| Topic | Key findings | Key sources with year + DOI/URL (no citation IDs) | Notes/limitations |
|---|---|---|---|
| identity/domains | Arabidopsis thaliana CERK1 corresponds to At3g21630 (syn. LYK1/RLK1), a plasma-membrane LysM receptor-like kinase with three extracellular LysM motifs, a transmembrane/juxtamembrane region, and an intracellular Ser/Thr kinase domain. The ectodomain is reported as globular with tightly packed LysMs, disulfide bridges, and glycosylation sites. (pqac-00000005, pqac-00000008, pqac-00000012) | Miya et al., 2007, PNAS, doi:10.1073/pnas.0705147104, https://doi.org/10.1073/pnas.0705147104; Vasquez, 2024, https://doi.org/10.53846/goediss-10844 | Structural fine detail is partly summarized from review/thesis-style sources rather than a primary Arabidopsis structure paper directly retrieved here. |
| ligand specificity | CERK1 is essential for perception/signaling of chitin elicitors; evidence supports preferential recognition of longer chitin oligomers, especially chitin heptamers/octamers, and GlcNAc8-driven receptor activation/dimerization. One source also notes binding to non-branched 1,3-β-D-(Glc) hexasaccharides. All three LysM domains are required for full chitin responsiveness. (pqac-00000000, pqac-00000004, pqac-00000005, pqac-00000012, pqac-00000015) | Miya et al., 2007, PNAS, doi:10.1073/pnas.0705147104, https://doi.org/10.1073/pnas.0705147104; Hu et al., 2021, Int J Mol Sci, doi:10.3390/ijms22063114, https://doi.org/10.3390/ijms22063114 | Miya et al. 2007 established signaling necessity but did not directly prove Arabidopsis CERK1 ligand binding in the same way as later structural/mechanistic work summarized in secondary sources. |
| receptor complex components | Early model: CERK1 can homodimerize upon chitin binding. Current model: CERK1 functions with LysM co-receptors, especially LYK5 and LYK4; LYK5 is often described as the higher-affinity chitin-binding partner, associates with CERK1 after chitin treatment, and is phosphorylated by CERK1. Other CERK1-associated LysM proteins contribute in different contexts, including LYM1/LYM3 for peptidoglycan signaling and LYM2 for plasmodesmal chitin responses. (pqac-00000000, pqac-00000003, pqac-00000009, pqac-00000010, pqac-00000015) | Liu et al., 2019, eLife, doi:10.7554/eLife.44474, https://doi.org/10.7554/eLife.44474; Hu et al., 2021, Int J Mol Sci, doi:10.3390/ijms22063114, https://doi.org/10.3390/ijms22063114 | Exact stoichiometry and sequence of assembly remain model-dependent across studies; some statements come from synthesized literature rather than one decisive experiment. |
| kinase activity/phosphosites | CERK1 has intrinsic kinase activity with autophosphorylation and myelin basic protein phosphorylation in vitro; the juxtamembrane region is required for kinase function. Reported signaling-relevant phosphosites include T479, Y428, T573, and Y557; Y557F reportedly impairs ROS more than MAPK activation, indicating branch-specific signaling. Chitin-induced phosphorylation is central to activation. (pqac-00000001, pqac-00000007, pqac-00000008, pqac-00000011, pqac-00000014) | Miya et al., 2007, PNAS, doi:10.1073/pnas.0705147104, https://doi.org/10.1073/pnas.0705147104; Meresa et al., 2024, Heliyon, doi:10.1016/j.heliyon.2024.e34871, https://doi.org/10.1016/j.heliyon.2024.e34871 | Several phosphosite assignments are summarized from later reviews/theses in the gathered evidence; not all underlying primary phosphosite papers were directly retrieved. |
| downstream signaling | 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. In guard cells, the LYK5-CERK1-PBL27 pathway targets the anion channel SLAH3; PBL27 phosphorylates SLAH3 at S127 and S189, which are required for chitin-induced stomatal closure and antifungal defense. (pqac-00000001, pqac-00000004, pqac-00000010, pqac-00000013) | Liu et al., 2019, eLife, doi:10.7554/eLife.44474, https://doi.org/10.7554/eLife.44474; Zamora et al., 2024, Horticulturae, doi:10.3390/horticulturae10040361, https://doi.org/10.3390/horticulturae10040361 | Specific pathway branches vary by cell type and readout; some roles of BIK1 vs PBL27 are synthesized across studies/reviews. |
