Abstract：
Blotches in floral organs attract pollinators and promote pollination success. Tree peony (Paeonia suffruticosa Andr.) is an internationally renowned cut flower with extremely high ornamental and economic value. Blotch formation on P. suffruticosa petals is predominantly attributed to anthocyanin accumulation. However, the endogenous regulation of blotch formation in P. suffruticosa remains elusive. Here, we identified the regulatory modules governing anthocyanin-mediated blotch formation in P. suffruticosa petals, which involves the transcription factors PsMYB308, PsMYBPA2, and PsMYB21. PsMYBPA2 activated PsF3H expression to provide sufficient precursor substrate for anthocyanin biosynthesis. PsMYB21 activated both PsF3H and PsFLS expression and promoted flavonol biosynthesis. The significantly high expression of PsMYB21 in non-blotch regions inhibited blotch formation by competing for anthocyanin biosynthesis substrates, while conversely, its low expression in the blotch region promoted blotch formation. PsMYB308 inhibited PsDFR and PsMYBPA2 expression to directly prevent anthocyanin-mediated blotch formation. Notably, a smaller blotch area, decreased anthocyanin content, and inhibition of anthocyanin structural gene expression were observed in PsMYBPA2-silenced petals, while the opposite phenotypes were observed in PsMYB308-silenced and PsMYB21-silenced petals. Additionally, PsMYBPA2 and PsMYB308 interacted with PsbHLH1-3, and their regulatory intensity on target genes was synergistically regulated by the PsMYBPA2-PsbHLH1-3 and PsMYB308-PsbHLH1-3 complexes. PsMYB308 also competitively bound to PsbHLH1-3 with PsMYBPA2 to fine-tune the regulatory network to prevent overaccumulation of anthocyanin in blotch regions. Overall, our study uncovers a complex R2R3-MYB transcriptional regulatory network that governs anthocyanin-mediated blotch formation in P. suffruticosa petals, providing insights into the molecular mechanisms underlying blotch formation in P. suffruticosa.
摘要：
花器官中的斑点吸引传粉者并促进授粉成功。牡丹（PaeoniasuffruticosaAndr。）是国际知名的切花，具有极高的观赏和经济价值。P.suffruticosa花瓣上的斑点形成主要归因于花色苷的积累。然而,苦参斑点形成的内源性调节仍然难以捉摸。这里,我们确定了控制花青素介导的斑点形成的调控模块。其中涉及转录因子PsMYB308，PsMYBPA2和PsMYB21。PsMYBPA2激活PsF3H表达,为花色苷生物合成提供足够的前体底物。PsMYB21激活PsF3H和PsFLS的表达并促进黄酮醇的生物合成。PsMYB21在非斑点区域的显着高表达通过竞争花青素生物合成底物来抑制斑点的形成。而反过来,其在斑点区的低表达促进了斑点的形成。PsMYB308抑制PsDFR和PsMYBPA2表达以直接防止花色苷介导的斑点形成。值得注意的是,一个较小的斑点区域，花青素含量降低，在PsMYBPA2沉默的花瓣中观察到花色苷结构基因表达受到抑制，而在PsMYB308沉默的花瓣和PsMYB21沉默的花瓣中观察到相反的表型。此外,PsMYBPA2和PsMYB308与PsbHLH1-3相互作用，它们对靶基因的调控强度受到PsMYBPA2-PsbHLH1-3和PsMYB308-PsbHLH1-3复合物的协同调控。PsMYB308还与PsMYBPA2竞争性结合到PsbHLH1-3，以微调调节网络，以防止花色苷在斑点区域的过度积累。总的来说,我们的研究揭示了一个复杂的R2R3-MYB转录调控网络，该网络控制着P.suffruticosa花瓣中花青素介导的斑点形成，提供对P.sufruticosa斑点形成的分子机制的见解。
