CERK1

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0004672 protein kinase activity	IEA GO_REF:0000002	MARK AS OVER ANNOTATED	Summary: CERK1 has an intracellular serine/threonine protein kinase domain and displays autophosphorylation and substrate (PBL27) kinase activity. This InterPro-based protein kinase activity annotation is correct but is a broad parent of the more specific Ser/Thr kinase term. Reason: The annotation is biochemically correct but is subsumed by the more specific and experimentally supported protein serine/threonine kinase activity (GO:0004674). It is retained as a non-misleading parent term. Supporting Evidence: PMID:18042724 CERK1 is a plasma membrane protein containing three LysM motifs in the extracellular domain and an intracellular Ser/Thr kinase domain with autophosphorylation/myelin basic protein kinase activity
GO:0004674 protein serine/threonine kinase activity	IEA GO_REF:0000003	ACCEPT	Summary: CERK1 has an intracellular Ser/Thr kinase domain and EC 2.7.11.1 catalytic activity (serine and threonine phosphorylation), supported experimentally by autophosphorylation and phosphorylation of PBL27. This is a core molecular function. Reason: Directly supported by experimental characterization of the intracellular Ser/Thr kinase domain and catalytic activity, and by the duplicate IDA annotation from PMID:18042724. Supporting Evidence: PMID:18042724 an intracellular Ser/Thr kinase domain with autophosphorylation/myelin basic protein kinase activity file:ARATH/CERK1/CERK1-deep-research-falcon.md CERK1 has intrinsic kinase activity with autophosphorylation and myelin basic protein phosphorylation in vitro
GO:0005524 ATP binding	IEA GO_REF:0000002	ACCEPT	Summary: As an active protein kinase, CERK1 binds ATP. UniProt annotates the canonical kinase ATP-binding region (residues 328-336) and ATP-binding residue 349. This is a standard, correct molecular function for a kinase. Reason: Consistent with the conserved kinase ATP-binding motif and experimentally demonstrated kinase/autophosphorylation activity requiring ATP. Supporting Evidence: PMID:18042724 an intracellular Ser/Thr kinase domain with autophosphorylation/myelin basic protein kinase activity
GO:0005886 plasma membrane	IEA GO_REF:0000120	ACCEPT	Summary: CERK1 is a single-pass plasma membrane receptor kinase. Plasma membrane localization is well supported experimentally (duplicate IDA annotations below). Reason: Plasma membrane localization is the established site of CERK1 function and is supported by multiple experimental studies. Supporting Evidence: PMID:18042724 as well as the localization of CERK1 in the plasma membrane file:ARATH/CERK1/CERK1-deep-research-falcon.md CERK1 is localized to the plasma membrane.
GO:0009617 response to bacterium	IEA GO_REF:0000117	KEEP AS NON CORE	Summary: CERK1 participates in bacterial perception (peptidoglycan sensing with LYM1/LYM3) and restricts bacterial growth, so a broad "response to bacterium" annotation is appropriate. More specific terms (defense response to bacterium, detection of peptidoglycan) are also present. Reason: Biologically correct but broad; the bacterial role is real but secondary to the core chitin/fungal immune function, and is better captured by the more specific terms also annotated. Supporting Evidence: PMID:19816132 CERK1 mediates perception of an unknown bacterial PAMP in Arabidopsis file:ARATH/CERK1/CERK1-deep-research-falcon.md including LYM1/LYM3 for peptidoglycan signaling and LYM2 for plasmodesmal chitin responses.
