Genomic cloning and promoter analysis of the β-actin gene from Korean rose bitterling ( Rhodeus uyekii )

Korean rose bitterling (Rhodeus uyekii), which belongs to the Acheilognathinae subfamily of the Cyprinidae family, has been proposed as a candidate for the development of ornamental fish in Korea. To develop a promoter capable of driving constitutive transgene expression, we identified and characterized the β-actin gene of R. uyekii (Ru-actb). The genomic organization of Ru-actb, which contains six exons, including an unexpressed first exon, is conserved with vertebrate β-actin genes. The Ru-actb gene has several regulatory elements, including a typical CAAT box, an evolutionarily conserved CArG motif, and a TATA box, in the proximal promoter region, and an additional CArG motif in the first intron. The regulatory region of Ru-actb covering from −4,474 bp to the start codon was able to drive the expression of red fluorescent protein in zebrafish and Korean rose bitterling. Ru-actb mRNA was ubiquitously detected in all tissues; highly expressed in brain, kidney, stomach, and intestine; and weakly expressed in eye, gill, fin, hepatopancreas, spleen, muscle, testis, and ovary. These results indicate that the regulatory region of Ru-actb may be used to develop a useful promoter for transgene expression in fish.