STRUCTURE AND EVOLUTION OF CYI CYTOPLASMIC ACTIN-ENCODING GENES IN THE INDIRECT-DEVELOPING AND DIRECT-DEVELOPING SEA-URCHINS HELIOCIDARIS-TUBERCULATA AND HELIOCIDARIS-ERYTHROGRAMMA

The CyI cytoplasmic actin-encoding genes of Heliocidaris erythrogramma (He), a direct-developing sea urchin, and H. tuberculata, an indirect developer, were isolated and compared to the homologous CyI gene of a nother indirect developer, Strongylocentrotus pur purpuratus. Comparis ons show that despite the differences in development, the actin gene s tructures and sequences are highly similar, The coding and 3' untransl ated regions are conserved. The 5' He regulatory region has an inserte d repeat element, but is otherwise similar to its homologues in the ar rangement of presumptive transcription control elements.