Lineage-specific evolution of zona pellucida genes in fish.

The zona pellucida (ZP) protein constitutes the egg envelope, which surrounds the vertebrate embryo. We performed a comprehensive study on the molecular evolution of ZP genes in Teleostei by cloning and analyzing the expression of ZP genes in fish of Anguilliformes in Elopomorpha, Osteoglossiformes in Osteoglossomorpha, and Clupeiformes in Otocephala to cover unsurveyed fish groups in Teleostei. The present results confirmed findings from our previous reports that the principal organ of ZP gene expression changed from ovary to liver in the common ancestors of Clupeocephala.