The Transcriptome and Metabolomic Analysis Reveal the Potential Role of CmjMYB308 in Anthocyanin Synthesis in the...

Flower color is a crucial economic trait in horticultural ornamental plants. Clematis L. is celebrated as 'the Queen of Vine Flowers' due to its vibrant and colorful flowers. To delve deeper into the mechanisms behind flower color variation, we conducted a study focusing on two Clematis cultivars: C. 'Henryi' and C. 'Mme Julia Correvon'. The transcriptome and metabolome results revealed that the red coloration of Clematis petals was related to the accumulation of peonidin-3-glucoside and the degradation of cyanidin 3-O-beta-D-sambubioside. Building on the correlation analysis of metabolomic and transcriptomic data, several ABP genes governed by TFs were found to be enriched. Then, we identified 55 R2R3-MYB TFs and discovered that 26 genes were highly expressed in C. 'Mme Julia Correvon'. Moreover, the co-expression network results indicated that CmjMYB308 of C. 'Mme Julia Correvon', a member of Subgroup 4, emerged as a high-frequency gene and may serve as a core TF involved in anthocyanin synthesis. Additionally, RT-qPCR analyses confirmed that CmjMYB308 was highly expressed in petals. Interestingly, MYB308 has two Indel variations in its coding sequence, which caused non-frameshift mutations in its encoded protein. To assess the functional implications of these variations, we performed a yeast autoactivation assay, which demonstrated that both ChrMYB308 of C. 'Henryi' and CmjMYB308 possess strong auto-activation capabilities. Taken together, our findings provide a solid foundation for understanding the role of indel variations in anthocyanin synthesis and offer valuable insights for future molecular-assisted breeding efforts aimed at differentiating flower colors within the Clematis genus.