Injection of Drosophila Embryos.

Injections into Drosophila embryos were performed as described previously, with modifications (33). Embryos were collected for 30 min, lined up for injections, and desiccated for 9 min in a closed chamber with Drierite. After injection, the embryos were incubated in a humidified chamber for 45 min and moved to a test tube and the tubes were stored on dry ice. For targeting and nontargeting SNAs, siRNA targeting the bicoid or luciferase mRNAs were used, respectively (SI Appendix, Table S1). Each biological replicate contained 15 embryos. The genotypes for the embryos are listed in SI Appendix.