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Journal Cover Plant Physiology and Biochemistry
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0981-9428
     Published by Elsevier Homepage  [2563 journals]   [SJR: 0.996]   [H-I: 63]
  • Overexpression of a tobacco J-domain protein enhances drought tolerance in
           transgenic Arabidopsis
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Zongliang Xia , Xiaoquan Zhang , Junqi Li , Xinhong Su , Jianjun Liu
      DnaJ proteins constitute a DnaJ/Hsp40 family and are important regulators involved in diverse cellular functions. To date, the molecular mechanisms of DnaJ proteins involved in response to drought stress in plants are largely unknown. In this study, a putative DnaJ ortholog from Nicotiana tabacum (NtDnaJ1), which encodes a putative type-I J-protein, was isolated. The transcript levels of NtDnaJ1 were higher in aerial tissues and were markedly up-regulated by drought stress. Over-expression of NtDnaJ1 in Arabidopsis plants enhanced their tolerance to osmotic or drought stress. Quantitative determination of H2O2 accumulation has shown that H2O2 content increased in wild-type and transgenic seedlings under osmotic stress, but was significantly lower in both transgenic lines compared with the wild-type. Expression analysis of stress-responsive genes in NtDnaJ1-transgenic Arabidopsis revealed that there was significantly increased expression of genes involved in the ABA-dependent signaling pathway (AtRD20, AtRD22 and AtAREB2) and antioxidant genes (AtSOD1, AtSOD2, and AtCAT1). Collectively, these data demonstrate that NtDnaJ1 could be involved in drought stress response and its over-expression enhances drought tolerance possibly through regulating expression of stress-responsive genes. This study may facilitate our understandings of the biological roles of DnaJ protein-mediated abiotic stress in higher plants and accelerate genetic improvement of crop plants tolerant to environmental stresses.


      PubDate: 2014-08-15T20:21:07Z
       
  • α-Linolenic acid concentration and not wounding per se is the
           key regulator of octadecanoid (oxylipin) pathway activity in rice
           (Oryza sativa L.) leaves
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): John T. Christeller , Ivan Galis
      Using an in vitro system composed of crushed leaf tissues to simulate the wounding response in rice leaves, we established that synthesis of jasmonic acid (JA) and jasmonic acid-isoleucine (JA-Ile) can only occur in unwounded tissue and, in wounded tissue, that only the chloroplast-located section of the octadecanoid pathway is active, resulting in the accumulation of 12-oxo-phytodienoic acid (OPDA). We further showed that OPDA accumulation in vitro was inhibited by 90% using the general lipase inhibitor, tetrahydrolipstatin, indicating that production of α-linolenic acid was the rate-limiting step in octadecanoid pathway activity in rice following wounding and the enzyme capacity for an active pathway was already present. We confirmed this result by showing that added α-linolenic acid stimulated OPDA synthesis in vitro and stimulated OPDA, JA and JA-Ile synthesis in vivo in unwounded tissue. Thus, the response to wounding can be mimicked by the provision of free α-linolenic acid. Our results draw attention to the key importance of lipase activity in initiation of JA and JA-Ile biosynthesis and our lack of knowledge of the cognate lipase(s), lipase substrate identity and mechanism(s) of activation in wounded and unwounded tissue.
      Graphical abstract image

      PubDate: 2014-08-15T20:21:07Z
       
  • Salt stress mitigation by seed priming with UV-C in lettuce plants:
           Growth, antioxidant activity and phenolic compounds
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Chayma Ouhibi , Houneida Attia , Fedia Rebah , Najoua Msilini , Mohamed Chebbi , Jawad Aarrouf , Laurent Urban , Mokhtar Lachaal
      Seeds of Lactuca sativa L. ‘Romaine’ were subjected to priming treatments with UV-C radiation at 0.85 or 3.42 kJ m−2. Seedlings obtained from both primed (Pr) and non-primed (NPr) seeds were grown in an hydroponic culture system supplemented with 0 (control) or 100 mM NaCl. After 21 days of NaCl treatment, root and leaf biomass, root lengths, leaf numbers, and leaf surface area were measured. Ions (Na+ and K+) accumulation was determined in roots and leaves. Total phenolic compound and flavonoid concentrations, as well as antioxidant and antiradical activities were measured in L. sativa leaves. Salt stress resulted in a lower increase in fresh weight of roots and leaves, which was more pronounced in roots than in leaves, due to reduced root elongation, leaf number and leaf expansion, as well as leaf thickness. The lower increase in fresh weight was accompanied by a restriction in tissue hydration and K+ ion uptake, as well as an increase in Na+ ion concentrations in all organs. These effects were mitigated in plants from the UV-C primed seeds. The mitigating effect of UV-C was more pronounced at 0.85 than at 3.42 kJ m−2. Salt stress also resulted in an increase in total phenolic compounds and flavonoid concentrations and in the total antioxidant capacity in leaves. The highest diphenylpicrylhydrazyl radical (DPPH) scavenging activity was found in the leaves of plants from both Pr seeds. Our results suggest that plants grown from seed primed by exposure to moderate UV-C radiation exhibited a higher tolerance to salinity stress.


      PubDate: 2014-08-15T20:21:07Z
       
  • Characterization of two highly similar CBF/DREB1-like genes, PhCBF4a and
           PhCBF4b, in Populus hopeiensis
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Zeliang Wang , Jun Liu , Hongying Guo , Xiang He , Wanbo Wu , Jincheng Du , Zhiyi Zhang , Xinmin An
      The C-repeat binding factors (CBFs)/dehydration-responsive element-binding protein (DREBs) are a group of conserved transcription factors that play an important role in the response and adaptation to environmental stress in many plants. Two highly similar CBF/DREB1-like genes, PhCBF4a and PhCBF4b, were previously identified in Populus hopeiensis. In this paper, we describe the function of these proteins in detail in terms of abiotic stress tolerance. Phylogenic analysis suggests that PhCBF4a and PhCBF4b are expressed as two distinct alleles. Expression of both genes is induced mainly by dehydration, low-temperature, and high-salinity. Agroinfiltration experiments in tobacco leaves revealed differential transcriptional activation of the genes, likely driven by differences in their C-terminal regions. When constitutively expressed in Arabidopsis, PhCBF4a and PhCBF4b induced elevated expression of the CBF/DREB1 regulons without prior stimulus, resulting in dwarfism, delayed flowering, and greater drought tolerance compared with vector controls. These results demonstrate that PhCBF4a and PhCBF4b are functional transcriptional regulators involved in the response of P. hopeiensis to abiotic stresses.


      PubDate: 2014-08-15T20:21:07Z
       
  • Sulphate fertilization ameliorates long-term aluminum toxicity symptoms in
           perennial ryegrass (Lolium perenne)
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Cristian Wulff-Zottele , Holger Hesse , Joachim Fisahn , Mariusz Bromke , Hernán Vera-Villalobos , Yan Li , Falko Frenzel , Patrick Giavalisco , Alejandra Ribera-Fonseca , Ligia Zunino , Immcolata Caruso , Evelyn Stohmann , Maria de la Luz Mora
      Effects of the oxanion sulphate on plant aluminum (Al3+) detoxification mechanisms are not well understood. Therefore, holistic physiological and biochemical modifications induced by progressively increased doses of sulphate fertilization in the presence of long-term Al3+ stress were investigated in the aluminum sensitive perennial ryegrass (Lolium perenne L. cvJumbo). Plant growth inhibition induced by Al3+ was decreased in response to increasing doses of sulphate supply. Aluminum concentrations measured in roots of perennial ryegrass by atomic absorption spectrometry declined significantly with increasing sulphate concentrations. In parallel, we determined a rise of sulphur in shoots and roots of perennial ryegrass. Inclusion of up to 360 μM of sulphate enhanced cysteine and glutathione biosynthesis in Al3+ (1.07 μM) treated plants. This increase of thiol-containing compounds favored all modifications in the glutathione redox balance, declining lipid peroxidation, decreasing the activity of superoxide dismutase, and modifying the expression of proteins involved in the diminution of Al3+ toxicity in roots. In particular, proteome analysis by 1D-SDS-PAGE and LC-MS/MS allowed to identify up (e.g. vacuolar proton ATPase, proteosome β subunit, etc) and down (Glyoxilase I, Ascorbate peroxidase, etc.) regulated proteins induced by Al3+ toxicity symptoms in roots. Although, sulphate supply up to 480 μM caused a reduction in Al3+ toxicity symptoms, it was not as efficient as compared to 360 μM sulphate fertilization. These results suggest that sulphate fertilization ameliorates Al3+ toxicity responses in an intracellular specific manner within Lolium perenne.


      PubDate: 2014-08-12T20:13:45Z
       
  • The cowpea RING ubiquitin ligase VuDRIP interacts with transcription
           factor VuDREB2A for regulating abiotic stress responses
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Ayan Sadhukhan , Sanjib Kumar Panda , Lingaraj Sahoo
      Cowpea (Vigna unguiculata L. Walp) is an important grain legume cultivated in drought-prone parts of the world, having higher tolerance to heat and drought than many other crops. The transcription factor, Dehydration-Responsive Element-Binding protein 2A (DREB2A), controls expression of many genes involved in osmotic and heat stress responses of plants. In Arabidopsis, DREB2A-interacting proteins (DRIPs), which function as E3 ubiquitin ligases (EC 6.3.2.19), regulate the stability of DREB2A by targeting it for proteasome-mediated degradation. In this study, we cloned the cowpea ortholog of DRIP (VuDRIP) using PCR based methods. The 1614 bp long VuDRIP mRNA encoded a protein of 433 amino acids having a C3HC4-type Really Interesting New Gene (RING) domain in the N-terminus and a C-terminal conserved region, similar to Arabidopsis DRIP1 and DRIP2. We found VuDRIP up-regulation in response to various abiotic stresses and phytohormones. Using yeast (Saccharomyces cerevisae) two-hybrid analysis, VuDRIP was identified as a VuDREB2A-interacting protein. The results indicate negative regulation of VuDREB2A by ubiquitin ligases in cowpea similar to Arabidopsis along with their other unknown roles in stress and hormone signaling pathways.


