No abstract

DNA methylation at cytosine residues governs the regulation of stress responsive genes in plants to generate response against various environmental abiotic stress conditions. Here, we analyzed the epigenetic consequences of drought and salinity on cytosine methylation dynamics of promoter regions of stress responsive Germin-like protein (GLP) genes in rice (Oryza sativa). The bisul te sequencing technique was employed to identify differential methylation status at cytosine residues in selected promoter region of three OsGLP genes (OsGLP4-1, OsGLP8-10 and OsGLP8-12) in leaves and roots of two elite Indica rice cultivars (tolerant KS282 and sensitive Super Basmati) under drought and salt stress. Our results identi ed cultivar, tissue and stress-dependent differentially methylated cytosine residues, however, the extent of methylation was found to be different depending upon CGN, CHG and CHH sequence contexts. Among all three OsGLP genes, promoter region of OsGLP8-12 was observed with most methylated and differentially methylated sites depending upon a particular variety, tissue or stress condition whereas no methylated sites were observed in promoter region of OsGLP4-1 in all samples. Moreover, in promoter regions of OsGLP8-10 and OsGLP8-12, several differentially methylated sites in response to stress treatments were identi ed either near or within cis-regulatory elements (CREs) involved in gene regulation or abiotic stress response indicating the association between promoter methylation and regulation of OsGLP genes under drought and salinity. This study provides insights to argue that altered methylation status of speci c cytosine residues in the promoter regions of OsGLP genes can be a key regulatory mechanism associated with their regulation under abiotic stresses in contrasting rice cultivars.

DNA methylation at cytosine residues governs the regulation of stress responsive genes in plants to generate response against various environmental abiotic stress conditions. Here, we analyzed the epigenetic consequences of drought and salinity on cytosine methylation dynamics of promoter regions of stress responsive Germin-like protein (GLP) genes in rice (Oryza sativa). The bisulfite sequencing technique was employed to identify differential methylation status at cytosine residues in selected promoter region of three OsGLP genes (OsGLP4-1, OsGLP8-10 and OsGLP8-12) in leaves and roots of two elite Indica rice cultivars (tolerant KS282 and sensitive Super Basmati) under drought and salt stress. Our results identified cultivar, tissue and stress-dependent differentially methylated cytosine residues, however, the extent of methylation was found to be different depending upon CGN, CHG and CHH sequence contexts. Among all three OsGLP genes, promoter region of OsGLP8-12 was observed with most methylated and differentially methylated sites depending upon a particular variety, tissue or stress condition whereas no methylated sites were observed in promoter region of OsGLP4-1 in all samples. Moreover, in promoter regions of OsGLP8-10 and OsGLP8-12, several differentially methylated sites in response to stress treatments were identified either near or within cis-regulatory elements (CREs) involved in gene regulation or abiotic stress response indicating the association between promoter methylation and regulation of OsGLP genes under drought and salinity. This study provides insights to argue that altered methylation status of specific cytosine residues in the promoter regions of OsGLP genes can be a key regulatory mechanism associated with their regulation under abiotic stresses in contrasting rice cultivars.

Germin-like proteins (GLPs) are ubiquitous plant proteins, which play significant role in plant responses against various abiotic stresses. However, the potential functions of GLPs in rice (Oryza Sativa) against salt and drought stress are still unclear. In this study, transcriptional variation of 8 OsGLP genes (OsGLP3-6, OsGLP4-1, OsGLP8-4, OsGLP8-7, OsGLP8-10, OsGLP8-11 and OsGLP8-12) was analyzed in leaves and roots of two economically important Indica rice cultivars, KS282 and Super Basmati under salt and drought stress at early seedling stage. The relative expression analysis from qRT-PCR indicated the highest increase in expression of OsGLP3-6 in leaves and roots of both rice varieties with a significantly higher expression in KS282. Moreover, relative change in expression of OsGLP8-7, OsGLP8-10 and OsGLP8-11 under salt stress and OsGLP8-7 under drought stress was also commonly higher in leaves and roots of KS282 as compared to Super Basmati. Whereas, OsGLP3-7 and OsGLP8-12 after salt stress and OsGLP8-4 and OsGLP8-12 after drought stress were observed with higher relative expression in roots of Super Basmati than KS282. Importantly, the OsGLP3-6 and OsGLP4-1 from chromosome 3 and 4 respectively showed higher expression in leaves whereas most of the OsGLP genes from chromosome 8 exhibited higher expression in roots. Overall, as a result of this comparative analysis, OsGLP genes showed both general and specific expression profiles depending upon a specific rice variety, stress condition as well as tissue type. These results will increase our understanding of role of OsGLP genes in rice crop and provide useful information for the further in-depth research on their regulatory mechanisms in response to these stress conditions.