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Plant Physiology and Biochemistry    [11 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0981-9428
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.996]   [H-I: 63]
  • RING-type ubiquitin ligase McCPN1 catalyzes UBC8-dependent protein
           ubiquitination and interacts with Argonaute 4 in halophyte ice plant
    • Abstract: Publication date: Available online 18 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Chang-Hua Li , Chih-Pin Chiang , Jun-Yi Yang , Chia-Jou Ma , Yu-Chan Chen , Hungchen Emilie Yen
      RING-type copines are a small family of plant-specific RING-type ubiquitin ligases. They contain an N-terminal myristoylation site for membrane anchoring, a central copine domain for substrate recognition, and a C-terminal RING domain for E2 docking. RING-type copine McCPN1 (copine1) from halophyte ice plant (Mesembryanthemum crystallinum L.) was previously identified from a salt-induced cDNA library. In this work, we characterize the activity, expression, and localization of McCPN1 in ice plant. An in vitro ubiquitination assay of McCPN1 was performed using two ice plant UBCs, McUBC1 and McUBC2, characterized from the same salt-induced cDNA library. The results showed that McUBC2, a member of the UBC8 family, stimulated the autoubiquitination activity of McCPN1, while McUBC1, a homolog of the UBC35 family, did not. The results indicate that McCPN1 has selective E2-dependent E3 ligase activity. We found that McCPN1 localizes primarily on the plasma membrane and in the nucleus of plant cells. Under salt stress, the accumulation of McCPN1 in the roots increases. A yeast two-hybrid screen was used to search for potential McCPN1-interacting partners using a library constructed from salt-stressed ice plants. Screening with full-length McCPN1 identified several independent clones containing partial Argonaute 4 (AGO4) sequence. Subsequent agro-infiltration, protoplast two-hybrid analysis, and bimolecular fluorescence complementation assay confirmed that McCPN1 and AGO4 interacted in vivo in the nucleus of plant cells. The possible involvement of a catalyzed degradation of AGO4 by McCPN1 in response to salt stress is discussed.


      PubDate: 2014-04-20T12:37:38Z
       
  • Identification of nutrient deficiency in maize and tomato plants by
           in vivo chlorophyll a fluorescence measurements
    • Abstract: Publication date: Available online 16 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Hazem Kalaji , Abdallah Oukarroum , Vladimir Alexandrov , Margarita Kouzmanova , Marian Brestic , Marek Zivcak , Izabela A. Samborska , Magdalena D. Cetner , Suleyman I. Allakhverdiev , Vasilij Goltsev
      The impact of some macro (Ca, S, Mg, K, N, P) and micro (Fe) nutrients deficiency on the functioning of the photosynthetic machinery in tomato (Solanum lycopersicum L.) and maize (Zea mays L.) plants grown in hydroponic cultures were investigated. Plants grown on a complete nutrient solution (control) were compared with those grown in a medium, which lacked one of macro- or microelements. The physiological state of the photosynthetic machinery in vivo was analysed after 14-days of deficient condition by the parameters of JIP-test based on fast chlorophyll a fluorescence records. In most of the nutrient-deficient samples, the decrease of photochemical efficiency, increase in non-photochemical dissipation and decrease of the number of active photosystem II (PSII) reaction centres were observed. However, lack of individual nutrients also had nutrient-specific effects on the photochemical processes. In Mg and Ca-deficient plants, the most severe decrease in electron donation by oxygen evolving complex (OEC) was indicated. Sulphur deficiency caused limitation of electron transport beyond PSI, probably due to decrease in the PSI content or activity of PSI electron acceptors; in contrary, Ca deficiency had an opposite effect, where the PSII activity was affected much more than PSI. Despite the fact that clear differences in nutrient deficiency responses between tomato and maize plants were observed, our results indicate that some of presented fluorescence parameters could be used as fluorescence phenotype markers. The principal component analysis of selected JIP-test parameters was presented as a possible species-specific approach to identify/predict the nutrient deficiency using the fast chlorophyll fluorescence records.
      Graphical abstract image

      PubDate: 2014-04-20T12:37:38Z
       
  • ΔpH-dependent non-photochemical quenching (qE) of excited
           chlorophylls in the Photosystem II core complex of the freshwater
           cyanobacterium Synechococcus sp PCC 7942
    • Abstract: Publication date: Available online 18 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Kostas Stamatakis , George C. Papageorgiou
      Light–induced and lumen acidity-dependent quenching (qE) of excited chlorophylls (Chl) in vivo has been amply documented in plants and algae, but not in cyanobacteria, using primarily the saturation pulse method of quenching analysis which is applied to continuously illuminated samples. This method is unsuitable for cyanobacteria because the background illumination elicits in them a very large Chl a fluorescence signal, due to a state 2 to state 1 transition, which masks fluorescence changes due to other causes. We investigated the qE problem in the cyanobacterium Synechococcus sp. PCC 7942 using a kinetic method (Chl a fluorescence induction) with which qE can be examined before the onset of the state 2 to state 1 transition and the attendant rise of Chl a fluorescence. Our results confirm the existence of a qE mechanism that operates on excited Chls a in Photosystem II core complexes of cyanobacteria.


      PubDate: 2014-04-20T12:37:38Z
       
  • Conservation of Arabidopsis thaliana circadian clock genes in
           Chrysanthemum lavandulifolium
    • Abstract: Publication date: Available online 18 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Jianxin Fu , Liwen Yang , Silan Dai
      In Arabidopsis, circadian clock genes play important roles in photoperiod pathway by regulating the daytime expression of CONSTANS (CO), but related reports for chrysanthemum are notably limited. In this study, we isolated eleven circadian clock genes, which lie in the three interconnected negative and positive feedback loops in a wild diploid chrysanthemum, Chrysanthemum lavandulifolium. With the exception of ClELF3, ClPRR1 and ClPRR73, most of the circadian clock genes are expressed more highly in leaves than in other tested tissues. The diurnal rhythms of these circadian clock genes are similar to those of their homologs in Arabidopsis. ClELF3 and ClZTL are constitutively expressed at all time points in both assessed photoperiods. The expression succession from morning to night of the PSEUDO RESPONSE REGULATOR (PRR) gene family occurs in the order ClPRR73/ClPRR37, ClPRR5, and then ClPRR1. ClLHY is expressed during the dawn period, and ClGIs is expressed during the dusk period. The peak expression levels of ClFKF1 and ClGIs are synchronous in the inductive photoperiod. However, in the non-inductive night break (NB) condition or non-24 h photoperiod, the peak expression level of ClFKF1 is significantly changed, indicating that ClFKF1 itself or the synchronous expression of ClFKF1 and ClGIs might be essential to initiate the flowering of C. lavandulifolium. This study provides the first extensive evaluation of circadian clock genes, and it presents a useful foundation for dissecting the functions of circadian clock genes in C. lavandulifolium.


      PubDate: 2014-04-20T12:37:38Z
       
  • Amelioration of high salinity stress damage by plant growth-promoting
           bacterial endophytes that contain ACC deaminase
    • Abstract: Publication date: Available online 18 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Shimaila Ali , Trevor C. Charles , Bernard R. Glick
      Plant growth and productivity is negatively affected by soil salinity. However, it is predicted that plant growth-promoting bacterial (PGPB) endophytes that contain 1-aminocyclopropane-1-carboxylate (ACC) deaminase (E.C. 4.1.99.4) can facilitate plant growth and development in the presence of a number of different stresses. In present study, the ability of ACC deaminase containing PGPB endophytes Pseudomonas fluorescens YsS6, Pseudomonas migulae 8R6, and their ACC deaminase deficient mutants to promote tomato plant growth in the absence of salt and under two different levels of salt stress (165 mM and 185 mM) was assessed. It was evidence that wild-type bacterial endophytes (P. fluorescens YsS6 and P. migulae 8R6) promoted tomato plant growth significantly even in the absence of stress (salinity). Plants pretreated with wild-type ACC deaminase containing endophytic strains were healthier and grew to a much larger size under high salinity stress compared to plants pretreated with the ACC deaminase deficient mutants or no bacterial treatment (control). The plants pretreated with ACC deaminase containing bacterial endophytes exhibit higher fresh and dry biomass, higher chlorophyll contents, and a greater number of flowers and buds than the other treatments. Since the only difference between wild-type and mutant bacterial endophytes was ACC deaminase activity, it is concluded that this enzyme is directly responsible for the different behavior of tomato plants in response to salt stress. The use of PGPB endophytes with ACC deaminase activity has the potential to facilitate plant growth on land that is not normally suitable for the majority of crops due to their high salt contents.


      PubDate: 2014-04-20T12:37:38Z
       
  • MicroRNAs involving in cold, wounding and salt stresses in Triticum
           aestivum L.
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Bing Wang , Yan-fei Sun , Na Song , Jin-ping Wei , Xiao-jie Wang , Hao Feng , Zhi-yuan Yin , Zhen-sheng Kang
      MicroRNAs (miRNAs) play critical roles in post-transcriptional regulation and act as important endogenous regulators to various stresses. Cold, wounding and high-salinity are three common environmental stress stimuli influencing crops growth and development. In this study, we identified 31 known miRNAs and 3 novel miRNAs in wheat. Moreover, 19 stress-regulated miRNAs using RT-qPCR data in which the effects of three stresses were surveyed from the known miRNAs. Among them, 16, 12 and 8 miRNAs were regulated under cold, wounding and high-salinity treatments, respectively. Of which 4 miRNAs were highly responsive to cold stress in wheat by northern blot, and 6 wounding-regulated and 3 high-salinity-regulated miRNAs were detected. Meanwhile, miR159, miR393 and miR398 were responsive to multiple stress stimuli. Besides, 2 novel miRNAs were regulated by cold stress. While, the analyses of targets suggested miR159, miR398 and miR6001 could responses to stress conditions in regulation pathways. Taken together, the results of this study suggest that wheat miRNAs may play important roles in response to abiotic stress.


