| Aspect | Key finding for rice OsCCaMK/OsDMI3 (Q6AVM3) | Evidence / quantitative detail | Source (date, URL) |
|---|---|---|---|
| Target identity / disambiguation | The literature consistently identifies rice **CCAMK/CCaMK** as **OsDMI3**, a **calcium/calmodulin-dependent protein kinase** in *Oryza sativa*; a classic rice locus used in foundational AM papers is **Os05g41090 (CCAMK)**. A Tos17 insertion was reported between the **CaM-binding domain** and **three EF hands**, matching the UniProt domain architecture. | Explicit rice identifier **Os05g41090 (CCAMK)**; mutant structure supports kinase + CaM-binding + EF-hand identity. (pqac-00000008, pqac-00000009) | Gutjahr et al., *Plant Cell* (2008), https://doi.org/10.1105/tpc.108.062414; Ni et al., *Plant Signaling & Behavior* (2020), https://doi.org/10.1080/15592324.2020.1813999 |
| Molecular function / enzyme class | OsCCaMK/OsDMI3 is a **Ser/Thr protein kinase** that acts as a **Ca2+/calmodulin-responsive decoder** of calcium signals. | In rice, kinase activity was measured by **in-gel kinase assay** after immunoprecipitation; assay used **myelin basic protein (MBP)** as substrate. Activity increased after saline-alkaline treatment. (pqac-00000002, pqac-00000003) | Ni et al. (2020), https://doi.org/10.1080/15592324.2020.1813999 |
| Assay conditions for kinase activity | Rice OsDMI3 kinase assays were performed under **Ca2+/CaM-containing conditions**, supporting biochemical classification as a Ca2+/CaM-dependent kinase. | Reaction conditions included **25 mM Tris-HCl pH 7.5, 5 mM MgCl2, 0.5 mM CaCl2, 2 mM calmodulin**; kinase activity significantly increased **1 h after 75 mM NaHCO3 (pH 8.0)** treatment. (pqac-00000003) | Ni et al. (2020), https://doi.org/10.1080/15592324.2020.1813999 |
| Known substrate / interacting partner | The best-supported direct downstream target for plant CCaMKs, including the rice symbiosis framework, is **CYCLOPS/IPD3**, which **interacts with and is phosphorylated by CCaMK**. | Rice symbiosis literature states CYCLOPS is a phosphorylation substrate of CCAMK; pathway models place **CCAMK → CYCLOPS** downstream of Ca2+ spiking. (pqac-00000006, pqac-00000013, pqac-00000014) | Gutjahr et al. (2008), https://doi.org/10.1105/tpc.108.062414 |
| Putative downstream effectors in saline-alkaline stress | Under saline-alkaline stress, OsDMI3 promotes expression of **OsSOS1** and plasma-membrane H+-ATPase genes **OsA3** and **OsA8**; these are supported as downstream outputs, but **direct phosphorylation was not established** in this paper. | After **75 mM NaHCO3**, OsDMI3 OE lines showed lower root **Na+** accumulation and lower **Na+ / H+ influx** than WT; KO lines showed the opposite. The study explicitly notes that direct phosphorylation of these transport systems remains unresolved. (pqac-00000000, pqac-00000003) | Ni et al. (2020), https://doi.org/10.1080/15592324.2020.1813999 |
| Regulation by Ca2+, CaM, autoinhibition | CCaMK family proteins are regulated by **both Ca2+ and Ca2+/CaM** and contain a **CaM-binding/autoinhibitory domain**. Conserved regulatory phosphorylation sites include **T265** (autophosphorylation-associated autoinhibitory control) and **S337** (within/near the CaM-binding region; negative regulatory role). | Family-level mechanistic work shows **T265D** can create autoactive forms; **S337D** reduces CaM binding/substrate phosphorylation; these data are strong for plant CCaMKs, though not all were measured directly for rice OsDMI3 in the retrieved rice papers. (pqac-00000001, pqac-00000004, pqac-00000007) | Katzer dissertation (2017), https://doi.org/10.5282/edoc.24793; Bellon dissertation (2021), https://doi.org/10.5282/edoc.28624; Singh dissertation (2014), https://doi.org/10.5282/edoc.16950 |
