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Journal Cover   Plant Physiology and Biochemistry
  [SJR: 1.041]   [H-I: 70]   [11 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0981-9428
   Published by Elsevier Homepage  [2588 journals]
  • Autochthonous arbuscular mycorrhizal fungi and Bacillus thuringiensis from
           a degraded Mediterranean area can be used to improve physiological traits
           
    • Abstract: Publication date: Available online 18 March 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Elisabeth Armada , Rosario Azcón , Olga M. López-Castillo , Mónica Calvo-Polanco , Juan Manuel Ruiz-Lozano
      Studies have shown that some microorganisms autochthonous from stressful environments are beneficial when used with autochthonous plants, but these microorganisms rarely have been tested with allochthonous plants of agronomic interest. This study investigates the effectiveness of drought-adapted autochthonous microorganisms [Bacillus thuringiensis (Bt) and a consortium of arbuscular mycorrhizal (AM) fungi] from a degraded Mediterranean area to improve plant growth and physiology in Zea mays under drought stress. Maize plants were inoculated or not with B. thuringiensis, a consortium of AM fungi or a combination of both microorganisms. Plants were cultivated under well-watered conditions or subjected to drought stress. Several physiological parameters were measured, including among others, plant growth, photosynthetic efficiency, nutrients content, oxidative damage to lipids, accumulation of proline and antioxidant compounds, root hydraulic conductivity and the expression of plant aquaporin genes. Under drought conditions, the inoculation of Bt increased significantly the accumulation of nutrients. The combined inoculation of both microorganisms decreased the oxidative damage to lipids and accumulation of proline induced by drought. Several maize aquaporins able to transport water, CO2 and other compounds were regulated by the microbial inoculants. The impact of these microorganisms on plant drought tolerance was complementary, since Bt increased mainly plant nutrition and AM fungi were more active improving stress tolerance/homeostatic mechanisms, including regulation of plant aquaporins with several putative physiological functions. Thus, the use of autochthonous beneficial microorganisms from a degraded Mediterranean area is useful to protect not only native plants against drought, but also an agronomically important plant such as maize.


      PubDate: 2015-03-19T04:31:50Z
       
  • Priming effect of abscisic acid on alkaline stress tolerance in rice
           (Oryza sativa L.) seedlings
    • Abstract: Publication date: Available online 12 March 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Li-Xing Wei , Bing-Sheng Lv , Ming-Ming Wang , Hong-Yuan Ma , Hao-Yu Yang , Xiao-Long Liu , Chang-Jie Jiang , Zheng-Wei Liang
      Saline–alkaline stress is characterized by high salinity and high alkalinity (high pH); alkaline stress has been shown to be the primary factor inhibiting rice seedling growth. In this study, we investigated the potential priming effect of abscisic acid (ABA) on tolerance of rice seedlings to alkaline stress simulated by Na2CO3. Seedlings were pretreated with ABA at concentrations of 0 (control), 10, and 50 μM by root-drench for 24 h and then transferred to a Na2CO3 solution that did not contain ABA. Compared to control treatment, pretreatment with ABA substantially improved the survival rate of rice seedlings and increased biomass accumulation after 7 days under the alkaline condition. ABA application at 10 μM also alleviated the inhibitory effects of alkaline stress on the total root length and root surface area. Physiologically, ABA increased relative water content (RWC) and decreased cell membrane injury degree (MI) and Na+/K+ ratios. In contrast, fluridone (an ABA biosynthesis inhibitor) decreased the RWC and increased MI in shoots under the alkaline conditions. These data suggest that ABA has a potent priming effect on the adaptive response to alkaline stress in rice and may be useful for improving rice growth in saline–alkaline paddy fields.


      PubDate: 2015-03-15T08:01:11Z
       
  • A redox-dependent dimerization switch regulates activity and tolerance for
           reactive oxygen species of barley seed glutathione peroxidase
    • Abstract: Publication date: Available online 10 March 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Nicolas Navrot , Nicklas Skjoldager , Jakob Bunkenborg , Birte Svensson , Per Hägglund
      Monomeric and dimeric forms of recombinant barley (Hordeum vulgare subsp. vulgare) glutathione peroxidase 2 (HvGpx2) are demonstrated to display distinctly different functional properties in vitro. Monomeric HvGpx2 thus has five fold higher catalytic efficiency than the dimer towards tert-butyl hydroperoxide, but is more sensitive to inactivation by hydrogen peroxide. Treatment of the monomer with hydrogen peroxide results in dimer formation. This observed new behavior of a plant glutathione peroxidase suggests a mechanism involving a switch from a highly catalytically competent monomer to a less active, but more oxidation-resistant dimer.


      PubDate: 2015-03-11T07:32:49Z
       
  • Identification of genes involved in the drought adaptation and recovery in
           Portulaca oleracea by differential display
    • Abstract: Publication date: Available online 4 March 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Rodrigo Matías D'Andrea , Agustina Triassi , María Isabel Casas , Carlos Santiago Andreo , María Valeria Lara
      Portulaca oleracea is one of the richest plant sources of ω-3 and ω-6 fatty acids and other compounds potentially valuable for nutrition. It is broadly established in arid, semiarid and well-watered fields, thus making it a promising candidate for research on abiotic stress resistance mechanisms. It is capable of withstanding severe drought and then of recovering upon rehydration. Here, the adaptation to drought and the posterior recovery was evaluated at transcriptomic level by differential display validated by qRT-PCR. Of the 2279 transcript-derived fragments amplified, 202 presented differential expression. Ninety of them were successfully isolated and sequenced. Selected genes were tested against different abiotic stresses in P. oleracea and the behavior of their orthologous genes in Arabidopsis thaliana was also explored to seek for conserved response mechanisms. In drought adapted and in recovered plants changes in expression of many protein metabolism-, lipid metabolism- and stress-related genes were observed. Many genes with unknown function were detected, which also respond to other abiotic stresses. Some of them are also involved in the seed desiccation/imbibition process and thus would be of great interest for further research. The potential use of candidate genes to engineer drought tolerance improvement and recovery is discussed.


      PubDate: 2015-03-06T13:55:02Z
       
  • Screening for salt-responsive proteins in two contrasting alfalfa
           cultivars using a comparative proteome approach
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Md. Atikur Rahman , Iftekhar Alam , Yong-Goo Kim , Na-Young Ahn , Sung-Hyun Heo , Dong-Gi Lee , Gongshe Liu , Byung-Hyun Lee
      A comparative proteomic approach was carried out between two contrasting alfalfa cultivars, nonomu (NM-801; salt tolerant) and vernal (VN; salt intolerant) in terms of salt tolerance. Seedlings were subjected to salt stress (50 and 100 mM NaCl) for three days. Several physiological parameters (leaf water, chlorophyll, root Na+, K+, and Ca2+) and root proteome profile were analyzed. Comparison of physiological status revealed that NM-801 is more tolerant to salt than VN. Eighty three differentially expressed proteins were found on 2-DE maps, of which 50 were identified by MALDI-TOF or MALDI-TOF/TOF mass spectrometry. These proteins were involved in ion homeostasis, protein turnover and signaling, protein folding, cell wall components, carbohydrate and energy metabolism, reactive oxygen species regulation and detoxification, and purine and fatty acid metabolism. The comparative proteome analysis showed that 33 salt-responsive proteins were significantly changed in both cultivars, while 17 (14 in VN and 3 in NM-801) were cultivar-specific. Peroxidase, protein disulfide-isomerase, NAD synthetase, and isoflavone reductase were up-regulated significantly only in NM-801 in all salt concentrations. In addition, we identified novel proteins including NAD synthetase and biotin carboxylase-3 that were not reported previously as salt-responsive. Taken together, these results provide new insights of salt stress tolerance in alfalfa.


      PubDate: 2015-03-06T13:55:02Z
       
  • Changes in cell size and number and in rhizodermal development contribute
           to root tip swelling of Hyoscyamus albus roots subjected to iron
           deficiency
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Yuki Kawahara , Yoshie Kitamura
      Root tip swelling is a common phenomenon observed when plant roots are subjected to Fe deficiency. We analysed whether an increase in cell number or an enlargement of cell width was involved in this phenomenon. Root tips of Hyoscyamus albus cultured with or without Fe were stained with fluorescent SYTO14 and analysed by confocal laser-scanning microscopy. Time-course and position-based examination revealed that the inhibition of longitudinal cell elongation and acceleration of transverse cell enlargement under Fe deficiency started from the tips and then extended towards the base during the time-course period. An increase in cell number also occurred behind the tips. In addition, the development of rhizodermal protrusions was observed on the surface of roots subjected to Fe deficiency. These results indicated that changes in cell size and number and in root hair development were all involved in root tip swelling.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • Species-specific enzymatic tolerance of sulfide toxicity in plant roots
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Nicole M. Martin , Brian R. Maricle
      Toxic effects of sulfide come from a poisoning of a number of enzymes, especially cytochrome c oxidase, which catalyzes the terminal step in mitochondrial aerobic respiration. Despite this, some estuarine plants live in sulfide-rich sediments. We hypothesized estuarine and flooding-tolerant species might be more tolerant of sulfide compared to upland species, and this was tested by measures of root cytochrome c oxidase and alcohol dehydrogenase activities in extracts exposed to sulfide. Enzyme activities were measured in 0, 5, 10, 15, and 20 μM sodium sulfide, and compared among 17 species of plants. Activities of alcohol dehydrogenase and cytochrome c oxidase were both reduced by increasing sulfide concentration, but cytochrome c oxidase was more sensitive to sulfide compared to alcohol dehydrogenase. Activities of cytochrome c oxidase were reduced to near zero at 5–10 μM sulfide whereas alcohol dehydrogenase activities were only reduced by about 50% at 10 μM sulfide. All species were sensitive to increasing sulfide, but to different degrees. Cytochrome c oxidase in flooding-sensitive species was decreased to near zero activity at 5 μM sulfide, whereas activities in some flooding-tolerant species were still detectable until 15 μM sulfide. Cytochrome c oxidase activities in some estuarine species were low even in the absence of sulfide, perhaps an adaptation to avoid sulfide vulnerability in their native, sulfide-rich habitat. This illustrates the potent metabolic effects of sulfide, and this is the first demonstration of varying sensitivities of cytochrome c oxidase to sulfide across organisms, making these data of novel importance.


