Oögenesis defects in the ecd-1 mutant of Drosophila melanogaster, deficient in ecdysteroid at high temperature

Oögenesis defects observed in ecd-1 females depend on the stage at which the shift from the permissive temperature (20°C) to the non-permissive temperature (28.5°C) is performed. Pupae shifting earlier than 48 hours after puparium formation have underdeveloped ovaries and die at emergence. In ecd-1 females shifted 2 days or more after puparium formation, egg chambers develop normally up to the early vitellogenic stage, and then degenerate—no mature oöcytes are formed. When the shift is performed after maturation of the females at 20°C, their egg-laying rate decreases slowly after the shift; the eggs display abnormal chorions and fail to develop into larvae. By shifting the ecd-1 females back to 20°C, a complete reversal of abnormalities of eggshell formation and egg development may be observed. The temperature-sensitive periods related to these different defects were determined. For egg development, the period extends from 2 days to 1 day before laying. For eggshell formation, the beginning and end of the temperature-sensitive period were not separated—both were located around 24 hours before laying. For the block of vitellogenesis, we concluded that this is probably due to an inhibition of yolk uptake. This inhibition would be effective only in follicles younger than the previtellogenic stage 7 when submitted to the non-permissive temperature.