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Abstract

Mutations of the maternal effect locus pelle (pll) cause dorsalized Drosophila embryos. In extreme mutants, the embryo develops into a long hollow tube of dorsal cuticular structures with no sign of ventral pattern elements. Injection of wild-type cytoplasm or poly(A)+RNA into mutant pll embryos partially restores the normal pattern. Rescuing activity is present in the wild-type cytoplasm until the late blastoderm stage, but is already absent from the poly(A)+RNA fraction by the time of pole cell formation. At the same time, pll embryos fail to respond to injected biologically active poly(A)+RNA. This indicates that pll+ mRNA is lost early from the pool of maternal RNA and that there is a non-RNA component of rescue. This component, most likely the pll+ protein, appears to be unequally distributed in wild-type embryos.