Homodimer and heterodimers. Expressed in the root endodermis. In the root endodermis, expressed at a late developmental stage, coinciding with the appearance of metaxylem vessels. In 10-day-old roots, reduced levels in proximity to the hypocotyl and in endodermal cells overlaying lateral root primordia. Belongs to the Casparian strip membrane proteins (CASP) family.