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Nature Reviews Microbiol: Genome evolution in filamentous plant pathogens: why bigger can be better (2012)

Nature Reviews Microbiol: Genome evolution in filamentous plant pathogens: why bigger can be better (2012) | Plant Genomics | Scoop.it

Many species of fungi and oomycetes are plant pathogens of great economic importance. Over the past 7 years, the genomes of more than 30 of these filamentous plant pathogens have been sequenced, revealing remarkable diversity in genome size and architecture. Whereas the genomes of many parasites and bacterial symbionts have been reduced over time, the genomes of several lineages of filamentous plant pathogens have been shaped by repeat-driven expansions. In these lineages, the genes encoding proteins involved in host interactions are frequently polymorphic and reside within repeat-rich regions of the genome. Here, we review the properties of these adaptable genome regions and the mechanisms underlying their plasticity, and we illustrate cases in which genome plasticity has contributed to the emergence of new virulence traits. We also discuss how genome expansions may have had an impact on the co-evolutionary conflict between these filamentous plant pathogens and their hosts.


Via Kamoun Lab @ TSL
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Transcriptome variation along bud development in grapevine (Vitis vinifera L.)

Transcriptome variation along bud development in grapevine (Vitis vinifera L.) | Plant Genomics | Scoop.it

Abstract (provisional)

Background

Vegetative buds provide plants in temperate environments the possibility for growth and reproduction when environmental conditions are favorable. In grapevine, crucial developmental events take place within buds during two growing seasons in consecutive years. The first season, the shoot apical meristem within the bud differentiates all the basic elements of the shoot including flowering transition in lateral primordia and development of inflorescence primordia. These events practically end with bud dormancy. The second season, buds resume shoot growth associated to flower formation and development. Gene expression has been previously monitored at specific stages of bud development but has never been followed along the two growing seasons.

Results

Gene expression changes were analyzed along the bud annual cycle at eight different time points. Principal Components Analysis (PCA) revealed that the main factors explaining the global gene expression differences were the processes of bud dormancy and active growth as well as stress responses. Accordingly, non dormant buds showed an enrichment in functional categories typical of actively proliferating and growing cells together with the over abundance of transcripts belonging to stress response pathways. Differential expression analyses performed between consecutive time points indicated that major transcriptional changes were associated to para/endodormancy, endo/ecodormancy and ecodormancy/bud break transitions. Transcripts encoding key regulators of reproductive development were grouped in three major expression clusters corresponding to: (i) transcripts associated to flowering induction, (ii) transcripts associated to flower meristem specification and initiation and (iii) transcripts putatively involved in dormancy. Within this cluster, a MADS-box gene (VvFLC2) and other transcripts with similar expression patterns could participate in dormancy regulation.

Conclusions

This work provides a global view of major transcriptional changes taking place along bud development in grapevine, highlighting those molecular and biological functions involved in the main events of bud development. As reported in other woody species, the results suggest that genes regulating flowering could also be involved in dormancy regulatory pathways in grapevine.

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Reactive short-chain leaf volatiles act as powerful inducers of abiotic stress-related gene expression

Reactive short-chain leaf volatiles act as powerful inducers of abiotic stress-related gene expression | Plant Genomics | Scoop.it
Abiotic stresses cause serious damage to plants; therefore, plants undergo a complicated stress response through signal transduction originating from environmental stimuli. Here we show that a subset of short-chain leaf volatiles with an [agr], [bgr]-unsaturated carbonyl bond in their structure (reactive short-chain leaf volatiles, RSLVs) like (E)-2-hexenal and (E)-2-butenal can act as signal chemicals that strongly induce the gene expression of abiotic-related transcription factors, such as heat stress-related transcription factors (HSFA2, MBF1c) and other abiotic stress-related transcription factors (DREB2A, ZATs). RSLV-induced expression of HSFA2 and MBF1c was eliminated in HSFA1s-, known as heat stress response master regulators, knockout mutant, whereas those of DREB2A and ZATs were not, suggesting that the RSLV signaling pathway is composed of HSFA1-dependent and -independent pathways. RSLV treatment induced production of chaperon proteins, and the RSLV-treated Arabidopsis thus demonstrated enhanced abiotic stress tolerance. Because oxidative stress treatment enhanced RSLV production, we concluded that commonly found RSLVs produced by environmental stresses are powerful inducer of abiotic stress-related gene expression as oxidative stress signals.
Biswapriya Biswavas Misra's insight:

Abiotic stresses cause serious damage to plants; therefore, plants undergo a complicated stress response through signal transduction originating from environmental stimuli. Here we show that a subset of short-chain leaf volatiles with an α, β-unsaturated carbonyl bond in their structure (reactive short-chain leaf volatiles, RSLVs) like (E)-2-hexenal and (E)-2-butenal can act as signal chemicals that strongly induce the gene expression of abiotic-related transcription factors, such as heat stress-related transcription factors (HSFA2,MBF1c) and other abiotic stress-related transcription factors (DREB2A, ZATs). RSLV-induced expression of HSFA2 and MBF1c was eliminated in HSFA1s-, known as heat stress response master regulators, knockout mutant, whereas those of DREB2A and ZATs were not, suggesting that the RSLV signaling pathway is composed of HSFA1-dependent and -independent pathways. RSLV treatment induced production of chaperon proteins, and the RSLV-treated Arabidopsis thus demonstrated enhanced abiotic stress tolerance. Because oxidative stress treatment enhanced RSLV production, we concluded that commonly found RSLVs produced by environmental stresses are powerful inducer of abiotic stress-related gene expression as oxidative stress signals.

  
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Transcriptomic analysis reveals the roles of microtubule-related genes and transcription factors in fruit length regulation in cucumber (Cucumis sativus L.)

