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Journal Cover Plant Molecular Biology
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1573-5028 - ISSN (Online) 0167-4412
     Published by Springer-Verlag Homepage  [2209 journals]   [SJR: 1.769]   [H-I: 112]
  • Diverse roles of PtrDUF579 proteins in        class="a-plus-plus">Populus and PtrDUF579-1
           function in vascular cambium proliferation during secondary growth
    • Abstract: Abstract DUF579 (domain of unknown function 579) family proteins contain a DUF579 domain structure but vary greatly in their overall sequence similarity. Several DUF579 proteins have been found to play a role in cell wall biosynthesis in Arabidopsis, while DUF579 family genes have not yet been systematically investigated in Populus. In this study, the Populus DUF579 family proteins were found to be localized in different cell types and subcellular locations. The diverse expression patterns of the proteins indicate that they may perform different functions in Populus. Among the DUF579 family members, PtrDUF579-1 is found to be specifically expressed in vascular cambium zone cells where it is localized in the Golgi apparatus. Suppression of PtrDUF579-1 expression reduced plant height and stem diameter size. Cambium cell division and xylem tissue growth was inhibited while secondary cell wall formation was unchanged in PtrDUF579-1 suppressed plants. Cell walls analysis showed that the composition of the pectin fraction of the cambium cell wall was altered while other polysaccharides were not affected in PtrDUF579-1 suppressed plants. This observation suggest cambium expressed PtrDUF579-1 may affect cell wall biosynthesis and be involved in cambium cell proliferation in Populus. Overall, DUF579 family proteins play a diverse set of roles in Populus.
      PubDate: 2014-06-05
  • The transcriptional response of apple alcohol acyltransferase (MdAAT2) to
           salicylic acid and ethylene is mediated through two apple MYB TFs in
           transgenic tobacco
    • Abstract: Abstract Volatile esters are major factors affecting the aroma of apple fruits, and alcohol acyltransferases (AATs) are key enzymes involved in the last steps of ester biosynthesis. The expression of apple AAT (MdAAT2) is known to be induced by salicylic acid (SA) or ethylene in apple fruits, although the mechanism of its transcriptional regulation remains elusive. In this study, we reveal that two apple transcription factors (TFs), MdMYB1 and MdMYB6, are involved in MdAAT2 promoter response to SA and ethylene in transgenic tobacco. According to electrophoretic mobility shift assays, MdMYB1 or MdMYB6 can directly bind in vitro to MYB binding sites in the MdAAT2 promoter. In vivo, overexpression of the two MYB TFs can greatly enhance MdAAT2 promoter activity, as demonstrated by dual luciferase reporter assays in transgenic tobacco. In contrast to the promoter of MdMYB1 or MdMYB6, the MdAAT2 promoter cannot be induced by SA or ethephon (ETH) in transgenic tobacco, even in stigmas in which the MdAAT2 promoter can be highly induced under normal conditions. However, the induced MYB TFs can dramatically enhance MdAAT2 promoter activity under SA or ETH treatment. We conclude that MdMYB1 and MdMYB6 function in MdAAT2 responses to SA and ethylene in transgenic tobacco, suggesting that a similar regulation mechanism may exist in apple.
      PubDate: 2014-06-04
  • Down-regulating annexin gene        class="a-plus-plus">GhAnn2 inhibits cotton fiber
           elongation and decreases Ca       class="a-plus-plus">2+ influx at the cell apex
    • Abstract: Abstract Cotton fiber is a single cell that differentiates from the ovule epidermis and undergoes synchronous elongation with high secretion and growth rate. Apart from economic importance, cotton fiber provides an excellent single-celled model for studying mechanisms of cell-growth. Annexins are Ca2+- and phospholipid-binding proteins that have been reported to be localized in multiple cellular compartments and involved in control of vesicle secretions. Although several annexins have been found to be highly expressed in elongating cotton fibers, their functional roles in fiber development remain unknown. Here, 14 annexin family members were identified from the fully sequenced diploid G. raimondii (D5 genome), half of which were expressed in fibers of the cultivated tetraploid species G. hirsutum (cv. YZ1). Among them, GhAnn2 from the D genome of the tetraploid species displayed high expression level in elongating fiber. The expression of GhAnn2 could be induced by some phytohormones that play important roles in fiber elongation, such as IAA and GA3. RNAi-mediated down-regulation of GhAnn2 inhibited fiber elongation and secondary cell wall synthesis, resulting in shorter and thinner mature fibers in the transgenic plants. Measurement with non-invasive scanning ion-selective electrode revealed that the rate of Ca2+ influx from extracellular to intracellular was decreased at the fiber cell apex of GhAnn2 silencing lines, in comparison to that in the wild type. These results indicate that GhAnn2 may regulate fiber development through modulating Ca2+ fluxes and signaling.
