, Volume 247, Issue 3, pp 663–677 | Cite as

3D reconstruction of endoplasmic reticulum in a hydrocarbon-secreting green alga, Botryococcus braunii (Race B)

  • Reiko Suzuki
  • Ichiro Nishii
  • Shigeru Okada
  • Tetsuko Noguchi
Original Article


Main conclusion

Based on 3D sections through cells of Botryococcus braunii, the structure of three domains of endoplasmic reticulum, and their spatial and functional relationships to other organelles are clarified.

Oil production by photosynthetic microalgae has attracted attention since these oils can be converted into renewable, carbon-neutral fuels. The green alga B. braunii accumulates large amounts of hydrocarbons, 30–50% of cell dry weight, in extracellular spaces rather than its cytoplasm. To advance the knowledge of hydrocarbon biosynthesis and transport pathways in this alga, we utilized transmission EM combined with rapid freezing and image reconstruction. We constructed detailed 3D maps distinguishing three ER domains: rdER with ribosomes on both sides, rsER with ribosomes on one side, and sER without ribosomes. The rsER and sER domains were especially prominent during the oil body formation and oil secretion stages. The ER contacted the chloroplasts, oil bodies, or plasma membrane via the rsER domains, oriented with the ribosome-free surface facing the organelles. We discuss the following transport pathway for hydrocarbons and their precursors in the cytoplasm: chloroplast → endoplasmic reticulum (ER) → oil bodies → ER → plasma membrane → secretion. This study represents the first 3D study of the three-domain classification (rdER, rsER and sER) of the ER network among eukaryotic cells. Finally, we propose the novel features of the ERs in plant cells that are distinct from the latest proposed model for the ERs in mammalian cells.


Biofuel Botryococcus braunii Endoplasmic reticulum Lipid transport Lipid secretion 3D reconstruction 



Endoplasmic reticulum


Rough-surfaced ER


Rough double ER


Rough single ER


Smooth-surfaced ER



This work was supported by the CREST project of the Japan Science and Technology Agency. We thank Michiyo Yamamoto for her help in preparation of figure plates. We also thank Dr. Timothy P. Devarenne at Texas A & M University for kind advice and valuable suggestions to our manuscript.

Supplementary material

425_2017_2811_MOESM1_ESM.mpg (14.1 mb)
Supplemental Video 1 to 5 are movie clips (.mpg) of 3D reconstructed the ER and related organelles in half cells at stages 1-5 in Figure 3b. They show the changes along the contour which were created in the TRI/3D SRFIII software and the movie size was <18 MB. The ER domains (rdER red, rsER orange, sER yellow), a nucleus (cyan), a chloroplast (green), oil bodies (gray), and vacuoles (purple). 3D reconstructed interphase cell (MPG 14471 kb)
425_2017_2811_MOESM2_ESM.mpg (11.9 mb)
3D reconstructed growing cell before septum formation (MPG 12166 kb)
425_2017_2811_MOESM3_ESM.mpg (11.1 mb)
3D reconstructed cell accumulating oils on the cell surface (MPG 11375 kb)
425_2017_2811_MOESM4_ESM.mpg (13.6 mb)
3D reconstructed immature daughter cell (MPG 13896 kb)
425_2017_2811_MOESM5_ESM.mpg (12.2 mb)
3D reconstructed mature daughter cell (MPG 12486 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Nara Women’s UniversityNaraJapan
  2. 2.Department of Biological Sciences, Faculty of ScienceNara Women’s UniversityNaraJapan
  3. 3.Department of Aquatic BiosciencesThe University of TokyoTokyoJapan
  4. 4.JST, CRESTTokyoJapan

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