Duplication of phospholipase C-δ gene family in fish genomes

Fishes possess more genes than other vertebrates, possibly because of a genome duplication event during the evolution of the teleost (ray-finned) fish lineage. To further explore this idea, we cloned five genes encoding phosphoinositide-specific phospholipase C-δ (PLC-δ), designated respectively PoPLC-δs, from olive flounder (Paralichthys olivaceus), and we performed phylogenetic analysis and sequence comparison to compare our putative gene products (PoPLC-δs) with the sequences of known human PLC isoforms. The deduced amino acid sequences shared high sequence identity with human PLC-δ1, -δ3, and -δ4 isozymes and exhibited similar primary structures. In phylogenetic analysis of PoPLC-δs with PLC-δs of five teleost fishes (zebrafish, stickleback, medaka, Tetraodon, and Takifugu), three tetrapods (human, chicken, and frog), and two tunicates (sea squirt and pacific sea squirt), whose putative sequences of PLC-δ are available in Ensembl genome browser, the result also indicated that the two paralogous genes corresponding to each PLC-δ isoform originated from fish-specific genome duplication prior to the divergence of teleost fish. Our analyses suggest that an ancestral PLC-δ gene underwent three rounds of genome duplication during the evolution of vertebrates, leading to the six genes of three PLC-δ isoforms in teleost fish.