Genome-Wide Identification of the U-Box E3 Ubiquitin Ligase Gene Family in Cabbage ( var. ) and Its Expression Analysis in Response to Cold Stress and Pathogen Infection.

Plant U-box E3 ubiquitin ligases (PUBs) play an important role in growth, development, and stress responses in many species. However, the characteristics of U-box E3 ubiquitin ligase genes in cabbage ( var. ) are still unclear. Here, we carry out the genome-wide analysis of U-box E3 ubiquitin ligase genes in cabbage and identify 65 var. U-box E3 ubiquitin ligase (BoPUB) genes in the cabbage genome. Phylogenetic analysis indicates that all 65 genes are grouped into six subfamilies, whose members are relatively conserved in the protein domain and exon-intron structure. Chromosomal localization and synteny analyses show that segmental and tandem duplication events contribute to the expansion of the U-box E3 ubiquitin ligase gene family in cabbage. Protein interaction prediction presents that heterodimerization may occur in BoPUB proteins. In silico promoter analysis and spatio-temporal expression profiling of genes reveal their involvement in light response, phytohormone response, and growth and development. Furthermore, we find that genes participate in the biosynthesis of cuticular wax and in response to cold stress and pathogenic attack. Our findings provide a deep insight into the U-box E3 ubiquitin ligase gene family in cabbage and lay a foundation for the further functional analysis of genes in different biological processes.