mt:CoIR301S mutants exhibit a wild range of defects, including growth retardation, neurodegeneration, muscular atrophy, male sterility, and reduced life span. The mutant has an extended larval phase (about 10 days at 25[o]C), and the mechanosensory bristles on the thorax are missing or thinned and shortened. Female flies are fertile but produce only 20% as many progeny as wild-type.
mt:CoIR301S flies exhibit about half the normal cytochrome c oxidase activity and significantly reduced ATP levels.
Young mt:CoIR301S mutant flies exhibit a full complement of ommatidia components, although some rhabdomeres have slight morphogenetic defects. However, the ommatidia of aged mt:CoIR301S, but not wild-type flies, are disorganized and the rhabdomeres are shrunken or completely lost, indicating age-dependent degeneration of photoreceptor neurons.
Transmission electron microscopy of flight muscle in wild-type and young mt:CoIR301S flies reveals orderly muscle fibers and fused mitochondria with long and tubular cristae. However, two weeks after adult eclosion, the mt:CoIR301S mitochondria are small and fragmented, containing many vesicular structures, and do not completely fill the intermyofibril space.
When tested in a climbing assay, mt:CoIR301S flies show mobility defects enhanced by age, consistent with age-dependent neurodegeneration and myopathy. Beyond these age-dependent neurological and muscular dysfunctions, mt:CoIR301S flies have substantially reduced longevity.