      PubDate: 2014-06-03
  • Overexpression of a tea flavanone 3-hydroxylase gene confers tolerance to
           salt stress and Alternaria
    in transgenic tobacco
    • Abstract: Abstract Flavan-3-ols are the major flavonoids present in tea (Camellia sinensis) leaves. These are known to have antioxidant and free radical scavenging properties in vitro. Flavanone 3-hydroxylase is considered to be an important enzyme of flavonoid pathway leading to accumulation of flavan-3-ols in tea. Expression analysis revealed the upregulation in transcript levels of C. sinensis flavanone 3-hydroxylase (CsF3H) encoding gene under salt stress. In this study, the biotechnological potential of CsF3H was evaluated by gene overexpression in tobacco (Nicotiana tabacum cv. Xanthi). Overexpression of CsF3H cDNA increased the content of flavan-3-ols in tobacco and conferred tolerance to salt stress and fungus Alternaria solani infection. Transgenic tobaccos were observed for increase in primary root length, number of lateral roots, chlorophyll content, antioxidant enzyme expression and their activities. Also, they showed lesser malondialdehyde content and electrolyte leakage compared to control tobacco plants. Further, transgenic plants produced higher degree of pectin methyl esterification via decreasing pectin methyl esterase (PME) activity in roots and leaves under unstressed and salt stressed conditions. The effect of flavan-3-ols on pectin methyl esterification under salt stressed conditions was further validated through in vitro experiments in which non-transgenic (wild) tobacco seedlings were exposed to salt stress in presence of flavan-3-ols, epicatechin and epigallocatechin. The in vitro exposed seedlings showed similar trend of increase in pectin methyl esterification through decreasing PME activity as observed in CsF3H transgenic lines. Taken together, overexpression of CsF3H provided tolerance to salt stress and fungus A. solani infection to transgenic tobacco through improved antioxidant system and enhanced pectin methyl esterification.
      PubDate: 2014-06-01
  • Sequence comparison and phylogenetic analysis by the Maximum Likelihood
           method of ribosome-inactivating proteins from angiosperms
    • Abstract: Abstract Ribosome-inactivating proteins (RIPs) from angiosperms are rRNA N-glycosidases that have been proposed as defence proteins against virus and fungi. They have been classified as type 1 RIPs, consisting of single-chain proteins, and type 2 RIPs, consisting of an A chain with RIP properties covalently linked to a B chain with lectin properties. In this work we have carried out a broad search of RIP sequence data banks from angiosperms in order to study their main structural characteristics and phylogenetic evolution. The comparison of the sequences revealed the presence, outside of the active site, of a novel structure that might be involved in the internal protein dynamics linked to enzyme catalysis. Also the B-chains presented another conserved structure that might function either supporting the beta-trefoil structure or in the communication between both sugar-binding sites. A systematic phylogenetic analysis of RIP sequences revealed that the most primitive type 1 RIPs were similar to that of the actual monocots (Poaceae and Asparagaceae). The primitive RIPs evolved to the dicot type 1 related RIPs (like those from Caryophyllales, Lamiales and Euphorbiales). The gene of a type 1 RIP related with the actual Euphorbiaceae type 1 RIPs fused with a double beta trefoil lectin gene similar to the actual Cucurbitaceae lectins to generate the type 2 RIPs and finally this gene underwent deletions rendering either type 1 RIPs (like those from Cucurbitaceae, Rosaceae and Iridaceae) or lectins without A chain (like those from Adoxaceae).
