Protein synthesis during Ilyanassa development: effect of the polar lobe.

Removal of the polar lobe at the trefoil stage of the first cleavage division of Ilyanassa embryos causes abnormalities much later in development. To determine if the developmental differences between normal and delobed embryos were reflected in alterations in protein synthesis and at what stages of development these become evident, protein solutions were separated by disc electrophoresis on basic acrylamide gels. For the analysis of the newly synthesized proteins, two protein samples, one labelled with C and the other with H, were combined in the same electrophoretic column. Each was prepared from normal embryos or Iobeless embryos at different stages of development. The distribution of the two groups of differentially labelled proteins was compared by a determination, for each fraction, of the ratio of the normalized H/C counts for that particular fraction (R — H/C). The plot of R versus fraction number was studied for various combinations of samples. During normal development the profile of labelled proteins remains unchanged until the onset of visible differentiation. At this stage, around day 4 of development, there are changes in biosynthesis revealed by a greater emphasis on the synthesis of slow moving proteins. The profile of labelled proteins of Iobeless embryos remains unchanged up to the 5th day of development. This result is correlated with the absence, in the Iobeless embryos, of many of the visible differentiations. Preliminary studies revealed that the spectrum of labelled proteins of the polar lobe is identical to the one present in Iobeless embryos and in normal embryos in early stages of development. This suggests the possibility that the morphogenetic factors associated with the polar lobe are not among the newly synthesized proteins. A hypothesis is presented to account for the effects on morphogenesis and protein synthesis which are produced by removal of the polar lobe.