Name: micron-scale phenotyping techniques of maize vascular bundles based on x-ray microcomputed tomography
Uploaded: 2018-10-09T15:00:00
Description: Watch this Scientific Journal Video about Micron-scale Phenotyping Techniques of Maize Vascular Bundles Based on X-ray Microcomputed Tomography at JoVE.com

This research was supported by the National Nature Science Foundation of China (No.31671577), the Science and Technology Innovation Special Construction Funded Program of Beijing Academy of Agriculture and Forestry Sciences(KJCX20180423), the Research Development Program of China (2016YFD0300605-01), the Beijing Natural Science Foundation (5174033), the Beijing Postdoctoral Research Foundation (2016 ZZ-66), and the Beijing Academy of Agricultural and Forestry Sciences Grant (KJCX20170404), (JNKYT201604).

1. Sample Preparation Protocol
<ol>
	<li>For the sampling, collect the stem, leaf, and root from fresh maize plants and divide them into three types of sample groups (each group with four replications). Then, cut them into small segments using a surgical blade in the following manner: (1) cut a segment of the middle stem internode 1 - 1.5 cm in length; (2) cut a segment of the maximum width of the leaf 0.5 - 3 cm in length along the vertical direction with the main vein; (3) cut a segment of the crown root 0.5 cm in le...