      PubDate: 2014-04-20T12:37:38Z
       
  • Isolation and characterization of Korean pine (Pinus koraiensis)
           convicilin
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Tengchuan Jin , Yang Wang , Yu-Wei Chen , Silvia M. Albillos , Mahendra H. Kothary , Tong-Jen Fu , Boyce Tankersley , Tara H. McHugh , Yu-Zhu Zhang
      A vicilin-like globulin seed storage protein, termed convicilin, was isolated for the first time from Korean pine (Pinus koraiensis). SDS-PAGE analysis revealed that Korean pine convicilin was post-translationally processed. The N-terminal peptide sequences of its components were determined. These peptides could be mapped to a protein translated from an embryo abundant transcript isolated in this study. Similar to vicilin, native convicilin appeared to be homotrimeric. Differential scanning calorimetry (DSC) analyses revealed that this protein is less resistant to thermal treatment than Korean pine vicilin. Its transition temperature was 75.57 °C compared with 84.13 °C for vicilin. The urea induced folding-unfolding equilibrium of pine convicilin monitored by intrinsic fluorescence could be interpreted in terms of a two-state model, with a C m of 4.41 ± 0.15 M.
      Graphical abstract image

      PubDate: 2014-04-20T12:37:38Z
       
  • NADPH-dependent thioredoxin reductase A (NTRA) confers elevated tolerance
           to oxidative stress and drought
    • Abstract: Publication date: Available online 19 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Joon-Yung Cha , Joo Yeon Kim , In Jung Jung , Mi Ri Kim , Andrew Melencion , Sadia Sabrina Alam , Dae-Jin Yun , Sang Yeol Lee , Min Gab Kim , Woe-Yeon Kim
      NADPH-dependent thioredoxin reductases (NTRs) are key-regulatory enzymes determining the redox state of the thioredoxin (Trx) system that provides reducing power to peroxidases or oxidoreductases. Moreover, it also plays an essential function in the direct reduction of ROS and acquiring stress tolerance in plant. Cytoplasmic NTRA, mitochondrial NTRB, and chloroplastic NTRC are the three conserved NTRs which cooperate with specific sub-cellularly localized Trxs in Arabidopsis. However, cytosolic NTRs such as NTRA in Arabidopsis have not previously been identified in plants or mammals as a source of functional redundancy with mitochondrial NTRs. Here, we show the involvement of NTRA in the plant stress response counteracting oxidative and drought stresses. Methyl viologen (MV), an inducer of oxidative stress in plants, enhanced the NTRA transcripts. To identify the physiological role of NTRA influencing ROS homeostasis by stress, NTRA overexpression (NTRAOX) and knock-out mutants (ntra-ko) were generated. After exposure to oxidative stress, wild-type and ntra-ko plants were sensitive, but NTRAOX plants tolerant. ROS range was increased by MV in wild-type and ntra-ko plants, but not in NTRAOX. Investigating the involvement of Arabidopsis NTRA in drought, NTRAOX plants exhibited extreme drought tolerance with high survival rates, lower water loss and reduced ROS compared to wild-type and ntra-ko plants. Transcripts of drought-responsive genes, such as RD29A and DREB2A, were highly expressed under drought and antioxidant genes, namely CuZnSOD and APX1 were enhanced in the absence of drought in NTRAOX plants. The results suggest that NTRA overexpression confers oxidative and drought tolerance by regulation of ROS amounts.


      PubDate: 2014-04-20T12:37:38Z
       
  • Expression of peanut Iron Regulated Transporter 1 in tobacco and rice
           plants confers improved iron nutrition
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Hongchun Xiong , Xiaotong Guo , Takanori Kobayashi , Yusuke Kakei , Hiromi Nakanishi , Tomoko Nozoye , Lixia Zhang , Hongyun Shen , Wei Qiu , Naoko K. Nishizawa , Yuanmei Zuo
      Iron (Fe) limitation is a widespread agricultural problem in calcareous soils and severely limits crop production. Iron Regulated Transporter 1 (IRT1) is a key component for Fe uptake from the soil in dicot plants. In this study, the peanut (Arachis hypogaea L.) AhIRT1 was introduced into tobacco and rice plants using an Fe-deficiency-inducible artificial promoter. Induced expression of AhIRT1 in tobacco plants resulted in accumulation of Fe in young leaves under Fe deficient conditions. Even under Fe-excess conditions, the Fe concentration was also markedly enhanced, suggesting that the Fe status did not affect the uptake and translocation of Fe by AhIRT1 in the transgenic plants. Most importantly, the transgenic tobacco plants showed improved tolerance to Fe limitation in culture in two types of calcareous soils. Additionally, the induced expression of AhIRT1 in rice plants also resulted in high tolerance to low Fe availability in calcareous soils.


      PubDate: 2014-04-20T12:37:38Z
       
  • Bcl-2 suppresses activation of VPEs by inhibiting cytosolic Ca2+ level
           with elevated K+ efflux in NaCl-induced PCD in rice
    • Abstract: Publication date: Available online 16 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Yongho Kim , Mingqiang Wang , Yu Bai , Zhanghui Zeng , Fu Guo , Ning Han , Hongwu Bian , Junhui Wang , Jianwei Pan , Muyuan Zhu
      Bcl-2 is one of the most important antiapoptotic members in mammals and prevents many forms of apoptosis in a variety of cell types. Our previous study revealed that overexpression of Bcl-2 significantly suppressed H2O2/NaCl-induced programmed cell death via inhibiting the transcriptional activation of OsVPE2 and OsVPE3 in transgenic rice. However, Ca2+ and K+ homeostasis of this process remains largely unknown. In the present study, we investigate whether nonselective cation channels (NSCC) blockers affect Bcl-2 function in rice under salt stress and how Bcl-2 affects ion homeostasis in salt stress-induced PCD. The results showed that overexpression of Bcl-2 significantly decreased transient elevations in the cytosolic Ca2+ levels, inhibited NaCl-induced K+ efflux but not H+ efflux across the plasma membrane, and further suppressed the expression levels of OsVPE2 and OsVPE3, leading to the inhibition of salt-induced PCD and increase of tolerance to salt stress in transgenic rice. During the NaCl-induced PCD, the effects of a NSCC blocker La3+ on ion homeostasis and VPEs expression in wild-type were similar to the effects of Bcl-2 overexpression in transgenic line. However, a synergistic effect of Bcl-2 and La3+ was not obviously detectable. Our results suggested that Bcl-2 played an important role in suppression of NaCl-induced PCD by disruption of ion homeostasis, providing an insight into the mechanistic study of plant VPEs, cytosolic Ca2+ level and K+ efflux.


      PubDate: 2014-04-20T12:37:38Z
       
  • Editorial Board
    • Abstract: Publication date: June 2014
      Source:Plant Physiology and Biochemistry, Volume 79




      PubDate: 2014-04-15T20:27:48Z
       
  • The nodule conductance to O2 diffusion increases with phytase activity in
           N2-fixing Phaseolus vulgaris L
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Mohamed Lazali , Jean Jacques Drevon
      To understand the relationship between phosphorus use efficiency (PUE) and respiration for symbiotic nitrogen fixation (SNF) in legume nodules, six recombinant inbred lines of common bean (RIL Phaseolus vulgaris L.), contrasting in PUE for SNF, were inoculated with Rhizobium tropici CIAT899, and grown under hydroaeroponic culture with sufficient versus deficient P supply (250 versus 75 μmol P plant−1 week−1). At the flowering stage, the biomass of plants and phytase activity in nodules were analyzed after measuring O2 uptake by nodulated roots. Our results show that the P-deficiency significantly increased the phytase activity in nodules of all RILs though with highest extent for RILs 147, 29 and 83 (ca 45%). This increase in phytase activity was associated with an increase in nodule respiration (ca 22%) and in use of the rhizobial symbiosis (ca 21%). A significant correlation was found under P-deficiency between nodule O2 permeability and phytase activity in nodules for RILs 104, 34 and 115. This observation is to our knowledge the first description of a correlation between O2 permeability and phytase activity of a legume nodule. It is concluded that the variation of phytase activity in nodules can increase the internal utilization of P and might be involved in the regulation of nodule permeability for the respiration linked with SNF and the adaptation to P-deficiency.


      PubDate: 2014-04-15T20:27:48Z
       
  • Expression of flavonoid biosynthesis genes and accumulation of flavonoid
           in wheat leaves in response to drought stress
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Dongyun Ma , Dexiang Sun , Chenyang Wang , Yaoguang Li , Tiancai Guo
      Flavonoids are the low molecular weight polyphenolic secondary metabolic compounds, and have various functions in growth, development, reproduction, and stress defense. However, little is known about the roles of the key enzymes in the flavonoids biosynthesis pathway in response to drought stress in winter wheat. Here, we investigated the expression pattern of flavonoids biosynthesis genes and accumulation of flavonoids in wheat leaves under drought stress. Quantitative real-time PCR analysis showed that there were a rapid increase in expression levels of TaCHS, TaCHI, TaF3H, TaFNS, TaFLS, TaDFR, and TaANS under drought stress in two wheat cultivars Aikang 58 (AK) and Chinese Spring (CS). The cultivar CS exhibited higher genes expression levels of TaCHS, TaCHI, TaF3H, TaFLS, TaDFR, and TaANS, and the cultivar AK showed a higher expression level of TaFNS gene during drought treatment. The increase rates of genes expression were superior in AK compared to CS. Total phenolics content, total flavonoids content, anthocyanin content, and schaftoside content in wheat leaves were enhanced during drought treatment and cultivar CS had a relative higher accumulation. These results suggest that the flavonoids pathway genes expression and accumulation of flavonoids compounds may be closely related to drought tolerant in wheat. Further, flavonoids response mechanism may be different between wheat cultivars.