      PubDate: 2014-08-04T19:42:17Z
       
  • Structural and functional characterization of proteinase inhibitors from
           seeds of Cajanus cajan (cv. ICP 7118)
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Marri Swathi , Vadthya Lokya , Vanka Swaroop , Nalini Mallikarjuna , Monica Kannan , Aparna Dutta-Gupta , Kollipara Padmasree
      Proteinase inhibitors (C11PI) from mature dry seeds of Cajanus cajan (cv. ICP 7118) were purified by chromatography which resulted in 87-fold purification and 7.9% yield. SDS-PAGE, matrix assisted laser desorption ionization time-of-flight (MALDI-TOF/TOF) mass spectrum and two-dimensional (2-D) gel electrophoresis together resolved that C11PI possessed molecular mass of 8385.682 Da and existed as isoinhibitors. However, several of these isoinhibitors exhibited self association tendency to form small oligomers. All the isoinhibitors resolved in Native-PAGE and 2-D gel electrophoresis showed inhibitory activity against bovine pancreatic trypsin and chymotrypsin as well as Achaea janata midgut trypsin-like proteases (AjPs), a devastating pest of castor plant. Partial sequences of isoinhibitor (pI 6.0) obtained from MALDI-TOF/TOF analysis and N-terminal sequencing showed 100% homology to Bowman-Birk Inhibitors (BBIs) of leguminous plants. C11PI showed non-competitive inhibition against trypsin and chymotrypsin. A marginal loss (<15%) in C11PI activity against trypsin at 80 °C and basic pH (12.0) was associated with concurrent changes in its far-UV CD spectra. Further, in vitro assays demonstrated that C11PI possessed significant inhibitory potential (IC50 of 78 ng) against AjPs. On the other hand, in vivo leaf coating assays demonstrated that C11PI caused significant mortality rate with concomitant reduction in body weight of both larvae and pupae, prolonged the duration of transition from larva to pupa along with formation of abnormal larval-pupal and pupal-adult intermediates. Being smaller peptides, it is possible to express C11PI in castor to protect them against its devastating pest A. janata.


      PubDate: 2014-08-04T19:42:17Z
       
  • Impacts of size and shape of silver nanoparticles on Arabidopsis plant
           growth and gene expression
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): You-yu Syu , Jui-Hung Hung , Jui-Chang Chen , Huey-wen Chuang
      Silver nanoparticles (AgNPs) are widely used as antibacterial nanomaterials; however, the environmental impacts of AgNPs remain uncertain. In this study, Arabidopsis physiological responses and gene expression were investigated after exposure to 3 different morphologies of AgNPs. The triangular (47 ± 7 nm) and spherical (8 ± 2 nm) AgNPs exhibited the lowest and highest degrees of antimicrobial activity, respectively. The AgNP-induced phenotypic alterations in Arabidopsis were correlated with nanoparticle morphology and size, in which the decahedral AgNPs (45 ± 5 nm) induced the highest degree of root growth promotion (RGP); however, the spherical AgNPs exhibited no RGP and induced the highest levels of anthocyanin accumulation in Arabidopsis seedlings. The decahedral and spherical AgNPs induced the lowest and highest levels of Cu/Zn superoxide dismutase (CSD2) accumulation, respectively. Moreover, 3 morphologies of AgNPs induced protein accumulations including cell-division-cycle kinase 2 (CDC2), protochlorophyllide oxidoreductase (POR), and fructose-1,6 bisphosphate aldolase (FBA). Regarding transcription, the AgNPs induced the gene expression of indoleacetic acid protein 8 (IAA8), 9-cis-epoxycarotenoid dioxygenase (NCED3), and dehydration-responsive RD22. Additional studies have shown that AgNPs antagonized the aminocyclopropane-1-carboxylic acid (ACC)-derived inhibition of root elongation in Arabidopsis seedlings, as well as reduced the expression of ACC synthase 7 (ACS7) and ACC oxidase 2 (ACO2), suggesting that AgNPs acted as inhibitors of ethylene (ET) perception and could interfere with ET biosynthesis. In conclusion, AgNPs induce ROS accumulation and root growth promotion in Arabidopsis. AgNPs activate Arabidopsis gene expression involved in cellular events, including cell proliferation, metabolism, and hormone signaling pathways.


      PubDate: 2014-08-04T19:42:17Z
       
  • Molecular cloning and expression analysis of tea plant aquaporin (AQP)
           gene family
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Chuan Yue , Hongli Cao , Lu Wang , Yanhua Zhou , Xinyuan Hao , Jianming Zeng , Xinchao Wang , Yajun Yang
      The role of aquaporin proteins (AQPs) has been extensively studied in plants. However, the information of AQPs in the tea plant (Camellia sinensis) is unclear. In this manuscript, we isolated 20 full-length AQP cDNAs from the tea plant, and these sequences were classified into five subfamilies. The genes in these subfamilies displayed differential expression profiles in the studied tissues. The CsAQP expression patterns correlated with flower development and opening (FDO) and bud endodormancy (BED). To better understand the short-term expression patterns of CsAQPs in response to abiotic stress, tea plants were treated with abscisic acid (ABA), cold, salt or drought. ABA treatment down-regulated the expression of various CsAQPs. Salt up-regulated the transcription of most CsAQP genes. Cold treatment resulted in a complicated transcriptional regulation pattern for various CsAQPs. The expression of CsAQPs, especially plasma membrane intrinsic proteins (CsPIPs) and tonoplast intrinsic proteins (CsTIPs), was induced by drought and remained relatively high after rehydration in leaves, whereas almost all the CsAQPs were repressed in roots. Our results highlighted the diversity of CsAQPs in the tea plant and demonstrated that the CsPIP and CsTIP genes play a vital role in the stress response as well as in FDO and BED. Furthermore, certain CsSIPs (small basic intrinsic proteins), CsNIPs (NOD26-like intrinsic proteins) and CsXIPs (X intrinsic proteins) may regulate BED and FDO.


      PubDate: 2014-08-04T19:42:17Z
       
  • Metabolomics deciphers the host resistance mechanisms in wheat cultivar
           Sumai-3, against trichothecene producing and non-producing isolates of
           Fusarium graminearum
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Raghavendra Gunnaiah , Ajjamada C. Kushalappa
      Fusarium head blight (FHB) of wheat, caused by Fusarium graminearum, reduces grain yield and contaminates grains with trichothecene mycotoxins. Host resistance to FHB is quantitatively inherited and more than 100 QTLs have been mapped, but the host resistance mechanisms are poorly understood. Non-targeted metabolic profiling was applied to elucidate the host resistance mechanisms to FHB spread through rachis of wheat cultivar Sumai-3 against both trichothecene producing and non-producing isolates of Fusarium graminearum. The accumulation of deoxynivalenol (DON) in Sumai-3 was low, however the resistance to spread was not due to its detoxification into DON-3-O-glucoside (D3G), as the proportion of total DON converted to D3G in the resistant was not significantly different from that in the susceptible cultivar Roblin. Instead, the resistance was considered to be due to the accumulation of resistance related (RR) metabolites belonging to the phenylpropanoid pathway that reduced pathogen advancement through increased host cell wall thickening and also reduced pathogen growth due to antifungal and/or antioxidant properties which, in turn, reduced subsequent trichothecene biosynthesis. The RR phenylpropanoids accumulated in Sumai-3 were mainly the preformed syringyl rich monolignols and their glucosides, which are precursors of lignin biosynthesis, as well as antimicrobial flavonoids. The resistant cultivar Sumai-3 inoculated with trichothecene producing F. graminearum not only accumulated less RR metabolites but also the abundance of many RR metabolites was lesser than in the trichothecene non-producing F. graminearum. This implies repression of host resistance mechanisms by trichothecenes/DON, which is a protein biosynthesis inhibitor. Enhancement of resistance in wheat against FHB can be exploited through stacking of candidate phenylpropanoid pathway genes.


      PubDate: 2014-07-30T19:22:26Z
       
  • The pH strongly influences the uranium-induced effects on the
           photosynthetic apparatus of Arabidopsis thaliana plants
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Eline Saenen , Nele Horemans , Nathalie Vanhoudt , Hildegarde Vandenhove , Geert Biermans , May Van Hees , Jean Wannijn , Jaco Vangronsveld , Ann Cuypers
      To study the impact of environmental uranium (U) contamination, effects should be analysed at different environmentally relevant pH levels as the speciation of U, and hence its toxicity, is strongly dependent on the pH. As photosynthesis is a major energy producing process in plants intimately connected to plant growth and known to be susceptible to metal stress, the effects of different U concentrations on photosynthesis in 18-day-old Arabidopsis thaliana (Columbia ecotype) are investigated at two contrasting pH levels, pH 4.5 and pH 7.5. At pH 4.5, U is highly taken up by the roots but is poorly translocated to the shoots, while at pH 7.5, less U is taken up but the translocation is higher. The lower U concentrations in the shoots at pH 4.5 are accompanied by a more reduced leaf growth as compared to pH 7.5. In addition, U does not influence the photosynthetic machinery at pH 7.5, while an optimization of the photosynthesis takes place after U exposure at pH 4.5. As such, more of the absorbed quanta are effectively used for photosynthesis accompanied by a decreased non-photochemical quenching and an increased electron transport rate. Since the enhanced photosynthesis at pH 4.5 is accompanied by a decreased growth, we suggest that the energy produced during photosynthesis is used for defence reactions against U-induced oxidative stress rather than for growth. As such, a high discrepancy was observed between the two pH levels, with an optimized photosynthetic apparatus at pH 4.5 and almost no effects at pH 7.5.


