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The Mechanics of Poro-Elastic Contractile Actomyosin Networks As a Model System of the Cell Cytoskeleton
Published on: March 10, 2023
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Elastic properties of the forisome
Stephen A Warmann1, William F Pickard2, Amy Q Shen1
1Department of Mechanical and Aerospace Engineering, Washington University in St Louis, St Louis, MO, USA.
Functional Plant Biology : FPB
|July 22, 2020
Summary
Forisomes, Ca2+-responsive protein bodies in legume phloem, exhibit direction-dependent mechanical properties. Their stiffness decreases after Ca2+ activation, impacting flow regulation.
Area of Science:
- Plant Biology
- Biophysics
- Materials Science
Background:
- Forisomes are Ca2+-responsive contractile protein bodies crucial for regulating phloem transport in legumes.
- Understanding the in vitro mechanical properties of forisomes is essential for elucidating their in vivo physiological functions.
Purpose of the Study:
- To investigate the viscoelastic properties of forisomes from Canavalia gladiata and Vicia faba using microscopic tensile tests.
- To determine the mechanical response of forisomes before and after Ca2+-induced contraction in both longitudinal and radial directions.
Main Methods:
- Microcantilever-based microscopic tensile tests, including incremental stress-relaxation measurements, were performed on forisomes.
- Viscoelastic properties were analyzed in the longitudinal and radial directions.
- Creep data were fitted using a three-parameter viscoelastic model.
Main Results:
- Forisomes exhibit anisotropic mechanical properties, with a significantly higher elastic modulus in the longitudinal direction compared to the radial direction.
- Pre-contraction longitudinal elastic moduli were similar between Vicia faba (660 ± 360 kPa) and Canavalia gladiata (600 ± 360 kPa).
- Ca2+-induced activation reduced longitudinal stiffness and altered the stress-strain curve, indicating controlled protein structure changes.
- Measured contractile forces were approximately 510 ± 390 nN for V. faba and 570 ± 310 nN for C. gladiata.
Conclusions:
- Forisomes possess a unidirectional fibrous structure, contributing to their direction-dependent mechanical behavior.
- The reduced stiffness upon activation suggests a mechanism for controlled modulation of phloem transport.
- These findings provide critical insights into the biomechanics of forisomes and their role in plant physiology.
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