Gene Expression during the Egg Development of Drosophila melanogaster.

Despite the importance of egg development to the female life cycle in Drosophila, global patterns of gene expression have not been examined in detail primarily due to the difficulty of synchronizing developmental stages. Entry into vitellogenesis is however an key stage of oogenesis, and by delaying entry past this control point, we have been able to investigate some of the transcriptional dynamics apparent before and after early egg formation over a 72 hour period. A short-day photoperiod (10:14 light:dark photoperiod) and moderate temperatures (11°C) are required for the induction of ovarian diapause. For our microarray experiments, 0-4 hours post-eclosion females were immediately introduced to the restrictive environmental conditions. Females were subsequently collected for RNA extraction after 5-7 days, or were alternatively re-introduced to normal environmental conditions to continue egg development. Time-points were collected before and after the release of reproductive arrest at 24 hour intervals and hybridized in a balanced loop design, including dye-swaps. Eight biological replicates were subsequently performed for each treatment, including 3 day old male and female controls maintained under normal environmental conditions.