Transcriptomic analysis reveals the roles of microtubule-related genes and transcription factors in fruit length regulation in cucumber (Cucumis sativus L.) | Plant Genomics | Scoop.it
Cucumber (Cucumis sativus L.) fruit is a type of fleshy fruit that is harvested immaturely. Early fruit development directly determines the final fruit length and diameter, and consequently the fruit yield and quality. Different cucumber varieties display huge variations of fruit length, but how fruit length is determined at the molecular level remains poorly understood. To understand the genes and gene networks that regulate fruit length in cucumber, high throughout RNA-Seq data were used to compare the transcriptomes of early fruit from two near isogenic lines with different fruit lengths. 3955 genes were found to be differentially expressed, among which 2368 genes were significantly up-regulated and 1587 down-regulated in the line with long fruit. Microtubule and cell cycle related genes were dramatically activated in the long fruit, and transcription factors were implicated in the fruit length regulation in cucumber. Thus, our results built a foundation for dissecting the molecular mechanism of fruit length control in cucumber, a key agricultural trait of significant economic importance.
Biswapriya Biswavas Misra's insight:

Cucumber (Cucumis sativus L.) fruit is a type of fleshy fruit that is harvested immaturely. Early fruit development directly determines the final fruit length and diameter, and consequently the fruit yield and quality. Different cucumber varieties display huge variations of fruit length, but how fruit length is determined at the molecular level remains poorly understood. To understand the genes and gene networks that regulate fruit length in cucumber, high throughout RNA-Seq data were used to compare the transcriptomes of early fruit from two near isogenic lines with different fruit lengths. 3955 genes were found to be differentially expressed, among which 2368 genes were significantly up-regulated and 1587 down-regulated in the line with long fruit. Microtubule and cell cycle related genes were dramatically activated in the long fruit, and transcription factors were implicated in the fruit length regulation in cucumber. Thus, our results built a foundation for dissecting the molecular mechanism of fruit length control in cucumber, a key agricultural trait of significant economic importance.

  
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Identification of horizontally transferred genes in the genus Colletotrichum reveals a steady tempo of bacterial to fungal gene transfer

Horizontal gene transfer (HGT) is the stable transmission of genetic material between organisms by means other than vertical inheritance. HGT has an important role in the evolution of prokaryotes but is relatively rare in eukaryotes. HGT has been shown to contribute to virulence in eukaryotic pathogens. We studied the importance of HGT in plant pathogenic fungi by identifying horizontally transferred genes in the genomes of three members of the genus Colletotrichum.
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Abstract (provisional)Background

Horizontal gene transfer (HGT) is the stable transmission of genetic material between organisms by means other than vertical inheritance. HGT has an important role in the evolution of prokaryotes but is relatively rare in eukaryotes. HGT has been shown to contribute to virulence in eukaryotic pathogens. We studied the importance of HGT in plant pathogenic fungi by identifying horizontally transferred genes in the genomes of three members of the genus Colletotrichum.

Results

We identified eleven HGT events from bacteria into members of the genus Colletotrichum or their ancestors. The HGT events include genes involved in amino acid, lipid and sugar metabolism as well as lytic enzymes. Additionally, the putative minimal dates of transference were calculated using a time calibrated phylogenetic tree. This analysis reveals a constant flux of genes from bacteria to fungi throughout the evolution of subphylum Pezizomycotina.

Conclusions

Genes that are typically transferred by HGT are those that are constantly subject to gene duplication and gene loss. The functions of some of these genes suggest roles in niche adaptation and virulence. We found no evidence of a burst of HGT events coinciding with major geological events. In contrast, HGT appears to be a constant, albeit rare phenomenon in the Pezizomycotina, occurring at a steady rate during their evolution.

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Rescooped by Biswapriya Biswavas Misra from Plant evolution
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Comparative transcriptome analyses reveal core parasitism genes and suggest gene duplication and repurposing as sources of structural novelty

The origin of novel traits is recognized as an important process underlying many major evolutionary radiations. We studied the genetic basis for the evolution of haustoria, the novel feeding organs of parasitic flowering plants, using comparative transcriptome sequencing in three species of Orobanchaceae. Around 180 genes are upregulated during haustorial development following host attachment in at least two species, and these are enriched in proteases, cell wall modifying enzymes, and extracellular secretion proteins. Additionally, about 100 shared genes are upregulated in response to haustorium inducing factors (HIFs) prior to host attachment. Collectively, we refer to these newly identified genes as putative “parasitism genes”. Most of these parasitism genes are derived from gene duplications in a common ancestor of Orobanchaceae andMimulus guttatus, a related non-parasitic plant. Additionally, the signature of relaxed purifying selection and/or adaptive evolution at specific sites was detected in many haustorial genes, and may play an important role in parasite evolution. Comparative analysis of gene expression patterns in parasitic and nonparasitic angiosperms suggests that parasitism genes are derived primarily from root and floral tissues, but with some genes co-opted from other tissues. Gene duplication, often taking place in a nonparasitic ancestor of Orobanchaceae, followed by regulatory neofunctionalization, were important processes in the origin of parasitic haustoria.


Via Pierre-Marc Delaux
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Rescooped by Biswapriya Biswavas Misra from Plant roots and rhizosphere
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Transcriptomic Analysis Highlights Reciprocal Interactions of Urea and Nitrate for Nitrogen Acquisition by Maize Roots

Even if urea and nitrate are the two major nitrogen (N) forms applied as fertilizers in agriculture and occur concomitantly in soils, the reciprocal influence of these two N sources on the mechanisms of their acquisition are poorly understood. Therefore, molecular and physiological aspects of urea and nitrate uptake were investigated in maize (Zea mays), a crop plant consuming high amounts of N.

