Dependence of the timing system regulating the onset of gastrulation on cytoplasmic, but not nuclear, activities in the Xenopus embryo |
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Authors: | Takagi Makoto Shimoda Taiki Shinagawa Atsunori |
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Institution: | Department of Biology, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-Machi, Yamagata 990-8560, Japan. |
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Abstract: | This study examines the properties of the timer that regulates the onset of gastrulation in the Xenopus embryo. Pre-gastrulation embryos were exposed to aphidicolin, vinblastine, 6-dimethylaminopurine (6-DMAP) or urethane. Embryos exposed to aphidicolin or vinblastine for 0.5-2 h before the presumptive onset of gastrulation, began gastrulation at the same time as control embryos. However, those exposed to 6-DMAP or urethane commenced gastrulation significantly later than controls. In 6-DMAP- and urethane-treated embryos, the onset of gastrulation was retarded by approximately 25% and 120%, respectively. 6-DMAP and urethane, but not vinblastine, also lowered the rate of nuclear doubling by 30% and 120%, respectively, in late-blastula to early-gastrula embryos. 6-DMAP and urethane also lowered the rate of cleavage and cleavage-relevant cytoplasmic cycling by 30% and 80%, respectively, in cleavage-stage embryos. We propose that cytoplasmic activities that can be retarded by 6-DMAP and urethane, but not aphidicolin or vinblastine, may be responsible for regulating the onset of gastrulation in Xenopus embryos. |
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Keywords: | 6-DMAP aphidicolin gastrulation timer urethane vinblastine Xenopus |
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