The translocation of mitochondria along insect ovarian microtubules from isolated nutritive tubes: a simple reactivated model.

Nutritive tubes, the microtubule-based translocation channels that link the trophic tissue to the developing oocytes in the ovaries of hemipteran insects, have been isolated and examined using video-enhanced differential interference contrast microscopy. When viewed in this way the nutritive tubes are seen to fray into linear strands, which, on the addition of exogenous ATP, support the translocation of particles along their lengths. The movement is also seen with GTP but not AMP-PNP. It is not affected by the addition of inhibitors of dynein or of energy metabolism. Electron microscopy shows the strands to consist of bundles of parallel microtubules of different sizes and the moving particles to be mitochondria. Comparisons are drawn between the movement of mitochondria along isolated insect ovarian microtubules and the reported translocation of vesicles along microtubules from squid axoplasm. The simplicity of the insect system is emphasized. The fact that it can be isolated easily and characterized biochemically makes it potentially valuable for investigating microtubule-based translocation.