Salt Stress-Induced Changes in In Vitro Cultured Stevia rebaudiana Bertoni: Effect on Metabolite Contents, Antioxidant Capacity and Expression of Steviol Glycosides-Related Biosynthetic Genes
2019
Lucho, Simone Ribeiro | do Amaral, Marcelo Nogueira | Auler, Priscila Ariane | Bianchi, Valmor João | Ferrer, María Ángeles | Calderón, Antonio Asensio | Braga, Eugenia Jacira Bolacel
Stevia rebaudiana is an industrially and medicinally important herb, mainly due to its steviol glycoside content, which is a calorie-free natural sweetener. Moreover, it contains other phytochemicals that make this species potentially beneficial for health. Salt stress affects plant growth, development and plant metabolism. The present study was executed with the objective of evaluating the effect of different NaCl concentrations (0.0, 0.5, 1.0 and 1.5 g L⁻¹) on growth parameters, total soluble sugars, steviol glycosides and phenolic compounds (total soluble phenols, flavonoids and hydroxycinnamic acids), as well as antioxidant capacity (with a FRAP and DPPH assay). We also analysed in this study the expression levels of genes involved in the three stages of the steviol glycosides biosynthesis pathway in S. rebaudiana. Treatment with NaCl decreased root numbers and weights (dry and fresh), while increasing antioxidant capacity (according to the FRAP assay), hydroxycinnamic acid and total soluble sugar content. Furthermore, the up-regulation of several genes (CMS, CMK, HDR and UGT76G1) encoding key enzymes of the steviol glycoside biosynthetic pathways was observed after NaCl treatments. The results provide new insights into the physiological, biochemical and molecular response mechanisms of in vitro-grown stevia plants to NaCl.
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