| Domain architecture / substrate-sensing logic | Plant CCaMKs possess an N-terminal **kinase domain**, a **CaM-binding/autoinhibitory region**, and a C-terminal **EF-hand Ca2+-binding region**; these features underpin calcium-signal decoding. | Retrieved texts describe **two visinin-like plus one non-canonical EF-hand** organization and show that disruption/deletion of EF-hand region impairs symbiotic function. Rice mutant insertion between CaM-binding region and EF hands further supports this architecture. (pqac-00000001, pqac-00000008, pqac-00000010) | Katzer (2017), https://doi.org/10.5282/edoc.24793; Gutjahr et al. (2008), https://doi.org/10.1105/tpc.108.062414; Singh (2014), https://doi.org/10.5282/edoc.16950 |
| Subcellular localization | CCaMK is most strongly supported as a **nuclear** signaling kinase in symbiosis, where it forms a complex with CYCLOPS and decodes nuclear Ca2+ spiking. | Nuclear localization is directly supported in Lotus and used in cross-species mechanistic interpretation; rice pathway papers place CCAMK downstream of nuclear Ca2+ spiking and upstream of CYCLOPS, consistent with nuclear action. Direct rice localization evidence was not retrieved here. (pqac-00000001, pqac-00000005, pqac-00000012) | Katzer (2017), https://doi.org/10.5282/edoc.24793; Shimoda et al., *Planta* (2019), https://doi.org/10.1007/s00425-019-03264-6; Gutjahr et al. (2008), https://doi.org/10.1105/tpc.108.062414 |
| Core pathway role | OsCCaMK/OsDMI3 is a central component of the **common symbiosis signaling pathway (CSSP/SYM pathway)**, acting **downstream of Ca2+ spiking** and upstream of transcriptional reprogramming via CYCLOPS. | Rice **ccamk** mutants display impaired AM interactions and altered AM-marker gene expression; pathway figures explicitly place **CASTOR/POLLUX → Ca2+ spiking → CCAMK → CYCLOPS**. (pqac-00000006, pqac-00000012, pqac-00000014) | Gutjahr et al. (2008), https://doi.org/10.1105/tpc.108.062414 |
| AM symbiosis phenotype in rice | Loss of rice CCAMK strongly impairs **arbuscular mycorrhizal colonization**, with fungal entry defects and failure of proper cortical colonization. | Figure evidence from the rice AM study shows **reduced root-length colonization** in **ccamk-1** and **ccamk-2** and abnormal epidermal/rhizodermal fungal structures without normal cortical progression. (pqac-00000014, pqac-00000015, pqac-00000016) | Gutjahr et al. (2008), https://doi.org/10.1105/tpc.108.062414 |
| Saline-alkaline tolerance role | Beyond symbiosis, OsDMI3 positively regulates **saline-alkaline tolerance in rice roots** by modulating ion homeostasis. | Experimental setup: **3-day-old seedlings** treated with **75 mM NaHCO3**; Na+/H+ fluxes measured after **24 h** by NMT; RT-PCR after **6 h**; flux data were means ± SEM of **6 independent experiments**. OE plants had longer roots/higher fresh weight under stress; KO plants were more sensitive. (pqac-00000000, pqac-00000003) | Ni et al. (2020), https://doi.org/10.1080/15592324.2020.1813999 |
| Recent / current understanding | Recent reviews and comparative studies continue to treat CCaMK as an **ancient, highly conserved symbiotic signaling hub**, with the **CCaMK–CYCLOPS** module retained across land-plant evolution. | 2023 review summarizes **CCaMK-CYCLOPS-DELLA** as central to AM signaling; 2024 evolutionary study argues conservation of the module across **~450 million years** of land-plant evolution. These are not rice-specific functional assays but support current expert consensus. (pqac-00000006) | Wu et al., IntechOpen chapter (2023), https://doi.org/10.5772/intechopen.107261; Vernié et al., bioRxiv (2024), https://doi.org/10.1101/2024.01.16.575147 |


*Table: This table summarizes experimentally supported and strongly inferred functional-annotation facts for rice OsCCaMK/OsDMI3, including identity verification, kinase activity, regulation, localization, pathway role, and key quantitative details with source URLs.*