| Gene/protein | Evidence type (expression, localization, interaction, mutant phenotype, pathway context) | Key finding | Experimental system/assay | Publication (year, journal) | URL/DOI | Evidence citation id(s) |
|---|---|---|---|---|---|---|
| CASPL1B1 / At5g44550 / Q9FI10 | Expression | Explicitly identified as Arabidopsis locus **At5g44550**; reported to be **exclusively expressed in suberized endodermal cells**, supporting a root endodermis-associated role. | Arabidopsis; promoter-based expression analysis described in study | Champeyroux et al. 2019, *Plant, Cell & Environment* | https://doi.org/10.1111/pce.13537 ; DOI: 10.1111/pce.13537 | (pqac-00000000, pqac-00000001) |
| CASPL1B1 / At5g44550 / Q9FI10 | Interaction | **Physically interacts with aquaporin PIP2;1**; authors propose CASPL1B1 may influence aquaporin regulation via the phosphorylated form of PIP2;1. | Molecular interaction analysis in Arabidopsis study context | Champeyroux et al. 2019, *Plant, Cell & Environment* | https://doi.org/10.1111/pce.13537 ; DOI: 10.1111/pce.13537 | (pqac-00000001) |
| CASPL1B1 / At5g44550 / Q9FI10 | Mutant phenotype | Loss of CASPL1B1-family members did **not** produce a clear whole-root hydraulic conductivity phenotype under control, NaCl, or ABA conditions; evidence supports no major role in bulk root water transport. | Arabidopsis loss-of-function mutants; root hydraulic conductivity (Lpr) assays under control, salt, and ABA treatments | Champeyroux et al. 2019, *Plant, Cell & Environment* | https://doi.org/10.1111/pce.13537 ; DOI: 10.1111/pce.13537 | (pqac-00000001) |
| CASPL1B1 (CASPL1 clade) | Pathway/family context | In a 39-member Arabidopsis CASP-LIKE family context, **CASPL1B1 belongs to the CASPL1 clade**; RNA-seq analyses indicated CASPL1B1 is **up-regulated in myb36 mutant or CIF2 treatment**, linking it to endodermal barrier-defect responses. | RNA-seq/endodermis-focused expression analyses under **myb36** and **CIF2** conditions | Barbosa et al. 2023, *Nature Communications* | https://doi.org/10.1038/s41467-023-37265-7 ; DOI: 10.1038/s41467-023-37265-7 | (pqac-00000002) |
| CASPL1B1 with CASPL family members | Mutant phenotype / redundancy | Simultaneous knockout of **six endodermis-expressed CASPL genes including CASPL1B1** in the **caspQ** background did **not** increase phenotypic severity over caspQ, suggesting redundancy or a nonessential role for early CS defect enhancement. | Higher-order Arabidopsis mutant analysis in **caspQ 6x-caspl** background | Barbosa et al. 2023, *Nature Communications* | https://doi.org/10.1038/s41467-023-37265-7 ; DOI: 10.1038/s41467-023-37265-7 | (pqac-00000002) |
| CASP family (family context for CASPL1B1) | Localization / structural role | CASPs are small **four-transmembrane-span** proteins that form a stable **Casparian strip membrane domain** platform; they are required for proper microdomain ultrastructure, membrane protein exclusion, wall adhesion, and organized strip fusion, but **not strictly for localized lignification initiation**. | Full CASP knockout, fluorescence imaging, ultrastructural analysis, proximity labeling | Barbosa et al. 2023, *Nature Communications* | https://doi.org/10.1038/s41467-023-37265-7 ; DOI: 10.1038/s41467-023-37265-7 | (pqac-00000003, pqac-00000006, pqac-00000008) |
| CASP family (family context for CASPL1B1) | Quantitative barrier phenotype | CASP complementation studies used **propidium iodide (PI) barrier assays**; functional complementation of **caspQ** required multiple CASPs, with **CASP1/CASP3/CASP5** the most effective tested combination; assays included **n = 8** individuals for boxplots and **n = 6** in complementation tests. | PI uptake barrier assay; transgenic complementation lines | Barbosa et al. 2023, *Nature Communications* | https://doi.org/10.1038/s41467-023-37265-7 ; DOI: 10.1038/s41467-023-37265-7 | (pqac-00000004, pqac-00000011) |
| Casparian strip / CASP pathway context | Pathway context | The **Schengen surveillance pathway** monitors Casparian strip integrity through stele-derived **CIF peptides** and **SGN3/GSO1** with downstream **SGN1**; CS establishment depends on **CASPs** plus lignin-polymerizing machinery. | Genetic pathway analysis; MYB36 positive-feedback engineering | Shen et al. 2023, *bioRxiv* | https://doi.org/10.1101/2023.04.19.537470 ; DOI: 10.1101/2023.04.19.537470 | (pqac-00000005) |
| Casparian strip barrier (family/biological context) | Functional relevance / transport barrier | Defective CS mutants (**sgn3**, **sgn4**) showed **higher boron accumulation in shoots** and **faster boric-acid flux into steles** in hydroponics, demonstrating that the CASP-associated endodermal barrier limits apoplastic boric acid entry into the stele under excess B. | Arabidopsis hydroponics, **10B** tracer experiment, stele-specific boric-acid biosensor | Muro et al. 2023, *Frontiers in Plant Science* | https://doi.org/10.3389/fpls.2023.988419 ; DOI: 10.3389/fpls.2023.988419 | (pqac-00000009) |


*Table: This table summarizes direct evidence for Arabidopsis CASPL1B1/At5g44550 and key family-context findings needed for functional annotation. It distinguishes gene-specific data from broader CASP/Casparian strip pathway evidence relevant to interpreting CASPL1B1 function.*