The CASP-like (CASPL) family

Poplar and Arabidopsis reviews, PANTHER families, and orthology evidence

AI Gene Review · projects/CASPL_FAMILY · 2026

Bottom line

  • CASPLs are small four-span membrane scaffolds; the true CASPs build the Casparian strip, but most CASPLs are uncharacterized.
  • We reviewed 21 poplar and 5 Arabidopsis CASPLs, described 2 PANTHER families, and ran orthology and expression analyses.
  • Function transfers at group level: 20/20 poplar CASPLs hit the same Roppolo group; root-specific CASPL1B1 and stress-induced CASPL4C1 fit their Arabidopsis orthologs.

Can function move from Arabidopsis to poplar?

Why this family

  • A dark family: dozens of members per plant genome, a handful characterized.
  • Poplar reviews borrow hypotheses from Arabidopsis orthologs; that only works if the orthology is real.
  • A family-wide view also fixes the PANTHER descriptions that every member inherits.

Expression backs the transfer

What the annotations show

Set Genes Rows Outcome
Poplar CASPLs 21 21 one IEA plasma membrane row each, all ACCEPT
Arabidopsis orthologs 5 21 13 ACCEPT, 1 non-core, 2 REMOVE, 5 UNDECIDED
  • REMOVE: ISM extracellular region (CASPL1B1) and nucleus (CASPL1D2).
  • UNDECIDED: five HDA Golgi / endosome / TGN rows on CASPL1D1.
  • NEW proposed: CASPL1D1 defense response to bacterium (IMP).
  • PANTHER: PTHR33573 description now separates CASP1–5 from the CASPL bulk; PTHR36488 (IPR044173) described.

Status and next steps

  • ✅ 21 poplar + 5 Arabidopsis reviews; 2 PANTHER families; orthology + expression analyses.
  • ⬜ Peanut and watermelon CASPLs are TrEMBL only, so out of scope.
  • ⬜ Optional extension: rice (29) and maize (23) reviewed CASPL entries.
  • ⬜ CASPL2A1 (poplar) is reviewed but absent from the orthology analysis.

Read more: projects/CASPL_FAMILY.md · projects/CASPL_FAMILY/bioinformatics/RESULTS.md · genes/POPTR/CASPL*/