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    CIPK6, a CBL-interacting protein kinase is required for development and salt tolerance in plant
    (Wiley-Blackwell, 2009) Tripathi, Vineeta; Parasuraman, Boominathan; Laxmi, Ashverya; Chattopadhyay, Debasis
    Calcineurin B-like proteins (CBL) and CBL-interacting protein kinases (CIPK) mediate plant responses to a variety of external stresses. Here we report that Arabidopsis CIPK6 is also required for the growth and development of plants. Phenotype of tobacco plants ectopically expressing a homologous gene (CaCIPK6) from the leguminous plant chickpea (Cicer arietinum) indicated its functional conservation. A lesion in AtCIPK6 significantly reduced shoot-to-root and root basipetal auxin transport, and the plants exhibited developmental defects such as fused cotyledons, swollen hypocotyls and compromised lateral root formation, in conjunction with reduced expression of a number of genes involved in auxin transport and abiotic stress response. The Arabidopsis mutant was more sensitive to salt stress compared to wild-type, while overexpression of a constitutively active mutant of CaCIPK6 promoted salt tolerance in transgenic tobacco. Furthermore, tobacco seedlings expressing the constitutively active mutant of CaCIPK6 showed a developed root system, increased basipetal auxin transport and hypersensitivity to auxin. Our results provide evidence for involvement of a CIPK in auxin transport and consequently in root development, as well as in the salt-stress response, by regulating the expression of genes.
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    CAP2 enhances germination of transgenic tobacco seeds at high temperature and promotes heat stress tolerance in yeast
    (Wiley-Blackwell, 2009) Shukla, Rakesh Kumar; Tripathi, Vineeta; Jain, Deepti; Yadav, Rajiv Kumar; Chattopadhyay, Debasis
    We reported earlier that ectopic expression of CAP2, a single AP2 domain containing transcription activator from chickpea (Cicer arietinum) in tobacco improves growth and development, and tolerance to dehydration and salt stress, of the transgenic plants. Here, we report that, in addition, the CAP2-transgenic tobacco seeds also exhibit higher germination efficiency at high temperature and show higher expression levels of genes for tobacco heat shock proteins and a heat shock factor. CAP2 was able to activate the 5¢-upstream activating sequence of tobacco heat shock factor. Surprisingly, expression of CAP2 cDNA in Saccharomyces cerevisiae also enhanced heat tolerance, with increased expression of the gene for yeast heat shock factor 1 (Hsf1) and its target, the gene for yeast heat shock protein 104 (Hsp104). Sequence analysis of the Hsf1 promoter revealed the presence of a dehydration-responsive element ⁄ C-repeat-like element (DRE/ CRE). Recombinant CAP2 protein bound to the DRE/CRE in the Hsf1 promoter in a gel shift assay and transactivated the Hsf1 promoter–His reporter construct. The full-length CAP2 protein was required to provide thermotolerance in yeast. If these findings are taken together, our results suggest that CAP2 is involved in the heat stress response and provides an example of functioning of a plant transcription factor in yeast, highlighting the strong evolutionary conservation of the stress response mechanism.
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    Development of chickpea EST-SSR markers and analysis of allelic variation across related species
    (Springer, 2009) Choudhary, Shalu; Sethy, Niroj Kumar; Shokeen, Bhumika; Bhatia, Sabhyata
    Despite chickpea being the third important grain legume, there is a limited availability of genomic resources, especially of the expressed sequence tag (EST)-based markers. In this study, we generated 822 chickpea ESTs from immature seeds as well as exploited 1,309 ESTs from the chickpea database, thus utilizing a total of 2,131 EST sequences for development of functional EST-SSR markers. Two hundred and forty-six simple sequence repeat (SSR) motifs were identified from which 183 primer pairs were designed and 60 validated as functional markers. Genetic diversity analysis across 30 chickpea accessions revealed ten markers to be polymorphic producing a total of 29 alleles and an observed heterozygosity average of 0.16 thereby exhibiting low levels of intra-specific polymorphism. However, the markers exhibited high cross-species transferability ranging from 68.3 to 96.6% across the six annual Cicer species and from 29.4 to 61.7% across the seven legume genera. Sequence analysis of size variant amplicons from various species revealed that size polymorphism was due to multiple events such as copy number variation, point mutations and insertions/deletions in the microsatellite repeat as well as in the flanking regions. Interestingly, a wide prevalence of crossability-group-specific sequence variations were observed among Cicer species that were phylogenetically informative. The neighbor joining dendrogram clearly separated the chickpea cultivars from the wild Cicer and validated the proximity of C. judaicum with C. pinnatifidum. Hence, this study for the first time provides an insight into the distribution of SSRs in the chickpea transcribed regions and also demonstrates the development and utilization of genic-SSRs. In addition to proving their suitability for genetic diversity analysis, their high rates of transferability also proved their potential for comparative genomic studies and for following gene introgressions and evolution in wild species, which constitute the valuable secondary genepool in chickpea.
