MYB transcription factors regulate diverse aspects of plant development and secondary metabolism, often by partnering in transcriptional regulatory complexes. Here, we harness genomic resources to identify novel MYBs, thereby producing an updated eudicot MYB phylogeny with revised relationships among subgroups as well as new information on sequence variation in the disordered C-terminus of anthocyanin-activating MYBs. BLAST® and hidden Markov model scans of gene annotations identified a total of 714 MYB transcription factors across the genomes of four crops that span the eudicots: apple, grape, kiwifruit and tomato. Codon model-based phylogenetic inference identified novel members of previously defined subgroups, and the function of specific anthocyanin-activating subgroup 6 members was assayed transiently in tobacco leaves. Sequence conservation within subgroup 6 highlighted one previously described and two novel short linear motifs in the disordered C-terminal region. The novel motifs have a mix of hydrophobic and acidic residues and are predicted to be relatively ordered compared with flanking protein sequences. Comparison of motifs with the Eukaryotic Linear Motif database suggests roles in protein–protein interaction. Engineering of motifs and their flanking regions from strong anthocyanin activators into weak activators, and vice versa, affected function. We conclude that, although the MYB C-terminal sequence diverges greatly even within MYB clades, variation within the C-terminus at and near relatively ordered regions offers opportunities for exploring MYB function and developing superior alleles for plant breeding.

中文翻译：

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基因组分析揭示了花青素激活 MYB 转录因子 C 端的功能变异

MYB 转录因子调节植物发育和次生代谢的不同方面，通常通过与转录调节复合物合作。在这里，我们利用基因组资源来识别新的 MYB，从而产生更新的真双子叶植物 MYB 系统发育，其中亚群之间的关系经过修改，以及花青素激活 MYB 的无序 C 端序列变异的新信息。基因注释的 BLAST® 和隐藏马尔可夫模型扫描在跨越真双子叶植物的四种作物的基因组中确定了总共 714 个 MYB 转录因子：苹果、葡萄、猕猴桃和番茄。基于密码子模型的系统发育推断确定了先前定义的亚组的新成员，并且在烟叶中瞬时测定了特定花青素激活亚组 6 成员的功能。亚组 6 内的序列保守性突出了无序 C 末端区域中的一个先前描述的和两个新的短线性基序。新的基序混合了疏水性和酸性残基，预计与侧翼蛋白质序列相比是相对有序的。基序与真核线性基序数据库的比较表明在蛋白质-蛋白质相互作用中的作用。将基序及其侧翼区域从强花青素激活剂转化为弱激活剂（反之亦然）影响功能。我们得出的结论是，尽管 MYB C 末端序列即使在 MYB 进化枝内也存在很大差异，但在相对有序区域及其附近的 C 末端内的变异为探索 MYB 功能和开发植物育种的优良等位基因提供了机会。