum control (energy quenching and energy redistribution between PSII/PSI) to avoid irreversible damage to the photosynthetic system. (3) Lower layer thalli increase their contents of Chlorophyll a (Chl a) and Chlorophyll b (Chl b) and decrease their Chl a/Chl b ratio to improve their ability to use light energy. (4) U. prolifera has strong photosynthetic plasticity and can adapt to frequent exchange between the surface and lower layer environments because of wave disturbance. Pigment component changes, energy quenching, and energy redistribution between PSII/PSI contribute to this photosynthetic plasticity.


      PubDate: 2016-06-05T00:05:57Z
       
  • The role of photorespiration during astaxanthin accumulation in
           Haematococcus pluvialis (Chlorophyceae)
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Chunhui Zhang, Litao Zhang, Jianguo Liu
      Most previous studies on Haematococcus pluvialis have been focused on growth and astaxanthin accumulation. However, the relationships between photorespiration and astaxanthin accumulation have not been clarified. The purpose of this study was to examine the role of photorespiration during the process of astaxanthin accumulation in H. pluvialis. During astaxanthin accumulation, the astaxanthin content was reduced significantly when photorespiration was inhibited by its specific inhibitor, carboxymethoxylamine. The inhibition of photorespiration did not change the dry weight, chlorophyll content and OJIP transients during the incubation; however, the inhibition of photorespiration significantly decreased the photochemistry of photosystem II and total photosynthetic O2 evolution capacity. Moreover, the restriction in photorespiration was synchronized with a decrease of astaxanthin accumulation. These results suggest that the photorespiratory pathway in H. pluvialis can accelerate astaxanthin accumulation. We speculate that photorespiration can enhance astaxanthin accumulation in the following ways: (i) photorespiration directly affects the glycerate-3-phosphate (PGA) level, which is intrinsically related to the accumulation of astaxanthin in H. pluvialis; (ii) the photorespiratory pathway indirectly affects the PGA level by effecting the dark reactions of photosynthesis, which then results in the enhancement of astaxanthin accumulation in H. pluvialis.


      PubDate: 2016-06-05T00:05:57Z
       
  • Identification of differentially expressed genes and signalling pathways
           in bark of Hevea brasiliensis seedlings associated with secondary
           laticifer differentiation using gene expression microarray
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Swee Cheng Loh, Gincy P. Thottathil, Ahmad Sofiman Othman
      The natural rubber of Para rubber tree, Hevea brasiliensis, is the main crop involved in industrial rubber production due to its superior quality. The Hevea bark is commercially exploited to obtain latex, which is produced from the articulated secondary laticifer. The laticifer is well defined in the aspect of morphology; however, only some genes associated with its development have been reported. We successfully induced secondary laticifer in the jasmonic acid (JA)-treated and linolenic acid (LA)-treated Hevea bark but secondary laticifer is not observed in the ethephon (ET)-treated and untreated Hevea bark. In this study, we analysed 27,195 gene models using NimbleGen microarrays based on the Hevea draft genome. 491 filtered differentially expressed (FDE) transcripts that are common to both JA- and LA-treated bark samples but not ET-treated bark samples were identified. In the Eukaryotic Orthologous Group (KOG) analysis, 491 FDE transcripts belong to different functional categories that reflect the diverse processes and pathways involved in laticifer differentiation. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) and KOG analysis, the profile of the FDE transcripts suggest that JA- and LA-treated bark samples have a sufficient molecular basis for secondary laticifer differentiation, especially regarding secondary metabolites metabolism. FDE genes in this category are from the cytochrome (CYP) P450 family, ATP-binding cassette (ABC) transporter family, short-chain dehydrogenase/reductase (SDR) family, or cinnamyl alcohol dehydrogenase (CAD) family. The data includes many genes involved in cell division, cell wall synthesis, and cell differentiation. The most abundant transcript in FDE list was SDR65C, reflecting its importance in laticifer differentiation. Using the Basic Local Alignment Search Tool (BLAST) as part of annotation and functional prediction, several characterised as well as uncharacterized transcription factors and genes were found in the dataset. Hence, the further characterization of these genes is necessary to unveil their role in laticifer differentiation. This study provides a platform for the further characterization and identification of the key genes involved in secondary laticifer differentiation.


