Development and Protein Synthesis in Drosophila

CHAPTER 1 At various times during metamorphosis, brain tissue of D. melanogaster has been pulse-labeled in situ with 35S-Met. The composition of the newly synthesized stage-specific proteins and of the total bulk of Coomassie stained polypeptides present at the same time in the tissue, or the parts of it, were analyzed on SDS-polyacrylamide gels. The striking similarity and constancy of the obtained patterns, and the finding that most of the observed accumulating polypeptides are glycosalated, lead to the conclusion that the predominant change in the larval Drosophila brain is dendritic and/or axonal reorganization. CHAPTER II Pupae of Drosophila melanogaster were heat shocked under conditions required to induce phenocopies in more than 90% of the flies that subsequently emerge. The effects of these treatments on protein synthesis in two tissues (thoracic epithelium and brain) were followed for several hours after the heat treatments. Results from pulse labeling and protein separations on SDS acrylamide gels showed a virtually complete cessation of protein synthesis immediately after the shock followed by a non-coordinate resumption of the starting pattern. Similar experiments following double heat shocks demonstrated a more rapid resumption of synthesis of heat shock proteins after two successive heat treatments than after a single one. CHAPTER III We describe variants of three heat shock proteins of Drosophila melanogaster and the use of these to map the chromosome regions which contain the coding sequences for these proteins. All three map to a region on chromosome 3L which includes only one heat shock puff, that designated as 67B. The results imply that the genes which code for at least three heat shock proteins are included within the 67B region. CHAPTER IV Mild heat treatments applied to whole animals or cell cultures of Drosophila melanogaster prior to lethal heat shocks result in both survival and protection against phenocopy induction. From an examination of these heat shock effects on transcriptional and translational activities in tissues and cells it appears that the protective action of pretreatment is due to sequestering of mRNAs in a masked form as RNPs. Heat shock proteins are evidently involved in the masking process either directly or indirectly.