      PubDate: 2015-03-06T13:55:02Z
       
  • Coumarin pretreatment alleviates salinity stress in wheat seedlings
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Ahmed Mahmoud Saleh , M.M.Y. Madany
      The potentiality of COU to improve plant tolerance to salinity was investigated. Wheat grains were primed with COU (50 ppm) and then grown under different levels of NaCl (50, 100, 150 mM) for two weeks. COU pretreatment improved the growth of wheat seedling under salinity, relative to COU-untreated seedlings, due to the accumulation of osmolytes such as soluble sugars and proline. Moreover, COU treatment significantly improved K+/Na+ ratio in the shoots of both salt stressed and un-stressed seedlings. However, in the roots, this ratio increased only under non-salinity. In consistent with phenylalanine ammonia lyase (PAL), phenolics and flavonoids were accumulated in COU-pretreated seedlings under the higher doses of salinity, relative to COU-untreated seedlings. COU primed seedlings showed higher content of the coumarin derivative, scopoletin, and salicylic, chlorogenic, syringic, vanillic, gallic and ferulic acids, under both salinity and non-salinity conditions. Salinity stress significantly improved the activity of peroxidase (POD) in COU-pretreated seedlings. However, the effect of COU on the total antioxidant capacity (TAC) was only obtained at the highest dose of NaCl (150 mM). The present results suggest that COU pretreatment could alleviate the adverse effect of salinity on the growth of wheat seedlings through enhancing, at least partly, the osmoregulation process and antioxidant defense system.


      PubDate: 2015-03-06T13:55:02Z
       
  • Severe drought stress is affecting selected primary metabolites,
           polyphenols, and volatile metabolites in grapevine leaves (Vitis vinifera
           cv. Pinot noir)
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Michaela Griesser , Georg Weingart , Katharina Schoedl-Hummel , Nora Neumann , Manuel Becker , Kurt Varmuza , Falk Liebner , Rainer Schuhmacher , Astrid Forneck
      Extreme weather conditions with prolonged dry periods and high temperatures as well as heavy rain events can severely influence grapevine physiology and grape quality. The present study evaluates the effects of severe drought stress on selected primary metabolites, polyphenols and volatile metabolites in grapevine leaves. Among the 11 primary metabolites, 13 polyphenols and 95 volatiles which were analyzed, a significant discrimination between control and stressed plants of 7 primary metabolites, 11 polyphenols and 46 volatile metabolites was observed. As single parameters are usually not specific enough for the discrimination of control and stressed plants, an unsupervised (PCA) and a supervised (PLS-DA) multivariate approach were applied to combine results from different metabolic groups. In a first step a selection of five metabolites, namely citric acid, glyceric acid, ribose, phenylacetaldehyde and 2-methylbutanal were used to establish a calibration model using PLS regression to predict the leaf water potential. The model was strong enough to assign a high number of plants correctly with a correlation of 0.83. The PLS-DA provides an interesting approach to combine data sets and to provide tools for the specific evaluation of physiological plant stresses.


      PubDate: 2015-03-06T13:55:02Z
       
  • SVP-like MADS-box protein from Carya cathayensis forms higher-order
           complexes
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Jingjing Wang , Chuanming Hou , Jianqin Huang , Zhengjia Wang , Yingwu Xu
      To properly regulate plant flowering time and construct floral pattern, MADS-domain containing transcription factors must form multimers including homo- and hetero-dimers. They are also active in forming hetero-higher-order complexes with three to five different molecules. However, it is not well known if a MADS-box protein can also form homo-higher-order complex. In this study a biochemical approach is utilized to provide insight into the complex formation for an SVP-like MADS-box protein cloned from hickory. The results indicated that the protein is a heterogeneous higher-order complex with the peak population containing over 20 monomers. Y2H verified the protein to form homo-complex in yeast cells. Western blot of the hickory floral bud sample revealed that the protein exists in higher-order polymers in native. Deletion assays indicated that the flexible C-terminal residues are mainly responsible for the higher-order polymer formation and the heterogeneity. Current results provide direct biochemical evidences for an active MADS-box protein to be a high order complex, much higher than a quartermeric polymer. Analysis suggests that a MADS-box subset may be able to self-assemble into large complexes, and thereby differentiate one subfamily from the other in a higher-order structural manner. Present result is a valuable supplement to the action of mechanism for MADS-box proteins in plant development.


      PubDate: 2015-03-06T13:55:02Z
       
  • Editorial Board
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88




      PubDate: 2015-03-06T13:55:02Z
       
  • Potassium phosphite increases tolerance to UV-B in potato
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Oyarburo Natalia Soledad , Machinandiarena Milagros Florencia , Feldman Mariana Laura , Daleo Gustavo Raúl , Andreu Adriana Balbina , Olivieri Florencia Pía
      The use of biocompatible chemical compounds that enhance plant disease resistance through Induced Resistance (IR) is an innovative strategy to improve the yield and quality of crops. Phosphites (Phi), inorganic salts of phosphorous acid, are environment friendly, and have been described to induce disease control. Phi, similar to other plant inductors, are thought to be effective against different types of biotic and abiotic stress, and it is assumed that the underlying signaling pathways probably overlap and interact. The signaling pathways triggered by UV-B radiation, for instance, are known to crosstalk with other signaling routes that respond that biotic stress. In the present work, the effect of potassium phosphite (KPhi) pre-treatment on UV-B stress tolerance was evaluated in potato leaves. Plants were treated with KPhi and, after 3 days, exposed to 2 h/day of UV-B (1.5 Watt m−2) for 0, 3 and 6 days. KPhi pre-treatment had a beneficial effect on two photosynthetic parameters, specifically chlorophyll content and expression of the psbA gene. Oxidative stress caused by UV-B was also prevented by KPhi. A decrease in the accumulation of hydrogen peroxide (H2O2) in leaves and an increase in guaiacol peroxidase (POD) and superoxide dismutase (SOD) activities were also observed. In addition, the expression levels of a gene involved in flavonoid synthesis increased in UV-B-stressed plants only when pre-treated with KPhi. Finally, accumulation of glucanases and chitinases was induced by UV-B stress and markedly potentiated by KPhi pre-treatment. Altogether, this is the first report that shows a contribution of KPhi in UV-B stress tolerance in potato plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Interactive effects of supplemental UV-B and temperature in European aspen
           seedlings: Implications for growth, leaf traits, phenolic defense and
           associated organisms
    • Abstract: Publication date: Available online 4 March 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Tendry R. Randriamanana , Anu Lavola , Riitta Julkunen-Tiitto
      Past studies reveal opposite effects of elevated UV-B and temperature on plant growth and concentrations of UV-B absorbing compounds, yet few studies have dealt with the combined and interactive effects of these two climate change factors on woody dioecious plants. We investigated the interactive effects of UV-B and temperature treatments on growth, leaf traits and phenolic concentrations in Populus tremula L. (European aspen) seedlings. We also considered the consequences of these effects on their associated organisms: herbivorous insects, rust pathogens, the presence of endophytic fungi and whether or not the responses differ between genders and genotypes. Supplemental temperature and UV-B were modulated to +2 °C and +30.77% above ambient conditions, respectively. Warming increased growth, photosynthesis and foliar nitrogen concentration but reduced leaf thickness and phenolic concentrations. On the other hand, supplemental UV-B increased total phenolic glycosides, mainly flavonols and phenolic acids, and partially counteracted the positive effects of warming on growth. Fast growing genotypes were less susceptible to the growth-reducing effect of combined UVB + T, less infected with rust disease and less prone to insect damage probably due to their higher salicylate and lower nitrogen concentrations. Under ambient temperature, the males of European aspen were taller and had bigger leaves than the females, while under elevated temperature, females grew bigger and, under UV-B, had more tremulacin than males. The multiple interactive effects of UV-B and temperature on growth, leaf traits and phenolic compounds, highlight the importance of multifactor experiments as a realistic predictor of plant responses to climate change.