      PubDate: 2016-05-31T00:00:17Z
       
  • Unsaturated amino acids derived from isoleucine trigger early membrane
           effects on plant cells
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Gabriel Roblin, Joëlle Laduranty, Janine Bonmort, Mohand Aidene, Jean-François Chollet
      Unsaturated amino acids (UnsAA) have been shown to affect the activity of various biological processes. However, their mode of action has been investigated poorly thus far. We show in this work that 2-amino-3-methyl-4-pentenoic acid (C2) and 2-amino-3-methyl-4-pentynoic acid (C3) structurally derived from isoleucine (Ile) exhibited a multisite action on plant cells. For one, C2 and C3 induced early modifications at the plasma membrane level, as shown by the hyperpolarization monitored by microelectrode implantation in the pulvinar cells of Mimosa pudica, indicating that these compounds are able to modify ionic fluxes. In particular, proton (H+) fluxes were modified, as shown by the pH rise monitored in the bathing medium of pulvinar tissues. A component of this effect may be linked to the inhibitory effect observed on the proton pumping and the vanadate-sensitive activity of the plasma membrane H+-ATPase monitored in plasma membrane vesicles (PMVs) purified from pulvinar tissues of M. pudica and leaf tissues of Beta vulgaris. This effect may explain, in part, the inhibitory effect of the compounds on the uptake capacity of sucrose and valine by B. vulgaris leaf tissues. In contrast, an unexpected action was observed in cell reactions, implicating ion fluxes and water movement. Indeed, the osmocontractile reactions of pulvini induced either by a mechanical shock in M. pudica or by dark and light signals in Cassia fasciculata were increased, indicating that, compared to Ile, these compounds may modify in a specific way the plasma membrane permeability to water and ions.


      PubDate: 2016-05-31T00:00:17Z
       
  • Response of phytohormones and correlation of SAR signal pathway genes to
           the different resistance levels of grapevine against Plasmopara viticola
           infection
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Shao-li Liu, Jiao Wu, Pei Zhang, Gerile Hasi, Yu Huang, Jiang Lu, Ya-li Zhang
      Phytohormones play an important role in the process of disease resistance in plants. Here, we investigated which among salicylic acid, jasmonic acid, and abscisic acid performs a key role in plant defense after Plasmopara viticola infection in grapevine. We used grapevines possessing different resistance levels against P. viticola infection to study the relationship between the expression of key genes in the related resistance signaling pathways and the level of resistance. We performed high-performance liquid chromatography–mass spectrometry to estimate the phytohormone contents in grape leaves at different time points after the infection. Furthermore, we performed quantitative analyses of key genes such as EDS1, PAD4, ICS2, PAL, NPR1, TGA1, and PR1 in the systemic acquired resistance pathway by quantitative reverse transcription-polymerase chain reaction. The results showed an increased variation in the SA content, which was maintained at high levels, after P. viticola infection in plant species exhibiting stronger resistance to the pathogen; this finding highlights the importance of SA in plant defense mechanisms. Moreover, EDS1 and PAD4 expression did not show a positive correlation with disease resistance in grape; however, higher expression of other genes that were analyzed was observed in highly resistant grape varieties. Our results provide insights into the role of phytohormone regulation in the induction and maintenance of plant defense response to pathogens.


      PubDate: 2016-05-31T00:00:17Z
       
  • Metabolic variations in different citrus rootstock cultivars associated
           with different responses to Huanglongbing
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Ute Albrecht, Oliver Fiehn, Kim D. Bowman
      Huanglongbing (HLB) is one of the most destructive bacterial diseases of citrus. No resistant cultivars have been identified, although tolerance has been observed in the genus Poncirus and some of its hybrids with Citrus that are commonly used as rootstocks. In this study we exploited this tolerance by comparing five different tolerant hybrids with a cultivar that shows pronounced HLB sensitivity to discern potential contributing metabolic factors. Whole leaves of infected and non-infected greenhouse-grown seedlings were extracted and subjected to untargeted GC-TOF MS based metabolomics. After BinBase data filtering, 342 (experiment 1) and 650 (experiment 2) unique metabolites were quantified, of which 122 and 195, respectively, were assigned by chemical structures. The number of metabolites found to be differently regulated in the infected state compared with the non-infected state varied between the cultivars and was largest (166) in the susceptible cultivar Cleopatra mandarin (Citrus reticulata) and lowest (3) in the tolerant cultivars US-897 (C. reticulata ‘Cleopatra’ × Poncirus trifoliata) and US-942 (C. reticulata ‘Sunki’ × P. trifoliata) from experiment 2. Tolerance to HLB did not appear to be associated with accumulation of higher amounts of protective metabolites in response to infection. Many metabolites were found in higher concentrations in the tolerant cultivars compared with susceptible Cleopatra mandarin and may play important roles in conferring tolerance to HLB. Lower availability of specific sugars necessary for survival of the pathogen may also be a contributing factor in the decreased disease severity observed for these cultivars.


