The Study On Mechanisms For The Different Tolerance To PRRS Viruses Between Tongcheng And Landrace Pigs

Porcine reproductive and respiratory syndrome (PRRS) is one of the most damaging contagious swine diseases, which is caused by a small positive single-stranded RNA virus - PRRS Virus (PRRSV).Host genetic background contributes much to the defenses to virus infection, however, little is known about the mechanisms under this contribution. The purpose of this study is to identify host genetic variations that are related to the different tolerances to PRRSV between different pig breeds.The analysis of the clinical syndromes of different pig breeds after infection with HP-PRRSV showed that Tongcheng pigs is more tolerances to PRRSV than Landrace pigs (The above work were mainly completed by Huazhong Agricultural University). Transcriptome analyses of lung tissues from Tongcheng and Landrace pigs infected with HP-PPRSV and control individuals were performed. There were 244, 652, 764 genes with significantly altered expression (DEGs) at 3, 5, 7 day after inoculation in Tongcheng, which was less than that of those (2035, 2037, 843) in Landrace when compared with control individuals. Then, I merged the DEGs in the three time points and obtained 1288 DEGs in Tongcheng pigs, which is less than the half of that in Landrace pigs (2746 DEGs). The only 913 genes were overlapped between 1288 and 2746 DEGs, which indicate that the two pig breeds had a different regulation on genes’ expression. Further analysis showed that the DEGs (2746) in Landrace were marked larger magnitude of expression change than that of DEGs (1288) in Tongcheng compared with control. Combined with the results above, I identified six candidate anti-PRRS genes {BID, BTG2,SOD1, BCL-XL, MX1 and IFIT1). Overexpressed all of them significantly inhibited the replication of PRRSV in Marc-145 cells. Moreover, the dual-luciferase experiment analysis showed that two SNPs in Tongcheng pigs but not in Landrace pigs located in the conserved seed region in 3’UTR of BTG2 and BID significantly changed the relative activity of luciferase compared with that in Landrace. These results indicate that the SNPs located in the 3’UTR regions of BTG2 and BID genes might be related to the different expression patterns of them between the two pig breeds.In addition, I identified 4024 lncRNAs that related to PRRSV infection and they also exhibited an overall reversed expression pattern between the two pig breeds. Among them, compared with control individuals, I identified 305 IncRNAs with reversed expression pattern between the two pig breeds at 3 dpi. NEAT1-IncRNA, which has been proved to play a role in the HIV infectin, was found to be upregulated at 3 dpi in the both pig breeds. Our findings indicate that IncRNAs might be involved in the process of PRRSV infection.By analyzing the miRNA expression profiles of lungs from control and infected Tongcheng and Landrace pigs, we obta:ined the following conclusions: 1. There were 278 known and 294 novel miRNAs were expressed totally. 2. There were 52,62,76 miRNAs with significantly altered expression (DEmiRNAs) at 3, 5, 7 day after inoculation in Tongcheng and 72, 75, 109 DEmiRNAs in Landrace compared with control individuals. 3. The qRT-PCR results of the DEmiRNAs were consistent with the miRNA sequencing data. 4. The miR-2320-5p was predicted to bind to conserve sequences of 3’UTR in the PRRSV genome, was down regulated significantly at 3 dpi after PRRSV infection in both breeds. 5. In addition, compared with control, PRRSV infection significantly increased the miRNA editing level in both breeds.In conclusion, this study found that the genes’ expression patterns were different between Tongcheng and Landrace pigs after infection with PRRSV. I identified six candidate genes,which might relate to PRRSV infection, and noncoding RNAs (IncRNA and miRNAs) that were involved during PRRSV infection. I also identified two SNPs in Toncheng pigs but not in Landrac pigs that can change the activity of dual luciferase significantly, compared with that in Landrace. This study gave us the increased insights to the molecular mechanisms of genetic variation contribute to differences in tolerance to PRRSV and provide an important scientific foundation for the development of new effective anti-PRRS methods and anti-virus breeding.