Recently, at the 2016 annual meeting of the Key Laboratory of Freshwater Fish Resources and Reproductive Development, the researchers of Southwest University, the University of Maryland and the Ehime University of Japan jointly released the first tilapia indoor artificial breeding technology system. The manual control of fish sex is achieved, which can greatly increase the income of aquaculture.

    Tilapia is known as the “protein source that does not require protein” and is an excellent breeding target recommended by the Food and Agriculture Organization of the United Nations to countries around the world. For a long time, there are two technical problems in artificially cultured tilapia: males grow 50% faster than females, and farmers want to raise males; after females mature, they produce eggs once every 14 days, and only one in one pond. Mother fish, when naturally propagated, will cause the fish in the pond to be mixed in size, affecting the commerciality of the same batch of fish, and also wasting aquaculture resources.

    Professor Wang Deshou, dean of the School of Life Sciences at Southwest University, and Ph.D. supervisor, began researching tilapia 16 years ago. He collaborated with the University of Maryland and Ehime University in Japan to use RAPD, AFLP and PCR to randomly amplify the sex determination interval, and screened five X or Y chromosome-specific molecular markers to determine the chromosome corresponding to LG23. Chromosomes, and found that Marker-5 is closest to the sex-determining gene.

    Afterwards, Professor Wang's team used the molecular marker (Marker-5) obtained by screening to combine the constructed Nile tilapia microarray Fosmid genomic library to clone the Nile tilapia sex-determining gene amhy, amhy only in XY. (male fish) gonad expression. Using the CRISPR/Cas9 technique to knock out amhy in XY individuals, the gonads develop into ovaries; in XY individuals knocking out amhrII, complete reversal also occurs.

    The research results were published in the American journal of genetics "PLoS Genetics", which was cited more than 20 times by "Scientific Reports" and "Biology of Reproduction", which attracted wide attention from the academic community.

    Dr. Li Minghui, a member of the team of Professor Wang, said that the result of the research is that the male fish (XY) is induced by estrogen to make it female, and the fish eggs are produced, and then fertilized by ordinary male fish to breed " Super male fish (YY), after fertilizing the female fish (XX) with super male fish, the whole male fish (XY) is obtained. This means that the tilapia sex will be manually controlled.

    It is reported that the cloning of sex-determining genes is a hot and difficult problem in the fields of genetics, developmental biology, animal reproduction biology and basic biology of aquatic products. Of the nearly 50,000 species of vertebrates currently in the world, fewer than 10 sex-determining genes have been found (amhy of tilapia is one of them). Researchers have isolated more sex-determining genes and studied their functions from the most evolved crustaceans with lower evolutionary status, and are essential for elucidating the evolutionary patterns and characteristics of vertebrate sex-determining genes.

    At present, the results of Southwest University have been applied to a fishery in Guangdong. It uses molecular marker-assisted breeding technology. The biological characteristics of tilapia have not changed much, and the third-generation fish is actually on the market. Food safety Guaranteed.