| localization/trafficking | CERK1 is localized to the plasma membrane. After chitin perception, LYK5 undergoes CERK1-dependent endocytosis, whereas CERK1 is often reported to remain at the plasma membrane. Regulatory trafficking modules summarized in recent literature include PUB12/13-mediated turnover, EXO70B2-associated recycling, and dephosphorylation by CIPP1 as negative feedback. (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000014, pqac-00000015) | Miya et al., 2007, PNAS, doi:10.1073/pnas.0705147104, https://doi.org/10.1073/pnas.0705147104; Hu et al., 2021, Int J Mol Sci, doi:10.3390/ijms22063114, https://doi.org/10.3390/ijms22063114 | The degradation route for CERK1-complex components is still described as debated in a 2024 synthesis source. |
| quantitative/statistics | In Miya et al. 2007, elicitor-responsive transcription was strongly CERK1-dependent: 1,222 genes were upregulated in WT versus only 3 in cerk1-1, and 421 downregulated in WT versus 2 in cerk1-1. 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 (~20% larger), with n=86 and n=102 and P < 0.01. Experimental inoculum included 5 × 10^5 spores mL^-1. (pqac-00000008, pqac-00000014) | Miya et al., 2007, PNAS, doi:10.1073/pnas.0705147104, https://doi.org/10.1073/pnas.0705147104 | Quantitative kinetics/binding constants for Arabidopsis CERK1 were limited in the gathered evidence; many recent sources were more mechanistic than numerically detailed. |
| recent developments 2023-2024 | Recent syntheses emphasize CERK1 as an active RD kinase coreceptor in a broader chitin receptor network, with phosphosite-specific signaling outputs, dynamic receptor regulation, and links to systemic resistance after root chitin perception. A 2024 Arabidopsis study found Trichoderma atroviride-induced ISR was compromised in a chitin-receptor mutant, yet soil-applied chitin-triggered systemic resistance was not, suggesting partial separation between beneficial-fungus ISR and canonical chitin-CERK1 signaling. Recent reviews also frame CERK1-centered modules as templates for understanding horticultural crop immunity. (pqac-00000006, pqac-00000011, pqac-00000013) | Meresa et al., 2024, Heliyon, doi:10.1016/j.heliyon.2024.e34871, https://doi.org/10.1016/j.heliyon.2024.e34871; Zamora et al., 2024, Horticulturae, doi:10.3390/horticulturae10040361, https://doi.org/10.3390/horticulturae10040361; Sakai et al., 2024, Microbes Environ, doi:10.1264/jsme2.me24038, https://doi.org/10.1264/jsme2.me24038 | 2023-2024 Arabidopsis CERK1 primary literature in the gathered evidence is limited; some recent insights come from reviews or from studies focused on adjacent pathways/contexts. |
| applications | CERK1 knowledge is being used conceptually for crop protection via carbohydrate elicitors (especially chitin/chitooligosaccharides), receptor engineering, and transfer of LysM receptor modules across species to improve fungal resistance. Reviews highlight use of chitin-based elicitors as alternatives to chemical control and translation of Arabidopsis CERK1-LYK5-PBL27-MAPK paradigms into horticultural crops. (pqac-00000011, pqac-00000013) | Meresa et al., 2024, Heliyon, doi:10.1016/j.heliyon.2024.e34871, https://doi.org/10.1016/j.heliyon.2024.e34871; Zamora et al., 2024, Horticulturae, doi:10.3390/horticulturae10040361, https://doi.org/10.3390/horticulturae10040361 | Application evidence here is mostly translational/review-based rather than field-deployed Arabidopsis CERK1 implementations with agronomic performance metrics. |


*Table: This table summarizes literature-supported functional annotation evidence for Arabidopsis thaliana CERK1/LYK1, including receptor identity, ligand recognition, signaling partners, phosphoregulation, localization, quantitative findings, and recent translational relevance.*