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Structure and Function of Chloroplasts

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Front. Plant Sci. | doi: 10.3389/fpls.2018.00370

Alterations of membrane lipid content correlated with chloroplasts and mitochondria development in Euglena gracilis

Shiori Shibata1, Shin-Ichi Arimura2, 3,  Takahiro Ishikawa4, 5 and  Koichiro Awai1, 5, 6*
  • 1Graduate School of Integrated Science and Technology, Shizuoka University, Japan
  • 2Graduate School of Agricultural and Life Sciences,The University of Tokyo, Japan
  • 3PRESTO, Japan Science and Technology Agency, Japan
  • 4Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Japan
  • 5Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Japan
  • 6Research Institute of Electronics, Shizuoka University, Japan

Euglenoids are unique protists that can grow photoautotrophically, photomixotrophically, and heterotrophically. Here we grew Euglena gracilis under these different growth conditions and determined cellular contents of seven membrane lipids and one storage lipid (triacylglycerol), which account for more than 94 mol% of total membrane lipids. We also describe the relationship among chloroplast and mitochondria developments with lipid contents, protein contents, and oxygen evolution/consumption rates. In photoautotrophic growth conditions, E. gracilis cells accumulated chlorophyll, photosynthetic proteins, and glycolipids typical to thylakoid membranes. The same occurred for the cells grown under photomixotrophic conditions with higher respiration rates. In heterotrophic conditions, E. gracilis cells had higher respiration rates compared to cells grown in other conditions with the accumulation of pyruvate: NADP+ oxidoreductase, a mitochondrial protein and phospholipid common in mitochondria. Cells were also observed using a confocal laser scanning microscope and found to show more chlorophyll autofluorescence when grown photoautotrophically and photomixotrophycally, and fluorescence of MitoTracker when grown photomixotrophically and heterotrophically. These results suggest that under illumination, E. gracilis develops functional thylakoid membranes with membrane lipids and proteins for photosynthesis. In the medium with glucose, the cells develop mitochondria with phospholipids and proteins for respiration. Possible application based on lipid analysis for the enhancement of wax ester or alkene synthesis is discussed.

Keywords: Euglena gracilis, Membrane Lipids, Photosynthesis, Respiration, thylakoid membranes, Mitotracker, confocal laser scanning microscopy

Received: 30 Nov 2017; Accepted: 06 Mar 2018.

Edited by:

Rebecca L. Roston, University of Nebraska-Lincoln, United States

Reviewed by:

Yonghua Li-Beisson, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), France
Wayne Riekhof, University of Nebraska-Lincoln, United States  

Copyright: © 2018 Shibata, Arimura, Ishikawa and Awai. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Koichiro Awai, Shizuoka University, Graduate School of Integrated Science and Technology, Shizuoka, Japan,