SlNAC2 overexpression in Arabidopsis results in enhanced abiotic stress tolerance with alteration in glutathione metabolism

Abstract

Plant NAC (NAM, ATAF, and CUC) transcription factors (TF) have important roles to play in abiotic stress responses through activation of a battery of functional genes/transcriptional regulators responsible for stress tolerance. Here we report the cloning of a novel Solanum lycopersicum L., NAC2 TF having 960 nucleotides long CDS (GenBank: KT740994.1). Phylogenetic analysis depicted the similarity of SlNAC2 to other orthologs. SlNAC2 was overexpressed in Arabidopsis thaliana to assess and characterize its role in plant abiotic stress responses. The transgenic events were first confirmed by genomic DNA PCR and qRT PCR; then the T3 generation plants were used for stress assays. Soil stress assay depicted better survivability of the transgenic plants under both salt (NaCl) and drought (PEG) stress. The transgenic plants showed enhanced endurance; with better antioxidative response, reduced accumulation of reactive oxygen species (ROS) molecules and better retention of water in tissue. This study for the very first time analyzed the different stakeholders of the glutathione metabolism in SlNAC2 overexpressing transgenic lines on exposure to both salinity and PEG stress. The expression of the two genes (ɤ-ECS, GS) responsible for glutathione biosynthesis increased with SlNAC2 overexpression. Further glutathione reductase responsible for reduction of glutathione disulfide (GSSG) to glutathione (GSH) also increased significantly which suggested the regulation of glutathione metabolism as a mechanism for the osmotic stress tolerance conferred to plants upon NAC overexpression.