The members of the fourth subgroup of R2R3-MYB (Sg4 members) are well-known inhibitors of phenylpropanoid and lignin synthesis pathways. The C2 domain is closely related to the transcriptional inhibitory activity of Sg4 members. Phosphorylation modification enhances the transcriptional inhibitory activity of Sg4 members. Here, we identified a phosphorylation site on the C2 domain of CsMYB4a from tea plants (). A mitogen-activated protein kinase (MAPK), named CsMPK3-2, phosphorylated this site on the C2 domain of CsMYB4a. Further experiments revealed that phosphorylation of CsMYB4a weakened its ability to inhibit the gene expression of , , and 4CL in the phenylpropanoid pathway and activated the expression of transcription factor , maintaining the adaxial–abaxial polarity of the leaf. Knocking out in transgenic tobacco partially repaired the leaf wrinkling phenotype caused by . The C1 domain exhibited an activation function when the C2 domain of CsMYB4a was phosphorylated by CsMPK3-2, causing this reversal phenomenon. These results enrich our understanding of the regulatory diversity of Sg4 members.

中文翻译：

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磷酸化修饰逆转茶树（Camellia sinensis）中 CsMYB4a 的转录抑制活性


R2R3-MYB第四亚组的成员（Sg4成员）是众所周知的苯丙素和木质素合成途径的抑制剂。 C2结构域与Sg4成员的转录抑制活性密切相关。磷酸化修饰增强了 Sg4 成员的转录抑制活性。在这里，我们在茶树 CsMYB4a 的 C2 结构域上鉴定了一个磷酸化位点 ()。一种名为 CsMPK3-2 的丝裂原激活蛋白激酶 (MAPK) 磷酸化 CsMYB4a C2 结构域上的该位点。进一步的实验表明，CsMYB4a的磷酸化削弱了其抑制苯丙素途径中的、、和4CL基因表达的能力，并激活了转录因子的表达，维持了叶片的近轴-远轴极性。转基因烟草中的敲除部分修复了由 引起的叶片起皱表型。当 CsMYB4a 的 C2 结构域被 CsMPK3-2 磷酸化时，C1 结构域表现出激活功能，导致这种逆转现象。这些结果丰富了我们对 Sg4 成员监管多样性的理解。