Genome-wide identification and analysis of RING finger gene family and the self-compatibility-associated SBP1 gene in goji berry (Lycium barbarum)

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RING finger proteins are a large family of E3 ubiquitin ligases that are crucial for modulating plant growth, development, and biotic and abiotic stress responses. The RING-HC-type SBP1 protein serves as a core component of the SCFSLF/SFB ubiquitin ligase complex and modulates gametophytic self-incompatibility (GSI) in plants. As a typical GSI species, Lycium barbarum remains poorly characterized regarding its RING finger gene family and SBP1 homologous genes. Here, we systematically identified 213 RING finger genes at the genome-wide level in L. barbarum . Based on phylogenetic relationships, gene structures, conserved motifs, and domain features, these genes were categorized into seven subfamilies covering RING-H2, RING-HC, and RING-v subtypes. Chromosomal localization analysis revealed that all RING finger genes are distributed on 12 chromosomes, including 10 tandem duplication pairs and 50 segmental duplication pairs. An SBP1 homologous gene that exhibits high sequence similarity with SBP1 proteins from other Solanaceae species was screened from the L. barbarum RING finger family. This homolog is highly and specifically expressed in pollen and encodes a nuclear-localized protein. Yeast two-hybrid assays verified its physical interaction with multiple male GSI determinant proteins in L. barbarum , namely S 2 -LbSLF7 , S 2 -LbSLF9 , S 2 -LbSLF11 , S 2 -LbSLF12 , and S 2 -LbSLF13 . This study comprehensively characterizes the RING finger gene family in L. barbarum and identifies a GSI-associated SBP1 homolog that potentially regulates pollen development and self-incompatibility. Our results provide a vital foundation for uncovering the molecular mechanism of wolfberry GSI and offer valuable genetic resources for the molecular breeding of self-compatible L. barbarum varieties.