AFM-based Mapping of the Elastic Properties of Cell Walls: at Tissue, Cellular, and Subcellular Resolutions

Abstract

We describe a recently developed method to measure mechanical properties of the surfaces of plant tissues using atomic force microscopy (AFM) micro/nano-indentations, for a JPK AFM. Specifically, in this protocol we measure the apparent Young's modulus of cell walls at subcellular resolutions across regions of up to 100 µm x 100 µm in floral meristems, hypocotyls, and roots. This requires careful preparation of the sample, the correct selection of micro-indenters and indentation depths. To account for cell wall properties only, measurements are performed in highly concentrated solutions of mannitol in order to plasmolyze the cells and thus remove the contribution of cell turgor pressure.In contrast to other extant techniques, by using different indenters and indentation depths, this method allows simultaneous multiscale measurements, i.e. at subcellular resolutions and across hundreds of cells comprising a tissue. This means that it is now possible to spatiallytemporally characterize the changes that take place in the mechanical properties of cell walls during development, enabling these changes to be correlated with growth and differentiation. This represents a key step to understand how coordinated microscopic cellular changes bring about macroscopic morphogenetic events.However, several limitations remain: the method can only be used on fairly small samples (around 100 µm in diameter) and only on external tissues; the method is sensitive to tissue topography; it measures only certain aspects of the tissue's complex mechanical properties. The technique is being developed rapidly and it is likely that most of these limitations will be resolved in the near future. Video LinkThe video component of this article can be found at

The Control of Growth Symmetry Breaking in the Arabidopsis Hypocotyl

“…Cells using AFM Using a previously established AFM-based indentation technique [6,7], we measured the stiffness of the anticlinal (i.e., perpendicular to the organ surface) epidermal walls of plasmolysed cells 19 hr after germination ( Figure 1). An apparent Young's modulus was calculated for transverse and longitudinal cell walls [7].…”

“…An apparent Young's modulus was calculated for transverse and longitudinal cell walls [7]. The smaller symmetric cells at the top of the hypocotyl showed comparable values for both types of walls.…”

Nanometrology of Biomass for Bioenergy: The Role of Atomic Force Microscopy and Spectroscopy in Plant Cell Characterization

“…Quantitative force-volume mapping has been used to study the nanomechanical properties of plant cell walls at every step of the delignification process (Peaucelle, 2014;Farahi et al, 2017). Figure 2, the Young's moduli varied toward lower values as the lignin was removed with a decrease from 4.7 ± 0.7 GPa for UR to 0.34 ± 0.07 GPa for EHA therefore suggesting total removal of the hemicellulose and lignin from the sample.…”

The mechanical properties of plant cell walls soft material at the subcellular scale: the implications of water and of the intercellular boundaries

“…The cells of higher plants are much smaller (micrometer scale), and the extraction of samples from a single cell presents many challenges. Recently, an atomic force microscopy (AFM)-based nanoindentation technique has been used extensively to probe and characterize both primary and secondary cell walls at the subcellular scale [33][34][35]. The strength of the AFM-based nanoindentation technique is that the samples do not need to be isolated from the tissue; instead, the AFM tip can scan and characterize samples with nanoscale spatial resolution.…”