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Journal Cover   Plant Molecular Biology
  [SJR: 1.842]   [H-I: 121]   [8 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1573-5028 - ISSN (Online) 0167-4412
   Published by Springer-Verlag Homepage  [2291 journals]
  • Comparison of CRISPR/Cas9 expression constructs for efficient targeted
           mutagenesis in rice
    • Abstract: The CRISPR/Cas9 system is an efficient tool used for genome editing in a variety of organisms. Despite several recent reports of successful targeted mutagenesis using the CRISPR/Cas9 system in plants, in each case the target gene of interest, the Cas9 expression system and guide-RNA (gRNA) used, and the tissues used for transformation and subsequent mutagenesis differed, hence the reported frequencies of targeted mutagenesis cannot be compared directly. Here, we evaluated mutation frequency in rice using different Cas9 and/or gRNA expression cassettes under standardized experimental conditions. We introduced Cas9 and gRNA expression cassettes separately or sequentially into rice calli, and assessed the frequency of mutagenesis at the same endogenous targeted sequences. Mutation frequencies differed significantly depending on the Cas9 expression cassette used. In addition, a gRNA driven by the OsU6 promoter was superior to one driven by the OsU3 promoter. Using an all-in-one expression vector harboring the best combined Cas9/gRNA expression cassette resulted in a much improved frequency of targeted mutagenesis in rice calli, and bi-allelic mutant plants were produced in the T0 generation. The approach presented here could be adapted to optimize the construction of Cas9/gRNA cassettes for genome editing in a variety of plants.
      PubDate: 2015-07-19
  • Sweet scents from good bacteria: Case studies on bacterial volatile
           compounds for plant growth and immunity
    • Abstract: Beneficial bacteria produce diverse chemical compounds that affect the behavior of other organisms including plants. Bacterial volatile compounds (BVCs) contribute to triggering plant immunity and promoting plant growth. Previous studies investigated changes in plant physiology caused by in vitro application of the identified volatile compounds or the BVC-emitting bacteria. This review collates new information on BVC-mediated plant-bacteria airborne interactions, addresses unresolved questions about the biological relevance of BVCs, and summarizes data on recently identified BVCs that improve plant growth or protection. Recent explorations of bacterial metabolic engineering to alter BVC production using heterologous or endogenous genes are introduced. Molecular genetic approaches can expand the BVC repertoire of beneficial bacteria to target additional beneficial effects, or simply boost the production level of naturally occurring BVCs. The effects of direct BVC application in soil are reviewed and evaluated for potential large-scale field and agricultural applications. Our review of recent BVC data indicates that BVCs have great potential to serve as effective biostimulants and bioprotectants even under open-field conditions.
      PubDate: 2015-07-16
  • Analysis of cuticular wax constituents and genes that contribute to the
           formation of ‘glossy Newhall’, a spontaneous bud mutant from
           the wild-type ‘Newhall’ navel orange
    • Abstract: Navel orange (Citrus sinensis [L.] Osbeck) fruit surfaces contain substantial quantities of cuticular waxes, which have important eco-physiological roles, such as water retention and pathogen defense. The wax constituents of ripe navel orange have been studied in various reports, while the wax changes occurring during fruit development and the molecular mechanism underlying their biosynthesis/export have not been investigated. Recently, we reported a spontaneous bud mutant from the wild-type (WT) ‘Newhall’ Navel orange. This mutant displayed unusual glossy fruit peels and was named ‘glossy Newhall’ (MT). In this study, we compared the developmental profiles of the epicuticular and intracuticular waxes on the WT and MT fruit surfaces. The formation of epicuticular wax crystals on the navel orange surface was shown to be dependent on the accumulation of high amounts of aliphatic wax components with trace amounts of terpenoids. In sharp contrast, the underlying intracuticular wax layers have relatively low concentrations of aliphatic wax components but high concentrations of cyclic wax compounds, especially terpenoids at the late fruit developmental stages. Our work also showed that many genes that are involved in wax biosynthesis and export pathways were down-regulated in MT fruit peels, leading to a decrease in aliphatic wax component amounts and the loss of epicuticular wax crystals, ultimately causing the glossy phenotype of MT fruits.