      PubDate: 2014-07-26T19:08:44Z
       
  • Impact of protective agents and drying methods on desiccation tolerance of
           Salix nigra L. seeds
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Patricio R. Santagapita , Helena Ott Schneider , Lina M. Agudelo-Laverde , M. Pilar Buera
      Willow seeds are classified as orthodox, but they show some recalcitrant characteristics, as they lose viability in a few weeks at room temperature. The aim of this work was to improve the desiccation tolerance of willow seeds (Salix nigra L.), as a model of sensitive materials to dehydration, through imbibition in solutions and later vacuum (VD) or freeze-drying (FD). Imbibition was conducted with 45% w/v trehalose or polyethylene glycol 400 –PEG– or water prior to dehydration treatments. Water- and especially trehalose-imbibed seeds subjected to VD showed better germination capability with respect to the freeze-dried ones. Water crystallization was mainly responsible for the great loss of capability germination observed in water- or trehalose-imbibed seeds subjected to FD. PEG behavior was better when seeds were FD instead of VD. DSC thermograms of seeds allowed to identify two thermal transitions corresponding to lipids melting and to proteins denaturation. This last transition reveals information about proteins state/functionality. Dehydration of control and PEG- or water-imbibed seeds affected proteins functionality leading to lower germinability. In the case of trehalose-imbibed seeds subjected to VD, proteins maintained their native state along dehydration, and the seeds showed a great germination capacity for all the water content range. Germinated seeds showed higher luminosity (L*), greenness (a*) and yellowness (b*) values than not-germinated seeds independently of the employed agent. Present work reveals that the presence of adequate protective agents as well the dehydration method were the main critical factors involved in willow seed desiccation tolerance.


      PubDate: 2014-07-26T19:08:44Z
       
  • Metabolic changes of Vitis vinifera berries and leaves exposed to Bordeaux
           mixture
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Viviana Martins , António Teixeira , Elias Bassil , Eduardo Blumwald , Hernâni Gerós
      Since the development of Bordeaux mixture in the late 1800's, copper-based fungicides have been widely used against grapevine (Vitis vinifera L.) diseases, mainly in organic but also in conventional viticulture; however their intensive use has raised phytotoxicity concerns. In this study, the composition of grape berries and leaves upon Bordeaux mixture treatment was investigated during the fructification season by a metabolomic approach. Four applications of Bordeaux mixture till 3 weeks before harvest were performed following the regular management practices of organic viticulture. Results showed that the copper-based treatment affected the content in sugars, organic acids, lipids and flavan-3-ols of grapes and leaves at specific developmental stages. Nonetheless, the levels of sucrose, glucose and fructose, and of tartaric and malic acids were not significantly affected in mature grapes. In contrast, a sharp decrease in free natural amino acids was observed, together with a reduction in protein content and in mineral nitrogen forms. The treatment with Bordeaux mixture increased by 7-fold the copper levels in tissue extracts from surface-washed mature berries.
      Graphical abstract image

      PubDate: 2014-07-26T19:08:44Z
       
  • Transcriptional regulation of genes encoding ABA metabolism enzymes during
           the fruit development and dehydration stress of pear 'Gold Nijisseiki'
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Shengjie Dai , Ping Li , Pei Chen , Qian Li , Yuelin Pei , Suihuan He , Yufei Sun , Ya Wang , Wenbin Kai , Bo Zhao , Yalan Liao , Ping Leng
      To investigate the contribution of abscisic acid (ABA) in pear 'Gold Nijisseiki' during fruit ripening and under dehydration stress, two cDNAs (PpNCED1 and PpNCED2) which encode 9-cis-epoxycarotenoid dioxygenase (NCED) (a key enzyme in ABA biosynthesis), two cDNAs (PpCYP707A1 and PpCYP707A2) which encode 8'-hydroxylase (a key enzyme in the oxidative catabolism of ABA), one cDNA (PpACS3) which encodes 1-aminocyclopropane-1-carboxylic acid (ACC), and one cDNA (PpACO1) which encodes ACC oxidase involved in ethylene biosynthesis were cloned from 'Gold Nijisseiki' fruit. In the pulp, peel and seed, expressions of PpNCED1 and PpNCED2 rose in two stages which corresponded with the increase of ABA levels. The expression of PpCYP707A1 dramatically declined after 60–90 days after full bloom (DAFB) in contrast to the changes of ABA levels during this period, while PpCYP707A2 stayed low during the whole development of fruit. Application of exogenous ABA at 100 DAFB increased the soluble sugar content and the ethylene release but significantly decreased the titratable acid and chlorophyll contents in fruits. When fruits harvested at 100 DAFB were stored in the laboratory (25 °C, 50% relative humidity), the ABA content and the expressions of PpNCED1/2 and PpCYP707A1 in the pulp, peel and seed increased significantly, while ethylene reached its highest value after the maximum peak of ABA accompanied with the expressions of PpACS3 and PpACO1. In sum the endogenous ABA may play an important role in the fruit ripening and dehydration of pear 'Gold Nijisseiki' and the ABA level was regulated mainly by the dynamics of PpNCED1, PpNCED2 and PpCYP707A1 at the transcriptional level.


      PubDate: 2014-07-26T19:08:44Z
       
  • Effect of calcium on strawberry fruit flavonoid pathway gene expression
           and anthocyanin accumulation
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Wenping Xu , Hui Peng , Tianbao Yang , Bruce Whitaker , Luhong Huang , Jianghao Sun , Pei Chen
      Two diploid woodland strawberry (Fragaria vesca) inbred lines, Ruegen F7-4 (red fruit-bearing) and YW5AF7 (yellow fruit-bearing) were used to study the regulation of anthocyanin biosynthesis in fruit. Ruegen F7-4 fruit had similar total phenolics and anthocyanin contents to commercial octoploid (F. × ananassa) cultivar Seascape, while YW5AF7 exhibited relatively low total phenolics content and no anthocyanin accumulation. Foliar spray of CaCl2 boosted fruit total phenolics content, especially anthocyanins, by more than 20% in both Seascape and RF7-4. Expression levels of almost all the flavonoid pathway genes were comparable in Ruegen F7-4 and YW5AF7 green-stage fruit. However, at the turning and ripe stages, key anthocyanin structural genes, including flavanone 3-hydroxylase (F3H1), dihydroflavonol 4-reductase (DFR2), anthocyanidin synthase (ANS1), and UDP-glucosyltransferase (UGT1), were highly expressed in Ruegen F7-4 compared with YW5AF7 fruit. Calcium treatment further stimulated the expression of those genes in Ruegen F7-4 fruit. Anthocyanins isolated from petioles of YW5AF7 and Ruegen F-7 had the same HPLC–DAD profile, which differed from that of Ruegen F-7 fruit anthocyanins. All the anthocyanin structural genes except FvUGT1 were detected in petioles of YW5AF7 and Ruegen F-7. Taken together, these results indicate that the “yellow” gene in YW5AF7 is a fruit specific regulatory gene(s) for anthocyanin biosynthesis. Calcium can enhance accumulation of anthocyanins and total phenolics in fruit possibly via upregulation of anthocyanin structural genes. Our results also suggest that the anthocyanin biosynthesis machinery in petioles is different from that in fruit.


      PubDate: 2014-07-26T19:08:44Z
       
  • Identification of differentially expressed genes potentially involved in
           the tolerance of Lotus tenuis to long-term alkaline stress
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Rosalía Cristina Paz , Rubén Anibal Rocco , Juan Francisco Jiménez-Bremont , Margarita Rodríguez-Kessler , Alicia Becerra-Flora , Ana Bernardina Menéndez , Oscar Adolfo Ruíz
      Soil alkalinity is one of the most serious agricultural problems limiting crop yields. The legume Lotus tenuis is an important forage acknowledged by its ability to naturally grow in alkaline soils. To gain insight into the molecular responses that are activated by alkalinity in L. tenuis plants, subtractive cDNA libraries were generated from leaves and roots of these plants. Total RNAs of non-stressed plants (pH 5.8; E.C. 1.2), and plants stressed by the addition of 10 mM of NaHCO3 (pH 9.0; E.C. 1.9), were used as source of the driver and the tester samples, respectively. RNA samples were collected after 14 and 28 days of treatment. A total of 158 unigenes from leaves and 92 unigenes from roots were obtained and classified into 11 functional categories. Unigenes from these categories (4 for leaves and 8 for roots), that were related with nutrient metabolism and oxidative stress relief were selected, and their differential expression analyzed by qRT-PCR. These genes were found to be differentially expressed in a time dependent manner in L. tenuis during the alkaline stress application. Data generated from this study will contribute to the understanding of the general molecular mechanisms associated to plant tolerance under long-term alkaline stress in plants.


      PubDate: 2014-07-26T19:08:44Z
       
  • Differential response of Arabidopsis leaves and roots to cadmium:
           Glutathione-related chelating capacity vs antioxidant capacity
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Marijke Jozefczak , Els Keunen , Henk Schat , Mattijs Bliek , Luis E. Hernández , Robert Carleer , Tony Remans , Sacha Bohler , Jaco Vangronsveld , Ann Cuypers
      This study aims to uncover the spatiotemporal involvement of glutathione (GSH) in two major mechanisms of cadmium (Cd)-induced detoxification (i.e. chelation and antioxidative defence). A kinetic study was conducted on hydroponically grown Arabidopsis thaliana (L. Heyhn) to gain insight into the early events after exposure to Cd. Cadmium detoxification was investigated at different levels, including gene transcripts, enzyme activities and metabolite content. Data indicate a time-dependent response both within roots and between plant organs. Early on in roots, GSH was preferentially allocated to phytochelatin (PC) synthesis destined for Cd chelation. This led to decreased GSH levels, without alternative pathways activated to complement GSH's antioxidative functions. After one day however, multiple antioxidative pathways increased including superoxide dismutase (SOD), ascorbate (AsA) and catalase (CAT) to ensure efficient neutralization of Cd-induced reactive oxygen species (ROS). As a consequence of Cd retention and detoxification in roots, a delayed response occurred in leaves. Together with high leaf thiol contents and possibly signalling responses from the roots, the leaves were protected, allowing them sufficient time to activate their defence mechanisms.


      PubDate: 2014-07-26T19:08:44Z
       
  • Antioxidant defence in UV-irradiated tobacco leaves is centred on
           hydrogen-peroxide neutralization
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Petra Majer , Gyula Czégény , Györgyi Sándor , Philip J. Dix , Éva Hideg
      Greenhouse grown tobacco (Nicotiana tabacum L. cv. Petit Havana) plants were exposed to supplemental UV centred at 318 nm and corresponding to 13.6 kJ m−2 d−1 biologically effective UV-B (280–315 nm) radiation. After 6 days this treatment decreased photosynthesis by 30%. Leaves responded by a large increase in UV-absorbing pigment content and antioxidant capacities. UV-stimulated defence against ROS was strongest in chloroplasts, since activities of plastid enzymes FeSOD and APX had larger relative increases than other, non-plastid specific SODs or peroxidases. In addition, non-enzymatic defence against hydroxyl radicals was doubled in UV treated leaves as compared to controls. In UV treated leaves, the extent of activation of ROS neutralizing capacities followed a peroxidases > hydroxyl-radical neutralization > SOD order. These results suggest that highly effective hydrogen peroxide neutralization is the focal point of surviving UV-inducible oxidative stress and argue against a direct signalling role of hydrogen peroxide in maintaining adaptation to UV, at least in laboratory experiments.


