S-nitrosylation of a receptor-like cytoplasmic kinase regulates plant immunity Beimi Cui, Qiaona Pan, Wenqiang Cui, Yiqin Wang, Verity I. P. Loake, Shuguang Yuan, Fengquan Liu, Gary J. Loake Plant immunity is triggered by the recognition of pathogen/microbial-associated molecular patterns (P/MAMPs) by plant cell surface receptors, leading to a sustained burst of reactive oxygen species (ROS). This study shows that P/MAMP recognition leads to a rapid nitrosative burst, initiating the accumulation of nitric oxide (NO), which subsequently leads to S-nitrosylation of the receptor-like cytoplasmic kinase (RLCK), botrytis-induced kinase 1 (BIK1), at Cys80. This redox-based, posttranslational modification promotes the phosphorylation of BIK1, resulting in BIK1 activation and stabilization. BIK1 S-nitrosylation also increases its physical interaction with RBOHD, the source of the apoplastic oxidative burst, promoting ROS formation. These findings identify mechanistic links between rapid NO accumulation and the expression of PTI, providing insights into plant immunity. The study shows that NO is required for flg22-induced ROS production in Arabidopsis. NO is involved in the regulation of BIK1 stability and activity. BIK1 is S-nitrosylated during PTI, and this S-nitrosylation is critical for BIK1 phosphorylation and activation. The S-nitrosylation of BIK1 at Cys80 is required for BIK1 phosphorylation and activation during PTI. The study also shows that S-nitrosylation of BIK1 at Cys80 is required for the oxidative burst and contributes to resistance against Pst DC3000 hrcC⁻. The study provides a molecular framework for the function of (S)NO during PTI. Following P/MAMP recognition, total cellular (S)NO, governed by AtGSNOR1, increases rapidly, leading to the S-nitrosylation of BIK1 at Cys80, promoting the phosphorylation of BIK1, thereby enhancing both the stability of BIK1 and its interaction with RBOHD. This may help drive the oxidative burst leading to pathogen resistance. However, as (S)NO concentrations increase during the later stages of PTI, AtRBOHD may become S-nitrosylated at Cys890, in a similar fashion to that which occurs during ETI, decreasing ROS synthesis. Analogously, our data show that high SNO levels decrease other PTI responses, including callose deposition and PTI-related gene expression. This complex NO-related molecular dialogue may therefore serve to both promote and subsequently curb PTI. The study also shows that S-nitrosS-nitrosylation of a receptor-like cytoplasmic kinase regulates plant immunity Beimi Cui, Qiaona Pan, Wenqiang Cui, Yiqin Wang, Verity I. P. Loake, Shuguang Yuan, Fengquan Liu, Gary J. Loake Plant immunity is triggered by the recognition of pathogen/microbial-associated molecular patterns (P/MAMPs) by plant cell surface receptors, leading to a sustained burst of reactive oxygen species (ROS). This study shows that P/MAMP recognition leads to a rapid nitrosative burst, initiating the accumulation of nitric oxide (NO), which subsequently leads to S-nitrosylation of the receptor-like cytoplasmic kinase (RLCK), botrytis-induced kinase 1 (BIK1), at Cys80. This redox-based, posttranslational modification promotes the phosphorylation of BIK1, resulting in BIK1 activation and stabilization. BIK1 S-nitrosylation also increases its physical interaction with RBOHD, the source of the apoplastic oxidative burst, promoting ROS formation. These findings identify mechanistic links between rapid NO accumulation and the expression of PTI, providing insights into plant immunity. The study shows that NO is required for flg22-induced ROS production in Arabidopsis. NO is involved in the regulation of BIK1 stability and activity. BIK1 is S-nitrosylated during PTI, and this S-nitrosylation is critical for BIK1 phosphorylation and activation. The S-nitrosylation of BIK1 at Cys80 is required for BIK1 phosphorylation and activation during PTI. The study also shows that S-nitrosylation of BIK1 at Cys80 is required for the oxidative burst and contributes to resistance against Pst DC3000 hrcC⁻. The study provides a molecular framework for the function of (S)NO during PTI. Following P/MAMP recognition, total cellular (S)NO, governed by AtGSNOR1, increases rapidly, leading to the S-nitrosylation of BIK1 at Cys80, promoting the phosphorylation of BIK1, thereby enhancing both the stability of BIK1 and its interaction with RBOHD. This may help drive the oxidative burst leading to pathogen resistance. However, as (S)NO concentrations increase during the later stages of PTI, AtRBOHD may become S-nitrosylated at Cys890, in a similar fashion to that which occurs during ETI, decreasing ROS synthesis. Analogously, our data show that high SNO levels decrease other PTI responses, including callose deposition and PTI-related gene expression. This complex NO-related molecular dialogue may therefore serve to both promote and subsequently curb PTI. The study also shows that S-nitros