Expression pattern of fifteen genes of non-mevalonate (MEP) and mevalonate (MVA) pathways in different tissues of endangered medicinal herb Picrorhiza kurroa with respect to picrosides content

Picrorhiza kurroa, has become an endangered medicinal herb due to excessive utilization, therefore it necessitates the understanding of biology and molecular basis of major chemical constituents i.e. Picroside-I (P-I) and Picroside-II (P-II). Estimation of P-I and P-II in different tissues of P. kurroa showed that shoots contain only P-I whereas P-II is present only in roots. Differential conditions with varying concentrations of P-I (0-27 mu g/mg) and P-II (0-4 mu g/mg) were selected. Four genes of MEP pathway; DXPS, ISPD, ISPE, MECPS and one gene of MVA pathway PMK showed elevated levels of transcripts in shoots (57-166 folds) and stolons (5-15 folds) with P-I contents 0-27 mu g/mg and 2.9-19.7 mu g/mg, respectively. Further HDS and DXPR genes of MEP pathway showed higher expression similar to 9-12 folds in roots having P-II (0-4 mu g/mg). The expression of ISPH and ISPE was also high similar to 5 folds in roots accumulating P-II. GDPS was the only gene with high transcript level in roots (9 folds) and shoots (20 folds). Differential biosynthesis and accumulation of picrosides would assist in regulating quality of plant material for herbal drug formulations.