      PubDate: 2014-04-15T20:27:48Z
       
  • Effects of exogenous 24-epibrassinolide on the photosynthetic membranes
           under non-stress conditions
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Anelia G. Dobrikova , Radka S. Vladkova , Georgi D. Rashkov , Svetla J. Todinova , Sashka B. Krumova , Emilia L. Apostolova
      In the present work the effects of exogenous 24-epibrassinolide (EBR) on functional and structural characteristics of the thylakoid membranes under non-stress conditions were evaluated 48 h after spraying of pea plants with different concentrations of EBR (0.01, 0.1 and 1.0 mg.L−1). The results show that the application of 0.1 mg.L−1 EBR has the most pronounced effect on the studied characteristics of the photosynthetic membranes. The observed changes in 540 nm light scattering and in the calorimetric transitions suggest alterations in the structural organization of the thylakoid membranes after EBR treatment, which in turn influence the kinetics of oxygen evolution, accelerate the electron transport rate, increase the effective quantum yield of photosystem II and the photochemical quenching. The EBR-induced changes in the photosynthetic membranes are most probably involved in the stress tolerance of plants.


      PubDate: 2014-04-15T20:27:48Z
       
  • Alleviation of salt-induced photosynthesis and growth inhibition by
           salicylic acid involves glycinebetaine and ethylene in mungbean (Vigna
           radiata L.)
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): M. Iqbal R. Khan , M. Asgher , Nafees A. Khan
      The influence of salicylic acid (SA) in alleviation of salt stress in mungbean (Vigna radiata L.) through modulation of glycinebetaine (GB) and ethylene was studied. SA application at 0.5 mM increased methionine (Met) and GB accumulation in plants concomitant with the suppression of ethylene formation by inhibiting 1-aminocyclopropane carboxylic acid synthase (ACS) activity more conspicuously under salt stress than no stress. The increased GB accumulation together with reduced ethylene under salt stress by SA application was associated with increased glutathione (GSH) content and lower oxidative stress. These positive effects on plant metabolism induced by SA application led to improved photosynthesis and growth under salt stress. These results suggest that SA induces GB accumulation through increased Met and suppresses ethylene formation under salt stress and enhances antioxidant system resulting in alleviation of adverse effects of salt stress on photosynthesis and growth. These effects of SA were substantiated by the findings that application of SA-analogue, 2, 6, dichloro-isonicotinic acid (INA) and ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG) resulted in similar effects on Met, GB, ethylene production, photosynthesis and growth under salt stress. Future studies on the interaction between SA, GB and ethylene could be exploited for adaptive responses of plants under salt stress.


      PubDate: 2014-04-15T20:27:48Z
       
  • Molecular cloning and characterization of a novel adenylyl cyclase gene,
           HpAC1, involved in stress signaling in Hippeastrum x hybridum
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Brygida Świeżawska , Krzysztof Jaworski , Agnieszka Pawełek , Weronika Grzegorzewska , Piotr Szewczuk , Adriana Szmidt-Jaworska
      Adenylyl cyclases (ACs) are enzymes that generate cyclic AMP, which is involved in different physiological and developmental processes in a number of organisms. Here, we report the cloning and characterization of a new plant adenylyl cyclases (AC) gene, designated HpAC1, from Hippeastrum x hybridum. This gene encodes a protein of 206 amino acids with a calculated molecular mass of 23 kD and an isoelectric point of 5.07. The predicted amino acid sequence contains all the typical features of and shows high identity with putative plant ACs. The purified, recombinant HpAC1 is able to convert ATP to cAMP. The complementation test that was performed to analyze the ability of HpAC1 to compensate for the AC deficiency in the Escherichia coli SP850 strain revealed that HpAC1 functions as an adenylyl cyclase and produces cyclic AMP. Moreover, it was shown that the transcript level of HpAC1 and cyclic AMP concentration changed during certain stress conditions. Both mechanical damage and Phoma narcissi infection lead to two sharp increases in HpAC1 mRNA levels during a 72-h test cycle. Changes in intracellular cAMP level were also observed. These results may indicate the participation of a cAMP-dependent pathway both in rapid and systemic reactions induced after disruption of symplast and apoplast continuity.


      PubDate: 2014-04-15T20:27:48Z
       
  • Cerium Dioxide and Zinc Oxide Nanoparticles Alter the Nutritional Value of
           Soil Cultivated Soybean Plants
    • Abstract: Publication date: Available online 5 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Jose R. Peralta-Videa , Jose A. Hernandez-Viezcas , Lijuan Zhao , Baltazar Corral Diaz , Yuan Ge , John H. Priester , Patricia Ann Holden , Jorge L. Gardea-Torresdey
      The aim of this study was to determine nutrient elements in soybean (Glycine max) plants cultivated in farm soil amended with nCeO2 at 0-1000 mg kg-1 and nZnO at 0-500 mg kg-1. Digested samples were analyzed by ICP-OES/MS. Compared to control, pods from nCeO2 at 1000 mg kg-1 had significantly less Ca but more P and Cu, while pods from 100 mg kg-1 nZnO had more Zn, Mn, and Cu. Plants treated with nZnO showed significant correlations among Zn, P, and S in pods with Zn in roots. Correlations among pod Zn/root Zn was r = 0.808 (p ≤ 0.01) and pod P/root P was r = 0.541 (p ≤ 0.05). The correlation among pod S/root S was r = -0.65 (p ≤ 0.01). While nCeO2 treatments exhibited significant correlations between pod Ca/root Ca (r = 0.645, p ≤ 0.05). The data suggest that nCeO2 and nZnO alter the nutritional value of soybean, which could affect the health of plants, humans, and animals.
      Graphical abstract image

      PubDate: 2014-04-10T23:25:35Z
       
  • Photochemical and biophysical feedbacks of C3 and C4 Mediterranean
           halophytes to atmospheric CO2 enrichment confirmed by their stable isotope
           signatures
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): B. Duarte , D. Santos , H. Silva , J.C. Marques , I. Caçador
      According the latest predictions, an increase of about two times in atmospheric CO2 concentrations, is expected to occur by the end of this century. In order to understand the effects of this atmospheric composition changes on two abundant Mediterranean halophytes (Halimione portulacoides and Spartina maritima), mesocosmos trials were performed simulating two atmospheric CO2 environments (380 ppm and 760 ppm of CO2 respectively). The two chosen halophyte species present different metabolic characteristics: H. portulacoides, is a C3 specie while S. maritima is a C4 species. Distinct feedbacks were obtained for each of the studied species. Stable Isotope discrimination showed that both species showed an enhancement of the Rubisco carboxylation capacity and photosynthetic efficiency mostly due to an increase in intracellular [CO2]. In H. portulacoides CO2 fertilization induced an enhancement of ETR and a decrease in non-photochemical quenching and in dissipated energy fluxes. On the other hand the C4 grass S. maritima, already at full capacity, showed no photosynthetic enhancement. In fact this highly productive grass presented lower photosynthetic efficiencies accompanied by increases in dissipated energy fluxes mostly due to reductions in energy flux associated with the transport of reducing power throughout the quinone pool. The accumulation of reducing power led to oxidative stress, and thus the photosynthetic ability of this grass was greatly reduced. Both these feedbacks to realistic future CO2 concentrations are important consideration for in future primary productivity models, indicating a possible reduced abundance of the pioneer S. maritima and an increased biomass spreading of the sediment stabilizer H. portulacoides, inevitably affecting the morphology and function of the salt marshes imposed by these atmospheric changes, both in terms of ecosystem functioning and loss of biodiversity.


      PubDate: 2014-04-10T23:25:35Z
       
  • Identification and characterization of the 14-3-3 gene family in Hevea
           brasiliensis
    • Abstract: Publication date: Available online 5 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Zi-Ping Yang , Hui-Liang Li , Dong Guo , Xiao Tang , Shi-Qing Peng
      The 14-3-3 proteins are a family of conserved phospho-specific binding proteins involved in diverse physiological processes. Although the genome-wide analysis of this family has been carried out in certain plant species, little is known about 14-3-3 protein genes in rubber tree (Hevea brasiliensis). In this study, we identified 10 14-3-3 protein genes (designated as HbGF14a to HbGF14j) in the latest rubber tree genome. A phylogenetic tree was constructed and found to demonstrate that HbGF14s can be divided into two major groups. Tissue-specific expression profiles showed that 10 HbGF14 were expressed in at least one of the tissues, which suggested that HbGF14s participated in numerous cellular processes. The 10 HbGF14s responded to jasmonic acid (JA) and ethylene (ET) treatment, which suggested that these HbGF14s were involved in response to JA and ET signaling. The target of HbGF14c protein was related to small rubber particle protein, a major rubber particle protein that is involved in rubber biosynthesis. These findings suggested that 14-3-3 proteins may be involved in the regulation of natural rubber biosynthesis.


