Post-transcriptional suppression of gene expression in Xenopus embryos by siRNA and long dsRNA. (A) Temporal expression of luciferase-coding RNA during early embryogenesis. In vitro transcribed RNA encoding GL3 luciferase (Luc mRNA, 2 ng) was microinjected into one blastomere of 2-cell stage embryos. Injected embryos were collected at different stages, lysed and assayed for luciferase activity. (B) Gene-specific inhibition of luciferase expression by siRNA and long dsRNA. Luciferase-coding RNA (Luc mRNA, 2 ng) and the indicated siRNAs (20 µM) or dsRNAs (0.2 µg/µl) were microinjected into embryos as in (A). The injection volume was 5 nl. Embryos were collected at stages 9 and 18. The average luciferase activity recovered from control embryos without siRNA or dsRNA was set as 100%. GL3 siRNA, siRNA targeting GL3 luciferase; GL2 siRNA, siRNA targeting the GL2 version of luciferase; mock siRNA, siRNA targeting irrelevant human but not Xenopus sequences; GL3 dsRNA, 1.7 kb dsRNA corresponding to full-length GL3 luciferase-coding sequences; mock dsRNA, 1 kb dsRNA corresponding to an irrelevant gene. All values represent the means of four groups of embryos and error bars indicate standard deviation from the mean. Experiments were repeated twice with similar results.