@article {ben-joseph_crystallization_2023,
	title = {Crystallization of Coccolith Calcite at Different Life-Cycle Phases Exhibits Distinct Degrees of Cellular Confinement},
	journal = {Small Structures},
	volume = {n/a},
	number = {n/a},
	year = {2023},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/sstr.202200353},
	pages = {2200353},
	abstract = {Coccolithophores are a group of unicellular marine algae that shape global geochemical cycles via the production of calcium carbonate crystals. Interestingly, different life-cycle phases of the same coccolithophore species produce very different calcitic scales, called coccoliths. In the widely studied diploid phase, the crystals have anisotropic and complex morphologies, while haploid cells produce coccoliths consisting solely of calcite crystals with simple rhombohedral morphology. Understanding how these two life-cycle phases control crystallization is a highly sought-after goal, yet, haploid phase crystallization has rarely been studied, and the process by which they form is unknown. Herein, advanced electron microscopy is employed to elucidate the cellular architecture of the calcification process in haploid cells. The results show that in contrast to diploid-phase calcification, the coccolith-forming vesicle of haploid-phase cells is voluminous. In this solution-like environment, the crystals nucleate and grow asynchronously in a process that resembles calcite growth in bulk solution, leading to the simple morphologies of the crystals. The two distinct mineralization regimes of coccolithophore life-cycle phases suggest that cellular architecture, and specifically confinement of the crystallization process, is a pivotal determinant of biomineral morphology and assembly.},
	keywords = {biomineralization, calcites, Coccoliths, crystal growths, haploid{\textendash}diploid life cycles, RCC1181, RCC3777},
	issn = {2688-4062},
	doi = {10.1002/sstr.202200353},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/sstr.202200353},
	author = {Ben-Joseph, Oz and de Haan, Diede and Rechav, Katya and Shimoni, Eyal and Levin-Zaidman, Smadar and Langer, Gerald and Probert, Ian and Wheeler, Glen L. and Gal, Assaf}
}
@article {langer_role_2021,
	title = {Role of silicon in the development of complex crystal shapes in coccolithophores},
	journal = {New Phytologist},
	volume = {231},
	number = {5},
	year = {2021},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.17230},
	pages = {1845{\textendash}1857},
	abstract = {The development of calcification by the coccolithophores had a profound impact on ocean carbon cycling, but the evolutionary steps leading to the formation of these complex biomineralized structures are not clear. Heterococcoliths consisting of intricately shaped calcite crystals are formed intracellularly by the diploid life cycle phase. Holococcoliths consisting of simple rhombic crystals can be produced by the haploid life cycle stage but are thought to be formed extracellularly, representing an independent evolutionary origin of calcification. We use advanced microscopy techniques to determine the nature of coccolith formation and complex crystal formation in coccolithophore life cycle stages. We find that holococcoliths are formed in intracellular compartments in a similar manner to heterococcoliths. However, we show that silicon is not required for holococcolith formation and that the requirement for silicon in certain coccolithophore species relates specifically to the process of crystal morphogenesis in heterococcoliths. We therefore propose an evolutionary scheme in which the lower complexity holococcoliths represent an ancestral form of calcification in coccolithophores. The subsequent recruitment of a silicon-dependent mechanism for crystal morphogenesis in the diploid life cycle stage led to the emergence of the intricately shaped heterococcoliths, enabling the formation of the elaborate coccospheres that underpin the ecological success of coccolithophores.},
	keywords = {biomineralization, Calcification, coccolith, coccolithophore, evolution, rcc, RCC1178, RCC1181, RCC1456, RCC1460, RCC1461, RCC1477, RCC1800, RCC1801, RCC3777, RCC6506, silicon},
	issn = {1469-8137},
	doi = {10.1111/nph.17230},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.17230},
	author = {Langer, Gerald and Taylor, Alison R. and Walker, Charlotte E. and Meyer, Erin M. and Ben Joseph, Oz and Gal, Assaf and Harper, Glenn M. and Probert, Ian and Brownlee, Colin and Wheeler, Glen L.}
}
@article {Meyer2020,
	title = {Sr in coccoliths of Scyphosphaera apsteinii: Partitioning behavior and role in coccolith morphogenesis},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {285},
	year = {2020},
	note = {Publisher: Elsevier Ltd tex.mendeley-tags: RCC1456},
	month = {sep},
	pages = {41{\textendash}54},
	abstract = {Coccolithophores are important contributors to global calcium carbonate through their species-specific production of calcite coccoliths. Nannofossil coccolith calcite remains an important tool for paleoreconstructions through geochemical analysis of isotopic and trace element incorporation including Sr, which is a potential indicator of past surface ocean temperature and productivity. Scyphosphaera apsteinii (Zygodiscales) exhibits an unusually high Sr/Ca ratio and correspondingly high partitioning coefficient (DSr = 2.5) in their two morphologically distinct types of coccoliths: flat muroliths and barrel-like lopadoliths. Whether or not this reflects mechanistic differences in calcification compared to other coccolithophores is unknown. We therefore examined the possible role of Sr in S. apsteinii calcification by growing cells in deplete (0.33 mmol/mol Sr/Ca), ambient (9 mmol/mol