This research was funded by CSIC I+D 2018, grant No. 95 (Mariana Sotelo Silveira).; CSIC Grupos (Omar Borsani) and PEDECIBA.

1. Preparation of the plant material and growth conditions
<ol>
	<li>To generate the needed plant material, sterilize the seeds of Arabidopsis wild type and mutant lines of interest. 
	NOTE: In this protocol, we used the following: ttl1: T-DNA insertion lines Salk_063943 (for TTL1; AT1G53300) - Columbia-0 (Col-0) wild-type; the Procuste1 (prc1-1) mutant, which consists of a knock-out mutation (Q720stop) in the CESA6 gene (AT5G64740), as previously descr...

<ol>
	<li>Anderson, C. T., Kieber, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+construction,+perception,+and+remodeling+of+plant+cell+walls.">Dynamic construction, perception, and remodeling of plant cell walls.</a> Annual Review of Plant Biology. 71, 39-69 (2020).</li><li>Roeder, A. H. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fifteen+compelling+open+questions+in+plant+cell+biology.">Fifteen compelling open questions in plant cell biology.</a> The Plant Cell. 34 (1), 72-102 (2022).</li><li>Zhang, B., Gao, Y., Zhang, L., Zhou, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+plant+cell+wall:+Biosynthesis,+construction,+and+functions.">The plant cell wall: Biosynthesis, construction, and functions.</a> Journal of Integrative Plant Biology. 63 (1), 251-272 (2021).</li><li>Hamant, O., Haswell, E. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Life+behind+the+wall:+Sensing+mechanical+cues+in+plants.">Life behind the wall: Sensing mechanical cues in plants.</a> BMC Biology. 15 (59), 1-9 (2017).</li><li>Scheres, B., Benfey, P., Dolan, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Root+development.">Root development.</a> The Arabidopsis Book. 1, 0101 (2002).</li><li>Cuadrado-Pedetti, M. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+arabidopsis+tetratricopeptide+thioredoxin-like+1+gene+is+involved+in+anisotropic+root+growth+during+osmotic+stress+adaptation.">The arabidopsis tetratricopeptide thioredoxin-like 1 gene is involved in anisotropic root growth during osmotic stress adaptation.</a> Genes. 12 (2), 236 (2021).</li><li>Milani, P., Braybrook, S. A., Boudaoud, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shrinking+the+hammer:+micromechanical+approaches+to+morphogenesis.">Shrinking the hammer: micromechanical approaches to morphogenesis.</a> Journal of Experimental Botany. 64 (15), 4651-4662 (2013).</li><li>Braybrook, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+the+elasticity+of+plant+cells+with+atomic+force+microscopy.">Measuring the elasticity of plant cells with atomic force microscopy.</a> Methods in Cell Biology. 125, 237-254 (2015).</li><li>Bidhendi, A. J., Geitmann, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+to+quantify+primary+plant+cell+wall+mechanics.">Methods to quantify primary plant cell wall mechanics.</a> Journal of Experimental Botany. 70 (14), 3615-3648 (2019).</li><li>Desnos, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Procuste1+mutants+identify+two+distinct+genetic+pathways+controlling+hypocotyl+cell+elongation,+respectively+in+dark-+and+light-grown+Arabidopsis+seedlings.">Procuste1 mutants identify two distinct genetic pathways controlling hypocotyl cell elongation, respectively in dark- and light-grown Arabidopsis seedlings.</a> Development. 122 (2), 683-693 (1996).