Protein Synthesis during Photocontrolled Progression of the Cell Cycle in Single‐celled Protonemata of the Fern Adiantum Capillus‐veneris

Abstract

Protein synthesis during photoinduced, synchronous progression of the cell cycle in singleeelled protonemata of the fern Adiantum capillus-veneris was studied by tracer techniques. Nuclei ofthe protonemata were labelled with 3H-thymidine during spore germination so that the amount of 'H incorporated into the TCA-insoluble fraction of the cells could be used as a measure of the cell number in each sample. The rate of the incorporation of 'T-amino acids into TCA-insoluble materials was not significantly varied at different stages of the cell cycle o r by treatment with blue light. Extracts of cells labelled with "S-methionine at various times after the transfer from red light condition (Go) to darkness ( G , to S) were analyzed by two-dimensional gel electrophoresis. At least 3 of about 200 spots showed significant changes in intensity on fluorograms. Spot A (molecular weight 20,000, isoelectric point 6.3) was detectable only in early G,, whereas spot B (molecular weight 19.500, isoelectric point 6.3) was found only in the late G , and S phases. When thecells were exposed to blue light before the dark incubation, the times of disappearance of spot A and appearance of spot B were advanced depending upon the progl;ession of the cell cycle but not upon the clock time.