Publications of NIPGR Scientists
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Item Genome-wide identification and co-expression network analysis provide insights into the roles of auxin response factor gene family in chickpea(Nature Publishing Group, 2017) Singh, Vikash K.; Rajkumar, Mohan Singh; Garg, Rohini; Jain, MukeshAuxin response factors (ARFs) are the transcription factors that regulate auxin responses in various aspects of plant growth and development. Although genome-wide analysis of ARF gene family has been done in some species, no information is available regarding ARF genes in chickpea. In this study, we identified 28 ARF genes (CaARF) in the chickpea genome. Phylogenetic analysis revealed that CaARFs can be divided into four different groups. Duplication analysis revealed that 50% of CaARF genes arose from duplication events. We analyzed expression pattern of CaARFs in various developmental stages. CaARF16.3, CaARF17.1 and CaARF17.2 showed highest expression at initial stages of flower bud development, while CaARF6.2 had higher expression at later stages of flower development. Further, CaARF4.2, CaARF9.2, CaARF16.2 and CaARF7.1 exhibited differential expression under different abiotic stress conditions, suggesting their role in abiotic stress responses. Co-expression network analysis among CaARF, CaIAA and CaGH3 genes enabled us to recognize components involved in the regulatory network associated with CaARFs. Further, we identified microRNAs that target CaARFs and TAS3 locus that trigger production of trans-acting siRNAs targeting CaARFs. The analyses presented here provide comprehensive information on ARF family members and will help in elucidating their exact function in chickpea.Item Transcriptome analysis in different rice cultivars provides novel insights into desiccation and salinity stress responses(Nature Publishing Group, 2016) Shankar, Rama; Bhattacharjee, Annapurna; Jain, MukeshDrought and salinity are the major environmental factors that affect rice productivity. Comparative transcriptome analysis between tolerant and sensitive rice cultivars can provide insights into the regulatory mechanisms involved in these stress responses. In this study, the comparison of transcriptomes of a drought-tolerant [Nagina 22 (N22)] and a salinity-tolerant (Pokkali) rice cultivar with IR64 (susceptible cultivar) revealed variable transcriptional responses under control and stress conditions. A total of 801 and 507 transcripts were exclusively differentially expressed in N22 and Pokkali rice cultivars, respectively, under stress conditions. Gene ontology analysis suggested the enrichment of transcripts involved in response to abiotic stress and regulation of gene expression in stress-tolerant rice cultivars. A larger number of transcripts encoding for members of NAC and DBP transcription factor (TF) families in N22 and members of bHLH and C2H2 TF families in Pokkali exhibited differential regulation under desiccation and salinity stresses, respectively. Transcripts encoding for thioredoxin and involved in phenylpropanoid metabolism were up-regulated in N22, whereas transcripts involved in wax and terpenoid metabolism were up-regulated in Pokkali. Overall, common and cultivar-specific stress-responsive transcripts identified in this study can serve as a helpful resource to explore novel candidate genes for abiotic stress tolerance in rice.Item Transcriptome analyses reveal genotype- and developmental stage-specific molecular responses to drought and salinity stresses in chickpea(Nature Publishing Group, 2016) Garg, Rohini; Shankar, Rama; Thakkar, Bijal; Kudapa, Himabindu; Krishnamurthy, Lakshmanan; Mantri, Nitin; Varshney, Rajeev K.; Bhatia, Sabhyata; Jain, MukeshDrought and salinity are the major factors that limit chickpea production worldwide. We performed whole transcriptome analyses of chickpea genotypes to investigate the molecular basis of drought and salinity stress response/adaptation. Phenotypic analyses confirmed the contrasting responses of the chickpea genotypes to drought or salinity stress. RNA-seq of the roots of drought and salinity related genotypes was carried out under control and stress conditions at vegetative and/or reproductive stages. Comparative analysis of the transcriptomes revealed divergent gene expression in the chickpea genotypes at different developmental stages. We identified a total of 4954 and 5545 genes exclusively regulated in drought-tolerant and salinity-tolerant genotypes, respectively. A significant fraction (~47%) of the transcription factor encoding genes showed differential expression under stress. The key enzymes involved in metabolic pathways, such as carbohydrate metabolism, photosynthesis, lipid metabolism, generation of precursor metabolites/energy, protein modification, redox homeostasis and cell wall component biogenesis, were affected by drought and/or salinity stresses. Interestingly, transcript isoforms showed expression specificity across the chickpea genotypes and/or developmental stages as illustrated by the AP2-EREBP family members. Our findings provide insights into the transcriptome dynamics and components of regulatory network associated with drought and salinity stress responses in chickpea.Item Divergent DNA methylation patterns associated with gene expression in rice cultivars with contrasting drought and salinity stress response(Nature Publishing Group, 2015) Garg, Rohini; Chevala, VVS Narayana; Shankar, Rama; Jain, MukeshDNA methylation is an epigenetic mechanism that play an important role in gene regulation in response to environmental conditions. The understanding of DNA methylation at the whole genome level can provide insights into the regulatory mechanisms underlying abiotic stress response/adaptation. We report DNA methylation patterns and their influence on transcription in three rice (Oryza sativa) cultivars (IR64, stress-sensitive; Nagina 22, drought-tolerant; Pokkali, salinity-tolerant) via an integrated analysis of whole genome bisulphite sequencing and RNA sequencing. We discovered extensive DNA methylation at single-base resolution in rice cultivars, identified the sequence context and extent of methylation at each site. Overall, methylation levels were significantly different in the three rice cultivars. Numerous differentially methylated regions (DMRs) among different cultivars were identified and many of which were associated with differential expression of genes important for abiotic stress response. Transposon-associated DMRs were found coupled to the transcript abundance of nearby protein-coding gene(s). Small RNA (smRNA) abundance was found to be positively correlated with hypermethylated regions. These results provide insights into interplay among DNA methylation, gene expression and smRNA abundance, and suggest a role in abiotic stress adaptation in rice.
