Cheng Lijun, Liu Zhiwen, Lu Baiyan, Gao Sihan, Zhao Junwei, Li Chao
School of Life Sciences, East China Normal University, Shanghai 200241, China.
School of Life Sciences, East China Normal University, Shanghai 200241, China; Institute of Eco-Chongming, East China Normal University, Shanghai 202162, China.
Plant Commun. 2025 Jul 30:101468. doi: 10.1016/j.xplc.2025.101468.
Pollen hydration represents the initial and critical step in pollen-stigma interactions and is necessary for successful plant fertilization. The FERONIA (FER) receptor kinase regulates pollen hydration by modulating stigmatic reactive oxygen species (ROS) accumulation through rapid alkalinization factor 23/33 (RALF23/33) and pollen coat protein B-class peptide (PCP-B) signaling. However, the function and regulatory mechanism of FER's receptor kinase activity in pollen hydration remain poorly understood. In this study, we found that the kinase-dead form of FER fails to restore stigmatic ROS accumulation and pollen hydration in the fer-4 mutant. By integrating RNA sequencing database analyses with yeast two-hybrid assays, we identified three type 2C phosphatases (PP2Cs)-protein phosphatase 2C clade H 1 (PP2CH1) and clade-E Growth-Regulating 1 and 2 (EGR1 and EGR2)-that interact with FER at the plasma membrane. These PP2Cs dephosphorylate FER at Ser695 and Thr696 within the activation segment, thereby inhibiting its kinase activity. Mutations at these two residues reduced ROS levels in the stigma and increased pollen hydration rates. Altogether, this study reveals a crucial regulatory mechanism of FER signaling, demonstrating that PP2CH1, EGR1, and EGR2 act as negative regulators of FER kinase activity to modulate stigmatic ROS accumulation and promote pollen hydration.
花粉水合作用是花粉与柱头相互作用的初始关键步骤，也是植物成功受精所必需的。FERONIA（FER）受体激酶通过快速碱化因子23/33（RALF23/33）和花粉壁蛋白B类肽（PCP-B）信号通路调节柱头活性氧（ROS）积累，从而调控花粉水合作用。然而，FER受体激酶活性在花粉水合作用中的功能和调控机制仍知之甚少。在本研究中，我们发现FER的激酶失活形式无法恢复fer-4突变体中柱头ROS的积累和花粉水合作用。通过整合RNA测序数据库分析和酵母双杂交试验，我们鉴定出三种2C型蛋白磷酸酶（PP2C）——蛋白磷酸酶2C进化枝H 1（PP2CH1）以及进化枝E的生长调节因子1和2（EGR1和EGR2）——它们在质膜上与FER相互作用。这些PP2C使FER激活区段内的Ser695和Thr696去磷酸化，从而抑制其激酶活性。这两个位点的突变降低了柱头中的ROS水平，并提高了花粉水合速率。总之，本研究揭示了FER信号传导的关键调控机制，表明PP2CH1、EGR1和EGR2作为FER激酶活性的负调节因子，调节柱头ROS积累并促进花粉水合作用。