      PubDate: 2014-04-10T23:25:35Z
       
  • The constitutive expression of a two transgene construct enhances the
           abiotic stress tolerance of chrysanthemum
    • Abstract: Publication date: Available online 5 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Aiping Song , Juan An , Zhiyong Guan , Jiafu Jiang , Fadi Chen , Wanghuai Lou , Weimin Fang , Zhaolei Liu , Sumei Chen
      Various abiotic stresses downgrade the quality and productivity of chrysanthemum. A construct carrying both CcSOS1 (from Chrysanthemum crassum) and CdICE1 (from C. dichrum) was constitutively expressed in the chrysanthemum variety ‘Jinba’. The transgenic plants were superior to the wild type (WT) ones with respect to their sensitivity to low temperature, drought and salinity, as measured by visible damage and plant survival. Salinity stressed transgenic plants accumulated more proline, and their level of superoxide dismutase and peroxidase activity was higher than in WT plants. At the physiological level, they suffered less loss of viable leaf area, maintained a lower leaf electrolyte conductivity and retained more chlorophyll (a+b). The ratio between the K+ and Na+ content was higher in the root, stem and median leaves of salinity stressed transgenic plants than in those of WT plants.


      PubDate: 2014-04-10T23:25:35Z
       
  • Comparison of oxidative stress in four Tillandsia species exposed to
           cadmium
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Jozef Kováčik , Petr Babula , Bořivoj Klejdus , Josef Hedbavny
      This is first study comparing four morphologically variable species of the genus Tillandsia and therefore various responses to the cadmium (Cd) action were expected. In accordance, Cd accumulation increased in order Tillandsia fasciculata < Tillandsia brachycaulos < Tillandsia pruinosa < Tillandsia capillaris, reaching 29.6 and 197.4 μg g−1 DW in first and last species after watering with 2 μM Cd2+ solution over 30 days. Fluorescence visualization of oxidative stress confirmed increase in ROS and especially elevation in hydroperoxides though no visible symptoms appeared on the plants. At the same time, nitric oxide generation and nitroso-glutathione depletion by Cd treatment were typically observed. Fluorescence staining of Cd using two dyes (PhenGreen and Leadmium) showed that Leadmium fits better with AAS quantification. Macro- and micro-nutrients were not considerably affected except for zinc. Reduced glutathione content was the highest in control T. fasciculata while oxidized glutathione in T. capillaris. Ascorbic acid amount revealed extreme quantitative differences among species and decreased in T. fasciculata only. Free amino acids accumulation was similar among species except for T. capillaris and Cd caused both depletion and increase but without high quantitative differences. Data are explanatively discussed in the context of limited literature related to oxidative stress in epiphytic plants and with general responses of plants to cadmium/heavy metals.


      PubDate: 2014-04-10T23:25:35Z
       
  • Influence of crop load on the expression patterns of starch metabolism
           genes in alternate-bearing Citrus trees
    • Abstract: Publication date: Available online 5 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Sergio G. Nebauer , Begoña Renau-Morata , Yolanda Lluch , Edurne Baroja-Fernández , Javier Pozueta-Romero , Rosa-Victoria Molina
      The fruit is the main sink organ in Citrus and captures almost all available photoassimilates during its development. Consequently, carbohydrate partitioning and starch content depend on the crop load of Citrus trees. Nevertheless, little is known about the mechanisms controlling the starch metabolism at the tree level in relation to presence of fruit. The aim of this study was to find the relation between the seasonal variation of expression and activity of the genes involved in carbon metabolism and the partition and allocation of carbohydrates in ‘Salustiana’ sweet orange trees with different crop loads. Metabolisable carbohydrates, and the expression and activity of the enzymes involved in sucrose and starch metabolism, including sucrose transport, were determined during the year in the roots and leaves of 40-year-old trees bearing heavy crop loads (‘on’ trees) and trees with almost no fruits (‘off’ trees). Fruit altered photoassimilate partitioning in trees. Sucrose content tended to be constant in roots and leaves, and surplus fixed carbon is channeled to starch production. Differences between ‘on’ and ‘off’ trees in starch content can be explained by differences in ADP-glucose pyrophosphorylase (AGPP) expression/activity and α-amylase activity which varies depending on crop load. The observed relation of AGPP and UGPP (UDP-glucose pyrophosphorylase) is noteworthy and indicates a direct link between sucrose and starch synthesis. Furthermore, different roles for sucrose transporter SUT1 and SUT2 have been proposed. Variation in soluble sugars content cannot explain the differences in gene expression between the ‘on’ and ‘off’ trees. A still unknown signal from fruit should be responsible for this control.


      PubDate: 2014-04-10T23:25:35Z
       
  • A transcriptional approach to unravel the connection between
           phospholipases A2 and D and ABA signal in citrus under water stress
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Paco Romero , M. Teresa Lafuente , Fernando Alférez
      The effect of water stress on the interplay between phospholipases (PL) A2 and D and ABA signalling was investigated in fruit and leaves from the sweet orange Navelate and its fruit-specific ABA-deficient mutant Pinalate by studying simultaneously expression of 5 PLD and 3 PLA2-encoding genes. In general, expression levels of PLD-encoding genes were higher at harvest in the flavedo (coloured outer part of the peel) from Pinalate. Moreover, a higher and transient increase in expression of CsPLDα, CsPLDβ, CsPLDδ and CsPLDζ was observed in the mutant as compared to Navelate fruit under water stress, which may reflect a mechanism of acclimation to water stress influenced by ABA deficiency. An early induction in CsPLDγ gene expression, when increase in peel damage during fruit storage was most evident, suggested a role for this gene in membrane degradation processes during water stress. Exogenous ABA on mutant fruit modified the expression of all PLD genes and reduced the expression of CsPLDα and CsPLDβ by 1 week to levels similar to those of Navelate, suggesting a repressor role of ABA on these genes. In general, CssPLA 2 α and β transcript levels were lower in flavedo from Pinalate than from Navelate fruit during the first 3 weeks of storage, suggesting that expression of these genes also depends at least partially on ABA levels. Patterns of expression of PLD and PLA2-encoding genes were very similar in Navelate and Pinalate leaves, which have similar ABA levels, when comparing both RH conditions. Results comparison with other from previous works in the same experimental systems helped to decipher the effect of the stress severity on the differential response of some of these genes under dehydration conditions and pointed out the interplay between PLA2 and PLD families and their connection with ABA signalling in citrus.


      PubDate: 2014-04-10T23:25:35Z
       
  • Activity levels and expression of antioxidant enzymes in the
           ascorbate–glutathione cycle in artificially aged rice seed
    • Abstract: Publication date: July 2014
      Source:Plant Physiology and Biochemistry, Volume 80
      Author(s): Guangkun Yin , Xia Xin , Chao Song , Xiaoling Chen , Jinmei Zhang , Shuhua Wu , Ruifang Li , Xu Liu , Xinxiong Lu
      Reactive oxygen species are the main contributors to seed deterioration. In order to study scavenging systems for reactive oxygen species in aged seed, we performed analyses using western blotting, real-time quantitative reverse-transcription polymerase chain reaction, high-performance liquid chromatography, and antioxidant enzyme activity analyses in artificially aged rice seeds (Oryza sativa L. cv. wanhua no.11). Aging seeds by storing them at 50 °C for 1, 9, or 17 months increased the superoxide radical and hydrogen peroxide levels and reduced the germination percentage from 99% to 92%, 55%, and 2%, respectively. The activity levels of superoxide dismutase (SOD), glutathione reductase (GR), and dehydroascorbate reductase (DHAR) did not change in aged seeds. In contrast, the activity levels of catalase (CAT), ascorbate peroxidase (APX), and monodehydroascorbate reductase (MDHAR) were significantly decreased in aged seeds, as were the expression of catalase and cytosolic ascorbate peroxidase protein. Transcript accumulation analysis showed that specific expression patterns were complex for each of the antioxidant enzyme types in the rice embryos. Overall, the expression of most genes was down-regulated, along with their protein expression. In addition, the reduction in the amount of ascorbate and glutathione was associated with the reduction in scavenging enzymes activity in aged rice embryos. Our data suggest that the depression of the antioxidant system, especially the reduction in the expression of CAT1, APX1 and MDHAR1, may be responsible for the accumulation of reactive oxygen species in artificially aged seed embryos, leading to a loss of seed vigor.


      PubDate: 2014-04-05T19:15:34Z
       
  • Functional analysis of the durum wheat gene TdPIP2;1 and its promoter
           region in response to abiotic stress in rice
    • Abstract: Publication date: June 2014
      Source:Plant Physiology and Biochemistry, Volume 79
      Author(s): Malika Ayadi , Delphine Mieulet , Denis Fabre , Jean-Luc Verdeil , Aurore Vernet , Emmanuel Guiderdoni , Khaled Masmoudi
      In a previous work, we demonstrated that expression of TdPIP2;1 in Xenopus oocytes resulted in an increase in P f compared to water injected oocytes. Phenotypic analyses of transgenic tobacco plants expressing TdPIP2;1 generated a tolerance phenotype towards drought and salinity stresses. To elucidate its stress tolerance mechanism at the transcriptional level, we isolated and characterized the promoter region of the TdPIP2;1 gene. A 1060-bp genomic fragment upstream of the TdPIP2;1 translated sequence has been isolated, cloned, and designated as the proTdPIP2;1 promoter. Sequence analysis of proTdPIP2;1 revealed the presence of cis regulatory elements which could be required for abiotic stress responsiveness, for tissue-specific and vascular expression. The proTdPIP2;1 promoter was fused to the β-glucuronidase (gusA) gene and the resulting construct was transferred into rice (cv. Nipponbare). Histochemical analysis of proTdPIP2;1::Gus in rice plants revealed that the GUS activity was observed in leaves, stems and roots of stably transformed rice T3 plants. Histological sections prepared revealed accumulation of GUS products in phloem, xylem and in some cells adjacent to xylem. The transcripts were up-regulated by dehydration. Transgenic rice plants overexpressing proTdPIP2;1 in fusion with TdPIP2;1, showed enhanced drought tolerance, while wild type plants were more sensitive and exhibited symptoms of wilting and chlorosis. These findings suggest that expression of the TdPIP2;1 gene regulated by its own promoter achieves enhanced drought tolerance in rice.