<ol>
	<li>Lucas, W. J., 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+plant+vascular+system:+evolution,+development+and+functions.">The plant vascular system: evolution, development and functions.</a> Journal of Integrative Plant Biology. 55, 294-388 (2013).</li><li>Gou, L., 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=Effect+of+population+density+on+stalk+lodging+resistant+mechanism+and+agronomic+characteristics+of+maize.">Effect of population density on stalk lodging resistant mechanism and agronomic characteristics of maize.</a> Acta Agronomica Sinia. 33, 1688-1695 (2007).</li><li>Hu, H., 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=QTL+mapping+of+stalk+bending+strength+in+a+recombinant+inbred+line+maize+population.">QTL mapping of stalk bending strength in a recombinant inbred line maize population.</a> Theoretical and Applied Genetics. 126, 2257-2266 (2013).</li><li>Wilson, J. R., Mertens, D. R., Hatfield, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolates+of+cell+types+from+sorghum+stems:+Digestion,+cell+wall+and+anatomical+characteristics.">Isolates of cell types from sorghum stems: Digestion, cell wall and anatomical characteristics.</a> Journal of the Science of Food and Agriculture. 63, 407-417 (1993).</li><li>Hatfield, R., Wilson, J., Mertens, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Composition+of+cell+walls+isolated+from+cell+types+of+grain+sorghum+stems.">Composition of cell walls isolated from cell types of grain sorghum stems.</a> Journal of the Science of Food and Agriculture. 79, 891-899 (1999).</li><li>Du, J., 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=Micron-scale+phenotyping+quantification+and+three-dimensional+microstructure+reconstruction+of+vascular+bundles+within+maize+stems+based+on+micro-CT+scanning.">Micron-scale phenotyping quantification and three-dimensional microstructure reconstruction of vascular bundles within maize stems based on micro-CT scanning.</a> Functional Plant Biology. 44 (1), 10-22 (2016).</li><li>Pan, X., 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=Reconstruction+of+Maize+Roots+and+Quantitative+Analysis+of+Metaxylem+Vessels+based+on+X-ray+Micro-Computed+Tomography.">Reconstruction of Maize Roots and Quantitative Analysis of Metaxylem Vessels based on X-ray Micro-Computed Tomography.</a> Canadian Journal of Plant Science. 98 (2), 457-466 (2018).</li><li>McElrone, A. J., Choat, B., Parkinson, D. Y., MacDowell, A. A., Brodersen, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+high+resolution+computed+tomography+to+visualize+the+three+dimensional+structure+and+function+of+plant+vasculature.">Using high resolution computed tomography to visualize the three dimensional structure and function of plant vasculature.</a> Journal of Visualized Experiments. (74), e50162 (2013).</li><li>Cloetens, P., Mache, R., Schlenker, M., Lerbs-Mache, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+phase+tomography+of+Arabidopsis+seeds+reveals+intercellular+void+network.">Quantitative phase tomography of Arabidopsis seeds reveals intercellular void network.</a> Proceedings of the National Academy of Sciences of the Unites States of America. 103, 14626-14630 (2006).</li><li>Dorca-Fornell, C., 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=Increased+leaf+mesophyll+porosity+following+transient+retinoblastoma-related+protein+silencing+is+revealed+by+microcomputed+tomography+imaging+and+leads+to+a+system-level+physiological+response+to+the+altered+cell+division+pattern.">Increased leaf mesophyll porosity following transient retinoblastoma-related protein silencing is revealed by microcomputed tomography imaging and leads to a system-level physiological response to the altered cell division pattern.</a> Plant Journal. 76 (6), 914-929 (2013).</li><li>Verboven, P., 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=Void+space+inside+the+developing+seed+of+Brassica+napus+and+the+modelling+of+its+function.">Void space inside the developing seed of Brassica napus and the modelling of its function.</a> New Phytologist. 199, 936-947 (2013).</li><li>Brodersen, C. R., Roark, L. C., Pittermann, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+physiological+implications+of+primary+xylem+organization+in+two+ferns.">The physiological implications of primary xylem organization in two ferns.</a> Plant, Cell &amp; Environment. 35, 1898-1911 (2012).</li><li>Choat, B., Brodersen, C. R., McElrone, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synchrotron+X-ray+microtomography+of+xylem+embolism+in+Sequoia+sempervirens+saplings+during+cycles+of+drought+and+recovery.">Synchrotron X-ray microtomography of xylem embolism in Sequoia sempervirens saplings during cycles of drought and recovery.</a> New Phytologist. 205, 1095-1105 (2015).</li><li>Torres-Ruiz, J. 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=Direct+x-ray+microtomography+observation+confirms+the+induction+of+embolism+upon+xylem+cutting+under+tension.">Direct x-ray microtomography observation confirms the induction of embolism upon xylem cutting under tension.</a> Plant Physiology. 167, 40-43 (2015).</li><li>Staedler, Y. M., Masson, D., Sch&#246;nenberger, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+tissues+in+3D+via.+x-ray+tomography:+simple+contrasting+methods+allow+high+resolution+imaging.">Plant tissues in 3D via. x-ray tomography: simple contrasting methods allow high resolution imaging.</a> PLoS One. 8, 75295 (2013).</li><li>Zhang, Y., Legay, S., Barri&#232;re, Y., M&#233;chin, V., Legland, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Color+quantification+of+stained+maize+stem+section+describes+lignin+spatial+distribution+within+the+whole+stem.">Color quantification of stained maize stem section describes lignin spatial distribution within the whole stem.</a> Journal of the Science of Food and Agriculture. 61, 3186-3192 (2013).</li><li>Legland, D., Devaux, M. F., Guillon, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+mapping+of+maize+bundle+intensity+at+the+stem+scale+using+spatial+normalisation+of+replicated+images.">Statistical mapping of maize bundle intensity at the stem scale using spatial normalisation of replicated images.</a> PLoS One. 9 (3), 90673 (2014).</li><li>Heckwolf, S., Heckwolf, M., Kaeppler, S. M., de Leon, N., Spalding, E. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Image+analysis+of+anatomical+traits+in+stem+transections+of+maize+and+other+grasses.">Image analysis of anatomical traits in stem transections of maize and other grasses.</a> Plant Methods. 11, 26 (2015).</li><li>Wu, H., Jaeger, M., Wang, M., Li, B., Zhang, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+distribution+of+vessels,+passage+cells+and+lateral+roots+along+the+root+axis+of+winter+wheat+(Triticum+aestivum).">Three-dimensional distribution of vessels, passage cells and lateral roots along the root axis of winter wheat (Triticum aestivum).</a> Annals of Botany. 107, 843-853 (2011).</li><li>Chopin, J., Laga, H., Huang, C. Y., Heuer, S., Miklavcic, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RootAnalyzer:+A+Cross-Section+Image+Analysis+Tool+for+Automated+Characterization+of+Root+Cells+and+Tissues.">RootAnalyzer: A Cross-Section Image Analysis Tool for Automated Characterization of Root Cells and Tissues.</a> PLoS One. 10, 0137655 (2015).</li><li>Passot, S., 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=Characterization+of+pearl+millet+root+architecture+and+anatomy+reveals+three+types+of+lateral+roots.">Characterization of pearl millet root architecture and anatomy reveals three types of lateral roots.</a> Frontiers in Plant Science. 7, 829 (2016).</li></ol>

With the successful application of CT technology in the fields of biomedicine and materials science, this technology has been gradually introduced into the fields of botany and agriculture, promoting researches in plant life sciences as a promising technical tool. In the late 1990s, CT technology was first used to study the morphological structures and development of plant root systems. In the past decade, synchrotron HRCT has become a powerful, nondestructive tool for plant biologists, and has been successfully used to ...

