When genetically divergent populations interbreed, first generation (F1) hybrids may show high productivity (hybrid vigor), but subsequent hybrid generations (F2 and beyond) frequently show a loss of productivity and fitness (hybrid breakdown). Hybrid breakdown is due to negative interactions among genes that have diverged between the populations, but which genes? The proposed investigations use the marine copepod, Tigriopus californicus, as a model system and focus on the interactions between mitochondrial genes (those located in the small, maternally-inherited mtDNA) and those located in the nuclear genome. The enzyme complexes that produce most cellular energy are mixes of components from both sources, so negative interactions may impact energy production and fitness. The role of these specific interactions on hybrid breakdown will be assessed by comparing mitochondrial gene expression, enzyme activities and energy production in natural populations and interpopulation hybrids.
Nuclear/mitochondrial gene interactions are of broad interest throughout biological sciences. Understanding how sequence variation in mtDNA leads to changes in mitochondrial function may shed new light on issues ranging from intraspecific physiological variation and human mitochondrial disease to success rates of nuclear-transplant cloning experiments. In addition to these broader scientific applications, the proposed work (and the experimental methods employed in the research) will serve as starting points for diverse outreach activities including public lectures, university curriculum development in molecular ecology, and development of K-12 laboratory activities implemented by a not-for-profit environmental education organization.