Transcriptome data-based screening of potential host of genetic transformation for a blue-hued Bougainvillea transgene

Bougainvillea is a popular ornamental plant. Although Bougainvillea is abundant in germplasm resources, cultivars and flower colors, there is no rare blue colour varieties, due to the absence of delphinidin-based anthocyanins. This study analyzed the Bougainvillea leaf and bract transcriptome to select hosts of genetic transformation that would be suitable for the accumulation of delphinidin. A total of 36 gigabyte (GB) of raw data was obtained by transcriptome sequencing, with 4,058 significantly differentially expressed genes, including 1,854 upregulated and 2,204 downregulated genes. Annotation of these genes was performed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases. Through annotation, two CHS genes, one F3H gene, one DFR gene, and one F3'H gene involved in the delphinidin biosynthesis pathway were identified. The expression levels of these genes and total flavonoid content in the bracts of six Bougainvillea varieties were examined through quantitative real-time PCR and spectrophotometry, respectively. Through the comprehensive evaluation based on membership function method, the suitable host order for a blue-hued Bougainvillea transgene is Singapore White>Elizabeth Angus>Ratana Yellow>China Beauty>Orange King>Brilliant Variegata. Thus, Singapore White variety was the most appropriate transgene host for blue-hued Bougainvillea. The results of this study provide a reference for the directed breeding of blue-hued Bougainvillea.