The maize vascular system runs through the entire plant, from the root and stem to the leaves, which forms the key transportation paths for delivering water, mineral nutrients, and organic substances1. Another important function of the vascular system is to provide mechanical support for the maize plant. For example, the morphology, number, and distribution of vascular bundles in roots and stems are closely related to the lodging resistance of maize plants2,3. At present, studies on the anatomical structure of vascular bundles mainly utilize microscopic and ultramicroscopic techniques to display the anatomical structures of a certain part of the stem, leaf, or root, and then measure and count these structures of interest by manual investigation. Undoubtedly, manual measurement of various microscopic structures in large-scale microimages is a very tedious and inefficient work and severely limits the precision of microphenotypic traits, owing to its subjectivity and inconsistency4,5.
Maize has no secondary growth, and the cell content essentially consists of water in the primary meristem. Without any pretreatment, fresh samples of maize tissues can be directly scanned using a micro-CT device; however, the scanning results are probably poor and rough. The main reasons are summarized as follows: (1) low attenuation densities of plant tissues, resulting in a low contrast of atomic number and high noise in images; (2) fresh plant materials are prone to dehydrate and shrink during the normal scanning environment, as reported by Du6. The abovementioned problems have become the main constraints for the development and application of microphenotyping technology for maize, wheat, rice, and other monocotyledons. Here, we introduce the &#39;sample preparation protocol&#39; to pretreat the samples of maize stem, leaf, and root. This protocol avoids the dehydration and deformation of plant materials during the CT scanning; thus, it is beneficial to increase the preservation time of plant samples with nondeformation. Moreover, the dyeing step based on solid iodine also enhances the contrast of plant materials; thus, it makes significant improvements in the imaging quality of micro-CT. Furthermore, we developed image processing software, named VesselParser, to process the CT images of maize stems and leaves. This software integrates a set of image-processing pipelines to perform high-throughput and automatic phenotyping analysis for 2-D CT images of different plant tissues. Vascular bundles in the entire cross-section of the maize stem and leaf are detected, extracted, and identified using an automatic image-processing method. As a result, we obtain 31 microscopic phenotypes of the maize stem and 33 microscopic phenotypes of the maize leaf. For the CT image series of the maize root, we developed an image-processing scheme to acquire 3-D phenotypic traits of metaxylem vessels. This scheme is superior in efficiency of image acquisition and reconstruction compared with traditional methods.
These results indicate that the image processing pipelines considering the imaging characteristics of ordinary X-ray micro-CT provide an effective method for the microscopic phenotyping of vascular bundles; this extremely widens the applications of CT techniques in plant science and improves the automatic phenotyping of plant materials at cellular resolution6,7.

<table border="0" cellpadding="0" cellspacing="0" style="width:841px;" width="841">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Skyscan 1172 X-ray computed tomography system</td>
			<td style="width:269px;">Bruker Corporation, Belgium</td>
			<td style="width:119px;">NA</td>
			<td style="width:237px;">For CT scanning</td>
		</tr>
		<tr height="46">
			<td height="46" style="height:46px;width:216px;">CO2 critical point drying system (Leica CPD300)</td>
			<td style="width:269px;">Leica Corporation, Germany</td>
			<td style="width:119px;">NA</td>
			<td style="width:237px;">For sample drying</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td>For FAA fixation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Formaldehyde</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td>For FAA fixation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Acetic acid</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td>For FAA fixation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Surgical blade</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td>For cutting the sample sgements</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">3D printer</td>
			<td style="width:269px;">Makerbot replicator 2, MakerBot Industries, USA</td>
			<td style="width:119px;">NA</td>
			<td>For printing the sample baskets of maize root, stem, and leaf</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge tube</td>
			<td style="width:269px;">Corning, USA</td>
			<td style="width:119px;">NA</td>
			<td>Place the root, stem, or leaf materials</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Solid iodine</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td>For sample dyeing</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">SkyScan Nrecon software</td>
			<td style="width:269px;">SkyScan NRecon, Version: 1.6.9.4, Bruker Corporation, Belgium</td>
			<td style="width:119px;">NA</td>
			<td>For image reconstruction</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">VesselParser software</td>
			<td style="width:269px;">VesselParser, Version: 3.0, National Engineering Research Center for Information Technology in Agriculture (NERCITA), Beijing, China</td>
			<td style="width:119px;">NA</td>
			<td>Image analysis protocol for single CT image of maize stem or leaf</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">ScanIP</td>
			<td style="width:269px;">ScanIP, Version: 7.0; Simpleware, Exeter, UK</td>
			<td style="width:119px;">NA</td>
			<td>3D image processing software</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Latex gloves</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tweezers</td>
			<td style="width:269px;">Any</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
	</tbody>
</table>

micron-scale phenotyping techniques of maize vascular bundles based on x-ray microcomputed tomography