      PubDate: 2014-06-01
  • Identification of candidate genes for fusarium yellows resistance in
           Chinese cabbage by differential expression analysis
    • Abstract: Abstract Fusarium yellows caused by Fusarium oxysporum f. sp. conglutinans is an important disease of Brassica worldwide. To identify a resistance (R) gene against Fusarium yellows in Chinese cabbage (Brassica rapa var. pekinensis), we analyzed differential expression at the whole genome level between resistant and susceptible inbred lines using RNA sequencing. Four hundred and eighteen genes were significantly differentially expressed, and these were enriched for genes involved in response to stress or stimulus. Seven dominant DNA markers at putative R-genes were identified. Presence and absence of the sequence of the putative R-genes, Bra012688 and Bra012689, correlated with the resistance of six inbred lines and susceptibility of four inbred lines, respectively. In F2 populations derived from crosses between resistant and susceptible inbred lines, presence of Bra012688 and Bra012689 cosegregated with resistance, suggesting that Bra012688 and Bra012689 are good candidates for fusarium yellows resistance in Chinese cabbage.
      PubDate: 2014-06-01
  • Genome-wide transcriptomic analysis of response to low temperature reveals
           candidate genes determining divergent cold-sensitivity of maize inbred
    • Abstract: Abstract Maize, despite being thermophyllic due to its tropical origin, demonstrates high intraspecific diversity in cold-tolerance. To search for molecular mechanisms of this diversity, transcriptomic response to cold was studied in two inbred lines of contrasting cold-tolerance. Microarray analysis was followed by extensive statistical elaboration of data, literature data mining, and gene ontology-based classification. The lines used had been bred earlier specifically for determination of QTLs for cold-performance of photosynthesis. This allowed direct comparison of present transcriptomic data with the earlier QTL mapping results. Cold-treated (14 h at 8/6 °C) maize seedlings of cold-tolerant ETH-DH7 and cold-sensitive ETH-DL3 lines at V3 stage showed strong, consistent response of the third leaf transcriptome: several thousand probes showed similar, statistically significant change in both lines, while only tens responded differently in the two lines. The most striking difference between the responses of the two lines to cold was the induction of expression of ca. twenty genes encoding membrane/cell wall proteins exclusively in the cold-tolerant ETH-DH7 line. The common response comprised mainly repression of numerous genes related to photosynthesis and induction of genes related to basic biological activity: transcription, regulation of gene expression, protein phosphorylation, cell wall organization. Among the genes showing differential response, several were close to the QTL regions identified in earlier studies with the same inbred lines and associated with biometrical, physiological or biochemical parameters. These transcripts, including two apparently non-protein-coding ones, are particularly attractive candidates for future studies on mechanisms determining divergent cold-tolerance of inbred maize lines.
      PubDate: 2014-06-01
  • CbCBF from        class="a-plus-plus">Capsella bursa-       class="a-plus-plus">pastoris enhances cold
           tolerance and restrains growth in        class="a-plus-plus">Nicotiana tabacum by
           antagonizing with gibberellin and affecting cell cycle signaling
    • Abstract: Abstract Plant cells respond to cold stress via a regulatory mechanism leading to enhanced cold acclimation accompanied by growth retardation. The C-repeat binding factor (CBF) signaling pathway is essential for cold response of flowering plants. Our previously study documented a novel CBF-like gene from the cold-tolerant Capsella bursa-pastoris named CbCBF, which was responsive to chilling temperatures. Here, we show that CbCBF expression is obviously responsive to chilling, freezing, abscisic acid, gibberellic acid (GA), indoleacetic acid or methyl jasmonate treatments and that the CbCBF:GFP fusion protein was localized to the nucleus. In addition, CbCBF overexpression conferred to the cold-sensitive tobacco plants enhanced tolerance to chilling and freezing, as well as dwarfism and delayed flowering. The leaf cells of CbCBF overexpression tobacco lines attained smaller sizes and underwent delayed cell division with reduced expression of cyclin D genes. The dwarfism of CbCBF transformants can be partially restored by GA application. Consistently, CbCBF overexpression reduced the bioactive gibberellin contents and disturbed the expression of gibberellin metabolic genes in tobacco. Meanwhile, cold induced CbCBF expression and cold tolerance in C. bursa-pastoris are reduced by GA. We conclude that CbCBF confers cold resistance and growth inhibition to tobacco cells by interacting with gibberellin and cell cycle pathways, likely through activation of downstream target genes.