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    Comparative analyses of genotype dependent expressed sequence tags and stress-responsive transcriptome of chickpea wilt illustrate predicted and unexpected genes and novel regulators of plant immunity
    (BioMed Central, 2009) Ashraf, Nasheeman; Ghai, Deepali; Barman, Pranjan; Basu, Swaraj; Gangisetty, Nagaraju; Mandal, Mihir K; Chakraborty, Niranjan; Datta, Asis; Chakraborty, Subhra
    Background: The ultimate phenome of any organism is modulated by regulated transcription of many genes. Characterization of genetic makeup is thus crucial for understanding the molecular basis of phenotypic diversity, evolution and response to intra- and extra-cellular stimuli. Chickpea is the world's third most important food legume grown in over 40 countries representing all the continents. Despite its importance in plant evolution, role in human nutrition and stress adaptation, very little ESTs and differential transcriptome data is available, let alone genotype-specific gene signatures. Present study focuses on Fusarium wilt responsive gene expression in chickpea. Results: We report 6272 gene sequences of immune-response pathway that would provide genotype- dependent spatial information on the presence and relative abundance of each gene. The sequence assembly led to the identification of a CaUnigene set of 2013 transcripts comprising of 973 contigs and 1040 singletons, two-third of which represent new chickpea genes hitherto undiscovered. We identified 209 gene families and 262 genotype-specific SNPs. Further, several novel transcription regulators were identified indicating their possible role in immune response. The transcriptomic analysis revealed 649 non- cannonical genes besides many unexpected candidates with known biochemical functions, which have never been associated with pathostress-responsive transcriptome. Conclusion: Our study establishes a comprehensive catalogue of the immune-responsive root transcriptome with insight into their identity and function. The development, detailed analysis of CaEST datasets and global gene expression by microarray provide new insight into the commonality and diversity of organ-specific immune-responsive transcript signatures and their regulated expression shaping the species specificity at genotype level. This is the first report on differential transcriptome of an unsequenced genome during vascular wilt.
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    Proteomics approach to identify dehydration responsive nuclear proteins from chickpea (Cicer arietinum L.)
    (The American Society for Biochemistry and Molecular Biology, Inc., 2008) Pandey, Aarti; Chakraborty, Subhra; Datta, Asis; Chakraborty, Niranjan
    Dehydration or water-deficit is one of the most important environmental stress factors that greatly influences plant growth and development and limits crop productivity. Plants respond and adapt to such stress by altering their cellular metabolism and activating various defense machineries. Mechanisms that operate signal perception, transduction, and downstream regulatory events provide valuable information about the underlying pathways involved in environmental stress responses. The nuclear proteins constitute a highly organized, complex network that plays diverse roles during cellular development and other physiological processes. To gain a better understanding of dehydration response in plants, we have developed a comparative nuclear proteome in a food legume, chickpea (Cicer arietinum L.). Three-week-old chickpea seedlings were subjected to progressive dehydration by withdrawing water and the changes in the nuclear proteome were examined using two-dimensional gel electrophoresis. Approximately 205 protein spots were found to be differentially regulated under dehydration. Mass spectrometry analysis allowed the identification of 147 differentially expressed proteins, presumably involved in a variety of functions including gene transcription and replication, molecular chaperones, cell signaling, and chromatin remodeling. The dehydration responsive nuclear proteome of chickpea revealed a coordinated response, which involves both the regulatory as well as the functional proteins. This study, for the first time, provides an insight into the complex metabolic network operating in the nucleus during dehydration.
