Regulation of Abiotic Stress Response Through NtROS2a-mediated Demethylation in Tobacco

DNA methylation is a common and rapid evolving epigenetic mechanism among higher eukaryotic organisms including cytosine residues in CG and CNG sequences. NtROS2a gene isolated from tobacco plants (Nicotiana tabacum cv Xanthi nc) contains DNA glycosylase domain with significant similarities to Arabidopsis ROS1 and DME at the C-terminus. Purified NtROS2a protein gene is 5,879 bp long and is designated as Nicotiana tabacum Repressor Of Silencing (NtROS: accession numbers; AB281588). RT-PCR analysis initially revealed the adaptive response of the lines overexpressing the gene in tobacco to various abiotic stresses. This was validated when phenotypic evaluation to cold, salt, simulated drought and osmotic stress tolerance was performed. Reduction in leaf wilting rate against high salinity treatment is remarkable in transgenic plants which showed at least 50% less wilting than the WT. Moreover, about 70% wilt rate difference was noted between the transgenic and WT in H2O2 treatment. This study showed that NtROS2a gene encoding DNA glycosylase which caused demethylation could regulate adaptive response of tobacco to various abiotic stress conditions.