Background: Though there are at present seventy indigenous aromatic rice cultivars being cultivated in West Bengal, India, the information regarding their genetic regulation of drought tolerance are scanty. Previous work from this laboratory has screened indigenous aromatic rice cultivars Badshabhog and Jamainadu as drought tolerant redox competent and drought susceptible redox incompetent germplasms respectivelybased on redox metabolomic investigation. In this backdrop, the present work comprehended to compare two indigenous aromatic rice cultivars for unfolding genetic regulation of drought stress.
Results: The result of comparative transcriptomic study through RNA-seq analysis in general revealed significant cultivar specific expression of genes under post-imbibitional dehydration stress as well as genes that are expressed in both the experimental cultivars (Oryza sativa L., cultivars Badshabhog and Jamainadu) with differential transcript abundance. 3482 and 3866 genes were found to be significantly down-regulated and up-regulated respectively when we compared between post-imbibitional dehydration stress-raised indigenous aromatic rice cultivars Badshabhog and Jamainadu. Transcripts selected for heatmap generation with proper annotation revealed 50 genes that are significantly expressed genes which are mainly involved in redox functions, signaling, membrane trafficking, replication and protein synthesis etc. On the contrary, genes which got highly expressed in Badshabhog found to be mainly concerned with carbondioxide concentrating mechanism (NADH-dependent malic enzyme), peroxysomal biogenesis, protein modification, protein synthesis, mitochondrial electron transport chain functioning, inercellular protein transport, histone demethylation associated with developmental process, regulation of apoptosis etc. Further Badshabhog exhibited greater GO (gene ontology) distribution so far as signaling, antioxidant functioning, biological and metabolic regulation, transcriptional and translational regulation etc. with significantly higher percentage of antioxidant genes. KEGG (kyoto encyclopedia of genes and genomes) pathway analysis showed several signal transduction pathways (abscisic acid, brassinosteroid, salicylic acid, jasmonic acid and ethylene) being influenced by drought stress.
Conclusion: The overall result of comparative transcriptomic investigation suggests that indigenous aromatic rice cultivars Badshabhog and Jamainadu explored varying strategies to deal with post-imbibitional dehydration stress. The cultivar Badshabhog exhibited a significantly greater molecular reprogramming presumably more through up-regulation of metabolic and energy demanding processes along with implementing better signaling strategies, antioxidative defense mechanism, DNA repair and transcriptional regulation vis-a-vis the cultivar Jamainadu.