      PubDate: 2014-04-05T19:15:34Z
       
  • Sensitivity of the aldehyde-induced and free fatty acid-induced activities
           of plant uncoupling protein to GTP is regulated by the ubiquinone
           reduction level
    • Abstract: Publication date: June 2014
      Source:Plant Physiology and Biochemistry, Volume 79
      Author(s): Andrzej M. Woyda-Ploszczyca , Wieslawa Jarmuszkiewicz
      Using isolated potato tuber mitochondria possessing uncoupling protein (StUCP), we found that, under non-phosphorylating conditions, the sensitivity of aldehyde (all trans-retinal or 4-hydroxy-2-nonenal)-induced and fatty acid (linoleic acid)-induced StUCP-mediated proton leaks to GTP is controlled by the endogenous ubiquinone (Q) reduction level. The action of StUCP activators was abolished by GTP only when Q was sufficiently oxidized, but no inhibitory effect was observed when Q was highly reduced. Thus, the Q reduction level-dependent regulation of StUCP inhibition functions independently of the type of UCP activation and could be an important physiological factor affecting the efficiency of UCP-catalyzed uncoupling in plant mitochondria.


      PubDate: 2014-04-05T19:15:34Z
       
  • Genome-wide identification and expression profiling of the cystatin gene
           family in apple (Malus × domestica Borkh.)
    • Abstract: Publication date: June 2014
      Source:Plant Physiology and Biochemistry, Volume 79
      Author(s): Yanxiao Tan , Suncai Wang , Dong Liang , Mingjun Li , Fengwang Ma
      Cystatins or phytocystatins (PhyCys) comprise a family of plant-specific inhibitors of cysteine proteinases. Such inhibitors are thought to be involved in the regulation of several endogenous processes as well as defense against biotic or abiotic stresses. However, information about this family is limited in apple. We identified 26 PhyCys genes within the entire apple genome. They were clustered into three distinct groups distributed across several chromosomes. All of their putative proteins contained one or two typical cystatin domains, which shared the characteristic motifs of PhyCys. Eight selected genes displayed differential expression patterns in various tissues. Moreover, their transcript levels were also up-regulated significantly in leaves during maturation, senescence or in response to treatment with one or more abiotic stresses. Our results indicated that members of this family may function in tissue development, leaf senescence, and adaptation to adverse environments in apple.


      PubDate: 2014-04-05T19:15:34Z
       
  • BnNAC485 is involved in abiotic stress responses and flowering time in
           Brassica napus
    • Abstract: Publication date: June 2014
      Source:Plant Physiology and Biochemistry, Volume 79
      Author(s): Lu Ying , Haiying Chen , Weiming Cai
      NAC domain proteins are plant-specific transcription factors that play important roles in plant growth and development. In this present study, we isolated BnNAC485 from Brassica napus L. (cv. HuYou15) and found that it showed high homology (84% at the amino acid level) with a NAC protein called AtRD26/ANAC072. BnNAC485 was specifically expressed in cotyledons and leaves of young seedlings, and expression was induced by abiotic stress and abscisic acid (ABA) treatment. The BnNAC485 protein localized to the nucleus. Over-expression of BnNAC485 enhanced tolerance to abiotic stress compared with wild-type plants in both B. napus and Arabidopsis thaliana. Furthermore, under exogenous ABA stress, BnNAC485 over-expression lines showed hypersensitivity to this treatment compared with wild-type B. napus and A. thaliana plants. Moreover, exogenous ABA treatment enhanced stomatal closing in B. napus plants over-expressing BnNAC485. Real-time RT-PCR assays showed that some abiotic- or ABA-responsive genes were up-regulated in A. thaliana plants over-expressing BnNAC485. Additionally, the transgenic lines flowered earlier than the wild-type B. napus and A. thaliana plants and the expression patterns of certain circadian clock genes were found to have changed. These results suggest that BnNAC485 acts in response to abiotic stress in plants via an ABA-mediated pathway and this gene can also alter plant flowering time.


      PubDate: 2014-04-05T19:15:34Z
       
  • Editorial Board
    • Abstract: Publication date: May 2014
      Source:Plant Physiology and Biochemistry, Volume 78




      PubDate: 2014-03-31T19:16:20Z
       
  • Enzymatic characterization of Chlamydomonas reinhardtii glycolate
           dehydrogenase and its nearest proteobacterial homologue
    • Abstract: Publication date: Available online 19 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Mohamed H. Aboelmy , Christoph Peterhansel
      Chlamydomonas reinhardtii contains a unique glycolate dehydrogenase (CrGlcDH) for glycolate oxidation in photorespiration that is different in structure from the GlcDH enzymes of heteroptrophic prokaryotes and the glycolate oxidases of higher plants. Here, we purified the recombinantly overexpressed enzyme and characterized its enzymatic properties. CrGlcDH uses d-lactate, but not l-lactate, as an alternative substrate with similar catalytic efficiency compared to glycolate. Other short-chain organic acids are only very slowly oxidized. Only the artificial electron acceptors DCIP and PMS, but neither flavine mono- or dinucleotides nor nicotinamide dinucleotides or cytochrome c, were used as electron acceptors by the recombinant enzyme. The enzyme is sensitive to CuSO4 suggesting function of reactive sulfhydryl groups in catalysis. Accordingly, mutational analysis of a putative Fe–S cluster indicated an important function of this domain in catalysis. Evolutionary sequence analysis confirmed that CrGlcDH belongs to a so far biochemically uncharacterized group of enzymes that is found in chlorophytes and some proteobacteria. The most related proteobacterial homologue was only active with d-lactate, but not glycolate as a substrate. Our results indicate that in the chlorophytes an existing enzyme changed its substrate specificity to support photorespiratory glycolate oxidation.


      PubDate: 2014-03-21T12:51:07Z
       
  • Polyamine-induced nitric oxide generation and its potential requirement
           for peroxide in suspension cells of soybean cotyledon node callus
    • Abstract: Publication date: Available online 15 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Beining Yang , Junzhang Wu , Fengming Gao , Jun Wang , Guoxing Su
      Polyamines (PAs) induce nitric oxide (NO) generation in plant tissues; however, their mechanism is still unclear. In the present study, suspension cells of soybean cotyledon-node callus were employed. Using a NO-specific fluorescent dye, DAF-FM-DA (3-amino, 4-aminomethyl-2', 7'-difluorescein, diacetate), and laser confocal scanning microscopy, changes in NO generation induced by exogenous PAs were examined. The results of this study showed that NO fluorescence was significantly induced above endogenous levels when callus cells were treated with 0.05 mM PAs. However, putrescine (Put) was the most active PA. The observed NO release by PAs was rapid and without an apparent lag phase. The response was quenched when the suspension cells were treated with the NO-specific scavenger cPTIO (2- (4- carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-1- oxy- 3-oxide). When 0.01 mM L-aminoguanidine (L-AG) was applied prior to the PA treatments, the NO fluorescence was diminished, and the inhibition of NO fluorescence was correlated with a decrease in diamine oxidase (DAO) activity. When callus cells were incubated with 0.1 mM catalase (CAT) and 1.0 mM N’N-dimethylthiourea (DMTU) prior to PA application, NO release was significantly reduced. In sum, our data provided evidence for PA-induced NO generation in suspension cells of soybean cotyledon node callus and demonstrated that peroxide, potentially derived from PA oxidative degradation, was involved in NO release induced by PAs.
      Graphical abstract image

      PubDate: 2014-03-17T00:12:12Z
       
  • Characterizing Photoinhibition and Photosynthesis in Juvenile-red Versus
           Mature-green Leaves of Jatropha curcas L
    • Abstract: Publication date: Available online 13 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Sanjay Ranjan , Ruchi Singh , Munna Singh , Uday V. Pathre , Pramod A. Shirke
      The new leaves of Jatropha curcas (L.) appear dark red in colour due to the presence of anthocyanin pigments, these leaves subsequently turn green on maturity. The aim of the study was to characterize the photosynthetic efficiency of the juvenile red and mature green leaves and to understand the possible role of anthocyanin pigment in the juvenile leaves of J. curcas. We studied the localization of anthocyanin pigment, reflectance properties, diurnal gas-exchange performance, carboxylation efficiency and photosynthetic efficiency under different light intensities by investigation of the photochemical and non-photochemical energy dissipation processes related to Photosystem II (PSII) and Photosystem I (PSI), of the juvenile and the mature leaves of J. curcas. The JIP test analysis of chlorophyll a fluorescence transients and the gas-exchange studies revels the low photosynthetic efficiency of red leaves is due to the immaturity of the leaf. The low value of quantum yield of non-photochemical energy dissipation due to acceptor side limitation, Y (NA) under high light in the red leaf, suggests that over-reduction of PSI acceptor side was prevented and it results in the accumulation of oxidized P700, which dissipates excess light energy harmlessly as heat and thereby alleviate photoinhibition of PSI in case of the juvenile red leaves. Further our results of photoinhibition and relaxation on exposure of red and green leaves to monochromatic blue light showed that effective quantum yield of PSII recovers faster and completely under darkness in juvenile red leaves as compared to mature green leaves, supporting the role of anthocyanin pigments in protecting both PSII and PSI in the red leaves.
      Graphical abstract image