In roots, the urea uptake was stimulated by the presence of urea in the external solution, indicating the presence of an inducible transport system. On the other hand the presence of nitrate depressed the induction of urea uptake and, at the same time, the induction of nitrate uptake was depressed by the presence of urea.

The expression of about 60,000 transcripts of maize in roots was monitored by microarray analyses and the transcriptional patterns of those genes involved in nitrogen acquisition were analysed by real-time RT-PCR.

In comparison to the treatment without added N, the exposure of maize roots to urea modulated the expression of only very few genes, such as asparagine synthase. On the other hand, the concomitant presence of urea and nitrate enhanced the overexpression of genes involved in nitrate transport (NRT2), assimilation (nitrate and nitrite reductase, glutamine synthetase 2) and determined a specific response of 41 transcripts, including glutamine synthetase 1-5, GOGAT, shikimate kinase and arogenate dehydrogenase. Based also on the real-time RT-PCR analysis, the transcriptional modulation induced by both sources might determine an increase in N-metabolism promoting a more efficient assimilation of taken-up nitrogen.

Via Christophe Jacquet
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Diminishing returns in next-generation sequencing (NGS) transcriptome data

Diminishing returns in next-generation sequencing (NGS) transcriptome data | Plant Genomics | Scoop.it
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RNA-seq is increasingly used to study gene expression of various organisms. While it provides a great opportunity to explore genome-scale transcriptional patterns with tremendous depth, it comes with prohibitive costs. Establishing a minimal sequencing depth for required accuracy will guide cost-effective experimental design and promote the routine application of RNA-seq. To address this issue, we selected 36 RNA-seq datasets, each with more than 20 million reads from six widely-used model organisms: Saccharomyces cerevisiae, Homo sapiens, Drosophila melanogaster, Caenorhabditis elegans, Mus musculus, and Arabidopsis thaliana, and investigated statistical correlations between the sequencing depth and the outcome accuracy. To achieve this, we randomly chose reads from each dataset, mapped them to the reference genomes, and analyzed the accuracy achieved with varying coverage. Our results indicated that as low as one million reads can provide the same sequencing accuracy in transcript abundance (r = 0.99) as > 30 million reads for highly-expressed genes in all six species. Because many metabolically and pathologically-relevant genes are highly expressed, our findings might be instructive for cost-effective experimental designs in NGS-based research and also provide useful guidance to similar research for other organisms.

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An RNA sequencing transcriptome analysis of the high-temperature stressed tall fescue reveals novel insights into plant thermotolerance

Tall fescue (Festuca arundinacea Schreb.) is major cool-season forage and turf grass species worldwide, but high-temperature is a major environmental stress that dramatically threaten forage production and turf management of tall fescue. However, very little is known about the whole-genome molecular mechanisms contributing to thermotolerance. The objectives of this study were to analyzed genome-wide gene expression profiles in the leaves of two tall fescue genotypes, heat tolerant 'PI578718' and heat sensitive 'PI234881' using high-throughput RNA sequencing.
Biswapriya Biswavas Misra's insight:
Abstract (provisional)Background

Tall fescue (Festuca arundinacea Schreb.) is major cool-season forage and turf grass species worldwide, but high-temperature is a major environmental stress that dramatically threaten forage production and turf management of tall fescue. However, very little is known about the whole-genome molecular mechanisms contributing to thermotolerance. The objectives of this study were to analyzed genome-wide gene expression profiles in the leaves of two tall fescue genotypes, heat tolerant 'PI578718' and heat sensitive 'PI234881' using high-throughput RNA sequencing.

Results

A total of 262 million high-quality paired-end reads were generated and assembled into 31,803 unigenes with an average length of 1,840 bp. Of these, 12,974 unigenes showed different expression patterns in response to heat stress and were categorized into 49 Gene Ontology functional subcategories. In addition, the variance of enrichment degree in each functional subcategory between PI578718 and PI234881 increased with increasing treatment time. Cell division and cell cycle genes showed a massive increase in transcript abundance in heat-stressed plants and more activated genes were detected in PI 578718 by Kyoto Encyclopedia of Genes and Genomes pathways analysis. Low molecular weight heat shock protein (LMW-HSP, HSP20) showed activated in two stressed genotypes and high molecular weight HSP (HMW-HSP, HSP90) just in PI578718. Assimilation such as photosynthesis, carbon fixation, CH4, N, S metabolism decreased along with increased dissimilation such as oxidative phosphorylation.

Conclusions

The assembled transcriptome of tall fescue could serve as a global description of expressed genes and provide more molecular resources for future functional characterization analysis of genomics in cool-season turfgrass in response to high-temperature. Increased cell division, LMW/HMW-HSP, dissimilation and antioxidant transcript amounts in tall fescue were correlated with successful resistance to high temperature stress.

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Evaluation of de novo transcriptome assemblies from RNA-Seq data

De novo RNA-Seq assembly facilitates the study of transcriptomes for species without sequenced genomes, but it is challenging to select the most accurate assembly in this context. To address this challenge, we developed a model-based score, RSEM-EVAL, for evaluating assemblies when the ground truth is unknown. We show that RSEM-EVAL correctly reflects assembly accuracy, as measured by REF-EVAL, a refined set of ground-truth-based scores that we also developed. Guided by RSEM-EVAL, we assembled the transcriptome of the regenerating axolotl limb; this assembly compares favorably to a previous assembly. A software package implementing our methods, DETONATE, is freely available at http://deweylab.biostat.wisc.edu/detonate.
Biswapriya Biswavas Misra's insight:

De novo RNA-Seq assembly facilitates the study of transcriptomes for species without sequenced genomes, but it is challenging to select the most accurate assembly in this context. To address this challenge, we developed a model-based score, RSEM-EVAL, for evaluating assemblies when the ground truth is unknown. We show that RSEM-EVAL correctly reflects assembly accuracy, as measured by REF-EVAL, a refined set of ground-truth-based scores that we also developed. Guided by RSEM-EVAL, we assembled the transcriptome of the regenerating axolotl limb; this assembly compares favorably to a previous assembly. A software package implementing our methods, DETONATE, is freely available at http://deweylab.biostat.wisc.edu/detonate.

