Evolution of the Parvalbumin Genes in Teleost Fishes after the Whole-Genome Duplication

Parvalbumin is considered a major fish allergen. Here, we report the molecular evolution of the parvalbumin genes in bony fishes based on 19 whole genomes and 70 transcriptomes. We found unexpectedly high parvalbumin diversity in teleosts; three main gene types (<i>pvalb-α</i>, <i>pvalb-β1</i>, and <i>pvalb-β2</i>, including oncomodulins) originated at the onset of vertebrates. Teleosts have further multiplied the parvalbumin gene repertoire up to nine ancestral copies—two copies of <i>pvalb-α</i>, two copies of <i>pvalb-β1</i>, and five copies of <i>pvalb-β2</i>. This gene diversity is a result of teleost-specific whole-genome duplication. Two conserved parvalbumin genomic clusters carry <i>pvalb-β1</i> and <i>β2</i> copies, whereas <i>pvalb-α</i> genes are located separately in different linkage groups. Further, we investigated parvalbumin gene expression in 17 tissues of the common carp (<i>Cyprinus carpio</i>), a species with 21 parvalbumin genes in its genome. Two <i>pvalb-α</i> and eight <i>pvalb-β2</i> copies are highly expressed in the muscle, while two alternative <i>pvalb-α</i> copies show expression in the brain and the testes, and <i>pvalb-β1</i> is dominant in the retina and the kidney. The recent pairs of muscular <i>pvalb-β2</i> genes show differential expression in this species. We provide robust genomic evidence of the complex evolution of the parvalbumin genes in fishes.