L-Deoxy-D-xylulose 5-phosphate synthase from periwinkle: cDNA identification and induced gene expression in terpenoid indole alkaloid-producing cells

Terpenoid indole alkaloids (TIAs) arise from the indole and the monoterpene pathways. The latter route derives from isopentenyl diphosphate (IPP). We report on the isolation and characterization of a cDNA (crdxs) encoding for 1-deoxy-D-xylulose 5-phosphate synthase (DXPS) in Catharnthus roseus suspe nsion cultures. The enzyme catalyses the formation of the precursor of the non-mevalonate pathway leading to IPP biosynthesis. Expression in Escherich ia coli of the truncated DXPS lacking the putative plastid transit peptide revealed that this pseudomature protein was active, crdxs mRNA were detecte d only in TIA producing-cells and the accumulation of transcripts was found to be associated with TIA production. This result corroborates recent stud ies obtained with a labelled precursor, which have given evidence that the non-mevalonate pathway is involved in the biosynthesis of the precursor of TIAs secologanin. (C) 2000 Editions scientifiques et medicales Elsevier SAS .