CASPL4C2

CASP-like protein 4C2 (PtCASPL4C2) is a small tetraspan membrane protein belonging to the CASP-like (CASPL) subfamily, the more divergent relatives of the bona fide Casparian strip membrane domain proteins (CASP1-5). Like other family members it has a central MARVEL-like four-transmembrane domain and is predicted to reside in the plasma membrane as a multi-pass protein. CASP-like proteins are not enzymes; by analogy with the characterized CASP scaffolds they are thought to organize plasma-membrane microdomains, but the specific biological role and tissue context of CASPL4C2 remain uncharacterized. Notably, by orthology within the unified CASP/CASPL nomenclature, the Arabidopsis member AtCASPL4C1 (and its watermelon ortholog ClCASPL) is cold-inducible and broadly expressed, and acts as a negative regulator of growth, biomass and flowering time and a modulator of cold tolerance, apparently functioning in vascular tissue independently of root Casparian strip formation. The protein is predicted to form homodimers and heterodimers. In poplar, PtCASPL4C2 is phloem-enriched at baseline and is salt- and heat-induced under stress (EBI Expression Atlas E-MTAB-5540 / E-GEOD-81077).