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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]
  • 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
       
  • Effective microorganisms enhance the scavenging capacity of the
           ascorbate–glutathione cycle in common bean (Phaseolus vulgaris L.)
           plants grown in salty soils
    • Abstract: Publication date: Available online 5 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Neveen B. Talaat
      No information is available regarding effective microorganisms (EM) influence on the enzymatic and non-enzymatic antioxidant defence system involved in the ascorbate-glutathione cycle under saline conditions. Therefore, as a first approach, this article focuses on the contribution of EM to the scavenging capacity of the ascorbate–glutathione cycle in salt-stressed plants. It investigates some mechanisms underlying alleviation of salt toxicity by EM application. Phaseolus vulgaris cv. Nebraska plants were grown under non-saline or saline conditions (2.5 and 5.0 dS m-1) with and without EM application. Lipid peroxidation and H2O2 content were significantly increased in response to salinity, while they decreased with EM application in both stressed and non-stressed plants. Activities of ascorbate peroxidase (APX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2) increased under saline conditions; these increases were more significant in salt-stressed plants treated by EM. Activities of monodehydroascorbate reductase (MDHAR; EC 1.6.5.4) and dehydroascorbate reductase (DHAR; EC 1.8.5.1) decreased in response to salinity; however they were significantly increased in stressed plants treated with EM. Ascorbate and glutathione contents were increased with the increasing salt concentration; moreover they further increased in stressed plants treated with EM. Ratios of AsA/DHA and GSH/GSSG decreased under saline conditions, whereas they were significantly increased with EM treatment in presence or in absence of soil salinization. The EM treatment detoxified the stress generated by salinity and significantly improved plant growth and productivity. Enhancing the H2O2-scavenging capacity of the ascorbate–glutathione cycle in EM-treated plants may be an efficient mechanism to attenuate the activation of plant defences.


      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
       
  • Fine mapping of the lesion mimic and early senescence 1 (lmes1) in rice
           (Oryza Sativa)
    • Abstract: Publication date: Available online 5 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Zhi Li , Yingxin Zhang , Lin Liu , Qunen Liu , Zhenzhen Bi , Ning Yu , Shihua Cheng , Liyong Cao
      A novel rice mutant, lesion mimic and early senescence 1 (lmes1), was identified from an ethylmethane sulfonate (EMS) mutagenized 93-11 population. This mutant exhibited spontaneous disease-like lesions in the absence of pathogen attack at the beginning of the tillering stage. Moreover, at the booting stage, lmes1 mutants exhibited a significantly increased MDA but decreased chlorophyll content, soluble protein content and photosynthetic rate in the leaves, which are indicative of an early senescence phenotype. The lmes1 mutant was significantly more resistant than 93-11 against rice bacterial blight infection, which was consistent with a marked increase in the expression of resistance-related genes. Here, we employed a map-based cloning approach to finely map the lmes1 gene. In an initial mapping with 94 F2 individuals derived from a cross between the lmes1 mutant and Nipponbare, the lmes1 gene was located in a 10.6-cM region on the telomere of the long arm of chromosome 7 using simple sequence repeat (SSR) markers. To finely map lmes1, we derived two F2 populations with 940 individuals from two crosses between the lmes1 mutant and two japonica rice varieties, Nipponbare and 02428. Finally, the lmes1 gene was mapped to an 88-kb region between two newly developed inDel markers, Zl-3 and Zl-22, which harbored 15 ORFs.


