Identification and validation of WsMYB34 transcription factor for salt tolerance and induced secondary metabolism in Withania somnifera

Abstract In the present study, we have identified a R2R3 type MYB protein from Withania somnifera, i.e., MYB34 (WsMYB34), known for plant development and stress tolerance. MYB transcription factors (MYB TF) have been widely implicated in conferring biotic and abiotic stress tolerance in medicinal plants. To validate this notion, we have analyzed the impact of different concentrations of NaCl on Withania somnifera and the potential of MYB protein in affecting the growth and development by acting as TFs in regulating the expression of defence-related genes and secondary metabolites. Since structural and functional characteristics of MYB TF in W. somnifera remains largely unknown, in-silico analysis was exploited to understand conserved binding motifs, phylogeny, 3-D structure, and role in regulating stress-responsive genes. Based on the domain analysis and phylogenetic assessment, WsMYB34 was found to be a R2R3 type MYB protein, which is phylogenetically closer to Solanum pennellii. In addition, interaction analysis depicted the binding capacity of WsMYB34 protein on the promoter region of a triterpenoid synthesising gene viz; CYP85A69 (having CAACTG cis-regulatory sequence). The comparative microarray analysis also offered the role of WsMYB34 in abiotic stress tolerance. Exposure to NaCl imposed increased withanolide and flavonoid contents and significantly up-regulated the expression of key genes for withanolide and WsMYB34 gene by 0.93–3.68 fold 2.61–3.47 fold respectively. The CYP85A9 gene was also induced by 3.47 fold at 150mM NaCl. In addition, NaCl also affected growth and biochemical behaviour of W. somnifera. Thus, these findings depicted the role of WsMYB34 protein in plant salt tolerance.