Identification of imperative enzymes by differential protein expression in Picrorhiza kurroa under metabolite accumulating and non-accumulating conditions.

Picrorhiza kurroa, an endangered medicinal plant found in the North-Western Himalayan region has a number of medicinal properties due to the presence of metabolites picroside-I and picroside-II. It is used in various herbal formulations like Picroliv, Livokin, Picrolax, Livomap, Tefroliv etc. Review of literature revealed that no information is available as of today on the proteome analysis of Picrorhiza kurroa. Hence, we aim to analyse the difference in proteome of Picrorhiza kurroa in response to ~ 17 times higher content of picroside-I at 15°C as compared to its content at 25°C. Thus, differential protein expression was studied. Densitometry analysis of SDS-PAGE gels of samples under two differential conditions of temperature revealed the presence of distinct set of proteins under picroside-I accumulating (15°C) versus non-accumulating (25°C) conditions. Mass spectrometric analysis of these proteins using MALDI-TOF MS followed by protein identification using database search on MASCOT search engine gave interesting results. The significant proteins identified were NAD(P)H-quinone oxidoreductase subunit K, shikimate kinase, ribulose bisphosphate carboxylase small chain and fructokinase fragment. Hence, these findings throw light on the involvement of these enzymes in the crucial physiological processes of Picrorhiza kurroa and can provide an insight into the biosynthesis of picrosides and other secondary metabolites.