GO:0019199 transmembrane receptor protein kinase activity	IEA GO_REF:0000002	ACCEPT	Summary: CERK1 is a single-pass transmembrane receptor with an extracellular ligand (chitin)-binding ectodomain and an intracellular Ser/Thr kinase domain; chitin-induced dimerization activates signaling. This term accurately captures its receptor kinase nature. Reason: Supported by domain architecture and the experimental demonstration that ligand-induced receptor dimerization activates kinase signaling (duplicate IDA/IMP annotations below). Supporting Evidence: PMID:22654057 chitin-induced AtCERK1 dimerization is critical for its activation file:ARATH/CERK1/CERK1-deep-research-falcon.md CERK1 is a single-pass membrane receptor with
GO:0045087 innate immune response	IEA GO_REF:0000120	ACCEPT	Summary: CERK1 is essential for chitin-triggered innate immunity and contributes to bacterial PAMP-triggered immunity. This is a core biological process. Reason: Strongly supported across the literature; cerk1 mutants lose chitin-induced immune responses. Duplicate IMP annotation also present. Supporting Evidence: PMID:18263776 LysM RLK1 is essential for chitin signaling in plants (likely as part of the receptor complex) and is involved in chitin-mediated plant innate immunity file:ARATH/CERK1/CERK1-deep-research-falcon.md CERK1 is a key PRR component required for chitin-induced PTI outputs including MAPK activation, ROS burst, and defense gene induction.
GO:0106310 protein serine kinase activity	IEA GO_REF:0000116	ACCEPT	Summary: Rhea/EC mapping of the serine phosphorylation half-reaction (EC 2.7.11.1). CERK1 phosphorylates serine residues (e.g. autophosphorylation at Ser-266, Ser-268, Ser-274). Correct but redundant with the broader Ser/Thr kinase term. Reason: Biochemically accurate; CERK1 demonstrably phosphorylates serine residues. Consistent with the curated phosphoserine sites. Supporting Evidence: PMID:20610395 chitin, chitin oligomers, and chitosan rapidly induce in vivo phosphorylation of CERK1 at multiple residues in the juxtamembrane and kinase domain
GO:1901701 cellular response to oxygen-containing compound	IEA GO_REF:0000117	MARK AS OVER ANNOTATED	Summary: This very broad ARBA machine-learning term likely derives from chitin (an oxygen-containing carbohydrate) responsiveness, but it is too generic to be informative for CERK1, whose specific roles are captured by "cellular response to chitin" and "response to chitin". Reason: Uninformatively broad ARBA-derived annotation; the specific and accurate response terms (cellular response to chitin, GO:0071323) are already present. Not wrong but over-general. Supporting Evidence: PMID:18263776 The mutation in this gene blocked the induction of almost all chitooligosaccharide-responsive genes
GO:0042802 identical protein binding	IPI PMID:22654057 Chitin-induced dimerization activates a plant immune recepto...	ACCEPT	Summary: CERK1 forms ligand-induced homodimers; a chitin octamer acts as a bivalent ligand driving AtCERK1-ECD dimerization required for activation. "Identical protein binding" captures the self-association, but the more specific "protein homodimerization activity" (also annotated) is preferable. Reason: Self-interaction (homodimerization) is experimentally demonstrated by crystallography and biochemistry. Retained as accurate; complementary to the homodimerization activity annotation. Supporting Evidence: PMID:22654057 a chitin octamer induces AtCERK1-ECD dimerization that is inhibited by shorter chitin oligomers
GO:0004672 protein kinase activity	IMP PMID:24750441 Selective regulation of the chitin-induced defense response ...	MARK AS OVER ANNOTATED	Summary: Kinase activity of CERK1 (mediating chitin-induced phosphorylation of PBL27) is supported by mutant phenotype analysis. Correct but a broad parent of the specific Ser/Thr kinase term. Reason: Biochemically correct but subsumed by the more specific Ser/Thr kinase activity (GO:0004674). Retained as a non-misleading parent. Supporting Evidence: PMID:24750441 In this study we show that PBL27, an Arabidopsis ortholog of OsRLCK185, is an immediate downstream component of the chitin receptor CERK1 and contributes to the regulation of chitin-induced immunity in Arabidopsis.
