Transcriptional Regulation of Alkaloid Biosynthesis in /Catharanthus roseus/ Cultures

Abstract

At least 25% of contemporary medicine and 50% of cancer drugs are derived from plants [1]. The diversity of the plant kingdom suggests that plants are one of the largest untapped resources for pharmaceuticals. Catharanthus roseus produces many important compounds, including two powerful anticancer alkaloids, vincristine (VCR) and vinblastine (VBL). However, these alkaloids are produced at extremely low levels, resulting in their costly ($4 – 60 million/kg) and laborious isolation. Approximately 500 kg of dried plant leaves yield only 1 g of VBL. For these reasons, VCR and VBL are excellent targets for biotechnology to increase their production, meet their demand, and decrease their cost. The biosynthesis of VCR and VBL is not entirely known, but involves at least 35 intermediates and 30 enzymes. Transcription factors regulate multiple genes in the this alkaloid pathway and therefore engineering their expression may increase the overall flux through the network and lead to increased production of alkaloids. Jasmonate (JA), a plant hormone produced in response to a pathogen attack, activates a cascade of transcription factors (such as ORCA and ZCT) which control alkaloid production. My research involves elucidating the interactions by which these and other transcription factors regulate alkaloid biosynthesis in order to ultimately control alkaloid production. We are currently identifying the transcriptional activators and repressors of alkaloid genes through profiling gene expression of JA-elicited C. roseus cultures compared to unelicited cultures and creating genetically engineered C. roseus hairy root cultures with optimal transcriptional regulation to maximize alkaloid production.