</li><li>Fagard, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Procuste1+encodes+a+cellulose+synthase+required+for+normal+cell+elongation+specifically+in+roots+and+dark-grown+hypocotyls+of+arabidopsis.">Procuste1 encodes a cellulose synthase required for normal cell elongation specifically in roots and dark-grown hypocotyls of arabidopsis.</a> The Plant Cell. 12 (12), 2409-2423 (2000).</li><li>Murashige, T., Skoog, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+revised+medium+for+rapid+growth+and+bio+assays+with+tobacco+tissue+cultures.">A revised medium for rapid growth and bio assays with tobacco tissue cultures.</a> Physiologia Plantarum. 15 (3), 473-497 (1962).</li><li>Perilli, S., Sabatini, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+root+meristem+size+development.">Analysis of root meristem size development.</a> Methods in Molecular Biology. 655, 177-187 (2010).</li><li>Sader, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+virtual+instrument+to+standardise+the+calibration+of+atomic+force+microscope+cantilevers.">A virtual instrument to standardise the calibration of atomic force microscope cantilevers.</a> Review of Scientific Instruments. 87 (9), 093711 (2016).</li><li>Collinsworth, A. M., Zhang, S., Kraus, W. E., Truskey, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apparent+elastic+modulus+and+hysteresis+of+skeletal+muscle+cells+throughout+differentiation.">Apparent elastic modulus and hysteresis of skeletal muscle cells throughout differentiation.</a> American Journal of Physiology - Cell Physiology. 283 (4), 1219-1227 (2002).</li><li>Mathur, A. B., Collinsworth, A. M., Reichert, W. M., Kraus, W. E., Truskey, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial,+cardiac+muscle+and+skeletal+muscle+exhibit+different+viscous+and+elastic+properties+as+determined+by+atomic+force+microscopy.">Endothelial, cardiac muscle and skeletal muscle exhibit different viscous and elastic properties as determined by atomic force microscopy.</a> Journal of Biomechanics. 34 (12), 1545-1553 (2001).</li><li>Sirghi, L., Ponti, J., Broggi, F., Rossi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+elasticity+and+adhesion+of+live+cells+by+atomic+force+microscopy+indentation.">Probing elasticity and adhesion of live cells by atomic force microscopy indentation.</a> European Biophysics Journal. 37 (6), 935-945 (2008).</li><li>Peaucelle, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AFM-based+mapping+of+the+elastic+properties+of+cell+walls:+At+tissue,+cellular,+and+subcellular+resolutions.">AFM-based mapping of the elastic properties of cell walls: At tissue, cellular, and subcellular resolutions.</a> Journal of Visualized Experiments: JoVE. (89), e51317 (2014).</li><li>Peaucelle, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pectin-induced+changes+in+cell+wall+mechanics+underlie+organ+initiation+in+Arabidopsis.">Pectin-induced changes in cell wall mechanics underlie organ initiation in Arabidopsis.</a> Current Biology. 21 (20), 1720-1726 (2011).</li><li>Fernandes, A. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+epidermal+cells+of+whole+living+roots+of+Arabidopsis+thaliana:+An+atomic+force+microscopy+study.">Mechanical properties of epidermal cells of whole living roots of Arabidopsis thaliana: An atomic force microscopy study.</a> Physical Review E. 85 (2), 21916 (2012).</li></ol>

