Graduate Student International Centre for Genetic Engineering and Biotechnology, New Delhi, India New Delhi, Delhi, India
Body of Abstract: Different genotypes within the same species respond differently to various external factors at the transcriptome level. To better understand the salinity stress tolerance mechanism in plants, our group discovered numerous transcripts that are more abundant in salt-tolerant Pokkali rice than salt-sensitive IR64 rice during salinity treatment. Most of these transcripts encoded unidentified or hypothetical proteins, including those encoding members of Cystathionine-Synthase (CBS) domain-containing proteins (CDCPs). CDCPs are found in all living forms and are known to be involved in diverse cellular processes mostly from investigations in the animal kingdom. We discovered 42 genes encoding CDCPs in rice (Oryza sativa subsp. indica), which are also found in the genomes of its wild relatives. Through both in silico- and qRT-PCR-based gene expression profiling, we found OsCBSX2 to be responsive to various abiotic stresses. At the cellular level, OsCBSX2 was observed to localize in the chloroplast, which probably functions through its interaction with Trx y, a redox regulator as well as with Type-A response regulators (RRs), OsRAC3 (GTPase), and COP9 signalosome subunit5a. In accordance with its stress responsiveness, the transgenic lines overexpressing OsCBSX2 exhibited a higher level of tolerance to salinity and drought. These transgenic lines maintained better photosynthetic performance and higher grain yield than the WT in both stresses. Besides, these lines also managed reduced oxidative stress than the WT in both drought and salinity conditions, which may possibly be through its interaction with the putative Trx Y and the downstream processes. Moreover, we found Arabidopsis mutant (atcbsx1) possessing a mutation in ATCBSX1, an OsCBSX2 ortholog, to be stress-sensitive, however, OsCBSX2 complemented and further enhanced the stress tolerance level of atcbsx1. Overall, our study decodes the preliminary functions of OsCBSX2 that acts as a suitable candidate to improve abiotic stress tolerance in rice.