dsRNA was synthesized using the MEGAscript RNAi kit (Ambion) according to the manufacturer's instructions. The templates for dsRNA were prepared as previously described using gene-specific primers containing T7 polymerase sites911. All the primer sets are listed in Table S2. PCR was carried out as follows at 94°C for 3 min, 35 cycles of 94°C for 1 min, 59°C for 1 min, 72°C for 1 min, and a final elongation at 72°C for 10 min. The purified PCR product was used as template for in vitro dsRNA synthesis. The template DNA and single-stranded RNA were removed by DNase and RNase treatments followed by dsRNA purification using MEGAclearTM columns (Ambion). The synthesized dsRNA was then eluted in diethyl pyrocarbonate-treated nuclease-free water and the corresponding concentrations were measured using a biophotometer (Eppendorf). The dsRNA of enhanced green fluorescent protein (EGFP) was used as the negative control.