A continuum mechanics model of the plant cell wall reveals interplay between enzyme action and cell wall structure

Euan T. Smithers*, Jingxi Luo, Rosemary J. Dyson

*Corresponding author for this work

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Abstract

Plant cell growth is regulated through manipulation of the cell wall network, which consists of oriented cellulose microfibrils embedded within a ground matrix incorporating pectin and hemicellulose components. There remain many unknowns as to how this manipulation occurs. Experiments have shown that cellulose reorients in cell walls as the cell expands, while recent data suggest that growth is controlled by distinct collections of hemicellulose called biomechanical hotspots, which join the cellulose molecule together. The enzymes expansin and Cel12A have both been shown to induce growth of the cell wall; however, while Cel12A’s wall-loosening action leads to a reduction in the cell wall strength, expansin’s has been shown to increase the strength of the cell wall. In contrast, members of the XTH enzyme family hydrolyse hemicellulose but do not appear to cause wall creep. This experimentally observed behaviour still awaits a full explanation. We derive and analyse a mathematical model for the effective mechanical properties of the evolving cell wall network, incorporating cellulose microfibrils, which reorient with cell growth and are linked via biomechanical hotspots made up of regions of crosslinking hemicellulose. Assuming a visco-elastic response for the cell wall and using a continuum approach, we calculate the total stress resultant of the cell wall for a given overall growth rate. By changing appropriate parameters affecting breakage rate and viscous properties, we provide evidence for the biomechanical hotspot hypothesis and develop mechanistic understanding of the growth-inducing enzymes. 

Original languageEnglish
Article number1
Number of pages30
JournalEuropean Physical Journal E
Volume47
Issue number1
DOIs
Publication statusPublished - 6 Jan 2024

Bibliographical note

Funding Information:
We would like to thank Cara Neal and Alexander Brune for their helpful inputs and the reviewers. RJD and ETS thank EPSRC for funding via grants EP/M00015X/1 and EP/N509590/1, respectively.

Publisher Copyright:
© 2024, The Author(s).

ASJC Scopus subject areas

  • Biotechnology
  • Biophysics
  • General Chemistry
  • General Materials Science
  • Surfaces and Interfaces

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