Functional Characterization of a Drosophila Transgenic Line Expressing a Chimeric Flightin: Implications on Flight Muscle Structure and Mating Behavior
The asynchronous, indirect flight muscles (IFM) of Drosophila are characterized by their remarkable crystalline myofilament lattice structure that has been proposed to have evolved to power skilled flight for survival, and to produce male courtship song, a sexually selected pre-mating behavior for reproduction. It is not known how physiologically and genetically IFM generates two distinct behaviors under separate evolutionary schemes. Flightin, a 20kDa myofibrillar myosin-binding protein that in Drosophila is exclusively expressed in the IFM, is required for muscle structural integrity and flight. The flightin N-terminal sequence (~65 aa in D. melanogaster) is highly variable among Drosophila species, unlike the rest of the Drosophila protein. Using electron microscopy, fourier image analyses, flight and wing beat frequency tests, I explored the hypothesis that the sequence of amino acids in flightin’s N-terminal region has a strong influence on myofilament lattice spacing and crystallinity. This is investigated by the creation of two independent D.melanogaster transgenic fly lines expressing a D.virilis-D.melanogaster chimeric flightin, both of which exhibit larger myofillament lattice spacing compared to the full length transgenic and D.virilis control fly lines, along with an intermediate wing beat frequency and an equal and/or improved flight ability compared to the control full length transgenic line. These results suggest the N-terminal region is under evolutionary pressures to optimize crystalline lattice structure