It is necessary to accurately quantify the anatomical structures of maize materials based on high-throughput image analysis techniques. Here, we provide a 'sample preparation protocol' for maize materials (i.e., stem, leaf, and root) suitable for ordinary microcomputed tomography (micro-CT) scanning. Based on high-resolution CT images of maize stem, leaf, and root, we describe two protocols for the phenotypic analysis of vascular bundles: (1) based on the CT image of maize stem and leaf, we developed a specific image analysis pipeline to automatically extract 31 and 33 phenotypic traits of vascular bundles; (2) based on the CT image series of maize root, we set up an image processing scheme for the three-dimensional (3-D) segmentation of metaxylem vessels, and extracted two-dimensional (2-D) and 3-D phenotypic traits, such as volume, surface area of metaxylem vessels, etc. Compared with traditional manual measurement of vascular bundles of maize materials, the proposed protocols significantly improve the efficiency and accuracy of micron-scale phenotypic quantification.

The sample preparation protocol suitable for ordinary micro-CT scanning not only prevents the deformation of plant tissues but also enhances the X-ray absorption contrast. Pretreated plant materials are scanned using a micro-CT system into high-quality slice images, and the highest resolution can reach 2 &#181;m/pixel. Figure 4 shows the scanned micro-CT images of stem, leaf, and root, and the image contrast has a significant improvement compared with the res...

Watch this Scientific Journal Video about Micron-scale Phenotyping Techniques of Maize Vascular Bundles Based on X-ray Microcomputed Tomography at JoVE.com

Micron-scale Phenotyping Techniques of Maize Vascular Bundles Based on X-ray Microcomputed Tomography

We provide a novel method to improve the X-ray absorption contrast of maize tissue suitable for ordinary microcomputed tomography scanning. Based on CT images, we introduce a set of image-processing workflows for different maize materials to effectively extract microscopic phenotypes of vascular bundles of maize.

It is necessary to accurately quantify the anatomical structures of maize materials based on high-throughput image analysis techniques. Here, we provide a ...

This method can have answer quick questions in the planned micron-scale phenotyping techniques build. Such as micro-CT scanning particles, and the phenotypic analysis method for maize vascular bundles. The main advantage of this technique is to provide new and effective ways to investigate phenotypical traits of maize vascular bundle by sample preparation, CT scanning, and analysis of protocols.The implications of this technique broadens applications of ordinary micro-CT scanning and other plant sciences. This protocol can be easily modified to accommodate other plant materials, such as dehydration of drying procedure. To begin, collect the stem, leaf, and root from fresh maize plants.And divide them into three sample groups. Next, use a surgical blade to cut a one to 1.5 centimeter segment of the middle stem internode. Using the same surgical blade, cut a 1/2 to two centimeter segment from the maximum width of the leaf along the vertical direction with the main vein.Use the surgical blade to cut a 1/2 centimeter segment from the ground root. After this, soak the sample segments in FAA solution for at least three days. Dehydrate the sample segments for 30 minutes in six sequential ethanol gradients.Then place the plant materials in the corresponding sample baskets. Quickly transfer the baskets to the sample cell of a carbon dioxide critical point drying system. Place the dried plant materials into a 50 milliliter centrifuge tube with two grams of solid iodine.Then place the tubes in a light-proof room for four to five hours. First, set the CT scanning parameters according to the text protocol. Then, set the scanning ranges according to the different sizes and volumes of the plant materials used.Next, adjust the imaging pixel sizes as follows:Two micrometers for the root. 6.77 micrometers for the stem. And 10 micrometers for the leaf.To reconstruct slice images, use imagery construction software to convert the raw CT data into CT slice images with 2K resolution. First, specify the organ type to initialize different algorithm pipelines in the automatic imaging software. Then, click the method parameters button and select maize stem, or maize leaf, in the first drop-down box.Click the data management button, set the work directory, and import all of slice images in the directory. Then select single or multi-slice images into the image pipelines. Next, determine the pixel size of the image.Pick the method parameters button and enter the pixel size of the image in the appropriate edit item. After this, click the phenotyping computation button to automatically extract phenotypic traits of the vascular bundles for all of the selected slice images. Click the statistical analysis button to output the results of these analysis as a text or CSV file.Import the reconstructed images of maize roots, and determine the accurate space parameters. Then use the recursive gaussian tool to smooth the images, and improve image quality. Adjust the threshold parameters to conduct 3D segmentation of metaxylem vessels.This will create a uniform color label for each connected metaxylem vessel. Then, improve and identify the metaxylem vessels interactively using morphology bitwise, and flood-fill operations. Next, conduct a volume visualization and surface reconstruction of the vessels.Finally, use the mask statistics tool to count and measure the phenotypic traits of a vessel at the 2D and 3D levels. Using the analysis outlined in the protocol, the phenotypic traits of vascular bundles in maize stems, leaves, and roots were computed. A generated 3D visualization of the root and metaxylem vessels was created, using the results of segmentation, reconstruction, and volume visualization.The proper sample preparation protocol significantly improves the scanning emitting quality of micro-CT for maize stem, leaf, and root. With the automatic emit pipeline to rapidly extract the phenotypical traits of vascular bundles for maize stem and leaf. And the setup and emit processing scan to analyze the 3D phenotypic traits of vascular bundles for maize root.This technique provides a practical way for accurate and rapid phenotypic qualification and identification of maize vascular bundles.

