Interplay of transcription factors orchestrating the biosynthesis of plant alkaloids

Abstract

Plants produce a range of secondary metabolites primarily as defence molecules. A plant has to invest considerable energy to synthesise alkaloids, and sometimes they are even toxic to themselves. Hence, the biosynthesis of alkaloids is a spatiotemporally regulated process under quantitative feedback regulation which is accomplished by the signal reception, transcriptional/translational regulation, transport, storage and accumulation. The transcription factors (TFs) initiate the biosynthesis of alkaloids after appropriate cues. The present study recapitulates last decade understanding of the role of TFs in alkaloid biosynthesis. The present review discusses TF families, viz. AP2/ERF, bHLH, WRKY, MYB involved in the biosynthesis of various types of alkaloids. It also highlights the role of the jasmonic acid cascade and post-translational modifications of TF proteins. A thorough understanding of TFs will help us to decide a strategy to facilitate successful pathway manipulation and in vitro production.

Keywords: AP2/ERF; JA; Regulation; Transcription factors.

Fig. 1

Catharanthus roseus transcription factors network and biosynthesis of TIA green arrows depict upregulation while red arrows depict downregulation by the TF. Yellow arrows indicate TIA pathway

Fig. 2

ERF and bHLH TFs in nicotine biosynthesis. ERF and bHLH TFs binding to GCC and G-box, respectively in the promoter regions of nicotine biosynthetic genes, black curved arrow indicates activation of ERF TFs by bHLH TFs through unknown factors. Yellow arrows indicate nicotine pathway

Fig. 3

Transcription factors involved in BIA biosynthesis. TFs binding to the promoters of BIA biosynthetic genes. Yellow arrows indicate BIA pathway. TYDC tyrosine decarboxylase, NCS norcoclaurine synthase, 6′OMT norcoclaurine 6-O-methyltransferase, CNMT coclaurine N-methyltransferase, NMCH N-methylcoclaurine 3′-hydroxylase, 4′OMT 3′-hydroxy-N-methylcoclaurine 4′-O-methyltransferase, BBE berberine bridge enzyme, TNMT tetrahydroprotoberberine cis-N-methyltransferase, SMT scoulerine 9-O-methyltransferase

Fig. 4

JA cascade. JA-Ile (JA-isoleucine) activating SCF complex and releasing MYC type bHLH TFs. Released MYC TF activates other TFs expression. MAP cascade carrying out phosphorylation of TF