Journal
MOLECULAR ECOLOGY
Volume 20, Issue 21, Pages 4503-4520Publisher
WILEY
DOI: 10.1111/j.1365-294X.2011.05290.x
Keywords
ecological genomics; microarray; mito-nuclear interactions; mtDNA phylogeography; oxygen availability
Funding
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, AED [AED-11-050]
- NIH [2R01GM067862]
- NSF [BES-0652006, EF-0723771]
- Experimental Program to Stimulate Competitive Research (EPSCoR) fellowship
- Office of Integrative Activities
- Office Of The Director [1004057] Funding Source: National Science Foundation
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The physiological link between oxygen availability and mitochondrial function is well established. However, whether or not fitness variation is associated with mitochondrial genotypes in the field remains a contested topic in evolutionary biology. In this study, we draw on a population of the teleost fish, Fundulus heteroclitus, where functionally distinct subspecies hybridize, likely as a result of past glacial events. We had two specific aims: (i) to determine the effect of mtDNA genotype on survivorship of male and female fish under hypoxic stress and (ii) to determine the effect of hypoxic stress, sex and mtDNA genotype on gene expression. We found an unexpected and highly significant effect of sex on survivorship under hypoxic conditions, but no significant effect of mtDNA genotype. Gene expression analyses revealed hundreds of transcripts differentially regulated by sex and hypoxia. Mitochondrial transcripts and other predicted pathways were among those influenced by hypoxic stress, and a transcript corresponding to the mtDNA control region was the most highly suppressed transcript under the conditions of hypoxia. An RT-PCR experiment on the control region was consistent with microarray results. Effects of mtDNA sequence variation on genome expression were limited; however, a potentially important epistasis between mtDNA sequence and expression of a nuclear-encoded mitochondrial translation protein was discovered. Overall, these results confirm that mitochondrial regulation is a major component of hypoxia tolerance and further suggest that purifying selection has been the predominant selective force on mitochondrial genomes in these two subspecies.
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