Uncovering interconnections between kinases vis-à-vis physiological and biochemical processes contributing to picroside-I biosynthesis in a medicinal herb, Picrorhiza kurroa Royle ex. Benth

Abstract

Picroside-I (P-I) is an iridoid glycoside of Picrorhiza kurroa, a perennial medicinal herb native to North-Western Himalayas, used in the preparation of herbal drug formulations. Natural habitat shoots (PKSS) produce significantly higher P-I content as compared to in vitro shoots (PKS-15 and PKS-25). Although temperature and culture conditions are known to play a major role in influencing P-I biosynthesis in different shoots of P. kurroa, the molecular mechanisms behind signal perception of variable environments are completely unknown. Kinases have been considered as key signaling proteins which control cellular processes involved in adaptability under diverse environments, thereby affecting downstream primary and secondary metabolic pathways. The current study investigated the association of kinases with P-I production and shoot biomass in P. kurroa. Transcriptome mining and in silico transcript abundance in three shoot tissues revealed differentially expressed kinases under high and low P-I accumulating conditions. A total of 521, 473 and 346 transcripts encoding kinases were identified in PKS-25, PKS-15 and PKSS tissues, respectively. Gene expression analysis of 43 selected genes in differential P-I content shoot tissues and genotypes revealed key processes regulated by kinases which might be associated with P-I biosynthesis. Expression of 16 kinases genes involved in plant–pathogen interactions, abiotic stress, wounding, hormonal response and carbohydrate metabolism was observed to be up-regulated in high P-I accumulating conditions, indicating their possible role in eliciting P-I biosynthesis in P. kurroa. Analysis of kinases along with genes involved in controlling shoot biomass productivity revealed that auxin response plays a major role in affecting biomass productivity in in vitro shoots of P. kurroa. This study provides a basic understanding of physiological processes affected under variable environmental conditions leading to differential biosynthesis of P-I in P. kurroa.