      PubDate: 2016-05-31T00:00:17Z
       
  • Phenotyping two tomato genotypes with different nitrogen use efficiency
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Maria Rosa Abenavoli, Caterina Longo, Antonio Lupini, Anthony J. Miller, Fabrizio Araniti, Francesco Mercati, Maria P. Princi, Francesco Sunseri
      Nitrogen (N) supply usually limits crop production and optimizing N-use efficiency (NUE) to minimize fertilizer loss is important. NUE is a complex trait that can be dissected into crop N uptake from the soil (NUpE) and N utilization (NUtE). We compared NUE in 14 genotypes of three week old tomatoes grown in sand or hydroponic culture supplied with nitrate (NO3 −). Culture method influenced measured NUE for some cultivars, but Regina Ostuni (RO) and UC82 were consistently identified as high and low NUE genotypes. To identify why these genotypes had contrasting NUE some traits were compared growing under 0.1 and 5 mM NO3 − supply. UC82 showed greater root 15NO3 − influx at low and high supply, and stronger SlNRT2.1/NAR2.1 transporter expression under low supply when compared with RO. Conversely, RO showed a higher total root length and thickness compared to UC82. Compared with UC82, RO showed higher shoot SlNRT2.3 expression and NO3 − storage at high supply, but similar NO3 − reductase activity. After N-starvation, root cell electrical potentials of RO were significantly more negative than UC82, but nitrate elicited similar responses in both root types. Overall for UC82 and RO, NUtE may play a greater role than NUpE for improved NUE.


      PubDate: 2016-05-26T11:33:53Z
       
  • Regulation of biosynthesis and emission of volatile
           phenylpropanoids/benzenoids in petunia× hybrida flowers by
           multi-factors of circadian clock, light, and temperature
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Sihua Cheng, Xiumin Fu, Xin Mei, Ying Zhou, Bing Du, Naoharu Watanabe, Ziyin Yang
      Floral volatile phenylpropanoids and benzenoids (VPBs) play important ecological functions and have potential economic applications. Little is known about how multi-factors in integration regulate the formation and emission of floral VPBs. In the present study, we investigated effects of multi factors including endogenous circadian clock, light, and temperature on the formation and emission of VPBs, which are major volatiles in flowers of Petunia× hybrida cv. ‘Mitchell Diploid’. Endogenous circadian clock was proposed as the most important factor regulating rhythmic emission of VPBs and expressions of structural genes involved in the upstream biosynthetic pathway of VPBs, but did not affect expression levels of structural genes involved in the downstream pathway and VPBs-related regulators. In contrast to light, temperature was a more constant factor affecting emission of VPBs. VPBs emission could be inhibited within a short time by increasing temperature. The information will contribute to our understanding of emission mechanism of floral volatiles.
      Graphical abstract image

      PubDate: 2016-05-26T11:33:53Z
       
  • Cloning and biochemical characterization of indole-3-acetic acid-amino
           acid synthetase PsGH3 from pea
    • Abstract: Publication date: October 2016
      Source:Plant Physiology and Biochemistry, Volume 107
      Author(s): Maciej Ostrowski, Agnieszka Mierek-Adamska, Dorota Porowińska, Anna Goc, Anna Jakubowska
      Phytohormone conjugation is one of the mechanisms that maintains a proper hormonal homeostasis and that is necessary for the realization of physiological responses. Gretchen Hagen 3 (GH3) acyl acid amido synthetases convert indole-3-acetic acid (IAA) to IAA-amino acid conjugates by ATP-dependent reactions. IAA-aspartate (IAA-Asp) exists as a predominant amide conjugate of auxin in pea tissues and acts as an intermediate during IAA catabolism. Here we report a novel recombinant indole-3-acetic acid-amido synthetase in Pisum sativum. In silico analysis shows that amino acid sequence of PsGH3 has the highest homology to Medicago truncatula GH3.3. The recombinant His-tag-PsGH3 fusion protein has been obtained in E. coli cells and is a soluble monomeric polypeptide with molecular mass of 69.18 kDa. The PsGH3 was purified using Ni2+-affinity chromatography and native PAGE. Kinetic analysis indicates that the enzyme strongly prefers IAA and L-aspartate as substrates for conjugation revealing K m ATP  = 0.49 mM, K m L−Asp  = 2.2 mM, and K m IAA  = 0.28 mM. Diadenosine pentaphosphate (Ap5A) competes with ATP for catalytic site and diminishes the PsGH3 affinity toward ATP approximately 1.11-fold indicating K i  = 8.5 μM. L-Tryptophan acts as an inhibitor of IAA-amido synthesizing activity by competition with L-aspartate. Inorganic pyrophosphatase (PPase) hydrolyzing pyrophosphate to two phosphate ions, potentiates IAA-Asp synthetase activity of PsGH3. Our results demonstrate that PsGH3 is a novel enzyme that is involved in auxin metabolism in pea seeds.


      PubDate: 2016-05-26T11:33:53Z
       
 
 
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