      PubDate: 2015-03-06T13:55:02Z
       
  • Enhanced production of steviol glycosides in mycorrhizal plants: A
           concerted effect of arbuscular mycorrhizal symbiosis on transcription of
           biosynthetic genes
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Shantanu Mandal , Shivangi Upadhyay , Ved Pal Singh , Rupam Kapoor
      Stevia rebaudiana (Bertoni) produces steviol glycosides (SGs) – stevioside (stev) and rebaudioside-A (reb-A) that are valued as low calorie sweeteners. Inoculation with arbuscular mycorrhizal fungi (AMF) augments SGs production, though the effect of this interaction on SGs biosynthesis has not been studied at molecular level. In this study transcription profiles of eleven key genes grouped under three stages of the SGs biosynthesis pathway were compared. The transcript analysis showed upregulation of genes encoding 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway enzymes viz.,1-deoxy-d-xylulose 5-phospate synthase (DXS), 1-deoxy-d-xylulose 5-phospate reductoisomerase (DXR) and 2-C-methyl-D-erytrithol 2,4-cyclodiphosphate synthase (MDS) in mycorrhizal (M) plants. Zn and Mn are imperative for the expression of MDS and their enhanced uptake in M plants could be responsible for the increased transcription of MDS. Furthermore, in the second stage of SGs biosynthesis pathway, mycorrhization enhanced the transcription of copalyl diphosphate synthase (CPPS) and kaurenoic acid hydroxylase (KAH). Their expression is decisive for SGs biosynthesis as CPPS regulates flow of metabolites towards synthesis of kaurenoid precursors and KAH directs these towards steviol synthesis instead of gibberellins. In the third stage glucosylation of steviol to reb-A by four specific uridine diphosphate (UDP)-dependent glycosyltransferases (UGTs) occurs. While higher transcription of all the three characterized UGTs in M plants explains augmented production of SGs; higher transcript levels of UGT76G1, specifically improved reb-A to stev ratio implying increased sweetness. The work signifies that AM symbiosis upregulates the transcription of all eleven SGs biosynthesis genes as a result of improved nutrition and enhanced sugar concentration due to increased photosynthesis in M plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Using the quantum yields of photosystem II and the rate of net
           photosynthesis to monitor high irradiance and temperature stress in
           chrysanthemum (Dendranthema grandiflora)
    • Abstract: Publication date: May 2015
      Source:Plant Physiology and Biochemistry, Volume 90
      Author(s): Eshetu Janka , Oliver Körner , Eva Rosenqvist , Carl-Otto Ottosen
      Under a dynamic greenhouse climate control regime, temperature is adjusted to optimise plant physiological responses to prevailing irradiance levels; thus, both temperature and irradiance are used by the plant to maximise the rate of photosynthesis, assuming other factors are not limiting. The control regime may be optimised by monitoring plant responses, and may be promptly adjusted when plant performance is affected by extreme microclimatic conditions, such as high irradiance or temperature. To determine the stress indicators of plants based on their physiological responses, net photosynthesis (Pn) and four chlorophyll-a fluorescence parameters: maximum photochemical efficiency of PSII [Fv/Fm], electron transport rate [ETR], PSII operating efficiency [F′q/F′m], and non-photochemical quenching [NPQ] were assessed for potted chrysanthemum (Dendranthema grandiflora Tzvelev) ‘Coral Charm’ under different temperature (20, 24, 28, 32, 36 °C) and daily light integrals (DLI; 11, 20, 31, and 43 mol m−2 created by a PAR of 171, 311, 485 and 667 μmol m−2 s−1 for 16 h). High irradiance (667 μmol m−2 s−1) combined with high temperature (>32 °C) significantly (p < 0.05) decreased Fv/Fm. Under high irradiance, the maximum Pn and ETR were reached at 24 °C. Increased irradiance decreased the PSII operating efficiency and increased NPQ, while both high irradiance and temperature had a significant effect on the PSII operating efficiency at temperatures >28 °C. Under high irradiance and temperature, changes in the NPQ determined the PSII operating efficiency, with no major change in the fraction of open PSII centres (qL) (indicating a QA redox state). We conclude that 1) chrysanthemum plants cope with excess irradiance by non-radiative dissipation or a reversible stress response, with the effect on the Pn and quantum yield of PSII remaining low until the temperature reaches 28 °C and 2) the integration of online measurements to monitor photosynthesis and PSII operating efficiency may be used to optimise dynamic greenhouse control regimes by detecting plant stress caused by extreme microclimatic conditions.


      PubDate: 2015-03-06T13:55:02Z
       
  • BdVIL4 regulates flowering time and branching through repressing miR156 in
           ambient temperature dependent way in Brachypodium distachyon
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Yanrong An , Yuyu Guo , Chengcheng Liu , Hailong An
      Responsing to environmental signals, VERNALIZATION INSENSITIVE 3 (VIN3) family proteins are involved in plant development control by repressing the target genes epigenecticly together with Polycomb Repressive Complex 2 (PRC2) complex. BdVIL4 is a VIN3 like gene in Brachypodium distachyon, preferentially expressed in young tissues spatially. The RNAi plants were constructed to study the function of BdVIL4 on the development process. The plants with BdVIL4 RNA interferenced (BdVIL4 RNAi plants) had no obvious difference from the wild at 23 °C, but flowered significantly later and had more branches than the control at l6 °C. In BdVIL4 RNAi plants the expression of miR156 were upregulated, and much more at low temperature (l6 °C). Coincidentally, similar to the BdVIL4 RNAi plants, the miR156 overexpressors also showed late flowering and more branches, and the late flowering phynotype just only performanced at lower temperature. The results suggested that BdVIL4 are involved in the regulation of branching and flowering responsing to the ambient temperature by repressing the expression of miR156.


      PubDate: 2015-03-06T13:55:02Z
       
  • MhNCED3, a gene encoding 9-cis-epoxycarotenoid dioxygenase in Malus
           hupehensis Rehd., enhances plant tolerance to Cl– stress by reducing
           Cl– accumulation
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Wei-wei Zhang , Hong-qiang Yang , Shu-zhen You , Shu-lei Fan , Kun Ran
      High Cl– concentrations in tissues can be toxic to crop plants and may lead to reduced growth rates and yields. 9-cis-epoxycarotenoid dioxygenase (NCED) is thought to be involved in the biosynthesis of abscisic acid (ABA), which is an important regulator of plant adaptive responses to stress. Here, the expression of MhNCED3 in Malus hupehensis Rehd. and the effects of MhNCED3 on plant tolerance to Cl– stress were explored. The results showed that MhNCED3 expression and ABA biosynthesis in M. hupehensis Rehd. were induced by Cl– stress. Ectopic expression of MhNCED3 in Arabidopsis complemented the phenotypic defects of the 129B08/nced3 mutant and enhanced WT tolerance to Cl– stress. The transgenic Arabidopsis showed improved growth and developmental status, increased ABA contents, and reduced transpiration rates and relative water content. Furthermore, ectopic expression of MhNCED3 decreased Cl– accumulation and oxidative damage, and up-regulated the expression levels of AtCLCc (chloride channel protein) and AtSLAH3 (slow anion channel 1 homolog 3) genes in Arabidopsis. These observations suggest that MhNCED3 has critical role in enhancing plant tolerance to Cl– stress by reducing Cl– accumulation.


      PubDate: 2015-03-06T13:55:02Z
       
  • Reduction of pyruvate orthophosphate dikinase activity is associated with
           high temperature-induced chalkiness in rice grains
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Zhen-mei Wang , Hai-xia Li , Xiong-feng Liu , Ying He , Han-lai Zeng
      Global warming affects both rice (Oryza sativa) yields and grain quality. Rice chalkiness due to high temperature during grain filling would lower the grain quality. The biochemical and molecular mechanisms responsible for the increased occurrence of chalkiness under high temperature are not fully understood. Previous research suggested that cytosolic pyruvate orthophosphate dikinase (cyPPDK, EC 2.7.9.1) in rice modulates carbon metabolism. The objective of this study was to determine the relationship between cyPPDK and high temperature-induced chalkiness. High temperature treatments were applied during the grain filling of two rice cultivars (9311 and TXZ-25) which had different sensitivity of chalkiness to high temperature. Chalkiness was increased significantly under high temperature treatment, especially for TXZ-25. A shortened grain filling duration and a decreased grain weight in both cultivars were caused by high temperature treatment. A reduction in PPDK activities due to high temperature was observed during the middle and late grain filling periods, accompanied by down regulated cyPPDK mRNA and protein levels. The temperature effects on the developmental regulation of PPDK activity were confirmed at transcription, translation and post-translational levels. PPDK activities were insensitive to variation in PPDK levels, suggesting the rapid phosphorylation mechanism of this protein. The two varieties showed similar responses to the high temperature treatment in both PPDK activities and chalkiness. We concluded that high temperature-induced chalkiness was associated with the reduction of PPDK activity.


      PubDate: 2015-03-06T13:55:02Z
       
  • A wheat lipid transfer protein (TdLTP4) promotes tolerance to abiotic and
           biotic stress in Arabidopsis thaliana
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Hela Safi , Walid Saibi , Meryem Mrani Alaoui , Abdelaziz Hmyene , Khaled Masmoudi , Moez Hanin , Faïçal Brini
      Lipid transfer proteins (LTPs) are members of the family of pathogenesis-related proteins (PR-14) that are believed to be involved in plant defense responses. In this study, we report the isolation and characterization of a novel gene TdLTP4 encoding an LTP protein from durum wheat [Triticum turgidum L. subsp. Durum Desf.]. Molecular Phylogeny analyses of wheat TdLTP4 gene showed a high identity to other plant LTPs. Predicted three-dimensional structural model revealed the presence of six helices and nine loop turns. Expression analysis in two local durum wheat varieties with marked differences in salt and drought tolerance, revealed a higher transcript accumulation of TdLTP4 under different stress conditions in the tolerant variety, compared to the sensitive one. The overexpression of TdLTP4 in Arabidopsis resulted in a promoted plant growth under various stress conditions including NaCl, ABA, JA and H2O2 treatments. Moreover, the LTP-overexpressing lines exhibit less sensitivity to jasmonate than wild-type plants. Furthermore, detached leaves from transgenic Arabidopsis expressing TdLTP4 gene showed enhanced fungal resistance against Alternaria solani and Botrytis cinerea. Together, these data provide the evidence for the involvement of TdLTP4 gene in the tolerance to both abiotic and biotic stresses in crop plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Simultaneous functions of the installed DAS/DAK formaldehyde-assimilation
           pathway and the original formaldehyde metabolic pathways enhance the
           ability of transgenic geranium to purify gaseous formaldehyde polluted
           environment
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Shengen Zhou , Sunqin Xiao , Xiuxia Xuan , Zhen Sun , Kunzhi Li , Limei Chen
      The overexpression of dihydroxyacetone synthase (DAS) and dihydroxyacetone kinase (DAK) from methylotrophic yeasts in chloroplasts created a photosynthetic formaldehyde (HCHO)-assimilation pathway (DAS/DAK pathway) in transgenic tobacco. Geranium has abilities to absorb and metabolize HCHO. Results of this study showed that the installed DAS/DAK pathway functioning in chloroplasts greatly enhanced the role of the Calvin cycle in transgenic geranium under high concentrations of gaseous HCHO stress. Consequently, the yield of sugars from HCHO-assimilation increased approximately 6-fold in transgenic geranium leaves, and concomitantly, the role of three original HCHO metabolic pathways reduced, leading to a significant decrease in formic acid, citrate and glycine production from HCHO metabolism. Although the role of three metabolic pathways reduced in transgenic plants under high concentrations of gaseous HCHO stress, the installed DAS/DAK pathway could still function together with the original HCHO metabolic pathways. Consequently, the gaseous HCHO-resistance of transgenic plants was significantly improved, and the generation of H2O2 in the transgenic geranium leaves was significantly less than that in the wild type (WT) leaves. Under environmental-polluted gaseous HCHO stress for a long duration, the stomata conductance of transgenic plants remained approximately 2-fold higher than that of the WT, thereby increasing its ability to purify gaseous HCHO polluted environment.


