The elicitors are biotic and abiotic compounds that by stimulation of defensive responses causes biosynthesis and accumulation of secondary metabolites. In this research, the expression of KO, UGT85C2, UGT74G1 and UGT76G1 genes involve in production pathway of steviol glycosides in the Stevia rebaudiana were investigated under chitosan, yeast extract and methyl jasmonate as elicitors. For this purpose, the stevia plants were treated by the elicitors in 3 concentrations of 20, 40 and 80 mg/L and then apical leaves were harvested after one month. The results showed that chitosan in the concentration of 20 (mg/L) significantly increased the expression of UGT85C2 and UGT76G1 genes compared to control plants (16 and 5%). Plus, Chitosan in the concentration of 40mg/l significantly increased the expression of UGT85C2 gene (14%). Methyl jasmonate 20mg/l caused the highest expression of KO gene, which increased by 13% in comparison with control plant. Also, the expression of UGT85C2 gene under the concentration of 20 methyl jasmonate showed a significant increase. According to the results, it was found that increasing the concentrations of chitosan and methyl jasmonate had a negative effect on gene expression profiles of steviol glycosides. Yeast extract in the concentration of 40mg/l significantly increased the expression of UGT85C2 and UGT76G1 genes, which showed 11 and 5% increase in expression, respectively. It was specified that concentration of 40mg/l compared to concentrations of 20 and 80mg/l of yeast extract had a better effect on gene expression enhancement. Hence, according to the results, it can be concluded that chitosan and methyl jasmonate at low concentrations and yeast extract in a moderate concentration can stimulate of the gene expression profiles that involved in the production of steviol glycosides, so increasing the amount of chemical compounds can be effective in the production of secondary metabolites in s. rebaudiana.

Keywords: Chitosan, Elicitor, Gene expression, Methyl jasmonate, Stevia rebaudiana, Steviol glycoside

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