The receptor-like cytoplasmic kinase BRASSINOSTEROID-SIGNALING KINASE1 (BSK1) interacts with pattern recognition receptor (PRR) FLAGELLIN SENSING2 (FLS2) and positively regulates plant innate immunity in . However, the molecular components involved in BSK1-mediated immune signaling remain largely unknown. To further explore the molecular mechanism underlying BSK1-mediated disease resistance, we screened two cysteine proteases, RESPONSE TO DEHYDRATION 19 (RD19) and RD19-LIKE 2 (RDL2), as BSK1-binding partners. Overexpression of , but not , displayed an autoimmune phenotype, presenting programmed cell death and enhanced resistance to multiple pathogens. Interestingly, RD19-mediated immune activation depends on BSK1, as knockout of in -overexpressing plants rescued their autoimmunity and abolished the increased resistance. Furthermore, we found that BSK1 plays a positive role in maintaining RD19 protein abundance in Arabidopsis. Our results provide new insights into BSK1-mediated immune signaling and reveal a potential mechanism by which BSK1 stabilizes RD19 to promote effective immune output.

中文翻译：

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油菜素类固醇信号激酶1与半胱氨酸蛋白酶相关并且是拟南芥对脱水反应19介导的抗病性所必需的

类受体细胞质激酶 BRASSINOSTEROID-SIGNALING KINASE1 (BSK1) 与模式识别受体 (PRR) FLAGELLIN SENSING2 (FLS2) 相互作用，并积极调节植物先天免疫。然而，参与 BSK1 介导的免疫信号传导的分子成分仍然很大程度上未知。为了进一步探索 BSK1 介导的抗病性的分子机制，我们筛选了两种半胱氨酸蛋白酶，RESPONSE TO DEHYDRATION 19 (RD19) 和 RD19-LIKE 2 (RDL2)，作为 BSK1 结合伴侣。的过度表达，但不是 ，表现出自身免疫表型，呈现程序性细胞死亡和对多种病原体的抵抗力增强。有趣的是，RD19介导的免疫激活依赖于BSK1，因为敲除in-过度表达的植物可以挽救它们的自身免疫并消除增加的抵抗力。此外，我们发现 BSK1 在维持拟南芥中 RD19 蛋白丰度方面发挥着积极作用。我们的结果为 BSK1 介导的免疫信号传导提供了新的见解，并揭示了 BSK1 稳定 RD19 以促进有效免疫输出的潜在机制。