      PubDate: 2015-03-06T13:55:02Z
       
  • Systematic mining of salt-tolerant genes in halophyte-Zoysia matrella
           through cDNA expression library screening
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Yu Chen , Junqin Zong , Zhiqun Tan , Lanlan Li , Baoyun Hu , Chuanming Chen , Jingbo Chen , Jianxiu Liu
      Though a large number of salt-tolerant genes were identified from Glycophyte in previous study, genes involved in salt-tolerance of halophyte were scarcely studied. In this report, an important halophyte turfgrass, Zoysia matrella, was used for systematic excavation of salt-tolerant genes using full-length cDNA expression library in yeast. Adopting the Gateway-compatible vector system, a high quality entry library was constructed, containing 3 × 106 clones with an average inserted fragments length of 1.64 kb representing a 100% full-length rate. The yeast expression library was screened in a salt-sensitive yeast mutant. The screening yielded dozens of salt-tolerant clones harboring 16 candidate salt-tolerant genes. Under salt-stress condition, these 16 genes exhibited different transcription levels. According to the results, we concluded that the salt-tolerance of Z. matrella might result from known genes involved in ion regulation, osmotic adjustment, as well as unknown pathway associated with protein folding and modification, RNA metabolism, and mitochondrial membrane translocase, etc. In addition, these results shall provide new insight for the future researches with respect to salt-tolerance.


      PubDate: 2015-03-06T13:55:02Z
       
  • Transcription factors and anthocyanin genes related to low-temperature
           tolerance in rd29A:RdreB1BI transgenic strawberry
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Xianbin Gu , Yahua Chen , Zhihong Gao , Yushan Qiao , Xiuyun Wang
      Dehydration-responsive element-binding (DREB) transcription factors play critical roles in plant stress responses and signal transduction. To further understand how DREB regulates genes expression to promote cold-hardiness, Illumina/Solexa sequencing technology was used to compare the transcriptomes of non-transgenic and rd29A:RdreB1BI transgenic strawberry plants exposed to low temperatures. Approximately 3.5 million sequence tags were obtained from non-transgenic (NT) and transgenic (T) strawberry untreated (C) or low-temperature treated (LT) leaf samples. Over 1000 genes were differentially expressed between the NT-C and T-C plants, and also the NT-C and NT-LT, as well as the T-C and T-LT plants. Analysis of the genes up-regulated following low-temperature treatment revealed that the majority are linked to metabolism, biosynthesis, transcription and signal transduction. Uniquely up-regulated transcription factors as well as anthocyanin biosynthetic pathway genes are discussed. Accumulation of anthocyanin in the stolon and the base of the petiole differed between non-treated NT and T plants, and this correlated with gene expression patterns. The differentially expressed genes that encode transcription factors and anthocyanin enzymes may contribute to the cold hardiness of RdreB1BI transgenic strawberry. The transcriptome data provide a valuable resource for further studies of strawberry growth and development and DREB-mediated gene regulation under low-temperature stress.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • Physiological changes in fruit ripening caused by overexpression of tomato
           SlAN2, an R2R3-MYB factor
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Xia Meng , Dongyue Yang , Xiaodong Li , Shuya Zhao , Na Sui , Qingwei Meng
      The R2R3-MYB protein SlAN2 has long been thought to be a positive regulator of anthocyanin accumulation. To investigate the role of SlAN2, we have previously overexpressed the gene in tomato. In this work, we analysed physiological characters of the transgenic plants during the fruit ripening. We show that fruits of transformants overexpressing SlAN2 displayed an orange colour, fast softening and elevated ethylene production. Overexpression of SlAN2 resulted in reduction of carotenoid levels via alteration of flux through the carotenoid pathway, elevated ethylene synthesis mainly via upregulation of ethylene biosynthesis genes, and early softening of fruits. We also found that the transcript level of SlRIN, an important ripening-related gene, was up-regulated in transgenic fruits. These results suggest that SlAN2 acts as an important regulator of fruit ripening.


      PubDate: 2015-03-06T13:55:02Z
       
  • Expression of an exogenous 1-aminocyclopropane-1-carboxylate deaminase
           gene in psychrotolerant bacteria modulates ethylene metabolism and cold
           induced genes in tomato under chilling stress
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Parthiban Subramanian , Ramasamy Krishnamoorthy , Mak Chanratana , Kiyoon Kim , Tongmin Sa
      The role of stress induced ethylene under low temperature stress has been controversial and hitherto remains unclear. In the present study, 1-aminocyclopropane-1-carboxylate deaminase (ACCD) gene, acdS expressing mutant strains were generated from ACCD negative psychrotolerant bacterial strains Flavobacterium sp. OR306 and Pseudomonas frederiksbergensis OS211, isolated from agricultural soil during late winter. After transformation with plasmid pRKACC which contained the acdS gene, both the strains were able to exhibit ACCD activity in vitro. The effect of this ACCD under chilling stress with regards to ethylene was studied in tomato plants inoculated with both acdS expressing and wild type bacteria. On exposing the plants to one week of chilling treatment at 12/10 °C, it was found that stress ethylene, ACC accumulation and ACO activity which are markers of ethylene stress, were significantly reduced in plants inoculated with the acdS gene transformed mutants. In case of plants inoculated with strain OS211-acdS, ethylene emission, ACC accumulation and ACO activity was significantly reduced by 52%, 75.9% and 23.2% respectively compared to uninoculated control plants. Moreover, expression of cold induced LeCBF1 and LeCBF3 genes showed that these genes were significantly induced by the acdS transformed mutants in addition to reduced expression of ethylene-responsive transcription factor 13 (ETF-13) and ACO genes. Induced expression of LeCBF1 and LeCBF3 in plants inoculated with acdS expressing mutants compared to wild type strains show that physiologically evolved stress ethylene and its transcription factors play a role in regulation of cold induced genes as reported earlier in the literature.


      PubDate: 2015-03-06T13:55:02Z
       
  • Involvement of an extracellular fungus laccase in the flavonoid metabolism
           in Citrus fruits inoculated with Alternaria alternata
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Licinio Díaz , José Antonio Del Río , Manuela Pérez-Gilabert , Ana Ortuño
      Fungi of the genus Alternaria are responsible for substantial pre-harvest losses in Citrus. In this study a degradative metabolism of flavonoids (flavanones, flavones and polymethoxyflavones) was observed when ‘Fortune’ mandarin, Citrus limon and Citrus paradisi, fruits were inoculated with Alternaria alternata, a pre-harvest pathogenic fungus. Associated to this flavonic metabolism the de novo synthesis of the phytoalexin scoparone was detected. This metabolism of flavonoids is caused by an extracellular fungus laccase. The kinetic characterisation of this enzyme revealed that the activity was induced by Citrus flavonoids and was dependent on flavonoid concentrations. The enzyme exhibited a Km of 1.9 mM using ABTS as substrate with an optimum pH of 3.5 in citrate buffer 100 mM. The enzyme is active between 15 and 45 °C, the optimum temperature being around 35 °C, although 50% of the initial activity is lost after 45 min at 35 °C. The A. alternata laccase was inhibited by 0.5 mM l-cysteine and by caffeic acid. Study of the substrate specificity of this enzyme revealed that Citrus flavonoids are substrates of A. alternata laccase. These results suggest that the laccase enzyme could be involved in the pathogenesis of A. alternata in Citrus.


