EARLY TRANSCRIPTION IN CAENORHABDITIS-ELEGANS EMBRYOS

We have analysed early transcription in devitellinized, cultured embry os of the nematode Caenorhabditis elegans by two methods: measurement of [P-32]UTP uptake into TCA-precipitable material and autoradiographi c detection of [H-3]UTP labelling both in the presence and absence of a-amanitin. RNA synthesis was first detected at the 8- to 12-cell stag e, and alpha-amanitin sensitivity also appeared at this time, during t he cleavages establishing the major founder cell lineages. The require ments for maternally supplied versus embryonically produced gene produ cts in early embryogenesis were examined in the same culture system by observing the effects of alpha-amanitin on cell division and the earl y stereotyped lineage patterns. In the presence of high levels of alph a-amanitin added at varying times from two cells onward, cell division continued until approximately the 100-cell stage and then stopped dur ing a single round of cell division. The characteristic unequal early cleavages, orientation of cleavage planes and lineage-specific timing of early divisions were unaffected by alpha-amanitin in embryos up to 87 cells. These results indicate that embryonic transcription starts w ell before gastrulation in C. elegans embryos, but that although embry onic transcripts may have important early functions, maternal products can support at least the mechanics of the first 6 to 7 cell cycles.