Directional intercellular transport of the phytohormone auxin mediated by PIN-FORMED (PIN) efflux carriers has essential roles in both coordinating patterning processes and integrating multiple external cues by rapidly redirecting auxin fluxes. PIN activity is therefore regulated by multiple internal and external cues, for which the underlying molecular mechanisms are not fully elucidated. Here, we demonstrate that 3'-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1 (PDK1), which is conserved in plants and mammals, functions as a molecular hub that perceives upstream lipid signalling and modulates downstream substrate activity through phosphorylation. Using genetic analysis, we show that the loss-of-function Arabidopsis pdk1.1 pdk1.2 mutant exhibits a plethora of abnormalities in organogenesis and growth due to defective polar auxin transport. Further cellular and biochemical analyses reveal that PDK1 phosphorylates D6 protein kinase, a well-known upstream activator of PIN proteins. We uncover a lipid-dependent phosphorylation cascade that connects membrane-composition-based cellular signalling with plant growth and patterning by regulating morphogenetic auxin fluxes.

中文翻译：

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脂质密码依赖性磷酸开关 PDK1-D6PK 在拟南芥中激活 PIN 介导的生长素外流。

由 PIN 形成 (PIN) 外排载体介导的植物激素生长素的定向细胞间转运在协调图案化过程和通过快速重定向生长素通量整合多个外部线索方面具有重要作用。因此，PIN 活性受多种内部和外部线索的调节，其潜在的分子机制尚未完全阐明。在这里，我们证明了在植物和哺乳动物中保守的 3'-磷酸肌醇依赖蛋白激酶 1 (PDK1) 可作为感知上游脂质信号传导并通过磷酸化调节下游底物活性的分子中枢。使用遗传分析，我们发现功能丧失的拟南芥 pdk1.1 pdk1.2 突变体由于生长素极性运输缺陷而表现出过多的器官发生和生长异常。进一步的细胞和生化分析表明，PDK1 磷酸化 D6 蛋白激酶，这是一种众所周知的 PIN 蛋白上游激活剂。我们发现了一种脂质依赖性磷酸化级联反应，该级联反应通过调节形态发生生长素通量将基于膜成分的细胞信号传导与植物生长和模式化联系起来。