Patterns of proteins synthesized during development of Caenorhabditis elegans

Abstract

Two-dimensional gel electrophoresis has been used to analyze proteins synthesized during postembryonic development of the nematode Caenorhabditis elegans. This organism is favorable for these studies because it has a limited number of cells, it is genetically well-defined, and its development is currently under investigation in several laboratories. 35S-Labeled E. coli was used for continuous and pulse labeling of C. elegans during its four juvenile larval stages and as a gravid adult. After continuous labeling or pulse labeling for 1 hr, 600–800 individual spots can be resolved on a 2D gel using fluorography and 2 weeks of exposure. Proteins that represent 0.0017% of the total sample can be detected. Exposure for 12 weeks reveals only 100 additional spots even though the films are not saturated. It therefore appears that the frequency distribution of proteins decreases significantly beyond these 800 most abundant proteins that can be fractionated on an O'Farrell gel. When the patterns of pulse-labeled proteins of the five developmental stages were compared, 113 proteins could be seen to undergo modulation at one or more of the developmental stages. A maximum number of changes was seen in the transition from the L4 to the adult stages when 11% of the total spots either appeared, disappeared, or changed in intensity. As controls, different preparations of the same developmental stage were compared and revealed considerable fluctuation, 2.6–4.8%. These fluctuations are presumed to be due to variations in growth conditions during culture of the organism. Continuous label experiments reveal a distinct set of proteins that undergo turnover and/or modification during development. Some of these proteins are absent in only one stage, indicating that stable proteins are also modulated. But nearly all of the proteins seen in a continuous label are also seen in a pulse label indicating that most of the major proteins are always present and always synthesized.