GO:0050832 defense response to fungus	IMP PMID:18263776 A LysM receptor-like kinase plays a critical role in chitin ...	ACCEPT	Summary: cerk1/lysm RLK1 mutants are more susceptible to fungal pathogens and lose chitin-induced defense, establishing a role in defense response to fungus. This is a core biological process. Reason: Directly supported by loss-of-function phenotypes showing increased susceptibility to fungal pathogens. Supporting Evidence: PMID:18263776 The mutation in this gene blocked the induction of almost all chitooligosaccharide-responsive genes and led to more susceptibility to fungal pathogens file:ARATH/CERK1/CERK1-deep-research-falcon.md Disease phenotype against Alternaria brassicicola showed lesion size 1.37 ± 0.57 mm in cerk1-2 versus 1.14 ± 0.56 mm in Col-0
GO:0005576 extracellular region	ISM GO_REF:0000122	REMOVE	Summary: This sequence-based (AtSubP) prediction is misleading. CERK1 is a single-pass plasma membrane protein with an extracellular ectodomain (the LysM domains face the apoplast), but the protein is not located in the extracellular region; it is membrane-anchored at the plasma membrane. Reason: The protein localizes to the plasma membrane (experimental IDA), not the extracellular region. The ISM prediction conflates the extracellular ectodomain topology with whole-protein localization and is incorrect. Supporting Evidence: PMID:18042724 as well as the localization of CERK1 in the plasma membrane
GO:0005515 protein binding	IPI PMID:29182677 Arabidopsis ubiquitin ligase PUB12 interacts with and negati...	REMOVE	Summary: Captures the interaction between CERK1 and the U-box E3 ligase PUB12 (and PUB13), which negatively regulate CERK1 in a phosphorylation-dependent manner. The generic "protein binding" term is uninformative. Reason: Bare "protein binding" is not informative about molecular function. The specific CERK1-PUB12/PUB13 interaction is documented in the gene notes and better represented by the regulatory biology rather than a generic MF term. Supporting Evidence: PMID:29182677 the ARM domains of PUB12 and its paralog PUB13 interacted with the intracellular domain of CERK1 in a manner that was dependent on its autophosphorylation
GO:0005515 protein binding	IPI PMID:27317676 The Arabidopsis Malectin-Like/LRR-RLK IOS1 Is Critical for B...	REMOVE	Summary: Captures the CERK1-IOS1 (malectin-like/LRR-RLK) interaction relevant to pattern-triggered immunity. Generic "protein binding" is uninformative. Reason: Bare "protein binding" provides no molecular-function information; the specific CERK1-IOS1 interaction is recorded in the gene notes. Supporting Evidence: PMID:27317676 CHITIN ELICITOR RECEPTOR KINASE1 (CERK1) recognize microbe-associated molecular patterns (MAMPs) to activate pattern-triggered immunity (PTI)
GO:0005515 protein binding	IPI PMID:24750441 Selective regulation of the chitin-induced defense response ...	REMOVE	Summary: Captures the CERK1-PBL27 interaction. CERK1 interacts with and phosphorylates the receptor-like cytoplasmic kinase PBL27. Generic "protein binding" is uninformative and is better represented by the kinase-substrate relationship. Reason: Bare "protein binding" is uninformative; the functionally meaningful CERK1-PBL27 kinase-substrate interaction is captured by the kinase activity and protein phosphorylation annotations. Supporting Evidence: PMID:24750441 In this study we show that PBL27, an Arabidopsis ortholog of OsRLCK185, is an immediate downstream component of the chitin receptor CERK1 and contributes to the regulation of chitin-induced immunity in Arabidopsis.
