Inhibition by cerulenin of RNA and lipid synthesis in Limnaea (mollusc) embryos

Cerulenin, a new antibiotic known to inhibit lipid synthesis in yeast, fungi and bacterial systems, has been tested with Limnaea embryos. In the presence of 40--50 microgram/ml cerulenin, lipid synthesis is inhibited by about 65% while RNA synthesis is inhibited by about 35% as is evident from the incorporation of 14C-acetate and 14C-uracil, respectively. In embryos treated with cerulenin, washed and returned to normal medium to which 14C-uracil was added, RNA synthesis continued normally. Such pretreatment with actinomycin, however, inhibits lipid synthesis by about 50%. Cerulenin treatment of eggs at the early morula or uncleaved stage for 30 min leads to a marked abnormality at the late veliger stage, and the embryos die before hatching. These results have been discussed in comparison with the known effects of actinomycin. As, unlike actinomycin, cerulenin has no delayed action, the present experiment offers a system for exploring the delayed effects of early transcription.