Evolution and diversification of adenine phosphoribosyltransferase (APT) gene family revealed their roles on flowering time in Brassica napus L.

Adenine phosphoribosyltransferase (APT) plays crucial roles in regulating plant growth and development. However, the evolution history of the APT gene family in plants and the features in rapeseed (Brassica napus L.) are largely unknown. Here, we identified 118 APT genes in 17 species from unicellular green alga to multicellular plants. Phylogenetic analysis indicated that the APT genes group into four clades, with divergence occurring between monocots and eudicots. We further systematically analyzed the gene characteristics, promoter cis-elements, and gene expression patterns of APT genes in 17 species. All the APT family members contained hormone response and environmental response elements. Candidate gene association study and trans-regulatory factors analysis revealed that BnaAPTs are associated with flowering time. Yeast-one hybrid assay suggested that BnaC09.APT5 could be regulated by the flowering time regulatory BnaA03.SOC1 via CArG-like motif. Overexpressing BnaC09.APT5 in rapeseed and AtAPT5 (the ortholog of BnaC09.APT5) in Arabidopsis exhibited delayed flowering time, whereas the T-DNA mutant of AtAPT5 (apt5) showed early flowering time. Gene expression of SOC1 was significantly decreased in the corresponding APT5 overexpression lines, and significantly increased in the apt5. These results indicate that APT5 is involved in flowering time regulation. The current study lays the foundation for further investigation the roles and functional mechanisms of BnaAPT genes on flowering time in rapeseed.