Genome-wide identification and expression profiling of glutathione S-transferase family under multiple abiotic and biotic stresses in Medicago truncatula L.

Glutathione transferases (GSTs) constitute an ancient, ubiquitous, multi-functional antioxidant enzyme superfamily that has great importance on cellular detoxification against abiotic and biotic stresses as well as plant development and growth. The present study aimed to a comprehensive genome-wide identification and functional characterization of GST family in one of the economically important legume plants— Medicago truncatula . Here, we have identified a total of ninety-two putative MtGST genes that code for 120 proteins. All these members were classified into twelve classes based on their phylogenetic relationship and the presence of structural conserved domain/motif. Among them, 7 MtGST gene pairs were identified to have segmental duplication. Expression profiling of MtGST transcripts revealed their high level of organ/tissue-specific expression in most of the developmental stages and anatomical tissues. The transcripts of MtGSTU 5, MtGSTU 8, MtGSTU 17, MtGSTU 46, and MtGSTU 47 showed significant up-regulation in response to various abiotic and biotic stresses. Moreover, transcripts of MtGSTU 8, MtGSTU 14, MtGSTU 28, MtGSTU 30, MtGSTU 34, MtGSTU 46 and MtGSTF 8 were found to be highly upregulated in response to drought treatment for 24h and 48h. Among the highly stress-responsive MtGST members, MtGSTU17 showed strong affinity towards its conventional substrates reduced glutathione (GSH) and 1‐chloro‐2,4‐dinitrobenzene (CDNB) with the lowest binding energy of—5.7 kcal/mol and -6.5 kcal/mol, respectively. Furthermore, the substrate-binding site residues of MtGSTU17 were found to be highly conserved. These findings will facilitate the further functional and evolutionary characterization of GST genes in Medicago .