An insight into conflux of metabolic traffic leading to picroside-I biosynthesis by tracking molecular time course changes in a medicinal herb, Picrorhiza kurroa

Picroside-I (P-I) is a member of the iridoid glycosides family of natural products, which are used to treat liver disorders. The growing medicinal need for this benign compound has stimulated the present study to identify genes important for the biosynthesis of P-I. In this study, molecular screens have been generated using gene expression patterns obtained by quantitative RT-PCR which have extended the knowledge of genes associated with P-I biosynthesis. A total of 13 genes encoding the rate limiting enzymes of different pathways, were analyzed by qRT-PCR in Picrorhiza kurroa shoots collected at 0, 10, 20, 30 and 40 days. The results showed that five of the genes (HK, DXPS, ISPD, HMGR and PMK) are supposed to be essential for P-I biosynthesis up to 20 days while DAHPS and G-10-H, in conjunction might assist P-I biosynthesis between 20 and 30 days of P. kurroa growth. This is apparently the first report on the molecular aspects of different pathways integrated in P-I biosynthesis. Moreover, principal component analysis prediction also corroborated the genes selection by identifying genes signatures for different samples (collected at different time intervals) and supported the link between samples and gene expression patterns. Overall, this study capitalizes on dynamic gene expression patterns obtained in response to the P-I stimuli under different stages of P. kurroa growth which are likely to define the regulatory steps in P-I biosynthesis.