GO:0005515 protein binding	IPI PMID:27679653 The Arabidopsis CERK1-associated kinase PBL27 connects chiti...	REMOVE	Summary: Captures the CERK1-PBL27 association connecting chitin perception to MAPK activation. Generic "protein binding" is uninformative. Reason: Bare "protein binding" is uninformative; the CERK1-PBL27 functional relationship is captured elsewhere (kinase activity, protein phosphorylation, intracellular signal transduction). Supporting Evidence: PMID:27679653 The Arabidopsis CERK1-associated kinase PBL27 connects chitin perception to MAPK activation
GO:0005886 plasma membrane	IDA PMID:24750441 Selective regulation of the chitin-induced defense response ...	ACCEPT	Summary: Experimental localization of CERK1 (and its interaction with PBL27) at the plasma membrane. Core localization. Reason: Direct experimental evidence for plasma membrane localization, consistent with CERK1's role as a cell-surface receptor. Supporting Evidence: PMID:18042724 as well as the localization of CERK1 in the plasma membrane
GO:0005886 plasma membrane	IDA PMID:27679653 The Arabidopsis CERK1-associated kinase PBL27 connects chiti...	ACCEPT	Summary: Experimental localization of CERK1 at the plasma membrane. Core localization; duplicate of the IDA annotation above. Reason: Direct experimental evidence for plasma membrane localization. Supporting Evidence: PMID:27679653 The Arabidopsis CERK1-associated kinase PBL27 connects chitin perception to MAPK activation
GO:0071323 cellular response to chitin	IMP PMID:24750441 Selective regulation of the chitin-induced defense response ...	ACCEPT	Summary: CERK1 is required for cellular responses to chitin, including PBL27 phosphorylation, MPK3/6 activation and downstream defense. Core process. Reason: Supported by mutant phenotypes showing loss of chitin-induced defense responses. Supporting Evidence: PMID:24750441 Knockout of PBL27 resulted in the suppression of several chitin-induced defense responses, including the activation of MPK3/6
GO:0006468 protein phosphorylation	IDA PMID:25036661 LIK1, a CERK1-interacting kinase, regulates plant immune res...	ACCEPT	Summary: CERK1 directly phosphorylates substrates such as the LRR-RLK LIK1 (and PBL27). Protein phosphorylation is a core activity of the kinase domain. Reason: Direct experimental evidence that CERK1 phosphorylates downstream substrates (LIK1 in vitro and in vivo). Supporting Evidence: PMID:25036661 In vitro experiments showed that LIK1 was directly phosphorylated by CERK1
GO:0016301 kinase activity	IDA PMID:25036661 LIK1, a CERK1-interacting kinase, regulates plant immune res...	MARK AS OVER ANNOTATED	Summary: Broad "kinase activity" term. CERK1 is a protein Ser/Thr kinase; the specific Ser/Thr kinase activity terms are preferable. Reason: Correct but uninformatively broad; subsumed by the specific protein serine/threonine kinase activity (GO:0004674). Supporting Evidence: PMID:25036661 In vitro experiments showed that LIK1 was directly phosphorylated by CERK1
GO:0005515 protein binding	IPI PMID:25340959 The kinase LYK5 is a major chitin receptor in Arabidopsis an...	REMOVE	Summary: Captures the chitin-induced CERK1-LYK5 complex, in which the high-affinity chitin receptor LYK5 recruits CERK1. Generic "protein binding" is uninformative; the specific functional interaction is described in the gene notes. Reason: Bare "protein binding" is uninformative. The biologically important chitin-dependent LYK5-CERK1 complex is recorded in the gene notes and reflected in the receptor-complex biology. Supporting Evidence: PMID:25340959 AtLYK5 interacts with AtCERK1 in a chitin-dependent manner
GO:0008061 chitin binding	IDA PMID:22654057 Chitin-induced dimerization activates a plant immune recepto...	ACCEPT	Summary: The CERK1 ectodomain binds chitin directly; the crystal structure of AtCERK1-ECD with a chitin pentamer shows binding mediated by a LysM domain and three NAG residues. Core molecular function. Reason: Direct structural and biochemical evidence for chitin binding by the LysM ectodomain. Supporting Evidence: PMID:22654057 directly binds chitin through its lysine motif (LysM)-containing ectodomain (AtCERK1-ECD)
GO:0008061 chitin binding	IDA PMID:22740685 How plant lysin motif receptors get activated: lessons learn...	ACCEPT	Summary: Review of CERK1 structural biology confirming chitin binding via the LysM ectodomain. Core molecular function; duplicate of other IDA chitin-binding annotations. Reason: Consistent with structural data that CERK1 binds NAG oligomers derived from chitin via its LysM ectodomain. Supporting Evidence: PMID:22740685 CERK1 binds NAG oligomers derived from chitin-the major constituent of fungal cell walls-and mediates immunity to fungal infection
GO:0042803 protein homodimerization activity	IDA PMID:22654057 Chitin-induced dimerization activates a plant immune recepto...	ACCEPT	Summary: Chitin octamer acts as a bivalent ligand inducing CERK1 homodimerization, which is required for receptor activation. This is a core, activating molecular function. Reason: Directly demonstrated by crystallography and biochemistry; mutations attenuating dimerization compromise CERK1-mediated signaling. Supporting Evidence: PMID:22654057 a chitin octamer induces AtCERK1-ECD dimerization that is inhibited by shorter chitin oligomers file:ARATH/CERK1/CERK1-deep-research-falcon.md Early model: CERK1 can homodimerize upon chitin binding.