      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
       
  • Arabidopsis thaliana peroxidases involved in lignin biosynthesis: in
           silico promoter analysis and hormonal regulation
    • Abstract: Publication date: Available online 3 April 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Joaquín Herrero , Alberto Esteban Carrasco , José Miguel Zapata
      Phytohormones such as auxins, cytokinins, and brassinosteroids, act by means of a signaling cascade of transcription factors of the families NAC, MYB, AP2 (APETALA2), MADS and class III HD (homeodomain) Zip, regulating secondary growth. When the hormonal regulation of Zinnia elegans peroxidase (ZePrx), an enzyme involved in lignin biosynthesis, was studied, it was found that this peroxidase is sensitive to a plethora of hormones which control xylem lignification. In a previous study we sought Arabidopsis thaliana homologues to ZePrx. Peroxidases 4, 52, 49 and 72 are the four peroxidases that fulfill the restrictive conditions that a peroxidase involved in lignification must have. In the present study, we focus our attention on hormonal regulation in order to establish the minimal structural and regulatory elements contained in the promoter region which an AtPrx involved in lignification must have. The results indicate that of the four peroxidases selected in our previous study, the one most likely to be homologous to ZePrx is AtPrx52. The results suggest that hormones such as auxins, cytokinins and BRs directly regulate AtPrx52, and that the AtPrx52 promoter may be the target of the set of transcription factors (NAC, MYB, AP2 and class I and III HD Zip) which are up-regulated by these hormones during secondary growth. In addition, the AtPrx52 promoter contains multiple copies of all the putative cis-elements (the ACGT box, the OCS box, the OPAQ box, the L1BX, the MYCL box and the W box) known to confer regulation by NO and H2O2.


      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
       
  • Editorial Board
    • Abstract: Publication date: April 2014
      Source:Plant Physiology and Biochemistry, Volume 77




      PubDate: 2014-03-17T00:12:12Z
       
  • 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
       
  • Arabidopsis thaliana mutant lpsi reveals impairment in the root responses
           to local phosphate availability
    • Abstract: Publication date: April 2014
      Source:Plant Physiology and Biochemistry, Volume 77
      Author(s): Athikkattuvalasu S. Karthikeyan , Ajay Jain , Vinay K. Nagarajan , Bhaskaran Sinilal , Shivendra V. Sahi , Kashchandra G. Raghothama
      Phosphate (Pi) deficiency triggers local Pi sensing-mediated inhibition of primary root growth and development of root hairs in Arabidopsis (Arabidopsis thaliana). Generation of activation-tagged T-DNA insertion pools of Arabidopsis expressing the luciferase gene (LUC) under high-affinity Pi transporter (Pht1;4) promoter, is an efficient approach for inducing genetic variations that are amenable for visual screening of aberrations in Pi deficiency responses. Putative mutants showing altered LUC expression during Pi deficiency were identified and screened for impairment in local Pi deficiency-mediated inhibition of primary root growth. An isolated mutant was analyzed for growth response, effects of Pi deprivation on Pi content, primary root growth, root hair development, and relative expression levels of Pi starvation-responsive (PSR) genes, and those implicated in starch metabolism and Fe and Zn homeostasis. Pi deprived local phosphate sensing impaired (lpsi) mutant showed impaired primary root growth and attenuated root hair development. Although relative expression levels of PSR genes were comparable, there were significant increases in relative expression levels of IRT1, BAM3 and BAM5 in Pi deprived roots of lpsi compared to those of the wild-type. Better understanding of molecular responses of plants to Pi deficiency or excess will help to develop suitable remediation strategies for soils with excess Pi, which has become an environmental concern. Hence, lpsi mutant will serve as a valuable tool in identifying molecular mechanisms governing adaptation of plants to Pi deficiency.


      PubDate: 2014-02-20T05:14:12Z
       
  • 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
       
  • Biochemical functions of the glutathione transferase supergene family of
           Larix kaempferi
    • Abstract: Publication date: Available online 14 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Qi Yang , Yan-Jing Liu , Qing-Yin Zeng
      Glutathione transferases (GSTs), which are ubiquitous in plants, play a major role in the detoxification of xenobiotics and oxidative stress metabolism. Due to their role in herbicide detoxification, previous studies of plant GSTs have mainly focused on agricultural plants. In contrast, functional information regarding gymnosperm GSTs is scarce. In this study, we cloned 27 full-length GST genes from the deciduous conifer Larix kaempferi, which is widely distributed across the cooler regions of the northern hemisphere. As with the angiosperm GST gene family, Larix GSTs are divided into eight classes, and tau class GSTs are the most numerous. Compared to the other seven classes of GSTs, Larix tau GST genes show substantially more variation in their expression patterns. The purified Larix GST proteins showed different substrate specificities, substrate activities, and kinetic characteristics. The pH and temperature profiles of purified Larix GST proteins showed broad optimum pH and temperature ranges for enzymatic activity, suggesting that Larix GSTs have evolutionary adaptations to various adverse environments. Taken together, this study provides comprehensive insight into the gymnosperm GST gene family.


