Abstract
Catharanthus roseus is a medicinal plant species having more than 100 alkaloids, including two anticancer alkaloids vinblastine and vincristine. RNA-seq data of a number of organs and treatments of C. roseus was utilized in order to identify organ-specific transcription factors (TFs) and those probably linked to the monoterpenoid indole alkaloids (MIA) pathway. Organ-specific TF transcripts as well as those probably regulate genes in the MIA pathway were identified. Expression of several TF transcripts was exclusive in organs like flower, mature leaf, root/hairy root, stem and seedling. Transcripts encoding peroxidases 1 and 12 were up-regulated in mature leaf, while down-regulated in the hairy roots. TF transcripts in hairy roots indicated no differential response when knocked down for the tdc gene (TDCi) compared to wild type. A number of eight transcripts of the MIA biosynthetic pathway concordantly expressed with TFs in the steps between tryptophan and vindoline biosyntheses. These transcripts are tdc, strl, sgd, t16h, omt, nmt, d4h and dat. The most common transcription factor families involved members of bHLH, MYB and WRKY whose genes are either induced by ABA or JA (or MeJA) or regulated during adverse condition. Results of virus induced gene silencing (VIGS) of two versions of bHLH25 gene confirmed its role in driving expression of strl gene. This study highlights the regulatory frameworks in C. roseus with emphasis to the TIA pathway to be used in improving alkaloid biosynthesis via metabolic engineering.