Investigation of Morphogenetic Differences and Seaweed Extract Stimulated Increase in Biomass and Picroside I Content in Picrorhiza Species

Abstract

Picrorhiza kurroa and P. scrophulariiflora are two endangered species of genus Picrorhiza which possess broad range of pharmacological activities due to presence of Picroside-I (P-I). Shoot development along with P-I biosynthesis was studied in different morphogenetic stages of P. kurroa and P. scrophulariiflora. Expression analysis of genes involved in primary metabolism viz. RBA, HisK, CytO, HK, PK, ICDH, MDH and G6PDH showed high transcript abundance in MS and FD stages vis-à-vis shoot development in P. kurroa and P. scrophulariiflora. Genes such as HMGR, PMK, DXPS, ISPE, GS, G10H, DAHPS and PAL of MVA, MEP, iridoid and shikimate/phenylpropanoid pathways showed significant modulation of expression in SP, MS and FD stages in congruence with P-I content as compared to CM stages of these plant species. newlineAlso effect of seaweed extract (SWE) obtained from Kappaphycus alvarezii with and without growth hormones was studied for in vitro propagation and production of P-I in these plant species. MS media supplemented with SWE (MSS) and growth hormones improved plant growth with increment of 2.67, 2.65 fold in shoot biomass and 1.47, 1.37 fold in shoot number in P. kurroa and P. scrophulariiflora, respectively as compared to control SM at 15 ± 2 °C. SWE as a medium (SWM) showed comparable results and proved to be an economic alternative to MS medium. Both MSS and SWM increased P-I accumulation at 25 ± 2 ºC and 15 ± 2 ºC by 2-4 and 2-3 folds in P. kurroa and P. scrophulariiflora, respectively. newlineFurther, a comparative analysis of SWE with other elicitors was carried out to identify an efficient elicitor for enhanced plant growth and P-I content in these plant species. Results indicated that treatment with SWE showed highest shoot biomass and P-I content in both plant species as compared to SNP, ABA and MeJa. Interestingly, SWE modulated all four integrating secondary metabolic pathways to stimulate P-I biosynthesis. newlineHence, current study has revealed developmental regulation of P-I biosynthesis in P. kurroa and P. scrophul