Abstract
We sampled 119 Nelore cattle (Bos indicus), 69 harboring B. indicus mtDNA plus 50 carrying Bos taurus mtDNA, to estimate the frequencies of putative mtDNA single nucleotide polymorphisms (SNPs) and investigate their association with Nelore weight and scrotal circumference estimated breeding values (EBVs). The PCR restriction fragment length polymorphism (PCR-RFLP) method was used to detect polymorphisms in the mitochondrial asparagine, cysteine, glycine, leucine and proline transporter RNA (tRNA) genes (tRNAasn, tRNAcys, tRNAgly, tRNAleu and tRNApro). The 50 cattle carrying B. taurus mtDNA were monomorphic for all the tRNA gene SNPs analyzed, suggesting that they are specific to mtDNA from B. indicus cattle. No tRNAcys or tRNAgly polymorphisms were detected in any of the cattle but we did detect polymorphic SNPs in the tRNAasn, tRNAleu and tRNApro genes in the cattle harboring B. indicus mtDNA, with the same allele observed in the B. taurus sequence being present in the following percentage of cattle harboring B. indicus mtDNA: 72.46% for tRNAasn, 95.23% for tRNAleu and 90.62% for tRNApro. Analyses of variance using the tRNAasn SNP as the independent variable and EBVs as the dependent variable showed that the G ® T SNP was significantly associated (p < 0.05) with maternal EBVs for weight at 120 and 210 days (p < 0.05) and animal's EBVs for weight at 210, 365 and 455 days. There was no association of the tRNAasn SNP with the scrotal circumference EBVs. These results confirm that mtDNA can affect weight and that mtDNA polymorphisms can be a source of genetic variation for quantitative traits.
Highlights
Mitochondria are eukaryotic cell organelles involved in various cellular functions, including cell proliferation, apoptosis and, mostly important, energy production (Birch-Machin, 2006) by oxidative phosphorylation (Taanman, 1999)
The aims of this study were to estimate the frequency of single nucleotide polymorphisms of the mitochondrial genes for asparagine transfer RNA (tRNA), cysteine tRNA (Pegoraro et al, 1996), glycine tRNA, leucine tRNA and proline tRNA in B. indicus and B. taurus mitochondrial DNA (mtDNA) from public GenBank sequences AY126697 and AY526085 in Brazilian Nelore cattle and to investigate the effects of these polymorphisms on weight and scrotal circumference estimated breeding values at different ages
All the cattle genotyped showed no sign of heteroplasmy for the five single nucleotide polymorphisms (SNPs) analyzed, suggesting maternal inheritance and homoplasmic distribution within tissues (Attardi, 1985; Smith et al, 2000;Birky, 2001)
Summary
Mitochondria are eukaryotic cell organelles involved in various cellular functions, including cell proliferation, apoptosis and, mostly important, energy production (Birch-Machin, 2006) by oxidative phosphorylation (Taanman, 1999). These organelles are responsible for approximately 90% of the energy produced by the mammal cell (Boettcher et al, 1996b). Mitochondria have their own genome, which is maternally inherited in mammals and is an important source of cytoplasmic genetic variation The effect of cytoplasmic inheritance has been studied in respect to milk production (Bell et al, 1985; Tess et al, 1987; Schutz et al, 1992; Boettcher et al, 1996a) and beef cattle growth traits (Tess and Robison, 1990; Northcutt et al, 1991; Tess and MacNeil, 1994; Quintanilla et al, 1999)
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