Functional genomics of sterol glycosyltransferase gene SGT family members of Withania somnifera using SGT knockout mutants of Arabidopis thaliana

Abstract

Withania somnifera Dunal (L.) known as ashwagandha, is widely used in Ayurvedic newlinemedicine. It is a popular medicinal plant in South East Asia and Southern Europe. The newlinemajor biochemical constituents are steroidal alkaloids and steroidal lactones in a class newlineof constituents called withanolides and glycowithanolides or withanosides. newlineWithanolides and withanosides have been reported to possess anti-inflammatory, newlineantitumor, antistress, antioxidant, immunomodulatory and rejuvenating properties. newlineWithanosides are steroidal lactones with one or more glucose units attached to C-3 or newlineC-27 positions. Due to glycosylation, the activity of these molecules is changed; newlinehence there is a change in their metabolic participation. newlineGlycosylation is one of the primary sedative mechanisms that plant utilizes in newlineorder to maintain metabolic homeostasis. Glycosylation plays diverse roles, like, newlineaccumulation of sterol glycoside in individual plants and secondary plant metabolism. newlineThe important chemical roles for glycosylation are stabilization, detoxification newline(reduced activity) and solubilization (increased polarization). Glycosyltransferases newline(GTs) are the enzymes responsible for glycosylation of plant compounds. newlineGlycosyltransferases can typically transfer single or multiple activated sugars from newlinenucleotide sugar donors to a wide range of small molecular acceptors of plants. newlineSterols occur either in free form or as sterol conjugates. Sterol newlineglycosyltransferases (SGTs) in plants catalyze glycosylation of phytosterols and newlinerelated compounds to generate their glyco-conjugates. These are biosynthesized by a newlineUDP-glucose: sterol glucosyltransferase (EC 2.4.1.173). The glycosyltransferase newlinemultigene family is categorized into 94 numbered families based on sequence newlinesimilarity, signature motifs, stereochemistry of the glucoside linkage formed, and newlineknown target specificity (http://afmb.cnrs-mrs.fr/CAZY). Of these 94 families, SGTs newlinehave been grouped into Family 1 of the classification scheme. SGTs play an important newlinerole in metabolic plasticity during adaptive responses. Many secondary metabolites newlineare derived from the sterol pathways which are important in defense mechanisms newlineagainst pathogen. The ratio of sterol and their modified counterparts varies when newlineplants adapt to environmental conditions, which leaves an area to be explored by newlinelooking for enzymes involved in sterol modifications. newline