GO:0042803 protein homodimerization activity	IDA PMID:22740685 How plant lysin motif receptors get activated: lessons learn...	ACCEPT	Summary: Review/structural confirmation that ligand-induced CERK1 homodimerization is required for immune signaling. Duplicate homodimerization annotation. Reason: Consistent with the structural model that NAG octamers stabilize CERK1 dimers to enable signaling. Supporting Evidence: PMID:22740685 Receptor activation and immune signaling requires, however, ligand-induced CERK1 homodimerization
GO:0071219 cellular response to molecule of bacterial origin	IEP PMID:22744984 LYK4, a lysin motif receptor-like kinase, is important for c...	KEEP AS NON CORE	Summary: CERK1 is induced by and participates in responses to bacterial molecules/PAMPs (including peptidoglycan), and CERK1 expression is induced by flagellin. cerk1 mutants show enhanced susceptibility to bacteria. Reason: Real but secondary to the core fungal-chitin function. The bacterial role is genuine (peptidoglycan sensing with LYM1/LYM3; restricting bacterial growth) but peripheral relative to chitin perception. Supporting Evidence: PMID:22744984 enhanced susceptibility to both the bacterial pathogen Pseudomonas syringae pv tomato DC3000 and the fungal pathogen Alternaria brassicicola
GO:0071323 cellular response to chitin	IEP PMID:22744984 LYK4, a lysin motif receptor-like kinase, is important for c...	ACCEPT	Summary: CERK1 is essential for cellular responses to chitin (induction of chitin-responsive genes, cytosolic calcium elevation). Core process; duplicate of the IMP annotation. Reason: Well supported; cerk1 mutants lose chitin-induced cellular responses. Supporting Evidence: PMID:22744984 reduced induction of chitin-responsive genes and diminished chitin-induced cytosolic calcium elevation
GO:0004674 protein serine/threonine kinase activity	IDA PMID:19951949 Direct binding of a plant LysM receptor-like kinase, LysM RL...	ACCEPT	Summary: CERK1 is autophosphorylated in vitro, demonstrating Ser/Thr protein kinase activity of the intracellular kinase domain. Core molecular function. Reason: Direct in vitro evidence of autophosphorylation by recombinant CERK1. Supporting Evidence: PMID:19951949 LysM RLK1-yEGFP was autophosphorylated in vitro
GO:0008061 chitin binding	IDA PMID:19951949 Direct binding of a plant LysM receptor-like kinase, LysM RL...	ACCEPT	Summary: First demonstration of direct, specific, high-affinity (Kd ~82 nM) binding of CERK1 to chitin in vitro. Core molecular function. Reason: Direct biochemical evidence of specific chitin binding by recombinant CERK1. Supporting Evidence: PMID:19951949 we present the first evidence for direct binding of LysM RLK1 to chitin file:ARATH/CERK1/CERK1-deep-research-falcon.md evidence supports preferential recognition of longer chitin oligomers, especially chitin heptamers/octamers, and GlcNAc8-driven receptor activation/dimerization
GO:0008061 chitin binding	IDA PMID:20610395 The lysin motif receptor-like kinase (LysM-RLK) CERK1 is a m...	ACCEPT	Summary: CERK1 is a major chitin-binding protein of Arabidopsis cells; its ectodomain binds chitin (and chitosan) directly, with all three LysM domains required. Core molecular function. Reason: Affinity-purification and direct-binding experiments confirm chitin binding by the CERK1 ectodomain. Supporting Evidence: PMID:20610395 the CERK1 ectodomain binds chitin and partially deacetylated chitosan directly without any requirement for interacting proteins and that all three LysM domains are necessary for chitin binding