      PubDate: 2014-06-01
  • Regulation of CCM genes in        class="a-plus-plus">Chlamydomonas reinhardtii
           during conditions of light–dark cycles in synchronous cultures
    • Abstract: Abstract We have investigated transcript level changes of CO2-concentrating mechanism (CCM) genes during light–dark (12 h:12 h) cycles in synchronized Chlamydomonas reinhardtii at air-level CO2. CCM gene transcript levels vary at various times of light–dark cycles, even at same air-level CO2. Transcripts of inorganic carbon transporter genes (HLA3, LCI1, CCP1, CCP2 and LCIA) and mitochondrial carbonic anhydrase genes (CAH4 and CAH5) are up regulated in light, following which their levels decline in dark. Contrastingly, transcripts of chloroplast carbonic anhydrases namely CAH6, CAH3 and LCIB are up regulated in dark. CAH3 and LCIB transcript levels reached maximum by the end of dark, followed by high expression into early light period. In contrast, CAH6 transcript level stayed high in dark, followed by high level even in light. Moreover, the up regulation of transcripts in dark was undone by high CO2, suggesting that the dark induced CCM transcripts were regulated by CO2 even in dark when CCM is absent. Thus while the CAH3 transcript level modulations appear not to positively correlate with that of CCM, the protein regulation matched with CCM status: in spite of high transcript levels in dark, CAH3 protein reached peak level only in light and localized entirely to pyrenoid, a site functionally relevant for CCM. Moreover, in dark, CAH3 protein level not only reduced but also the protein localized as a diffused pattern in chloroplast. We propose that transcription of most CCM genes, followed by protein level changes including their intracellular localization of a subset is subject to light–dark cycles.
      PubDate: 2014-06-01
  • Characterization and expression patterns of small RNAs in synthesized
           Brassica hexaploids
    • Abstract: Abstract Polyploidy has played an important role in promoting plant evolution through genomic merging and doubling. We used high-throughput sequencing to compare miRNA expression profiles between Brassica hexaploid and its parents. A total of 613, 784 and 742 known miRNAs were identified in Brassica rapa, Brassica carinata, and Brassica hexaploid, respectively. We detected 618 miRNAs were differentially expressed (log2Ratio ≥ 1, P ≤ 0.05) between Brassica hexaploid and its parents, and 425 miRNAs were non-additively expressed in Brassica hexaploid, which suggest a trend of non-additive miRNA regulation following hybridization and polyploidization. Remarkably, majority of the non-additively expressed miRNAs in the Brassica hexaploid are repressed, and there was a bias toward repression of B. rapa miRNAs, which is consistent with the progenitor-biased gene repression in the synthetic allopolyploids. In addition, we identified 653 novel mature miRNAs in Brassica hexaploid and its parents. Finally, we found that almost all the non-additive accumulation of siRNA clusters exhibited a low-parent pattern in Brassica hexaploid. Non-additive small RNA regulation is involved in a range of biological pathways, probably providing a driving force for variation and adaptation in allopolyploids.
      PubDate: 2014-06-01
  • Are rice (Oryza sativa
           L.) phosphate transporters regulated similarly by phosphate and
           arsenate' A comprehensive study
    • Abstract: Abstract Rice is one of the most important staple foods worldwide, but it often contains inorganic arsenic, which is toxic and gives rise to severe health problems. Rice plants take up arsenate As(V) via the phosphate transport pathways, though it is not known how As(V), as compared to phosphate, modifies the expression of phosphate transporters (PTs). Therefore, the impact of As(V) or phosphate (Pi) on the gene expression of PTs and several Pi signaling regulators was investigated. Rice plants were grown on medium containing different As(V) or Pi concentrations. Growth was evaluated and the expression of tested genes was quantified at different time points, using quantitative RT-PCR (qPCR). The As and P content in plants was determined using inductively coupled plasma mass spectrometry (ICP-MS). As(V) elicited diverse and opposite responses of different PTs in roots and shoots, while Pi triggered a more shallow and uniform transcriptional response in several tested genes. Only a restricted set of genes, including PT2, PT3, PT5 and PT13 and two SPX-MFS family members, was particularly responsive to As(V). Despite some common reactions, the responses of the analyzed genes were predominantly ion-specific. The possible reasons and consequences are discussed.
