Background
The BAHD acyltransferase superfamily exhibits various biological roles in plants, including regulating fruit quality, catalytic synthesizing of terpene, phenolics and esters, and improving stress resistance. However, the copy numbers, expression characteristics and associations with fruit aroma formation of the BAHD genes remain unclear.
Conclusion
We have thoroughly identified the BAHD superfamily genes and performed a comprehensive comparative analysis of their phylogenetic relationships, expansion patterns, and expression characteristics in seven Rosaceae species, and we also obtained four candidate genes involved in aroma synthesis in pear fruit. These results provide a theoretical basis for future studies of the specific biological functions of BAHD superfamily members and the improvement of pear fruit quality.
Results
In total, 717 BAHD genes were obtained from the genomes of seven Rosaceae, (Pyrus bretschneideri, Malus domestica, Prunus avium, Prunus persica, Fragaria vesca, Pyrus communis and Rubus occidentalis). Based on the detailed phylogenetic analysis and classifications in model plants, we divided the BAHD family genes into seven groups, I-a, I-b, II-a, II-b, III-a, IV and V. An inter-species synteny analysis revealed the ancient origin of BAHD superfamily with 78 syntenic gene pairs were detected among the seven Rosaceae species. Different types of gene duplication events jointly drive the expansion of BAHD superfamily, and purifying selection dominates the evolution of BAHD genes supported by the small Ka/Ks ratios. Based on the correlation analysis between the ester content and expression levels of BAHD genes at different developmental stages, four candidate genes were selected for verification as assessed by qRT-PCR. The result implied that Pbr020016.1, Pbr019034.1, Pbr014028.1 and Pbr029551.1 are important candidate genes involved in aroma formation during pear fruit development.