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Licensed Unlicensed Requires Authentication Published by De Gruyter May 14, 2021

New insights on Laminaria digitata ultrastructure through combined conventional chemical fixation and cryofixation

  • Christos Katsaros

    Christos Katsaros is a Professor Emeritus in the Department of Biology of the University of Athens Greece, specialising in macroalgal morphogenesis. He was awarded a PhD on the morphogenesis of selected brown algae. After that, he extended his research on algae and seagrasses, addressing questions ranging from the cell structure and the role of the cytoskeleton in cell morphogenesis, to host-parasite interactions, as well as to the effects of environmental changes on the cell structure and development.

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    , Sophie Le Panse

    Sophie Le Panse is in charge of the Merimage core imaging facility at the Station Biologique de Roscoff since 2008 after 10 years at the Institut Jacques Monod in Paris. Merimage has two areas of activities: electronic microscopy and optical microscopy. The facility works mainly for research applications in the life and marine sciences and is open both to internal and external scientists in Roscoff. She did her PhD at Pierre & Marie Curie University in Paris and then conducted post-doctoral research at the Institute of Anatomy, Aarhus University, Denmark, before joining the CNRS (Centre National de la Recherché Scientifique).

    , Gillian Milne

    Gillian Milne has been part of the technical team at University of Aberdeen since 2003. Originating in the Ophthalmology Department dealing with samples for histological preparation, she then moved over to the newly formed Microscopy & Histology Core Facility in 2006. Here she has gained experience in a variety of histological methods as well as transmission electron microscopy. Working with a large variety of sample types (yeast, honey bees, human nails, algae to name a few) she has developed skills in many preparation methods and protocols, including high pressure freezing and freeze substitution.

    , Carl J. Carrano

    Professor Carl J. Carrano has extensive experience in elucidating the function of inorganic trace elements in biological systems. He received his BS (chemistry) from UC Santa Barbara, his PhD from Texas A&M and did postdoctoral work at UC Berkeley. With 40+ years of academic experience at the University of Vermont, Texas State University and San Diego State University, he has authored >180 peer reviewed publications, is an associate editor of the journal Molecules, editor in chief of the journal BioMetals, and was honoured by being elected a Fellow in Chemistry by the AAAS and the Royal Society of Chemistry.

    and Frithjof Christian Küpper

    Frithjof Christian Küpper has held the Chair in Marine Biodiversity at the University of Aberdeen since 2011, after eight years at the Scottish Association for Marine Science (Oban) as a lecturer and reader, studying the biodiversity and biochemistry of marine plants/algae. He conducted graduate studies at Roscoff and Konstanz for a joint French-German PhD. His research found that iodide serves as an inorganic antioxidant in kelp, the first described from a living system, impacting atmospheric and marine chemistry. A certified scientific diver, Frithjof has worked in the Mediterranean, South Atlantic (Ascension and Falkland Islands), Antarctica, the Arctic and the Arabian Gulf.

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From the journal Botanica Marina

Abstract

The objective of the present study is to examine the fine structure of vegetative cells of Laminaria digitata using both chemical fixation and cryofixation. Laminaria digitata was chosen due to its importance as a model organism in a wide range of biological studies, as a keystone species on rocky shores of the North Atlantic, its use of iodide as a unique inorganic antioxidant, and its significance as a raw material for the production of alginate. Details of the fine structural features of vegetative cells are described, with particular emphasis on the differences between the two methods used, i.e. conventional chemical fixation and freeze-fixation. The general structure of the cells was similar to that already described, with minor differences between the different cell types. An intense activity of the Golgi system was found associated with the thick external cell wall, with large dictyosomes from which numerous vesicles and cisternae are released. An interesting type of cisternae was found in the cryofixed material, which was not visible with the chemical fixation. These are elongated structures, in sections appearing tubule-like, close to the external cell wall or to young internal walls. An increased number of these structures was observed near the plasmodesmata of the pit fields. They are similar to the “flat cisternae” found associated with the forming cytokinetic diaphragm of brown algae. Their possible role is discussed. The new findings of this work underline the importance of such combined studies which reveal new data not known until now using the old conventional methods. The main conclusion of the present study is that cryofixation is the method of choice for studying Laminaria cytology by transmission electron microscopy.


Dedication: This paper is dedicated to Susan Loiseaux-de Goër in Roscoff, one of the pioneers of brown algal cell biology and the techniques in electron microscopy for its study.