      PubDate: 2014-06-01
  • CRISPR–Cas system: a powerful tool for genome engineering
    • Abstract: Abstract Targeted gene regulation on a genome-wide scale is a powerful strategy for interrogating, perturbing, and engineering cellular systems. Recent advances with the RNA-mediated Cas9 endonuclease derived from clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated proteins (Cas) systems have dramatically transformed our ability to specifically modify intact genomes of diverse cells and organisms. The CRISPR–Cas system has been adapted as an efficient, facile, and robust gene-targeting technology with the potential for high-throughput and multiplexed genome engineering. Exciting breakthroughs in understanding the mechanisms of the CRISPR–Cas system and its enormous potential for applications across basic science, agricultural and biotechnology.
      PubDate: 2014-06-01
  • Transcriptional coordination between leaf cell differentiation and
           chloroplast development established by TCP20 and the subgroup Ib bHLH
           transcription factors
    • Abstract: Abstract The establishment of the photosynthetic apparatus during chloroplast development creates a high demand for iron as a redox metal. However, iron in too high quantities becomes toxic to the plant, thus plants have evolved a complex network of iron uptake and regulation mechanisms. Here, we examined whether four of the subgroup Ib basic helix-loop-helix transcription factors (bHLH38, bHLH39, bHLH100, bHLH101), previously implicated in iron homeostasis in roots, also play a role in regulating iron metabolism in developing leaves. These transcription factor genes were strongly up-regulated during the transition from cell proliferation to expansion, and thus sink-source transition, in young developing leaves of Arabidopsis thaliana. The four subgroup Ib bHLH genes also showed reduced expression levels in developing leaves of plants treated with norflurazon, indicating their expression was tightly linked to the onset of photosynthetic activity in young leaves. In addition, we provide evidence for a mechanism whereby the transcriptional regulators SAC51 and TCP20 antagonistically regulate the expression of these four subgroup Ib bHLH genes. A loss-of-function mutant analysis also revealed that single mutants of bHLH38, bHLH39, bHLH100, and bHLH101 developed smaller rosettes than wild-type plants in soil. When grown in agar plates with reduced iron concentration, triple bhlh39 bhlh100 bhlh101 mutant plants were smaller than wild-type plants. However, measurements of the iron content in single and multiple subgroup Ib bHLH genes, as well as transcript profiling of iron response genes during early leaf development, do not support a role for bHLH38, bHLH39, bHLH100, and bHLH101 in iron homeostasis during early leaf development.
      PubDate: 2014-06-01
  • The MET1b gene encoding
           a maintenance DNA methyltransferase is indispensable for normal
           development in rice
    • Abstract: Abstract While Arabidopsis bears only one MET1 gene encoding the DNA methyltransferase that is mainly responsible for maintaining CG methylation after DNA replication, rice carries two MET1 genes, MET1a and MET1b, expressed in actively replicating and dividing cells, and MET1b is more abundantly expressed than is MET1a. A met1a null mutant displayed no overt phenotypes, implying that MET1b must play a major role in the maintenance DNA methylation. Here, we employed two met1b null mutants, generated by homologous recombination-mediated knock-in targeting and insertion of endogenous retrotransposon Tos17. These MET1a/MET1a met1b/met1b homozygotes exhibited abnormal seed phenotypes, which is associated with either viviparous germination or early embryonic lethality. They also displayed decreased levels of DNA methylation at repetitive CentO sequences and at the FIE1 gene locus in the embryos. In addition, independently isolated knock-in-targeted plants, in which the promoterless GUS reporter gene was fused with the endogenous MET1b promoter, showed the reproducible, dosage-dependent, and spatiotemporal expression patterns of GUS. The genotyping analysis of selfed progeny of heterozygous met1a met1b null mutants indicated that weakly active MET1a seems to serve as a genetic backup mechanism in rice met1b gametophytes, although the stochastic and uncoordinated activation of epigenetic backup mechanisms occurred less efficiently in the met1b homozygotes of rice than in the met1 homozygotes of Arabidopsis. Moreover, passive depletion of CG methylation during the postmeiotic DNA replication in the haploid nuclei of the met1a met1b gametophytes in rice results in early embryonic lethality. This situation somewhat resembles that of the met1 gametophytes in Arabidopsis.
