Genomic and biochemical analysis of oxidative stress in birds with diverse longevities
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The relationship among oxidative stress, mitochondrial DNA integrity, and longevity continues to be without a general consensus. Here, we hypothesize that short- and long-lived birds, including the budgerigar (Melopsittacus undulatus), guineafowl (Numida meleagris), quail (Corturnix japonica), and turkey (Meleagris gallopavo) differ in oxidative stress measured by blood markers and that this difference correlates with mitochondrial genomic integrity both within and among species. In preliminary studies and to establish a reference and standard for the search for single nucleotide polymorphisms (SNPs), we used a combination of experimental and in silico tools for genome analysis to screen selected regions of the chicken (Gallus gallus) mitochondrial genome (mtGenome) for SNPs. A total of 113 SNPs was identified which formed 17 haplotypes. The length of the turkey mtGenome sequence developed was 16,967 bp in length, while that of the budgie was 18,193 bp. Annotation of both sequences revealed a total of 13 genes and 24 RNA (22 tRNA and 2 rRNA). Within the budgie mtGenome sequence, a duplicated control region was observed, and there was an additional nucleotide in the NADH dehydrogenase subunit 3 sequence of both the turkey and budgie. The total number of SNPs within the D-loop and 16S rRNA in each of the four species ranged from zero in the quail to 22 in the budgie. The new mtGenome sequences revealed that the turkey was most closely related to the chicken and quail, and the budgie was closest to kakabo (Strigops habroptilus). Oxidative stress, estimated by biomarkers thiobarbiturate acid reacting substance (TBARS), plasma uric acid (PUA), and glutathione (GSH) and at 10, 30, 55, and 80 wks-of-age within each species, was not consistent. The level of GSH was highest in guineafowl, but lowest in budgie. While PUA, an antioxidant, exhibited a significantly (P<0.05) decrease as birds grew order, TBARS, a lipid peroxidation index, increased with age. In general, oxidant and antioxidant status appeared to vary among species and to be significantly affected by age, unlike mutations in the mtDNA which remained the same in younger and older birds. This primary findings and discoveries of this dissertation research include the large scale SNP discovery in previously described and novel avian mtGenomes including the chicken and turkey, the two main poultry species, and the determination that oxidative stress in birds appears to vary with age but that this does not affect mitochondrial DNA variation. Recent evidence of work in mice appears to support results described in this dissertation that mitochondrial DNA mutations do not increase with age, the central paradigm of the â Free Radical Theory of Agingâ . The dissertation also described resources and data that will be a foundation for the use of birds, especially the budgie, as a model for testing this theory that remains of interest to both agricultural and biomedical sciences.
- Doctoral Dissertations