All embryos used in this study were from wild-type Drosophila
flies (Canton S). Embryos were collected at 2 h intervals and aged
until the desired developmental stage on yeast juice agar plates
at 25 C. The 0–2-hr embryos and 3–5-hr embryos were dechorionated with 5% sodium hypochlorite in water for 1.5 min and then
frozen in liquid nitrogen. After 500 ll of TRIzol Reagent (Invitrogen) was added to the frozen embryos on ice, the embryos were
homogenized quickly, and 500 ll TRIzol Reagent and 200 ll chloroform/isoamyl alcohol (49/1, v/v) were added, followed by vigorous shaking. After incubation on ice for 5 min, the suspension was
centrifuged at 12,000 rpm at 4 C for 15 min. RNA in the aqueous
phase was transferred to a sterilized tube. After addition of
500 ll of isopropanol to the tube, the solution was stored on ice
for 5 min followed by centrifugation at 12,000 rpm at 4 C for
10 min. Isopropanol was exchanged with 75% aq ethanol and the
ethanol solution was centrifuged at 7500 rpm at 4 C for 3 min
three times. The precipitate, RNA, was suspended in 75% aq ethanol
and stored at 20 C for more than 12 h. The RNA suspension was
collected by centrifugation and dissolved in PBS buffer, followed by
treatment with an oligo (dT)-cellulose column (GE Healthcare)