Genome-wide identification and expression analysis of SnRK2 gene family in mungbean (Vigna radiata) in response to drought stress

Drought stress causes lower crop production globally. Plants have acquired many adaptations to overcome drought stress. Mungbean (Vigna radiata (L.) R.Wilczek) is a legume crop widely cultivated in South, East and Southeast Asia. It is grown in high-temperature areas where drought is the main cause of reduced plant growth and productivity. Plants cope with drought stress by activating different signalling mechanisms. The sucrose non-fermenting-1-related protein kinase 2 family (SnRK2s) is known to play vital roles in osmotic stress and in abscisic acid (ABA) signalling pathways by phosphorylating downstream targets. The genes encoding SnRK2s in mungbean and their detailed characterisation remain unexplored. We have conducted extensive genome-wide analysis for gene prediction, in silico gene analysis, evolutionary analysis and gene-expression profiling under drought-stress conditions by quantitative real-time PCR. Through genome-wide analysis, eight SnRK2 genes were predicted in the mungbean genome and were assigned the names VrSnRK2.1-VrSnRK2.8, according to their order on the chromosomes. The VrSnRK2 genes identified were classified into three clusters based on their phylogenetic relationship with those of Arabidopsis thaliana. Drought stress was imposed on 11-day-old mungbean plants by completely withholding water for 3 days. According to real-time qPCR data, the expression of most of the VrSnRK2 genes was induced by drought stress, indicating their role in the drought-stress response. One of the genes, namely SnRK2.6c, showed highest expression level (12-fold) under drought stress, possibly indicating a critical role under water-deficit conditions. These data provide important information about the VrSnRK2 gene family in mungbean. The results will help in future functional characterisation of VrSnRK2 genes.