      PubDate: 2014-03-17T00:12:12Z
       
  • Effect of light on growth and endogenous hormones in Chlorella minutissima
           (Trebouxiophyceae)
    • Abstract: Publication date: Available online 13 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): W.A. Stirk , P. Bálint , D. Tarkowská , O. Novák , G. Maróti , K. Ljung , V. Turečková , M. Strnad , V. Ördög , J. van Staden
      Plant growth regulators (PGRs) play an important role in mediating growth and stress responses in plants. Light influences PGRs concentrations in vascular plants. The effect of light on growth and endogenous PGR concentrations in microalgae was investigated in the present study. Chlorella minutissima MACC 360 was grown in 14:10 h light:dark (L:D), continuous dark (CD) and continuous dark with the addition of 5 g L-1 glucose (CD+G) for 48 h. Cultures were synchronized in the L:D cultures, increasing in size during the light period and dividing during the dark period. C. minutissima cells did not increase in size or undergo cell division in CD cultures. In CD+G conditions, the cultures were no longer synchronized but did continue to increase in cell size and constantly underwent cell division although fewer cells divided than in the L:D cultures. Endogenous auxin and cytokinin concentrations increased and gibberellin concentrations decreased over time in the actively growing cultures (L:D and CD+G) but did not increase in the CD cultures. The largest increase in indole content was in the CD+G cultures while the L:D cultures had the largest cytokinin increase. Brassinosteroid concentrations decreased over time in all the cultures including those grown in CD conditions. Abscisic acid (ABA) concentrations were low and only increased in the CD cultures. These results show that endogenous PGRs were affected by the light regime and/or culture growth.


      PubDate: 2014-03-17T00:12:12Z
       
  • Developmental stimuli and stress factors affect expression of ClGLP1, an
           emerging allergen-related gene in Citrus limon
    • Abstract: Publication date: Available online 15 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): L. Bruno , N.D. Spadafora , D. Iaria , A. Chiappetta , M.B. Bitonti
      Germins and germin-like proteins (GLPs) constitute an ubiquitous family of plant proteins that seem to be involved in many developmental and stress related processes. A novel GLP cDNA was isolated from Citrus limon and structural features and genomic organization were investigated by in silico and Southern blots analysis. In lemon, the ClGLP1 encodes a 24.38 kDa which possesses a conserved motif of plant GLPs proteins. A phylogetic analysis mapped ClGLP1 as belonging to the GER3 subfamily into the GLP1 group of large GLP family. ClGLP1 was differentially expressed in the various organs and was highest in mature fruit. Moreover, expression in the fruit was tissue- and stage-related as well as dependent on agricultural practice (organic vs conventional). ClGLP1 transcripts increased during the transition from the green (180 days after blooming) to the yellow (240 days after blooming) mature fruit and were strongly enhanced in yellow mature fruit from organic compared with conventional culture. A sudden and systemic increase in ClGLP1 expression level was observed in leaves injured by wounding, together with an increase of endogenous H2O2 amount. Notably, an enhancement of H202 was observed in fruit peel during transition from green to yellow fruit stage. All together our data showed that ClGLP1 expression can be modulated in relation to both developmental stimuli and culture practices; evidence is also provided that through an oxidase activity this gene could play a role in fruit maturation as well as in stress responses.


      PubDate: 2014-03-17T00:12:12Z
       
  • Comparative proteomics of Euphorbia kansui Liou milky sap at two different
           developmental stages
    • Abstract: Publication date: Available online 15 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Xueyan Zhao , Jingjing Si , Yan Miao , Yong Peng , Li Wang , Xia Cai
      Euphorbia kansui Liou is a unique traditional Chinese medicinal herb. Its milky sap proteins play important roles in laticifer development, synthesis and transport of its biologically active substances. A proteomic approach was applied to analyze the E. kansui latex proteins related to laticifer development and secondary metabolite synthesis by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional polyacrylamide gel electrophoresis. A total of 125 milky sap proteins associated with development of laticifers, disease and defense, and general metabolism were identified, and 19 differentially expressed proteins at two different developmental stages of laticifers were successfully detected. Peroxidase, cytochrome P450 mono-oxygenase superfamily, lipoxygenase, and multidrug resistance protein ABC transporter family may be involved in laticifer development, secondary metabolite synthesis and transport, and plant physiology.


      PubDate: 2014-03-17T00:12:12Z
       
  • Changes in biosynthesis and metabolism of glutathione upon ochratoxin A
           stress in Arabidopsis thaliana
    • Abstract: Publication date: Available online 12 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Yan Wang , Weiwei Zhao , Junran Hao , Wentao Xu , YunBo Luo , Weihong Wu , Zhuojun Yang , Zhihong Liang , Kunlun Huang
      Ochratoxin A (OTA) is one of the most toxic mycotoxins, which is toxic to plants and simulates oxidative stress. Glutathione is an important antioxidant in plants and is closely associated with detoxification in cells. We have previously shown that OTA exposure induces obvious expression differences in genes associated with glutathione metabolism. To characterize glutathione metabolism and understand its role in OTA phytotoxicity, we observed the accumulation of GSH in the detached leaves of Arabidopsis thaliana under OTA treatment. OTA stimulated a defense response through enhancing glutathione-S-transferase, glutathione peroxidase, glutathione reductase activities, and the transcript levels of these enzymes were increased to maintain the total glutathione content. Moreover, the level of oxidized glutathione (GSSG) was increased and the ascorbate–glutathione cycle fluctuated in response to OTA. The depletion of glutathione using buthionine sulfoximine (BSO, inhibitor of glutamate–cysteine ligase) had no profound effect on OTA toxicity, as glutathione was regenerated through the ascorbate–glutathione cycle to maintain the total glutathione content. The ROS, MDA and GSH accumulation was significantly affected in the mutant gsh1, gr1 and gpx2 after treatment with OTA, which indicated that glutathione metabolism is directly involved in the oxidative stress response of Arabidopsis thaliana subjected to OTA. In conclusion, date demonstrate that glutathione-associated metabolism is closely related with OTA stress and glutathione play a role in resistance of Arabidopsis subjected to OTA.


      PubDate: 2014-03-17T00:12:12Z
       
  • Soluble expression of Spinach psbC gene in Escherichiacoli and
           in vitro reconstitution of CP43 coupled with chlorophyll a only
    • Abstract: Publication date: Available online 12 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Ji-Liu , Si-Si Xie , Yue-Luo , Guo-Fei Zhu , Lin-Fang Du
      CP43 is a chlorophyll a (Chl a) and β-carotene (β-Car) binding protein encoded by psbC gene. In this study, psbC gene isolated from Spinach was expressed in Escherichia coli in soluble state. After lysis of the cells, the apoproteins purified by nickel affinity chromatography were examined by SDS-PAGE and Western-blot. Next, reconstitution experiment was carried out in vitro and the formation of stable pigment–protein complex was analyzed by partially denaturing electrophoresis. After purifying reconstituted CP43 (rCP43) from free pigments (FPs) by sucrose gradient ultracentrifugation and subsequently ion exchange chromatography (IEC), the eluate was analyzed by partially denaturing electrophoresis to confirm stability of the reconstructed complex. Finally, analyses of spectroscopic character of the eluate revealed that in vitro reconstitution was achieved and FPs were completely removed from the pigment–protein complex. Comparison between the absorption spectra of the rCP43 and native CP43 (nCP43) showed the lack of peaks between 450 and 500 nm, illustrating that the β-Car was stripped off rCP43. In brief, it is feasible to obtain a reconstituted protein binding Chl a only, indicating that the occupancy of the β-Car site has small impact on the stabilization of CP43. However, β-Car shows strong interaction with Chl a, inducing the hyperchromic effect in blue region of spectrum and the blue shift of the 438.5 nm and 673.5 nm absorption band to 437 nm and 671 nm respectively. To some extent, our research is suggestive that β-Car, coupled loosely with CP43, contributes to the precise orientation of Chl a in vivo.


      PubDate: 2014-03-17T00:12:12Z
       
  • Knockout mutants as a tool to identify the subunit composition of
           Arabidopsis glutamine synthetase isoforms
    • Abstract: Publication date: Available online 12 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Milan Dragićević , Slađana Todorović , Milica Bogdanović , Biljana Filipović , Danijela Mišić , Ana Simonović
      Glutamine synthetase (GS) is a key enzyme in nitrogen assimilation, which catalyzes the formation of glutamine from ammonia and glutamate. Plant GS isoforms are multimeric enzymes, recently shown to be decamers. The Arabidopsis genome encodes five cytosolic (GS1) proteins labeled as GLN1;1 through GLN1;5 and one chloroplastic (GS2) isoform, GLN2;0. However, as many as 11 GS activity bands were resolved from different Arabidopsis tissues by Native PAGE and activity staining. Western analysis showed that all 11 isoforms are composed exclusively of 40 kDa GS1 subunits. Of five GS1 genes, only GLN1;1, GLN1;2 and GLN1;3 transcripts accumulated to significant levels in vegetative tissues, indicating that only subunits encoded by these three genes produce the 11-band zymogram. Even though the GS2 gene also had significant expression, the corresponding activity was not detected, probably due to inactivation. To resolve the subunit composition of 11 active GS1 isoforms, homozygous knockout mutants deficient in the expression of different GS1 genes were selected from the progeny of T-DNA insertional SALK and SAIL lines. Comparison of GS isoenzyme patterns of the selected GS1 knockout mutants indicated that all of the detected isoforms consist of varying proportions of GLN1;1, GLN1;2 and GLN1;3 subunits, and that GLN1;1 and GLN1;3, as well as GLN1;2 and GLN1;3 and possibly GLN1;1 and GLN1;2 proteins combine in all proportions to form active homo- and heterodecamers.
      Graphical abstract image