The authors have no conflicts of interest. The MATLAB script used for fitting the data is available upon personal request by writing to J. C. B.

Cell and cell-wall mechanics are increasingly becoming relevant to gain insight into how mechanics affects growth processes. As physical forces propagate over considerable distances in solid tissues, the study of changes in the physical properties of the cell wall and how they are sensed, controlled, tuned, and impact the plant&#39;s growth are becoming an important field of study2,3,8.
A method is pr...

Plant cells are surrounded by a cell wall that is a complex structure composed of interacting networks of polysaccharides, proteins, metabolites, and water that varies in thickness from 0.1 to several &#181;m depending on the cell type and the phase of growth1,2. Cell wall mechanical properties play an essential role in the growth of plants. Low stiffness values of the cell wall have been proposed as a precondition for cell growth and cell-wall expansion, and there is increasing evidence that all cells sense mechanical forces to perform their functions. However, it is still debated whether changes in the physical properties of the cell wall determines cell fate2,3,4. Because plant cells do not move during development, the final shape of an organ depends on how far and in what direction a cell expands. Thus, Arabidopsis root is a good model to study the impact of cell wall physical properties in cell expansion because different types of expansion occur in different regions of the root. For example, anisotropic expansion is evident in the elongation zone and particularly noticeably in the epidermal cells5.
The method described here was used to characterize the physical properties of the cell wall of epidermal cells at the nanoscale of living Arabidopsis roots using an Atomic Force Microscope (AFM) coupled with an inverted fluorescence phase microscope6. For an extensive revision of the AFM technique, read7,8,9.
This protocol outlines a basic sample preparation method and a general method for AFM-based elasticity measurements of plant cell walls.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63533/63533fig01v2.jpg" /> 
Figure 1: Schematic overview of force-indentation experiment in Arabidopsis roots using atomic force microscopy (AFM). The scheme gives an overview of the steps of a Force-Indentation experiment from the preparation of the substrate to immobilize the root sample firmly (1-2), root viability confirmation through propidium iodide staining (3), cantilever positioning on the surface of an elongated epidermal cell of the primary root (4-5), force curves measurement (6), and force curve processing to calculate the apparent Young&#39;s modulus (7-8). EZ: elongation zone. <a href="https://www.jove.com/files/ftp_upload/63533/63533fig01largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1 x Phosphate-Buffered Saline (PBS)</td>
			<td></td>
			<td></td>
			<td>Include sodium chloride and phosphate buffer and is formulated to prevent osmotic shock and maintain water balance in living cells.</td>
		</tr>
		<tr>
			<td>AFM software</td>
			<td>Bruker, Billerica, MA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Atomic force microscopy (AFM)</td>
			<td>BioScope Catalyst, Bruker, Billerica, MA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Catalyst Probe holder-fluid</td>
			<td>Bruker, Billerica, MA, USA</td>
			<td>CAT-FCH</td>
			<td>A probe holder for the Bioscope Catalyst, designed for fluid operation in contact or Tapping Mode.&#160; Also compatible with air operation.</td>
		</tr>
		<tr>
			<td>Cryoscopic osmometer; model OSMOMAT 030</td>
			<td>Gonotech, Berlin, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Murashige &#38; Skoog Medium</td>
			<td>Duchess Biochemie</td>
			<td>M0221</td>
			<td>Original concentration, (1962)</td>
		</tr>
		<tr>
			<td>Optical inverted microscope coupled to the AFM</td>
			<td>Olympus IX81, Miami, FL, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PEGAMIL</td>
			<td>ANAEROBICOS S.R.L., Buenos Aires, Argentina</td>
			<td>100429</td>
			<td>Neutral, non acidic silicone glue</td>
		</tr>
		<tr>
			<td>Petri dishes</td>
			<td>Deltalab</td>
			<td>200201.B</td>
			<td>Polystyrene, 55 x 14 mm, radiation sterile.</td>
		</tr>
		<tr>
			<td>Propidium iodide</td>
			<td>Sigma</td>
			<td>P4170</td>
			<td>For root viability test.</td>
		</tr>
		<tr>
			<td>Silicon nitride probe, DNP-10, cantilever A</td>
			<td>Bruker, Billerica, MA, USA</td>
			<td>DNP-10/A</td>
			<td>For force modulation microscopy in liquid operation. Probe tip radius of 20-60 nm. 175-&#956;m-long triangular cantilever,&#160; with a spring constant of 0.35 N/m.</td>
		</tr>
		<tr>
			<td>Tweezers</td>
			<td>Sigma</td>
			<td>T4537</td>
			<td></td>
		</tr>
	</tbody>
</table>

atomic force microscopy to study the physical properties of epidermal cells of live arabidopsis roots

A method is described here to characterize the physical properties of the cell wall of epidermal cells of living Arabidopsis roots through nanoindentations with an atomic force microscope (AFM) coupled with an optical inverted fluorescence microscope. The method consists of applying controlled forces to the sample while measuring its deformation, allowing quantifying parameters such as the apparent Young's modulus of cell walls at subcellular resolutions. It requires a careful mechanical immobilization of the sample and correct selection of indenters and indentation depths. Although it can be used only in external tissues, this method allows characterizing mechanical changes in plant cell walls during development and enables the correlation of these microscopic changes with the growth of an entire organ.

Force-Indentation experiments 
The following text presents some results expected when a force-indentation experiment is conducted to show the typical output to expect when the protocol is well executed.
Force-displacement curves 
Representative force indentation plots that were obtained indenting live samples at a position placed in the center of the cell of the root elongation zone are presented in Figure 2. When the AF...

Watch this Scientific Journal Video about Atomic Force Microscopy to Study the Physical Properties of Epidermal Cells of Live Arabidopsis Roots at JoVE.com

Atomic Force Microscopy to Study the Physical Properties of Epidermal Cells of Live Arabidopsis Roots

The atomic force microscopy indentation protocol offers the possibility to dissect the role of the physical properties of the cell wall of a particular cell of a tissue or organ during normal or constrained growth (i.e., under water deficit).

