Effects of RNA inhibitors on the development of Drosophila embryos permeabilized by a new technique

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Abstract
The molecular analysis of Drosophila embryogenesis has been hindered by the impermeable nature of the vitelline membrane, which has made it difficult to introduce exogenous substances into the developing embryo. We have developed a modification of the permeabilization technique of Limbourg and Zalokar ('73) in which octane is used to permeabilize the vitelline membrane and dimethylsulfoxide is used to facilitate the transport of exogenous substance across the cell membranes. The procedure is highly effective (ca. 95%) and is consistent with a high frequency of normal development. We have used this technique to analyze the effect in vivo of four inhibitors of RNA synthesis (alphaamanitin, actinomycin‐D, rifampin, and rifamycin SV) on the embryogenesis of Drosophila. We have found that there are characteristic stage‐specific alternations in the sensitivity of the embryo to these inhibitors which is reflected both by changes in the ID50 dosages and by changes in the developmental abnormalities caused by the drugs. Embryos aged 2–12 hours old undergo a developmental arrest within 30 minutes after application of the inhibitors. Embryos older than 12 hours are able to develop for 140+ minutes after treatment before arresting. The effects of these drugs are consistent with the idea that there exists a definite sequential program of gene activity that is necessary to the normal embryonic development of Drosophila.