      PubDate: 2014-02-15T07:18:19Z
       
  • Grape marc extract causes early perception events, defence reactions and
           hypersensitive response in cultured tobacco cells
    • Abstract: Publication date: Available online 6 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): R. Benouaret , E. Goujon , P. Goupil
      Grape marc extract (GME) showed elicitor activity on suspension-cultured cells of tobacco. The BY-2 cells reacted to GME (0.25% and 0.125%) with a long-sustained pH rise in their growth medium. Using EGTA or LaCl3, we showed that extracellular alkalinization depended on Ca2+ mobilization. The tobacco BY-2 cells challenged with GME promoted cell death and the upregulation of defence-related genes such as PR3, PAL and CCoAOMT. Cell death rate was quantified using an experimental calibrated Evans Blue assay. The GME-induced cell death was dose-dependent and occurred in 24 h. Longer exposure increased the extent of tobacco cell death. To investigate a potential hypersensitive reaction, we tested the effect of various inhibitors of protein synthesis (cycloheximide) and proteases (aprotinin, pepstatin and E-64) on GME-induced cell death. All these chemicals reduced GME-induced cell death rate in 30 min. Overall, our findings indicate that GME elicits early perception events, defence reactions and cell death requiring protein synthesis and proteases.
      Graphical abstract image

      PubDate: 2014-02-10T12:18:33Z
       
  • AtWNK9 is regulated by ABA and dehydration and is involved in drought
           tolerance in Arabidopsis
    • Abstract: Publication date: Available online 6 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Minmin Xie , Dan Wu , Guifang Duan , Liqun Wang , Reqing He , Xiushan Li , Dongying Tang , Xiaoying Zhao , Xuanming Liu
      WNK (with no lysine [K]) kinases play important regulatory roles in flowering, as well as salt and osmotic stress tolerance in plants. Here, we report that AtWNK9, a member of the Arabidopsis WNK gene family, was induced by exogenous abscisic acid (ABA) treatment and dehydration stress. Overexpression of AtWNK9 from the cauliflower mosaic virus 35S promoter in Arabidopsis resulted in increased sensitivity to ABA, strong inhibition of primary root elongation, increased proline accumulation, reduced stomatal aperture, and a reduced rate of water loss. In addition, plant survival under drought stress was improved compared to wild type. In contrast, a mutant with a T-DNA insertion in AtWNK9 showed reduced ABA sensitivity and an increased rate of water loss; further, it showed increased susceptibility to drought stress. The transcription of a number of ABA signaling components, including ABI1, ERA1, ABI3, and ABF3, was up-regulated in AtWNK9 transgenic plants and down-regulated in the wnk9 mutant in response to ABA. Some ABA-responsive and biosynthetic genes, as well as other drought-related genes, were altered at various levels in AtWNK9 transgenic plants and wnk9 mutants under dehydration stress. Overall, these findings suggest that AtWNK9 plays a positive role in ABA signaling and improves drought tolerance in transgenic Arabidopsis.


      PubDate: 2014-02-10T12:18:33Z
       
  • Effects of the sequence characteristics of miRNAs on multi-viral
           resistance mediated by single amiRNAs in transgenic tobacco
    • Abstract: Publication date: Available online 4 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Yun-Zhi Song , Quan-Jun Han , Fang Jiang , Run-Ze Sun , Zhi-Hang Fan , Chang-Xiang Zhu , Fu-Jiang Wen
      Artificial microRNA (amiRNA) has become the preferred viral defence that can be induced in plants. In this study, nine amiRNA target sites were selected that were based on the sequence characteristics of natural miRNAs in the cylindrical inclusion protein (CI), nuclear inclusion a protein (NIa), nuclear inclusion b protein (NIb), and coat protein (CP) genes of Potato virus Y (PVYN). These amiRNAs that exhibited high similarities to the sequences of PVYN and TEV-SD1 were considered. To study the effectiveness of gene silencing in amiRNA-mediated viral resistance, we constructed nine amiRNA plant expression vectors by replacing the functional sequences of miRNA319a precursors with our selected amiRNA sequences. These constructs were subsequently introduced to tobacco plants. A northern blot assay verified that the nine amiRNA plant expression vectors could successfully express amiRNAs in plants. The analysis of viral resistance demonstrated that these transgenic tobacco plants could effectively inhibit PVYN and TEV-SD1 viral infections. The amiRNA that targeted the NIb and CP genes displayed a higher silencing efficiency than did the amiRNAs targeted CI and NIa genes. Northern blot analysis demonstrated that silencing was induced by the original amiRNAs and could be bilaterally extended by the siRNA pathway. That is, the amiRNA and the secondary siRNA mediated the degradation of viral RNA together. Genetic analysis demonstrated that the trait for viral resistance in transgenic plants can be consistently inherited via a single copy of the transgenic sequence. Considering the correlation between the sequence characteristics and the activity of amiRNA, we concluded that a few mismatched bases between the amiRNA and the target sequence could be allowed, particularly the mismatched bases in the 3′ end of the amiRNA.