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Rescooped by Biswapriya Biswavas Misra from MycorWeb Plant-Microbe Interactions
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Extensive Error in the Number of Genes Inferred from Draft Genome Assemblies

Extensive Error in the Number of Genes Inferred from Draft Genome Assemblies | Plant Genomics | Scoop.it
Current sequencing methods produce large amounts of data, but genome assemblies based on these data are often woefully incomplete. These incomplete and error-filled assemblies result in many annotation errors, especially in the number of genes present in a genome. In this paper we investigate the magnitude of the problem, both in terms of total gene number and the number of copies of genes in specific families. To do this, we compare multiple draft assemblies against higher-quality versions of the same genomes, using several new assemblies of the chicken genome based on both traditional and next-generation sequencing technologies, as well as published draft assemblies of chimpanzee. We find that upwards of 40% of all gene families are inferred to have the wrong number of genes in draft assemblies, and that these incorrect assemblies both add and subtract genes. Using simulated genome assemblies of Drosophila melanogaster, we find that the major cause of increased gene numbers in draft genomes is the fragmentation of genes onto multiple individual contigs. Finally, we demonstrate the usefulness of RNA-Seq in improving the gene annotation of draft assemblies, largely by connecting genes that have been fragmented in the assembly process.

Via Francis Martin
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Francis Martin's curator insight, December 20, 2014 11:02 AM

Good that JGI is using RNA-Seq to support gene prediction of our fungal genomes.

Rescooped by Biswapriya Biswavas Misra from Science Garden
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Plants with pocket-sized genomes: Record for smallest plant genome found

Plants with pocket-sized genomes: Record for smallest plant genome found | Plant Genomics | Scoop.it
Members of Genlisea, a genus of carnivorous plants, possess the smallest genomes known in plants. To elucidate genomic evolution in the group as a whole, researchers have now surveyed a wider range of species, and found a new record-holder.

 

The genus Genlisea (corkscrew plants) belongs to the bladderwort family (Lentubulariaceae), a family of carnivorous plants. Some of the 29 species of Genlisea that have been described possess tiny genome sizes. Indeed, the smallest genome yet discovered among flowering plants belongs to a member of the group. The term 'genome' here refers to all genetic material arranged in a set of individual chromosomes present in each cell of a given species. An international team of researchers, led by Professor Günther Heubl of LMU's Department of Biology, has now explored, for the first time, the evolution of genome size and chromosome number in the genus. Heubl and his collaborators studied just over half the known species of Genlisea, and their findings are reported in the latest issue of the journal Annals of Botany.

 

"During the evolution of the genus, the genomes of some Genlisea species must have undergone a drastic reduction in size, which was accompanied by miniaturization of chromosomes, but an increase in chromosome number," says Dr. Andreas Fleischmann, a member of Heubl's research group. Indeed, the chromosomes of the corkscrew plants are so minute that they can only just be resolved by conventional light microscopy. With the aid of an ingenious preparation technique, Dr. Aretuza Sousa, a specialist in cytogenetics and cytology at the Institute of Systematic Botany at LMU, was able to visualize the ultrasmall chromosomes of Genlisea species by fluorescence microscopy. Thanks to this methodology, the researchers were able to identify individual chromosomes and determine their number, as well as measuring the total DNA content of the nuclear genomes of selected representatives of the genus.

 

The LMU researchers also discovered a new record-holder. Genlisea tuberosa, a species that was discovered only recently from Brazil, and was first described by Andreas Fleischmann in collaboration with Brazilian botanists, turns out to have a genome that encompasses only 61 million base pairs (= Mbp; the genome size is expressed as the total number of nucleotide bases found on each of the paired strands of the DNA double helix) Thus G. tuberosa possesses now the smallest plant genome known, beating the previous record by 3 Mbp. Moreover, genome sizes vary widely between different Genlisea species, spanning the range from ~60 to 1700 Mbp.


Via Dr. Stefan Gruenwald, Kim Frye Housh
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Rescooped by Biswapriya Biswavas Misra from plant cell genetics
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Organization and evolution of transposable elements along the bread wheat chromosome 3B

BackgroundThe 17 Gb bread wheat genome has massively expanded through the proliferation of transposable elements and two recent rounds of polyploidization. The assembly of a 774?Mb reference sequence of wheat chromosome 3B provided us with the opportunity to explore the impact of transposable elements (TEs) on the complex wheat genome structure and evolution at a resolution and scale never reached so far.ResultsWe develop an automated workflow, CLARI-TE, for TE modeling in complex genomes. We delineate precisely 56,488 intact and 196,391 fragmented TEs along the 3B pseudomolecule, accounting for 85% of the sequence, and reconstruct 30,199 nested insertions. TEs have been mostly silent for the last one million years, and the 3B chromosome has been shaped by a succession of bursts that occurred between 1 to 3 million years ago. Accelerated TE elimination in the high-recombination distal regions is a driving force towards chromosome partitioning. CACTAs overrepresented in the high-recombination distal regions are significantly associated with recently duplicated genes. In addition, we identify 140 CACTA-mediated gene capture events with 17 genes potentially created by exon shuffling and show that 19 captured genes are transcribed and under selection pressure, suggesting the important role of CACTAs in the recent wheat adaptation.ConclusionAccurate TE modeling uncovers the dynamics of TEs in a highly complex and polyploid genome. It provides novel insights into chromosome partitioning and highlights the role of CACTA transposons in the high level of gene duplication in wheat.

