Alkaloids production and antioxidant properties in Catharanthus roseus (L.) G. Don. shoots and study of alkaloid biosynthesis-related gene expression levels in response to methyl jasmonate and putrescine treatments as eco-friendly elicitors

Introduction: This study aimed to determine the effects of methyl jasmonate (MJ) combined with putrescine as eco-friendly elicitors on secondary metabolism and gene expression of alkaloid biosynthetic pathway in Catharanthus roseus in vitro-propagated shoots. Methods: The expression of mitogen-activated protein kinase 3 and the transcription factor, octadecanoid-responsive Catharanthus AP2-domain3, upstream of plant alkaloids' biosynthetic pathway, and of key genes in the pathway (CrPRX1, STR, DAT, and GS) are investigated as well using qRt-PCR. Antioxidant enzyme (superoxide dismutase, peroxidase, and catalase) activities and nonenzymatic antioxidants (phenolics, flavonoids, and carotenoids) contents have studied to determine the stress levels of the plant by spectrophotometer. Results: Results showed increased contents of non-enzymatic antioxidants after 4-8 hr and enzymatic antioxidants activities after 24 hr. Alkaloids contents increased mostly after 1 week. The investigated signaling genes upregulated after 8 hr and biosynthetic genes after 24 hr of treatments. Combined treatments had more positive effects on gene expression levels, antioxidant responses, and secondary metabolite production than MJ individually. Discussion: Increased effects of combined elicitor on genes expression may be due to cross talks between their signaling pathways. Combination of MJ and putrescine can be used as an eco-friendly elicitor for enhancing the production of economically important alkaloids in C. roseus.