      PubDate: 2014-07-26T19:08:44Z
       
  • Leaf ion homeostasis and plasma membrane H+-ATPase activity in Vicia faba
           change after extra calcium and potassium supply under salinity
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Sherif H. Morgan , Pooja Jha Maity , Christoph-Martin Geilfus , Sylvia Lindberg , Karl Hermann Mühling
      Salt stress in plants impacts apoplastic ion activities and cytosolic ionic homeostasis. The ameliorating effects exerted by calcium or potassium on compartmentation of ions in leaves under salinity are not fully understood. To clarify how calcium or potassium supply could ameliorate ion homeostasis and ATPase activities under salinity, 5 mM CaSO4 or 10 mM K2SO4 were added with, or without, 100 mM NaCl for 7 d and 21 d to Vicia faba grown in hydroponics. The apoplastic pH was detected with Oregon Green dextran dye in intact second-uppermost leaves by microscopy-based ratio imaging. The cytosolic Ca2+, Na+, K+ activities and pH were detected in protoplasts loaded with the acetoxy methyl-esters of Fura-2, SBFI, PBFI and BCECF, respectively, using epi-fluorescence microscopy. Furthermore, total Ca2+, Na+, K+ concentrations and growth parameters were investigated. The ATPase hydrolyzing activity increased with time, but decreased after long salinity treatment. The activity largely increased in calcium-treated plants, but was depressed in potassium-treated plants after 7 d. The calcium supply increased Vmax, and the ATPase activity increased with salinity in a non-competitive way for 7 d and 21 d. The potassium supply instead decreased activity competitively with Na+, after 21 d of salinity, with different effects on Km and Vmax. The confirmed higher ATPase activity was related with apoplast acidification, cytosol alkalinization and low cytosolic [Na+], and thus, might be an explanation why extra calcium improved shoot and leaf growth.


      PubDate: 2014-07-26T19:08:44Z
       
  • Salinity and drought tolerant OsACA6 enhances cold tolerance in transgenic
           tobacco by interacting with stress-inducible proteins
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Kazi Md. Kamrul Huda , Mst. Sufara Akhter Banu , Sandep Yadav , Ranjan Kumar Sahoo , Renu Tuteja , Narendra Tuteja
      Plant Ca2+ATPases regulate many signalling pathways which are important for plant growth, development and abiotic stress responses. Our previous work identified that overexpression of OsACA6 confers salinity and drought tolerance in tobacco. In the present work we report, the function of OsACA6 in cold stress tolerance in transgenic tobacco plants. The expression of OsACA6 was induced by cold stress. The promoter-GUS fusion analyses in the different tissues of transgenic tobacoco confirmed that OsACA6 promoter is cold stress-inducible. Transgenic tobacco plants overexpressing OsACA6 exhibited cold tolerance compared to the wild type (WT) controls. The enhanced tolerance was confirmed by phenotypic analyses as well as by measuring germination, survival rate, chlorophyll content, cell membrane stability, malondialdehyde and proline content. Compared to the WT, the expression of catalase, ascorbate peroxidase and superoxide dismutase increased in the OsACA6 overexpressing plants, which was inversely correlated with the levels of H2O2 in the transgenic lines. We also identified interacting proteins of OsACA6 by using yeast two-hybrid screening assay. Most of the interacting partners of OsACA6 are associated with the widespread biological processes including plant growth, development, signalling and stress adaptation. Furthermore, we also confirmed that OsACA6 is able to self-interact. Overall, these results suggest that OsACA6 plays an important role in cold tolerance at least in part, by regulating antioxidants-mediated removal of reactive oxygen species or by interacting with different calcium signal decoders including calmodulin-like proteins (CaM) calcium/calmodulin dependent protein kinases (CDPKs) and receptor-like protein kinases (RLKs).


      PubDate: 2014-07-26T19:08:44Z
       
  • Modulation of auxin content in Arabidopsis confers improved drought stress
           resistance
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Haitao Shi , Li Chen , Tiantian Ye , Xiaodong Liu , Kejian Ding , Zhulong Chan
      Auxin is a well-known plant phytohormone that is involved in multiple plant growth processes and stress responses. In this study, auxin response was significantly modulated under drought stress condition. The iaaM-OX transgenic lines with higher endogenous indole-3-acetic acid (IAA) level and IAA pre-treated wild type (WT) plants exhibited enhanced drought stress resistance, while the yuc1yuc2yuc6 triple mutants with lower endogenous IAA level showed decreased stress resistance in comparison to non-treated WT plants. Additionally, endogenous and exogenous auxin positively modulated the expression levels of multiple abiotic stress-related genes (RAB18, RD22, RD29A, RD29B, DREB2A, and DREB2B), and positively affected reactive oxygen species (ROS) metabolism and underlying antioxidant enzyme activities. Moreover, auxin significantly modulated some carbon metabolites including amino acids, organic acids, sugars, sugar alcohols and aromatic amines. Notably, endogenous and exogenous auxin positively modulated root architecture especially the lateral root number. Taken together, this study demonstrated that auxin might participate in the positive regulation of drought stress resistance, through regulation of root architecture, ABA-responsive genes expression, ROS metabolism, and metabolic homeostasis, at least partially.


      PubDate: 2014-07-26T19:08:44Z
       
  • Comparative proteomic responses of two bermudagrass (Cynodon dactylon (L).
           Pers.) varieties contrasting in drought stress resistance
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Haitao Shi , Tiantian Ye , Zhulong Chan
      Drought (water-deficit) stress is a serious environmental problem in plant growth and cultivation. As one of widely cultivated warm-season turfgrass, bermudagrass (Cynodon dactylon (L). Pers.) exhibits drastic natural variation in the drought stress resistance in leaves and stems of different varieties. In this study, proteomic analysis was performed to identify drought-responsive proteins in both leaves and stems of two bermudagrass varieties contrasting in drought stress resistance, including drought sensitive variety (Yukon) and drought tolerant variety (Tifgreen). Through comparative proteomic analysis, 39 proteins with significantly changed abundance were identified, including 3 commonly increased and 2 decreased proteins by drought stress in leaves and stems of Yukon and Tifgreen varieties, 2 differentially regulated proteins in leaves and stems of two varieties after drought treatment, 23 proteins increased by drought stress in Yukon variety and constitutively expressed in Tifgreen variety, and other 3 differentially expressed proteins under control and drought stress conditions. Among them, proteins involved in photosynthesis (PS), glycolysis, N-metabolism, tricarboxylicacid (TCA) and redox pathways were largely enriched, which might be contributed to the natural variation of drought resistance between Yukon and Tifgreen varieties. These studies provide new insights to understand the molecular mechanism underlying bermudagrass response to drought stress.


      PubDate: 2014-07-26T19:08:44Z
       
  • Photosynthetic changes of flag leaves during senescence stage in super
           high-yield hybrid rice LYPJ grown in field condition
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Yuwen Wang , Jingjing Zhang , Jing Yu , Xiaohan Jiang , Lingang Sun , Min Wu , Guoxiang Chen , Chuangen Lv
      Photosynthetic activities and thylakoid membrane protein patterns as well as the ultrastructure of chloroplasts in flag leaves were investigated during the senescence processes in high-yield hybrid rice LYPJ under field condition. The earlier decrease of PS I activity than PS II in LYPJ was primarily due to the significant degradation of PS I chlorophyll–protein complex. The degradation rate for each chlorophyll–protein complex was different and the order for the stability of thylakoid membrane complexes during flag leaf senescence in rice LYPJ was: LHCII > OEC > PSII core antenna > PSII core > PSI core > LHCI, which was partly supported by the BN-PAGE gel combined with immunoblot analysis. A decrease in the chlorophyll a/b ratio at the senescence stage was observed to coincide with stability of the LHCII subunits. Ultrastructural investigations revealed that the chloroplasts have large loosen stacking grana without interconnecting stroma thylakoids during the senescence processes. It was hypothesized that the stability of grana thylakoids harboring the major LHCII under high radiation condition in summer might played a key role in the dissipation of excess light energy. This alternative strategy would protect photosynthetic apparatus from photodamage and might be causally related to the high yield of this rice cultivar.


      PubDate: 2014-07-26T19:08:44Z
       
  • Is DNA methylation modulated by wounding-induced oxidative burst in
           maize?
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Elżbieta Lewandowska-Gnatowska , Lidia Polkowska-Kowalczyk , Jadwiga Szczegielniak , Mirosława Barciszewska , Jan Barciszewski , Grażyna Muszyńska
      Plants respond to environmental changes by modifying gene expression. One of the mechanisms regulating gene expression is methylation of cytosine to 5-methylcytosine (m5C) which modulates gene expression by changing chromatin structure. Methylation/demethylation processes affect genes that are controlled upon environmental stresses. Here, on account of the regulatory role of m5C, we evaluate the content of m5C in DNA from normal and wound-damaged maize leaves. Wounding leads to a transient decrease of the global DNA methylation level ca 20–30% 1 h after the treatment followed by a return to the initial level within the next hours. Similar results were obtained using of radio-labeled nucleotides separated by Thin Layer Chromatography (TLC) or using m5C-specific Enzyme-Linked Immunosorbent Assay (ELISA). Wounding induced in maize leaves a two-step oxidative stress, an early one just after wounding and the second two hours later. It coincides with the transient changes of the cytosine methylation level. In the stress-inducible maize calcium-dependent protein kinase ZmCPK11 gene wounding transiently reduced methylation of cytosines 100 and 126 in the first exon.


