Methyl jasmonic acid induced expression pattern of terpenoid indole alkaloid pathway genes in Catharanthus roseus seedlings

Madagascar periwinkle (Catharanthus roseus) produces diverse terpenoid indole alkaloids (TIAs), including the anti-cancer drugs vincristine and vinblastine. In this study, the effects of methyl jasmonic acid (MeJA) treatment on TIA metabolism and gene expression in seedlings were analyzed. Several reference genes were also isolated from periwinkle. These reference genes, as well as ribosomal protein (RSP9) and cyclophilin (CYC) genes, were characterized to determine which are most suitable for use as expression profiling control genes. The results show that TIA genes exhibit significant variation in the magnitude and timing of induction by MeJA. ORCA3, a jasmonate-responsive APETALA2 (AP2)-domain transcription factor gene, exhibited the greatest increase in transcript levels, with increases up to 25 fold observed 0.5 h after MeJA treatment. MeJA-induced increases in transcript levels occurred in the following order: ORCA3, desacetoxyvindoline 4-hydroxylase (D4H), strictosidine synthase (STR), tryptophan decarboxylase (TDC), geraniol 10-hydroxylase (G10H) and cytochrome P-450 reductase (CPR). The results suggest that variations in the timing of MeJA induced increases in TIA transcript levels might be related to complex interactions between different transcription factors, such as ORCA3, and other factors. CrEF1 alpha and CrUBQ11 are the most stable genes out of the 8 tested under the conditions of these experiments.