ABSTRACT
Stevia rebaudiana Bertoni is a famous medicinal plant for its low calorific value compounds which are named steviol glycosides (SGs) and they are 150-300 times sweeter than sugar. Among various SGs, stevioside and rebaudioside A considered to be the main sweetening compounds. Soil salinity is one of the most essential stress in the world. Salinity affects the survival and yield of crops. In current study the effects of salinity and osmotic stress caused by different concentration of NaCl (0, 20, 40, 60 and 80 mM) on morphological traits, genes expressionand amount of both stevioside and rebaudioside Aunder in vitro conditions has been investigated. The morphological traits such as bud numbers, root numbers, shoot length (after 15 and 30 days) were evaluated. With increasing salinity, the values of all studied morphological traits decreased. To investigation of UGT74G1 and UGT76G1 genes expression that are involved in the synthesis of SGs, RT-PCR was done and there were significant differences between all media. The highest expression of both genes was observed in plantlets grown on MS media (with NaCl-free). Also, the lowest amounts of gene expression of the both genes were seen in MS+ 60 mM NaCl. Based on HPLC results, the highest amount of both stevioside and rebaudioside A were observed in plantlets grown in MS media (with NaCl-free). Finally, it can be concluded that stevia can survive under salt stress, but it has the best performance in the lower salinity.
Subject(s)
Gene Expression Regulation, Plant/drug effects , Salinity , Stevia/genetics , Chromatography, High Pressure Liquid , Diterpenes, Kaurane/analysis , Genes, Plant , Glucosides/analysis , Plant Leaves/drug effects , Plant Leaves/genetics , Plant Proteins/genetics , Plant Proteins/metabolism , Plant Shoots/drug effects , Plant Shoots/genetics , Plant Shoots/growth & development , Sodium Chloride/pharmacology , Stevia/drug effectsABSTRACT
Stevia rebaudiana is one of the most important biologically sourced and low-calorie sweeteners Bertoni that has a lot of steviol glycosides. Tissue culture is the best for propagation of stevia and micro nutrients can affect both morphological traits and steviol glycosides production. Therefore, the effect of different concentrations of KH2PO4on stevia growth factors and gene expression had been studied by tissue culture methods, RT-PCR and HPLC. According the results, bud numbers had increased significantly in MS + 0.034 mMKH2PO4 media and the highest measured length was seen in plants grown under MS + 0.034 mM KH2PO4 treatment. Also, the highest growth rate (1.396 mm/d) was observed in MS + 0.034 mMKH2PO4.The best concentration of KH2PO4 for expression of UGT74G1 was 0.00425mMand the best one for UGT76G1 expression was 0.017mM. Interestingly, the best media for both stevioside and rebaudioside A accumulation was 0.017mM KH2PO4containing media. There was positive correlation between the best media for gene expression and the best one for steviol glycosides production.