      PubDate: 2015-07-16
  • Functional architecture of two exclusively late stage pollen-specific
           promoters in rice ( Oryza sativa L.)
    • Abstract: Late stage pollen-specific promoters are important tools in crop molecular breeding. Several such promoters, and their functional motifs, have been well characterized in dicotyledonous plants such as tomato and tobacco. However, knowledge about the functional architecture of such promoters is limited in the monocotyledonous plant rice. Here, pollen-late-stage-promoter 1 (PLP1) and pollen-late-stage-promoter 2 (PLP2) were characterized using a stable transformation system in rice. Histochemical staining showed that the two promoters exclusively drive GUS expression in late-stage pollen grains in rice. 5′ deletion analysis revealed that four regions, including the −1159 to −720 and the −352 to −156 regions of PLP1 and the −740 to −557 and the −557 to −339 regions of PLP2, are important in maintaining the activity and specificity of these promoters. Motif mutation analysis indicated that ‘AGAAA’ and ‘CAAT’ motifs in the −740 to −557 region of PLP2 act as enhancers in the promoter. Gain of function experiments indicated that the novel TA-rich motif ‘TACATAA’ and ‘TATTCAT’ in the core region of the PLP1 and PLP2 promoters is necessary, but not sufficient, for pollen-specific expression in rice. Our results provide evidence that the enhancer motif ‘AGAAA’ is conserved in the pollen-specific promoters of both monocots and eudicots, but that some functional architecture characteristics are different.
      PubDate: 2015-07-01
  • DNA METHYLTRANSFERASE 1 is involved in m CG and m CCG DNA methylation and
           is essential for sporophyte development in Physcomitrella patens
    • Abstract: DNA methylation has a crucial role in plant development regulating gene expression and silencing of transposable elements. Maintenance DNA methylation in plants occurs at symmetrical mCG and mCHG contexts (m = methylated) and is maintained by DNA METHYLTRANSFERASE 1 (MET1) and CHROMOMETHYLASE (CMT) DNA methyltransferase protein families, respectively. While angiosperm genomes encode for several members of MET1 and CMT families, the moss Physcomitrella patens, serving as a model for early divergent land plants, carries a single member of each family. To determine the function of P. patens PpMET we generated ΔPpmet deletion mutant which lost mCG and unexpectedly mCCG methylation at loci tested. In order to evaluate the extent of mCCG methylation by MET1, we reexamined the Arabidopsis thaliana Atmet1 mutant methylome and found a similar pattern of methylation loss, suggesting that maintenance of DNA methylation by MET1 is conserved through land plant evolution. While ΔPpmet displayed no phenotypic alterations during its gametophytic phase, it failed to develop sporophytes, indicating that PpMET plays a role in gametogenesis or early sporophyte development. Expression array analysis revealed that the deletion of PpMET resulted in upregulation of two genes and multiple repetitive sequences. In parallel, expression analysis of the previously reported ΔPpcmt mutant showed that lack of PpCMT triggers overexpression of genes. This overexpression combined with loss of mCHG and its pleiotropic phenotype, implies that PpCMT has an essential evolutionary conserved role in the epigenetic control of gene expression. Collectively, our results suggest functional conservation of MET1 and CMT families during land plant evolution. A model describing the relationship between MET1 and CMT in CCG methylation is presented.
      PubDate: 2015-07-01
  • The activity of the artemisinic aldehyde Δ11(13) reductase promoter
           is important for artemisinin yield in different chemotypes of Artemisia
           annua L.
