A SURVEY OF HOMEOBOX GENES IN CHAETOPTERUS-VARIOPEDATUS AND ANALYSIS OF POLYCHAETE HOMEODOMAINS

A survey of genomic DNA hom the polychaete Chaetopterus variopedatus w as conducted using the polymerase chain reaction. Twelve unique homeob ox-containing gene fragments were recovered. Phylogenetic analysis ind icates that seven of the fragments are from genes belonging to Hox hom eobox classes. Other fragments show orthology with Xlox, caudal, and P rh homeobox classes, with two fragments not definitely assignable to a homeobox class by our analysis. Orthology with gene sequences reporte d for the polychaete Ctenodrilus serratus, by Dick and Buss (1994), wa s calculated and indicated that at least eight of the C. variopedatus fragments are homologous to these previously reported sequences. Tabul ation of the Hox gene relationships suggest that polychaetes have repr esentative genes of each of the Hox cognate groups except Abd-B. This conclusion further suggests that the Hox cluster in the basal protosto me ancestor had already undergone the gene duplications leading to the complete complement of homeotic genes known in Drosophila, with the p ossible loss of Abd-B in the polychaete lineage. (C) 1997 Academic Pre ss.