The Fast Growth And Sterility Of The Growth Hormone Gene Transgenic Triploid Carps

Studies on the transgenic commercial fishes have made substantial progress in America, Canada and China, producing transgenic Atlantic Salmon, transgenic Oncorhynchus kisutch and the "all-fish" growth hormone gene transgenic carps. However, there is no classical case of successful industrialization of transgenic animal in the world. The main bottleneck of transgenic fish industrialization is the worry of the potential ecological safety. The transgenic fish would hybridized with some related natural species in sexual mating way, resulting drift of the transferred genes which would pollute the wild gene pool and destroy species variety. The key point to solve the ecological risk of transgenic fish is to control their fertility. The studies on the foundational theory and technology of fertility control on transgenic fish have become important research subject. There is no doubt that producing sterile triploid transgenic fish is one of the idea way to solve the ecological risk.The College of Life Sciences of Hunan Normal University and the cooperating institution have successfully create bisexual fertile allotetraploid hybrid crucian carps (4n=200), which have maintained for 16 generation (F3-F18). In recent years, the population of improved tetraploid crucian carps has been obtained by using gynogenetic methods, which is also reproductive and stable. The hybridization between the allotetraploids and diploid fish species produced all-triploid progeny. Three different abortive gonads were found in the triploid fish, including sterile ovarian ovary-like, sterile testis-like and sterile fat-like forms. The forming of allotetraploid and improved tetraploid crucian carp populations provide plenty of parents for producing fertile triploid fish on a large scale. Consequently, the crossing between tetraploid crucian carps and diploid transgenic carps could produce fertile triploid progenies with a proportion of 100%, which would solve the public worry about the potential ecological safety of transgenic fish industrialization. And in this study, improved allotetraploid crucian carps were mated with diploid transgenic yellow river carps with additional grass carp growth hormone (GCGH) gene. The transgenic triploid carps (positive fish) and the non-transgenic triploid carps (negative fish) were obtained. Furthermore, the characteristics of their growth and reproductive development were studied in the expectation of experiment data for industrialization of GH gene transgenic carps.The major results were presented as follows:The 100%triploid carps with 150 (3n=150) chromosomes were obtained by crossing the improved tetraploid hybrids (♀,4n=200) of red crucian carp x common carp with yellow river carp(♂,2n=100). Based on PCR detection with the special primers, the transgenic triploid carps (positive triploid fish) and the non-transgenic triploid carps (negative triploid fish) were identified among the triploid carps. The positive fish took up a proportion of 44.2%. Through tissue section observation, the gonads of positive triploid fish at the age of 24 months were found to be sterile, which were not able to produce mature gametes when it was breeding season. Morphologically, both the positive and negative triploid fish were similar. They had spindle-shaped, laterally compressed body in steel grey and two pairs of barbells. Most of the countable and measurable traits of the triploid carps were intermediate between those of paternal and maternal parents. In the past two years, the positive and negative triploid fish were raised in the same ponds. The mean body weight of the positive triploid fish was 2.3 times as heavy as that of the negative triploid fish and the highest body weight of positive triploid fish was 2.91 times as heavy as that of the negative triploid fish. Thus, this study not only indicated the fast growth rate of the transgenic triploid carps, bus also eliminated the ecological risk of the transgenic triploid carps when they were raised in the waters because they could not mate with any other fish to produce progeny.