Mitochondrial Sequence Reveals High Levels of Gene Flow Between Breeds of Domestic Sheep from Asia and Europe

Abstract

Sequence variation present within the mitochondrial genome was used to investigate genetic diversity within sheep breeds from Asia and Europe. Comparison of 2027 bp of sequence from 121 animals revealed 44 phylogenetically informative nucleotide positions and a single insertion/deletion. A total of 57 haplotypes were observed which formed two distinct clades. Type A haplotypes were found in breeds from Asia (India, Indonesia, Mongolia, and Tibet), while type B haplotypes were observed at the highest frequency in breeds sourced from Europe (nine breeds from Austria, Aland, Finland, Spain, and northwestern Russia). The distribution of haplotypes indicates sheep appear to have the weakest population structure and the highest rate of intercontinental dispersal of any domestic animal reported to date. Only 2.7% of the sequence variation observed was partitioned between continents, which is lower than both goat (approximately 10%) and cattle (approximately 50%). Diagnostic restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR) tests which distinguish type A and B haplotypes were used to test an additional 223 animals from 17 breeds of European and Asian origin. A mixture of the two lineages was found in every breed except Suffolk and the Indian Garole, indicating introgression has played a major part during breed development and subsequent selection.

Mitochondrial diversity and the origin of Iberian sheep

“…The presence of certain Iberian individuals showing the Asian haplotype, A, was not unexpected, in line with its presence in European sheep (e.g. Milchschaf breed in our study), and in accordance with a high gene flow between Asian and European sheep [11]. However, the most relevant result from Iberian exploration was the identification of two individuals showing haplotype C. The recently reported type C has proven more frequent in Anatolian sheep [13] than in other Asiatic breeds [5,8,20], and within Europe it has been found, so far, only in Portugal [14].…”

“…In sheep, mtDNA investigation has recently allowed for the identification of two new maternal lineages [8,13,20] in addition to the two previously reported types [9,21], which indicates multiphyletic origins for modern breeds; and further recent information about mtDNA variability in sheep is also available with certain data concerning Iberian sheep [11,14].…”

Haplogroup relationships between domestic and wild sheep resolved using a mitogenome panel

“…To select two animals, representative of each haplogroup, all samples previously sequenced by the authors (Meadows et al, 2005(Meadows et al, , 2007 were pooled (n ¼ 318) and a conservative, weighted median-joining diagram constructed using Network 4.1.1.2 (http://www.fluxus-engineering.com) (Supplementary Figure 1). Network construction was as described previously (Meadows et al, 2007).…”

Genetic diversity and population structure of different varieties of Morada Nova hair sheep from Brazil

“…mtDNA fragments from ND5 (Tserenbataa et al, 2004) and the D-loop (Meadows et al, 2005) were amplified with previously published primers and conditions: ND5L (5'-AATAGT TTATCCAGTTGGTCTTAGG-3'), ND5RI (5'-AAGATTTGTTGGAGATCTCAGGTG-3'); and MTCR-F2 (5'-AACTGCTTGACCGTACATAGTA-3'), MTCR-R1 (5'-AGAAGGGTATA AAGCACCGCC-3'), respectively. Purified PCR fragments were sequenced with an ABI PRISM 3730 ® instrument, with BigDye v3.0 chemistry.…”