The Relationship Between DNA Methylation And Heterosis

Heterosis, a widely existing biological phenomenon, has been successfully exploited on breeding of many animals. However, because of the complexity of heterosis mechanism and the restriction of studying method, great advance had not been achieved on prediction of heterosis, which limits its further utilization. So, the study of heterosis mechanism and forecast still needs to be carried out.In this experiment, three parental lines Large White, Landrace, Meishan and their hybrids Large White × Landrace, Landrace × Large White, Large White×Meisha, Meishan×Large White were used as the source of DNA samples, the high performance liquid chromatography(HPLC) was used for the determination of DNA methylation contents both in the blood and muscle tissue of pigs. At the same time, the significant differences in DNA methylation contents between parental lines and their hybrids, based on different hybrid systems and different tissues, were analyzed. In addition, the association analyses between DNA methylation and quantity traits were performed. These will offer theory support for heterosis. Lastly, the methylation-special PCR was used for amplification of the CpG island of IGF2 gene's second promoter. A useful method for exploring methylation mode of special DNA fragment is established. The main results are as follows:1. The HPLC for detecting DNA methylation content was firstly established in the laboratory, and the detection of 163 muscle DNA samples and 182 blood samples was completed.2. The DNA methylation contents were compared in different tissues: the average methylation is 16.92% in 163 muscle samples and 6.49% in 182 blood samples, the difference between which is highly significant(p<0.01).3. In the blood of Large White, Landrace and their hybrids, the DNA methylation content in hybrids was highly significantly higher than that in parents (p<0.01), which manifests negative heterosis. The difference between hybrids was highly significant (p<0.01), so the result between reciprocal crosses was different. In the blood of Large White, Meishan and their hybrids, the difference between Meishan X Large White hybrid and parents was highly significant(p<0.01), but there was no significant difference between Large White X Meishan hybrids and parents. The methylation content in hybrids was higher than parents, which manifests positive heterosis. There was highly significant difference between hybrids (p<0.01). The result between reciprocal crosses was different.