The cells at the periphery of the root cap are continuously sloughed off from the root into the mucilage, and are thought to be programmed to die [1].This family represents a conserved region approximately 60 residues in length within plant root cap proteins, which may be involved in the process.

1: Maize genes specifically expressed in the outermost cells of root cap. Matsuyama T, Yasumura N, Funakoshi M, Yamada Y, Hashimoto T; Plant Cell Physiol 1999;40:469-476. PMID:10427770