Atomic Force Microscopy to Study the Physical Properties of Epidermal Cells of Live Arabidopsis Roots

A method is described here to characterize the physical properties of the cell wall of epidermal cells of living Arabidopsis roots through ...

This method allows to quantify changes in the physical properties of the plant cell wall during development and relate this microscopic changes to the growth of an entire organ. The main advantage of this technique is that it's not invasive and it does not require any treatment that allows the in vivo quantification of physical properties of the cell wall add subcellular resolution relatively rapid. To begin, spread a thin layer of silicone glue into the Petri dish with a cover slip and leave it in the air for 45 seconds.Using tweezers, place the seedling on the glue and orient its direction to avoid contact between the seedling's protruding parts, and the cantilever. Then press the root gently to the silicone glue layer to bind it firmly. Leave it for 45 seconds, and add the 1X PBS solution.Mount the standard silicon nitride cantilever with a pyramidal tip into the AFM probe holder for fluid, and align the laser on the cantilever close to the position of the tip. Then move the photo diode to place the laser spot at the center of the detector. Calibrate the deflection sensitivity by performing an indentation with a ramp size of 3 micrometers, an indentation and retraction rate of 0.6 micrometers per second and a trigger threshold of 0.5 volts.Ensure that the probe is not interacting with the sample and calibrate the cantilever's spring constant. Using the thermal tune utility, click on calibrate followed by thermal tune or on the thermal tune icon in the nano scope toolbar and enter the cantilever temperature. After selecting a frequency range, click on the sample harmonic oscillator fluid button.Next, click on acquired data in the thermal tune panel. Now, adjust median filter width to three. Adjust PSD binwidth to reduce the noise in the acquired data by averaging and set fit boundaries around the first resonance peak.Click on calculate spring constant K, and then click on yes in the pop-up window, asking if the user wants to use this value. Using the inverted optical microscope at 10, 20 and 40 times eye piece magnification, position the AFM probe on the surface of the fourth elongated epidermal cell of the primary root ensuring to position it in the center of the cell. With the previously calculated spring constant value obtained force curves with a ramp size of 3 micrometers, a trigger threshold of 11 nanonewton, and an indentation and retraction rate of 0.6 micrometers per second at selected points.Obtain force curves from three cells per root for each treatment and capture at least 150 force curves for each root. This plot shows an expected result when a force indentation experiment is conducted on live samples positioned at the center of the cell of the root elongation zone. When the AFM tip starts to indent, the surface of the cell wall, the force begins to increase because of the cell wall opposition to the defamation.The increase of force continues until the maximum force value is reached. After this point, the unloading part of the indentation begins. The force grows following a parabola in the indentation part, which is important to fit each curve to the prediction model for pyramidal indenters used for calculations.As a fitting parameter, the contact point position should correspond to the cell wall surface before indentation and is considered the origin of the AFM tip displacement. Force curves in which it is impossible to detect the point of contact before the indentation should be discarded. Further, the loading and unloading curve of the force indentation experiment must be devoid of noise.After fitting each force curve to the model, histograms were obtained that showed the distribution of the frequency of the obtained values of the apparent Young's modulus. This histogram shows the frequency obtained with a set of 201 successful indentations on nine different cells of three different plants of Columbia Zero grown in control conditions. Indentation could be difficult for some genotypes due to the morphology of the root.For example, the TTL 1 PRC 1-1 double mutant grown in severe osmotic stress. These histograms show the probability distribution of the obtained values of the apparent Young's modulus from nine different cells. Only histogram H that corresponds to one cell could be fitted to a Gaussian distribution.The metal presented here could be combined with other techniques such as grow rate studies or analysis of the chemical composition of the cell wall. These other techniques will further complement information to understand how the chemical composition on the physical properties of the cell wall affect the growth of an organ.

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Developmental Biology

1.9K visualizações.  Universidad de la República (UdelaR). Este método permite quantificar as mudanças nas propriedades físicas da parede celular da planta durante o desenvolvimento e relacionar essas mudanças microscópicas com o crescimento de um órgão inteiro. A principal vantagem desta técnica é que não é invasiva e não requer nenhum tratamento que permita a quantificação in vivo das propriedades físicas da parede celular adicionar resolução subcelular relativamente rápida. Para começar, espalhe uma fina camada de cola de silico...