Transcriptome Profiling Reveal Key Hub Genes In Co-Expression Networks Involved In Iridoid Glycosides Biosynthetic Machinery In Picrorhiza Kurroa

Picrorhiza kurroa is a medicinal herb rich in hepatoprotective iridoid glycosides, picroside-I (P-I) and picroside-II (P-II). The biosynthetic machinery of picrosides is poorly understood, therefore, 'no-direction' gene coexpression networks were used to extract linked/closed and separated interactions in terpenoid glycosidesspecific sub-networks. Transcriptomes generated from different organs, varying for P-I and P-II contents such as shoots grown at 15 and 25 degrees C and nursery-grown shoots, stolons, and roots resulted in 47,726, 44,958, 40,117, 66,979, and 55,578 annotated transcripts, respectively. Occurrence of 2810 +/- 136 nodes and 15,626 +/- 696 edges in these networks indicated intense, co-expressed, closed loop interactions. Either deregulation/inhibition of abscisic acid (ABA) biosynthesis/signaling or constitutive degradation of ABA resulted in organ-specific accumulation of P-I and P-II. Biosynthesis, condensation and glucosylation of isoprene units may occur in shoots, roots or stolons; but addition of phenylpropanoid moiety and further modification/s of the iridoid backbone occurs mainly inside vacuoles in roots.