Genome-Wide Identification and Exogenous Hormone and Stress Response Expression Analysis of the GARP Gene Family in Soybean (Glycine max)

The GARP transcription factor family is integral to the regulation of plant growth, development, hormone signaling pathways, circadian rhythms, and responses to both biotic and abiotic stressors. Despite its recognized importance, a comprehensive characterization of the GARP gene family in Glycine max remains unexplored. In this study, we identified 126 GmGARP genes across the 16 chromosomes of G. max and elucidated their diverse physicochemical properties. Phylogenetic classification grouped the GmGARP genes into eight distinct subfamilies, based on conserved motifs and gene structures, suggesting functional and evolutionary conservation within these clusters. The discovery of 56 segmentally duplicated gene pairs highlights gene duplication as a key driver of family expansion. Promoter analysis revealed various cis-regulatory elements, while expression profiling demonstrated that GmGARP genes possess significant tissue specificity. Furthermore, qRT-PCR analysis indicated that GmGARP genes are highly responsive to exogenous hormones, such as ABA, MeJA, and GA, as well as to abiotic stresses, including cold, salt, and drought conditions. Notably, GmGARP120 and GmGARP98 contain specific cis-elements linked to hormone responses, with their interaction verified through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Additionally, 11,195 potential target genes were predicted, underscoring the regulatory potential of the GmGARP transcription factors. These findings provide significant insights into the GmGARP gene family, laying a strong foundation for future studies on its role in G. max development and adaptive responses to environmental stressors.