De novo assembly and transcriptome analysis of differentially expressed genes relevant to variegation in hawthorn flowers

Flower color variegation has been observed in many plant species. However, pink flowers on the white-blooming hawthorn trees found by our group earlier have never been reported. To better understand the differentially expressed genes (DEGs) in variegated hawthorn flowers, white and pink flowers at different developmental stages (S1 and S2) underwent transcriptome sequencing separately. Approximately 34.28 Gb of high-quality data were obtained and assembled into 100,013 unigenes with an average length of 706.93 bp. These unigenes were further subjected to functional annotation and biochemical pathway analysis, and DEGs of two types of hawthorn flowers at different developmental stages were studied. Based on the enrichment analysis of DEGs, eight anthocyanin-modified enzyme genes or other enzyme genes that indirectly affect anthocyanin synthesis (5AT, 3GGT, and AI, β-Glu, two Aux/IAAs, two PODs), eight structural genes (UFGT, DFR, CHI, two F3Hs, and three PALs), and three transcription factors (one MYB and two bHLHs) were also identified. We randomly selected 15 genes, and the trends in the expression levels of these genes in the organs of white and pink flowers at different developmental stages were verified by quantitative real-time PCR. Mass sequence data obtained by RNA-seq of variegated hawthorn flowers provided basic sequence information and a unique opportunity to uncover the genetic mechanisms underlying flower color variegation.