The effect of 24-epi-brassinosteroid on the expression of some genes involved in the diosgenin biosynthetic pathway of fenugreek (Trigonella foenum-graecum L.) under high temperature stress

The application of various stimulants, such as abiotic stress, radiation, and growth regulators to increase the quantity of secondary metabolites is one of the interesting research areas. The aim of this study was to investigate the effect of 24-epi-brassinosteroid on the expression of some genes involved in the diosgenin biosynthetic pathway of fenugreek under high temperature stress. The highest expression of cycloartenol synthase (27-fold) was observed at high temperature treatment and 2 ppm of 24-epi-brassinosteroid (at 24 h after heat stress), while the highest expression of SSR gene was 3.5 fold at normal temperature and 5 ppm 24-epi-brassinosteroid. Application of 2 and 5 ppm of 24-epi-brassinosteroid significantly increased squalene epoxidase expression during high temperature stress. Compared to normal condition, squalene epoxidase expression increased 20 and 10 fold at 2 and 5 ppm of 24-epi-brassinosteroid, respectively. Application of 24-epi-brassinosteroid (2 ppm) after 24 hours significantly increased the expression of sterol methyltransferase by 6-fold (Compared to 23°C and non-application of 24-epi-brassinosteroid). Interestingly, compared to normal condition, squalene synthase expression was decreased at high temperature treatment and different levels of 24-epi-brassinosteroid. The results showed that 24-epi-brassinosteroid (2 and 5 ppm) could be used as a suitable stimulus to enhance the expression of some genes involved in the biosynthesis pathway and subsequently to increase the content of the diosgenin.