      PubDate: 2014-07-26T19:08:44Z
       
  • Improvement of nitrogen accumulation and metabolism in rice (Oryza sativa
           L.) by the endophyte Phomopsis liquidambari
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Bo Yang , Hai-Yan Ma , Xiao-Mi Wang , Yong Jia , Jing Hu , Xia Li , Chuan-Chao Dai
      The fungal endophyte Phomopsis liquidambari can enhance nitrogen (N) uptake and metabolism of rice plants under hydroponic conditions. To investigate the effects of P. liquidambari on N accumulation and metabolism in rice (Oryza sativa L.) under field conditions during the entire growing season (S1, the seedling stage; S2, the tillering stage; S3, the heading stage; S4, the ripening stage), we utilized pot experiments to examine metabolic and physiological levels in both shoot and root tissues of rice, with endophyte (E+) and without endophyte (E−), in response to three different N levels. We found that under low-N treatment, P. liquidambari symbiosis increased the rice yield and N use efficiency by 12% and by 11.59%, respectively; that the total N contents in E+ rice plants at the four growth stages were separately increased by 29.05%, 14.65%, 21.06% and 18.38%, respectively; and that the activities of nitrate reductase and glutamine synthetase in E+ rice roots and shoots were significantly increased by fungal infection during the S1 to S3 stages. Moreover, P. liquidambari significantly increased the free NH4 +, NO3 -, amino acid and soluble protein contents in infected rice tissues under low-N treatment during the S1 to S3 stages. The obtained results offer novel data concerning the systemic changes induced by P. liquidambari in rice during the entire growth period and confirm the hypothesis that the rice–P. liquidambari interaction improved the N accumulation and metabolism of rice plants, consequently increasing rice N utilization in nutrient-limited soil.


      PubDate: 2014-07-26T19:08:44Z
       
  • Apoplastic antioxidant enzyme responses to chronic free-air ozone exposure
           in two different ozone-sensitive wheat cultivars
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Junli Wang , Qing Zeng , Jianguo Zhu , Chen Chen , Gang Liu , Haoye Tang
      The effects of elevated ozone concentrations [O3] on two different ozone-sensitive wheat (Triticum aestivum L.) cultivars [Yangmai16 (Y16) and Yannong19 (Y19)] were investigated to determine the different apoplastic antioxidant mechanisms under O3-FACE (free-air controlled enrichment) condition. The results indicated that elevated [O3] (1.5 × ambient [O3]) induced increases in the production of superoxide anion ( O 2 − ), hydroxyl radical (HO), hydrogen peroxide (H2O2) and lipid peroxidation, and these results were more pronounced in the apoplasts of Y19 than in those of Y16. Apoplastic antioxidant enzymes were developmentally regulated and the effect of elevated [O3] depended on the developmental stage of wheat for both cultivars. In cultivar Y19, continuous O3 stress induced a decrease in the activity of apoplastic superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC 1.11.1.7) and ascorbate peroxidase (APX; EC 1.11.1.11) in the later growing stages, indicating Y19 appears to be the more sensitive cultivar and is prone to oxidative stress. The strategic response of antioxidant enzymes activities by Y16 in four different plant development stages (booting, flowering, filling and ripening) resulted in O3 stress-induced antioxidant defense responses, which indicated its higher tolerance to O3 stress. The same patterns of activity of apoplastic SOD and APX isozymes were observed in both Y16 and Y19 cultivars, while POD isozymes differed by cultivar in terms of the pattern of bands. The results of the present study show that O3 tolerance can be improved by regulating apoplastic ROS metabolism through the responses of apoplastic antioxidant enzymes to O3 stress in different plant development stages.


      PubDate: 2014-07-26T19:08:44Z
       
  • Contribution of polyamines and other related metabolites to the
           maintenance of zucchini fruit quality during cold storage
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Francisco Palma , Fátima Carvajal , Manuel Jamilena , Dolores Garrido
      In order to investigate the contribution of polyamines and related amino acids in the maintenance of zucchini fruit quality during cold storage, two varieties of Cucurbita pepo with different degrees of chilling tolerance were used, Natura (more tolerant) and Sinatra (moresensitive). After harvest, free putrescine levels decreased during storage at 20 °C, whereas in fruit kept at 4 °C this polyamine accumulated in both varieties, but with higher levels in the sensitive variety (Sinatra). This behavior suggests that putrescine is accumulated as a response to low temperature in zucchini fruit by stress-induced chilling injury, and not due to the postharvest storage itself. ADC activity responds quickly to chilling but sharply decreases after 14 days, whereas its expression remains high in both varieties. ODC activity takes over when the cold stress is relatively severe, as this activity was found to be much higher in Sinatra. ODCexpression also correlated with ODC activity. DAO activity increased in Natura fruit, and conversely decreased in Sinatra fruit during storage at 4 °C, whereas the proline content was higher in Natura and lower in Sinatra. Therefore, we suggest that putrescine degradation and proline accumulation contribute to the acquisition of chilling tolerance in zucchini fruit. GABA content decreased in both varieties, with a greater reduction in Natura fruit and less in Sinatra fruit. In addition, GABA transaminase showed a higher activity in Natura fruit than in Sinatra fruit during cold storage, suggesting that GABA catabolism could be involved in the tolerance to postharvest cold storage in zucchini fruit.


      PubDate: 2014-07-26T19:08:44Z
       
  • Identification of caleosin and two oleosin isoforms in oil bodies of pine
           megagametophytes
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Buntora Pasaribu , Tse-yu Chung , Chii-Shiarng Chen , Song-liang Wang , Pei-Luen Jiang , Jason T.C. Tzen
      Numerous oil bodies of 0.2–2 μm occupied approximately 80% of intracellular space in mature pine (Pinus massoniana) megagametophytes. They were stably isolated and found to comprise mostly triacylglycerols as examined by thin layer chromatography analysis and confirmed by both Nile red and BODIPY stainings. Fatty acids released from the triacylglycerols of pine oil bodies were mainly unsaturated, including linoleic acid (60%), adrenic acid (12.3%) and vaccenic acid (9.7%). Proteins extracted from pine oil bodies were subjected to immunological cross-recognition, and the results showed that three proteins of 28, 16 and 14 kDa were detected by antibodies against sesame seed caleosin, sesame oleosin-L and lily pollen oleosin-P, respectively. Complete cDNA fragments encoding these three pine oil-body proteins, tentatively named caleosin, oleosin-L and oleosin-G, were obtained by PCR cloning and further confirmed by mass spectrometric analysis. Consistently, phylogenetic tree analyses showed that pine caleosin was closely-related to the caleosin of cycad megagametophyte among known caleosin sequences. While pine oleosin-L was found clustered with seed oleosin isoforms of angiosperm species, oleosin-G was distinctively grouped with the oleosin-P of lily pollen. The oleosin-G identified in pine megagametophytes seems to represent a new class of seed oleosin isoform evolutionarily close to the pollen oleosin-P.


      PubDate: 2014-07-26T19:08:44Z
       
  • Hormonal dynamics during recovery from drought in two Eucalyptus globulus
           genotypes: From root to leaf
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Barbara Correia , Marta Pintó-Marijuan , Bruno B. Castro , Ricard Brossa , Marta López-Carbonell , Glória Pinto
      Drought is a limiting environmental stress that represents a growing constraint to the forestry sector. Eucalyptus globulus is a widely planted coppice species, which capacity to cope with water deficit has already been described. However, the capacity of this species to recover is still poorly understood. In this study, we aimed to investigate the changes in abscisic acid (ABA), ABA-glucose ester (ABA-GE) and jasmonic acid (JA) content in leaves, xylem sap and roots of two genotypes (AL-10 and AL-18) during rewatering (2 h, 4 h, 24 h, and 168 h), after a drought stress period (0 h). We wished to clarify the role of these hormones in the recovery from drought and to determine whether these hormonal relations were related to specific genotype metabolisms. Our results showed that drought caused an increased in ABA and ABA-GE levels in all analysed plant parts, while JA content decreased in leaves, increased in xylem sap and did not change in roots. Some of these responses were genotype specific. During rewatering, ABA and ABA-GE content decreased in both genotypes and all plant parts, but at different time scales, and JA levels did not greatly change. Again, the genotypes responded differently. Altogether, our results characterised the response pattern of clone AL-10 as more responsive and defended that leaf should be used in preliminary screening methods of stress tolerance. The hormonal dynamics were related to the previously documented responses of these genotypes and sustain further physiological and molecular studies of water stress in this and other tree species.


      PubDate: 2014-07-26T19:08:44Z
       
  • Vacuolar biogenesis and aquaporin expression at early germination of broad
           bean seeds
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Galina V. Novikova , Colette Tournaire-Roux , Irina A. Sinkevich , Snejana V. Lityagina , Christophe Maurel , Natalie Obroucheva
      A key event in seed germination is water uptake-mediated growth initiation in embryonic axes. Vicia faba var. minor (broad bean) seeds were used for studying cell growth, vacuolar biogenesis, expression and function of tonoplast water channel proteins (aquaporins) in embryonic axes during seed imbibition, radicle emergence and growth. Hypocotyl and radicle basal cells showed vacuole restoration from protein storage vacuoles, whereas de novo vacuole formation from provacuoles was observed in cells newly produced by root meristem. cDNA fragments of seven novel aquaporin isoforms including five Tonoplast Intrinsic Proteins (TIP) from three sub-types were amplified by PCR. The expression was probed using q-RT-PCR and when possible with isoform-specific antibodies. Decreased expression of TIP3s was associated to the transformation of protein storage vacuoles to vacuoles, whereas enhanced expression of a TIP2 homologue was closely linked to the fast cell elongation. Water channel functioning checked by inhibitory test with mercuric chloride showed closed water channels prior to growth initiation and active water transport into elongating cells. The data point to a crucial role of tonoplast aquaporins during germination, especially during growth of embryonic axes, due to accelerated water uptake and vacuole enlargement resulting in rapid cell elongation.


