Plant cells can sense conserved molecular patterns through pattern recognition receptors (PRRs) and initiate pattern-triggered immunity (PTI). Details of thePTIsignaling network are starting to be uncovered in Arabidopsis, but are still poorly understood in other species, including soybean (Glycine max). In this study, we perform a forward genetic screen for autoimmunity-relatedlesion mimic mutants(lmms) in soybean and identify two allelic mutants, which carry mutations inGlyma.13G054400, encoding a malectin-like receptor kinase (RK). The mutants exhibit enhanced resistance to both bacterial and oomycete pathogens, as well as elevatedROSproduction upon treatment with the bacterial pattern flg22. Overexpression ofGmLMM1gene inNicotiana benthamianaseverely suppresses flg22-triggeredROSproduction and oomycete patternXEG1-induced cell death. We further show that GmLMM1 interacts with the flg22 receptorFLS2 and its co-receptorBAK1 to negatively regulate flg22-induced complex formation between them. Our study identifies an important component inPTIregulation and reveals that GmLMM1 acts as a molecular switch to control an appropriate immune activation, which may also be adapted to otherPRR-mediated immune signaling in soybean.

Plant cells can sense conserved molecular patterns through pattern recognition receptors (PRRs) and initiate pattern-triggered immunity (PTI). Details of thePTIsignaling network are starting to be uncovered in Arabidopsis, but are still poorly understood in other species, including soybean (Glycine max). In this study, we perform a forward genetic screen for autoimmunity-relatedlesion mimic mutants(lmms) in soybean and identify two allelic mutants, which carry mutations inGlyma.13G054400, encoding a malectin-like receptor kinase (RK). The mutants exhibit enhanced resistance to both bacterial and oomycete pathogens, as well as elevatedROSproduction upon treatment with the bacterial pattern flg22. Overexpression ofGmLMM1gene inNicotiana benthamianaseverely suppresses flg22-triggeredROSproduction and oomycete patternXEG1-induced cell death. We further show that GmLMM1 interacts with the flg22 receptorFLS2 and its co-receptorBAK1 to negatively regulate flg22-induced complex formation between them. Our study identifies an important component inPTIregulation and reveals that GmLMM1 acts as a molecular switch to control an appropriate immune activation, which may also be adapted to otherPRR-mediated immune signaling in soybean.