Systematic Analysis of Cotton RING E3 Ubiquitin Ligase Genes Reveals Their Potential Involvement in Salt Stress Tolerance

The Really Interesting New Gene (RING) E3 ubiquitin ligases represent the largest class of E3 ubiquitin ligases involved in protein degradation and play a pivotal role in plant growth, development, and environmental responses. Despite extensive studies in numerous plant species, the functions of RING E3 ligases in cotton remain largely unknown. In this study, we performed systematic identification, characterization, and expression analysis of RING genes in cotton. A total of 514, 509, and 914 RING genes were identified in Gossypium arboretum, G. raimondii, and G. hirsutum, respectively. Duplication analysis indicates that segmental duplication may be the primary mechanism responsible for the expansion of the cotton RING gene family. Moreover, the Ka/Ks analysis suggests that these duplicated genes have undergone purifying selection throughout the evolutionary history of cotton. Notably, 393 G. hirsutum RING genes exhibited differential expression in response to salt stress. The overexpression of the specific C3H2C3 RING gene, GhZFRG1, in Arabidopsis resulted in enhanced tolerance to salt stress. This study contributes to our understanding of the evolution of cotton RING ligases and paves the way for further functional analysis of the RING E3 ligase genes in cotton.