Via Jean-Pierre Zryd
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An evolutionary genomic tale of two rice species

An evolutionary genomic tale of two rice species | Plant Genomics | Scoop.it
The domestication of African rice, Oryza glaberrima, occurred separately from that of the much more widespread Asian rice species Oryza sativa. Analysis of the whole-genome sequence for O. glaberrima shows the extent to which the same genes were involved in these distinct but parallel evolutionary events.
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The domestication of African rice, Oryza glaberrima, occurred separately from that of the much more widespread Asian rice species Oryza sativa. Analysis of the whole-genome sequence for O. glaberrima shows the extent to which the same genes were involved in these distinct but parallel evolutionary events.

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Transcriptomic and Proteomic Analyses of Resistant Host Responses in Arachis diogoi Challenged with Late Leaf Spot Pathogen, Phaeoisariopsis personata

Transcriptomic and Proteomic Analyses of Resistant Host Responses in  Arachis diogoi  Challenged with Late Leaf Spot Pathogen,  Phaeoisariopsis personata | Plant Genomics | Scoop.it
ha
Biswapriya Biswavas Misra's insight:

Late leaf spot is a serious disease of peanut caused by the imperfect fungus, Phaeoisariopsis personata. Wild diploid species, Arachis diogoi. is reported to be highly resistant to this disease and asymptomatic. The objective of this study is to investigate the molecular responses of the wild peanut challenged with the late leaf spot pathogen using cDNA-AFLP and 2D proteomic study. A total of 233 reliable, differentially expressed genes were identified in Arachis diogoi. About one third of the TDFs exhibit no significant similarity with the known sequences in the data bases. Expressed sequence tag data showed that the characterized genes are involved in conferring resistance in the wild peanut to the pathogen challenge. Several genes for proteins involved in cell wall strengthening, hypersensitive cell death and resistance related proteins have been identified. Genes identified for other proteins appear to function in metabolism, signal transduction and defence. Nineteen TDFs based on the homology analysis of genes associated with defence, signal transduction and metabolism were further validated by quantitative real time PCR (qRT-PCR) analyses in resistant wild species in comparison with a susceptible peanut genotype in time course experiments. The proteins corresponding to six TDFs were differentially expressed at protein level also. Differentially expressed TDFs and proteins in wild peanut indicate its defence mechanism upon pathogen challenge and provide initial breakthrough of genes possibly involved in recognition events and early signalling responses to combat the pathogen through subsequent development of resistivity. This is the first attempt to elucidate the molecular basis of the response of the resistant genotype to the late leaf spot pathogen, and its defence mechanism.

  
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Nonuniform gene expression pattern detected along the longitudinal axis in the matured rice leaf

Nonuniform gene expression pattern detected along the longitudinal axis in the matured rice leaf | Plant Genomics | Scoop.it
Rice (Oryza sativa) is a staple crop that supports half the world's population and an important monocot model system. Monocot leaf matures in a basipetal manner, and has a well-defined developmental gradient along the longitudinal axis. However, little is known about its transcriptional dynamics after leaf maturation. In this study, we have reconstructed a high spatial resolution transcriptome for the matured rice leaf by sectioning the leaf into seven 3-cm fragments. We have performed strand-specific Illumina sequencing to generate gene expression profiles for each fragment. We found that the matured leaf contains a longitudinal gene expression gradient, with 6.97% (2,603) of the expressed genes showing differentially expression along the seven sections. The leaf transcriptome showed a gradual transition from accumulating transcripts related to primary cell wall and basic cellular metabolism at the base to those involved in photosynthesis and energy production in the middle, and catabolic metabolism process toward the tip.
Biswapriya Biswavas Misra's insight:

Rice (Oryza sativa) is a staple crop that supports half the world's population and an important monocot model system. Monocot leaf matures in a basipetal manner, and has a well-defined developmental gradient along the longitudinal axis. However, little is known about its transcriptional dynamics after leaf maturation. In this study, we have reconstructed a high spatial resolution transcriptome for the matured rice leaf by sectioning the leaf into seven 3-cm fragments. We have performed strand-specific Illumina sequencing to generate gene expression profiles for each fragment. We found that the matured leaf contains a longitudinal gene expression gradient, with 6.97% (2,603) of the expressed genes showing differentially expression along the seven sections. The leaf transcriptome showed a gradual transition from accumulating transcripts related to primary cell wall and basic cellular metabolism at the base to those involved in photosynthesis and energy production in the middle, and catabolic metabolism process toward the tip.

  
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Developing genome-wide microsatellite markers of bamboo and their applications on molecular marker assisted taxonomy for accessions in the genus Phyllostachys

Developing genome-wide microsatellite markers of bamboo and their applications on molecular marker assisted taxonomy for accessions in the genus Phyllostachys | Plant Genomics | Scoop.it
ted microsatellite markers, 23 markers were selected for polymorphic analysis among 78 accessions an
Biswapriya Biswavas Misra's insight:

Morphology-based taxonomy via exiguously reproductive organ has severely limitation on bamboo taxonomy, mainly owing to infrequent and unpredictable flowering events of bamboo. Here, we present the first genome-wide analysis and application of microsatellites based on the genome of moso bamboo (Phyllostachys edulis) to assist bamboo taxonomy. Of identified 127,593 microsatellite repeat-motifs, the primers of 1,451 microsatellites were designed and 1,098 markers were physically mapped on the genome of moso bamboo. A total of 917 markers were successfully validated in 9 accessions with ~39.8% polymorphic potential. Retrieved from validated microsatellite markers, 23 markers were selected for polymorphic analysis among 78 accessions and 64 alleles were detected with an average of 2.78 alleles per primers. The cluster result indicated the majority of the accessions were consistent with their current taxonomic classification, confirming the suitability and effectiveness of the developed microsatellite markers. The variations of microsatellite marker in different species were confirmed by sequencing and in silicocomparative genome mapping were investigated. Lastly, a bamboo microsatellites database (http://www.bamboogdb.org/ssr) was implemented to browse and search large information of bamboo microsatellites. Consequently, our results of microsatellite marker development are valuable for assisting bamboo taxonomy and investigating genomic studies in bamboo and related grass species.

