• Soybean expansin protein GmEXLB1 improve the root development dependent-on auxin signal pathway; • Overexpression of GmEXLB1 enhanced soybean salt tolerance; • GmEXLB1 directly interacts with GmPUB21, an E3 ubiquitin ligase that negatively regulates soybean salt tolerance. • Cell-free assay showed the stability of GmEXLB1 protein is regulated via the 26S proteasome pathway; moreover, GmPUB21 promotes the degradation of GmEXLB1 specifically under salt stress. As a salt-sensitive crop, soybean is significantly threatened by salt stress, which can reduce its yield. Previous study identified E3 ligase GmPUB21 as a negative regulator of salt stress responses that interacts with the expansin-like B1 gene GmEXLB1 . RT-qPCR analysis revealed that GmEXLB1 mRNA levels was rapidly induced by NaCl treatment in both roots and leaves. Overexpression of GmEXLB1 significantly enhanced salt tolerance, and improved root development. DAB staining revealed that less ROS accumulated in GmEXLB1 -overexpressed plants. Physiological assays further demonstrated that GmEXLB1 -overexpressing plants exhibited significantly higher catalase (CAT) and peroxidase (POD) activities, along with reduced malondialdehyde (MDA) content, compared to wild-type controls. Cell-free assay shows that the protein stability regulation of GmEXLB1 depends on the 26S proteasome pathway, and GmPUB21 promotes the degradation of GmEXLB1, especially under salt treatment. Interestingly, IAA effectively enhances the stability of GmEXLB1. These results reveals that GmEXLB1 enhance salt tolerance and improve the root development dependent-on IAA signal pathway in soybean.
Yang et al. (Wed,) studied this question.