      PubDate: 2014-03-17T00:12:12Z
       
  • Biosynthesis of catechin components is differentially regulated
           in dark-treated tea (Camellia sinensis L.)
    • Abstract: Publication date: Available online 3 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Gaojie Hong , Jie Wang , Yong Zhang , Danielle Hochstetter , Shuping Zhang , Yue Pan , Yunlong Shi , Ping Xu , Yuefei Wang
      Tea (Camellia sinensis L.) is a crop with both commercial and medicinal value with remarkably high polyphenol content in the form of catechins. To understand the molecular regulation of catechin biosynthesis in tea, we treated the tea plants with darkness. We used qRT-PCR to validate the expression of genes involved in catechin biosynthesis. It indicated that dark treatment displayed different effects on the genes participating in tea flavonoid (FL) pathway. The early genes of FL biosynthesis pathway, CHSI, F3H and DFR, remained at steady expression levels when treated by darkness. It is noteworthy that the expression level of LAR increased and the level of ANS decreased under dark conditions. The vanillin assay showed that the dark-treated plants contained lower levels of total catechins than those grown under normal conditions. The HPLC analysis further demonstrated the changes in biosynthesis of catechins under these conditions. In accordance with the gene expression pattern, the content of epicatechins (ECs) declined and that of catechins (Cs) was elevated in response to the darkness. Our study uncovered the molecular mechanisms and biochemical changes of shading in tea cultivation.


      PubDate: 2014-03-06T22:41:18Z
       
  • Strategies for Cd accumulation in Dittrichia viscosa (L.) Greuter:
           Role of the cell wall, non-protein thiols and organic acids
    • Abstract: Publication date: Available online 3 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): R. Fernández , D. Fernández-Fuego , A. Bertrand , A. González
      Dittrichia viscosa (L.) Greuter is plant species commonly found in degraded zones of Asturias (Spain), where it accumulates high levels of Cd, but the mechanisms involved in this response in non-model plants have not been elucidated. In this way, we analysed the fraction of the total Cd bound to the cell walls, the ultrastructural localization of this metal, and non-protein thiol and organic acid concentrations of two clones of D. viscosa: DV-A (from a metal-polluted soil) and DV-W (from a non-polluted area). After 10 days of hydroponic culture with Cd, fractionation and ultrastructural localisation studies showed that most of the Cd accumulated by D. viscosa was kept in the cell wall. Thenon-protein thiol content rose in D. viscosa with Cd exposure, especially in the non-metallicolous DV-W clone, and in both clones we found with Cd exposure a synthesis de novo of phytochelatins PC2 and PC3 in shoots and roots and also of other phytochelatin-related compounds, particularly in roots. Regarding organic acids, their concentration in both clones decreased in shoots after Cd treatment, but increased in roots, mainly due to changes in the citric acid concentration. Thus, retention of Cd in the cell wall seems to be the first strategy in response to metal entry in D. viscosa and once inside cells non-protein thiols and organic acids might also participate in Cd tolerance.


      PubDate: 2014-03-06T22:41:18Z
       
  • The involvement of expansins in responses to phosphorus availability in
           wheat, and its potentials in improving phosphorus efficiency of plants
    • Abstract: Publication date: Available online 3 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Yang-yang Han , Shan Zhou , Yan-hui Chen , Xiangzhu Kong , Ying Xu , Wei Wang
      Phosphorus (P) is a critical macronutrient required for numerous functions in plants and is one of the limiting factors for plant growth. Phosphate availability has a strong effect on root system architecture. Expansins are encoded by a superfamily of genes that are organized into four families, and growing evidence has demonstrated that expansins are involved in almost all aspects of plant development, especially root development. In the current study, we demonstrate that expansins may be involved in increasing phosphorus availability by regulating the growth and development of plant roots. Multiple expansins (five α- and nine β-expansin genes) were up- or down-regulated in response to phosphorus and showed different expression patterns in wheat. Meanwhile, the expression level of TaEXPB23 was up-regulated at excess-P condition, suggesting the involvement of TaEXPB23 in phosphorus adaptability. Overexpression of the TaEXPB23 resulted in improved phenotypes, particularly improved root system architecture, as indicated by the increased number of lateral roots in transgenic tobacco plants under excess-P and low-P conditions. Thus, these transgenic plants maintained better photosynthetic gas exchange ability than the control under both P-sufficient and P-deficient conditions.


      PubDate: 2014-03-06T22:41:18Z
       
  • Cloning and characterization of a novel Athspr promoter specifically
           active in vascular tissue
    • Abstract: Publication date: Available online 3 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Liang Zhang , Tao Yang , Xiaoying Li , Hongyan Hao , Shengtao Xu , Wei Cheng , Yingli Sun , Chongying Wang
      The vascular system – xylem, phloem and the cambium – is essential for water supply, nutrient transport, and physical support in higher plants. Although it is known that vascular-specific gene expression is regulated by cis-acting regulatory sequences in promoters, it is largely unknown how many regulatory elements exist and what their roles are in promoters. To understand the regulatory elements of vascular-specific promoters and their roles in vascular development, a T-DNA insertion mutant showing delayed growth and diminished resistance to environmental stress was isolated using promoter trap strategy. The novel gene, Arabidopsis thaliana heat shock protein-related (Athspr), was cloned from Arabidopsis ecotype C24. Strong GUS (β-glucuronidase) staining in the original promoter trap line was found in the vascular tissues of all organs in the mutant. The Athspr promoter was cloned and fused with GUS and eGFP (enhanced green fluorescent protein) reporter genes to verify its vascular-specific expression in Arabidopsis. Further histochemical analysis in transgenic plants demonstrated a similar GUS expression pattern in the vascular tissues. In addition, ATHSPR-eGFP driven by Athspr promoter was observed in vascular bundles of the transgenic seedling roots. Finally, comparative analysis with promoter motifs from 37 genes involved in vascular development revealed that Athspr and all other promoters active in vascular tissues contained regulatory elements responding to phytohormones, light, biotic and abiotic stresses, as well as those regulating tissue-specific expression. These results demonstrated that the Athspr promoter has a vascular tissue-specific activity and Athspr may have multiple functions in vascular development and resistance against various stresses.


      PubDate: 2014-03-06T22:41:18Z
       
  • Overexpression of a stress-responsive MYB transcription factor of Poncirus
           trifoliata confers enhanced dehydration tolerance and increases polyamine
           biosynthesis
    • Abstract: Publication date: Available online 5 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Peipei Sun , Xiaofang Zhu , Xiaosan Huang , Ji-Hong Liu
      MYBs are an important family of transcription factors that play significant roles in plant development and stress response in plants. However, knowledge concerning the functions of MYBs in the non-model plants and the target genes is still limited. In this study, we isolated a stress-responsive R2R3-type MYB gene from trifoliate orange (Poncirus trifoliata (L.) Raf.), designated as PtsrMYB. PtsrMYB shares the highest degree of identity with AtMYB109. Subcellular localization using onion epidermal cells indicates that PtsrMYB is localized in the nucleus. Transcript levels of PtsrMYB were up-regulated by abiotic stresses such as dehydration, salt, cold and ABA treatment. Overexpression of PtsrMYB in tobacco confers enhanced dehydration tolerance, as indicated by less water loss, lower levels of malondialdehyde and reactive oxygen species. The transgenic tobacco lines displayed higher mRNA levels of two arginine decarboxylase (ADC) genes before and after dehydration treatment when compared with the wild type, concurrent with the greater levels of polyamines. Several MYB-recognizing cis-acting elements exist on the promoters of PtADC gene. Yeast one-hybrid assay demonstrated that PtsrMYB predominantly interact with two regions of the promoter, indicating the PtADC may be a target gene of PtsrMYB. Take together, PtsrMYB plays a positive role in dehydration tolerance, which may be, at least in part, due to the modulation of polyamine synthesis by regulating the ADC gene.


      PubDate: 2014-03-06T22:41:18Z
       
  • Dehydrin expression as a potential diagnostic tool for cold stress in
           white clover
    • Abstract: Publication date: Available online 1 March 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Irina Ivanova Vaseva , Iwona Anders , Bistra Yuperlieva-Mateeva , Rosa Nenkova , Anelia Kostadinova , Urs Feller
      Cold acclimation is important for crop survival in environments undergoing seasonal low temperatures. It involves the induction of defensive mechanisms including the accumulation of different cryoprotective molecules among which are dehydrins (DHN). Recently several sequences coding for dehydrins were identified in white clover (Trifolium repens). This work aimed to select the most responsive to cold stress DHN analogues in search for cold stress diagnostic markers. The assessment of dehydrin transcript accumulation via RT-PCR and immunodetection performed with three antibodies against the conserved K-, Y-, and S-segment allowed to outline different dehydrin types presented in the tested samples. Both analyses confirmed that YnKn dehydrins were underrepresented in the controls but exposure to low temperature specifically induced their accumulation. Strong immunosignals corresponding to 37- 40 kDa with antibodies against Y- and K-segment were revealed in cold-stressed leaves. Another ‘cold-specific’ band at position 52-55 kDa was documented on membranes probed with antibodies against K-segment. Real time RT-qPCR confirmed that low temperatures induced the accumulation of SKn and YnSKn transcripts in leaves and reduced their expression in roots. Results suggest that a YnKn dehydrin transcript with GenBank ID: KC247805 and the immunosignal at 37- 40 kDa, obtained with antibodies against Y- and K-segment are reliable markers for cold stress in white clover. The assessment of SKn (GenBank ID: EU846208) and YnSKn (GenBank ID: KC247804) transcript levels in leaves could serve as additional diagnostic tools.


