| Claim/Topic | Evidence summary | System/assay | Key quantitative/statistical details (as available) | Source (with year, journal, DOI URL) |
|---|---|---|---|---|
| Target identity and family assignment | AtCASPL4C1 is the Arabidopsis ortholog discussed for At3g55390 and is annotated as CASP-LIKE PROTEIN 4C1; it belongs to the CASP/CASPL family within the plant MARVEL-like superfamily. | Orthology/annotation and phylogenetic analysis | Arabidopsis CASP/CASPL family noted as 39-member UPF0497/CASPL-related set; gene studied via SALK_034800C knockout and ortholog overexpression. (pqac-00000007, pqac-00000008) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Protein topology | AtCASPL4C1 is predicted to encode a four-pass membrane protein, consistent with CASP/CASPL family topology. | Bioinformatic transmembrane prediction | Predicted TM helices at aa 36–56, 78–98, 119–139, and 160–180. (pqac-00000008) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Subcellular localization | The watermelon ortholog ClCASPL-GFP co-localized with a plasma-membrane RFP marker; Yang et al. use this to support plasma-membrane localization for the Arabidopsis ortholog AtCASPL4C1. | Transient expression of ClCASPL-GFP in tobacco with PM-RFP co-marker | Localization was exclusive to the plasma membrane in the heterologous assay. (pqac-00000007, pqac-00000008) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Expression pattern | AtCASPL4C1 is broadly expressed rather than root-endodermis-specific: promoter-GUS signal was seen in roots (vascular cylinder, not root tip), emerged lateral roots, leaves, floral organs, and siliques, but not seeds. | Promoter-GUS reporter lines plus in silico expression analysis | Broad organ expression; specifically noted as not root-predominant unlike canonical CASP1-5. (pqac-00000005, pqac-00000008) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Cold inducibility | AtCASPL4C1 transcript and promoter activity are induced by cold stress, supporting a role in cold-response biology. | Cold treatment time course with transcript analysis and GUS staining | Induction reported over 72 h at 10°C, with transcript peak around ~48 h after cold exposure. (pqac-00000005, pqac-00000006) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Knockout growth phenotype under normal conditions | Loss of AtCASPL4C1 increases growth vigor: mutant plants had slightly longer primary roots, faster growth, larger plants, increased biomass, and earlier flowering relative to WT and ClCASPL overexpressors. | SALK T-DNA knockout phenotyping on MS medium and soil | Means ± SD reported; n=20 stated for phenotyping; significance tested (Student's *t*-test in methods/legend, and Tukey test in figure legend). Exact values are figure-based rather than text-extracted. (pqac-00000005, pqac-00000007, pqac-00000009) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Cold tolerance phenotype | AtCASPL4C1 knockout shows enhanced cold tolerance, whereas overexpression of the watermelon ortholog in Arabidopsis increases cold sensitivity. | Seedling and soil-grown plant cold assays at 10°C; root growth, Fv/Fm, rosette leaf number, dry weight | Assays included 5-day-old seedlings shifted to 10°C for 7 d and 21-day-old plants exposed to 10°C for 10 d; mutant showed longer roots, higher Fv/Fm, more rosette leaves, and greater dry weight than WT/OX lines; statistical significance indicated in figures. (pqac-00000006, pqac-00000007, pqac-00000009, pqac-00000010) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| Casparian strip / barrier role of AtCASPL4C1 | Despite family membership, AtCASPL4C1 knockout did not show a significant Casparian strip defect in roots, implying its primary demonstrated role is not essential CS assembly. | PI barrier assay and lignin staining of roots; CASP1-5 transcript checks | PI staining used 15 µM PI for 10 min on 5-day-old roots; lignin staining remained present in WT, mutant, and OX lines; CASP1 increased in knockout and CASP2-5 also increased, suggesting compensatory/redundant transcriptional responses. (pqac-00000005, pqac-00000006, pqac-00000008) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299 |
| CASP vs CASPL distinction in Arabidopsis root barrier biology | Canonical CASP1-5 are endodermis-specific, immobile, stable microdomain proteins required to organize proper Casparian strip membrane-wall microdomains; they shape exclusion zones and membrane-wall adhesion but are not strictly required to position initial lignin foci. | Quintuple CASP knockout, microscopy, proximity labeling, barrier and lignin assays | Full CASP knockout caused disorganized, excessively thick lignified foci and impaired exocyst dynamics; CASP1-turboID identified 332 enriched proteins, including RabA GTPases; dominant-negative RabAs caused a weak but reproducible delay in barrier formation. (pqac-00000001, pqac-00000002, pqac-00000004) | Barbosa et al. 2023, *Nature Communications*, https://doi.org/10.1038/s41467-023-37265-7 |
| Evidence that tested CASPLs do not substitute for CASPs in CS formation | Barbosa et al. examined endodermis-expressed CASPLs and found their expression timing/pattern did not explain early CS lignin microdomains; higher-order caspQ plus multiple caspl knockouts were not more severe than caspQ alone. | RNA-seq expression analysis, fluorescent CASPL fusions, undecuple mutant genetics | Seven CASPL1-clade members were examined; a caspQ 6x-caspl mutant showed no stronger phenotype than caspQ, arguing tested CASPLs are functionally distinct from CASPs in CS formation. (pqac-00000003, pqac-00000000) | Barbosa et al. 2023, *Nature Communications*, https://doi.org/10.1038/s41467-023-37265-7 |
| Functional interpretation for AtCASPL4C1 | Current direct evidence supports AtCASPL4C1 as a broadly expressed four-pass plasma-membrane CASPL protein that negatively regulates growth and cold tolerance, with no demonstrated essential role in Arabidopsis Casparian strip formation. | Synthesis of genetic, expression, localization, and barrier assays | Conclusion is based on one Arabidopsis T-DNA mutant study plus family-context work showing CASPLs are generally distinct from canonical CASPs in CS microdomain organization. (pqac-00000005, pqac-00000006, pqac-00000003, pqac-00000004) | Yang et al. 2015, *Scientific Reports*, https://doi.org/10.1038/srep14299; Barbosa et al. 2023, *Nature Communications*, https://doi.org/10.1038/s41467-023-37265-7 |


*Table: This table consolidates the key experimental evidence for Arabidopsis AtCASPL4C1 (Q9M2U0/At3g55390), including localization, expression, cold-response phenotypes, and Casparian strip relevance. It also distinguishes the specific role of canonical CASPs from broader CASPL family members using the 2023 CASP microdomain study.*