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Cycle cellulaire et polarisation du zygote Fucus régulations et interactions

Abstract : The correct orchestration of cell cycle and differentiation is required for the development of all organisms. In plants, there is little data on the molecular mechanisms involved in the coordination of both of these processes. The zygote of the brown alga Fucus is a model to study plant early embryogenesis. Polarisation of the Fucus zygote occurs after fertilization and is concomitant with the first mitotic cell cycle. Little is known about cell cycle, and altough molecular actors involved in polarization have been identified, transduction pathways controlling the establishment of polarity remain to be determined. In this context, we are interested in the regulation of cell cycle and polarisation, as well as, in interconnection between these two processes. We have demonstrated, that the first cell cycle of Fucus zygotes encompasses four well-defined phases G1, G2, S and M, and is under the tight control of cell-cycle dependent-kinase-related proteins (CDK). Usual functional checkpoints are found, ensuring that mitosis will not occur in the presence of incomplete DNA replication or of mitotic spindle defects. Two CDKs containing the hallmark PSTAIRE, p32 and p34, are translated from maternal mRNAs, after fertilization, and their progressive synthesis correlates with an increase in CDK activity until G2 phase, where the transcription of a positive regulator is further required to achieve CDK activation before mitosis. Both of these CDKs appear to be negatively regulated by tyrosine phosphorylation, during normal cell cycle progression and following activation of the DNA replication checkpoint. Since p34 is the major target of the CDK inhibitor purvalanol, it appears to play a major role in cell cycle control. We have also demonstrated that, at the G1/S transition, p34 controls the formation of the embryonic axis, which is achieved during S phase. On the other hand, we have shown that axis formation is essential for embryo patterning and is under the control of tyrosine-kinases-related proteins, whose inactivation delayed but do not hampered cell division. Thus, whereas axis formation is cell-cycle dependent, a putative control of the cell-cycle control by polarisation events remains to be shown.
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Submitted on : Wednesday, February 11, 2015 - 11:55:22 AM
Last modification on : Friday, January 21, 2022 - 3:28:48 AM
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  • HAL Id : tel-01115123, version 1


Florence Corellou. Cycle cellulaire et polarisation du zygote Fucus régulations et interactions. Biologie cellulaire. Rennes 1, 2000. Français. ⟨tel-01115123⟩



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