Characterization of the beta-actin gene of the rice field eel and its phylogeny in fish.

Beta-actin is a member of the actin family of genes,which play important roles in maintaining cytoskeletal structure, cell motility, cell division, intracellular movements and contractile processes. We report here the identification of a beta-actin cDNA of the rice field eel,a teleost fish with a characteristic of natural sex reversal. The cDNA sequence of this gene was 1860 bp in length,encoding a 375 amino acid protein. Amino acid identities of the beta-actin between the rice field eel and other vertebrates including human, chicken, and other fishes, were more than 98%. RT-PCR showed expression of the rice field eel beta-actin in testis, ovotestis, ovary, heart, liver, spleen and brain,suggesting a ubiquitous expression pattern. Phylogenetic tree including all beta-actin cds of teleost fishes was constructed,which suggested consistently that teleost beta-actin can be classified into four types,but no fish has been found contains all the four types of beta-actin gene in its genome. The results that suggest lineage-specific beta-actin loss might happen in the radical evolution of teleost fishes.