Integrated Metabolome and Transcriptome Analysis Reveals the Effect of Anthocyanins on Flower Color Variation in Michelia odora

The flower color of Michelia odora, an important landscape tree plant, shows significant ornamental value, but its regulatory mechanisms remain to be further explored. The present work integrated metabolomic with transcriptomic analyses for elucidating the anthocyanin biosynthesis mechanisms in light pink and deep pink M. odora flowers. Our metabolomic analysis identified 13 differentially expressed anthocyanins, 11 of which, especially cyanidins, were significantly accumulated within deep pink petals versus light pink ones. As revealed by our transcriptomic analysis, 33 differential genes were related to flavonoid and anthocyanin biosynthesis. Further, transcription factor genes, encompassing three MoMYB alongside two MobHLH genes, were likely the hub genes that modulated anthocyanin biosynthesis. Quantitative real-time PCR validation indicated that certain genes, like MoPAL, MoC4H, Mo4CL, MoCHS, MoCHI, MoUGT75C1, MoMYB3, MobHLH1, and MobHLH3, displayed concurrent expression with anthocyanin accumulation within deep pink petals. Collectively, these results indicate the role of anthocyanin accumulation in deep pink color, and the effect of upregulated genes on increasing anthocyanin levels. Our results shed novel light on color change mechanisms underlying M. odora, and provide a theoretical basis for flower breeding.