Sr/Ca), and higher than ambient Sr conditions (36 and 72 mmol/mol Sr/Ca). The effects on growth, quantum efficiency of photosystem II (Fv/Fm), coccolith morphology, and calcite DSr were evaluated. No effect on S. apsteinii growth rate or Fv/Fm was observed when cells were grown in Sr/Ca between 0.33{\textendash}36 mmol/mol. However, at 72 mmol/mol Sr/Ca growth rate was significantly reduced, although Fv/Fm was unaffected. Reducing the Sr/Ca from ambient (9 mmol/mol) did not significantly alter the frequency of malformed and aberrant muroliths and lopadoliths, but at higher than ambient Sr/Ca conditions coccolith morphology was significantly disrupted. This implies that Sr is not a critical determining factor in normal coccolith calcite morphology in this dimorphic species. Using energy dispersive spectroscopy (EDS) we observed an increase in [Sr] and decrease in DSr of coccoliths as the Sr/Ca of the growth medium increased. Interestingly, muroliths had significantly lower Sr/Ca than lopadoliths at ambient and elevated [Sr], and lopadolith tips had lower Sr than bases in ambient conditions. In summary, the Sr fractionation behavior of S. apsteinii is distinct from other coccolithophores because of an unusually high DSr and inter- and intra-coccolith variability in Sr/Ca. These observations could be explained by mechanistic differences in the selectivity of the Ca2+ transport pathway or in the Sr-and Ca-binding capacity of organic components, such as polysaccharides associated with coccolithogenesis.},
	keywords = {biomineralization, Calcification, coccolith, coccolithophore, Energy dispersive spectroscopy, Fractionation, RCC1456, Sr/Ca, Strontium, Trace element},
	issn = {00167037},
	doi = {10.1016/j.gca.2020.06.023},
	author = {Meyer, Erin M. and Langer, Gerald and Brownlee, Colin and Wheeler, Glen L. and Taylor, Alison R.}
}
@article {Helliwell2019,
	title = {Alternative mechanisms for fast na + /ca 2+ signaling in eukaryotes via a novel class of single-domain voltage-gated channels},
	journal = {Current Biology},
	volume = {29},
	number = {9},
	year = {2019},
	note = {tex.mendeley-tags: RCC299},
	pages = {1503{\textendash}1511.e6},
	abstract = {Rapid Na + /Ca 2+ -based action potentials govern essential cellular functions in eukaryotes, from the motile responses of unicellular protists, such as Paramecium [1, 2], to complex animal neuromuscular activity [3]. A key innovation underpinning this fundamental signaling process has been the evolution of four-domain voltage-gated Na + /Ca 2+ channels (4D-Ca v s/Na v s). These channels are widely distributed across eukaryote diversity [4], albeit several eukaryotes, including land plants and fungi, have lost voltage-sensitive 4D-Ca v /Na v s [5{\textendash}7]. Because these lineages appear to lack rapid Na + /Ca 2+ -based action potentials, 4D-Ca v /Na v s are generally considered necessary for fast Na + /Ca 2+ -based signaling [7]. However, the cellular mechanisms underpinning the membrane physiology of many eukaryotes remain unexamined. Eukaryotic phytoplankton critically influence our climate as major primary producers. Several taxa, including the globally abundant diatoms, exhibit membrane excitability [8{\textendash}10]. We previously demonstrated that certain diatom genomes encode 4D-Ca v /Na v s [4] but also proteins of unknown function, resembling prokaryote single-domain, voltage-gated Na + channels (BacNa v s) [4]. Here, we show that single-domain channels are actually broadly distributed across major eukaryote phytoplankton lineages and represent three novel classes of single-domain channels, which we refer collectively to as EukCats. Functional characterization of diatom EukCatAs indicates that they are voltage-gated Na + - and Ca 2+ -permeable channels, with rapid kinetics resembling metazoan 4D-Ca v s/Na v s. In Phaeodactylum tricornutum, which lacks 4D-Ca v /Na v s, EukCatAs underpin voltage-activated Ca 2+ signaling important for membrane excitability, and mutants exhibit impaired motility. EukCatAs therefore provide alternative mechanisms for rapid Na + /Ca 2+ signaling in eukaryotes and may functionally replace 4D-Ca v s/Na v s in pennate diatoms. Marine phytoplankton thus possess unique signaling mechanisms that may be key to environmental sensing in the oceans. Diatoms exhibit fast animal-like action potentials, but many species lack 4D-Ca v /Na v channels that underpin membrane excitability in animals. Diatoms do encode novel 1D voltage-gated channels (EukCatAs). Helliwell, Chrachri et al. show that EukCatAs are fast Na + and Ca 2+ channels that provide alternative mechanisms for rapid signaling in eukaryotes.},
	keywords = {action potentials, BacNa v, calcium channel, diatoms, EukCats, gliding motility, ion selectivity, RCC299, signaling, single-domain channel, voltage-gated channel},
	issn = {09609822},
	doi = {10.1016/j.cub.2019.03.041},
	author = {Helliwell, Katherine E. and Chrachri, Abdul and Koester, Julie A. and Wharam, Susan and Verret, Frederic and Taylor, Alison R. and Wheeler, Glen L. and Brownlee, Colin}
}
@article {Walker2018,
	title = {The requirement for calcification differs between ecologically important coccolithophore species},
	journal = {New Phytologist},
	volume = {in press},
	year = {2018},
	note = {tex.mendeley-tags: RCC1731},
	month = {jun},
	keywords = {Calcification, coccolithophore, Coccolithus braarudii, Emiliania huxleyi, phytoplankton, rcc1731},
	issn = {0028646X},
	doi = {10.1111/nph.15272},
	url = {http://doi.wiley.com/10.1111/nph.15272},
	author = {Walker, Charlotte E. and Taylor, Alison R. and Langer, Gerald and Durak, Gra{\.z}yna M. and Heath, Sarah and Probert, Ian and Tyrrell, Toby and Brownlee, Colin and Wheeler, Glen L.}
}
