Role of abscisic acid in strigolactone-induced salt stress tolerance in arbuscular mycorrhizal Sesbania cannabina seedlings

Background: Strigolactones (SLs) are considered to be a novel class of phytohormone involved in plant defense responses. Currently, their relationships with other plant hormones, such as abscisic acid (ABA), during responses to salinity stress are largely unknown. Results: In this study, the relationship between SL and ABA during the induction of H2O2 - mediated tolerance to salt stress were studied in arbuscular mycorrhizal (AM) Sesbania cannabina seedlings. The SL levels increased after ABA treatments and decreased when ABA biosynthesis was inhibited in AM plants. Additionally, the expression levels of SL-biosynthesis genes in AM plants increased following treatments with exogenous ABA and H2O2. Furthermore, ABA-induced SL production was blocked by a pre-treatment with dimethylthiourea, which scavenges H2O2. In contrast, ABA production was unaffected by dimethylthiourea. Abscisic acid induced only partial and transient increases in the salt tolerance of 115108 (a SL synthesis inhibitor) treated AM plants, whereas SL induced considerable and prolonged increases in salt tolerance after a pre-treatment with tungstate. Conclusions: These results strongly suggest that ABA is regulating the induction of salt tolerance by SL in AM S. cannabina seedlings.