Sexual Conflict, Ageing, and the Evolution of Cytonuclear Interaction.

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Mitochondria (mt) - the "power plants" of animal and other eukaryotic cells - possess their own DNA and, paradoxically, sometimes evolve in ways that are unfavourable to their hosts. Mitochondrial diseases, such as the neurodegenerative condition we call Alzheimer's disease are one result, but many other pathologies, including ageing itself, may be related to dysfunctional evolution of mt. Because mt are passed down through the egg, even defects hobbling male-specific functions can escape natural selection. Sperm are particularly affected by mutations in mtDNA because most animal sperm require high mt output to function; in men mt defects are a very common cause of infertility. But such high output mt may compromise the survival of the egg and body, creating an evolved conflict between male and female. For males to influence mt function requires intervention by genes in the nucleus, and so a complex, coevolved, and conflicted relationship between the sexes and mt exists. Proposed research makes use of a unique model system in the fruit fly, Drosophila, in which over 1000 generations of evolution for extremely fast and slow life-cycles has produced a complex of 16 radically different populations with respect to development, reproduction and ageing. Trading mt between these treatments has a strong effect on male, but not female, fertility and ageing, consistent with the mt-nucleus sexual conflict hypothesis. These effects can be visualized using new techniques in genetics and microscopy, in which sperm heads are genetically-engineered to fluoresce -- red or green -- and animals can be studied across their entire life span as a microcosm for ageing research. Here we have an unparalleled opportunity to deepen our understanding of genetic processes related fertility and senescence in one of the premiere model systems in biology.