micron-scale-phenotyping-techniques-maize-vascular-bundles-based-on-x

Research

JoVE Journal

Biology

Non-invasive 3D-Visualization with Sub-micron Resolution Using Synchrotron-X-ray-tomography

Little is known about the internal organization of many micro-arthropods with body sizes below 1 mm. The reasons for that are the small size and the hard cuticle which makes it difficult to use protocols of classical histology. In addition, histological sectioning destroys the sample and can therefore not be used for unique material. Hence, a non-destructive method is desirable which allows to view inside small samples without the need of sectioning.
We used synchrotron X-ray tomography at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France) to non-invasively produce 3D tomographic datasets with a pixel-resolution of 0.7&micro;m. Using volume rendering software, this allows us to reconstruct the internal organization in its natural state without the artefacts produced by histological sectioning. These date can be used for quantitative morphology, landmarks, or for the visualization of animated movies to understand the structure of hidden body parts and to follow complete organ systems or tissues through the samples.

We used synchrotron X-ray tomography at the European Synchrotron Radiation Facility (ESRF) to non-invasively produce 3D tomographic datasets with a pixel-resolution of 0.7&micro;m. Using volume rendering software, this allows the reconstruction of internal structures in their natural state without the artefacts produced by histological sectioning.

Little is known about the internal organization of many micro-arthropods with body sizes below 1 mm. The reasons for that are the small size and the hard ...

Protein Crystallization for X-ray Crystallography

Using the three-dimensional structure of biological macromolecules to infer how they function is one of the most important fields of modern biology. The availability of atomic resolution structures provides a deep and unique understanding of protein function, and helps to unravel the inner workings of the living cell. To date, 86% of the Protein Data Bank (rcsb-PDB) entries are macromolecular structures that were determined using X-ray crystallography.
To obtain crystals suitable for crystallographic studies, the macromolecule (e.g. protein, nucleic acid, protein-protein complex or protein-nucleic acid complex) must be purified to homogeneity, or as close as possible to homogeneity. The homogeneity of the preparation is a key factor in obtaining crystals that diffract to high resolution (Bergfors, 1999; McPherson, 1999).
Crystallization requires bringing the macromolecule to supersaturation. The sample should therefore be concentrated to the highest possible concentration without causing aggregation or precipitation of the macromolecule (usually 2-50 mg/ mL). Introducing the sample to precipitating agent can promote the nucleation of protein crystals in the solution, which can result in large three-dimensional crystals growing from the solution. There are two main techniques to obtain crystals: vapor diffusion and batch crystallization. In vapor diffusion, a drop containing a mixture of precipitant and protein solutions is sealed in a chamber with pure precipitant. Water vapor then diffuses out of the drop until the osmolarity of the drop and the precipitant are equal (Figure 1A). The dehydration of the drop causes a slow concentration of both protein and precipitant until equilibrium is achieved, ideally in the crystal nucleation zone of the phase diagram. The batch method relies on bringing the protein directly into the nucleation zone by mixing protein with the appropriate amount of precipitant (Figure 1B). This method is usually performed under a paraffin/mineral oil mixture to prevent the diffusion of water out of the drop.
Here we will demonstrate two kinds of experimental setup for vapor diffusion, hanging drop and sitting drop, in addition to batch crystallization under oil.

