Interphase-ArrestedDrosophilaEmbryos Initiate Mid-Blastula Transition At A Low Nuclear-Cytoplasmic Ratio [article]

Isaac Strong, Kai Yuan, Patrick H. O'Farrell
2017 bioRxiv   pre-print
Externally deposited eggs begin development with an immense cytoplasm and a single overwhelmed nucleus. Rapid mitotic cycles restore normality as the ratio of nuclei to cytoplasm (N/C) increases. At the 14th cell cycle inDrosophilaembryos, the cell cycle slows, transcription increases, and morphogenesis begins at the Mid-Blastula Transition (MBT). To explore the role of N/C in MBT timing, we blocked N/C-increase by downregulating cyclin/Cdk1 to arrest early cell cycles. Embryos arrested in cell
more » ... cycle 12 cellularized, initiated gastrulation movements and activated transcription of genes previously described as N/C dependent. Thus, occurrence of these events is not directly coupled to N/C-increase. However, N/C might act indirectly. Increasing N/C promotes cyclin/Cdk1 downregulation which otherwise inhibits many MBT events. By experimentally inducing downregulation of cyclin/Cdk1, we bypassed this input of N/C-increase. We describe a regulatory cascade wherein the increasing N/C downregulates cyclin/Cdk1 to promote increasing transcription and the MBT.
doi:10.1101/143719 fatcat:2nrh7bohm5el3btjl5d563uyue