State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
Plant J. 2024 Oct;120(1):45-59. doi: 10.1111/tpj.16968. Epub 2024 Aug 10.
Stomatal movement plays a critical role in plant immunity by limiting the entry of pathogens. OPEN STOMATA 1 (OST1) is a key component that mediates stomatal closure in plants, however, how OST1 functions in response to pathogens is not well understood. RECEPTOR-LIKE KINASE 902 (RLK902) phosphorylates BRASSINOSTEROID-SIGNALING KINASE 1 (BSK1) and positively modulates plant resistance. In this study, by a genome-wide phosphorylation analysis, we found that the phosphorylation of BSK1 and OST1 was missing in the rlk902 mutant compared with the wild-type plants, indicating a potential connection between the RLK902-BSK1 module and OST1-mediated stomatal closure. We showed that RLK902 and BSK1 contribute to stomatal immunity, as the stomatal closure induced by the bacterial pathogen Pto DC3000 was impaired in rlk902 and bsk1-1 mutants. Stomatal immunity mediated by RLK902 was dependent on BSK1 phosphorylation at Ser230, a key phosphorylation site for BSK1 functions. Several phosphorylation sites of OST1 were important for RLK902- and BSK1-mediated stomatal immunity. Interestingly, the phosphorylation of Ser171 and Ser175 in OST1 contributed to the stomatal immunity mediated by RLK902 but not by BSK1, while phosphorylation of OST1 at Ser29 and Thr176 residues was critical for BSK1-mediated stomatal immunity. Taken together, these results indicate that RLK902 and BSK1 contribute to disease resistance via OST1-mediated stomatal closure. This work revealed a new function of BSK1 in activating stomatal immunity, and the role of RLK902-BSK1 and OST1 module in regulating pathogen-induced stomatal movement.
气孔运动通过限制病原体进入来在植物免疫中发挥关键作用。开放气孔 1（OST1）是介导植物气孔关闭的关键组成部分，然而，OST1 如何响应病原体还不太清楚。受体样激酶 902（RLK902）磷酸化油菜素甾醇信号激酶 1（BSK1）并正向调节植物抗性。在这项研究中，通过全基因组磷酸化分析，我们发现与野生型植物相比，rlk902 突变体中 BSK1 和 OST1 的磷酸化缺失，表明 RLK902-BSK1 模块与 OST1 介导的气孔关闭之间存在潜在联系。我们表明 RLK902 和 BSK1 有助于气孔免疫，因为细菌病原体 Pto DC3000 诱导的气孔关闭在 rlk902 和 bsk1-1 突变体中受损。RLK902 介导的气孔免疫依赖于 BSK1 在 Ser230 上的磷酸化，这是 BSK1 功能的关键磷酸化位点。OST1 的几个磷酸化位点对 RLK902 和 BSK1 介导的气孔免疫很重要。有趣的是，OST1 的 Ser171 和 Ser175 磷酸化有助于由 RLK902 介导但不由 BSK1 介导的气孔免疫，而 OST1 的 Ser29 和 Thr176 残基的磷酸化对 BSK1 介导的气孔免疫至关重要。总之，这些结果表明 RLK902 和 BSK1 通过 OST1 介导的气孔关闭来抵抗疾病。这项工作揭示了 BSK1 在激活气孔免疫中的新功能，以及 RLK902-BSK1 和 OST1 模块在调节病原体诱导的气孔运动中的作用。
