In this study, we identified four canonical calmodulin genes in the Pacific abalone, Haliotis discus hannai. Their full-length cDNAs were variable in the 5' and 3' untranslated regions, but highly similar (91-97%) in the coding region. Each of the genes encoded 149 amino acids, with 93-97% similarity among themselves and 94-98% similarity with human CAM I. There were 54 substitutions distributed unevenly throughout the coding regions, found mostly in the third codon position. Gene structure analysis revealed that each of the calmodulin genes comprised five exons and four introns. The intron positions and phases were identical and there were no introns in the fourth exon. The corresponding introns differed in their sequences and sizes. Expression profiles of nine tissues from abalone revealed that the calmodulin genes were transcribed in common in gill and mantle tissue, but differentially in the other tissues. A phylogenetic analysis based on the amino acid sequences revealed that calmodulin C was the most common isoform in Gastropoda and calmodulin was the most diverged isoform. An in silico analysis of the calmodulin genes identified paralogous genes in other Haliotis species, indicating that gene duplication might have occurred in the last common ancestor of Haliotis. Abbreviations: ORF: open reading frame; RACE: random amplification of cDNA end; TSA: transcriptome shotgun assembly; UTR: untranslated region.
Keywords: Calmodulin; calcium signaling; expression profiling; gene structure; invertebrate.