      PubDate: 2014-02-05T07:22:47Z
       
  • Model based analysis of transient fluorescence yield induced by actinic
           laser flashes in spinach leaves and cells of green alga Chlorella
           pyrenoidosa Chick
    • Abstract: Publication date: Available online 4 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): N.E. Belyaeva , F.-J. Schmitt , V.Z. Paschenko , G.Yu. Riznichenko , A.B. Rubin , G. Renger
      Measurements of Single Flash Induced Transient Fluorescence Yield (SFITFY) on spinach leaves and whole cells of green thermophilic alga Chlorella pyrenoidosa Chick were analyzed for electron transfer (ET) steps and coupled proton transfer (PT) on both, donor and acceptor sides of the reaction center (RC) of photosystem II (PS II). A specially developed PS II model (Belyaeva et al., 2008, 2011a) allowed the determination of ET steps that occur in a hierarchically ordered time scale from nanoseconds to several seconds. Our study demonstrates that our SFITFY data is consistent with the concept of the reduction of P680+• by YZ in both leaves and algae (studied on spinach leaves and cells of Chlorella pyrenoidosa Chick). The multiphasic P680+• reduction kinetics by YZ in PS II core complexes with high oxygen evolution capacity was seen in both algae and leaves. Model simulation to fit SFITFY curves for dark adapted species used here gives the rate constants to verify nanosecond kinetic stages of P680+• reduction by YZ in the redox state S1 of the WOC shown in Kühn et al. (2004). Then a sequence of relaxation steps in the redox state S1, outlined by Renger G. (2012), occurs in both algae and leaves as a similar non-adiabatic ET reactions. Coupled PT is discussed briefly to understand a rearrangement of hydrogen bond protons in the protein matrix of the WOC (Umena et al., 2011). On the other hand, present studies showed a slower reoxidation of reduced QA by QB in algal cells as compared with that in a leaf that might be regarded as a consequence of differences of spatial domains at the QB- site in leaves compared to algae. Our comparative study helped to correlate theory with experimental data for molecular photosynthetic mechanisms in thylakoid membranes.


      PubDate: 2014-02-05T07:22:47Z
       
  • Development- and cold-regulated accumulation of cold shock domain proteins
           in wheat
    • Abstract: Publication date: Available online 1 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Mariana Radkova , Pavel Vítámvás , Kentaro Sasaki , Ryozo Imai
      Cold shock domain (CSD) proteins, or Y-box proteins, are nucleic acid-binding proteins that are widely distributed from bacteria to higher plants and animals. Bacterial CSD proteins play an essential role in cold adaptation by destabilizing RNA secondary structures. WHEAT COLD SHOCK DOMAIN PROTEIN 1 (WCSP1) shares biochemical functions with bacterial CSD proteins and is possibly involved in cold adaptation. In this study, the temporal and spatial distribution of the wheat cold shock domain protein family (WCSPs) was serologically characterized with regard to plant development and cold adaptation. Four WCSP genes were identified through database analysis and were classified into three classes based on their molecular masses and protein domain structures. Class I (20 kD) and class II (23 kD) WCSPs demonstrated a clear pattern of accumulation in root and shoot meristematic tissues during vegetative growth. In response to cold, marked increases in WCSP levels were observed but the pattern of accumulation differed by tissue. Accumulation of WCSPs in crown tissue during cold acclimation was observed in the winter cultivar 'Chihoku' but not in the spring cultivar 'Haruyutaka'', suggesting a possible function for WCSPs in cold acclimation. During flower and seed development, protein levels of class I and class II WCSPs remained high. The class III WCSP (27 kD) was detected only during seed development. The highest level of class III WCSP accumulation was observed at the milky seed stage. Together, the results of this study provide a view of CSD protein accumulation throughout the life cycle of wheat and suggest that WCSPs function differentially in plant development and cold adaptation.


