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bioRxiv · 10.1101/2024.11.15.623571

Dynamic change of calcium-rich compartments during coccolithophore biomineralization

Triccas, A.·Chevrier, D. M.·Verezhak, M.·Ihli, J.·Guizar-Sicairos, M.·Holler, M.·Scheffel, A.·Ozaki, N.·Chamard, V.·Wood, R.·Grunewald, T. A.·Nudelman, F.
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Abstract

Coccolithophores are abundant marine phytoplankton that produce biomineralized calcite scales, called coccoliths, which sequester substantial amounts of carbon and play a significant role in biogeochemical cycles. However, mechanisms underlying the storage and transport of ions essential for calcification remain unresolved. We used ptychographic X-ray computed tomography under cryogenic conditions to visualize intracellular calcium-rich structures involved in the storage of calcium ions in the coccolithophore species Chrysotila carterae. During calcification, we observed a range of structures, from small electron-dense bodies within larger compartments, to denser and distributed globular compartments, before returning to small bodies once scale formation is complete. Nanobeam-scanning X-ray fluorescence measurements further revealed these electron-dense bodies are rich in P and Ca (molar ratio of [~]4:1). We infer from the dynamic nature of structures that these bodies are part of required cellular calcium ion transport pathways, a fundamental process critical for understanding the response of coccolithophores to climate change.

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Triccas, A., Chevrier, D. M., Verezhak, M., Ihli, J., Guizar-Sicairos, M., Holler, M., Scheffel, A., Ozaki, N., Chamard, V., Wood, R., Grunewald, T. A., Nudelman, F.. 2024-11-15. Dynamic change of calcium-rich compartments during coccolithophore biomineralization. https://doi.org/10.1101/2024.11.15.623571

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