      PubDate: 2015-03-06T13:55:02Z
       
  • Heterologous expression of IbMYB1a by different promoters exhibits
           different patterns of anthocyanin accumulation in tobacco
    • Abstract: Publication date: April 2015
      Source:Plant Physiology and Biochemistry, Volume 89
      Author(s): Chul Han An , Ki-Won Lee , Sang-Hoon Lee , Yu Jeong Jeong , Su Gyoung Woo , Hyokon Chun , Youn-Il Park , Sang-Soo Kwak , Cha Young Kim
      We previously reported that the transient and stable expression of IbMYB1a produced anthocyanin pigmentation in tobacco leaves and transgenic Arabidopsis plants, respectively. To further determine the effects of different promoters on the expression of IbMYB1a and anthocyanin production, we generated and characterized stably transformed tobacco (Nicotiana tabacum SR1) plants expressing IbMYB1a under the control of three different promoters. We compared the differences in anthocyanin accumulation patterns and phenotypic features of the leaves of these transgenic tobacco plants during growth. Expression of IbMYB1a under the control of these three different promoters led to a remarkable variation in anthocyanin pigmentation in tobacco leaves. The anthocyanin contents of the leaves of the SPO-IbMYB1a-OX (SPO-M) line were higher than those of the SWPA2-IbMYB1a-OX (SPA-M) and 35S-IbMYB1a-OX (35S-M) lines. High levels of anthocyanin pigments negatively affected plant growth in the SPO-M lines, resulting delayed growth and, occasionally, a stunted phenotype. Furthermore, HPLC analysis revealed that transcriptional regulation of IbMYB1a led to the production of cyanidin-based anthocyanins in the tobacco plants. In addition, RT-PCR analysis revealed that IbMYB1a expression induced the up-regulation of several structural genes in the anthocyanin biosynthetic pathway, including DFR and ANS. Differential expression levels of IbMYB1a under the control of different promoters were highly correlated with the expression levels of the structural genes, thereby affecting anthocyanin production levels. These results indicate that IbMYB1a positively controls the expression of multiple anthocyanin biosynthetic genes and anthocyanin accumulation in heterologous tobacco plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Populus×canescens grown on Cr-rich tannery waste: Comparison of leaf
           and root biochemical and proteomic responses
    • Abstract: Publication date: May 2015
      Source:Plant Physiology and Biochemistry, Volume 90
      Author(s): Agata Zemleduch-Barylska , Gabriela Lorenc-Plucińska
      Treatment of tannery effluents generates large amounts of sediments containing concentrated doses of metals (mainly chromium). Such waste is most commonly disposed of by landfilling, which is hazardous to the ecosystem due to Cr leaching. Afforestation of disposal sites with fast growing trees could stabilize contaminants in the soil and prevent them from spreading. The aim of this study was to examine the adaptation of Populus × canescens Sm. to tannery waste using biochemical and proteomic methods. We analyzed changes in the leaves and fine roots of poplar planted in soil or tannery waste. We found no obvious symptoms of metal stress, such as: elevated hydrogen peroxide levels or lipid peroxidation, but we observed activation of many elements of antioxidative system. Comparison of 2-DE protein profiles of leaves and fine roots from poplar grown on soil or tannery waste revealed increased expression of glycolytic enzymes and proteins involved in the synthesis of cell wall components, changes in the levels of proteins associated with photosynthesis, stress-related proteins, proteasome subunits and methionine biosynthesis enzymes. This experiment demonstrated that proteomic analysis has the potential to link the effects of Cr-rich tannery waste with biological consequences.


      PubDate: 2015-03-06T13:55:02Z
       
  • Ultraviolet-B protection of ascorbate and tocopherol in plants related
           with their function on the stability on carotenoid and phenylpropanoid
           compounds
    • Abstract: Publication date: May 2015
      Source:Plant Physiology and Biochemistry, Volume 90
      Author(s): Yinan Yao , Jingjing You , Yongbin Ou , Jinbiao Ma , Xiuli Wu , Gang Xu
      Ascorbate and tocopherol are important hydrophilic or lipophilic antioxidants in plants, while their crucial roles in the antioxidant defense system under ultraviolet B radiation were not well understood. The mutants of Arabidopsis thaliana deficient in ascorbate (vtc1 and vtc2) or tocopherol (vte1) were used to analyze their physiological, biochemical and metabolic change in responses to Ultraviolet B radiation. Results showed that loss of either ascorbate or tocopherol caused reduction in phenylpropanoid and flavonol glycosides compounds, as well as reduction in superoxide dismutase activity and total cellular antioxidant capacity. This ultimately led to higher oxidative stress as well as lower levels of photosynthetic pigments (carotenoid and chlorophyll) and CO2 assimilation rate in the vtc1, vtc2, and vte1 mutants than the wild type under UV-B radiation, besides unstable early light-induced protein (ELIP1) in those mutants. On the other hand, the loss of tocopherol in vte1 mutants was compensated by the increase of zeaxanthin and anthocyanin contents, which armed vte1 mutants with higher heat dissipation capacity in PS II and higher antioxidative capacity than vtc mutants. Consequently the tolerance to UV-B radiation were much higher in vte1 mutant than in vtc mutants, furthermore, PS II function and light harvesting protein (LHCb1) abundance were reduced only in ascorbate-deficient mutant relative to wild type. Our results suggested that the ascorbate and tocopherol provided not only direct protective function against UV-B radiation but also indirect effects by influencing other protective system, in particular by affecting the stability of various carotenoid and phenylpropanoid compounds.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • Cultivar specific metabolic changes in grapevines berry skins in relation
           to deficit irrigation and hydraulic behavior
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Uri Hochberg , Asfaw Degu , Grant R. Cramer , Shimon Rachmilevitch , Aaron Fait
      Deficit irrigation techniques are widely used in commercial vineyards. Nevertheless, varieties respond differently to water availability, prompting the need to elucidate the physiological and molecular mechanisms involved in the interactions between genotypes and their environment. In the present study, the variability in berry metabolism under deficit irrigation was investigated in the field on Shiraz and Cabernet Sauvignon (CS), known for their hydraulic variability. Berry skin metabolite profiling of the two cultivars was performed by parallel GC–MS and LC-MS at four development stages. Under similar irrigation, the cultivars differed in stomata regulation. In response to water deficit, CS exhibited lessened loss in berry weight and milder metabolic alteration of berry-skin primary metabolites, as compared with Shiraz. The metabolic stress responses were shown to depend on berry phenology. Characteristic metabolic changes included a decrease in amino acids and TCA cycle intermediates from veraison onward. In contrast, water deficit induced the accumulation of stress-related metabolites such as: proline, beta-alanine, raffinose, nicotinate and ascorbate, to a greater extent in Shiraz. Polyphenol metabolism in response to water stress also underwent significant changes, unique to each cultivar. Results suggest a link between the vine hydraulics and water-deficit driven changes in the berry skin metabolism, with significant consequences on the metabolic composition of the fruit.


      PubDate: 2015-03-06T13:55:02Z
       
  • Mechanism of artemisinin phytotoxicity action: Induction of reactive
           oxygen species and cell death in lettuce seedlings
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Zhi-Qiang Yan , Dan-Dan Wang , Lan Ding , Hai-Yan Cui , Hui Jin , Xiao-Yan Yang , Jian-She Yang , Bo Qin
      Artemisinin has been recognized as an allelochemical that inhibits growth of several plant species. However, its mode of action is not well clarified. In this study, the mechanism of artemisinin phytotoxicity on lettuce seedlings was investigated. Root and shoot elongation of lettuce seedlings were inhibited by artemisinin in a concentration-dependent manner. The compound effectively arrested cell division and caused loss of cell viability in root tips of lettuce. Overproduction of reactive oxygen species (ROS) was induced by artemisinin. Lipid peroxidation, proline overproduction and reduction of chlorophyll content in lettuce seedlings were found after treatments. These results suggested that artemisinin could induce ROS overproduction, which caused membrane lipids peroxidation and cell death, and impacted mitosis and physiological processes, resulting in growth inhibition of receptor plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Enhanced excision repair and lack of PSII activity contribute to higher UV
           survival of Chlamydomonas reinhardtii cells in dark
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Vishalsingh R. Chaudhari , Aniket Vyawahare , Swapan K. Bhattacharjee , Basuthkar J. Rao
      Plant cells are known to differentiate their responses to stress depending up on the light conditions. We observed that UVC sensitive phenotype of light grown asynchronous Chlamydomonas reinhardtii culture (Light culture: LC) can be converted to relatively resistant form by transfer to dark condition (Dark culture: DC) before UVC exposure. The absence of photosystem II (PSII) function, by either atrazine treatment in wild type or in D1 (psbA) null mutant, conferred UV protection even in LC. We provide an indirect support for involvement of reactive oxygen species (ROS) signalling by showing higher UV survival on exposures to mild dose of H2O2 or Methyl Viologen. Circadian trained culture also showed a rhythmic variation in UV sensitivity in response to alternating light–dark (12 h:12 h) entrainment, with maximum UV survival at the end of 12 h dark and minimum at the end of 12 h light. This rhythm failed to maintain in “free running” conditions, making it a non-circadian phenotype. Moreover, atrazine strongly inhibited rhythmic UV sensitivity and conferred a constitutively high resistance, without affecting internal circadian rhythm marker expression. Dampening of UV sensitivity rhythm in Thymine-dimer excision repair mutant (cc-888) suggested the involvement of DNA repair in this phenomenon. DNA excision repair (ER) assays in cell-free extracts revealed that dark incubated cells exhibit higher ER compared to those growing in light, underscoring the role of ER in conferring differential UV sensitivity in dark versus light incubation. We suggest that multiple factors such as ROS changes triggered by differences in PSII activity, concomitant with differential ER efficiency collectively contribute to light–dark (12 h: 12 h) rhythmicity in C. reinhardtii UV sensitivity.


