Adult fly population cages were maintained at 24 ̊C on a 24-hour light cycle (14 hours light/10 hours dark). After a 2hr pre-lay, embryos were collected on agar plates for a 2 hour interval during a light cycle and allowed to hatch. Larvae were allowed to feed until 42-44hr AEL, then frozen on dry ice.

Total RNA was primed for first strand cDNA synthesis using a random N15 primer in the presence of trehalose and sorbitol. The RNA/cDNA hybrid was purified, then capped RNA was biotinylated and purified using streptavidin beads. The first strand cDNA was ligated to another primer at the 5' end for second strand cDNA synthesis. The resulting double-stranded cDNA was cleaved using EcoP15I and a second linker was ligated to the 3' end of the ds-cDNA products. 5'-CAGE tags were purified by streptavidin then amplified by PCR.

The 9-nt barcode linker sequence was removed, and the 27-nt CAGE reads representing capped 5’ transcript ends were aligned to the D. melanogaster genome using StatMap (http://www.statmap-bio.org/).