      PubDate: 2014-07-26T19:08:44Z
       
  • Molecular cloning and characterization of three cDNAs encoding
           1-deoxy-d-xylulose-5-phosphate synthase in Aquilaria sinensis (Lour.) Gilg
           
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Yanhong Xu , Juan Liu , Liang Liang , Xin Yang , Zheng Zhang , Zhihui Gao , Chun Sui , Jianhe Wei
      Agarwood is an expensive resinous heartwood derived from Aquilaria plants that is widely used in traditional medicines, incense and perfume. The major constituents of agarwood oils are sesquiterpenes, which are obtained from isopentenyl diphosphate and dimethylallyl diphosphate precursors through the plastidial methylerythritol phosphate (MEP) pathway and/or the cytosolic mevalonate pathway. 1-deoxy-d-xylulose-5-phosphate synthase (DXS) is the first rate-limiting enzyme for sesquiterpene synthesis in the MEP pathway. In this study, 3 cDNAs of DXS genes were cloned and characterized from the Aquilaria sinensis (Lour.) Gilg. These genes represent 3 phylogenetically distinct clades conserved among plants. Functional complementation in a DXS-deficient Escherichia coli strain EcAB4-2 demonstrated that they are active DXS, which rescued the E. coli mutant. Their expression profiles in different tissues and in response to different treatments were analyzed by real-time PCR. All 3 genes are highly expressed in stem, followed by leaf and root. AsDXS1 was significantly stimulated by mechanical, chemical, and H2O2 treatment, whereas AsDXS2 and AsDXS3 only responded to chemical treatment and mechanical treatment, respectively. All three genes were oscillation in respond to MJ treatment, with expression peaks occurring at different time points. Our results suggest the conservation of DXS in evolution and imply their distinct functions in primary and defensive sesquiterpene metabolism in A. sinensis.


      PubDate: 2014-07-26T19:08:44Z
       
  • Heterologous expression and functional characterization of the
           NADPH-cytochrome P450 reductase from Capsicum annuum
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Ga-Young Lee , Hyun Min Kim , Sang Hoon Ma , Se Hee Park , Young Hee Joung , Chul-Ho Yun
      Two NADPH-cytochrome P450 reductase (CPR) genes (CaCPR1 and CaCPR2) were isolated from hot pepper (Capsicum annuum L. cv. Bukang). At the red ripe stage, the expression level of CaCPR1 was more than 6-fold greater than that in leaves or flowers. It gradually increased during fruit ripening. The CaCPR2 gene seemed to be expressed constitutively in all of the tested tissues. To investigate the enzymatic properties of CaCPR1, the cDNA of CaCPR1 was heterologously expressed in Escherichia coli without any modification of amino acid sequences, and CaCPR1 was purified. The enzymatic properties of CaCPR1 were confirmed using cytochrome c and cytochrome b 5 as protein substrates. The CaCPR1 could support human CYP1A2-catalyzed reaction. It also reduced tetrazolium salts and ferricyanide. These results show that CaCPR1 is the major CPR in most hot pepper tissues. It is suggested that the CaCPR1 can be used a prototype for studying biological functions and biotechnological applications of plant CPRs.


      PubDate: 2014-07-26T19:08:44Z
       
  • Editorial Board
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82




      PubDate: 2014-07-26T19:08:44Z
       
  • Overexpression of tomato chloroplast-targeted DnaJ protein enhances
           tolerance to drought stress and resistance to Pseudomonas solanacearum in
           transgenic tobacco
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Guodong Wang , Guohua Cai , Fanying Kong , Yongsheng Deng , Nana Ma , Qingwei Meng
      DnaJ proteins as co-chaperones have critical functions in biotic and abiotic stress responses, but their biological functions remain largely uninvestigated. This study investigates the function of a tomato (Lycopersicon esculentum) chloroplast-targeted DnaJ protein (LeCDJ2) using transgenic tobacco. Quantitative real-time polymerase chain reaction analysis showed that LeCDJ2 expression was triggered by salicylic acid (SA), drought and pathogen attack. Ectopic expression of LeCDJ2 in transgenic tobacco reduced the accumulation of superoxide anion radical ( O 2 − ) and hydrogen peroxide (H2O2) under drought stress. Compared with Vec plants, the maximum photochemical efficiency of photosystem II (PSII) (Fv/Fm), net photosynthetic rate (Pn), and content of D1 protein were relatively higher in transgenic plants. The transgenic plants showes better growth, higher chlorophyll content, lower malondialdehyde (MDA) accumulation and relative electrolyte leakage (REL) under drought stress. In addition, overexpression of LeCDJ2 improved the resistance to the pathogen Pseudomonas solanacearum in transgenic tobacco. These results indicate that overexpression of a tomato chloroplast-targeted DnaJ gene enhances tolerance to drought stress and resistance to P. solanacearum in transgenic tobacco.


      PubDate: 2014-07-26T19:08:44Z
       
  • Analysis of gas exchange, stomatal behaviour and micronutrients uncovers
           dynamic response and adaptation of tomato plants to monochromatic light
           treatments
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Andrew O'Carrigan , Mohammad Babla , Feifei Wang , Xiaohui Liu , Michelle Mak , Richard Thomas , Bill Bellotti , Zhong-Hua Chen
      Light spectrum affects the yield and quality of greenhouse tomato, especially over a prolonged period of monochromatic light treatments. Physiological and chemical analysis was employed to investigate the influence of light spectral (blue, green and red) changes on growth, photosynthesis, stomatal behaviour, leaf pigment, and micronutrient levels. We found that plants are less affected under blue light treatment, which was evident by the maintenance of higher A, g s , T r , and stomatal parameters and significantly lower VPD and T leaf as compared to those plants grown in green and red light treatments. Green and red light treatments led to significantly larger increase in the accumulation of Fe, B, Zn, and Cu than blue light. Moreover, guard cell length, width, and volume all showed highly significant positive correlations to g s , T r and negative links to VPD. There was negative impact of monochromatic lights-induced accumulation of Mn, Cu, and Zn on photosynthesis, leaf pigments and plant growth. Furthermore, most of the light-induced significant changes of the physiological traits were partially recovered at the end of experiment. A high degree of morphological and physiological plasticity to blue, green and red light treatments suggested that tomato plants may have developed mechanisms to adapt to the light treatments. Thus, understanding the optimization of light spectrum for photosynthesis and growth is one of the key components for greenhouse tomato production.


      PubDate: 2014-07-26T19:08:44Z
       
  • Water deficit down-regulates miR398 and miR408 in pea (Pisum sativum L.)
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Živko Jovanović , Nemanja Stanisavljević , Aleksandar Mikić , Svetlana Radović , Vesna Maksimović
      MicroRNAs (miRNAs), recently recognized as important regulator of gene expression at posttranscriptional level, have been found to be involved in plant stress responses. The observation that some miRNAs are up- or down regulated by stress implies that they could play vital roles in plant resistance to abiotic and biotic stress. We investigated the effect of water stress treatment during 10 days on expression of conserved miRNAs-miR398a/b and miR408 in pea plants. This time frame reflects the changes as close as possible to the changes where water stress causes visible effects under field condition. It was observed that dehydration strongly down regulates the expression of both miR398a/b and miR408 in pea roots and shoots. The down-regulation of miR398a/b and the up-regulation of potential target genes – copper superoxide dismutase, CSD1, highlight the involvement of this miRNA in pea stress response. To the contrary, the mRNA level of cytochrome c oxidase subunit 5 (COX5b) did not change in roots and shoots of water-stressed plants, compared to control (well) hydrated plants. This suggests that COX5b is not the target of miR398, or that its expression is regulated by some other mechanism. P 1B -ATPase expression increased during water deficit only in the shoots of pea; in the roots there were no changes in expression. Our results help to understand the possible role of investigated miRNAs and their contribution to pea capacity to cope with water deficit.


      PubDate: 2014-07-26T19:08:44Z
       
  • Salinity-induced accumulation of organic osmolytes in barley and wheat
           leaves correlates with increased oxidative stress tolerance:
           In planta evidence for cross-tolerance
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Norhawa Puniran-Hartley , Joseph Hartley , Lana Shabala , Sergey Shabala
      Salinity tolerance in plants is dependent on their abilities to adjust osmotically to reduced soil water potential and to keep intracellular ROS levels under control. Both these processes are believed to rely on de novo synthesis of organic osmolytes (traditionally defined as compatible solutes). However direct in planta evidence for anti-oxidant roles of compatible solutes are scarce. In this work, we induced changes in the level of endogenous organic osmolytes by exposing plants to various levels of NaCl (salinity stress; 50–300 mM range) and then studying sensitivity of leaves to oxidative (UV–B) stress. Increase in the external NaCl concentrations was accompanied by the progressive accumulation in leaf Na+. This accumulation was much higher in old leaves compared with young ones. In old leaves, three major inorganic ions (Na+, Cl− and K+) have made 67.7% and 70.4% of leaf osmotic potential (in wheat and barley, respectively) when exposed to 200 mM NaCl treatment, while in young leaves their contribution was only 43.9% and 46.8%, respectively. Here, organic osmolytes played a substantial role in leaf osmotic adjustment. Increased accumulation of organic osmolytes correlated strongly with activity of PSII in leaves exposed to oxidation inducing UV-B treatment in both species (R 2 = 0.50 for wheat and 0.71 for barley). We conclude that salinity-induced accumulation of organic osmolytes in barley and wheat leaves correlates with increased oxidative stress tolerance and provides the evidence for a mechanism of cross-tolerance between these two stresses.


      PubDate: 2014-07-26T19:08:44Z
       
  • A stress responsive gene of Fortunella crassifolia FcSISP functions in
           salt stress resistance
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Xiaoqing Gong , Jingyan Zhang , Ji-Hong Liu
      Exploration of genes functioning in salt tolerance is crucial for generating transgenic plants with enhanced salt tolerance. In this study, we report the isolation and functional characterization of a stress-responsive gene FcSISP from Meiwa kumquat (Fortunella crassifolia). FcSISP encodes a putative protein of 47 amino acids, with a calculated molecular mass of 4.94 kDa and theoretical isoelectric point of 3.76, and was localized in the nucleus. Transcript levels of FcSISP were induced by dehydration, cold, salt and bacterium causing citrus canker, and hormones (salicylic acid and abscisic acid), with the greatest induction under salt treatment. Overexpression of FcSISP in tobacco (Nicotiana nudicaulis) conferred enhanced salt tolerance. The transgenic lines accumulated lower Na+ contents, leading to reduced Na/K ratio, but accumulated more proline than the wild type (WT). Steady state mRNA levels of genes involved in Na+ exchange (three SOS genes and three NHX genes) and proline synthesis (P5CS and P5CR) were higher in the transgenic lines in comparison with WT. Moreover, overexpression of FcSISP in trifoliate orange [Poncirus trifoliata (L.) Raf.], a widely-used and salt-sensitive citrus rootstock, led to elevated salt tolerance. Taken together, the data demonstrate that FcSISP plays a positive role in salt tolerance and that it holds a great potential for engineering salt tolerance in crops.


