| Aspect | Summary | Key source(s) with year and DOI/URL | Evidence citation |
|---|---|---|---|
| Verified identity | **OsCPS4/OsCyc1** in *Oryza sativa* ssp. *japonica* corresponds to **syn-copalyl diphosphate synthase** (UniProt Q0JF02), a class II diterpene cyclase/CPS in the terpene synthase family; it is distinct from unrelated “CPS4” genes in other species. | Ma et al., 2023, *Communications Chemistry*, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w | (pqac-00000014) |
| Reaction catalyzed | OsCPS4 catalyzes conversion of **(E,E,E)-geranylgeranyl diphosphate (GGPP)** to **syn-copalyl diphosphate (syn-CPP/syn-CDP)**, the syn stereoisomeric CPP branch point intermediate in rice diterpenoid metabolism. | Ma et al., 2023, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w; Lu et al., 2018, *Plant Cell*, DOI: 10.1105/tpc.18.00205, https://doi.org/10.1105/tpc.18.00205 | (pqac-00000014, pqac-00000006) |
| Pathway context | syn-CPP made by OsCPS4 feeds the **syn-CPP branch** leading to **momilactones A/B** and **oryzalexin S**; these are the best-established metabolic fates of syn-CPP in rice and are linked to phytoalexin and allelopathic functions. | Ma et al., 2023, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w; Lu et al., 2018, DOI: 10.1105/tpc.18.00205, https://doi.org/10.1105/tpc.18.00205 | (pqac-00000000, pqac-00000001, pqac-00000012) |
| Genomic context | **CPS4** is part of the rice **momilactone biosynthetic gene cluster (MBGC)** on chromosome 4, together with **KSL4, CYP99A2, CYP99A3, MAS1/2**-related functions that elaborate syn-CPP toward momilactones. | Priego-Cubero et al., 2024, *bioRxiv*, DOI: 10.1101/2024.01.11.572147, https://doi.org/10.1101/2024.01.11.572147 | (pqac-00000002) |
| Downstream step | After OsCPS4 forms syn-CPP, **OsKSL4** performs the first dedicated cyclization toward momilactone biosynthesis, producing the hydrocarbon scaffold used for later oxidation steps. | Priego-Cubero et al., 2024, DOI: 10.1101/2024.01.11.572147, https://doi.org/10.1101/2024.01.11.572147 | (pqac-00000002, pqac-00000008) |
| Structural evidence | 2023 work delivered the first detailed **X-ray/cryo-EM structural analysis** of rice syn-CPS OsCyc1/OsCPS4, including substrate-bound mutant structures and active-site geometry explaining stereochemical control. | Ma et al., 2023, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w | (pqac-00000014, pqac-00000004) |
| Quantitative structural findings | OsCyc1 forms multiple oligomeric states; **tetramers dominate in solution** and are **not required for in vitro activity**. Reported masses include monomer **~88.2 kDa**, truncated construct **~80.8 kDa**, and apparent solution mass **~273 kDa** by static light scattering. | Ma et al., 2023, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w | (pqac-00000000, pqac-00000014) |
| Mechanistic details | Structural analysis identified active-pocket residues near GGPP and measured distances consistent with cyclization (e.g., **2.82 Å** from D367A O to GGPP C19; residues such as H251, C310, I311 near substrate) supporting a mechanistic basis for syn-CPP formation. | Ma et al., 2023, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w | (pqac-00000004) |
| Genetics and phenotype | **Os-cps4** knockout/knockdown causes **loss of syn-CPP-derived diterpenes** and alters disease interactions: no strong role against rice blast in some backgrounds, but **reduced susceptibility to Xoo** and a role in **non-host resistance to *Magnaporthe poae***. | Lu et al., 2018, DOI: 10.1105/tpc.18.00205, https://doi.org/10.1105/tpc.18.00205 | (pqac-00000003, pqac-00000005, pqac-00000012) |
| Quantitative genetics data | In non-host resistance assays, **17 < n < 46** plants were evaluated across *Magnaporthe* species/strains for **Os-cps4ko**, and **33 < n < 43** for **Os-cps4i** lines; susceptibility differences reached **p < 0.05** or **p < 0.005** in some comparisons. | Lu et al., 2018, DOI: 10.1105/tpc.18.00205, https://doi.org/10.1105/tpc.18.00205 | (pqac-00000005, pqac-00000013) |
| Metabolic engineering utility | OsCPS4 has been used in **heterologous co-expression systems** to supply syn-CPP for downstream rice KSL functional studies; a 1-L engineered culture yielded **~5 mg** diterpene product in one scale-up example. | Morrone et al., 2011, *Biochemical Journal*, DOI: 10.1042/BJ20101429, https://doi.org/10.1042/BJ20101429 | (pqac-00000007) |
| Major 2023–2024 developments | Recent advances include: **(1)** first structural/mechanistic dissection of OsCPS4 stereocontrol and oligomerization (2023); **(2)** demonstration that rational mutagenesis can expand product outcome to include **ent-CPP** in addition to syn-CPP (2023); **(3)** 2024 comparative genomics placing **CPS4** within an evolutionarily dynamic **MBGC** across *Oryza*. | Ma et al., 2023, DOI: 10.1038/s42004-023-01042-w, https://doi.org/10.1038/s42004-023-01042-w; Priego-Cubero et al., 2024, DOI: 10.1101/2024.01.11.572147, https://doi.org/10.1101/2024.01.11.572147 | (pqac-00000000, pqac-00000004, pqac-00000002) |
| Localization note | Direct experimental localization evidence was **not retrieved in the available source set**; however, OsCPS4 is annotated by UniProt as a **chloroplastic precursor**, consistent with plastidial GGPP-based diterpenoid biosynthesis, but this should be treated here as database-supported rather than primary-literature-verified from the retrieved texts. | UniProt Q0JF02 (database context supplied by user); no direct primary-paper localization evidence retrieved in available contexts | (pqac-00000014) |


*Table: This table summarizes the verified identity, enzymatic function, pathway role, genomic context, evidence types, and recent 2023-2024 advances for rice OsCPS4/OsCyc1. It is useful as a compact evidence map for functional annotation of UniProt Q0JF02.*