Identification and Analysis of the CBF Gene Family in Three Species of Acer under Cold Stress.

The C-Repeat Binding Factor ( CBF ) gene family has been identified and characterized in multiple plant species, and it plays a crucial role in responding to low temperatures. Presently, only a few studies on tree species demonstrate the mechanisms and potential functions of CBFs associated with cold resistance, while our study is a novel report on the multi-aspect differences of CBFs among three tree species, compared to previous studies. In this study, genome-wide identification and analysis of the CBF gene family in Acer truncatum , Acer pseudosieboldianum , and Acer yangbiense were performed. The results revealed that 16 CBF genes (five ApseCBFs , four AcyanCBFs , and seven AtruCBFs ) were unevenly distributed across the chromosomes, and most CBF genes were mapped on chromosome 2 (Chr2) and chromosome 11 (Chr11). The analysis of phylogenetic relationships, gene structure, and conserved motif showed that 16 CBF genes could be clustered into three subgroups; they all contained Motif 1 and Motif 5, and most of them only spanned one exon. The cis-acting elements analysis showed that some CBF genes might be involved in hormone and abiotic stress responsiveness. In addition, CBF genes exhibited tissue expression specificity. High expressions of ApseCBF1, ApseCBF3 , AtruCBF1 , AtruCBF4 , AtruCBF6 , AtruCBF7 , and ApseCBF3 , ApseCBF4 , ApseCBF5 were detected on exposure to low temperature for 3 h and 24 h. Low expressions of AtruCBF2 , AtruCBF6 , AtruCBF7 were detected under cold stress for 24 h, and AtruCBF3 and AtruCBF5 were always down-regulated under cold conditions. Taken together, comprehensive analysis will enhance our understanding of the potential functions of the CBF genes on cold resistance, thereby providing a reference for the introduction of Acer species in our country.