(640f) Enhancing Production of Pharmaceutically Valuable Alkaloids from Hairy Root Cultures of Catharanthus Roseus through Genetic Engineering of Key Transcription Factors

The medicinal plant, Catharanthus roseus, is the source of pharmaceutically valuable anticancer alkaloids, vincristine (VCR) and vinblastine (VBL). These alkaloids are produced only in C. roseus and at extremely low levels (0.0002 wt%). Due to their low levels, the isolation of these compounds is both laborious and costly, ranging from $4 to $60 million/kg. Despite these barriers, these alkaloids have been effectively used to treat cancer for over 50 years.

  The biosynthesis of VCR and VBL is not entirely known but involves at least 35 intermediates and 30 enzymes. In an effort to increase VCR and VBL, key enzymes in the C. roseus biosynthetic pathway have been overexpressed but this strategy has proven unsuccessful since the enzymatic bottleneck is shifted downstream. However, transcription factors regulate multiple genes in the pathway and therefore engineering their expression may potentially increase the overall flux through the network and lead to increased production of the desired compounds.

  Here, we study key transcription factors involved in regulating multiple alkaloid biosynthetic enzymes. Since ZCT1 (Zinc finger Catharanthus transcription factor) is a known repressor of alkaloid biosynthetic enzymes, we established stable C. roseus hairy root cultures with silenced ZCT1 expression through RNA interference (RNAi). The results of silencing this key repressor and their implications in alkaloid biosynthesis in C. roseus will be discussed.