    • Abstract: The artemisinic aldehyde double bond reductase (DBR2) plays an important role in the biosynthesis of the antimalarial artemisinin in Artemisia annua. Artemisinic aldehyde is reduced into dihydroartemisinic aldehyde by DBR2. Artemisinic aldehyde can also be oxidized by amorpha-4,11-diene 12-hydroxylase and/or aldehyde dehydrogenase 1 to artemisinic acid, a precursor of arteannuin B. In order to better understand the effects of DBR2 expression on the flow of artemisinic aldehyde into either artemisinin or arteannuin B, we determined the content of dihydroartemisinic aldehyde, artemisinin, artemisinic acid and arteannuin B content of A. annua varieties sorted into two chemotypes. The high artemisinin producers (HAPs), which includes the ‘2/39’, ‘Chongqing’ and ‘Anamed’ varieties, produce more artemisinin than arteannuin B; the low artemisinin producers (LAPs), which include the ‘Meise’, ‘Iran#8’, ‘Iran#14’, ‘Iran#24’ and ‘Iran#47’ varieties, produce more arteannuin B than artemisinin. Quantitative PCR showed that the relative expression of DBR2 was significantly higher in the HAP varieties. We cloned and sequenced the promoter of the DBR2 gene from varieties of both the LAP and the HAP groups. There were deletions/insertions in the region just upstream of the ATG start codon in the LAP varities, which might be the reason for the different promoter activities of the HAP and LAP varieties. The relevance of promoter variation, DBR2 expression levels and artemisinin biosynthesis capabilities are discussed and a selection method for HAP varieties with a DNA marker is suggested. Furthermore, putative cis-acting regulatory elements differ between the HAP and LAP varieties.
      PubDate: 2015-07-01
  • Ascorbate biosynthesis and its involvement in stress tolerance and plant
           development in rice ( Oryza sativa L.)
    • Abstract: Ascorbic acid (AsA) biosynthesis and its implications for stress tolerance and plant development were investigated in a set of rice knock-out (KO) mutants for AsA biosynthetic genes and their wild-types. KO of two isoforms of GDP-d-mannose epimerase (OsGME) reduced the foliar AsA level by 20–30 %, and KO of GDP-l-galactose phosphorylase (OsGGP) by 80 %, while KO of myo-inositol oxygenase (OsMIOX) did not affect foliar AsA levels. AsA concentration was negatively correlated with lipid peroxidation in foliar tissue under ozone stress and zinc deficiency, but did not affect the sensitivity to iron toxicity. Lack of AsA reduced the photosynthetic efficiency as represented by the maximum carboxylation rate of Rubisco (Vmax), the maximum electron transport rate (Jmax) and the chlorophyll fluorescence parameter ΦPSII. Mutants showed lower biomass production than their wild-types, especially when OsGGP was lacking (around 80 % reductions). All plants except for KO mutants of OsGGP showed distinct peaks in foliar AsA concentrations during the growth, which were consistent with up-regulation of OsGGP, suggesting that OsGGP plays a pivotal role in regulating foliar AsA levels during different growth stages. In conclusion, our data demonstrate multiple roles of AsA in stress tolerance and development of rice.
      PubDate: 2015-07-01
  • Dual functions of GmTOE4a in the regulation of photoperiod-mediated
           flowering and plant morphology in soybean
    • Abstract: Flowering time, maturity, and plant morphology have considerable effects on the adaptation and grain yield of soybean (Glycine max). The identification of novel genes and an understanding of their molecular basis are critical to improve soybean productivity. In this study, we cloned a flowering time related APETALA2-like gene GmTOE4a and generated GmTOE4a-overexpressing lines in the cultivar Williams 82. The transgenic lines exhibited late flowering both under long day and short day conditions, and repressed the flowering-related genes, including GmFT2a, GmFT5a, GmAP1, and GmLFY, whereas the flowering repressors GmFT4 and miR156 were upregulated. Interestingly, GmTOE4a was also mediated by photoperiod via maturity genes E3 and E4, which encode photoreceptors in soybean. Further, miR172-mediated GmTOE4a, which regulates flowering in soybean, is different in Arabidopsis in that it is dependent on the CONSTANS-like gene GmCOL1a. In addition to its effect on flowering time, GmTOE4a regulated plant morphology, increased stem thickness, and reduced plant height, internode length and leaf size, which are important agronomic traits that enhance the capacity to resist lodging and increase soybean yield. This is useful information to understand the molecular mechanism of flowering time and plant morphology in soybean and will greatly influence soybean yield improvement.
