Establishing a zebrafish transgenic line expressing tilapia lysozyme with enhanced antibacterial activity

In recent years, infectious disease caused by Streptococcus agalactiae has increased in aquaculture, threatening the healthy development of tilapia and resulting in substantial economic losses. Cultivating disease-resistant tilapia by transgenic technology is one strategy that has been developed to address this issue. Here, we used a transposon system to investigate gene expression and tissue lytic activity in transgenic zebrafish expressing the tilapia lysozyme. The transpose vector contained the Tgf2 transposon skeleton, tilapia heat shock protein 70 promoter (Hsp70) and two target genes (tilapia C-type lysozyme 3 [lysozyme-C3] and green fluorescent protein [GFP]). The transgenic zebrafish F-0 generation was obtained by microinjecting the donor vector and transposase mRNA into fertilized zebrafish eggs. There was 45% green fluorescence in the zebrafish F-0 generation, which was spread over the entire body based on microscope observation. The F-0 generation was reared to sexual maturity, at which point individuals were mated with wild-type zebrafish to produce the F-1 generation. Tilapia lysozyme-C3 expression was detected in the liver of F-1 generation by RT-PCR and western blotting, but was not detected in the skin, intestine, or muscle. Significantly higher liver bacteriolysis activity was detected in transgenic zebrafish compared with wild-type zebrafish. Therefore, transgenic zebrafish may have an increased potential for bacterial resistance.