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    Expression of CAP2, an AP2-family transcription factor from chickpea enhances growth and tolerance to dehydration and salt tress in transgenic tobacco
    (American Society of Plant Biologists, 2006) Shukla, Rakesh K.; Raha, Sumita; Tripathi, Vineeta; Chattopadhyay, Debasis
    The APETALA2 (AP2) domain defines a large family of DNA-binding proteins that play important roles in plant morphology, development, and stress response. We describe isolation and characterization of a gene (CAP2) from chickpea (Cicer arietinum) encoding a novel AP2-family transcription factor. Recombinant CAP2 protein bound specifically to C-repeat/dehydration- responsive element in gel-shift assay and transactivated reporter genes in yeast (Saccharomyces cerevisiae) one-hybrid assay. CAP2 appeared to be a single/low copy intronless gene, and the protein product localized in the nucleus. Transcript level of CAP2 increased by dehydration and by treatment with sodium chloride, abscisic acid, and auxin, but not by treatment with low temperature, salicylic acid, and jasmonic acid. The 35S promoter-driven expression of CAP2 in tobacco (Nicotiana tabacum) caused drastic increase in the leaf cell size, and, thereby, in leaf surface area and number of lateral roots. Transgenic plants demonstrated more tolerance to dehydration and salt stress than the wild-type plants. Transgenic plants expressed higher steady-state transcript levels of abiotic stress-response genes NtERD10B and NtERD10C and auxin-response genes IAA4.2 and IAA2.5. Taken together, our results indicated a mutual interrelation between plant growth-development and abiotic stress- response pathways and a probable involvement of CAP2 in both the signaling pathways.
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    The nuclear proteome of chickpea (Cicer arietinum L.) reveals predicted and unexpected proteins
    (American Chemical Society, 2006) Pandey, Aarti; Choudhary, Mani Kant; Bhushan, Deepti; Chattopadhyay, Arnab; Chakraborty, Subhra; Datta, Asis; Chakraborty, Niranjan
    Nuclear proteins constitute a highly organized, complex network that plays diverse roles during cellular development and other physiological processes. The yeast nuclear proteome corresponds to about one-fourth of the total cellular proteins, suggesting the involvement of the nucleus in a number of diverse functions. In an attempt to understand the complexity of plant nuclear proteins, we have developed a proteome reference map of a legume, chickpea, using two-dimensional gel electrophoresis (2-DE). Approximately, 600 protein spots were detected, and LC-ESI-MS/MS analyses led to the identification of 150 proteins that have been implicated in a variety of cellular functions. The largest percentage of the identified proteins was involved in signaling and gene regulation (36%), while 17% were involved in DNA replication and transcription. The chickpea nuclear proteome indicates the presence of few new nuclear proteins of unknown functions vis-a-vis many known resident proteins. To the best of our knowledge, this is the first report of a nuclear proteome of an unsequenced genome.
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    Development of sequence-tagged microsatellite site markers for chickpea (Cicer arietinum L.)
    (Wiley-Blackwell, 2006) Choudhary, Shalu; Sethy, Niroj K.; Shokeen, Bhumika; Bhatia, Sabhyata
    Microsatellite loci were identified from chickpea (Cicer arietinum L.), the third most important grain legume crop in the world. A total of 13 sequence-tagged microsatellite markers were developed using two different approaches: (i) amplification using degenerate primers and (ii) cloning of intersimple sequence repeat (ISSR)-amplified fragments. Thirty-five chickpea accessions were analysed, which resulted in a total of 30 alleles at the 13 loci. The observed heterozygosity ranged from 0.1143 to 0.4571 with an average of 0.2284. The cross-species transferability of the sequence-tagged microsatellite site (STMS) markers was checked in Cicer reticulatum, the wild annual progenitor of chickpea. These microsatellite markers will be useful for assessing the genetic diversity patterns within chickpea as well as aid in construction of intra- and interspecific genetic linkage maps.