      PubDate: 2014-03-02T06:06:40Z
       
  • “A maize spermine synthase 1 PEST sequence fused to the GUS reporter
           protein facilitates proteolytic degradation”
    • Abstract: Publication date: Available online 27 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Israel Maruri-López , Margarita Rodríguez-Kessler , Aída Araceli Rodríguez-Hernández , Alicia Becerra-Flora , Juan Elías Olivares-Grajales , Juan Francisco Jiménez-Bremont
      Polyamines are low molecular weight aliphatic compounds involved in various biochemical, cellular and physiological processes in all organisms. In plants, genes involved in polyamine biosynthesis and catabolism are regulated at transcriptional, translational, and posttranslational level. In this research, we focused on the characterization of a PEST sequence (rich in proline, glutamic acid, serine, and threonine) of the maize spermine synthase 1 (ZmSPMS1). To this aim, 123 bp encoding 40 amino acids of the C-terminal region of the ZmSPMS1 enzyme containing the PEST sequence were fused to the GUS reporter gene. This fusion was evaluated in Arabidopsis thaliana transgenic lines and onion monolayers transient expression system. The ZmSPMS1 PEST sequence leads to specific degradation of the GUS reporter protein. It is suggested that the 26S proteasome may be involved in GUS::PEST fusion degradation in both onion and Arabidopsis. The PEST sequences appear to be present in plant spermine synthases, mainly in monocots.


      PubDate: 2014-03-02T06:06:40Z
       
  • Hydrogen sulfide and cell signaling: Team player or referee'
    • Abstract: Publication date: Available online 25 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): J.T. Hancock , M. Whiteman
      Hydrogen sulfide (H2S) has been postulated to be the third gasotransmitter, and along with other reactive compounds such as reactive oxygen species (ROS) and nitric oxide (NO) it is thought to be a key signalling molecule. Enzymes which generate H2S, and remove it, have been characterised in both plants and animals and although it is inherently toxic to cells – inhibiting cytochrome oxidase for example – H2S is now being thought of as part of signal transduction pathways. But is it working as a signal in the sense usually seen for small signalling molecules, that is, produced when needed, perceived and leading to dedicated responses in cells' A look through the literature shows that H2S is involved in many stress responses, and in animals is implicated in the onset of many diseases, in both cases where ROS and NO are often involved. It is suggested here that H2S is not acting as a true signal, but through its interaction with NO and ROS metabolism is modulating such activity, keeping it in check unless strictly needed, and that H2S is acting as a referee to ensure NO and ROS metabolism is working properly.


      PubDate: 2014-03-02T06:06:40Z
       
  • Silicon improves seed germination and alleviates oxidative stress of bud
           seedlings in tomato under water deficit stress
    • Abstract: Publication date: Available online 22 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Yu Shi , Yi Zhang , Hejin Yao , Jiawen Wu , Hao Sun , Haijun Gong
      The beneficial effects of silicon on plant growth and development under drought have been widely reported. However, little information is available on the effects of silicon on seed germination under drought. In this work, the effects of exogenous silicon (0.5 mM) on the seed germination and tolerance performance of tomato (Solanum lycopersicum L.) bud seedlings under water deficit stress simulated by 10% (w/v) polyethylene glycol (PEG-6000) were investigated in four cultivars (‘Jinpengchaoguan’, ‘Zhongza No.9’, ‘Houpi L402’ and ‘Oubao318’). The results showed that the seed germination percentage was notably decreased in the four cultivars under water stress, and it was significantly improved by added silicon. Compared with the non-silicon treatment, silicon addition increased the activities of superoxide dismutase (SOD) and catalase (CAT), and decreased the production of superoxide anion (O2¯. ) and hydrogen peroxide (H2O2) in the radicles of bud seedlings under water stress. Addition of silicon decreased the total phenol concentrations in radicles under water stress, which might contribute to the decrease of peroxidase (POD) activity, as observed in the in vivo and in vitro experiments. The decrease of POD activity might contribute to a less accumulation of hydroxyl radical (·OH) under water stress. Silicon addition also decreased the concentrations of malondialdehyde (MDA) in the radicles under stress, indicating decreased lipid peroxidation. These results suggest that exogenous silicon could improve seed germination and alleviate oxidative stress to bud seedling of tomato by enhancing antioxidant defense. The positive effects of silicon observed in a silicon-excluder also suggest the active involvement of silicon in biochemical processes in plants.


      PubDate: 2014-02-24T22:21:49Z
       
  • Reduced chlorophyll biosynthesis in heterozygous barley magnesium
           chelatase mutants
    • Abstract: Publication date: Available online 17 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Ilka Braumann , Nils Stein , Mats Hansson
      Chlorophyll biosynthesis is initiated by magnesium chelatase, an enzyme composed of three proteins, which catalyzes the insertion of Mg2+ into protoporphyrin IX to produce Mg-protoporphyrin IX. In barley (Hordeum vulgare L.) the three proteins are encoded by Xantha-f, Xantha-g and Xantha-h. Two of the gene products, XanH and XanG, belong to the structurally conserved family of AAA+ proteins (ATPases associated with various cellular activities) and form a complex involving six subunits of each protein. The complex functions as an ATP-fueled motor of the magnesium chelatase that uses XanF as substrate, which is the catalytic subunit responsible for the insertion of Mg2+ into protoporphyrin IX. Previous studies have shown that semi-dominant Xantha-h mutations result in non-functional XanH subunits that participate in the formation of inactive AAA complexes. In the present study, we identify severe mutations in the barley mutants xantha-h.38, -h.56 and -h.57. A truncated form of the protein is seen in xantha-h.38, whereas no XanH is detected in xantha-h.56 and -h.57. Heterozygous mutants show a reduction in chlorophyll content by 14-18% suggesting a slight semi-dominance of xantha-h.38, -h.56 and -h.57, which otherwise have been regarded as recessive mutations.


      PubDate: 2014-02-20T05:14:12Z
       
  • Resveratrol and its combination with α-tocopherol mediate salt
           adaptation in citrus seedlings
    • Abstract: Publication date: Available online 20 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Zacharoula Kostopoulou , Ioannis Therios , Athanassios Molassiotis
      Resveratrol, a phytoalexin found in red wine, has the potential to impact a variety of human diseases but its function in plants exposed to stressful conditions is still unknown. In the present study the effect of exogenous application of resveratrol (Res), α-tocopherol (α-Toc) and their combination (Res + α-Toc) in salt adaptation of citrus seedlings was investigated. It was found that Res, α-Toc or Res + α-Toc treatments reduced NaCl-derived membrane permeability (EL), lipid peroxidation (MDA) and pigments degradation, whereas companied Res and α-Toc application also reduced H2O2 accumulation in leaves and restored the reduction of photosynthesis induced by NaCl. Application of Res under salinity retained Cl- in roots while Res + α-Toc reduced the translocation of Na+ and Cl- to leaves. Carbohydrates and proline, phenols, total ascorbic acid and glutathione were remarkably affected by NaCl as well as by chemical treatments in leaves and roots of citrus. NaCl treatment increased the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), glutathione reductase (GR), polyphenol oxidase (PPO) in leaves while SOD and POD activities were decreased in roots by this treatment. Also, Res, α-Toc or Res + α-Toc treatments displayed tissue specific activation or deactivation of the antioxidant enzymes. Overall, this work revealed a new functional role of Res in plants and provided evidence that the interplay of between Res and α-Toc is involved in salinity adaptation.


      PubDate: 2014-02-20T05:14:12Z
       
  • Glutathione transferase supergene family in tomato: salt stress-regulated
           expression of representative genes from distinct GST classes in plants
           primed with salicylic acid
    • Abstract: Publication date: Available online 19 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Jolán Csiszár , Edit Horváth , Zsolt Váry , Ágnes Gallé , Krisztina Bela , Szilvia Brunner , Irma Tari
      A family tree of the multifunctional proteins, glutathione transferases (GSTs, EC 2.5.1.18) was created in Solanum lycopersicum based on homology to known Arabidopsis GSTs. The involvement of selected SlGSTs was studied in salt stress response of tomato primed with salicylic acid (SA) or in un-primed plants by real-time qPCR. Selected tau GSTs (SlGSTU23, SlGSTU26) were up-regulated in the leaves, while GSTs from lambda, theta, dehydroascorbate reductase and zeta classes (SlGSTL3, SlGSTT2, SlDHAR5, SlGSTZ2) in the root tissues under salt stress. Priming with SA exhibited a concentration dependency; SA mitigated the salt stress injury and caused characteristic changes in the expression pattern of SlGSTs only at 10-4 M concentration. SlGSTF4 displayed a significant up-regulation in the leaves, while the abundance of SlGSTL3, SlGSTT2 and SlGSTZ2 transcripts were enhanced in the roots of plants primed with high SA concentration. Unexpectedly, under high salinity the SlDHAR2 expression decreased in primed roots as compared to the salt-stressed plants, however, the up-regulation of SlDHAR5 isoenzyme contributed to the maintenance of DHAR activity in roots primed with high SA. The members of lambda, theta and zeta class GSTs have a specific role in salt stress acclimation of tomato, while SlGSTU26 and SlGSTF4, the enzymes with high glutathione conjugating activity, characterize a successful priming in both roots and leaves. In contrast to low concentration, high SA concentration induced those GSTs in primed roots, which were up-regulated under salt stress. Our data indicate that induction of GSTs provide a flexible tool in maintaining redox homeostasis during unfavourable conditions.


      PubDate: 2014-02-20T05:14:12Z
       
 
 
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