Abscisic acid promotes selenium absorption, metabolism and toxicity via stress-related phytohormones regulation in Cyphomandra betacea Sendt. (Solanum betaceum Cav.)

High levels of selenium (Se) uptakes negatively affect plant growth. In this study, the possible molecular mechanism for the effects of abscisic acid (ABA) on Se absorption, metabolism and toxicity in Cyphomandra betacea Sendt. (Solanum betaceum Cav.) young plants were investigated. Se+ABA treatment promoted significant Se absorption in C. betacea while impeding plant growth as compared to Se treatment. The expression levels of sulfate/phosphate transporter protein genes indicated that Se+ABA triggered more S/Se absorption and transportation into chloroplast. Furthermore, Se+ABA promoted higher metabolisms of inorganic sulfur (S)/Se and organic S/Se. The organic Se might be in several forms (SeCysth, SeCys and SeMet) in Se+ABA treatment, whereas SeCysth was the major organic form in Se treatment. More reactive oxygen species production was suggested in Se+ABA treatment from a series of genes involved in antioxidant enzymes and molecules, including superoxide dismutase, peroxiredoxin, glutathione sulfur-transferase and glutathione. Se+ABA further improved the expression levels of genes involved in biosynthesis and signaling transduction genes involved in stress-related phytohormones (jasmonic acid and salicylic acid). Combining with the data in ABA treatment, we hypothesized a model that ABA might first affect the biosynthesis and signaling transduction pathways of stress-related phytohormones, and subsequently altered the metabolic processes responding to Se stress.