• The evolution of a lipid‐based cuticle on aerial plant surfaces that protects against dehydration is considered a fundamental innovation in the colonization of the land by the green plants. However, key evolutionary steps in the early regulation of cuticle synthesis are still poorly understood, owing to limited studies in early‐diverging land plant lineages.
• Here, we characterize a land plant specific subgroup 9 R2R3 MYB transcription factor MpSBG9, in the early‐diverging land plant model Marchantia polymorpha, that is homologous to MIXTA proteins in vascular plants.
• The MpSBG9 functions as a key regulator of cuticle biosynthesis by preferentially regulating expression of orthologous genes for cutin formation, but not wax biosynthesis genes. The MpSBG9 also promotes the formation of papillate cells on the adaxial surface of M. polymorpha, which is consisitent with its canonical role in vascular plants.
• Our observations imply conserved MYB transcriptional regulation in the control of the cutin biosynthesis pathway as a core genetic network in the common ancestor of all land plants, implicating the land plant‐specific MIXTA MYB lineage in the early origin and evolution of the cuticle.

中文翻译：

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特定于陆地植物的MIXTA-MYB谱系与植物表皮的早期进化和土地定殖有关

• 防止植物脱水的空中植物表面脂基表皮的进化被认为是绿色植物在土地上定殖的一项根本性创新。然而，由于对早期分化的陆地植物谱系的研究有限，因此对角质层合成的早期调控的关键进化步骤仍知之甚少。
• 在这里，我们在早期分化的陆地植物模型Marchantia polymorpha中表征了一个陆地植物特异性亚组9 R2R3 MYB转录因子MpSBG9，它与维管植物中的MIXTA蛋白同源。
• MpSBG9通过优先调节角质形成的直系同源基因而不是蜡质生物合成基因的表达而充当表皮生物合成的关键调节剂。所述MpSBG9还促进乳突细胞的近轴表面上形成M.多形，这是consisitent在维管束植物它的规范的作用。
• 我们的观察结果表明，在角质生物合成途径的控制中，MYB转录调控是所有陆地植物共同祖先的核心遗传网络，这牵涉到陆地植物特有的MIXTA MYB谱系在角质层的早期起源和进化中。