The three postblastoderm cell cycles of Drosophila embryogenesis are regulated in G2 by string.
The string (stg) locus of Drosophila encodes a factor that is thought to trigger mitosis by activating the p34cdc2 protein kinase. stg is required for mitosis early in development and is transcribed in a dynamic pattern that anticipates the pattern of embryonic cell divisions. Here we show that differential cell cycle regulation during postblastoderm development (cell cycles 14-16) occurs in G2. We demonstrate that stg mRNA expressed from a heat shock promotor triggers mitosis, and an associated S phase, in G2 cells during these cycles. Hence, differential cell cycle timing at this developmental stage is controlled by stg. Finally, we use heat-induced stg expression to alter the normal pattern of embryonic mitoses. Surprisingly, the complex mitotic pattern evident during normal development is not essential for many features of pattern formation or for viability.
Department of Biochemistry and Biophysics, University of California, San Francisco 94143.
B A
BA
Edgar
P H
PH
O'Farrell
D000818:Animals; D001756:Blastoderm / Q000166:cytology; D016203:CDC2 Protein Kinase; D002453:Cell Cycle; D002455:Cell Division; D015342:DNA Probes; D004330:Drosophila / Q000166:cytology / Q000196:embryology* / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology* / Q000502:physiology; D005246:Feedback; D006360:Heat-Shock Proteins / Q000235:genetics; D006358:Hot Temperature; D007399:Interphase; D008938:Mitosis; D009693:Nucleic Acid Hybridization; D010750:Phosphoproteins / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics
D015342:DNA Probes; D006360:Heat-Shock Proteins; D010750:Phosphoproteins; D011494:Protein Kinases; D016203:CDC2 Protein Kinase