The indole alkaloid tryptamine produced in transgenic Petunia hybrida

Tryptophan decarboxylase (TDC) from Catharanthus roseus (periwinkle) conver ts tryptophan to the indole-alkaloid tryptamine, an anti-insect compound. T his TDC cDNA was transformed and expressed in transgenic Petunia hybrida un der the control of the strong and constitutive 35S promoter from cauliflowe r mosaic virus. Kanamycin screening and Southern hybridization with the TDC cDNA confirmed plant transformation. Northern analysis indicated greater T DC mRNA accumulation in transgenic plants compared to non-transformed plant s. Additionally, eight-fold more tryptamine accumulated in leaves of kanamy cin resistant transgenic plants compared to non-transformed plants. Flower petals from the transgenic plants contained lower tryptamine levels than th eir leaves. Because tryptamine titers were higher in transformed plants com pared to controls, over-expression of the TDC enzyme may partially overcome endogenous tryptamine catabolism and/or other negative biosynthetic regula tion. Future alteration of tryptamine breakdown in Petunia may further incr ease total endogenous tryptamine concentrations, potentially discouraging i nsect reproduction on these transgenic plants. (C) 1999 Editions scientifiq ues et medicales Elsevier SAS.