Centre for Genetic Diseases, Hudson Institute of Medical Research and Department of Molecular and Translational Science, Monash University, 27-31 Wright Street, Clayton, Vic 3168, Australia.
BMC Genet. 2018 Jul 6;19(1):41. doi: 10.1186/s12863-018-0629-4.
The mitochondrial genome (mtDNA) is an emerging determiner of phenotypic traits and disease. mtDNA is inherited in a strict maternal fashion from the population of mitochondria present in the egg at fertilisation. Individuals are assigned to mtDNA haplotypes and those with sequences that cluster closely have common origins and their migration patterns can be mapped. Previously, we identified five mtDNA haplotypes in the commercial breeding lines of Australian pigs, which defined their common origins, and showed how these mtDNA haplotypes influenced litter size and reproductive function in terms of egg and embryo quality and fertilisation efficiency.
We have determined whether mtDNA haplotypes influence other phenotypic traits. These include fat density; muscle depth; fat to leanness ratios; lifetime daily gain; teat quality; muscle score; front and rear leg assessments; percentage offspring weaned; weaning to oestrus intervals; gilt age at selection; and gestational length. In all, we assessed 5687 pigs of which 2762 were females and 2925 were males. We assessed all animals together and then by gender. We further assessed by gender based on whether a sire had joined with females from only one haplotype or from more than one haplotype. We determined that fat density, muscle depth, fat to leanness ratios, lifetime daily gain and teat quality were influenced by mtDNA haplotype and that there were gender specific effects on teat quality.
Our data illustrate that mtDNA haplotypes are associated with a number of important phenotypic traits indicative of economic breeding values in breeding pigs with gender-specific differences. Interestingly, there are 'trade offs' whereby some mtDNA haplotypes perform better for one selection criterion, such as muscle depth, but less so for another, for example teat quality, indicating that pig mtDNA haplotypes are afforded an advantage in one respect but a disadvantage in another.
线粒体基因组（mtDNA）是表型特征和疾病的新兴决定因素。mtDNA 严格按照母系遗传，由受精时卵子中存在的线粒体群体遗传。个体被分配到 mtDNA 单倍型，那些序列聚类密切的个体具有共同的起源，它们的迁移模式可以被绘制出来。此前，我们在澳大利亚猪的商业养殖品种中鉴定出了 5 种 mtDNA 单倍型，这些单倍型确定了它们的共同起源，并展示了这些 mtDNA 单倍型如何影响产仔数和繁殖功能，包括卵子和胚胎质量以及受精效率。
我们已经确定了 mtDNA 单倍型是否会影响其他表型特征。这些特征包括脂肪密度、肌肉深度、脂肪与瘦肉比、终生日增重、乳头质量、肌肉评分、前肢和后肢评估、断奶后代百分比、断奶至发情间隔、母猪选择时的年龄和妊娠期长度。总共评估了 5687 头猪，其中 2762 头是母猪，2925 头是公猪。我们对所有动物进行了评估，然后按性别进行了评估。我们还根据父本是否只与一个单倍型的母本交配，或与多个单倍型的母本交配，按性别进一步进行了评估。我们发现，脂肪密度、肌肉深度、脂肪与瘦肉比、终生日增重和乳头质量受 mtDNA 单倍型影响，并且乳头质量存在性别特异性影响。
我们的数据表明，mtDNA 单倍型与许多重要的表型特征相关，这些特征表明了繁殖猪的经济选育值，并且存在性别特异性差异。有趣的是，存在“权衡”，即一些 mtDNA 单倍型在一个选择标准（如肌肉深度）上表现更好，但在另一个标准（如乳头质量）上表现较差，这表明猪 mtDNA 单倍型在一方面具有优势，但在另一方面具有劣势。
