Transcriptomic and metabolomic analyses reveal that MYB transcription factors regulate anthocyanin synthesis and accumulation in the disc florets of the anemone form of chrysanthemum morifolium

Abstract

• We conducted detailed metabolomic and transcriptomic analyses of ‘Danfen’, a conventional variety, and ‘Fenlian’, an anemone variety. • Our results indicate that CmMYB6 and CmMYB3 in ‘Fenlian'disc florets leading to accumulation of anthocyanin. The expression of CmMYB5 in ‘Danfen’ disc florets inhibits the expression of anthocyanin biosynthesis genes. • Our research have identified candidate genes and established a theoretical basis for the improvement of the colour of disc florets of common chrysanthemum varieties. Chrysanthemum morifolium is a popular flower. The disc florets of most C. morifolium varieties are yellow or colourless, whereas those of the anemone-form are red/pink. To explain this difference, we analysed the metabolomes and transcriptomes of ‘Danfen’ (conventional variety) and ‘Fenlian’ (anemone-form variety). Of the 129,277 assembled unigenes, 59,070 were annotated. A total of 50,325 differentially expressed genes (DEGs) were detected between the ‘Fenlian’ and ‘Danfen’ disc florets (20,782 up-regulated DEGs and 29,543 down-regulated DEGs). Two genes encoding R2R3-MYB transcription factors ( CmMYB5 and CmMYB59 ) were specifically expressed in the ‘Danfen’ disc florets. In contrast, CmMYB6, CmMYB3 , and CHI were specifically expressed in ‘Fenlian’ disc florets. Moreover, four CHS genes, six F3H genes, two F3′H genes, four DFR genes, and one ANS gene were highly expressed in ‘Fenlian’ disc florets. Several anthocyanins were detected only in the ‘Fenlian’ disc florets. Our results indicate that CmMYB6 and CmMYB3 regulate the specific expression of CHI in ‘Fenlian’, leading to high CHS and DFR expression levels and the accumulation of cyanidin chloride and pelargonidin chloride. The expression of CmMYB5 in ‘Danfen’ disc florets inhibits the expression of anthocyanin biosynthesis genes. On the basis of our data, we identified candidate genes that may be useful for enhancing C. morifolium flower coloration.