Genome-Wide Identification and Characterization of C3H-ZFP Genes and Their Expression under Salt and Cadmium Stress Conditions in Soybean

Zinc finger proteins (ZFPs) are a diverse group of plant transcription factors essential for regulating development, signaling, and stress responses. In this study, we performed a genome-wide identification and integrative analysis of 140 C3H-type zinc finger transcription factor genes in the soybean genome, exhibiting an uneven distribution across all 20 chromosomes. These C3H-ZFPs contained one (37), two (58), three (19), four (7), five (17), or six (2) C3H domains and were classified into 14 subsets based on their domain architecture. All C3H genes encoding proteins harbored the conserved C3H-ZFP domain and displayed various physicochemical characteristics. Phylogenetic analysis grouped them into 10 clades, closely related to other species like Arabidopsis, rice and alfalfa. Promoter analysis revealed cis-elements associated with stress response (~39.1%), light response (~37.3%), phytohormones (~18.5%), and development (~4.97%). Duplication analysis revealed 78 pairs of segmental and eight tandem duplication events, with purifying selection indicated by Ka/Ks (nonsynonymous/synonymous) ratios, indicating that these C3H-ZFP duplicates were largely maintained under purifying selection. A total of 388 miRNAs from 196 gene families were predicted to target 140 C3H-ZFP genes, with most enriched miRNAs targeting C3H-ZFP genes, including the miR156, miR395, and miR396 families. Transcription factor binding sites for MYB, AP2, MIKC_MADS, BBR-BPC, ERF, C2H2, and Dof were found upstream of most C3H-ZFP genes. RNA-Seq and qRT-PCR analyses showed tissue-specific expression and stress-responsive expression patterns, with several C3H-ZFP genes, especially GmC3H1, GmC3H63, GmC3H124, and GmC3H127, being significantly upregulated under abiotic stress conditions. Together, these results provide a comprehensive overview of soybean C3H-ZFP genes and identify promising candidates for future functional studies on development and abiotic stress adaptation.