Analysis of RDE-4 maternal effects.

RDE-4 maternal effects are fully penetrant and expressive. Progeny animals from crosses depicted in Figure 4A were scored in each generation for RNAi activity (seeMaterials and Methods). Results from three different crosses are depicted. Three experiments were conducted at 22°C. The maternal effects were not altered by growth temperature. rde-4/+ F1 heterozygotes displayed wild-type RNAi activity, as expected. All of the F2 animals, including rde-4/rde-4 homozygotes, displayed wild-type RNAi activity due to RDE-4 maternal effects. Some of the F2 progeny were chosen at random, isolated, allowed to produce F3 progeny, and subsequently genotyped by DNA sequencing. Those F2 progeny that were homozygous for rde-4 produced F3 progeny that were RNAi- at 100% penetrance and expressivity; those F2 progeny that were heterozygous or wild type produced F3 progeny that were RNAi+ at 100% penetrance and expressivity, which is in keeping with a strong RDE-4 maternal effect. The ratio of wild-type to homozygous rde-4 F2 animals was approximately 3∶1, as predicted, and this is reflected in the RNAi activity of the F3s as well. Similar results were observed for both rde-4(ne299) and rde-4(ne309) alleles.