  
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Deeply diverged alleles in the Arabidopsis AREB1 transcription factor drive genome-wide differences in transcriptional response to the environment

Gene regulatory variation is an important driver of the evolution of physiological and developmental responses to the environment. The abscisic acid (ABA) signaling pathway has long been studied as a key component of the cellular response to abiotic stresses in plants. We identify two haplotypes in an Arabidopsis thaliana transcription factor, AREB1, which plays a central role in ABA-mediated response to osmotic stress. These two haplotypes show the sequence signature of long-term maintenance of genetic diversity, suggesting a role for a diversifying selection process such as balancing selection. We find that the two haplotypes, distinguished by a large number of SNPs and the presence or absence of four small insertion/deletions in AREB1 intron 1 and exon 2, are at roughly equal frequencies in Arabidopsis, and show high linkage disequilibrium and deep sequence divergence. We use a transgenic approach, along with mRNA Sequencing-based assay of genomewide expression levels, and find considerable functional divergence between alleles representing the two haplotype groups. Specifically, we find that, under benign soil-water conditions, transgenic lines containing different AREB1 alleles differ in the expression of a large number of genes associated with pathogen response. There are relatively modest gene expression differences between the two transgenic lines under restricted soil water content. Our finding of pathogen-related activity expands the known roles of AREB1 in A. thaliana and reveals the molecular basis of gene-by-environment interaction in a putatively adaptive plant regulatory protein.


Via Pierre-Marc Delaux
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Genome-wide identification, expression analysis of GH3 family genes in Medicago truncatula under stress-related hormones and Sinorhizobium meliloti infection

Auxin plays a pivotal role in the regulation of plant growth and development by controlling the expression of auxin response genes rapidly. As one of the major auxin early response gene families, Gretchen Hagen 3 (GH3) genes are involved in auxin homeostasis by conjugating excess auxins to amino acids. However, how GH3 genes function in environmental stresses and rhizobial infection responses in Medicago truncatula are largely unknown. Here, based on the latest updated M. truncatula genome, a comprehensive identification and expression profiling analysis of MtGH3 genes were performed. Our data showed that most of MtGH3 genes were expressed in tissue-specific manner and were responsive to environmental stress-related hormones. To understand the possible roles of MtGH3 genes involved in symbiosis establishment between M. truncatula and symbiotic bacteria, quantitative real-time polymerase chain reaction (qRT-PCR) was used to test the expressions of MtGH3 genes during the early phase of Sinorhizobium meliloti infection. The expression levels of most MtGH3 genes were upregulated in shoots and downregulated in roots by S. meliloti infection. The differences in expression responses to S. meliloti infection between roots and shoots were in agreement with the results of free indoleacetic acid (IAA) content measurements. The identification and expression analysis of MtGH3 genes at the early phase of S. meliloti infection may help us to understand the role of GH3-mediated IAA homeostasis in the regulation of nodule formation in model legumes M. truncatula.

Via Christophe Jacquet
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Global transcriptome analysis of developing chickpea (Cicer arietinum L.) seeds

Understanding developmental processes, especially in non-model crop plants, is extremely important in order to unravel unique mechanisms regulating development. Chickpea (C. arietinum L.) seeds are especially valued for their high carbohydrate and protein content. Therefore, in order to elucidate the mechanisms underlying seed development in chickpea, deep sequencing of transcriptomes from four developmental stages was undertaken. In this study, next generation sequencing platform was utilized to sequence the transcriptome of four distinct stages of seed development in chickpea. About 1.3 million reads were generated which were assembled into 51,099 unigenes by merging the de novo and reference assemblies. Functional annotation of the unigenes was carried out using the Uniprot, COG and KEGG databases. RPKM based digital expression analysis revealed specific gene activities at different stages of development which was validated using Real time PCR analysis. More than 90% of the unigenes were found to be expressed in at least one of the four seed tissues. DEGseq was used to determine differentially expressing genes which revealed that only 6.75% of the unigenes were differentially expressed at various stages. Homology based comparison revealed 17.5% of the unigenes to be putatively seed specific. Transcription factors were predicted based on HMM profiles built using TF sequences from five legume plants and analyzed for their differential expression during progression of seed development. Expression analysis of genes involved in biosynthesis of important secondary metabolites suggested that chickpea seeds can serve as a good source of antioxidants. Since transcriptomes are a valuable source of molecular markers like simple sequence repeats (SSRs), about 12,000 SSRs were mined in chickpea seed transcriptome and few of them were validated. In conclusion, this study will serve as a valuable resource for improved chickpea breeding.
Biswapriya Biswavas Misra's insight:

