OsRLCK185 (Os05g0372100) is a receptor-like cytoplasmic kinase of subfamily VII in rice and the counterpart of Arabidopsis PBL27. It is a catalytically active serine/threonine protein kinase that lacks transmembrane and extracellular domains and associates with the inner face of the plasma membrane, where it interacts with the LysM receptor kinase OsCERK1 of the OsCEBiP-OsCERK1 chitin receptor complex (and the peptidoglycan receptor system that shares OsCERK1). After chitin perception OsCERK1 directly phosphorylates OsRLCK185 in its activation-loop region, and OsRLCK185 dissociates from the receptor and phosphorylates downstream substrates. It phosphorylates the C-terminal regulatory domain of the MAP kinase kinase kinase OsMAPKKKepsilon (OsMAPKKK24) and also phosphorylates OsMAPKKK18, connecting the receptor to the OsMKK4-OsMPK3/OsMPK6 cascade; silencing OsRLCK185 suppresses chitin- and peptidoglycan-induced MAPK activation, ROS production and defence gene expression. It is targeted by the Xanthomonas oryzae type III effector Xoo1488, which blocks its phosphorylation by OsCERK1, and it is also phosphorylated by the OsFLS2-OsSERK2 flagellin receptor complex and contributes to flg22-induced defence gene expression. Additional reported partners include OsDRE2a, which it phosphorylates, and the receptor-like kinases OsRLK902-1/2, which stabilise it.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0002768 immune response-regulating cell surface receptor signaling pathway | EXP PMID:23498959 A receptor-like cytoplasmic kinase targeted by a plant patho... | MODIFY | Summary: PHI-base annotation from Yamaguchi et al. 2013: OsRLCK185 associates with and is directly phosphorylated by the chitin receptor kinase OsCERK1, and silencing it suppresses chitin- and peptidoglycan-induced immune responses including MAPK activation. Reason: Correct but less specific than warranted. Chitin and peptidoglycan are PAMPs perceived by cell surface pattern recognition receptors, and OsRLCK185 is the kinase that receives the signal directly from OsCERK1 (and also from the OsFLS2-OsSERK2 flagellin receptor). The is_a descendant cell surface pattern recognition receptor signaling pathway (GO:0002752) is more informative and matches the treatment of the same row on OsCERK1, of PBL27, and of the chitin_perception module. Proposed replacements: cell surface pattern recognition receptor signaling pathway Supporting Evidence: PMID:23498959 In response to chitin, OsRLCK185 associates with, and is directly phosphorylated by, OsCERK1 at the plasma membrane. PMID:23498959 Silencing OsRLCK185 suppressed peptidoglycan- and chitin-induced immune responses, including MAP kinase activation and defense-gene expression. PMID:38158656 Genetic evidence suggests that OsRLCK176 and OsRLCK185 may function downstream of the OsFLS2-mediated signaling pathway. |
| GO:0004672 protein kinase activity | EXP PMID:23498959 A receptor-like cytoplasmic kinase targeted by a plant patho... | ACCEPT | Summary: PHI-base kinase activity annotation from the OsRLCK185 discovery paper. The cached abstract describes OsRLCK185 as a substrate of OsCERK1; the deep-research summary of the full text reports that OsRLCK185 autophosphorylates and phosphorylates the effector Xoo1488 in vitro, with the K108E kinase-dead variant as control. Reason: OsRLCK185 is an active kinase. Independent work shows that it phosphorylates OsMAPKKKepsilon, OsMAPKKK18 and OsDRE2a. The full text of PMID:23498959 is not cached; the curator's annotation is consistent with all other evidence and is accepted. The more specific protein serine/threonine kinase activity is used in core functions. Supporting Evidence: PMID:28111288 OsRLCK185 interacts with and phosphorylates the C-terminal regulatory domain of OsMAPKKKฮต. PMID:28371870 In vitro phosphorylation experiments showed that OsRLCK185 directly phosphorylates OsMAPKKK18. file:ORYSJ/RLCK185/RLCK185-deep-research-falcon.md OsRLCK185 itself phosphorylated Xoo1488 |
