Comparative transcriptome analysis between ornamental apple species provides insights into mechanism of double flowering

Abstract

Double-flower ornamental crabapples display eye-catching morphologies in comparison to single flower, but the genetic basis of double-flower development is not yet well known in apples. In order to comprehensively understand the differential expression of genes (DEGs) between single and double flower, the transcriptome of double flower crabapples Malus Kelsey, Malus micromalus, Malus Royalty, and a single flower cultivar Malus Dolgo were compared by RNA-sequencing. The results showed that there were 1854 genes in overlapped DEGs among all sample comparisons in apple single and double flower varieties. A large number of development and hormone related DEGs were also recognized on the basis of GO and KEGG annotations, and most of the genes were found to be down-regulated in double flowers. Particularly, an AGL24-MADS-box gene (MD08G1196900) and an auxin responsive gene (MD13G1137000) were putatively key candidate genes in the development of double flower by weighted gene co-expression network analysis (WGCNA). The study provides insights into the complex molecular mechanism underlying the development of the double flower in apple.