      PubDate: 2015-03-06T13:55:02Z
       
  • Water availability influences morphology, mycorrhizal associations, PSII
           efficiency and polyamine metabolism at early growth phase of Scots pine
           seedlings
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Riina Muilu-Mäkelä , Jaana Vuosku , Esa Läärä , Markku Saarinen , Juha Heiskanen , Hely Häggman , Tytti Sarjala
      Scots pine (Pinus sylvestris L.) is adapted to various soil types with diverse water availabilities. However, Scots pine seedlings are vulnerable to abiotic stress during the early growth, when they may be exposed to both dry and wet conditions. Here, we focused on the above and below ground coping strategies of Scots pine seedlings under controlled wet, optimal and dry soil conditions by investigating morphological traits including seedling biomass, number of root tips, proportion of mycorrhizal root tips and brown needles. In addition, we studied metabolic and physiological responses including gene expression involved in biosynthesis and catabolism of polyamines (PA), PSII efficiency and the expression of the catalase (CAT) late-embryogenesis abundant protein (LEA), pyruvate decarboxylase (PDC), glutamate-cysteine ligase (GCL) and glutathione synthetase (GS) genes. We found that seedlings invested in shoots by maintaining stable shoot water content and high PSII efficiency under drought stress. Free and soluble conjugated putrescine (Put) accumulated in needles under drought stress, suggesting the role of Put in protection of photosynthesizing tissues. However, the expression of the PA biosynthesis genes, arginine decarboxylase (ADC), spermidine synthase (SPDS) and thermospermine synthase (ACL5) was not affected under drought stress whereas catabolizing genes diamino oxidase (DAO) and polyamine oxidase (PAO) were down-regulated in shoots. The morphology of the roots was affected by peat water content. Furthermore, both drought stress and water excess restricted the seedling ability to sustain a symbiotic relationship. The consistent pattern of endogenous PAs seems to be advantageous to the Scots pine seedlings also under stress conditions.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • RPN1a, a subunit of the 26S proteasome, controls trichome development in
           Arabidopsis
    • Abstract: Publication date: March 2015
      Source:Plant Physiology and Biochemistry, Volume 88
      Author(s): Dashi Yu , Feng Yu , Changqing Du , Xiushan Li , Xiaoying Zhao , Xuanming Liu
      The ubiquitin-mediated 26S proteasome pathway (UPS) is of great importance to plant growth and development. Previously research showed that a subunit of the 26S proteasome, named RPN1a, was involved in trichome's branching in Arabidopsis. Mutation in RPN1a give rise to more trichome branches on leaves. Here, we found that T-DNA insertion mutation in RPN1a resulted in increased trichome branches on main stem, and trichome number on rosette leaves and the main stem compared with the wild type plant. Expression analysis results showed that the transcription levels of ZFP6, ZFP5, GIS, GL1, GL2, GL3, TTG1 and MYB23, which promote trichome initiation, were up-regulated in the rpn1a mutant, and expression of FRC4, which is responsible for increased trichome branching, was also increased in the rpn1a mutant. Moreover, the mRNA expression level of RPN1a was significantly repressed by GA (gibberellin) and CK (cytokinin) treatment, which are two important phytohormones that play essential roles in trichome development. These results demonstrate that RPN1a may be involved in trichome development through the GA and CK signaling pathways.


      PubDate: 2015-03-06T13:55:02Z
       
  • Salicylic-acid elicited phospholipase D responses in Capsicum chinense
           cell cultures
    • Abstract: Publication date: Available online 27 February 2015
      Source:Plant Physiology and Biochemistry
      Author(s): B.A. Rodas-Junco , J.A. Muñoz-Sánchez , Felipe Vázquez-Flota , S.M.T. Hernández-Sotomayor
      The plant response to different stress types can occur through stimulus recognition and the subsequent signal transduction through second messengers that send information to the regulation of metabolism and the expression of defense genes. The phospholipidic signaling pathway forms part of the plant response to several phytoregulators, such as salicylic acid (SA), which has been widely used to stimulate secondary metabolite production in cell cultures. In this work, we studied the effects of SA treatment on [32-P]Pi phospholipid turnover and phospholipase D (PLD) activity using cultured Capsicum chinense cells. In cultured cells, the PIP2 turnover showed changes after SA treatment, while the most abundant phospholipids (PLs), such as phosphatidylcholine (PC), did not show changes during the temporal course. SA treatment significantly increased phosphatidic acid (PA) turnover over time compared to control cells. The PA accumulation in cells treated with 1-butanol showed a decrease in messengers; at the same time, there was a 1.5-fold increase in phosphatidylbutanol. These results suggest that the participation of the PLD pathway is a source of PA production, and the activation of this mechanism may be important in the cell responses to SA treatment.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • Differences in volatile profiles of Cabernet Sauvignon grapes grown in two
           distinct regions of China and their responses to weather conditions
    • Abstract: Publication date: Available online 26 February 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Xiao-Qing Xu , Bin Liu , Bao-Qing Zhu , Yi-Bin Lan , Yuan Gao , Dong Wang , Malcolm J. Reeves , Chang-Qing Duan
      Volatile compounds are considered important for plants to communicate with each other and interact with their environments. Most wine-producing regions in China feature a continental monsoon climate with hot-wet summers and dry-cold winters, giving grapes markedly different growing environments compared to the Mediterranean or oceanic climates described in previous reports. This study focused on comparing the volatile profiles of Vitis vinifera L. cv. Cabernet Sauvignon berries from two regions with distinct climate characteristics: Changli has a warm and semi-humid summer, and Gaotai has a cool-arid summer and a cold winter. The relationship between meteorological metrics and the concentrations of grape volatiles was also examined. In harvested grapes, benzyl alcohol, phenylethyl alcohol, 1-hexanol and 1-octen-3-ol were more abundant in the Changli berries, while hexanal, heptanal, 2-methoxy-3-isobutylpyrazine, and (E)-β-damascenone presented higher levels in the Gaotai berries. The fluctuation in the accumulation of volatile compounds observed during berry development was closely correlated with variations in short-term weather (weather in a week), especially rainfall. The concentration of some volatiles, notably aliphatic aldehydes, was significantly related to diurnal temperature differences. The variability during berry development of concentrations for compounds such as C6 volatile compounds, 2-methoxy-3-isobutylpyrazine and (E)-β-damascenone strongly depended upon weather conditions. This work expands our knowledge about the influence of continental monsoon climates on volatile compounds in developing grape berries. It will also improve the comprehension of the plant response to their surrounding environments through the accumulation of volatiles. The results will help growers to alter viticultural practices according to local conditions to improve the aromatic quality of grapes.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • The effects of UV radiation during the vegetative period on antioxidant
           compounds and postharvest quality of broccoli (Brassica oleracea L.)
    • Abstract: Publication date: Available online 24 February 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Yasin Topcu , Adem Dogan , Zehra Kasimoglu , Hilal Sahin-Nadeem , Ersin Polat , Mustafa Erkan
      In this study, the effects of supplementary UV radiation during the vegetative period on antioxidant compounds, antioxidant activity and postharvest quality of broccoli heads during long term storage was studied. The broccolis were grown under three different doses of supplementary UV radiation (2.2, 8.8 and 16.4 kJ/m2/day) in a soilless system in a glasshouse. Harvested broccoli heads were stored at 0 °C in modified atmosphere packaging for 60 days. The supplementary UV radiation (280–315 nm) during the vegetative period significantly decreased total carotenoid, the chlorophyll a and chlorophyll b content but increased the ascorbic acid, total phenolic and flavonoid contents of broccolis. All supplementary UV treatments slightly reduced the antioxidant activity of the broccolis, however, no remarkable change was observed between 2.2 and 8.8 kJ/m2 radiation levels. The sinigrin and glucotropaeolin contents of the broccolis were substantially increased by UV treatments. The prolonged storage period resulted in decreased ascorbic acid, total phenolic and flavonoid contents, as well as antioxidant activity. Discoloration of the heads, due to decreased chlorophyll and carotenoid contents, was also observed with prolonged storage duration. Glucosinolates levels showed an increasing tendency till the 45th day of storage, and then their levels started to decline. The weight loss of broccoli heads during storage progressively increased with storage time in all treatments. Total soluble solids, solids content and titratable acidity decreased continuously during storage. Titratable acidity was not affected by UV radiation doses during the storage time whereas soluble solids and solids content (dry matter) were significantly affected by UV doses. Supplementary UV radiation increased the lightness (L*) and chroma (C*) values of the broccoli heads. Pre-harvest UV radiation during vegetative period seems to be a promising tool for increasing the beneficial health components of broccolis.


      PubDate: 2015-03-06T13:55:02Z
       
  • The vegetative buds of Salix myrsinifolia are responsive to elevated UV-B
           and temperature
    • Abstract: Publication date: Available online 24 February 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Unnikrishnan Sivadasan , Tendry R. Randriamanana , Riitta Julkunen-Tiitto , Line Nybakken
      The predicted rise in temperature and variable changes in ultraviolet-B radiation will have marked effects on plant growth and metabolism. Different vegetative parts of trees have been studied to detect the impacts of enhanced temperature and UV-B, but the effects on buds have rarely been considered. In the present study, Salix myrsinifolia clones were subjected to enhanced UV-B and temperature over two growing seasons starting from 2009, and measured springtime bud development and concentrations of phenolic compounds. In 2010 and 2011 the buds under increased temperature were up to 30% longer than those in control plots. On the other hand, UV-B combined with elevated temperature significantly decreased bud length by 4–5% in 2010. This effect was stronger in males than in females. The vegetative buds contained high constitutive amounts of chlorogenic acid derivatives, which may explain the weak increase in hyperin and chlorogenic acid that are usual UV-B sheltering compounds. The elevated temperature treatment significantly increased salicin content (about 18% in males and 22% in females), while triandrin concentration decreased by only 50% in females. Our results indicate that vegetative bud size is highly affected by seasonal temperature, while UV-B induced a weaker and transient effect.


