EVOLUTION OF ACTIN GENE FAMILIES OF SEA-URCHINS

The actin gene family of the sea urchin Lytechinus pictus includes a s ingle muscle actin gene, LpM, and four cytoskeletal actin genes: LpC1, LpC2, LpC3, and LpC4. The origin and relationship of these actin gene s to members of the actin gene family of the sea urchin Strongylocentr otus purpuratus were considered. Comparison of deduced amino acid sequ ences suggested a close relationship between LpC1 and the CyI-CyII sub family of S. purpuratus actin genes, and between LpC2 and the CyIII su bfamily of S. purpuratus actin genes; the muscle actin genes were orth ologous. It is proposed that two divergent cytoskeletal actin genes of the common ancestral sea urchin gave rise by duplication to the extan t cytoskeletal actin genes of these species, some of which have change d 3' noncoding sequences while others have maintained a terminus highl y conserved among sea urchin actin genes.