Nataraja KarabaSAPNA HARIHAR2020-10-062020-10-062020-03-20Th-12586https://krishikosh.egranth.ac.in/handle/1/5810152492DNA methylation modulates gene expression in plants when exposed to abiotic stresses. This study aimed to examine the pattern and inheritance of DNA methylation in rice genotypes under drought. DNA methylation occurring at CpG islands (CGI) modulates gene expression. The relationship between epigenetic marks (CGI) and gene expression under drought was analysed using in silico analysis. Promoter regions of many down-regulated genes showed more than two CGI, and only one CGI in upregulated genes under stress. To validate this, in vivo expression analysis was performed using rice genotypes, Apo and IR64 grown under puddled, 100 and 60 percent field capacity (FC) using genes with (PP2C, PAL, LEA3) or without CGI (HSP70, RH25). This analysis indicated an association between CGI and gene expression. The importance of DNA methylation at these sites was studied in rice seedling, Apo, AC39020, BPT5204 and IR64, using 5’-azacytidine (methylation inhibitor) under NaCl and PEG induced stresses, which revealed that DNA methylation regulates gene expression. To study the drought effect on DNA methylation, global methylome was performed using MS-RAPD and whole genome bisulfite sequencing (WGBS). The memory effect was also studied using the plants retained in the puddled, 100 and 60 percent FC and subjected to different soil water status in the subsequent generation. MS-RAPD analysis indicated that stress induced hyper methylation in IR64, and hypo methylation in Apo and the stress memory was retained in the subsequent generation. WGBS in IR64 indicated differential DNA methylation in intergenic region followed by promoter region under 100 and 60 per cent FC. Gene expression analysis using semi-quantitative, real time and nanostring-based approaches of select genes indicated varied pattern of methylation-associated gene expression under stress and these patterns were passed to the next generation. The study highlighted importance of DNA methylation in gene expression under drought and its inheritance.EnglishThesis