Understanding developmental processes, especially in non-model crop plants, is extremely important in order to unravel unique mechanisms regulating development. Chickpea (C. arietinum L.) seeds are especially valued for their high carbohydrate and protein content. Therefore, in order to elucidate the mechanisms underlying seed development in chickpea, deep sequencing of transcriptomes from four developmental stages was undertaken. In this study, next generation sequencing platform was utilized to sequence the transcriptome of four distinct stages of seed development in chickpea. About 1.3 million reads were generated which were assembled into 51,099 unigenes by merging the de novo and reference assemblies. Functional annotation of the unigenes was carried out using the Uniprot, COG and KEGG databases. RPKM based digital expression analysis revealed specific gene activities at different stages of development which was validated using Real time PCR analysis. More than 90% of the unigenes were found to be expressed in at least one of the four seed tissues. DEGseq was used to determine differentially expressing genes which revealed that only 6.75% of the unigenes were differentially expressed at various stages. Homology based comparison revealed 17.5% of the unigenes to be putatively seed specific. Transcription factors were predicted based on HMM profiles built using TF sequences from five legume plants and analyzed for their differential expression during progression of seed development. Expression analysis of genes involved in biosynthesis of important secondary metabolites suggested that chickpea seeds can serve as a good source of antioxidants. Since transcriptomes are a valuable source of molecular markers like simple sequence repeats (SSRs), about 12,000 SSRs were mined in chickpea seed transcriptome and few of them were validated. In conclusion, this study will serve as a valuable resource for improved chickpea breeding.

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Transcriptomic analysis of the late stages of grapevine ( Vitis vinifera cv. Cabernet Sauvignon) berry ripening reveals significant induction of ethylene signaling and flavor pathways in the skin.

BMC Plant Biol. 2014 Dec 19;14(1):370. [Epub ahead of print]
Biswapriya Biswavas Misra's insight:

BackgroundGrapevine berry, a nonclimacteric fruit, goes through three developmental stages, the last one is the ripening stage, when the berry changes color and dramatically increases in sugar. Flavors derived from terpenoid and fatty acid metabolism develop at the very end of this ripening stage. Whole-genome microarray analysis was used to assess the transcriptomic response of pulp and skin of Cabernet Sauvignon berries in the late stages of ripening between 22 and 37 °Brix.ResultsThere were approximately 18,000 transcripts whose abundance changed with °Brix level and tissue type. There were a large number of changes in many gene ontology (GO) categories involving metabolism, signaling and abiotic stress. GO categories reflecting tissue differences were overrepresented in photosynthesis, isoprenoid metabolism and pigment biosynthesis. Detailed analysis of the interaction of the skin and pulp with °Brix levels revealed that there were statistically significantly higher abundances of transcripts changing with °Brix level in the skin that were involved in ethylene signaling, isoprenoid and fatty acid metabolism. Many transcripts were peaking around known optimal fruit stages for flavor production. The transcript abundance of approximately two-thirds of the AP2/ERF superfamily of transcription factors changed during these developmental stages. The transcript abundance of a unique clade of ERF6-type transcription factors had the largest changes in the skin and clustered with other genes involved in ethylene, senescence, and fruit flavor production including ACC oxidase, terpene synthases, and lipoxygenases. The transcript abundance of other important transcription factors (i.e. SPL, RIN, etc.) involved in the regulation of fruit ripening was also higher in the skin.ConclusionsA detailed analysis of the transcriptome dynamics during late stages of ripening of grapevine berries revealed that these berries went through massive transcriptional changes in gene ontology categories involving chemical signaling and metabolism in both the pulp and skin, particularly in the skin. Changes in the transcript abundance of genes involved in the ethylene signaling pathway of this nonclimacteric fruit were statistically significant in the late stages of ripening when the production of transcripts for important flavor and aroma compounds were at their highest. Ethylene transcription factors known to play a role in leaf senescence also appear to play a role in fruit senescence. Ethylene may play a bigger role than previously thought in this non-climacteric fruit.

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Transcriptome Profiling of Wheat Seedlings following Treatment with Ultrahigh Diluted Arsenic Trioxide.

Evid Based Complement Alternat Med. 2014;2014:851263. doi: 10.1155/2014/851263. Epub 2014 Nov 27.
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Plant systems are useful research tools to address basic questions in homeopathy as they make it possible to overcome some of the drawbacks encountered in clinical trials (placebo effect, ethical issues, duration of the experiment, and high costs). The objective of the present study was to test the hypothesis whether 7-day-old wheat seedlings, grown from seeds either poisoned with a sublethal dose of As2O3 or unpoisoned, showed different significant gene expression profiles after the application of ultrahigh diluted As2O3 (beyond Avogadro's limit) compared to water (control). The results provided evidence for a strong gene modulating effect of ultrahigh diluted As2O3 in seedlings grown from poisoned seeds: a massive reduction of gene expression levels to values comparable to those of the control group was observed for several functional classes of genes. A plausible hypothesis is that ultrahigh diluted As2O3 treatment induced a reequilibration of those genes that were upregulated during the oxidative stress by bringing the expression levels closer to the basal levels normally occurring in the control plants.

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Whole Genome Association Mapping of Plant Height in Winter Wheat (Triticum aestivum L.)