GO:0046777 protein autophosphorylation	IDA PMID:19951949 Direct binding of a plant LysM receptor-like kinase, LysM RL...	ACCEPT	Summary: CERK1 autophosphorylates in vitro. Autophosphorylation is a core regulatory feature of the kinase. Reason: Direct experimental evidence of in vitro autophosphorylation. Supporting Evidence: PMID:19951949 LysM RLK1-yEGFP was autophosphorylated in vitro
GO:0046777 protein autophosphorylation	IDA PMID:20610395 The lysin motif receptor-like kinase (LysM-RLK) CERK1 is a m...	ACCEPT	Summary: Chitin, chitin oligomers and chitosan rapidly induce in vivo phosphorylation of CERK1 at multiple residues; kinase activity is required for this chitin-dependent autophosphorylation. Core regulatory process. Reason: Direct evidence of chitin-induced in vivo (auto)phosphorylation requiring CERK1 kinase activity. Supporting Evidence: PMID:20610395 kinase activity of CERK1 is required for its chitin-dependent in vivo phosphorylation
GO:2001080 chitosan binding	IDA PMID:20610395 The lysin motif receptor-like kinase (LysM-RLK) CERK1 is a m...	ACCEPT	Summary: The CERK1 ectodomain binds partially deacetylated chitosan directly in addition to chitin. A specific, experimentally supported molecular function. Reason: Direct binding experiments show the CERK1 ectodomain binds chitosan. Supporting Evidence: PMID:20610395 the CERK1 ectodomain binds chitin and partially deacetylated chitosan directly
GO:0002752 cell surface pattern recognition receptor signaling pathway	IDA PMID:19816132 The LysM receptor kinase CERK1 mediates bacterial perception...	ACCEPT	Summary: CERK1 is a cell-surface pattern recognition receptor that perceives MAMPs (chitin; also a bacterial PAMP) and initiates defense signaling. Core process. Reason: CERK1 functions as a plasma-membrane PRR initiating PAMP-triggered immunity signaling. Supporting Evidence: PMID:19816132 Plants use pattern recognition receptors (PRRs) to perceive pathogen-associated molecular pattern (PAMPs) and initiate defence responses file:ARATH/CERK1/CERK1-deep-research-falcon.md CERK1 activation triggers hallmark PTI responses:
GO:0005515 protein binding	IPI PMID:19249211 AvrPtoB targets the LysM receptor kinase CERK1 to promote ba...	REMOVE	Summary: Captures the interaction between CERK1 and the Pseudomonas syringae type III effector AvrPtoB, which ubiquitinates and degrades CERK1 to suppress immunity. Generic "protein binding" is uninformative. Reason: Bare "protein binding" is uninformative; the CERK1-AvrPtoB interaction (host-pathogen) is documented in the gene notes and is not a constitutive molecular function of CERK1. Supporting Evidence: PMID:19249211 AvrPtoB ubiquitinates the CERK1 kinase domain in vitro and targets CERK1 for degradation in vivo
GO:0042742 defense response to bacterium	IDA PMID:19816132 The LysM receptor kinase CERK1 mediates bacterial perception...	KEEP AS NON CORE	Summary: CERK1 restricts bacterial growth and mediates perception of a bacterial PAMP; cerk1 plants show reduced PAMP-induced defense to bacterial extracts and enhanced bacterial susceptibility. A genuine but secondary defense role. Reason: The bacterial defense role is real (peptidoglycan sensing; restricting bacterial growth) but peripheral to the core chitin/fungal immune function. Supporting Evidence: PMID:19816132 plays an essential role in restricting bacterial growth on plants
GO:0004674 protein serine/threonine kinase activity	IDA PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: Original identification of CERK1 as a receptor kinase with an intracellular Ser/Thr kinase domain displaying autophosphorylation and MBP kinase activity. Core molecular function. Reason: Direct experimental evidence of Ser/Thr kinase activity from the founding CERK1 paper. Supporting Evidence: PMID:18042724 an intracellular Ser/Thr kinase domain with autophosphorylation/myelin basic protein kinase activity