      PubDate: 2015-03-06T13:55:02Z
       
  • Carbon allocation from source to sink leaf tissue in relation to flavonoid
           biosynthesis in variegated Pelargonium zonale under UV-B radiation and
           high PAR intensity
    • Abstract: Publication date: Available online 2 February 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Marija Vidović , Filis Morina , Sonja Milić , Andreas Albert , Bernd Zechmann , Tomislav Tosti , Jana Barbro Winkler , Sonja Veljović Jovanović
      We studied the specific effects of high photosynthetically active radiation (PAR, 400–700 nm) and ecologically relevant UV-B radiation (0.90 W m−2) on antioxidative and phenolic metabolism by exploiting the green-white leaf variegation of Pelargonium zonale plants. This is a suitable model system for examining “source-sink” interactions within the same leaf. High PAR intensity (1350 μmol m−2 s−1) and UV-B radiation induced different responses in green and white leaf sectors. High PAR intensity had a greater influence on green tissue, triggering the accumulation of phenylpropanoids and flavonoids with strong antioxidative function. Induced phenolics, together with ascorbate, ascorbate peroxidase (APX, EC 1.11.1.11) and catalase (CAT, EC 1.11.1.6) provided efficient defense against potential oxidative pressure. UV-B-induced up-regulation of non-phenolic H2O2 scavengers in green leaf sectors was greater than high PAR-induced changes, indicating a UV-B role in antioxidative defense under light excess; on the contrary, minimal effects were observed in white tissue. However, UV-B radiation had greater influence on phenolics in white leaf sections compared to green ones, inducing accumulation of phenolic glycosides whose function was UV-B screening rather than antioxidative. By stimulation of starch and sucrose breakdown and carbon allocation in the form of soluble sugars from “source” (green) tissue to “sink” (white) tissue, UV-B radiation compensated the absence of photosynthetic activity and phenylpropanoid and flavonoid biosynthesis in white sectors.


      PubDate: 2015-03-06T13:55:02Z
       
  • Arabidopsis thaliana natural variation reveals connections between UV
           radiation stress and plant pathogen-like defense responses
    • Abstract: Publication date: Available online 2 February 2015
      Source:Plant Physiology and Biochemistry
      Author(s): Thomas Piofczyk , Ganga Jeena , Ales Pecinka
      UV radiation is a ubiquitous component of solar radiation that affects plant growth and development. Here we studied growth related traits of 345 Arabidopsis thaliana accessions in response to UV radiation stress. We analyzed the genetic basis of this natural variation by genome-wide association studies, which suggested a specific candidate genomic region. RNA-sequencing of three sensitive and three resistant accessions combined with mutant analysis revealed five large effect genes. Mutations in PHE AMMONIA LYASE 1 (PAL1) and putative kinase At1g76360 rendered Arabidopsis hypersensitive to UV stress, while loss of function from putative methyltransferase At4g22530, NOVEL PLANT SNARE 12 (NPSN12) and defense gene ACTIVATED DISEASE RESISTANCE 2 (ADR2) conferred higher UV stress resistance. Three sensitive accessions showed strong ADR2 transcriptional activation, accumulation of salicylic acid (SA) and dwarf growth upon UV stress, while these phenotypes were much less affected in resistant plants. The phenotype of sensitive accessions resembles autoimmune reactions due to overexpression of defense related genes, and suggests that natural variation in response to UV radiation stress is driven by pathogen-like responses in Arabidopsis.


      PubDate: 2015-03-06T13:55:02Z
       
  • Editorial Board
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87




      PubDate: 2015-03-06T13:55:02Z
       
  • Sulfate resupply accentuates protein synthesis in coordination with
           nitrogen metabolism in sulfur deprived Brassica napus
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Qian Zhang , Bok-Rye Lee , Sang-Hyun Park , Rashed Zaman , Jean-Christophe Avice , Alain Ourry , Tae-Hwan Kim
      To investigate the regulatory interactions between S assimilation and N metabolism in Brassica napus, de novo synthesis of amino acids and proteins was quantified by 15N and 34S tracing, and the responses of transporter genes, assimilatory enzymes and metabolites pool involving in nitrate and sulfate metabolism were assessed under continuous sulfur supply, sulfur deprivation and sulfate resupply after 3 days of sulfur (S) deprivation. S-deprived plants were characterized by a strong induction of sulfate transporter genes, ATP sulfurylase (ATPS) and adenosine 5′-phosphosulfate reductase (APR), and by a repressed activity of nitrate reductase (NR) and glutamine synthetase (GS). Sulfate resupply to the S-deprived plants strongly increased cysteine, amino acids and proteins concentration. The increase in sulfate and cysteine concentration caused by sulfate resupply was not matched with the expression of sulfate transporters and the activity of ATPS and APR which were rapidly decreased by sulfate resupply. A strong induction of O-acetylserine(thiol)lyase (OASTL), NR and GS upon sulfate resupply was accompanied with the increase in cysteine, amino acids and proteins pool. Sulfate resupply resulted in a strong increase in de novo synthesis of amino acids and proteins, as evidenced by the increases in N and S incorporation into amino acids (1.8- and 2.4-fold increase) and proteins (2.2-and 6.3-fold increase) when compared to S-deprived plants. The results thus indicate that sulfate resupply followed by S-deprivation accelerates nitrate assimilation for protein synthesis.


      PubDate: 2015-03-06T13:55:02Z
       
  • Identification and expression of a stearoyl-ACP desaturase gene
           responsible for oleic acid accumulation in Xanthoceras sorbifolia seeds
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Na Zhao , Yuan Zhang , Qiuqi Li , Rufang Li , Xinli Xia , Xiaowei Qin , Huihong Guo
      Xanthoceras sorbifolia Bunge is an oilseed tree that grows well on barren lands in dry climate. Its seeds contain a large amount of oil rich in oleic acid (18:1Δ9) and linoleic acid (18:2Δ9, 12). However, the molecular regulation of oil biosynthesis in X. sorbifolia seeds is poorly understood. Stearoyl-ACP desaturase (SAD, EC 1.14.99.6) is a plastid-localized soluble desaturase that catalyzes the conversion of stearic acid (18:0) to oleic acid, which plays a key role in determining the ratio of saturated to unsaturated fatty acids. In this study, a full-length cDNA of XsSAD was isolated from developing X. sorbifolia embryos. The XsSAD open reading frame had 1194-bp, encoding a polypeptide of 397 amino acids. XsSAD expression in Escherichia coli cells resulted in increased 18:1Δ9 level, confirming the biological activity of the enzyme encoded by XsSAD. XsSAD expression in Arabidopsis ssi2 mutants partially restored the morphological phenotype and effectively increased the 18:1Δ9 level. The levels of other unsaturated fatty acids synthesized with 18:1Δ9 as the substrate also increased to some degree. XsSAD in X. sorbifolia had a much higher expression in embryos than in leaves and petals. XsSAD expression also correlated well with the oleic acid, unsaturated fatty acid, and total fatty acid levels in developing embryos. These data suggested that XsSAD determined the synthesis of oleic acid and contributed to the accumulation of unsaturated fatty acid and total oil in X. sorbifolia seeds. A preliminary tobacco rattle virus-based virus-induced gene silencing system established in X. sorbifolia can also be helpful for further analyzing the functions of XsSAD and other oil synthesis-related genes in woody plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Growth, physiological adaptation, and gene expression analysis of two
           Egyptian rice cultivars under salt stress
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Ahmad Mohammad M. Mekawy , Dekoum V.M. Assaha , Hiroyuki Yahagi , Yuma Tada , Akihiro Ueda , Hirofumi Saneoka
      Abiotic stressors, such as high salinity, greatly affect plant growth. In an attempt to explore the mechanisms underlying salinity tolerance, physiological parameters of two local Egyptian rice (Oryza sativa L.) cultivars, Sakha 102 and Egyptian Yasmine, were examined under 50 mM NaCl stress for 14 days. The results indicate that Egyptian Yasmine is relatively salt tolerant compared to Sakha 102, and this was evident in its higher dry mass production, lower leaf Na+ levels, and enhanced water conservation under salt stress conditions. Moreover, Egyptian Yasmine exhibited lower Na+/K+ ratios in all tissues examined under salinity stress. The ability to maintain such traits seemed to differ in the leaves and roots of Egyptian Yasmine, and the root K+ content was much higher in Egyptian Yasmine than in Sakha 102. In order to understand the basis for these differences, we studied transcript levels of genes encoding Na+ and K+ transport proteins in different tissues. In response to salinity stress, Egyptian Yasmine showed induction of expression of some membrane transporter/channel genes that may contribute to Na+ exclusion from the shoots (OsHKT1;5), limiting excess Na+ entry into the roots (OsLti6b), K+ uptake (OsAKT1), and reduced expression of a Na+ transporter gene (OsHKT2;1). Therefore, the active regulation of genes related to Na+ transport at the transcription level may be involved in salt tolerance mechanisms of Egyptian Yasmine, and these mechanisms offer the promise of improved salinity stress tolerance in local Egyptian rice genotypes.


      PubDate: 2015-03-06T13:55:02Z
       
  • Euphorbia characias latex: Micromorphology of rubber particles and rubber
           transferase activity
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Delia Spanò , Francesca Pintus , Francesca Esposito , Danilo Loche , Giovanni Floris , Rosaria Medda
      We have recently characterized a natural rubber in the latex of Euphorbia characias. Following that study, we here investigated the rubber particles and rubber transferase in that Mediterranean shrub. Rubber particles, observed by scanning electron microscopy, are spherical in shape with diameter ranging from 0.02 to 1.2 μm. Washed rubber particles exhibit rubber transferase activity with a rate of radiolabeled [14C]IPP incorporation of 4.5 pmol min−1 mg−1. Denaturing electrophoresis profile of washed rubber particles reveals a single protein band of 37 kDa that is recognized in western blot analysis by antibodies raised against the synthetic peptide whose sequence, DVVIRTSGETRLSNF, is included in one of the five regions conserved among cis-prenyl chain elongation enzymes. The cDNA nucleotide sequence of E. characias rubber transferase (GenBank JX564541) and the deduced amino acid sequence appear to be highly homologous to the sequence of several plant cis-prenyltransferases.