The 3-D structure of a molecule provides a unique understanding of how the molecule functions. The principal method for structure determination at near-atomic resolution is X-ray crystallography. Here, we demonstrate the current methods for obtaining three-dimensional crystals of any given macromolecule that are suitable for structure determination by X-ray crystallography.

Using the three-dimensional structure of biological macromolecules to infer how they function is one of the most important fields of modern biology. The ...

3D Printing of Preclinical X-ray Computed Tomographic Data Sets

Three-dimensional printing allows for the production of highly detailed objects through a process known as additive manufacturing. Traditional, mold-injection methods to create models or parts have several limitations, the most important of which is a difficulty in making highly complex products in a timely, cost-effective manner.1 However, gradual improvements in three-dimensional printing technology have resulted in both high-end and economy instruments that are now available for the facile production of customized models.2 These printers have the ability to extrude high-resolution objects with enough detail to accurately represent in vivo images generated from a preclinical X-ray CT scanner. With proper data collection, surface rendering, and stereolithographic editing, it is now possible and inexpensive to rapidly produce detailed skeletal and soft tissue structures from X-ray CT data. Even in the early stages of development, the anatomical models produced by three-dimensional printing appeal to both educators and researchers who can utilize the technology to improve visualization proficiency. 3, 4 The real benefits of this method result from the tangible experience a researcher can have with data that cannot be adequately conveyed through a computer screen. The translation of pre-clinical 3D data to a physical object that is an exact copy of the test subject is a powerful tool for visualization and communication, especially for relating imaging research to students, or those in other fields. Here, we provide a detailed method for printing plastic models of bone and organ structures derived from X-ray CT scans utilizing an Albira X-ray CT system in conjunction with PMOD, ImageJ, Meshlab, Netfabb, and ReplicatorG software packages.

Using modern plastic extrusion and printing technologies, it is now possible to quickly and inexpensively produce physical models of X-ray CT data taken in a laboratory. The three -dimensional printing of tomographic data is a powerful visualization, research, and educational tool that may now be accessed by the preclinical imaging community.

Three-dimensional printing allows for the production of highly detailed objects through a process known as additive manufacturing.  Traditional, ...

Production of Human Norovirus Protruding Domains in E. coli for X-ray Crystallography

The norovirus capsid is composed of a single major structural protein, termed VP1. VP1 is subdivided into a shell (S) domain and a protruding (P) domain. The S domain forms a contiguous scaffold around the viral RNA, whereas the P domain forms viral spikes on the S domain and contains determinants for antigenicity and host-cell interactions. The P domain binds carbohydrate structures, i.e., histo-blood group antigens, which are thought to be important for norovirus infections. In this protocol, we describe a method for producing high quality norovirus P domains in high yields. These proteins can then be used for X-ray crystallography and ELISA in order to study antigenicity and host-cell interactions.
The P domain is firstly cloned into an expression vector and then expressed in bacteria. The protein is purified using three steps that involve immobilized metal-ion affinity chromatography and size exclusion chromatography. In principle, it is possible to clone, express, purify, and crystallize proteins in less than four weeks, which makes this protocol a rapid system for analyzing newly emerging norovirus strains.

Production of Human Norovirus Protruding Domains in E. coli for X-ray Crystallography

Here, we describe a method to express and purify high quality norovirus protruding (P) domains in E. coli for use in X-ray crystallography studies. This method can be applied to other calicivirus P domains, as well as non-structural proteins, i.e., viral protein genome-linked (VPg), protease, and RNA dependent RNA polymerase (RdRp).

The norovirus capsid is composed of a single major structural protein, termed VP1. VP1 is subdivided into a shell (S) domain and a protruding (P) domain. ...

Techniques to Induce and Quantify Cellular Senescence

In response to cellular stress or damage, proliferating cells can induce a specific program that initiates a state of long-term cell-cycle arrest, termed cellular senescence. Accumulation of senescent cells occurs with organismal aging and through continual culturing in vitro. Senescent cells influence many biological processes, including embryonic development, tissue repair and regeneration, tumor suppression, and aging. Hallmarks of senescent cells include, but are not limited to, increased senescence-associated &#946;-galactosidase activity (SA-&#946;-gal); p16INK4A, p53, and p21 levels; higher levels of DNA damage, including &#947;-H2AX; the formation of Senescence-associated Heterochromatin Foci (SAHF); and the acquisition of a Senescence-associated Secretory Phenotype (SASP), a phenomenon characterized by the secretion of a number of pro-inflammatory cytokines and signaling molecules. Here, we describe protocols for both replicative and DNA damage-induced senescence in cultured cells. In addition, we highlight techniques to monitor the senescent phenotype using several senescence-associated markers, including SA-&#946;-gal, &#947;-H2AX and SAHF staining, and to quantify protein and mRNA levels of cell cycle regulators and SASP factors. These methods can be applied to the assessment of senescence in various models and tissues.