      PubDate: 2014-07-26T19:08:44Z
       
  • Selection and validation of reference genes for transcript normalization
           in gene expression studies in Catharanthus roseus
    • Abstract: Publication date: October 2014
      Source:Plant Physiology and Biochemistry, Volume 83
      Author(s): Jacob Pollier , Robin Vanden Bossche , Heiko Rischer , Alain Goossens
      Quantitative Real-Time PCR (qPCR), a sensitive and commonly used technique for gene expression analysis, requires stably expressed reference genes for normalization of gene expression. Up to now, only one reference gene for qPCR analysis, corresponding to 40S Ribosomal protein S9 (RPS9), was available for the medicinal plant Catharanthus roseus, the only source of the commercial anticancer drugs vinblastine and vincristine. Here, we screened for additional reference genes for this plant species by mining C. roseus RNA-Seq data for orthologs of 22 genes known to be stably expressed in Arabidopsis thaliana and qualified as superior reference genes for this model plant species. Based on this, eight candidate C. roseus reference genes were identified and, together with RPS9, evaluated by performing qPCR on a series of different C. roseus explants and tissue cultures. NormFinder, geNorm and BestKeeper analyses of the resulting qPCR data revealed that the orthologs of At2g28390 (SAND family protein, SAND), At2g32170 (N2227-like family protein, N2227) and At4g26410 (Expressed protein, EXP) had the highest expression stability across the different C. roseus samples and are superior as reference genes as compared to the traditionally used RPS9. Analysis of publicly available C. roseus RNA-Seq data confirmed the expression stability of SAND and N2227, underscoring their value as reference genes for C. roseus qPCR analysis.


      PubDate: 2014-07-26T19:08:44Z
       
  • Beneficial rhizobacteria from rice rhizosphere confers high protection
           against biotic and abiotic stress inducing systemic resistance in rice
           seedlings
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Jose Antonio Lucas , Jorge García-Cristobal , Alfonso Bonilla , Beatriz Ramos , Javier Gutierrez-Mañero
      The present study reports a screening for PGPR in a highly selective environment, the rhizosphere of rice plants, in southwestern of Spain. Among the 900 isolates, only 38% were positive for at least one of the biochemical activities to detect putative PGPR. The best 80 isolates were selected and identified by 16S rRNA partial sequencing. Among these, 13 strains were selected for growth promotion assays. Only one strain (BaC1-38) was able to significantly increase height, while nine strains significantly inhibited it. Five strains significantly increased dry weight, and only BaC1-21 significantly decreased it. Based on significant modifications in growth, three bacteria (BaC1-13, BaC1-21 and BaC1-38) were tested for systemic induction of resistance against stress challenge (salt and Xanthomonas campestris infection). Protection against salt stress and pathogen infection was similar; BaC1-38 protected by 80%, BaC1-13 by 50% and BaC1-21 only by 20%. Toxicity of salt stress to the plants was evaluated by photosynthetic efficiency of seedlings. Fv/Fm only decreased significantly in plants inoculated with BaC1-13. ΦPSII also decreased significantly in plants inoculated with BaC1-21, but increased significantly with BaC1-38. NPQ decreased significantly in plants inoculated with BaC1-21. The two strains able to induce systemic resistance against Xanthomonas campestris seem to work by different pathways. BaC1-13 primed enzymes related with the detoxification of reactive oxygen species (ROS). However, BaC1-38 primed pathogenesis-related proteins (PRs), and this pathway was more effective, both improved chlorophyll index confirming the priming state of the plant.


      PubDate: 2014-06-08T14:52:08Z
       
  • Hydrogen peroxide-induced antioxidant activities and cardiotonic glycoside
           accumulation in callus cultures of endemic Digitalis species
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Gunce Sahin Cingoz , Sandeep Kumar Verma , Ekrem Gurel
      The effect of hydrogen peroxide (H2O2) on callus cultures of four Digitalis species (Digitalis lamarckii, Digitalis trojana, Digitalis davisiana and Digitalis cariensis) increased catalase (CAT), superoxide dismutase (SOD), total phenolic, proline activity and cardiotonic glycoside production. Callus derived from hypocotyl explants was cultured on Murashige and Skoog medium supplemented with 0.25 mg L−1 indole-3-acetic acid (IAA) and 0.5 mg L−1 thidiazuron (TDZ). After a month of culture, callus was transferred to MS medium containing 10 mM H2O2 and then incubated for 6 h. The amount of five cardenolides (Lanatoside C, Digitoxin, Digoxigenin, Gitoxigenin and Digoxin) as well as CAT, SOD, total phenolic, proline activity from Digitalis species were compared. No digoxin was detected in all treatments and control groups. The total cardenolides estimated were in the order of D. lamarckii (586.65  μg g−1 dw), D. davisiana (506.79 μg g−1 dw), D. cariensis (376.60 μg g−1 dw) and D. trojana (282.39 μg g−1 dw). It was clear that H2O2 pre-treatment resulted in an increase in enzymatic and nonenzymatic antioxidants. However, a significant negative relationship between cardenolides production and overall activities of CAT, SOD, total phenolic and proline was evident. The described protocol here will be useful for the development of new strategies for a large-scale production of cardenolides.


      PubDate: 2014-06-08T14:52:08Z
       
  • Cold priming drives the sub-cellular antioxidant systems to protect
           photosynthetic electron transport against subsequent low temperature
           stress in winter wheat
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Xiangnan Li , Jian Cai , Fulai Liu , Tingbo Dai , Weixing Cao , Dong Jiang
      Low temperature seriously depresses the growth of wheat through inhibition of photosynthesis, while earlier cold priming may enhance the tolerance of plants to subsequent low temperature stress. Here, winter wheat plants were firstly cold primed (5.2 °C lower temperature than the ambient temperature, viz., 10.0 °C) at the Zadoks growth stage 28 (i.e. re-greening stage, starting on 20th of March) for 7 d, and after 14 d of recovery the plants were subsequently subjected to a 5 d low temperature stress (8.4 °C lower than the ambient temperature, viz., 14.1 °C) at the Zadoks growth stage 31 (i.e. jointing stage, starting on 8th April). Compared to the non-primed plants, the cold-primed plants possessed more effective oxygen scavenging systems in chloroplasts and mitochondria as exemplified by the increased activities of SOD, APX and CAT, resulting in a better maintenance in homeostasis of ROS production. The trapped energy flux (TR O /CS O ) and electron transport (ET O /CS O ) in the photosynthetic apparatus were found functioning well in the cold-primed plants leading to higher photosynthetic rate during the subsequent low temperature stress. Collectively, the results indicate that cold priming activated the sub-cellular antioxidant systems, depressing the oxidative burst in photosynthetic apparatus, hereby enhanced the tolerance to subsequent low temperature stress in winter wheat plants.


      PubDate: 2014-06-08T14:52:08Z
       
  • Reactive oxygen species burst induced by aluminum stress triggers
           mitochondria-dependent programmed cell death in peanut root tip cells
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Wenjing Huang , Xudong Yang , Shaochang Yao , Thet LwinOo , Huyi He , Aiqin Wang , Chuangzhen Li , Longfei He
      Recent studies had certified that aluminum (Al) induced ROS production and programmed cell death (PCD) in higher plants. The relationship between ROS production and PCD occurrence under Al stress is uncovered. The results showed that root elongation inhibition and PCD occurrence was induced by 100 μM AlCl3. Al stress induced ROS burst, up-regulated Rboh and COX gene expression, increased mitochondrial permeability transition pore (MPTP) opening, decreased inner mitochondrial membrane potential (ΔΨm), released cytochrome c from mitochondria to cytoplasm, activated caspase 3-like protease activity. Exogenous H2O2 aggravated the changes caused by Al and accelerated PCD occurrence, but ROS scavenger CAT and AsA reversed the changes caused by Al and inhibited PCD production. A potential cascade of cellular events during Al induced PCD via mitochondria dependent pathway and the mechanism of ROS on regulating PCD induced by Al is proposed.


      PubDate: 2014-06-08T14:52:08Z
       
  • Effect of leaf dehydration duration and dehydration degree on PSII
           photochemical activity of papaya leaves
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Meijun Liu , Zishan Zhang , Huiyuan Gao , Cheng Yang , Xingli Fan , Dandan Cheng
      Although the effect of dehydration on photosynthetic apparatus has been widely studied, the respective effect of dehydration duration and dehydration degree was neglected. This study showed that, when leaves dehydrated in air, the PSII activities of leaves decreased with the decline of leaf relative water content (RWC). Unexpectedly, when leaves dehydrated to same RWC, the decreases in Fv/Fm, Ψo and RC/CSm were lower in leaves dehydrating at 43 °C than those at 25 °C. However, to reach the same RWC, leaves dehydrating at 43 °C experienced 1/6 of the dehydration duration for leaves dehydrating at 25 °C. To distinguish the respective effect of dehydration degree and dehydration duration on photosynthetic apparatus, we studied the PSII activities of leaves treated with different concentration of PEG solutions. Increasing dehydration degree aggravated the decline of Fv/Fm, Ψo and RC/CSm in leaves with the same dehydration duration, while prolonging the dehydration duration also exacerbated the decline of Fv/Fm, Ψo and RC/CSm in leaves with identical dehydration degree. With the same dehydration degree and duration, high temperature enhanced the decrease of Fv/Fm, Ψo and RC/CSm in the leaves. When leaves dehydrated in air, the effect of high temperature was underestimated due to reduction of dehydration duration. The results demonstrated that, dehydration degree and duration both play important roles in damage to photosynthetic apparatus. We suggest that, under combined stresses, the effects of dehydration degree and duration on plants should be considered comprehensively, otherwise, partial or incorrect results may be obtained.
      Graphical abstract image

      PubDate: 2014-06-08T14:52:08Z
       
  • Different mechanisms drive the performance of native and invasive woody
           species in response to leaf phosphorus supply during periods of drought
           stress and recovery
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Marciel Teixeira Oliveira , Camila Dias Medeiros , Gabriella Frosi , Mauro Guida Santos
      The effects of drought stress and leaf phosphorus (Pi) supply on photosynthetic metabolism in woody tropical species are not known, and given the recent global environmental change models that forecast lower precipitation rates and periods of prolonged drought in tropical areas, this type of study is increasingly important. The effects of controlled drought stress and Pi supply on potted young plants of two woody species, Anadenanthera colubrina (native) and Prosopis juliflora (invasive), were determined by analyzing leaf photosynthetic metabolism, biochemical properties and water potential. In the maximum stress, both species showed higher leaf water potential (Ψl) in the treatment drought +Pi when compared with the respective control −Pi. The native species showed higher gas exchange under drought +Pi than under drought –Pi conditions, while the invasive species showed the same values between drought +Pi and −Pi. Drought affected the photochemical part of photosynthetic machinery more in the invasive species than in the native species. The invasive species showed higher leaf amino acid content and a lower leaf total protein content in both Pi treatments with drought. The two species showed different responses to the leaf Pi supply under water stress for several variables measured. In addition, the strong resilience of leaf gas exchange in the invasive species compared to the native species during the recovery period may be the result of higher efficiency of Pi use. The implications of this behavior for the success of this invasive species in semiarid environments are discussed.


