Abstract

The response of three key genes: strictosidine synthase (str1), tryptophan decarboxylase (tdc) and secologanin synthase (cyp72A1) of the wild plant species, Catharanthus roseus to different plant tissue culture treatments was studied. These genes encode enzymes acting early in the biosynthetic pathway of terpenoid indole alkaloids. In vitro culture system conditions involved the application of three sucrose (40, 50 and 60 g/L), three benzyl adenine (0.1, 0.2 and 0.4 mg/L) and two jasmonic acid (10 and 100 µM) concentrations. Quantitative RT-PCR (qRT-PCR) using SYBR Green I was used to analyze the changes in expression of the three genes in response to different media recipes. The maximum folding of str1 expression (1.9x) between treated and untreated callus was obtained under ba2 (0.2 mg/L benzyl adenine) treatment. Relatively high folding values of 1.8x and 1.7x were obtained in S2 (50 g/L sucrose) and ba1 (0.1 mg/L benzyl adenine), respectively. Two-fold increase in gene expression of tdc was obtained when C. roseus callus was treated with 10 µM jasmonic acid (ja1), while only 1.5x was obtained when callus was treated with 100 µM jasmonic acid (Ja2). The maximum expression of cyp72A1 gene (4.6x) was observed under ba2 treatment, when the callus was treated with 0.2 mg/L benzyl adenine. This emphasized the influence of BA on up-regulation of this gene.

Key words: Strictosidine synthase, tryptophan decarboxylase, secologanin synthase, Catharanthus roseus, terpenoid indole alkaloids.