Brassinosteroid-signaling kinase ZmBSK7 enhances salt stress tolerance in maize

Salinity has become a crucial environmental factor that restricts plant growth, development, and productivity. Nevertheless, the mechanisms by which plants react to salt stress remain inadequately comprehended. In this study, we identified maize brassinosteroid-signaling kinase gene ZmBSK7 which is homologous to AtBSK1. Our results showed that ZmBSK7 is induced by salt stress and ZmBSK7 localizes in the plasma membrane. ZmBSK7 overexpression increases salt tolerance, while its knockdown decreases salt tolerance in maize. ZmBSK7 reduces the malondialdehyde (MDA) content and the percentage of electrolyte leakage, and also elevates the activities of antioxidant enzymes. Furthermore, ZmBSK7 promotes K⁺ content accumulation and reduces Na⁺/K⁺ ratio. Further found that ZmBSK7 physically interacts with K⁺ efflux antiporter 2 (ZmKEA2) in vivo and in vitro. Salt stress also increased the expression of ZmKEA2. Thus, ZmBSK7 improves salt tolerance in maize by affecting ZmKEA2 expression to promote K⁺ content accumulation and reduce Na⁺/K⁺ ratio. This study enhances the comprehension of BSK proteins and establishes a theoretical foundation for investigating salt stress tolerance in plants.