Transcriptome Profiling and Gene Network Analysis Revealed Regulatory Mechanisms of Bract Development in Bougainvillea glabra

Background: Bracts are important in ornamental plants and their developmental regulation is complex, but relatively little research has been done on them. In this study, physiological, biochemical and morphological changes in Bougainvillea glabraleaves, leaf buds and bracts during seven developmental periods were systematically investigated in B. glabra bracts. Meanwhile, transcriptome data of B. glabra bracts were obtained using PacBio and Illumina sequencing technologies, and key genes regulating their development were screened. Results: Scanning electron microscopy revealed that the bracts develop with a process of regression of hairs, changing colour from green to white; Transcriptome sequencing yielded 79,130,973 bp of transcript sequences, totalling 45,788 transcripts; Differential gene analysis revealed 50 expression patterns across seven developmental periods, with significant variability in transcription factors such as BgAP1, BgFULL, BgCMB1, BgSPL16, BgEIL1, and BgBH305 KEGG and GO analyses of growth and development concerning chlorophyll metabolism and hormone-conducting metabolic pathways; Key genes for chlorophyll metabolism include PORA, SGR, PPH, PAO and RCCR; The growth hormone and abscisic acid signalling pathways involve 44 and 23 homologous genes, and co-expression network analyses revealed that the screened genes BgAPRR5 and BgEXLA1 are involved in the regulation of bract development. Conclusions: These findings promote the understanding of the molecular mechanism of plant bract development, as well as provide important guidance for the molecular regulation and genetic improvement of the growth and development of ornamental plants, mainly ornamental bracts.