| GO:0004672 protein kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA protein kinase activity from the RLCK VII PANTHER node (PTN002819552), seeded by Arabidopsis RLCK VII members including PBL27 (At5g18610), the OsRLCK185 counterpart. Reason: Phylogenetically sound; OsRLCK185 sits inside the clade of active RLCK VII kinases and has an intact kinase domain, and its activity is experimentally confirmed by substrate phosphorylation assays. Supporting Evidence: PMID:28111288 OsRLCK185 interacts with and phosphorylates the C-terminal regulatory domain of OsMAPKKKฮต. |
| GO:0004672 protein kinase activity | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-based IEA from the Ser/Thr/Tyr kinase catalytic domain and Ser/Thr kinase active site signatures. Reason: Correct; the kinase domain is intact and catalytically active. Less specific than the Ser/Thr kinase term but not wrong. Supporting Evidence: PMID:28371870 In vitro phosphorylation experiments showed that OsRLCK185 directly phosphorylates OsMAPKKK18. |
| GO:0004674 protein serine/threonine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: EC 2.7.11.1 mapping to protein serine/threonine kinase activity. Reason: OsRLCK185 belongs to the Ser/Thr protein kinase family and, per the deep-research summary of Wang et al. 2017, phosphorylates OsMAPKKKepsilon on Ser/Thr rather than Tyr residues. This is the core molecular function, matching the PBL27 review and the chitin_perception module annoton. Supporting Evidence: PMID:28111288 OsRLCK185 interacts with and phosphorylates the C-terminal regulatory domain of OsMAPKKKฮต. file:ORYSJ/RLCK185/RLCK185-deep-research-falcon.md immunochemical tests identified **Ser/Thr**, rather than Tyr, phosphorylation |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: IEA ATP binding from the protein kinase domain and ATP-binding site signatures. Reason: OsRLCK185 is a catalytically active kinase and therefore binds ATP; the conserved ATP-binding lysine (K108) is mutated to make the kinase-dead control used in substrate assays. Supporting Evidence: file:ORYSJ/RLCK185/RLCK185-deep-research-falcon.md Wild-type OsRLCK185, but not kinase-inactive OsRLCK185^K108E^, phosphorylated kinase-dead OsMAPKKKฮต^K49M^ on Ser/Thr |
| GO:0005886 plasma membrane | IDA PMID:23498959 A receptor-like cytoplasmic kinase targeted by a plant patho... | ACCEPT | Summary: IDA (PHI-base) for plasma membrane localization; OsRLCK185 associates with OsCERK1 at the plasma membrane and is detected in microsomal fractions. Reason: Directly supported by the abstract and corroborated by independent BiFC showing OsRLCK185 interactions with OsMAPKKK18 and OsDRE2a at the plasma membrane. OsRLCK185 is a peripheral membrane protein acting on the cytoplasmic face, which is where it meets OsCERK1 and its substrates. Supporting Evidence: PMID:23498959 In response to chitin, OsRLCK185 associates with, and is directly phosphorylated by, OsCERK1 at the plasma membrane. PMID:28371870 OsRLCK185 interacted with OsMAPKKK18 at the plasma membrane in planta. |
