Identification of the BBX gene family and SmBBX5 positively regulate anthocyanin accumulation in eggplant (Solanum melongena L.)

BBX transcription factors (TF) play a vital role in the anthocyanin synthesis. Purple eggplant is rich in anthocyanin and has high nutritional value and greatly benefiting human health. Although some eggplant anthocyanin synthesis genes have been reported, the molecular mechanism of eggplant BBX genes participate in anthocyanin synthesis remains unclear. In this present study, 38 SmBBX genes were detected and distributed on 12 chromosomes. The all SmBBX proteins can be divided into 5 subfamilies by phylogenetic analysis. Cis-elements analysis found that SmBBX genes may play important role in regulating light, stress and hormone responsive in eggplant. A total of 13 gene duplication were found in 19 SmBBX genes. In all 4,765 differentially expressed genes (DEGs) were identified in bagged and debagged eggplant peels by transcriptome sequencing. The 11 differentially expressed SmBBX genes were obtained and confirmed by RT-qPCR. KEGG analysis found that all DEGs were significantly enriched in the flavonoids, phenylpropanoids, stilbenes, diarylheptanes and gingerols pathways. Subcellular localization found that SmBBX5 was localized in nucleus. The SmBBX5 gene positively regulated the synthesis of anthocyanin in eggplant peel by transient overexpression and VIGS technology. The results provide new reference for exploring the molecular mechanism of anthocyanin accumulation and genetic improvement of eggplant with high anthocyanin in eggplant.