title: Comparative transcriptome analysis in different tissues of a medicinal herb, Picrorhiza kurroa pinpoints transcription factors regulating picrosides biosynthesis.
abstract: Transcriptional regulation of picrosides biosynthesis, the iridoid glycosides of an endangered medicinal herb, Picrorhiza kurroa, is completely unknown. P. kurroa plants obtained from natural habitat accumulate higher picrosides than in-vitro cultured plants, which necessitates identification of transcription factors (TFs) regulating their differential biosynthesis. The current study investigates complete spectrum of different TF classes in P. kurroa transcriptomes and discerns their association with picrosides biosynthesis. Transcriptomes of differential picroside-I content shoots and picroside-II content roots were mined for seven classes of TFs implicated in secondary metabolism regulation in plants. Key TFs were identified through in silico transcript abundance and qPCR analysis was performed to confirm transcript levels of TFs under study in differential content tissues and genotypes. Promoter regions of key picrosides biosynthetic pathway genes were explored to hypothesize which TFs can possibly regulate target genes. A total of 131, 137, 107, 82 and 101 transcripts encoding different TFs families were identified in PKS-25, PKS-15, PKSS, PKR-25 and PKSR transcriptomes, respectively. ERF-18, bHLH-104, NAC-25, 32, 94 and SUF-4 showed elevated expression in roots (up to 37 folds) and shoots (up to 195 folds) of plants obtained from natural habitat, indicating their role as activators of picrosides biosynthesis whereas, elevated expression of WRKY-17, 40, 71 and MYB-4 in low picrosides content conditions suggested their down-regulatory role. In silico analysis of key picrosides biosynthetic pathway gene promoter regions revealed binding domains for ERF-18, NAC-25, WRKY-40 and MYB-4. Identification of candidate TFs contributing towards picrosides biosynthesis is a pre-requisite for designing appropriate metabolic engineering strategies aimed at enhancing picrosides content in vitro and in vivo.
authors.affiliation: Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, 173234, Himachal Pradesh, India.
authors.forename: Ira
authors.initials: I
authors.lastname: Vashisht
authors.affiliation: Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, 173234, Himachal Pradesh, India.
authors.forename: Tarun
authors.initials: T
authors.lastname: Pal
authors.affiliation: Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, 173234, Himachal Pradesh, India.
authors.forename: Hemant
authors.initials: H
authors.lastname: Sood
authors.affiliation: Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, 173234, Himachal Pradesh, India. rajinder.chauhan@juit.ac.in.
authors.forename: Rajinder S
authors.initials: RS
authors.lastname: Chauhan
mesh_terms: D053898:Biosynthetic Pathways; D002934:Cinnamates / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D057888:Iridoid Glucosides / Q000378:metabolism*; D032261:Picrorhiza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D010946:Plants, Medicinal / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D059467:Transcriptome
chemical_list: D002934:Cinnamates; D057888:Iridoid Glucosides; D010940:Plant Proteins; D014157:Transcription Factors; C109270:picroside I; C416837:picroside II
keywords: Picrorhiza kurroa; Picrosides; Secondary metabolism; Transcription factors; Transcriptome