      PubDate: 2014-06-01
  • Identification of direct targets of transcription factor MYB46 provides
           insights into the transcriptional regulation of secondary wall
    • Abstract: Abstract Secondary wall formation requires coordinated transcriptional regulation of the genes involved in the biosynthesis of the components of secondary wall. Transcription factor (TF) MYB46 (At5g12870) has been shown to function as a central regulator for secondary wall formation in Arabidopsis thaliana, activating biosynthetic genes as well as the TFs involved in the pathways. Recently, we reported that MYB46 directly regulates secondary wall-associated cellulose synthase (CESA4, CESA7, and CESA8) and a mannan synthase (CSLA9) genes. However, it is not known whether MYB46 directly activates the biosynthetic genes for hemicellulose and lignin, which are the other two major components of secondary wall. Based on the observations that the promoter regions of many of the secondary wall biosynthetic genes contain MYB46-binding cis-regulatory motif(s), we hypothesized that MYB46 directly regulates the genes involved in the biosynthesis of the secondary wall components. In this report, we describe several lines of experimental evidence in support of the hypothesis. Electrophoretic mobility shift assay and chromatin immunoprecipitation analysis showed that MYB46 directly binds to the promoters of 13 genes involved in lignin and xylan biosynthesis. We then used steroid receptor-based inducible activation system to confirm that MYB46 directly activates the transcription of the xylan and lignin biosynthetic genes. Furthermore, ectopic up-regulation of MYB46 resulted in a significant increase in xylose and a small increase in lignin content based on acetyl bromide soluble lignin measurements in Arabidopsis. Taken together, we conclude that MYB46 function as a central and direct regulator of the genes involved in the biosynthesis of all three major secondary wall components.
      PubDate: 2014-05-31
  • Heat shock factor HSFB2a involved in gametophyte development of        class="a-plus-plus">Arabidopsis thaliana and its
           expression is controlled by a heat-inducible long non-coding antisense RNA
    • Abstract: Abstract Heat stress transcription factors (HSFs) are central regulators of the heat stress response. Plant HSFs of subgroup B lack a conserved sequence motif present in the transcriptional activation domain of class A-HSFs. Arabidopsis members were found to be involved in non-heat shock functions. In the present analysis we investigated the expression, regulation and function of HSFB2a. HSFB2a expression was counteracted by a natural long non-coding antisense RNA, asHSFB2a. In leaves, the antisense RNA gene is only expressed after heat stress and dependent on the activity of HSFA1a/HSFA1b. HSFB2a and asHSFB2a RNAs were also present in the absence of heat stress in the female gametophyte. Transgenic overexpression of HSFB2a resulted in a complete knock down of the asHSFB2a expression. Conversely, asHSFB2a overexpression leads to the absence of HSFB2a RNA. The knockdown of HSFB2a by asHSFB2a correlated with an improved, knockdown of asHSFB2a by HSFB2a overexpression with an impaired biomass production early in vegetative development. In both cases the development of female gametophytes was impaired. A T-DNA knock-out line did not segregate homozygous mutant plants, only heterozygots hsfB2a-tt1/+ were viable. Approximately 50 % of the female gametophytes were arrested in early development, before mitosis 3, resulting in 45 % of sterile ovules. Our analysis indicates that the “Yin–Yang” regulation of gene expression at the HSFB2a locus influences vegetative and gametophytic development in Arabidopsis.
      PubDate: 2014-05-30
  • Transcriptome analysis of salinity responsiveness in contrasting genotypes
           of finger millet (Eleusine
    L.) through RNA-sequencing
    • Abstract: Abstract Finger millet (Eleusine coracana L.) is a hardy cereal known for its superior level of tolerance against drought, salinity, diseases and its nutritional properties. In this study, attempts were made to unravel the physiological and molecular basis of salinity tolerance in two contrasting finger millet genotypes viz., CO 12 and Trichy 1. Physiological studies revealed that the tolerant genotype Trichy 1 had lower Na+ to K+ ratio in leaves and shoots, higher growth rate (osmotic tolerance) and ability to accumulate higher amount of total soluble sugar in leaves under salinity stress. We sequenced the salinity responsive leaf transcriptome of contrasting finger millet genotypes using IonProton platform and generated 27.91 million reads. Mapping and annotation of finger millet transcripts against rice gene models led to the identification of salinity responsive genes and genotype specific responses. Several functional groups of genes like transporters, transcription factors, genes involved in cell signaling, osmotic homeostasis and biosynthesis of compatible solutes were found to be highly up-regulated in the tolerant Trichy 1. Salinity stress inhibited photosynthetic capacity and photosynthesis related genes in the susceptible genotype CO 12. Several genes involved in cell growth and differentiation were found to be up-regulated in both the genotypes but more specifically in tolerant genotype. Genes involved in flavonoid biosynthesis were found to be down-regulated specifically in the salinity tolerant Trichy 1. This study provides a genome-wide transcriptional analysis of two finger millet genotypes differing in their level of salinity tolerance during a gradually progressing salinity stress under greenhouse conditions.