Whole Genome Association Mapping of Plant Height in Winter Wheat (Triticum aestivum L.) | Plant Genomics | Scoop.it
PLOS ONE: an inclusive, peer-reviewed, open-access resource from the PUBLIC LIBRARY OF SCIENCE. Reports of well-performed scientific studies from all disciplines freely available to the whole world.
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The genetic architecture of plant height was investigated in a set of 358 recent European winter wheat varieties plus 14 spring wheat varieties based on field data in eight environments. Genotyping of diagnostic markers revealed the Rht-D1b mutant allele in 58% of the investigated varieties, while the Rht-B1b mutant was only present in 7% of the varieties. Rht-D1 was significantly associated with plant height by using a mixed linear model and employing a kinship matrix to correct for population stratification. Further genotyping data included 732 microsatellite markers, resulting in 770 loci, of which 635 markers were placed on the ITMI map plus a set of 7769 mapped SNP markers genotyped with the 90 k iSELECT chip. When Bonferroni correction was applied, a total of 153 significant marker-trait associations (MTAs) were observed for plant height and the SSR markers (−log10 (P-value) ≥4.82) and 280 (−log10 (P-value) ≥5.89) for the SNPs. Linear regression between the most effective markers and the BLUEs for plant height indicated additive effects for the MTAs of different chromosomal regions. Analysis of syntenic regions in the rice genome revealed closely linked rice genes related to gibberellin acid (GA) metabolism and perception, i.e. GA20 and GA2 oxidases orthologous to wheat chromosomes 1A, 2A, 3A, 3B, 5B, 5D and 7B, ent-kaurenoic acid oxidase orthologous to wheat chromosome 7A, ent-kaurene synthase on wheat chromosome 2B, as well as GA-receptors like DELLA genes orthologous to wheat chromosomes 4B, 4D and 7A and genes of the GID family orthologous to chromosomes 2B and 5B. The data indicated that besides the widely used GA-insensitive dwarfing genes Rht-B1 and Rht-D1 there is a wide spectrum of loci available that could be used for modulating plant height in variety development.

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Analysis of the Phlebiopsis gigantea Genome, Transcriptome and Secretome Provides Insight into Its Pioneer Colonization Strategies of Wood

Analysis of the Phlebiopsis gigantea Genome, Transcriptome and Secretome Provides Insight into Its Pioneer Colonization Strategies of Wood | Plant Genomics | Scoop.it
Collectively classified as white-rot fungi, certain basidiomycetes efficiently degrade the major structural polymers of wood cell walls. A small subset of these Agaricomycetes, exemplified by Phlebiopsis gigantea, is capable of colonizing freshly exposed conifer sapwood despite its high content of extractives, which retards the establishment of other fungal species. The mechanism(s) by which P. gigantea tolerates and metabolizes resinous compounds have not been explored. Here, we report the annotated P. gigantea genome and compare profiles of its transcriptome and secretome when cultured on fresh-cut versus solvent-extracted loblolly pine wood. The P. gigantea genome contains a conventional repertoire of hydrolase genes involved in cellulose/hemicellulose degradation, whose patterns of expression were relatively unperturbed by the absence of extractives. The expression of genes typically ascribed to lignin degradation was also largely unaffected. In contrast, genes likely involved in the transformation and detoxification of wood extractives were highly induced in its presence. Their products included an ABC transporter, lipases, cytochrome P450s, glutathione S-transferase and aldehyde dehydrogenase. Other regulated genes of unknown function and several constitutively expressed genes are also likely involved in P. gigantea's extractives metabolism. These results contribute to our fundamental understanding of pioneer colonization of conifer wood and provide insight into the diverse chemistries employed by fungi in carbon cycling processes.

Via Francis Martin
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Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation

Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation | Plant Genomics | Scoop.it

Leaf development is such a fascinating topic, because it reveals the molecular processes the are involved in pattern formation. Interestingly, several genes and small molecules (e.g., auxin) are used repeatedly during the initiation and elaboration of leaves. A pair of papers out in Plant Cell highlights this thrifty genetic strategy.
In the first, we see how the development of the ligule in a maize leaf involves the redeployment of several genes that are involved in leaf initiation, a process that occurs much earlier in the developmental pathway.


Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation (www.plantcell.org/…/early/2014/12/16/tpc.114.132688.abstract).
In the second, we see the KNOX1 / GA module that is so important in leaf developmental patterning also contributes to the environtmental responsiveness of leaf shape (heterophylly), as found in aquatic plants such as Rorippa aquatica.
Regulation of the KNOX-GA Gene Module Induces Heterophyllic Alteration in North American Lake Cress (http://www.plantcell.org/…/20…/12/16/tpc.114.130229.abstract).
These studies also reinforce our understanding of process of evolution; why start from scratch when you can just tweak something that aleady works in another context?

 


Via Mary Williams, Christophe Jacquet
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An Arabidopsis gene regulatory network for secondary cell wall synthesis

An Arabidopsis gene regulatory network for secondary cell wall synthesis | Plant Genomics | Scoop.it
Biswapriya Biswavas Misra's insight:

The plant cell wall is an important factor for determining cell shape, function and response to the environment. Secondary cell walls, such as those found in xylem, are composed of cellulose, hemicelluloses and lignin and account for the bulk of plant biomass. The coordination between transcriptional regulation of synthesis for each polymer is complex and vital to cell function. A regulatory hierarchy of developmental switches has been proposed, although the full complement of regulators remains unknown. Here we present a protein–DNA network between Arabidopsis thaliana transcription factors and secondary cell wall metabolic genes with gene expression regulated by a series of feed-forward loops. This model allowed us to develop and validate new hypotheses about secondary wall gene regulation under abiotic stress. Distinct stresses are able to perturb targeted genes to potentially promote functional adaptation. These interactions will serve as a foundation for understanding the regulation of a complex, integral plant component.

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Plant genetics: Following the early root of plastome degradation

Plant genetics: Following the early root of plastome degradation | Plant Genomics | Scoop.it
Parasitic organisms are often genomically and morphologically reduced. For example, some parasitic plants contain degraded plastid genomes owing to a reduced need to photosynthesize. A new study now shows that coralroot orchids are in the early stages of the transition to a parasitic lifestyle, and that this condition has arisen independently at least twice in the g…
Biswapriya Biswavas Misra's insight:

Parasitic organisms are often genomically and morphologically reduced. For example, some parasitic plants contain degraded plastid genomes owing to a reduced need to photosynthesize. A new study now shows that coralroot orchids are in the early stages of the transition to a parasitic lifestyle, and that this condition has arisen independently at least twice in the g…

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