Genome wide comparative analysis of the BAHD superfamily in seven Rosaceae species and expression analysis in pear (Pyrus☓ bretschneideri)

Abstract

Background: The BAHD acyltransferase superfamily exhibits various biological roles in plants, including regulation the fruit quality; catalytic synthesis of terpene, phenolic and esters; improvement of stress resistance. However, the copy number, evolutionary history and potential functions of the BAHD superfamily genes in the genome sequenced Rosaceae species remains unclear. Results: Totally, 755 BAHD genes were obtained from the genomes of seven Rosaceae fruit species (Pyrus bretschneideri, Malus domestica, Prunus avium, Prunus persica, Fragaria vesca, Pyrus communis and Rubus occidentalis). Based on the classification results from model plants, we divided the BAHD family genes into seven subgroups (I-a, I-b, II-a, II-b, III-a, IV, V). Based on intra-species synteny analysis, 61 syntenic gene pairs were detected from the six Rosaceae species. Dispersed gene duplication occurred frequently in all investigated species. Different modes of duplicated gene pairs identified in each investigated species show that the Ka/Ks is less than one, indicating they evolved through purifying selection. Based on the correlation analysis between ester content and expression level of BAHD genes at different development stages, we selected five genes to perform qRT-PCR verification, and the results showed that Pbr020016.1, Pbr019034.1, Pbr014028.1 and Pbr029551.1 are the important candidate genes involved in aroma formation during pear fruit development. Conclusion: We have thoroughly annotated the BAHD superfamily genes and made a comprehensive comparative analysis of their colinearity, phylogenetic relationships and gene duplication patterns in the seven Rosaceae species, and also obtained four candidate genes might be involved in the aroma synthesis in the pear fruit. These presented results provide a theoretical basis for the future studies of the specific biological functions of BAHD superfamily members and the improvement of pear fruit quality. Keywords: BAHD, pear, evolution, Rosaceae, transcriptome, volatile esters