Mass Spectrometric Analysis of Differentially Expressed Proteins in an Endangered Medicinal Herb, Picrorhiza kurroa

Picrorhiza kurroa grown in the Northwestern Himalayan region is used in various herbal formulations but extensive harvesting of this plant has led it to near extinction. The active constituents responsible for the medicinal properties of P. kurroa have been identified as picroside-I and picroside-II which are present in a particular ratio (1 : 1.5) in herbal formulations like Picroliv. The biosynthetic pathway of picrosides has been partially deciphered till date and needs to be elucidated completely. Review of literature revealed that no information is available as of today on the proteome analysis of Picrorhiza kurroa w.r.t. picroside-II biosynthesis. Therefore, with the aim of identifying proteins associated with picroside biosynthesis in Picrorhiza kurroa, differential protein expression was studied under picroside accumulating versus nonaccumulating conditions using SDS-PAGE. A total of 19 differentially expressed proteins were identified using MALDI-TOF/TOF MS followed by MASCOT search. Proteins involved in diverse functions were identified amongst which the most important proteins were glyceraldehyde-3-phosphate dehydrogenase, 1-aminocyclopropane-1-carboxylate oxidase, photosystem I reaction centre subunit V, 2-oxoglutarate ferrous-dependent oxygenase and putative cytochrome P450 superfamily protein because of their role in picroside biosynthesis. These identified proteins provide an insight and a basic platform for thorough understanding of biosynthesis of secondary metabolites and various other physiological processes of P. kurroa.