R2R3 MYB Transcription Factor, AhMYB94 Plays a Crucial Role in Stress adaptation of a Salt Susceptible Groundnut Cultivar-K6

Abstract

Abstract R2R3 MYB transcription factors are involved in plant growth, plant development and abiotic and biotic stress responses. Several MYB genes are involved in salt tolerance in several plant species. Genotypic variation in the expression of a stress responsive regulatory gene, MYB94 was observed in groundnut under drought and salinity stress conditions. In this study, a stress-responsive transcription factor AhMYB94 was over-expressed in salt-susceptible groundnut cultivar K-6. Relative gene expression analysis revealed that AhMYB94 was significantly higher in groundnut cultivar K9 than in cultivar K6 due to salt treatments. Overexpression of AhMYB94 improved the salt tolerance of groundnut cultivar K6 as evidenced from better growth status, fresh and dry biomass of overexpression lines than wild type (WT) under salt stress conditions. Further, less reactive oxygen species (ROS) accumulated in AhMYB94 overexpressing lines when exposed to salt stress, as estimated by diaminobenzidine (DAB) or nitroblue tetrazolium (NBT) histochemical staining. Furthermore, overexpression of AhMYB94 in groundnut confers significantly increased tolerance ability of plants to oxidative damage under salt stress, mainly by increasing the osmolyte content, the activities of antioxidative enzymes such as SOD, and APX, reducing malondialdehyde (MDA) content, and upregulation of the expression of stress-related genes. When exposed to salt stress, the AhMYB94 transgenic lines demonstrated a higher Na+ and K+ content and a lower Na+/K+ ratio than the wild type (WT). These results demonstrated that AhMYB94 plays a positive role in enhancing salt tolerance and could be a candidate for improved tolerance of plants to salt stress.