Involvement of an ent-copalyl diphosphate synthase in tissue-specific accumulation of specialized diterpenes in Andrographis paniculata. (November 2015)

• Record Type: Journal Article
• Authors: Misra, Rajesh Chandra; Garg, Anchal; Roy, Sudeep; Chanotiya, Chandan Singh; Vasudev, Prema G.; Ghosh, Sumit
• Is Part Of: Plant science. Volume 240(2015:Nov.)
• Page Start: 50
• Page End: 64
• Publication Date: 2015-11
• Subjects: Andrographis paniculata -- Ent-copalyl diphosphate synthase -- Ent-labdane-related diterpene -- Medicinal compound -- Specialized metabolism -- Transcriptional variants; Botany -- Periodicals; Botanique -- Périodiques; 580
• DOI: 10.1016/j.plantsci.2015.08.016
• Languages: English
• ISSNs: 0168-9452

Abstract

Graphical abstract: Highlights: Transcripts associated with specialized diterpene accumulation are identified. Two class II diterpene synthases with transcriptional variants are characterized. ApCPS1 may be involved in general metabolism i.e. gibberellins biosynthesis. ApCPS2 is involved in tissue-specific accumulation of specialized diterpenes. ApCPS2 is functionally characterized as ent -copalyl diphosphate synthase. Abstract: Ent -labdane-related diterpene ( ent -LRD) specialized (i.e. secondary) metabolites of the medicinal plant kalmegh ( Andrographis paniculata ) have long been known for several pharmacological activities. However, our understanding of the ent -LRD biosynthetic pathway has remained largely incomplete. Since ent -LRDs accumulate in leaves, we carried out a comparative transcriptional analysis using leaf and root tissues, and identified 389 differentially expressed transcripts, including 223 transcripts that were preferentially expressed in leaf tissue. Analysis of the transcripts revealed various specialized metabolic pathways, including transcripts of the ent -LRD biosynthetic pathway. Two class II diterpene synthases ( ApCPS1 and ApCPS2 ) along with one ( ApCPS1 ′) and two ( ApCPS2′ and ApCPS2 ″) transcriptional variants that were the outcomes of alternative splicing of the precursor mRNA and alternative transcriptional termination, respectively, were identified. ApCPS1 and ApCPS2 encode for 832- and 817-amino acids proteins, respectively, and are phylogenetically related to the dicotyledons ent -copalyl diphosphate synthases ( ent -CPSs). The spatio-temporal patterns of ent -LRD metabolites accumulation and gene expression suggested a likely role for ApCPS1 in general (i.e. primary) metabolism, perhaps by providing precursor for the biosynthesis of phytohormone gibberellin (GA). However, ApCPS2 is potentially involved in tissue-specific accumulation of ent -LRD specialized metabolites. Bacterially expressed recombinant ApCPS2 catalyzed the conversion of (E, E, E)-geranylgeranyl diphosphate (GGPP), the general precursor of diterpenes to ent -copalyl diphosphate ( ent -CPP), the precursor of ent -LRDs. Taken together, these results advance our understanding of the tissue-specific accumulation of specialized ent -LRDs of medicinal importance.