Cellular senescence, the irreversible state of cell-cycle arrest, can be induced by various cellular stresses. Here, we describe protocols to induce cellular senescence and methods to assess markers of senescence.

In response to cellular stress or damage, proliferating cells can induce a specific program that initiates a state of long-term cell-cycle arrest, termed ...

SA-&#946;-Galactosidase-Based Screening Assay for the Identification of Senotherapeutic Drugs

Cell senescence is one of the hallmarks of aging known to negatively influence a healthy lifespan. Drugs able to kill senescent cells specifically in cell culture, termed senolytics, can reduce the senescent cell burden in vivo and extend healthspan. Multiple classes of senolytics have been identified to date including HSP90 inhibitors, Bcl-2 family inhibitors, piperlongumine, a FOXO4 inhibitory peptide and the combination of Dasatinib/Quercetin. Detection of SA-&#946;-Gal at an increased lysosomal pH is one of the best characterized markers for the detection of senescent cells. Live cell measurements of senescence-associated &#946;-galactosidase (SA-&#946;-Gal) activity using the fluorescent substrate C12FDG in combination with the determination of the total cell number using a DNA intercalating Hoechst dye opens the possibility to screen for senotherapeutic drugs that either reduce overall SA-&#946;-Gal activity by killing of senescent cells (senolytics) or by suppressing SA-&#946;-Gal and other phenotypes of senescent cells (senomorphics). Use of a high content fluorescent image acquisition and analysis platform allows for the rapid, high throughput screening of drug libraries for effects on SA-&#946;-Gal, cell morphology and cell number.

SA-&amp;#946;-Galactosidase-Based Screening Assay for the Identification of Senotherapeutic Drugs

Cellular senescence is the key factor in the development of chronic age-related pathologies. Identification of therapeutics that target senescent cells show promise for extending healthy aging. Here, we present a novel assay to screen for the identification of senotherapeutics based on measurement of senescence associated &#946;-Galactosidase activity in single cells.

Cell senescence is one of the hallmarks of aging known to negatively influence a healthy lifespan. Drugs able to kill senescent cells specifically in cell ...

Dosimetry for Cell Irradiation using Orthovoltage (40-300 kV) X-Ray Facilities

The importance of dosimetry protocols and standards for radiobiological studies is self-evident. Several protocols have been proposed for dose determination using low energy X-ray facilities, but depending on the irradiation configurations, samples, materials or beam quality, it is sometimes difficult to know which protocol is the most appropriate to employ. We, therefore, propose a dosimetry protocol for cell irradiations using low energy X-ray facility. The aim of this method is to perform the dose estimation at the level of the cell monolayer to make it as close as possible to real cell irradiation conditions. The different steps of the protocol are as follows: determination of the irradiation parameters (high voltage, intensity, cell container etc.), determination of the beam quality index (high voltage-half value layer couple), dose rate measurement with ionization chamber calibrated in air kerma conditions, quantification of the attenuation and scattering of the cell culture medium with EBT3 radiochromic films, and determination of the dose rate at the cellular level. This methodology must be performed for each new cell irradiation configuration as the modification of only one parameter can strongly impact the real dose deposition at the level of the cell monolayer, particularly involving low energy X-rays.

Dosimetry for Cell Irradiation using Orthovoltage 40-300 kV X-Ray Facilities

This document describes a new dosimetry protocol for cell irradiations using low energy X-ray equipment. Measurements are performed in conditions simulating real cell irradiation conditions as much as possible.

The importance of dosimetry protocols and standards for radiobiological studies is self-evident. Several protocols have been proposed for dose ...

Image Rendering Techniques in Postmortem Computed Tomography: Evaluation of Biological Health and Profile in Stranded Cetaceans

With 6 years of experience in implementing virtopsy routinely into the Hong Kong cetacean stranding response program, standardized virtopsy procedures, postmortem computed tomography (PMCT) acquisition, postprocessing, and evaluation were successfully established. In this pioneer cetacean virtopsy stranding response program, PMCT was performed on 193 stranded cetaceans, providing postmortem findings to aid necropsy and shed light on the biological health and profile of the animals. This study aimed to assess 8 image rendering techniques in PMCT, including multiplanar reconstruction, curved planar reformation, maximum intensity projection, minimum intensity projection, direct volume rendering, segmentation, transfer function, and perspective volume rendering. Illustrated with practical examples, these techniques were able to identify most of the PM findings in stranded cetaceans and served as a tool to investigate their biological health and profile. This study could guide radiologists, clinicians and veterinarians through the often difficult and complicated realm of PMCT image rendering and reviewing.

