CLONING OF ASCIDIAN HOMEOBOX GENES PROVIDES EVIDENCE FOR A PRIMORDIALCHORDATE CLUSTER

In order to isolate genes important in controlling embryonic developme nt in Tunicates, a genomic library from the ascidian Ciona intestinali s was screened with a degenerate oligodeoxyribonucleotide encoding the third helix of Antennapedia-type homeoboxes. Fourteen C, intestinalis homeobox genes, corresponding to several classes of homeodomains, hav e been identified. Five of the isolated homeoboxes show their highest homology to members of the Vertebrate HOX clusters. mRNAs for two of t he isolated homeoboxes are present in unfertilized C. intestinalis egg s.