Genome-Wide Identification and Expression Analysis of the Soybean GmHSP100 Gene Family in Response to Heat and Salt Stresses

Background: Heat shock protein 100 (HSP100) is a key molecular chaperone that maintains intracellular proteostasis and enhances plant tolerance. However, the HSP100 gene family in soybean (Glycine max) has not been systematically characterized. Methods: In this study, we performed genome-wide identification and comprehensive analysis of the GmHSP100 gene family and analyzed their phylogeny, genomic distribution, synteny, protein structures, subcellular localization, promoter cis-elements, and expression patterns under heat and salt stresses via bioinformatics approaches and quantitative real-time PCR (qRT-PCR) validation. Results: Thirteen GmHSP100 members were identified, which were classified into CLPB, CLPC and CLPD subfamilies. Segmental and whole-genome duplications primarily drove the expansion of this gene family. All encoded proteins possessed conserved AAA+ ATPase domains, with distinct motifs across subfamilies. Most proteins localized to the cytoplasm, while CLPC and CLPD targeted chloroplasts and GmCLPB4 localized to mitochondria. Promoter analysis identified numerous elements associated with light, hormone and stress responses. Expression profiling showed strong tissue specificity and time-dependent stress-treatment induction. Heat stress triggered rapid and strong upregulation of the GmHSP100s, whereas salt stress salt stress induced their relatively delayed and sustained expression. Conclusions: These findings reveal the evolutionary conservation and diversification of the GmHSP100 gene family in soybean, providing a foundational framework for understanding the functions of GmHSP100 in stress adaptation.