The Hong Kong cetacean stranding response program has incorporated postmortem computed tomography, which provides valuable information on the biological health and profile of the deceased animals. This study describes 8 image rendering techniques that are essential for the identification and visualization of postmortem findings in stranded cetaceans, which will help clinicians, veterinarians and stranding response personnel worldwide to fully utilize the radiological modality.

With 6 years of experience in implementing virtopsy routinely into the Hong Kong cetacean stranding response program, standardized virtopsy procedures, ...

A 3D Cartographic Description of the Cell by Cryo Soft X-ray Tomography

Imaging techniques are fundamental in order to understand cell organization and machinery in biological research and the related fields. Among these techniques, cryo soft X-ray tomography (SXT) allows imaging whole cryo-preserved cells in the water window X-ray energy range (284-543 eV), in which carbon structures have intrinsically higher absorption than water, allowing the 3D reconstruction of the linear absorption coefficient of the material contained in each voxel. Quantitative structural information at the level of whole cells up to 10 &#181;m thick is then achievable this way, with high throughput and spatial resolution down to 25-30 nm half-pitch. Cryo-SXT has proven itself relevant to current biomedical research, providing 3D information on cellular infection processes (virus, bacteria, or parasites), morphological changes due to diseases (such as recessive genetic diseases) and helping us understand drug action at the cellular level, or locating specific structures in the 3D cellular environment. In addition, by taking advantage of the tunable wavelength at synchrotron facilities, spectro-microscopy or its 3D counterpart, spectro-tomography, can also be used to image and quantify specific elements in the cell, such as calcium in biomineralization processes. Cryo-SXT provides complementary information to other biological imaging techniques such as electron microscopy, X-ray fluorescence or visible light fluorescence, and is generally used as a partner method for 2D or 3D correlative imaging at cryogenic conditions in order to link function, location, and morphology.

Here, a protocol describing the sample preparation and data collection steps required in cryo soft X-ray tomography (SXT) to image the ultrastructure of whole cryo-preserved cells at a resolution of 25 nm half pitch, is presented.

Imaging techniques are fundamental in order to understand cell organization and machinery in biological research and the related fields. Among these ...

Directly Measuring Forces Within Reconstituted Active Microtubule Bundles

Microtubule networks are employed in cells to accomplish a wide range of tasks, ranging from acting as tracks for vesicle transport to working as specialized arrays during mitosis to regulate chromosome segregation. Proteins that interact with microtubules include motors such as kinesins and dynein, which can generate active forces and directional motion, as well as non-motor proteins that crosslink filaments into higher-order networks or regulate filament dynamics. To date, biophysical studies of microtubule-associated proteins have overwhelmingly focused on the role of single motor proteins needed for vesicle transport, and significant progress has been made in elucidating the force-generating properties and mechanochemical regulation of kinesins and dyneins. However, for processes in which microtubules act both as cargo and track, such as during filament sliding within the mitotic spindle, much less is understood about the biophysical regulation of ensembles of the crosslinking proteins involved. Here, we detail our methodology for directly probing force generation and response within crosslinked microtubule minimal networks reconstituted from purified microtubules and mitotic proteins. Microtubule pairs are crosslinked by proteins of interest, one microtubule is immobilized to a microscope coverslip, and the second microtubule is manipulated by an optical trap. Simultaneous total internal reflection fluorescence microscopy allows for multichannel visualization of all the components of this microtubule network as the filaments slide apart to generate force. We also demonstrate how these techniques can be used to probe pushing forces exerted by kinesin-5 ensembles and how viscous braking forces arise between sliding microtubule pairs crosslinked by the mitotic MAP PRC1. These assays provide insights into the mechanisms of spindle assembly and function and can be more broadly adapted to study dense microtubule network mechanics in diverse contexts, such as the axon and dendrites of neurons and polar epithelial cells.

Here, we present a protocol for reconstituting microtubule bundles in vitro and directly quantifying the forces exerted within them using simultaneous optical trapping and total internal reflection fluorescence microscopy. This assay allows for nanoscale-level measurement of the forces and displacements generated by protein ensembles within active microtubule networks.