Permeability barrier formation requires germline expression of fatty acid synthesis genes. Confocal images of control embryos and embryos in which the indicated components of the fatty acid biosynthesis pathway were inhibited by RNAi in either an rrf-1(+) (left) or rrf-1(pk1417) mutant background (right). Embryos expressing a GFP-tagged plasma membrane probe and mCherry::histone H2B (red) were placed in FM4-64 dye. All RNAi-treated embryos were permeable in the rrf-1(pk1417) background, indicating that germline expression of these genes is required. n = number of imaged embryos. Bars, 10 µm.