Pumilio genes from the Platyhelminthes.

Pumilio proteins are proposed to have a conserved primordial function in the maintenance of proliferation in stem cells through post-transcriptional regulation. In this work, a search for pumilio homology domain (PUM-HD) sequences of pumilio genes from several Platyhelminthes species was performed, including representatives form Cestoda, Trematoda and Tricladida. Only one PUM-HD sequence was found in each triclad species; however, two PUM-HD homologues were found in all the parasitic species. These sequences formed two clearly separated clades: PlatyPum1, with sequences from all species, and PlatyPum2, composed exclusively of neodermatan sequences. Therefore, at least one duplication of the pumilio gene must have occurred before the divergence of cestodes and trematodes. Further duplications of PUM-HD were found in Fasciola hepatica, but these consist of retropseudogenes. This is the first comparative analysis of PUM-HD sequences in the Platyhelminthes and, more generally, in any lophotrochozoan phylum.