Actin genes from the sea star Pisaster ochraceus

Genomic and tube foot cDNA recombinant libraries have been prepared from the sea star Pisaster ochraceus. Three major classes of actin-bearing lambda phage clones have been identified on the basis of restriction enzyme mapping and localization of actin coding regions. There are at most six non-allelic actin genes in the sea star genome. Southern blots of restriction enzyme-digested genomic DNA from individual sea stars probed with actin coding sequences indicate extensive polymorphism in actin gene regions. The locations of repetitive sequences within the genomic clones have been mapped. Approx. 1% of cDNA clones prepared from tube foot poly(A) RNA contain actin coding segments. The actin gene(s) from which the tube foot actin transcripts originate have been identified by hybridization with a 460 bp 3' untranslated region from one of the cDNA plasmids. Hybridization of the untranslated region probe with genomic digests demonstrates that there are at least three alleles for the tube foot actin in sea star populations.