Immune signal perception and integration by cell surface receptors and peptide ligands Plants and animals rely on pattern-recognition receptors (PRRs) to detect infection by recognizing microbe- associated molecular patterns (MAMPs). Plant plasma membrane (PM)-resident receptor kinases (RKs) function as PRRs that sense MAMPs from diverse microbes and collectively contribute to plant immunity. Plant RKs also perceive a wide range of extrinsic and intrinsic signals and regulate growth, reproduction, and environmental adaptation. The signaling pathways mediated by many RKs converge at a subfamily of RKs, namely BAK1/SERKs, that function as shared coreceptors associating with various receptors upon ligand perception modulating plant immunity, growth, and immune homeostasis. The PM-tethered cytoplasmic kinase BIK1 associates with multiple PRR-BAK1 complexes and relays the intracellular signaling events. Microbial infection also induces the gene expression of many secreted peptides, which could function as immunomodulatory phytocytokines perceived by PRRs and fortify plant immunity. This proposal's long-term goal is to elucidate the mechanisms underlying pathogen signal perception and integration by PRR complexes via shared modules in coordination with phytocytokines for a rapid, specific, and robust immune response. The proposed research will address several key questions in the field. The project will elucidate how BIK1-associated PRR receptorsome dynamics are spatiotemporally regulated and relay the diverse immune signaling. As a critical kinase, BIK1 homeostasis, activities, and subcellular dynamics are regulated by the intertwined phosphorylation and ubiquitination modifications. The project will define how the shared BAK1/SERK coreceptors maintain the functional specificity in different receptorsomes. The studies will address how signaling specificity is regulated with the single-cell resolution at the organismal level. The project will also study how immunomodulatory phytocytokines coordinate with microbial patterns to mount effective immunity. The proposed interdisciplinary research will provide ample training opportunities for researchers at different levels, including underrepresented undergraduate and graduate students and postdoctoral fellows, and will advance our understanding of innate immunity and signal transduction at the whole organismal level by identifying new components and delineating novel pathways that regulate immune signal integration, signaling activation, attenuation, and specificity.