Structural and functional prediction of WsMYB34 transcription factor in Withania somnifera (L.) Dunal by deciphering its role in NaCl-induced secondary metabolism

Abstract

In the present study, a MYB transcription factor from Withania somnifera, was identified i.e., WsMYB34, known for development and stress tolerance in plants. MYB transcription factors have been widely implicated in conferring stress tolerance in medicinal plants. To validate this notion, we analyzed the impact of different concentrations of NaCl on W. somnifera and hypothesized the potentiality of MYB protein in regulating the expression of secondary metabolite-related genes by docking approach. Since structural and functional characteristics of R2R3 type MYB TF in W. somnifera remain largely unknown, in-silico analysis was exploited to understand conserved binding motifs, phylogeny, 3-D structure, and role in combating stress. Based on these outcomes, WsMYB34 was found to be an R2R3 type MYB protein, which is phylogenetically close to that of Capsicum baccatum (CbMYB34). In addition, in-silico 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 MYB34 in abiotic stress tolerance in model plants. Exposure to NaCl imposed increased withanolide and flavonoid contents and significant up-regulation of key genes for withanolide and WsMYB34 gene by 0.93–3.68 and 2.61–3.47-folds respectively. The enhanced expressivity of transcript encoding WsMYB34 indicated its possible role in inducing terpenes, flavonoids, anthocyanins, and trichome organogenesis to provide defence against salt. In addition, NaCl caused a reduction in morphology and photosynthesis of W. somnifera. However, enhanced contents of phenolics, proline, MDA, and free radical scavenging activities were observed.