Integrated Metabolome and Transcriptome Analyses Reveal That the Flavonoid Metabolic Pathway Is Associated with Pigment Differential Accumulation in Two Colors of Petaloid Staminodes in Canna glauca

Canna glauca, an ornamental plant widely cultivated in aquatic habitats, is notable for its long florescence and showy flowers. The flower of this species is distinguished by its petaloid staminodes, which comprise the majority of the overall floral display. Flavonoids have been reported to be the predominant pigment groups that determine most flower colors. However, the influence of flavonoid metabolic pathways on the flower color of C. glauca remains to be investigated. In this study, comprehensive floral transcriptomes and metabolite profiles of the wild type (yellow flower) and 'Erebus' cultivar (pink flower) of C. glauca were analyzed. We identified 432 flavonoid metabolites, including 20 anthocyanins. 'Erebus' accumulated higher levels of 18 anthocyanins than the wild type, including 10 cyanidins, 4 pelargonidins, and 4 peonidins. The wild type accumulated higher levels of two malvidins. Through the joint analysis of transcriptomics and metabonomics, we observed a notable association between the expression of three DEGs and eleven anthocyanin levels. Furthermore, we analyzed the expression patterns of key genes that determine flavonoid biosynthesis, such as CHS, CHI, F3 ' H, and DFR. These findings provide enlightenment on the anthocyanin accumulation of Canna glauca, serving as a basis for exploring biochemical and molecular mechanisms underlying flower coloration.