      PubDate: 2015-07-01
  • The rice transcription factor OsWRKY47 is a positive regulator of the
           response to water deficit stress
    • Abstract: OsWRKY47 is a divergent rice transcription factor belonging to the group II of the WRKY family. A transcriptomic analysis of the drought response of transgenic rice plants expressing P SARK ::IPT, validated by qPCR, indicated that OsWRKY47 expression was induced under drought stress in P SARK ::IPT plants. A PCR-assisted site selection assay (SELEX) of recombinant OsWRKY47 protein showed that the preferred sequence bound in vitro is (G/T)TTGACT. Bioinformatics analyses identified a number of gene targets of OsWRKY47; among these two genes encode a Calmodulin binding protein and a Cys-rich secretory protein. Using Oswrk47 knockout mutants and transgenic rice overexpressing OsWRKY47 we show that the transcription of these putative targets were regulated by OsWRKY47. Phenotypic analysis carried out with transgenic rice plants showed that Oswrky47 mutants displayed higher sensitivity to drought and reduced yield, while plants overexpressing OsWRKY47 were more tolerant.
      PubDate: 2015-07-01
  • Genome-wide analysis reveals phytohormone action during cassava storage
           root initiation
    • Abstract: Development of storage roots is a process associated with a phase change from cell division and elongation to radial growth and accumulation of massive amounts of reserve substances such as starch. Knowledge of the regulation of cassava storage root formation has accumulated over time; however, gene regulation during the initiation and early stage of storage root development is still poorly understood. In this study, transcription profiling of fibrous, intermediate and storage roots at eight weeks old were investigated using a 60-mer-oligo microarray. Transcription and gene expression were found to be the key regulating processes during the transition stage from fibrous to intermediate roots, while homeostasis and signal transduction influenced regulation from intermediate roots to storage roots. Clustering analysis of significant genes and transcription factors (TF) indicated that a number of phytohormone-related TF were differentially expressed; therefore, phytohormone-related genes were assembled into a network of correlative nodes. We propose a model showing the relationship between KNOX1 and phytohormones during storage root initiation. Exogeneous treatment of phytohormones N 6 -benzylaminopurine and 1-Naphthaleneacetic acid were used to induce the storage root initiation stage and to investigate expression patterns of the genes involved in storage root initiation. The results support the hypothesis that phytohormones are acting in concert to regulate the onset of cassava storage root development. Moreover, MeAGL20 is a factor that might play an important role at the onset of storage root initiation when the root tip becomes swollen.
      PubDate: 2015-06-29
  • A purple acid phosphatase plays a role in nodule formation and nitrogen
           fixation in Astragalus sinicus
    • Abstract: The AsPPD1 gene from Astragalus sinicus encodes a purple acid phosphatase. To address the functions of AsPPD1 in legume-rhizobium symbiosis, its expression patterns, enzyme activity, subcellular localization, and phenotypes associated with its over-expression and RNA interference (RNAi) were investigated. The expression of AsPPD1 was up-regulated in roots and nodules after inoculation with rhizobia. Phosphate starvation reduced the levels of AsPPD1 transcripts in roots while increased those levels in nodules. We confirmed the acid phosphatase and phosphodiesterase activities of recombinant AsPPD1 purified from Pichia pastoris, and demonstrated its ability to hydrolyze ADP and ATP in vitro. Subcellular localization showed that AsPPD1 located on the plasma membranes in hairy roots and on the symbiosomes membranes in root nodules. Over-expression of AsPPD1 in hairy roots inhibited nodulation, while its silencing resulted in nodules early senescence and significantly decreased nitrogenase activity. Furthermore, HPLC measurement showed that AsPPD1 overexpression affects the ADP levels in the infected roots and nodules, AsPPD1 silencing affects the ratio of ATP/ADP and the energy charge in nodules, and quantitative observation demonstrated the changes of AsPPD1 transcripts level affected nodule primordia formation. Taken together, it is speculated that AsPPD1 contributes to symbiotic ADP levels and energy charge control, and this is required for effective nodule organogenesis and nitrogen fixation.
