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Ca2+ signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus

Ca2+ signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus
Ca2+ signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus
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.

1477-9129
2173-2181
Bothwell, J.H.F.
148883cc-1cd8-4e05-bb99-e80ce7a3cebb
Kisielewska, J.
44095bfd-ecde-4171-b28d-a2220db72d0a
Genner, M.J.
bfd02462-1b20-4396-91f0-3b1849c92d48
McAinsh, M.R.
c8d0162b-004b-4a96-8356-27ada291cb9f
Brownlee, C.
2af37c1c-b2bf-4832-8370-d9c35e7b3385
Bothwell, J.H.F.
148883cc-1cd8-4e05-bb99-e80ce7a3cebb
Kisielewska, J.
44095bfd-ecde-4171-b28d-a2220db72d0a
Genner, M.J.
bfd02462-1b20-4396-91f0-3b1849c92d48
McAinsh, M.R.
c8d0162b-004b-4a96-8356-27ada291cb9f
Brownlee, C.
2af37c1c-b2bf-4832-8370-d9c35e7b3385

Bothwell, J.H.F., Kisielewska, J., Genner, M.J., McAinsh, M.R. and Brownlee, C. (2008) Ca2+ signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus. Development, 135 (12), 2173-2181. (doi:10.1242/dev.017558).

Record type: Article

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.

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Published date: 15 June 2008
Organisations: Ocean and Earth Science

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Local EPrints ID: 340278
URI: https://eprints.soton.ac.uk/id/eprint/340278
ISSN: 1477-9129
PURE UUID: b73eec37-0104-4f3c-9831-1ee77c27c996

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Date deposited: 18 Jun 2012 14:03
Last modified: 30 Jul 2019 18:55

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