Summary Plant homeodomain leucine zipper IV (HD‐Zip IV) transcription factors (TFs) contain an evolutionarily conserved steroidogenic acute regulatory protein (StAR)‐related lipid transfer (START) domain. While the START domain is required for TF activity, its presumed role as a lipid sensor is not clear. Here we used tandem affinity purification from Arabidopsis cell cultures to demonstrate that PROTODERMAL FACTOR2 (PDF2), a representative member that controls epidermal differentiation, recruits lysophosphatidylcholines (LysoPCs) in a START‐dependent manner. Microscale thermophoresis assays confirmed that a missense mutation in a predicted ligand contact site reduces lysophospholipid binding. We additionally found that PDF2 acts as a transcriptional regulator of phospholipid‐ and phosphate (Pi) starvation‐related genes and binds to a palindromic octamer with consensus to a Pi response element. Phospholipid homeostasis and elongation growth were altered in pdf2 mutants according to Pi availability. Cycloheximide chase experiments revealed a role for START in maintaining protein levels, and Pi starvation resulted in enhanced protein destabilization, suggesting a mechanism by which lipid binding controls TF activity. We propose that the START domain serves as a molecular sensor for membrane phospholipid status in the epidermis. Our data provide insights toward understanding how the lipid metabolome integrates Pi availability with gene expression.

中文翻译：

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拟南芥原胚因子2结合溶血磷脂酰胆碱并转录调节磷脂代谢


摘要植物同源域亮氨酸拉链 IV (HD-Zip IV) 转录因子 (TF) 含有进化上保守的类固醇生成急性调节蛋白 (StAR) 相关脂质转移 (START) 结构域。虽然 START 结构域是 TF 活性所必需的，但其作为脂质传感器的假定作用尚不清楚。在这里，我们使用拟南芥细胞培养物中的串联亲和纯化来证明原真皮因子2（PDF2）（控制表皮分化的代表性成员）以START依赖性方式招募溶血磷脂酰胆碱（LysoPCs）。微尺度热泳分析证实，预测的配体接触位点中的错义突变会减少溶血磷脂结合。我们还发现 PDF2 作为磷脂和磷酸盐 (Pi) 饥饿相关基因的转录调节因子，并与回文八聚体结合，并与Pi 响应元素。 pdf2 突变体中的磷脂稳态和伸长生长根据 Pi 的可用性而改变。环己酰亚胺追踪实验揭示了 START 在维持蛋白质水平中的作用，而 Pi 饥饿导致蛋白质不稳定增强，这表明脂质结合控制 TF 活性的机制。我们建议 START 结构域作为膜磷脂状态的分子传感器。表皮。我们的数据为了解脂质代谢组如何将 Pi 可用性与基因表达整合起来提供了见解。