      PubDate: 2015-06-24
  • Membrane targeting of MnSOD is essential for oxidative stress tolerance of
           nitrogen-fixing cultures of Anabaena sp. strain PCC7120
    • Abstract: The nitrogen-fixing cyanobacterium, Anabaena PCC7120 encodes for a membrane-targeted 30 kDa Mn-superoxide dismutase (MnSOD) and a cytosolic FeSOD. The MnSOD is post-translationally processed to 27 and 24 kDa forms in the cytosol and periplasm/thylakoid lumen. The extent of cleavage of signal and linker peptides at the N-terminus is dependent on the availability of combined nitrogen during growth. While the 24 and 27 kDa forms are present in near equal proportions under nitrogen-fixing conditions, the 24 kDa form is predominant under nitrogen-supplemented conditions. Individual contribution of these forms of MnSOD to total oxidative stress tolerance was analysed using recombinant Anabaena strains overexpressing either different molecular forms of MnSOD or MnSOD defective in the cleavage of signal/linker peptide. Targeting of MnSOD to the membrane and subsequent cleavage to release both the 24 and 27 kDa forms was essential for oxidative stress tolerance under nitrogen-fixing conditions. On the other hand, the cleavage of linker peptide was absolutely essential and the release of cytosolic 24 kDa form of MnSOD was obligatory for developing oxidative stress tolerance under nitrogen-supplemented conditions. Thus, a single MnSOD caters to the reduction of superoxide radical in both cytosol and thylakoid lumen/periplasm irrespective of the N-status of growth by regulating its cleavage. This is the first report on the physiological advantage of membrane-targeting and processing of MnSOD in either bacteria or plants. The higher oxidative stress tolerance offered by the cytosolic form of MnSOD has possibly resulted in retention of only the cytosolic form in bacterial non-nitrogen-fixers during evolution.
      PubDate: 2015-06-24
  • Crucial roles of the pentatricopeptide repeat protein SOAR1 in Arabidopsis
           response to drought, salt and cold stresses
    • Abstract: Whereas several mitochondrial/chloroplast pentatricopeptide repeat (PPR) proteins have been reported to regulate plant responses to abiotic stresses, no nucleus-localized PPR protein has been found to play role in these processes. In the present experiment, we provide evidence that a cytosol-nucleus dual-localized PPR protein SOAR1, functioning to negatively regulate abscisic acid (ABA) signaling in seed germination and postgermination growth, is a crucial, positive regulator of plant response to abiotic stresses. Downregulation of SOAR1 expression reduces, but upregulation of SOAR1 expression enhances, ABA sensitivity in ABA-induced promotion of stomatal closure and inhibition of stomatal opening, and plant tolerance to multiple, major abiotic stresses including drought, high salinity and low temperature. Interestingly and importantly, the SOAR1-overexpression lines display strong abilities to tolerate drought, salt and cold stresses, with surprisingly high resistance to salt stress in germination and postgermination growth of seeds that are able to potentially germinate in seawater, while no negative effect on plant growth and development was observed. So, the SOAR1 gene is likely useful for improvement of crops by transgenic manipulation to enhance crop productivity in stressful conditions. Further experimental data suggest that SOAR1 likely regulates plant stress responses at least partly by integrating ABA-dependent and independent signaling pathways, which is different from the ABI2/ABI1 type 2C protein phosphatase-mediated ABA signaling. These findings help to understand highly complicated stress and ABA signalling network.
