Anthocyanin biosynthesis is mainly controlled by MYB-bHLH-WD40 (MBW) complexes that modulate the expression of anthocyanin biosynthetic genes. The MYB regulators involved in anthocyanin biosynthesis arose early during plant evolution, and thus might function divergently in different evolutionary lineages. Although the anthocyanin-promoting R2R3-MYB regulators in eudicots have been comprehensively explored, little consensus has been reached about functional discrepancies versus conservation among MYB regulators from different plant lineages. Here we integrated transcriptome analysis, gene expression profiles, gain-of-function experiments and transient protoplast transfection assays to functionally characterize the monocot Freesia hybrida anthocyanin MYB regulator gene FhPAP1 which showed correlations with late anthocyanin biosynthetic genes. FhPAP1 could activate anthocyanin biosynthetic genes as well as TT8-clade genes FhTT8L, AtTT8 and NtAN1 when overexpressed in Freesia, Arabidopsis and tobacco, respectively. Consistently, FhPAP1 could interact with FhTT8L and FhTTG1 to form the conserved MBW complex and shared similar target genes with its orthologs from Arabidopsis. Most prominently, FhPAP1 displayed higher transactivation capacity than its homologs in Arabidopsis and tobacco, which was instantiated in its powerful regulation on anthocyanin biosynthetic genes. Moreover, we found that FhPAP1 might be the selected gene during the domestication and rapid evolution of the wild Freesia species to generate intensive flower pigmentation. These results showed that while the MBW complex was highly evolutionarily conserved between tested monocot and core eudicot plants, participating MYB regulators showed functional differences in transactivation capacity according to their activation domain and played important roles in the flower coloration domestication and evolution of angiosperms.

中文翻译：

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小苍兰的R2R3-MYB调节剂FhPAP1在花色苷生物合成中的保守作用和特殊作用。

花青素的生物合成主要受MYB-bHLH-WD40（MBW）复合物控制，该复合物调节花青素的生物合成基因的表达。花青素生物合成中涉及的MYB调节剂是在植物进化早期出现的，因此可能在不同的进化谱系中发挥不同的作用。尽管已经全面研究了双子叶植物中促进花青素的R2R3-MYB调节剂，但关于不同植物谱系的MYB调节剂之间的功能差异与保守性方面的共识还很少。在这里，我们整合了转录组分析，基因表达谱，功能获得性实验和瞬时原生质体转染测定，以功能表征单子叶植物小苍兰杂种花青素MYB调节基因FhPAP1，该基因与后期花青素生物合成基因相关。当分别在小苍兰，拟南芥属和烟草中过表达时，FhPAP1可以激活花色苷生物合成基因以及TT8覆盖基因FhTT8L，AtTT8和NtAN1。一致地，FhPAP1可以与FhTT8L和FhTTG1相互作用形成保守的MBW复合体，并与拟南芥的直系同源基因共享相似的靶基因。最突出的是，FhPAP1在拟南芥和烟草中显示出比其同源物更高的反式激活能力，这在其对花色苷生物合成基因的强力调控中得以体现。此外，我们发现FhPAP1可能是野生小苍兰的驯化和快速进化期间产生密集的花色素沉着的选定基因。这些结果表明，虽然MBW复合物在测试的单子叶植物和核心双子叶植物之间高度进化保守，