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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Plant Sci. | doi: 10.3389/fpls.2019.01398

Structural imaging of native cryo-preserved secondary cell walls reveals the presence of macrofibrils and their formation requires normal cellulose, lignin and xylan biosynthesis.

  • 1Department of Biochemistry, University of Cambridge, United Kingdom
  • 2Natural Material Innovation Centre, University of Cambridge, United Kingdom
  • 3Sainsbury Laboratory, University of Cambridge, United Kingdom
  • 4Institute of Biotechnology/Department of Biological and Environmental Sciences, University of Helsinki, Finland

1 Abstract
The woody secondary cell walls of plants are the largest repository of renewable carbon biopolymers on the planet. These walls are made principally from cellulose and hemicelluloses and are impregnated with lignin. Despite their importance as the main load bearing structure for plant growth, as well as their industrial importance as both a material and energy source, the precise arrangement of these constituents within the cell wall is not yet fully understood. We have adapted low temperature scanning electron microscopy (cryo-SEM) for imaging the nanoscale architecture of angiosperm and gymnosperm cell walls in their native hydrated state. Our work confirms that cell wall macrofibrils, cylindrical structures with a diameter exceeding 10 nm, are a common feature of the native hardwood and softwood samples. We have observed these same structures in Arabidopsis thaliana secondary cell walls, enabling macrofibrils to be compared between mutant lines that are perturbed in cellulose, hemicellulose and lignin formation. Our analysis indicates that the macrofibrils in Arabidopsis cell walls are dependent upon the proper biosynthesis, or composed, of cellulose, xylan and lignin. This study establishes that cryo-SEM is a useful additional approach for investigating the native nanoscale architecture and composition of hardwood and softwood secondary cell walls and demonstrates the applicability of Arabidopsis genetic resources to relate fibril structure with wall composition and biosynthesis.

Keywords: SEM, cell walls, Macrofibrils, Cellulose, Xylan, Lignin, Softwood, Hardwood

Received: 23 May 2019; Accepted: 10 Oct 2019.

Copyright: © 2019 Lyczakowski, Bourdon, Terrett, Helariutta, Wightman and Dupree. 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(s) 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. Raymond Wightman, Sainsbury Laboratory, University of Cambridge, Cambridge, CB2 1LR, England, United Kingdom, raymond.wightman@slcu.cam.ac.uk
Prof. Paul Dupree, University of Cambridge, Department of Biochemistry, Cambridge, CB2 1TN, England, United Kingdom, pd101@cam.ac.uk