      PubDate: 2014-02-05T07:22:47Z
       
  • Hormone profiling and transcription analysis reveal a major role of ABA in
           tomato salt tolerance
    • Abstract: Publication date: Available online 2 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Rongchao Yang , Ting Yang , Haijun Zhang , Yan Qi , Yanxia Xing , Na Zhang , Ren Li , Sarah Weeda , Shuxin Ren , Bo Ouyang , Yang-Dong Guo
      The response and adaptation of plants to different environmental stresses are of great interest as they provide the key to understanding the mechanisms underlying stress tolerance. In this study, the changing patterns of four endogenous hormones and various physiological and biochemical parameters of both a salt-tolerant (LA2711) and a salt-sensitive (ZS-5) tomato cultivar were examined under salt stress and non-stress conditions. Additionally, the transcription of key genes in the abscisic acid (ABA) biosynthesis and metabolism were analyzed at different time points. The results indicated that gene expression responsible for ABA biosynthesis and metabolism coincided with the hormone level, and SlNCED1 and SlCYP707A3 may play major roles in the process. LA2711 performed superior to ZS-5 on various parameters, including seed germination, Na+ compartmentation, selective absorption of K+,and antioxidant enzymes activity. The difference in salt tolerance between the two genotypes could be attributed to the different levels of ABA due to differences in gene expression of key genes in ABA biosynthesis and metabolism. Although gibberellin, cytokinin and auxin were involved, our results indicated that ABA signaling plays a major role in tomato salt tolerance. As compared to ZS-5, LA2711 had a higher capability to selectively absorb and redistribute K+ and a higher tolerance to Na+ in young leaves, which may be the main physiological mechanisms of salt tolerance.


      PubDate: 2014-02-05T07:22:47Z
       
  • Salicylic acid and gentisic acid induce RNA silencing-related genes and
           plant resistance to RNA pathogens
    • Abstract: Publication date: Available online 2 February 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Laura Campos , Pablo Granell , Susana Tárraga , Pilar López-Gresa , Vicente Conejero , José María Bellés , Ismael Rodrigo , Purificación Lisón
      We have observed that treatments with salicylic acid (SA) or gentisic acid (GA) induced resistance to RNA pathogens such as ToMV and CEVd in tomato and Gynura auriantiaca, respectively. Accumulation of SA and GA has been found to occur in plants infected by these pathogens, thus pointing out a possible defence role of both molecules. To study the molecular basis of the observed induced resistance to RNA pathogens the induction of silencing-related genes by SA and GA was considered. For that purpose, we searched for tomato genes which were orthologous to those described in Arabidopsis thaliana, such as AtDCL1, AtDCL2, AtDCL4, AtRDR1, AtRDR2 and AtRDR6, and we tracked their induction in tomato along virus and viroid infections. We observed that CEVd significantly induced all these genes in tomato, with the exception of ToRDR6, being the induction of ToDCL4 the most outstanding. Regarding the ToMV asymptomatic infection, with the exception of ToRDR2, we observed a significant induction of all the indicated silencing-related genes, being ToDCL2 the most induced gene. Subsequently, we analyzed their transcriptional activation by SA and at the time when ToMV was inoculated on plants. ToDCL2, ToRDR1 and ToRDR2 were significantly induced by both SA and GA, whereas ToDCL1 was only induced by SA. Such an induction resulted more effective by SA treatment, which is in agreement with the stronger SA-induced resistance observed. Our results suggest that the observed delay in the RNA pathogen accumulation could be due to the pre-induction of RNA silencing-related genes by SA or GA.