      PubDate: 2015-06-21
  • Comparison of gene expression profiles and responses to zinc chloride
           among inter- and intraspecific hybrids with growth abnormalities in wheat
           and its relatives
    • Abstract: Hybrid necrosis is a well-known reproductive isolation mechanism in plant species, and an autoimmune response is generally considered to trigger hybrid necrosis through epistatic interaction between disease resistance-related genes in hybrids. In common wheat, the complementary Ne1 and Ne2 genes control hybrid necrosis, defined as type I necrosis. Two other types of hybrid necrosis (type II and type III) have been observed in interspecific hybrids between tetraploid wheat and Aegilops tauschii. Another type of hybrid necrosis, defined here as type IV necrosis, has been reported in F1 hybrids between Triticum urartu and some accessions of Triticum monococcum ssp. aegilopoides. In types I, III and IV, cell death occurs gradually starting in older tissues, whereas type II necrosis symptoms occur only under low temperature. To compare comprehensive gene expression patterns of hybrids showing growth abnormalities, transcriptome analysis of type I and type IV necrosis was performed using a wheat 38k oligo-DNA microarray. Defense-related genes including many WRKY transcription factor genes were dramatically up-regulated in plants showing type I and type IV necrosis, similarly to other known hybrid abnormalities, suggesting an association with an autoimmune response. Reactive oxygen species generation and necrotic cell death were effectively inhibited by ZnCl2 treatment in types I, III and IV necrosis, suggesting a significant association of Ca2+ influx in upstream signaling of necrotic cell death in wheat hybrid necrosis.
      PubDate: 2015-06-17
  • Accurate CpG and non-CpG cytosine methylation analysis by high-throughput
           locus-specific pyrosequencing in plants
    • Abstract: Pyrosequencing permits accurate quantification of DNA methylation of specific regions where the proportions of the C/T polymorphism induced by sodium bisulfite treatment of DNA reflects the DNA methylation level. The commercially available high-throughput locus-specific pyrosequencing instruments allow for the simultaneous analysis of 96 samples, but restrict the DNA methylation analysis to CpG dinucleotide sites, which can be limiting in many biological systems. In contrast to mammals where DNA methylation occurs nearly exclusively on CpG dinucleotides, plants genomes harbor DNA methylation also in other sequence contexts including CHG and CHH motives, which cannot be evaluated by these pyrosequencing instruments due to software limitations. Here, we present a complete pipeline for accurate CpG and non-CpG cytosine methylation analysis at single base-resolution using high-throughput locus-specific pyrosequencing. The devised approach includes the design and validation of PCR amplification on bisulfite-treated DNA and pyrosequencing assays as well as the quantification of the methylation level at every cytosine from the raw peak intensities of the Pyrograms by two newly developed Visual Basic Applications. Our method presents accurate and reproducible results as exemplified by the cytosine methylation analysis of the promoter regions of two Tomato genes (NOR and CNR) encoding transcription regulators of fruit ripening during different stages of fruit development. Our results confirmed a significant and temporally coordinated loss of DNA methylation on specific cytosines during the early stages of fruit development in both promoters as previously shown by WGBS. The manuscript describes thus the first high-throughput locus-specific DNA methylation analysis in plants using pyrosequencing.
      PubDate: 2015-06-14
  • Involvement of genes encoding ABI1 protein phosphatases in the response of
           Brassica napus L. to drought stress
    • Abstract: In this report we characterized the Arabidopsis ABI1 gene orthologue and Brassica napus gene paralogues encoding protein phosphatase 2C (PP2C, group A), which is known to be a negative regulator of the ABA signaling pathway. Six homologous B. napus sequences were identified and characterized as putative PP2C group A members. To gain insight into the conservation of ABI1 function in Brassicaceae, and understand better its regulatory effects in the drought stress response, we generated transgenic B. napus plants overexpressing A. thaliana ABI1. Transgenic plants subjected to drought showed a decrease in relative water content, photosynthetic pigments content and expression level of RAB18- and RD19A-drought-responsive marker genes relative to WT plants. We present the characterization of the drought response of B. napus with the participation of ABI1-like paralogues. The expression pattern of two evolutionarily distant paralogues, BnaA01.ABI1.a and BnaC07.ABI1.b in B. napus and their promoter activity in A. thaliana showed differences in the induction of the paralogues under dehydration stress. Comparative sequence analysis of both BnaABI1 promoters showed variation in positions of cis-acting elements that are especially important for ABA- and stress-inducible expression. Together, these data reveal that subfunctionalization following gene duplication may be important in the maintenance and functional divergence of the BnaABI1 paralogues. Our results provide a framework for a better understanding of (1) the role of ABI1 as a hub protein regulator of the drought response, and (2) the differential involvement of the duplicated BnaABI1 genes in the response of B. napus to dehydration-related stresses.
