Manipulation of brassinosteroid signaling via overexpression of its major receptor SlBRI1 regulates salt tolerance in tomato

Abstract

Salinity is a key abiotic stress that has a negative impact on overall growth and crop yield. SlBRI1, a major receptor of brassinosteroid (BR) signaling, regulates plant growth and development as well as stress resistance. However, the role of SlBRI1 in salt stress adaptation remains unclear. In this study, we investigated the biological function of SlBRI1 in tomato subjected to high salt concentrations. Our results indicated that SlBRI1 was induced by salt stress. Compared with wild-type plants, SlBRI1 overexpressing lines with enhanced BR signaling showed improved tolerance, while the tomato BR-insensitive mutant cu3−abs1, a loss-of-function mutant of SlBRI1, showed increased sensitivity to high salt concentrations. Physiological analyses indicated that SlBRI1-overexpressing lines have enhanced salt tolerance through elevated cell membrane integrity, higher osmo-protectant accumulation, improved photosynthetic capacity, elevated antioxidant activity, enhanced Na+/K+ homeostasis, and upregulation of stress-related genes. Furthermore, tomato SlBRI1-overexpressing lines exhibited a higher germination percentage, plant height, seedling fresh and dry weight, fruit number per plant, single fruit weight, total soluble solids, and fruit yield per plant than wild-type plants subjected to salt stress. Our research provides evidence indicating the positive role of SlBRI1 in the regulation of salt stress tolerance in tomato and provides new insights for breeding high-yielding crops for saline soil.