Expression analysis of some genes involved in Terpenoid Indole Alkaloids pathway in periwinkle (Catharanthus roseus) following foliar application of salicylic acid

Catharanthus roseus is an ornamental and evergreen plant, which is used in cancer treatment due to production of important alkaloids, Vinblastine and vincristin. C.  roseus is also of great importance for pharmaceutical industry. Vinblastine and vincristine in the terpenoid indole-alkaloid pathway (TIAs) synthesis in Low level. Difficulties with chemical synthetic production and low production level in plant lead to find practical solutions to increase the amount of these two economically important alkaloids. It seems plant growth regulators such as salicylic acid (SA) induce expression of major genes involved in vinblastine and vincristine production. In addition to increasing in the alkaloid content, especially vinblastine and vincristine, application of SA activates the plant defense system and under normal condition and in dealing with stresses, improve C.  roseus yeild. To this end, the relative expression of terpenoid indole alkaloids (TIAs) pathway genes in all three Indole, Terpenoid and Alkaloid pathways studied following foliar application of SA at a concentration of 0.01 mM by using qRT-PCR analysis. The results of this experiment showed that the mRNA transcript level of the first gene in the phenolic pathway reduced, although the down-regulation was not statistically significant. The transcript level of TIAs pathway genes were also increased after SA foliar application. The highest 4-O-acetyltransferase (Dat) gene transcription level observed at 24 and 48 h after treatment, suggesting Dat could be a primary responsive gene to SA treatment.