Unravelling complexity of picrosides biosynthetic pathway gene paralogues in a medicinal herb Picrorhiza kurroa Royle ex Benth

Abstract

Picrorhiza kurroa is a medicinal herb with Picroside-I and Picroside-II as the major chemical newlineconstituents implicated in various pharmacological activities. Being endangered status of herb newlinecoupled with chances of adulteration of raw material, a need has been felt to develop newlinealternative production platforms for the production of picrosides, however, that would require newlinea thorough understanding of biosynthetic pathways. The challenge with biosynthetic newlinepathways of secondary metabolites in plants has been the occurrence of multiple copies of newlinegenes, thereby, complicating the process of identifying a gene paralogue(s) associated with newlinethe biosynthesis of a secondary metabolite in a specific tissue/organ. The final steps in newlinepicrosides biosynthesis are the esterification of catalpol (iridoid backbone) for the formation newlineof Picroside-I and Picroside-II, which are catalysed by acyltransferase(s). The current study newlineutilized differential NGS transcriptomics, TPM screening and qRT-PCR for the identification newlineof multiple copies of key genes in the biosynthetic pathway. On the other hand comparative newlinetranscriptomics between shoots, roots and stolons followed by expression analysis was used newlineto identify putative acyltransferase(s) catalyzing final steps in decorating picrosides newlinestructures. Further, for the identification of acyltransferase encoding transcripts that might newlineplay role in Picroside-II biosynthesis, the six Picroside-II acyltransferase encoding transcripts newlinetranslations were subjected to molecular docking studies to shortlist putative acyltransferase newlinethat might play significant role in Picroside-II production. Thus, the identified gene newlineparalogues and acyltransferases can enhance Picrosides production in shoots of Picrorhiza newlinekurroa under in-vitro conditions. This knowledge will help researchers better understand the newlinemolecular basis of picrosides biosynthesis towards designing genetic improvement strategies newlineto increase picrosides content in Picrorhiza kurroa. newline