Reiko Suzuki1,2, Ichiro Nishii3,2, Shigeru Okada4,2, Tetsuko Noguchi5,6. 1. Nara Women's University, Kitauoya-nishimachi, Nara, 630-8506, Japan. 2. JST, CREST, 5 Sanbancho, Chiyoda, Tokyo, 102-0075, Japan. 3. Department of Biological Sciences, Faculty of Science, Nara Women's University, Kitauoya-nishimachi, Nara, 630-8506, Japan. 4. Department of Aquatic Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-8657, Japan. 5. Nara Women's University, Kitauoya-nishimachi, Nara, 630-8506, Japan. noguchi@cc.nara-wu.ac.jp. 6. JST, CREST, 5 Sanbancho, Chiyoda, Tokyo, 102-0075, Japan. noguchi@cc.nara-wu.ac.jp.
Abstract
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.
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.
Entities:
Keywords:
3D reconstruction; Biofuel; Botryococcus braunii; Endoplasmic reticulum; Lipid secretion; Lipid transport
Authors: Taylor L Weiss; Robyn Roth; Carrie Goodson; Stanislav Vitha; Ian Black; Parastoo Azadi; Jannette Rusch; Andreas Holzenburg; Timothy P Devarenne; Ursula Goodenough Journal: Eukaryot Cell Date: 2012-08-31
Authors: Derk Binns; Tom Januszewski; Yue Chen; Justin Hill; Vladislav S Markin; Yingming Zhao; Christopher Gilpin; Kent D Chapman; Richard G W Anderson; Joel M Goodman Journal: J Cell Biol Date: 2006-05-30 Impact factor: 10.539