      PubDate: 2014-05-18
           PATTERNING FACTOR-LIKE (EPFL) secreted peptide gene, is required for
           filament elongation in Brassica
    • Abstract: Abstract Inflorescence architecture, pedicel length and stomata patterning in Arabidopsis thaliana are specified by inter-tissue communication mediated by ERECTA and its signaling ligands in the EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family of secreted cysteine-rich peptides. Here, we identified and characterized BnEPFL6 from Brassica napus. Heterologous expression of this gene under the double enhanced CaMV promoter (D35S) in Arabidopsis resulted in shortened stamen filaments, filaments degradation, and reduced filament cell size that displayed down-regulated expression of AHK2, in which phenotypic variation of ahk2-1 mutant presented highly consistent with that of BnEPFL6 transgenic lines. Especially, the expression level of BnEPFL6 in the shortened filaments of four B. napus male sterile lines (98A, 86A, SA, and Z11A) was similar to that of BnEPFL6 in the transgenic Arabidopsis lines. The activity of pBnEPFL6.2::GUS was intensive in the filaments of transgenic lines. These observations reveal that BnEPFL6 plays an important role in filament elongation and may also affect organ morphology and floral organ specification via a BnEPFL6-mediated cascade.
      PubDate: 2014-05-18
  • Brassica villosa, a
           system for studying non-glandular trichomes and genes in the Brassicas
    • Abstract: Abstract Brassica villosa is a wild Brassica C genome species with very dense trichome coverage and strong resistance to many insect pests of Brassica oilseeds and vegetables. Transcriptome analysis of hairy B. villosa leaves indicated higher expression of several important trichome initiation genes compared with glabrous B. napus leaves and consistent with the Arabidopsis model of trichome development. However, transcripts of the TRY inhibitory gene in hairy B. villosa were surprisingly high relative to B. napus and relative transcript levels of SAD2, EGL3, and several XIX genes were low, suggesting potential ancillary or less important trichome-related roles for these genes in Brassica species compared with Arabidopsis. Several antioxidant, calcium, non-calcium metal and secondary metabolite genes also showed differential expression between these two species. These coincided with accumulation of two alkaloid-like compounds, high levels of calcium, and other metals in B. villosa trichomes that are correlated with the known tolerance of B. villosa to high salt and the calcium-rich natural habitat of this wild species. This first time report on the isolation of large amounts of pure B. villosa trichomes, on trichome content, and on relative gene expression differences in an exceptionally hairy Brassica species compared with a glabrous species opens doors for the scientific community to understand trichome gene function in the Brassicas and highlights the potential of B. villosa as a trichome research platform.
      PubDate: 2014-05-16
  • Expression of        class="a-plus-plus">Arabidopsis sugar transport
           protein STP13 differentially affects glucose transport activity and basal
           resistance to Botrytis
    • Abstract: Abstract Botrytis cinerea is the causing agent of the grey mold disease in more than 200 crop species. While signaling pathways leading to the basal resistance against this fungus are well described, the role of the import of sugars into host cells remains to be investigated. In Arabidopsis thaliana, apoplastic hexose retrieval is mediated by the activity of sugar transport proteins (STPs). Expression analysis of the 14 STP genes revealed that only STP13 was induced in leaves challenged with B. cinerea. STP13-modified plants were produced and assayed for their resistance to B. cinerea and glucose transport activity. We report that STP13-deficient plants exhibited an enhanced susceptibility and a reduced rate of glucose uptake. Conversely, plants with a high constitutive level of STP13 protein displayed an improved capacity to absorb glucose and an enhanced resistance phenotype. The correlation between STP13 transcripts, protein accumulation, glucose uptake rate and resistance level indicates that STP13 contributes to the basal resistance to B. cinerea by limiting symptom development and points out the importance of the host intracellular sugar uptake in this process. We postulate that STP13 would participate in the active resorption of hexoses to support the increased energy demand to trigger plant defense reactions and to deprive the fungus by changing sugar fluxes toward host cells.
      PubDate: 2014-05-11
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