Changes in medicinal alkaloids production and expression of related regulatory and biosynthetic genes in response to silver nitrate combined with methyl jasmonate in Catharanthus roseus in vitro propagated shoots.

Antihypertensive compound ajmalicine and antileukemic vincristine and vinblastine are three important terpenoid indole alkaloids produced by Catharanthus roseus (Apocynaceae). This study has been done to investigate the effects of methyl jasmonate (100 μM) and silver nitrate (50 and 100 μM) individually and simultaneously on the production of mentioned important medicinal alkaloids (vincristine, vinblastine, ajmalicine, vindoline and catharanthine) and the expression profile of related regulatory and biosynthetic genes in micropropagated shoots of C. roseus. The effects of these treatments are also investigated on non-enzymatic defensive metabolites (total phenolics, flavonoids and carotenoids) and antioxidant enzymes activities (peroxidase, EC 1.11.1.7, catalase, EC 1.11.1.6 and superoxide dismutase, EC 1.15.1.1). Changes of dry weight, quantity of lipid peroxidation, and photosynthetic pigments contents have been measured as well. The results showed increased contents of alkaloids and expression levels of investigated regulatory (Mitogen-activated protein kinase3 and Octadecanoid-responsive Catharanthus AP2-domain3) and biosynthetic (strictosidine synthase, geissoschizine synthase, deacetylvindoline acetyltransferase and peroxidase1) genes under the employed treatments. The maximum yields of these alkaloids and the highest levels of the mentioned genes expression were observed under 100 μM methyl jasmonate in combination with 100 μM of AgNO3 after seven days. The employed treatments induced increased lipid peroxidation, higher levels of enzymatic antioxidants activities and more production of non-enzymatic defensive metabolites which shows activity of plant defensive system. The results suggest that silver nitrate and methyl jasmonate signalling pathways may have cross talks and their simultaneous application make an effective combination for elicitation of medicinal alkaloids biosynthesis in C. roseus micropropagated shoots.