Long-read sequencing ofChrysanthemum morifoliumtranscriptome reveals flavonoid biosynthesis and regulation

The inflorescence ofChrysanthemum morifoliumcv. 'Hangju' has been widely used in China due to its antioxidant and anti-inflammatory properties. The biosynthesis and regulation of flavonoids, a group of bioactive components, inC.morifoliumare poorly understood. Transcriptome sequencing is an effective method for obtaining transcript information. Therefore, single-molecule real-time (SMRT) sequencing was performed to obtain the full-length genes involved in flavonoid biosynthesis and regulation inC.morifolium. High-quality RNA was extracted from the inflorescence ofC.morifoliumat different flowering stages and used to construct two libraries (0-5 kb and 4.5-10 kb) for sequencing. Finally, 125,532 non-redundant isoforms with a mean length of 2009 bp were obtained. Of these, 2,083 transcripts were annotated to pathways related to flavonoid biosynthesis, and 56 isoforms were annotated asCHS,CHI,F3H,F3'H,FNS II,FLS,DFRandANSgenes. Based on gene expression levels at different stages, we predicted the major genes involved in flavonoid biosynthesis. By phylogenetic analysis, we found two candidate MYB transcription factors (CmMYBF1 and CmMYBF2) activating flavonol biosynthesis. Based on the full-length transcriptomic data and further quantitative analysis, the major genes involved in flavonoid biosynthesis and regulation inC.morifoliumwere predicted in our study. The results provide a valuable theoretical basis for the introduction and cultivation ofC. morifoliumcv. 'Hangju'.