      PubDate: 2014-06-08T14:52:08Z
       
  • Wound healing response and xylem differentiation in tobacco plants
           over-expressing a fungal endopolygalacturonase is mediated by copper amine
           oxidase activity
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Alessandra Cona , Alessandra Tisi , Sandip Annasaheb Ghuge , Stefano Franchi , Giulia De Lorenzo , Riccardo Angelini
      In this work, we have investigated the involvement of copper amine oxidase (CuAO; EC 1.4.3.21) in wound healing and xylem differentiation of Nicotiana tabacum plants over-expressing a fungal endopolygalacturonase (PG plants), which show constitutively activated defence responses. In petioles and stems of PG plants, we found higher CuAO activity and lower polyamine (PA) levels, particularly putrescine (Put), with respect to wild-type (WT) plants. Upon wounding, a more intense autofluorescence of cell wall phenolics was observed in correspondence of wound surface, extending to epidermis and cortical parenchima only in PG plants. This response was mostly dependent on CuAO activity, as suggested by the reversion of autofluorescence upon supply of 2-bromoethylamine (2-BrEt), a CuAO specific inhibitor. Moreover, in unwounded plants, histochemical analysis revealed a tissue-specific expression of the enzyme in the vascular cambium and neighboring derivative cells of both petioles and stems of PG plants, whereas the corresponding WT tissues appeared unstained or faintly stained. A higher histochemical CuAO activity was also observed in xylem cells of PG plants as compared to WT xylem tissues suggesting a peculiar role of CuAO activity in xylem differentiation in PG plants. Indeed, roots of PG plants exhibited early xylem differentiation, a phenotype consistent with both the higher CuAO and the lower Put levels observed and supported by the 2-BrEt-mediated reversion of early root xylem differentiation and H2O2 accumulation. These results strongly support the relevance of PA-catabolism derived H2O2 in defence responses, such as those signaled by a compromised status of cell wall pectin integrity.


      PubDate: 2014-06-08T14:52:08Z
       
  • Differential expression of molybdenum transport and assimilation genes
           between two winter wheat cultivars (Triticum aestivum)
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Zhaojun Nie , Chengxiao Hu , Hongen Liu , Qiling Tan , Xuecheng Sun
      Molybdenum (Mo) is an essential trace element for higher plants. Winter wheat cultivar 97003 has a higher Mo efficiency than 97014 under Mo-deficiency stress. Mo efficiency is related to Mo uptake, transfer and assimilation in plants. Several genes are involved in regulating Mo uptake, transfer and assimilation in plants. To obtain a better understanding of the aforementioned difference in Mo uptake, we have conducted a hydroponic trail to investigate the expression of genes related to Mo uptake, transfer and assimilation in the above two cultivars. The results indicate a closed relationship between Mo uptake and TaSultr5.1, TaSultr5.2 and TaCnx1 expression, according to a stepwise regression analysis of the time course of Mo uptake in the two cultivars. Meanwhile, expression of TaSultr5.2 in roots also showed a positive relationship with Mo uptake rates. 97003 had stronger Mo uptake than 97014 at low Mo-application rates (less than 1 μmol Mo L−1) due to the higher expression of TaSultr5.2, TaSultr5.1 and TaCnx1 in roots. On the contrary, Mo uptake of 97003 was weaker than 97014 at high Mo application rates (ranging from 5 to 20 μmol Mo L−1), which was related to significant down-regulation of TaSultr5.2 and TaCnx1 genes in roots of 97003 compared to 97014. Therefore, we speculated that the differential-expression intensities of TaSultr5.2, TaSultr5.1 and TaCnx1 could be the cause of the difference in Mo uptake between the two winter wheat cultivars at low and high Mo application levels.


      PubDate: 2014-06-02T14:26:04Z
       
  • Polyamine biosynthesis and degradation are modulated by exogenous
           gamma-aminobutyric acid in root-zone hypoxia-stressed melon roots
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Chunyan Wang , Longquan Fan , Hongbo Gao , Xiaolei Wu , Jingrui Li , Guiyun Lv , Binbin Gong
      We detected physiological change and gene expression related to PA metabolism in melon roots under controlled and hypoxic conditions with or without 5 mM GABA. Roots with hypoxia treatment showed a significant increase in glutamate decarboxylase (GAD) activity and endogenous GABA concentration. Concurrently, PA biosynthesis and degradation accelerated with higher gene expression and enzymes activity. However, endogenous GABA concentrations showed a large and rapid increase in Hypoxia + GABA treated roots. This led to a marked increase in Glu concentration by feedback inhibition of GAD activity. Hypoxia + GABA treatment enhanced arginine (Arg), ornithine (Orn) and methionine (Met) levels, promoting enzyme gene expression levels and arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) activities in roots. Hypoxia + GABA treatment significantly increased concentrations of free putrescine (Put), spermidine (Spd) and spermine (Spm) from day two to eight, promoting the PA conversion to soluble conjugated and insoluble bound forms. However, PA degradation was significantly inhibited in hypoxia + GABA treated roots by significantly decreasing gene expression and activity of diamine oxidase (DAO) and polyamine oxidase (PAO). However, exogenous GABA showed a reduced effect in control compared with hypoxic conditions. Our data suggest that alleviating effect of exogenous GABA to hypoxia is closely associated with physiological regulation of PA metabolism. We propose a potential negative feedback mechanism of higher endogenous GABA levels from combined effects of hypoxia and exogenous GABA, which alleviate the hypoxia damage by accelerating PA biosynthesis and conversion as well as preventing PA degradation in melon plants.


      PubDate: 2014-05-26T10:02:24Z
       
  • The role of isoflavone metabolism in plant protection depends on
           the rhizobacterial MAMP that triggers systemic resistance against
           Xanthomonas axonopodis pv. glycines in Glycine max (L.) Merr. cv. Osumi
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Elena Algar , F. Javier Gutierrez-Mañero , Ana Garcia-Villaraco , Daniel García-Seco , J. Antonio Lucas , Beatriz Ramos-Solano
      Glycine max (L.) Merr. plays a crucial role in both the field of food and the pharmaceutical industry due to their input as plant protein and to the benefits of isoflavones (IF) for health. In addition, IF play a key role in nodulation and plant defense and therefore, an increase in IF would be desirable for better field performance. IF are secondary metabolites and therefore, inducible, so finding effective agents to increase IF contents is interesting. Among these agents, plant growth promoting rhizobacteria (PGPR) have been used to trigger systemic induction of plant's secondary metabolism through their microbe associated molecular patterns (MAMPs) that fit in the plant's receptors to start a systemic response. The aim of this study was to evaluate the ability of 4 PGPR that had a contrasted effect on IF metabolism, to protect plants against biotic stress and to establish the relation between IF profile and the systemic response triggered by the bacteria. Apparently, the response involves a lower sensitivity to ethylene and despite the decrease in effective photosynthesis, growth is only compromised in the case of M84, the most effective in protection. All strains protected soybean against Xanthomonas axonopodis pv. glycines (M84 > N5.18 > Aur9>N21.4) and only M84 and N5.18 involved IF. N5.18 stimulated accumulation of IF before pathogen challenge. M84 caused a significant increase on IF only after pathogen challenge and N21.4 caused a significant increase on IF content irrespective of pathogen challenge. Aur9 did not affect IF. These results point out that all 4 strains have MAMPs that trigger defensive metabolism in soybean. Protection induced by N21.4 and Aur9 involves other metabolites different to IF and the role of IF in defence depends on the previous metabolic status of the plant and on the bacterial MAMP.


      PubDate: 2014-05-26T10:02:24Z
       
  • The rice gene OsZFP6 functions in multiple stress tolerance responses in
           yeast and Arabidopsis
    • Abstract: Publication date: September 2014
      Source:Plant Physiology and Biochemistry, Volume 82
      Author(s): Qing-jie Guan , Li-feng Wang , Qing-yun Bu , Zhen-yu Wang
      The role of zinc finger proteins in organismal stress conditions has been widely reported. However, little is known concerning the function of CCHC-type zinc finger proteins in rice. In this study, OsZFP6, a rice CCHC-type zinc finger protein 6 gene, was cloned from rice using RT-PCR. The OsZFP6 protein contains 305 amino acids and a conserved zinc finger domain and is localised to the nucleus. Southern blot analysis revealed that a single copy was encoded in the rice genome. OsZFP6 expression was increased by abiotic stress, including salt (NaCl), alkali (NaHCO3) and H2O2 treatment. When OsZFP6 was transformed into yeast, the transgenic yeast showed significantly increased resistance to NaHCO3 compared to the control. Moreover, Arabidopsis transgenic plants overexpressing OsZFP6 were more tolerant to both NaHCO3 and H2O2 treatments. Overall, we uncovered a role for OsZFP6 in abiotic stress responses and identified OsZFP6 as a putatively useful gene for developing crops with increased alkali and H2O2 tolerance.


      PubDate: 2014-05-26T10:02:24Z
       
 
 
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