      PubDate: 2015-06-10
  • Identification of ICE1 as a negative regulator of ABA-dependent pathways
           in seeds and seedlings of Arabidopsis
    • Abstract: Inducer of CBF expression 1 (ICE1) mediates the cold stress signal via an abscisic acid (ABA)-independent pathway. A possible role of ICE1 in ABA-dependent pathways was examined in this study. Seedling growth was severely reduced in a T-DNA insertion mutant of ICE1, ice1-2, when grown on 1/2 MS medium lacking sugars, but was restored to wild-type (WT) levels by supplementation with 56 mM glucose. In addition to this sugar-dependent phenotype, germination and establishment of ice1-2 were more sensitive to high glucose concentrations than in the WT. Hypersensitivity to ABA was also observed in ice1-2, suggesting its sensitivity to glucose might be mediated through the ABA signaling pathway. Glucose and ABA induced much higher expression of two genes related to ABA signal transduction, ABA-INSENSITIVE 3 (ABI3) and ABA-INSENSITIVE 4 (ABI4), in ice1-2 than in the WT during establishment. In summary, in addition to its known roles in regulating cold responses, stomatal development, and endosperm breakdown, ICE1 is a negative regulator of ABA-dependent responses.
      PubDate: 2015-06-06
  • Characterization of the psbH precursor RNAs reveals a precise
           endoribonuclease cleavage site in the psbT/psbH intergenic region that is
           dependent on psbN gene expression
    • Abstract: The plastid psbB operon harbours 5 genes, psbB, psbT, psbH, petB and petD. A sixth gene, the psbN gene, is located on the opposite DNA strand in the psbT/psbH intergenic region. Its transcription produces antisense RNA to a large part of the psbB pentacistronic mRNA. We have investigated whether transcription of the psbN gene, i.e. production of antisense RNA, influences psbT/psbH intergenic processing. Results reveal the existence of four different psbH precursor RNAs. Three of them result from processing and one is produced by transcription initiation. One of the processed RNAs is probably created by site-specific RNA cleavage. This RNA is absent in plants where the psbN gene is not transcribed suggesting that cleavage at this site is dependent on the formation of sense/antisense double-stranded RNA. In order to characterize the nuclease that might be responsible for double-stranded RNA cleavage, we analysed csp41a and csp41b knock-out mutants and the corresponding double mutant. Both CSP41 proteins are known to interact physically and CSP41a had been shown to cleave within 3′-untranslated region stem-loop structures, which contain double-stranded RNA, in vitro. We demonstrate that the psbH RNA, that is absent in plants where the psbN gene is not transcribed, is also strongly diminished in all csp41 plants. Altogether, results reveal a site-specific endoribonuclease cleavage event that seems to depend on antisense RNA and might implicate endoribonuclease activity of CSP41a.
      PubDate: 2015-05-27
  • Overexpression of ZmMAPK1 enhances drought and heat stress in transgenic
           Arabidopsis thaliana
    • Abstract: Mitogen-activated protein kinase (MAPK) signal transduction cascades play a crucial role in the response to extracellular stimuli in eukaryotes. A number of MAPK family genes have been isolated in plants, but the maize MAPK genes have been little studied. Here, we studied the role of maize MAP kinase 1 (ZmMAPK1) using gene expression, protein subcellular localization, transformation in Arabidopsis, expression patterns of the stress-responsive genes and physiological parameter analysis. Our physiological parameter analysis suggested that over-expression ZmMAPK1 can increase proline content and decrease malondialdehyde content under drought, and prevent chlorophyll loss and the production of scavenger reactive oxygen species under heat stress. The resistance characteristics of the over-expression of ZmMAPK1 were associated with a significant increase in survival rate. These results suggest that ZmMAPK1 plays a positive role in response to drought and heat stress in Arabidopsis, and provide new insights into the mechanisms of action of MAPK in response to abiotic stress in plants.
      PubDate: 2015-05-26
  • Erratum to: The activity of the artemisinic aldehyde Δ11(13)
           reductase promoter is important for artemisinin yield in different
           chemotypes of Artemisia annua L.
    • PubDate: 2015-05-22
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