Corresponding authors: Christos Katsaros, Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 157 84, Greece, E-mail: ; and Frithjof Christian Küpper, Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA, 92182-1030, USA; School of Biological Sciences, University of Aberdeen, Cruickshank Building, St Machar Drive, Aberdeen, AB24 3UU, SC, UK; and Department of Chemistry, Marine Biodiscovery Centre, University of Aberdeen, Aberdeen, AB24 3UE, SC, UK, E-mail:

Funding source: European Union’s Horizon 2020

Award Identifier / Grant number: 730984

Funding source: Natural Environment Research Council (NERC)

Award Identifier / Grant number: NE/D521522/1, NE/F012705/1

Funding source: National Science Foundation

Award Identifier / Grant number: CHE-1664657

Funding source: National Oceanic & Atmospheric Administration

Funding source: Scottish Funding Council

Award Identifier / Grant number: HR09011

About the authors

Christos Katsaros

Christos Katsaros is a Professor Emeritus in the Department of Biology of the University of Athens Greece, specialising in macroalgal morphogenesis. He was awarded a PhD on the morphogenesis of selected brown algae. After that, he extended his research on algae and seagrasses, addressing questions ranging from the cell structure and the role of the cytoskeleton in cell morphogenesis, to host-parasite interactions, as well as to the effects of environmental changes on the cell structure and development.

Sophie Le Panse

Sophie Le Panse is in charge of the Merimage core imaging facility at the Station Biologique de Roscoff since 2008 after 10 years at the Institut Jacques Monod in Paris. Merimage has two areas of activities: electronic microscopy and optical microscopy. The facility works mainly for research applications in the life and marine sciences and is open both to internal and external scientists in Roscoff. She did her PhD at Pierre & Marie Curie University in Paris and then conducted post-doctoral research at the Institute of Anatomy, Aarhus University, Denmark, before joining the CNRS (Centre National de la Recherché Scientifique).

Gillian Milne

Gillian Milne has been part of the technical team at University of Aberdeen since 2003. Originating in the Ophthalmology Department dealing with samples for histological preparation, she then moved over to the newly formed Microscopy & Histology Core Facility in 2006. Here she has gained experience in a variety of histological methods as well as transmission electron microscopy. Working with a large variety of sample types (yeast, honey bees, human nails, algae to name a few) she has developed skills in many preparation methods and protocols, including high pressure freezing and freeze substitution.

Carl J. Carrano

Professor Carl J. Carrano has extensive experience in elucidating the function of inorganic trace elements in biological systems. He received his BS (chemistry) from UC Santa Barbara, his PhD from Texas A&M and did postdoctoral work at UC Berkeley. With 40+ years of academic experience at the University of Vermont, Texas State University and San Diego State University, he has authored >180 peer reviewed publications, is an associate editor of the journal Molecules, editor in chief of the journal BioMetals, and was honoured by being elected a Fellow in Chemistry by the AAAS and the Royal Society of Chemistry.

Frithjof Christian Küpper

Frithjof Christian Küpper has held the Chair in Marine Biodiversity at the University of Aberdeen since 2011, after eight years at the Scottish Association for Marine Science (Oban) as a lecturer and reader, studying the biodiversity and biochemistry of marine plants/algae. He conducted graduate studies at Roscoff and Konstanz for a joint French-German PhD. His research found that iodide serves as an inorganic antioxidant in kelp, the first described from a living system, impacting atmospheric and marine chemistry. A certified scientific diver, Frithjof has worked in the Mediterranean, South Atlantic (Ascension and Falkland Islands), Antarctica, the Arctic and the Arabian Gulf.

Acknowledgements

We would like to acknowledge Susan Loiseaux-de Goër, Bernard Kloareg, Philippe Potin and Akira F. Peters for their hospitality and support to FCK and CK during their visit to Roscoff.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: The research leading to these results received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 730984, ASSEMBLE Plus project 370, supporting access of CK and FCK to the Station Biologique de Roscoff. This work was conducted in conjunction with the European Marine Biological Resource Centre (EMBRC-ERIC), EMBRC-France. French state funds are managed by the ANR within the Investments of the Future program under reference ANR-10-INSB-02. Also, funding from the UK Natural Environment Research Council (NERC) through grants NE/D521522/1, NE/F012705/1, and Oceans 2025 (WP4.5) programs to FCK; the National Science Foundation (CHE-1664657) and the National Oceanic & Atmospheric Administration to CJC and FCK; and the MASTS pooling initiative (Marine Alliance for Science and Technology for Scotland, funded by the Scottish Funding Council and contributing institutions; grant reference HR09011) is gratefully acknowledged.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

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Received: 2020-10-23
Accepted: 2021-04-08
Published Online: 2021-05-14
Published in Print: 2021-06-25

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