POU-DOMAIN SEQUENCES FROM THE FLATWORM DUGESIA-TIGRINA

Redundant primers matching well-conserved sequences within vertebrate and invertebrate POU genes were used in the PCR (polymerase chain reac tion) to detect three different POU-domain-containing genes within the genome of the flatworm, Dugesia tigrina. Two of these genes appear to be close homologues of class-III POU genes previously identified in D ugesia japonica, while the third represents a new class-III POU gene. Nucleotide sequences encoding highly related POU domains within the tw o species of planaria exhibited a surprisingly poor degree of shared i dentity. Since only class-III POU genes have been observed to date in flatworms, these genes may represent ancestral versions of the multipl e classes of POU genes that exist in vertebrates, and may play importa nt roles in the development of metazoan nervous tissue.