GO:0046777 protein autophosphorylation	IDA PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: The CERK1 kinase domain shows autophosphorylation activity. Core regulatory process; duplicate annotation. Reason: Direct experimental evidence of autophosphorylation. Supporting Evidence: PMID:18042724 an intracellular Ser/Thr kinase domain with autophosphorylation/myelin basic protein kinase activity
GO:0008061 chitin binding	IDA PMID:22744984 LYK4, a lysin motif receptor-like kinase, is important for c...	ACCEPT	Summary: Chitin binding annotation associated with the LYK4 study context. CERK1 chitin binding via its LysM ectodomain is well established by direct biochemical and structural evidence. Core molecular function. Reason: Consistent with the extensive direct evidence that CERK1 binds chitin through its LysM ectodomain. Supporting Evidence: PMID:20610395 the CERK1 ectodomain binds chitin and partially deacetylated chitosan directly
GO:0045087 innate immune response	IMP PMID:22461667 The LysM receptor-like kinase LysM RLK1 is required to activ...	ACCEPT	Summary: CERK1/LysM RLK1 is required to activate chitin-induced defense (and abiotic-stress) responses; loss-of-function abolishes these responses. Core biological process. Reason: Mutant phenotype analysis shows CERK1 is required for chitin-induced immune responses. Supporting Evidence: PMID:22461667 known to play a critical role in signaling defense responses induced by exogenous chitin
GO:0019199 transmembrane receptor protein kinase activity	IMP PMID:22106285 Arabidopsis lysin-motif proteins LYM1 LYM3 CERK1 mediate bac...	ACCEPT	Summary: CERK1 acts as a transmembrane receptor kinase required for bacterial peptidoglycan sensing (with LYM1/LYM3). Confirms receptor kinase function. Core molecular function. Reason: Supported by mutant phenotypes; CERK1 functions as a transmembrane receptor kinase in PAMP perception. Supporting Evidence: PMID:22106285 PGN sensing and immunity to bacterial infection in Arabidopsis thaliana requires three lysin-motif (LysM) domain proteins
GO:0032499 detection of peptidoglycan	IMP PMID:22106285 Arabidopsis lysin-motif proteins LYM1 LYM3 CERK1 mediate bac...	KEEP AS NON CORE	Summary: With LYM1 and LYM3, CERK1 mediates sensing of bacterial peptidoglycan and immunity to bacterial infection. A specific, genuine but secondary process. Reason: Real role in peptidoglycan-mediated bacterial sensing, but secondary to CERK1's core chitin/fungal perception function. Supporting Evidence: PMID:22106285 PGN sensing and immunity to bacterial infection in Arabidopsis thaliana requires three lysin-motif (LysM) domain proteins
GO:0035556 intracellular signal transduction	IDA PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: CERK1 transduces the perceived chitin signal across the plasma membrane into the cytoplasm via its intracellular kinase domain, acting upstream of MAPK activation and ROS. Core process, though a broad term. Reason: CERK1 is positioned upstream of intracellular signaling cascades (MAPK, ROS) and transduces the signal via its cytoplasmic kinase domain. Supporting Evidence: PMID:18042724 CERK1 is involved in the perception of the chitin oligosaccharide elicitor at the cell surface and the transduction of the signal into the cytoplasm via its intracellular serine/threonine kinase activity file:ARATH/CERK1/CERK1-deep-research-falcon.md Activated CERK1 signals through RLCK-VII kinases including PBL27, BIK1, and PBL19, linking receptor activation to ROS production, Ca2+ influx, MAPK cascades, defense gene expression, callose deposition, and stomatal immunity.
