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Two Tabersonine 6,7-Epoxidases Initiate Lochnericine-Derived Alkaloid Biosynthesis in Catharanthus roseus.

Inês CarqueijeiroStephanie BrownKhoa ChungThu-Thuy DangManish WaliaSébastien BesseauThomas Dugé de BernonvilleAudrey OudinArnaud LanoueKevin BilletThibaut MunschKonstantinos KoudounasCéline MelinCharlotte GodonBienvenue RazafimandimbyJohan-Owen de CraeneGaëlle GlévarecJillian MarcNathalie Giglioli-Guivarc'hMarc ClastreBenoit St-PierreNicolas PaponRodrigo B AndradeSarah E O'ConnorVincent Courdavault
Published in: Plant physiology (2018)
Lochnericine is a major monoterpene indole alkaloid (MIA) in the roots of Madagascar periwinkle (Catharanthus roseus). Lochnericine is derived from the stereoselective C6,C7-epoxidation of tabersonine and can be metabolized further to generate other complex MIAs. While the enzymes responsible for its downstream modifications have been characterized, those involved in lochnericine biosynthesis remain unknown. By combining gene correlation studies, functional assays, and transient gene inactivation, we identified two highly conserved P450s that efficiently catalyze the epoxidation of tabersonine: tabersonine 6,7-epoxidase isoforms 1 and 2 (TEX1 and TEX2). Both proteins are quite divergent from the previously characterized tabersonine 2,3-epoxidase and are more closely related to tabersonine 16-hydroxylase, involved in vindoline biosynthesis in leaves. Biochemical characterization of TEX1/2 revealed their strict substrate specificity for tabersonine and their inability to epoxidize 19-hydroxytabersonine, indicating that they catalyze the first step in the pathway leading to hörhammericine production. TEX1 and TEX2 displayed complementary expression profiles, with TEX1 expressed mainly in roots and TEX2 in aerial organs. Our results suggest that TEX1 and TEX2 originated from a gene duplication event and later acquired divergent, organ-specific regulatory elements for lochnericine biosynthesis throughout the plant, as supported by the presence of lochnericine in flowers. Finally, through the sequential expression of TEX1 and up to four other MIA biosynthetic genes in yeast, we reconstituted the 19-acetylhörhammericine biosynthetic pathway and produced tailor-made MIAs by mixing enzymatic modules that are naturally spatially separated in the plant. These results lay the groundwork for the metabolic engineering of tabersonine/lochnericine derivatives of pharmaceutical interest.
Keyphrases
  • cell wall
  • genome wide
  • genome wide identification
  • copy number
  • transcription factor
  • high throughput
  • hydrogen peroxide
  • single cell
  • blood brain barrier
  • saccharomyces cerevisiae