Plants can perceive a slight upsurge in ambient temperature and respond by undergoing morphological changes, such as elongated hypocotyls and early flowering. The dynamic functioning of PHYTOCHROME INTERACTING FACTOR4 (PIF4) in thermomorphogenesis is well established, although the complete regulatory pathway involved in thermosensing remains elusive. We establish that an increase in temperature from 22 to 28 °C induces upregulation and activation of MITOGEN-ACTIVATED PROTEIN KINASE 4 (MPK4) in Arabidopsis (Arabidopsis thaliana), subsequently leading to the phosphorylation of PIF4. Phosphorylated PIF4 represses the expression of ACTIN-RELATED PROTEIN 6 (ARP6), which is required for mediating the deposition of histone variant H2A.Z at its target loci. Furthermore, we demonstrate that variations in ARP6 expression in PIF4 phosphor-null and phosphor-mimetic seedlings affect hypocotyl growth at 22 and 28 °C by modulating the regulation of ARP6-mediated H2A.Z deposition at the loci of genes involved in elongating hypocotyl cells. Interestingly, the expression of MPK4 is also controlled by H2A.Z deposition in a temperature-dependent manner. Taken together, these findings highlight the regulatory mechanism of thermosensing by which MPK4-mediated phosphorylation of PIF4 affects ARP6-mediated H2A.Z deposition at the genes involved in hypocotyl cell elongation.

中文翻译：

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MPK4 介导的 PHYTOCHROME INTERACTING 磷酸化FACTOR4通过调节组蛋白变体 H2A 来控制热感应。Z 沉积


植物可以感知到环境温度的轻微上升，并通过发生形态变化来做出反应，例如细长的下胚轴和早开花。PHYTOCHROME INTERACTING FACTOR4 （PIF4） 在热形态发生中的动态功能已得到充分证实，尽管涉及热传感的完整调节途径仍然难以捉摸。我们确定温度从 22 °C 升高到 28 °C 会诱导拟南芥（拟南芥）中丝裂原活化蛋白激酶 4 （MPK4） 的上调和激活，随后导致 PIF4 的磷酸化。磷酸化 PIF4 抑制肌动蛋白相关蛋白 6 （ARP6） 的表达，这是介导组蛋白变体 H2A 沉积所必需的。Z 在其目标位点。此外，我们证明 PIF4 磷零和磷模拟幼苗中 ARP6 表达的变化通过调节 ARP6 介导的 H 2 A 的调节来影响 22 °C 和 28 °C 下的下胚轴生长。Z 沉积在参与伸长下胚轴细胞的基因位点。有趣的是，MPK4 的表达也受 H2A 控制。Z 沉积。综上所述，这些发现突出了热感应的调节机制，MPK4 介导的 PIF4 磷酸化影响 ARP6 介导的 H2A。Z 沉积在参与下胚轴细胞伸长的基因上。