An analysis of stage-specific protein synthesis in the early Drosophila embryo using high-resolution, two-dimensional gel electrophoresis

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An improved method of high-resolution, two-dimensional gel electrophoresis has been used to study the patterns of protein synthesis during embryonic development of Drosophila melanogaster. Small groups of synchronized embryos were radiolabeled directly by microinjection with [ 35S]methionine, and the patterns of synthesis of [ 35S]methionine-labeled proteins from 15 developmental stages between 1.5 and 18.5 hr post-fertilization evaluated. Over 1200 proteins were resolved, and changes in the temporal pattern of synthesis of many of these have been analyzed in the present study. Major qualitative and quantitative differences in the relative rates of synthesis of large numbers of proteins were found in the stages examined. These have been grouped into several different classes. In particular, one group consisted of proteins displaying a dramatic fall in levels of synthesis from preblastoderm through cellular blastoderm. Within this group, some proteins disappeared completely by gastrulation, whereas others underwent a phase of elevated synthesis at a later stage of development. A second group consisted of proteins that were found at all stages examined. All polypeptides in this group underwent a phase of elevated rate of synthesis post cellular blastoderm. A third group consisted of stage-specific proteins that were synthesized during a specific embryonic stage. Temporal changes in the relative rates of synthesis of many proteins were found to be clustered in a few limited periods of rapid change that occurred every 4 to 5 hr. In addition, subsets of proteins increasing during one such period were observed to decrease during a later period, indicating the possibility of some form of coordinate regulation. The time interval between a period of increase and decrease in rates of synthesis of many proteins was observed to occur every 9–10 hr.