Synthesis of nuclear and cytoplasmic proteins was studied biochemically and autoradiographically in early loach (Misgurnus fossilis) and sea-urchin (Strongylocentrotus nudus) embryos.
After incubation with [14C]amino acids for 5–120 min the ratio of the specific activities of nuclear, mitochondrial and 12000 g supernatant proteins was shown to be equal approximately to 6:1:2 in loach embryos and to 8:4:3 in sea-urchin embryos independently of the duration of labelling.
After incubation with [3H]amino acids the number of silver grains per unit section was on the average 2·4 times higher for nuclei than it was for cytoplasm at mid-blastula and mid-gastrula stages. At the mid-gastrula the vegeto-animal gradient of protein synthesis was found.
A higher level of the synthesis of nuclear proteins as compared with that of cytoplasmic proteins appears to be related to an increase in the nuclear volume and the nucleo-cytoplasmic ratio during the early development of the loach and sea-urchin embryos.
Select microRNAs are essential for early development in the sea urchin