Laboratory of Biotechnology and Plant Improvement, Center of Biotechnology of Sfax, BP "1177", University of Sfax, Sfax 3018, Tunisia.
Plant Physiology and Functional Genomics Research Unit, Institute of Biotechnology of Sfax, BP "1175", University of Sfax, Sfax 3038, Tunisia.
Int J Mol Sci. 2021 Sep 27;22(19):10424. doi: 10.3390/ijms221910424.
Brassinosteroids (BRs) play key roles in diverse plant growth processes through a complex signaling pathway. Components orchestrating the BR signaling pathway include receptors such as kinases, transcription factors, protein kinases and phosphatases. The proper functioning of the receptor kinase BRI1 and the transcription factors BES1/BZR1 depends on their dephosphorylation by type 2A protein phosphatases (PP2A). In this work, we report that an additional phosphatase family, type one protein phosphatases (PP1), contributes to the regulation of the BR signaling pathway. Co-immunoprecipitation and BiFC experiments performed in Arabidopsis plants overexpressing durum wheat showed that interacts with dephosphorylated BES1, but not with the BRI1 receptor. Higher levels of dephosphorylated, active BES1 were observed in these transgenic lines upon BR treatment, indicating that modifies the BR signaling pathway by activating BES1. Moreover, ectopic expression of durum wheat lead to an enhanced growth of primary roots in comparison to wild-type plants in presence of BR. This phenotype corroborates with a down-regulation of the BR-regulated genes CPD and DWF4. These data suggest a role of PP1 in fine-tuning BR-driven responses, most likely via the control of the phosphorylation status of BES1.
油菜素内酯（BRs）通过复杂的信号通路在多种植物生长过程中发挥关键作用。协调 BR 信号通路的组成部分包括受体激酶，如激酶、转录因子、蛋白激酶和磷酸酶。受体激酶 BRI1 和转录因子 BES1/BZR1 的正常功能依赖于其被 2A 型蛋白磷酸酶（PP2A）去磷酸化。在这项工作中，我们报告说，另一个磷酸酶家族，即 1 型蛋白磷酸酶（PP1），有助于调节 BR 信号通路。在过表达硬粒小麦的拟南芥植物中进行的共免疫沉淀和 BiFC 实验表明，与受体 BRI1 不同， 与去磷酸化的 BES1 相互作用。在这些转基因系中，用 BR 处理后观察到更高水平的去磷酸化、活性 BES1，表明 通过激活 BES1 来修饰 BR 信号通路。此外，与野生型植物相比，硬粒小麦 的异位表达导致在存在 BR 的情况下主根的生长增强。这种表型与 BR 调控基因 CPD 和 DWF4 的下调相一致。这些数据表明 PP1 在微调 BR 驱动的反应中起作用，可能是通过控制 BES1 的磷酸化状态。
