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Hain TM, Bykowski M, Saba M, Evans ME, Schröder-Turk GE, Kowalewska Ł. SPIRE-a software tool for bicontinuous phase recognition: application for plastid cubic membranes. Plant Physiol 2022; 188:81-96. [PMID: 34662407 PMCID: PMC8774748 DOI: 10.1093/plphys/kiab476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 09/17/2021] [Indexed: 06/13/2023]
Abstract
Bicontinuous membranes in cell organelles epitomize nature's ability to create complex functional nanostructures. Like their synthetic counterparts, these membranes are characterized by continuous membrane sheets draped onto topologically complex saddle-shaped surfaces with a periodic network-like structure. Their structure sizes, (around 50-500 nm), and fluid nature make transmission electron microscopy (TEM) the analysis method of choice to decipher their nanostructural features. Here we present a tool, Surface Projection Image Recognition Environment (SPIRE), to identify bicontinuous structures from TEM sections through interactive identification by comparison to mathematical "nodal surface" models. The prolamellar body (PLB) of plant etioplasts is a bicontinuous membrane structure with a key physiological role in chloroplast biogenesis. However, the determination of its spatial structural features has been held back by the lack of tools enabling the identification and quantitative analysis of symmetric membrane conformations. Using our SPIRE tool, we achieved a robust identification of the bicontinuous diamond surface as the dominant PLB geometry in angiosperm etioplasts in contrast to earlier long-standing assertions in the literature. Our data also provide insights into membrane storage capacities of PLBs with different volume proportions and hint at the limited role of a plastid ribosome localization directly inside the PLB grid for its proper functioning. This represents an important step in understanding their as yet elusive structure-function relationship.
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Affiliation(s)
- Tobias M Hain
- Institute of Mathematics, University of Potsdam, Potsdam D-14476, Germany
- College of Science, Health, Engineering and Education, Mathematics and Statistics, Murdoch University, Murdoch WA 6150, Australia
- Physical Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Lund 22100, Sweden
| | - Michał Bykowski
- Department of Plant Anatomy and Cytology, Faculty of Biology, Institute of Experimental Plant Biology and Biotechnology, University of Warsaw, Warsaw, Poland
| | - Matthias Saba
- Adolphe Merkle Institute, University of Fribourg, Fribourg CH-1700, Switzerland
| | - Myfanwy E Evans
- Institute of Mathematics, University of Potsdam, Potsdam D-14476, Germany
| | - Gerd E Schröder-Turk
- College of Science, Health, Engineering and Education, Mathematics and Statistics, Murdoch University, Murdoch WA 6150, Australia
- Department of Applied Mathematics, The Australian National University, Research School of Physics, Canberra 2601, Australia
| | - Łucja Kowalewska
- Department of Plant Anatomy and Cytology, Faculty of Biology, Institute of Experimental Plant Biology and Biotechnology, University of Warsaw, Warsaw, Poland
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