Investigating the Physiological Responses and the Expression of Effective Genes in Steviol Glycosides Production in Stevia (Stevia rebaudiana)

Stevia plant is one of the most important medicinal plants used to control diabetes due to its sweetening properties and low calories. Stevia is cultivated in many parts of the world, and to increase its sweetening properties, the effects of many different factors have been tested on this plant. In this research, we investigated the effect of elements related to metal oxidants on the induction of molecular levels and transcription. Thus, the activity of 3 key genes named CPPS, HDS, and GGDPS in response to six different metal oxidants named Cro3, Pbo, Fe2O3, Ag2O, Bao, and Tio2 was carried out in this research. The results showed that the increased concentration of metal oxides, especially Fe2O3 and TiO2, escalates gene expression in the biosynthesis of sweeteners extracted from stevia leaves. Also, related to all treatments, the higher the concentration, the higher the gene expression. Among all metal oxide treatments, Pbo and Bao resulted in low gene expression for CPPS, HDS, and GGDPS genes. On the other side, control showed the lowest expression regarding all three surveyed genes, indicating that using metal oxides can achieve higher production of sweeteners in stevia plants. The results of this research determined that physiological characteristics are affected by metal oxide treatments. Also, the expression of genes effective in the production of steviol glycosides, which is one of the important sweetening factors of this plant in the leaves, increases under the influence of these treatments. As a result, it can be said that the use of these treatments can have an increasing effect on the amount of sweetening of the plant.