The Effects of Mx1 Locus on Immunity Tracts Components in Large White×Meishan F_2 Offspring

The mouse Myxovirus resistance protein 1 （Mx 1） is known to be sufficient to confer resistance to influenza viruses, and genes encoding Myxovirus resistance protein 1 （Mx 1） is, therefore, an interesting candidate gene for disease resistance in farm animals. The porcine Mxl gene has already been identified and characterized based on its homology with mouse Mxl; the full-length coding region of the pig Mxl gene spans 2 545 bp （M65087） and is organized into 17 exons compared with the human ortholog mRNA. In this study, the exons 9, 10, 11 and introns 6, 9 of the porcine Mxl gene were cloned and sequenced; two SNPs were identified in exons 9, 10, 11 but none of the SNPs led to an amino acid exchange, and the other eleven variants were detected in introns 6 and 9, respectively. Differences in allele frequency among Meishan, Large White, Tibetan, Tongcheng, Huainan, and Duroc pigs were observed within intron 9, of which an A ~ G substitution at position 186 was detected as an Msp I PCR-restriction fragment length polymorphism （PCR-RFLP）. The association analysis using the Large WhitexMeishan F2 offspring suggested that the Mxl genotype was associated with variation in several immunity traits that are of interest in pig breeding. However, further investigations in more populations are needed to confirm the above concept.

Association of Single Nucleotide Polymorphisms in Exon 3 of Porcine LMCD1 Gene with Meat Quality and Carcass Traits

LIM domain proteins are found to be important regulators in cell growth, cell fate determination, cell differentiation, and remodelling of the cell cytoskeleton by their interaction with some structural proteins, kinases, transcriptional regulators, etc. The presence of LIM domains in LMCD1 gene implies it may be involved in skeletal muscle protein-protein interactions. This study was to investigate polymorphisms of LIM and cysteine-rich domain 1 （LMCD1） gene and its effect on meat quality and carcass traits in pig. The polymorphism （G294A） in exon 3 region of porcine LMCD1 gene, which is synonymous mutation, was genotyped in the population of 178 F, pigs of a Large White × Meishan resource family. Statistical results indicated the distribution of allele G （with a A → G mutation） and A （without mutation）. Analysis of variance showed that the polymorphism of LMCD1 gene was associated with variation in several carcass traits of interest for pig breeding. Some carcass traits and meat quality traits are close to significance by association. An analysis of more animals is necessary to analyze the polymorphisms in exon 3 of porcine LMCD1 gene if it was selected as a marker for the pig carcass traits.

Identification of Novel Polymorphisms in Porcine Ring Finger Protein 4 and Matrix Metalloproteinase 9 Genes and Association Analysis with Litter Size Traits

Reproduction trait plays an important role in pig production. Identification of molecular markers that are linked to litter size may contribute to the genetic development of porcine reproduction traits. In this study, porcine ring finger protein 4 （pRNF4） and Matrix metalloproteinase 9 （pMMP-9） were selected as candidate genes on the basis of their physiological roles in reproduction. Two single-nucleotide polymorphisms （416C〉T in pRNF4 and - 1257G〉A in pMMP-9） that could be detected by PCR restriction fragment length polymorphism （PCR-RFLP） were discovered and tested for statistical associations with litter size traits in three populations. For 416C〉T, TT genotype was associated with a significantly higher （p〈0.05） number of live births than those recorded for CC sows and the additive effect was significant （p〈0.05） in Qingping and Min Pigs populations in later parities. For -1257G〉A, inconsistent results were found in three populations. The results suggested that T allele in pRNF4 gene might confer a high prolificacy in breeding and further studies were needed to confLrm the results.

Correlation of Individual Heterozygosity of Microsatellite Marker Loci with Heterosis of Growth Traits in Pig Populations

To investigate the correlation of individual heterozygosity and heterosis of three traits in crossbred F1 pig populations, the F1 populations were built by random mating Yorkshire x Meishan （YM, n = 82）, and its reciprocal （MY, n =47） and two straightbred populations （Yorkshire = 34, Meishan = 55） were used as control groups. The heterosis of birth weight （BWT）, average daily gain （ADG）, and feed conversion ratio （FCR） were acquired as well. In the research, the significant marker loci for the heterosis of the three traits were observed by one-way ANOVA （P〈0.01） in a total of 39 marker loci on SSC4, SSC6, SSC7, SSC8, and SSC13, and the numbers of the significant marker loci were 12 （BWT）, 18 （ADG）, and 17 （FCR）, respectively, based on which the general heterozygosity （GH） was divided into significant marker loci heterozygosity （SH） and insignificant marker loci heterozygosity （IH）. Furthermore, the trends of alteration in heterosis with the stepwise increase in heterozygosity by 0.05 were explored. This was done by the regression analysis of the three kinds of heterozygosity against heterosis of the three traits. The results showed that, for BWT, the heterosis increased with the increase in GH （r=0.9337, P=0.0021） and SH （r=0.9165, P=0.0102）; for ADG, the heterosis increased with the increase in IH （r=0.7012, P=0.0353） and GH （r=0.7470, P=0.0537, near significant）; for FCR, the heterosis of feed efficiency increased with the increase in IH （r=0.8721, P=0.0022）. The results indicated that the correlation was not always higher or more significant for SH with heterosis than it was for IH or GH with heterosis, and it might be because of the reciprocal cancellation of the positive effect and negative effect of QTL linked to the significant marker loci.

Analysis of Genetic Diversity and Relationships of Seven Chinese Indigenous Pig Breeds and Three Exotic Pig Breeds Using the DNA Differential Display Technique

The genetic diversity and relationships of seven Chinese indigenous pig breeds （Meishan, Erhualian, Hezuo, Bamei, Qingping, Tongcheng, and Huainan） and three exotic pig breeds （Large White, Landrace, and Duroc） were analyzed using the DNA differential display technique by means of eight primer combinations. A total of 123 reproducible bands were used to calculate mean Nei＇s gene diversity, and mean Shannon＇s information index for each pig population. Based on these the Nei＇s standard genetic identity and distance were estimated, which was used to construct a dendrogram tree for the 10 pig breeds. The experimental results obtained and the method used in this study for evaluating the genetic diversity and relationships of pigs were also discussed.

Detection of Quantitative Trait Loci Associated with Live Measurement Traits in Pigs

Live measurement growth traits are very important economic traits in pig production and breeding. In this research, quantitative trait loci （QTL） were detected for 11 live estimated growth and carcass traits, including birth weight （BWT）, average daily gain over testing periods （ADG3）, live backfat thickness at last 3-4th lumbar （LBFT3）, live loin eye area （LLEA）, and so on, in 214 pig resource family population, including 180 F2 individual, by 39 microsatellite marker loci on SSC4, SSC6, SSC7, SSC8, and SSC13. The results indicated that 4 chromosome significant level QTL and one suggestive QTL were detected for ADG3 （at position of 50 cM on SSC8）, LBFT3 （at position of 147 cM on SSC4）, LLEA （one highly significant at position of 48 cM on SSC7; another significant at position of 125 cM on SSC8） and BWT （suggestive significant at position of 0 cM, at marker sw489 on SSC4）. The phenotypic variance of these QTL accounted for 0.95% to 16.91%. Most of them were mentioned in previous reports; except the QTL of LLEA at position of sw1953 on SSC8 which maybe a new QTL.