DISRUPTION OF MITOCHONDRIAL FUNCTION IN INTERPOPULATION HYBRIDS OF TIGRIOPUS CALIFORNICUS

• Published in: Evolution Vol. 60; no. 7; pp. 1382 - 1391
• Main Authors: Ellison, Christopher K, Burton, Ronald S
• Format: Journal Article
• Language: English
• Published: United States Society for the Study of Evolution 01.07.2006; Oxford University Press
• Subjects: Adaptation, Biological; Adenosine Triphosphate - metabolism; Assembly lines; Biological Evolution; Cell Nucleus - genetics; Citrate (si)-Synthase - metabolism; Citrates; Copepod; Copepoda; Copepoda - enzymology; Copepoda - genetics; Copepoda - metabolism; DNA-Directed RNA Polymerases - metabolism; Electron Transport; electron transport system; Enzymes; Genetics; Genotype; Hatching; hybrid breakdown; Hybridity; Hybridization; Hybridization, Genetic; Hypotheses; Inbreeding; intergenomic coadaptation; intrinsic post-zygotic isolation; Marine; Mitochondria; Mitochondria - enzymology; Mitochondria - genetics; Mitochondria - metabolism; Mitochondrial DNA; mitochondrial function; mitochondrial RNA polymerase; Nuclear cytoplasmic interactions; RNA; Species Specificity; Tigriopus californicus
• ISSN: 0014-3820; 1558-5646
• DOI: 10.1554/06-210.1

Electron transport system (ETS) function in mitochondria is essential for the aerobic production of energy. Because ETS function requires extensive interactions between mitochondrial and nuclear gene products, coadaptation between mitochondrial and nuclear genomes may evolve within populations. Hybridization between allopatric populations may then expose functional incompatibilities between genomes that have not coevolved. The intertidal copepod Tigriopus californicus has high levels of nucleotide divergence among populations at mitochondrial loci and suffers F2 hybrid breakdown in interpopulation hybrids. We hypothesize that hybridization results in incompatibilities among subunits in ETS enzyme complexes and that these incompatibilities result in diminished mitochondrial function and fitness. To test this hypothesis, we measured fitness, mitochondrial function, and ETS enzyme activity in inbred recombinant hybrid lines of Tigriopus californicus. We found that (1) both fitness and mitochondrial function are reduced in hybrid lines, (2) only those ETS enzymes with both nuclear and mitochondrial subunits show a loss of activity in hybrid lines, and (3) positive relationships exist between ETS enzyme activity and mitochondrial function and between mitochondrial function and fitness. We also present evidence that hybrid lines harboring mitochondrial DNA (mtDNA) and mitochondrial RNA polymerase (mtRPOL) from the same parental source population have higher fitness than those with mtDNA and mtRPOL from different populations, suggesting that mitochondrial gene regulation may play a role in disruption of mitochondrial performance and fitness of hybrids. These results suggest that disruption of coadaptation between nuclear and mitochondrial genes contributes to the phenomenon of hybrid breakdown.