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Biomineralization Pathways in Calcifying Dinoflagellates: Uptake, Storage in MgCaP-Rich Bodies and Formation of the Shell

44 Pages Posted: 15 Aug 2019 Publication Status: Accepted

See all articles by Anne Jantschke

Anne Jantschke

Weizmann Institute of Science - Department of Structural Biology; Dresden University of Technology - Bioanalytical Chemistry

Steve Weiner

Weizmann Institute of Science - Department of Structural Biology

Andreas Schertel

Carl Zeiss X-ray Microscopy, Inc.

Lia Addadi

Weizmann Institute of Science - Department of Structural Biology

Iddo Pinkas

Weizmann Institute of Science - Department of Chemical Research Support

Abstract

Little is known about the formation of the shells of calcareous dinoflagellates, despite the fact that they are one of the major calcifying organisms of the phytoplankton. Here, we investigate calcitic cyst formation in two representative members from different clades of calcareous dinoflagellates using cryo-electron microscopy (cryo-SEM and cryo-FIB-SEM) in combination with micro-Raman and infrared spectroscopy.Only calcein-AM and not calcein enters these cells, indicating active uptake of calcium and other divalent cations. Multifunctional vacuoles containing crystalline inclusions are observed in both species and we identify the crystals as anhydrous guanine in the β-form. We also observe in the same vacuolar enclosures, dense magnesium, calcium and phosphorous rich mineral bodies by cryo EDX. These bodies are secreted into the outer matrix space where calcite forms. Calcite formation occurs via multiple independent nucleation events and the different crystals grow with preferred orientation into a dense reticular network that forms the calcitic cyst. The degree of atomic order of this calcite is less than that of geological calcite. We suggest a common biomineralization pathway for these two calcifying dinoflagellates: (1) Uptake of calcium and other cations through the membranes. (2) Deposition of Mg2+ and Ca2+ ions inside a disordered MgCaP-body. (3) Secretion of these bodies to the space between the outer membranes. (4) Formation and growth of calcite bodies into a dense reticulate network that forms the mature calcitic shell. This study provides new insights into calcium uptake, storage and transport in calcifying dinoflagellates.

Keywords: biomineralization, dinoflagellates, guanine crystals, calcitic cysts, cryo-FIB-SEM

Suggested Citation

Jantschke, Anne and Weiner, Steve and Schertel, Andreas and Addadi, Lia and Pinkas, Iddo, Biomineralization Pathways in Calcifying Dinoflagellates: Uptake, Storage in MgCaP-Rich Bodies and Formation of the Shell. Available at SSRN: https://ssrn.com/abstract=3435955 or http://dx.doi.org/10.2139/ssrn.3435955

Anne Jantschke (Contact Author)

Weizmann Institute of Science - Department of Structural Biology ( email )

Israel

Dresden University of Technology - Bioanalytical Chemistry ( email )

Germany

Steve Weiner

Weizmann Institute of Science - Department of Structural Biology ( email )

Israel

Andreas Schertel

Carl Zeiss X-ray Microscopy, Inc.

4385 Hopyard Rd Suite 100
Pleasanton, CA 94588
United States

Lia Addadi

Weizmann Institute of Science - Department of Structural Biology

Israel

Iddo Pinkas

Weizmann Institute of Science - Department of Chemical Research Support

Israel

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