Both cyclin B levels and DNA-replication checkpoint control the early embryonic mitoses in Drosophila.
The earliest embryonic mitoses in Drosophila, as in other animals except mammals, are viewed as synchronous and of equal duration. However, we observed that total cell-cycle length steadily increases after cycle 7, solely owing to the extension of interphase. Between cycle 7 and cycle 10, this extension is DNA-replication checkpoint independent, but correlates with the onset of Cyclin B oscillation. In addition, nuclei in the middle of embryos have longer metaphase and shorter anaphase than nuclei at the two polar regions. Interestingly, sister chromatids move faster in anaphase in the middle than the posterior region. These regional differences correlate with local differences in Cyclin B concentration. After cycle 10, interphase and total cycle duration of nuclei in the middle of the embryo are longer than at the poles. Because interphase also extends in checkpoint mutant (grapes) embryo after cycle 10, although less dramatic than wild-type embryos, interphase extension after cycle 10 is probably controlled by both Cyclin B limitation and the DNA-replication checkpoint.
Ji
Jun-Yuan
JY
Department of Biology, University of Washington, Seattle, WA 98195-1800, USA.
Squirrell
Jayne M
JM
Schubiger
Gerold
G
D000818:Animals; D030801:Animals, Genetically Modified; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle; D002842:Chromatids / Q000502:physiology; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D017344:Genes, Insect; D049452:Green Fluorescent Proteins; D006657:Histones / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008938:Mitosis; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
C503698:CycB protein, Drosophila; D019926:Cyclin B; D029721:Drosophila Proteins; D006657:Histones; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D016203:CDC2 Protein Kinase