      PubDate: 2014-02-05T07:22:47Z
       
  • Overexpression of a novel chrysanthemum SUPERMAN-like gene in tobacco
           affects lateral bud outgrowth and flower organ development
    • Abstract: Publication date: Available online 27 January 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Qing-Lin Liu , Ke-Dong Xu , Nan Ma , Liang-Jun Zhao , Lin Xi
      Previous studies have shown that the SUP genes play important roles in flower development and plant growth and morphogenesis. In this study, we isolated and characterized a SUPERMAN-like gene DgSZFP from chrysanthemum. DgSZFP contains one conserved Cys2/His2-type zinc finger motifs in the N-terminal region and an EAR-box in C-terminus. Its expression was significantly higher in nodes, flower buds, disc stamens, and petals than in the other tissues. Overexpression of DgSZFP in tobacco resulted in enhanced branching, reduced plant height, increased the width of petal tubes, produced the staminoid petals and petaloid stamens in flowers, and enhanced the seed weight and size. In addition, DgSZFP-overexpression tobacco plants accumulated high concentrations of cytokinin and chlorophyll. These results suggest that DgSZFP may be the candidate gene for regulating branching and floral organ development in chrysanthemum.


      PubDate: 2014-01-31T22:22:42Z
       
  • Cellular proton dynamics in Elodea canadensis leaves induced by cadmium
    • Abstract: Publication date: Available online 28 January 2014
      Source:Plant Physiology and Biochemistry
      Author(s): M. Tariq Javed , Sylvia Lindberg , Maria Greger
      Our earlier investigations showed that Elodea canadensis shoots, grown in the presence of cadmium (Cd), caused basification of the surrounding medium. The present study was aimed to examine the proton dynamics of the apoplastic, cytosolic and vacuolar regions of E. canadensis leaves upon Cd exposure and to establish possible linkage between cellular pH changes and the medium basification. The changes in cytosolic calcium [Ca2+]cyt was also investigated as the [Ca2+]cyt and [pH]cyt homeostasis are closely linked. The cellular H+ and Ca2+ concentrations were monitored by fluorescence microscopy and ion-specific fluorescent dyes. Cadmium concentration of leaf-cell walls was measured after plant cultivation at different fixed levels of starting pH. The protoplasts from E. canadensis leaves were isolated by use of a newly developed enzymatic method. Upon Cd addition, both cytosolic and vacuolar pH of leaf protoplasts increased with a concomitant rise in the cytosolic Ca2+ concentration. Time course studies revealed that changes in [Ca2+]cyt and [pH]cyt followed similar dynamics. Cadmium (0.5 μM) exposure decreased the apoplastic pH by 0.85 units. The maximum cell wall bound Cd-contents were obtained in plants grown at low starting pH. It is concluded that Cd treatment causes apoplastic acidosis in E. canadensis leaves associated with enhanced Cd binding to the cell walls and, consequently, reduced Cd influx into the cytosol.


      PubDate: 2014-01-31T22:22:42Z
       
  • Heterologous expression of the gourd E3 ubiquitin ligase gene LsRZF1
           compromises the drought stress tolerance in Arabidopsis thaliana
    • Abstract: Publication date: Available online 25 January 2014
      Source:Plant Physiology and Biochemistry
      Author(s): Ji-Hee Min , Hyun-Woo Ju , Kwang-Yeol Yang , Jung-Sung Chung , Baik-Ho Cho , Cheol Soo Kim
      Protein ubiquitination is one of the major regulatory processes used by eukaryotic cells. The ubiquitin E3 ligase acts as a main determinant of substrate specificity. However, the precise roles of E3 ligase in plants to drought stress are poorly understood. In this study, a gourd family (Lagenaria siceraria) ortholog of Arabidopsis thaliana RING Zinc Finger 1 (AtRZF1) gene, designated LsRZF1, was identified and characterized. LsRZF1 was reduced by abscisic acid (ABA), osmotic stress, and drought conditions. Compared to wild type, transgenic Arabidopsis plants ectopic expressing LsRZF1 were hypersensitive to ABA and osmotic stress during early seedling development, indicating that LsRZF1 negatively regulates drought-mediated control of early seedling development. Moreover, the ectopic expression of the LsRZF1 gene was very influential in drought sensitive parameters including proline content, water loss, and the expression of dehydration stress-related genes. Furthermore, ubiquitin E3 ligase activity and genetic data indicate that AtRZF1 and LsRZF1 function in similar pathway to control proline metabolism in Arabidopsis under drought condition. Together, these results suggest that the E3 ligase LsRZF1 is an important regulator of water deficit stress during early seedling development.


      PubDate: 2014-01-27T12:21:55Z
       
 
 
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