Nuclear transcription in preblastoderm Drosophila embryos

Drosophila preblastoderm (0 - 2.5 hr post-oviposition) embryos incorporate [32P] phosphate into newly synthesized RNA. A fraction of this RNA can be ascribed to nuclear transcription by virtue of its hybridization to nuclear DNA. This confirms the electron microscopic observation of McKnight and Miller (1) that nuclear transcription takes place at a low level in preblastoderm embryos. These nuclear transcripts are relatively small (7 - 12S), poly A(+) and appear on polysomes. Translation of newly synthesized nuclear transcripts during preblastoderm indicates that a zygotic genome contribution to embryonic phenotype may occur earlier in development than previously thought.