Elongation of Sperm Promoted by Giant Mitochondria in Drosophila
Abstract: Across species, to out-do competitors, during sperm competition between sperm from multiple males to fertilize limited number of eggs, great variations in sperm morphology have evolved. Sperm tail of Drosophilidae elongate up to 6 cm as a result of sexual selection for longer sperm by female. Sperm elongation takes place post meiotically and can proceed in the absence of an axoneme. We used primary cultures of spermatids of D. melanogaster to demonstrate that sperm elongation is driven by interdependent extension of giant mitochondria and cytoplasmic microtubules that is organized around the mitochondrial surface. Defects in sperm elongation in mutants of Milton-dMiro complex, a linker for mitochondria and microtubule motor Kinesin, suggests mitochondria-microtubule interaction is essential for the elongation. It is demonstrated that, in addition to the function as energy source, mitochondria can serve as internal skeleton for shaping sperm morphology.
Key words: spermatogenesis, mitochondria, microtubule, bio-diversity