LAUSR

Abstract Several environmental factors such as weather, season, temperature, biotic, and abiotic factors affect the plant productivity and content of secondary metabolites. Present work is carried out to investigate the physiological and biochemical effects owing to seasonal variation on prestigious Indian medicinal plant, Withania somnifera. Furthermore, the regulatory role of transcription factors (TFs) in the management of plant growth and withanolide biosynthesis was also analysed. Direct sowing of our developed elite variety of W. somnifera i.e. NMITLI-118 was done in two contrasting seasons; winter (NMITLI-118-W) and summer (NMITLI-118-S) seasons. Plant growth parameters such as plant biomass production, plant height, shoot/root production, and total photosynthetic pigments were recorded in both and compared for analysis in terms of productivity. Key pathway genes having role in terpenoid-isoprenoid pathway viz WsDXS, WsDXR, WsHMGR, and WsCAS were higher in expression. Higher pathway genes expression also reflected higher expression of secondary metabolite-with-anolide content in different tissues of W. somnifera (NMITLI-118-W than NMITLI-118-S). Tissue‐wide gene expression analysis of important transcription factors such as WsWRKY, WsbHLH, WsMYB, and WsWuschel reflected their involvement in tissue-specific regulation of withanolide biosynthesis and WsAP-2ERF & WsLWD1 in the regulation of plant growth and development. Our results established the relation between biomass production and total photosynthetic pigments & withanolide biosynthesis. This is the first study which revealed the effect of the seasonal variation on W. somnifera under natural field conditions in overall productivity, pathway gene expression and in withanolide biosynthesis. The study also reflected the regulation of various transcription factors in secondary metabolite biosynthesis and in plant growth & development in W. somnifera.