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Ca2+ signals co-ordinate zygotic polarization and cell cycle progression in the brown alga, Fucus serratus.

Bothwell, John H. F. and Kisielewska, Jolanta and Genner, Martin J. and McAinsh, Martin R. and Brownlee, Colin (2008) Ca2+ signals co-ordinate zygotic polarization and cell cycle progression in the brown alga, Fucus serratus. Development, 135 (12). pp. 2173-2181. ISSN 1477-9129

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    Abstract

    Zygotes of the fucoid brown algae provide excellent models for addressing fundamental questions about zygotic symmetry breaking. Although the acquisition of polarity is tightly coordinated with the timing and orientation of the first asymmetric division-with zygotes having to pass through a G1/S-phase checkpoint before the polarization axis can be fixed-the mechanisms behind the interdependence of polarization and cell cycle progression remain unclear. In this study, we combine in vivo Ca2+ imaging, single cell monitoring of S-phase progression and multivariate analysis of high-throughput intracellular Ca2+ buffer loading to demonstrate that Ca2+ signals coordinate polarization and cell cycle progression in the Fucus serratus zygote. Consistent with earlier studies on this organism, and in contrast to animal models, we observe no fast Ca2+ wave following fertilization. Rather, we show distinct slow localized Ca2+ elevations associated with both fertilization and S-phase progression, and we show that both S-phase and zygotic polarization are dependent on pre-S-phase Ca2+ increases. Surprisingly, this Ca2+ requirement cannot be explained by co-dependence on a single G1/S-phase checkpoint, as S phase and zygotic polarization are differentially sensitive to pre-S-phase Ca2+ elevations and can be uncoupled. Furthermore, subsequent cell cycle progression through M phase is independent of localized actin polymerization and zygotic polarization. This absence of a morphogenesis checkpoint, together with the observed Ca2+-dependences of S phase and polarization, show that the regulation of zygotic division in the brown algae differs from that in other eukaryotic model systems, such as yeast and Drosophila.

    Item Type: Article
    Journal or Publication Title: Development
    Uncontrolled Keywords: Ca2+ ; Cell cycle ; Fucus serratus ; PCNA ; Polarization ; Zygote
    Subjects: Q Science > QH Natural history > QH301 Biology
    Departments:
    ID Code: 26843
    Deposited By: Dr Martin R McAinsh
    Deposited On: 31 Jul 2009 09:00
    Refereed?: Yes
    Published?: Published
    Last Modified: 23 Jul 2014 14:48
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/26843

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