GO:0010200 response to chitin	IMP PMID:18263776 A LysM receptor-like kinase plays a critical role in chitin ...	ACCEPT	Summary: CERK1 is essential for the response to chitin; mutants block induction of almost all chitooligosaccharide-responsive genes. Core process. Reason: Mutant phenotype analysis shows CERK1 is required for the chitin response. Supporting Evidence: PMID:18263776 The mutation in this gene blocked the induction of almost all chitooligosaccharide-responsive genes
GO:0005886 plasma membrane	IDA PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: Experimental demonstration that CERK1 is a plasma membrane protein. Core localization; founding study. Reason: Direct experimental evidence for plasma membrane localization. Supporting Evidence: PMID:18042724 as well as the localization of CERK1 in the plasma membrane
GO:0019199 transmembrane receptor protein kinase activity	IDA PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: CERK1 is a plasma membrane receptor kinase with extracellular LysM domains and an intracellular Ser/Thr kinase domain. Core molecular function; duplicate of the IMP annotation. Reason: Founding study establishes CERK1 as a transmembrane receptor kinase. Supporting Evidence: PMID:18042724 CERK1 is a plasma membrane protein containing three LysM motifs in the extracellular domain and an intracellular Ser/Thr kinase domain
GO:0032491 detection of molecule of fungal origin	IEP PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: CERK1 detects the fungal cell wall MAMP chitin at the cell surface, functioning as a master switch of chitin signaling. Core process; duplicate (IEP) of the IMP annotation. Reason: CERK1 perceives chitin (a fungal-origin molecule) and is essential for chitin signaling. Supporting Evidence: PMID:18042724 CERK1 plays a critical role in fungal MAMP perception in plants
GO:0032491 detection of molecule of fungal origin	IMP PMID:18042724 CERK1, a LysM receptor kinase, is essential for chitin elici...	ACCEPT	Summary: cerk1 KO mutants completely lose the ability to respond to chitin elicitor, demonstrating CERK1 is required to detect the fungal MAMP. Core process. Reason: Loss-of-function abolishes chitin detection/response, establishing CERK1's role in detecting a fungal-origin molecule. Supporting Evidence: PMID:18042724 The KO mutants for CERK1 completely lost the ability to respond to the chitin elicitor, including MAPK activation, reactive oxygen species generation, and gene expression file:ARATH/CERK1/CERK1-deep-research-falcon.md Loss-of-function cerk1 mutants lose chitin-elicitor responses (MAPK activation, ROS production, defense gene expression), placing CERK1 at the top of the signaling cascade.

Gene Description

Existing Annotations Review

Core Functions

Binds the fungal cell wall polysaccharide chitin (and partially deacetylated chitosan) through its extracellular three-LysM-domain ectodomain at the plasma membrane, providing the ligand-recognition step of chitin perception.

Functions as a transmembrane receptor protein serine/threonine kinase: chitin-induced homodimerization activates the intracellular kinase domain, which autophosphorylates and phosphorylates downstream substrates (e.g. PBL27, LIK1) to transduce the signal into the cytoplasm.

Acts as a cell-surface pattern recognition receptor that initiates chitin- triggered innate immunity (MAPK activation, ROS, gene induction) and is essential for defense against fungal pathogens; ligand-induced homodimerization is the activating event.

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