      PubDate: 2015-03-06T13:55:02Z
       
  • Molecular identification and characterization of the pyruvate
           decarboxylase gene family associated with latex regeneration and stress
           response in rubber tree
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Xiangyu Long , Bin He , Chuang Wang , Yongjun Fang , Jiyan Qi , Chaorong Tang
      In plants, ethanolic fermentation occurs not only under anaerobic conditions but also under aerobic conditions, and involves carbohydrate and energy metabolism. Pyruvate decarboxylase (PDC) is the first and the key enzyme of ethanolic fermentation, which branches off the main glycolytic pathway at pyruvate. Here, four PDC genes were isolated and identified in a rubber tree, and the protein sequences they encode are very similar. The expression patterns of HbPDC4 correlated well with tapping-simulated rubber productivity in virgin rubber trees, indicating it plays an important role in regulating glycometabolism during latex regeneration. HbPDC1, HbPDC2 and HbPDC3 had striking expressional responses in leaves and bark to drought, low temperature and high temperature stresses, indicating that the HbPDC genes are involve in self-protection and defense in response to various abiotic and biotic stresses during rubber tree growth and development. To understand ethanolic fermentation in rubber trees, it will be necessary to perform an in-depth study of the regulatory pathways controlling the HbPDCs in the future.


      PubDate: 2015-03-06T13:55:02Z
       
  • Plant-microorganism-soil interactions influence the Fe availability in the
           rhizosphere of cucumber plants
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Youry Pii , Alexander Penn , Roberto Terzano , Carmine Crecchio , Tanja Mimmo , Stefano Cesco
      Iron (Fe) is a very important element for plants, since it is involved in many biochemical processes and, often, for the low solubility of the natural Fe sources in soil, plants suffer from Fe – deficiency, especially when grown on calcareous soils. Among the numerous plant growth-promoting rhizobacteria (PGPR) that colonize the rhizosphere of agronomically important crops, Azospirillum brasilense has been shown to exert strong stimulating activities on plants, by inducing alterations of the root architecture and an improvement of mineral nutrition, which could result from an enhancement of ion uptake mechanisms as well as by increased bioavailability of nutrients. Some studies have also established that A. brasilense can act as biocontrol agent, by preventing the growth and/or virulence of phytopathogens, most likely through the production of microbial siderophores that sequester Fe from the soil. Despite microbial siderophores complexed with Fe could be an easily accessible Fe source for plants, the possible involvement of A. brasilense in improving Fe nutrition in plants suffering from the micronutrient deficiency has not been investigated yet. Within the present research, the characterization of the physiological and biochemical effects induced by Fe starvation and PGPR inoculation in cucumber plants (Cucumis sativus L. cv. Chinese Long) was carried out. The analyses of root exudates released by hydroponically grown plants highlighted that cucumber plants respond differently depending on the nutritional status. In addition, following the cultivation period on calcareous soil, also the root exudates found in the extracts suggested a peculiar behaviour of plants as a function of the treatment. Interestingly, the presence of the inoculum in soil allowed a faster recovery of cucumber plants from Fe-deficiency symptoms, i.e. increase in the chlorophyll content, in the biomass and in the Fe content of leaves. These observations might suggest a feasible application of A. brasilense in alleviating symptoms generated by Fe-limiting growth condition in cucumber plants.


      PubDate: 2015-03-06T13:55:02Z
       
  • Di-4-ANEPPDHQ, a fluorescent probe for the visualisation of membrane
           microdomains in living Arabidopsis thaliana cells
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Xiaoyu Zhao , Ruili Li , Cunfu Lu , František Baluška , Yinglang Wan
      Cholesterol-enriched microdomains, also called lipid rafts, are nanoscale membrane structures with a high degree of structural order. Since these microdomains play important roles in dynamic cytological events, such as cell signalling and membrane trafficking, the detection and tracking of microdomain behaviours are crucial to studies on modern membrane physiology. Currently, observation of microdomains is mostly based on the detection of specific raft-resident constituents using artificial cross-link fluorescent probes. However, only a few microdomain-specific fluorescent dyes are available for plant cell biology studies. In this study, the photophysical properties of di-4-ANEPPDHQ were analysed. The use of confocal laser scanning microscope (CLSM)-based methods in the visualisation of microdomains in living cells of Arabidopsis thaliana was assessed. The results confirmed that the generalised polarisation (GP) method can be used to quantitatively visualise the membrane orders in live plant cells. This dye was found to have low cytotoxicity in plant root epidermal cells and root hairs. These findings suggest that di-4-ANEPPDHQ is an appropriate tool for the visualisation of microdomains in living plant cells.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • The TOC159 mutant of Arabidopsis thaliana accumulates altered levels of
           saturated and polyunsaturated fatty acids
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Meshack Afitlhile , Morgan Fry , Samantha Workman
      We evaluated whether the TOC159 mutant of Arabidopsis called plastid protein import 2-2 (ppi2-2) accumulates normal levels of fatty acids, and transcripts of fatty acid desaturases and galactolipid synthesis enzymes. The ppi2-2 mutant accumulates decreased pigments and total fatty acid content. The MGD1 gene was downregulated and the mutant accumulates decreased levels of monogalactosyldiacylglycerol (MGDG) and 16:3, which suggests that the prokaryotic pathway was impaired in the mutant. The HY5 gene, which encodes long hypocotyl5 transcription factor, was upregulated in the mutant. The DGD1 gene, an HY5 target was marginally increased and the mutant accumulates digalactosyldiacylglycerol at the control level. The mutant had increased expression of 3-ketoacyl-ACP synthase II gene, which encodes a plastid enzyme that elongates 16:0 to 18:0. Interestingly, glycerolipids in the mutant accumulate increased levels of 18:0. A gene that encodes stearoyl-ACP desaturase (SAD) was expressed at the control level and 18:1 was increased, which suggest that SAD may be strongly regulated at the posttranscriptional level. The molar ratio of MGDG to bilayer forming plastid lipids was decreased in the cold-acclimated wild type but not in the ppi2-2 mutant. This indicates that the mutant was unresponsive to cold-stress, and is consistent with increased levels of 18:0, and decreased 16:3 and 18:3 in the ppi2-2 mutant. Overall, these data indicate that a defective Toc159 receptor impaired the synthesis of MGDG, and affected desaturation of 16 and 18-carbon fatty acids. We conclude that expression of the MGD1 gene and synthesis of MGDG are tightly linked to plastid biogenesis.


      PubDate: 2015-03-06T13:55:02Z
       
  • Lysine metabolism in antisense C-hordein barley grains
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Daiana Schmidt , Vanessa Rizzi , Salete A. Gaziola , Leonardo O. Medici , Eva Vincze , Marcin Kozak , Peter J. Lea , Ricardo A. Azevedo
      The grain proteins of barley are deficient in lysine and threonine due to their low concentrations in the major storage protein class, the hordeins, especially in the C-hordein subgroup. Previously produced antisense C-hordein transgenic barley lines have an improved amino acid composition, with increased lysine, methionine and threonine contents. The objective of the study was to investigate the possible changes in the regulation of key enzymes of the aspartate metabolic pathway and the contents of aspartate-derived amino acids in the nontransgenic line (Hordeum vulgare L. cv. Golden Promise) and five antisense C-hordein transgenic barley lines. Considering the amounts of soluble and protein-bound aspartate-derived amino acids together with the analysis of key enzymes of aspartate metabolic pathway, we suggest that the C-hordein suppression did not only alter the metabolism of at least one aspartate-derived amino acid (threonine), but major changes were also detected in the metabolism of lysine and methionine. Modifications in the activities and regulation of aspartate kinase, dihydrodipicolinate synthase and homoserine dehydrogenase were observed in most transgenic lines. Furthermore the activities of lysine α-ketoglutarate reductase and saccharopine dehydrogenase were also altered, although the extent varied among the transgenic lines.
      Graphical abstract image

      PubDate: 2015-03-06T13:55:02Z
       
  • Expression of potato S-adenosyl-l-methionine synthase (SbSAMS) gene
           altered developmental characteristics and stress responses in transgenic
           Arabidopsis plants
    • Abstract: Publication date: February 2015
      Source:Plant Physiology and Biochemistry, Volume 87
      Author(s): Sun Hee Kim , Sang Hyon Kim , Sasikumar Arunachalam Palaniyandi , Seung Hwan Yang , Joo-Won Suh
      S-adenosyl-l-methionine (SAM) synthase (SAMS) catalyze the biosynthesis of SAM, which is a precursor for ethylene and polyamines, and a methyl donor for a number of biomolecules. A full-length cDNA of SAMS from Solanum brevidens was expressed in Arabidopsis thaliana to study its physiological function. RT-PCR analysis showed that SbSAMS expression was enhanced significantly in S. brevidens leaves upon treatment with salt, mannitol, ethephon, IAA and ABA. The transgenic SbSAMS overexpression lines accumulated higher levels S-adenosyl homocysteine (SAHC) and ethylene concomitantly with increased SAM level. Expression levels of genes related to ethylene biosynthesis such as ACC synthase, but not polyamine biosynthesis genes were enhanced in SbSAMS overexpressing Arabidopsis lines. In addition, ABA responsive, wound and pathogen-inducible genes were upregulated in SbSAMS transgenic Arabidopsis plants. Transgenic Arabidopsis lines exhibited higher salt and drought stress tolerance compared to those of vector control. Based on these results we conclude that SbSAMS is expressed under abiotic stress to produce SAM as a broad-spectrum signal molecule to upregulate stress-related genes including ethylene and ABA biosynthetic pathway genes responsible for ABA, pathogen and wound responses.


      PubDate: 2015-03-06T13:55:02Z
       
 
 
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