Genome-wide identification of the BBX gene family in kiwifruit and analysis of its expression responses to multiple types of stress.

This study systematically analyzed the BBX gene family in kiwifruit (Actinidia chinensis) to investigate its roles in abiotic stress responses. Bioinformatics analyses were performed, including gene localization, collinearity assessment, gene structure characterization, phylogenetic reconstruction, three-dimensional protein modeling, protein-protein interaction networks, and cis-acting element screening. These approaches elucidated the evolutionary relationships and structural features of the kiwifruit BBX genes. Transcriptome data revealed differential expression patterns under boron deficiency, salt stress, and cadmium stress, visualized through heatmaps. Quantitative real-time PCR validation confirmed that AcBBX4, AcBBX5, AcBBX15, AcBBX17, and AcBBX36 were significantly differentially expressed under all three stress conditions, suggesting their coordinated function in stress adaptation. Protein-protein interaction analysis identified AcBBX17 as a central hub in the regulatory network. Promoter analysis indicated that AcBBX17 contains a high proportion of methyl jasmonate responsive elements, and functional enrichment supported its involvement in the jasmonic acid signaling pathway. Based on these findings, a jasmonic acid-mediated regulatory model centered on AcBBX17 was proposed. In summary, the BBX gene family functions as key transcriptional regulators in plant development and stress response pathways, with this study providing specific insights into its role in kiwifruit abiotic stress tolerance.