BAHD acyltransferase OsSLG mediates rice cadmium tolerance by integrating the brassinosteroid and salicylic acid pathway

Abstract

Cadmium (Cd) is a highly toxic element that significantly threatens plant growth and human health. Brassinosteroids (BRs) and salicylic acid (SA) are crucial phytohormones involved in plant growth and defense. While the mechanisms by which BRs and SA individually regulate various plant biological processes have been extensively studied, their interaction with Cd in rice (Oryza sativa L.) remains poorly understood. In this study, we demonstrated that SLENDER GRAIN (OsSLG), a BR biosynthesis-related gene, plays a critical role in regulating in rice. Overexpression of OsSLG enhanced Cd tolerance, whereas OsSLG RNA interference (RNAi) lines (OsSLG-Ri) exhibited hypersensitivity to Cd stress. Exogenous BR treatment improved the Cd tolerance of the wild type and rescued the Cd-sensitive phenotype of OsSLG-Ri. Furthermore, OsSLG overexpression significantly reduced reactive oxygen species (ROS) and Cd accumulation, this reduction was attributed to the downregulation of genes involved in Cd absorption and transport, as well as the upregulation of genes associated with Cd detoxification and ROS scavenging. In addition, OsSLG enhanced the photosynthetic capacity and mineral element content in rice plants, improving their ability to cope with Cd stress. Gene expression analysis showed that OsSLG promoted the expression of the SA pathway genes, and phenotypic analysis confirmed that SA positively regulates Cd tolerance in rice. Notably, BR-induced Cd tolerance was diminished in SA biosynthesis-deficient rice plants overexpressing SA hydroxylase genes OsS5H1 and OsS5H2, suggesting that the SA pathway is necessary for BR-mediated Cd tolerance. In conclusion, our findings highlight OsSLG as a key player in elucidating the interplay between BR and SA under Cd stress.