Proteins in the mitochondrial electron transport chain are composed of both nuclear and mitochondrially encoded subunits that must tightly interact. In Drosophila, over one fifth of the nuclear encoded subunits have a second copy that is only expressed in the testes. This study aims to dissect the functional differences of one such duplicate gene, cytochrome-c proximal and cytochrome-c distal. The experiments proposed to test this are as follows. 1) Measure fitness correlates of transgenic flies expressing either testis or somatic cytochrome c in both the soma and testes. For somatic function the traits of lifespan, fecundity, and larval viability will be measured. For testis function the traits of sperm viability, sperm count and sperm competitive ability will be measured. 2) Test for coadaptation of tissue specific enzyme complexes by quantifying enzymatic activity of tissue specific cytochrome c oxidase when oxidizing either testis or somatic cytochrome c.
This study integrates 1) reproductive evolution, by measuring reproductive fitness traits in a previously uninvestigated class of reproductive proteins, 2) evolution of coadaptation, by testing the functional disruption induced by forcing non-coadapted molecules to interact and 3) evolution of gene duplication and subfunctionalization, by measuring functional divergence of two gene copies. As such, findings will prove informative to a broad range of researchers and will provide tight connections between otherwise loosely affiliated fields.
