Comparative coexpression networks pinpoint acyltransferases decorating structures of major iridoid glycosides in a medicinal herb, Picrorhiza kurroa

Abstract

Picrorhiza kurroa, a hepatoprotective Himalayan medicinal herb contains a variety of iridoid glycosides mainly present in stolons and roots, contributing to several medicinal properties. However, off late the herb has been declared as endangered, therefore, warranting alternate production routes for those iridoid glycosides. Catalpol, the major intermediary compound, is transformed into several iridoid glycosides through acylation by acyltransferase enzymes. In current study, we performed comparative gene co-expression-networks analysis among transcriptomes derived from different tissues/organs of P. kurroa varying for contents of iridoid glycosides to pinpoint major hubs associated with BAHD class of acyltransferases. Our analysis also captured other components co-expressed with major Acyltransferases hubs, which provided us leads as novel edges possibly contributing to other components of biosynthetic machinery. Some of the key interacting components such as Phytyl ester synthase (PES1 and PES2), callose synthase, serine carboxy peptidase like protein, polyphenol oxidase and UDP-glycosyltransferase were identified, which are possibly contributing to variations in the contents of iridoid glycosides in different tissues/organs of P. kurroa. Furthermore, the functional association of identified BAHD-ATs (SS_3469, STS_4084, STS_4241, STS_8424, SR_4494, and SR_4510) was evaluated through molecular docking to pinpoint probable BAHD-ATs transforming structural modifications of iridoid glycosides.