Further Investigations on Transcription and Translation in Limnaea Embryos

Abstract

14C-amino acid incorporation in uncleaved Limnaea eggs is slight but it slowly increases up to the trochophore stage followed by a rapid rise during the veliger stage when 32P incorporation is falling. There is a peak in the 10 S region of the sucrose density gradient profile of morula RNA. Presumably this morula RNA (messenger RNA) is necessary for final development and hatching of the veliger. The trochophore 10 S peak is the largest, stable and strongly depressed by actinomycin; on the contrary, the veliger 10 S RNA peak is insensitive to actinomycin and seems to be meant for immediate translation.Actinomycin treatment of the uncleaved eggs prevents cleavage in a certain percentage of eggs but in the rest the treatment is not effective until the trochophore stage.