| Evidence level | Claim | Key details/assay | Source (authors, year, journal) | URL/DOI |
|---|---|---|---|---|
| Direct (AtCASPL1B2) | **Target identity:** AtCASPL1B2 corresponds to **UniProt Q9SUP0 / At4g20390** and is a **Group 1 CASPL** family member in *Arabidopsis thaliana* | Primary family analysis explicitly identifies AtCASPL1B2/Q9SUP0; belongs to CASPL/CASP-related MARVEL-like 4TM family (pqac-00000000) | Roppolo et al., 2014, *Plant Physiology* | https://doi.org/10.1104/pp.114.239137 |
| Direct (AtCASPL1B2) | **Localization inference with direct construct evidence:** AtCASPL1B2 can localize to the **Casparian strip membrane domain (CSD)** when expressed under the **AtCASP1 promoter** | mCherry-tagged AtCASPL1B2 showed CSD localization in **2 independent lines**; **13 lines** had no detectable fluorescence under this assay, indicating limited/variable detectable expression or stability in this context (pqac-00000000) | Roppolo et al., 2014, *Plant Physiology* | https://doi.org/10.1104/pp.114.239137 |
| Family-level | **CASP proteins are membrane scaffolds that define the CSD and organize localized lignification** | Four-transmembrane proteins; stable ring-like CSD; proposed recruitment/organization of lignin-polymerization machinery including PER64-associated processes; multiple CASP knockouts disrupt strip continuity (pqac-00000002, pqac-00000003, pqac-00000004) | Pfister et al., 2014, *eLife*; Roppolo et al., 2014, *Plant Physiology* | https://doi.org/10.7554/eLife.03115 ; https://doi.org/10.1104/pp.114.239137 |
| Family-level | **Barrier-function consequence of defective CSD/CASP organization:** loss of strip integrity causes strong apoplastic bypass and selective ion-homeostasis defects | PI tracer assay used **15 mM PI (10 mg/mL), 10 min**; ionomics across multiple labs/growth systems found **K decreased 1.4–3.0-fold**, **Mg increased 1.5–2.1-fold**, **Cs increased 1.3–1.4-fold** in *sgn3*; low-K hypersensitivity observed (pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000012) | Pfister et al., 2014, *eLife* | https://doi.org/10.7554/eLife.03115 |
| Family-level, recent (2023) | **Updated mechanism:** CASPs are not strictly required to initiate localized lignification, but are required to organize/fuse microdomains and displace secretory foci for a sealed barrier | In **caspQ** quintuple mutants, lignin forms disorganized microdomains; CASPs mediate **EXO70A1** eviction and promote microdomain fusion into a continuous band; proximity labeling implicated **RabA GTPases** (pqac-00000001, pqac-00000005, pqac-00000007, pqac-00000008) | Barbosa et al., 2023, *Nature Communications* | https://doi.org/10.1038/s41467-023-37265-7 |
| Family-level, recent (2024) | **Arabidopsis CASP/CASPL family context:** Arabidopsis has a large CASP/CASPL repertoire with root/endodermis-enriched members | Bioinformatic survey identified **39 Arabidopsis CASP genes**; most are root enriched; **AtCASP_like1** and **AtCASP_like31** were highlighted as strongly endodermis-enriched candidates linked to CS formation (pqac-00000015, pqac-00000019, pqac-00000020) | Xue et al., 2024, *International Journal of Molecular Sciences* | https://doi.org/10.3390/ijms25189858 |
| Family-level review | **Developmental timing benchmark for CS vs suberin deposition** | Review summarizes that detectable **Casparian strip lignification appears ~12 cells after onset of elongation**, whereas detectable **suberin lamellae appear ~38 cells after onset**; supports distinct timing of barrier components (pqac-00000014) | Nawrath et al., 2013, *The Arabidopsis Book* | https://doi.org/10.1199/tab.0167 |


*Table: This table compiles the strongest direct and family-level evidence relevant to AtCASPL1B2/Q9SUP0, separating gene-specific observations from broader CASP/CASPL functional inferences. It is useful for building a cautious annotation when direct experimental data on this specific Arabidopsis protein are limited.*