| GO:0005886 plasma membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated annotation (ARBA / UniProt subcellular location cell membrane). Reason: Consistent with the experimental plasma membrane localization. Supporting Evidence: PMID:23498959 In response to chitin, OsRLCK185 associates with, and is directly phosphorylated by, OsCERK1 at the plasma membrane. |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000116 | ACCEPT | Summary: Rhea-based IEA (L-seryl-[protein] phosphorylation) from the UniProt catalytic activity record, which is itself by similarity (ECO:0000305). Reason: Consistent with OsRLCK185 being a Ser/Thr kinase that phosphorylates Ser/Thr residues of OsMAPKKKepsilon. Redundant with, and narrower than, protein serine/threonine kinase activity, which is used as the core term. Supporting Evidence: file:ORYSJ/RLCK185/RLCK185-deep-research-falcon.md immunochemical tests identified **Ser/Thr**, rather than Tyr, phosphorylation |
| GO:0043410 positive regulation of MAPK cascade | IDA PMID:28371870 Conservation of Chitin-Induced MAPK Signaling Pathways in Ri... | NEW | Summary: Proposed new annotation. OsRLCK185 directly phosphorylates two MAP kinase kinase kinases that initiate the chitin-induced OsMKK4-OsMPK3/OsMPK6 cascade (OsMAPKKKepsilon/OsMAPKKK24 and OsMAPKKK18), and phosphomimetic OsRLCK185 with OsMAPKKKepsilon activates MAPK3/6 phosphorylation in N. benthamiana. Reason: Participation test: OsRLCK185 performs a step of the regulation itself, by phosphorylating the MAP3K that starts the cascade; this is not merely necessity evidence (although silencing also suppresses chitin-induced OsMPK3/6 activation). Two independent groups identified different MAP3K substrates. Comparator check: the Arabidopsis counterpart PBL27, in the same role relative to MAPKKK5, carries GO:0043410 in GOA (accepted in the PBL27 review). In Arabidopsis the PBL27-MAPKKK5 link is disputed (RLCK VII-4 kinases contribute), but the rice evidence is independent of that dispute. GO:0043410 is not an ancestor or descendant of GO:0002752. Supporting Evidence: PMID:28111288 OsRLCK185 interacts with and phosphorylates the C-terminal regulatory domain of OsMAPKKKฮต. PMID:28111288 Coexpression of phosphomimetic OsRLCK185 and OsMAPKKKฮต activates MAPK3/6 phosphorylation in Nicotiana benthamiana leaves. PMID:28371870 In vitro phosphorylation experiments showed that OsRLCK185 directly phosphorylates OsMAPKKK18. PMID:28371870 These results suggested that OsRLCK185 connects the chitin receptor to the MAPK cascade consisting of OsMAPKKK18-OsMKK4-OsMPK3/6. |
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Download this section (compressed HTML)Q: Which OsRLCK185 substrate, OsMAPKKKepsilon (OsMAPKKK24) or OsMAPKKK18, carries most of the chitin-induced signal to OsMKK4 in rice cells, and are their OsRLCK185 phospho-acceptor sites equivalent to the PBL27 sites on Arabidopsis MAPKKK5?
Suggested experts: Rice immune signalling researchers
Q: Does OsRLCK185 contribute to the chitin-induced ROS burst through a substrate of its own (e.g. OsDRE2a or an OsRBOH), or indirectly, given that the BIK1-type OsRLCK176 and the OsRacGEF1-OsRac1 route are the established ROS branches?
Q: Do rice RLCK VII-4 orthologs act redundantly with OsRLCK185 upstream of OsMAPKKKs, as Arabidopsis RLCK VII-4 kinases do with PBL27?
Experiment: Complement a stable osrlck185 knockout with wild-type, kinase-dead (K108E) and activation-loop phospho-dead (S240A/T241A/T246A) OsRLCK185 and quantify chitin- and peptidoglycan-induced OsMPK3/6 activation and phosphorylation of OsMAPKKK18 and OsMAPKKKepsilon.
Hypothesis: OsRLCK185 kinase activity is required in planta for chitin-induced OsMPK3/6 activation.
Experiment: Map in vitro and chitin-induced in vivo phosphosites by mass spectrometry and test phospho-dead and phosphomimetic MAP3K variants for MAPK activation.
Hypothesis: OsRLCK185 directly phosphorylates defined sites in OsMAPKKK18 and OsMAPKKKepsilon.
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