Identification of RhoGAP Gene Family in Soybean (Glycine max L.) and its Role in the Response to Rhizobium Infection

Rho GTPase-activating proteins (RhoGAPs) are characterized by a conserved RhoGAP domain and function as negative regulators of Rho GTPases, playing important roles in plant growth, development, and responses to environmental stimuli. In this study, 19 GmRhoGAP genes were identified in the soybean genome and found to be unevenly distributed across 11 chromosomes. Comprehensive analyses were performed, including gene structure, conserved motifs, protein domains, gene duplication, synteny, cis-acting elements, tissue-specific expression, and quantitative real-time PCR under rhizobial infection. Structural analysis revealed substantial diversity in intron-exon organization but high conservation of motif composition, with all members containing the conserved RhoGAP domain. A total of 20 segmentally duplicated gene pairs were identified, indicating expansion of the GmRhoGAP family in soybean. Inter-species synteny analysis showed closer evolutionary relationships with Arabidopsis than with rice, and Ka/Ks analysis suggested strong purifying selection during evolution. Promoter analysis indicated potential involvement in development, phytohormone signaling, stress responses, and light responsiveness. Expression profiling demonstrated distinct tissue-specific patterns. qRT-PCR further showed that GmRhoGAP genes respond differentially to rhizobial infection, with 10 generally upregulated genes and 4 downregulated genes. These analyses provide a framework for understanding this gene family and identify candidate genes for future research.