IEM would like to acknowledge the Danish Research Council (FTP and FNU) for funding. ERL acknowledges the support of an ARC DP grant. AB acknowledges the support of the ARC Centre of Excellence in Plant Cell Walls grant.

1. Tissue Collection &amp; Preparation
<ol>
	<li>Collect 100 mg fresh weight of plant tissues (a minimum of 10 mg dry weight) in at least triplicate for each tissue of interest. The following steps describe the preparation of cell wall material from vegetative tissues. In the case of storage tissues, un-wanted starch is enzymatically removed before proceeding with the extraction of cell wall polymers as previously described13.</li>
	<li>Homogenize the samples to a fine powder with liquid nitrogen using a Qiagen TissueLyser II, with 24 tube adapter sets and 3 mm tungsten carbide beads (30 Hz, 2 x 30 sec). Alternatively if only a few samples are being processed, a mortar and pestle is used.</li>
	<li>Transfer the homogenates into 10 ml plastic conical tubes.</li>
	<li>Prepare cell wall material by washing the homogenates in 10 ml 80% v/v ethanol at RT and vortexing vigorously for 2 min.</li>
	<li>Centrifuge samples at 3,500 x g and discard supernatant. Repeat the 70% ethanol washes at least three times or until the supernatant is clear, particularly for tissues containing chlorophyll.</li>
	<li>Perform a final wash with 100% acetone and leave the pellets containing Alcohol Insoluble Residues (AIR) to air-dry overnight.</li>
	<li>Sieve the AIR samples with a 0.4 mm2 mesh to achieve a fine, homogenous powder and to remove larger, poorly ground particles which sometime remain in the homogenate.</li>
	<li>Weigh 10 mg AIR sample into microtubes, each containing a 3 mm glass bead to aid the mixing of samples.</li>
</ol>
2. Extraction of Cell Wall Glycans
<ol>
	<li>Pectins, and polymers associated with pectins are extracted from the samples by adding 500 &mu;l of 50 &mu;M CDTA (pH 7.5) to each sample.</li>
	<li>Briefly vortex the tubes to ensure the solvent is in contact with the sample material and then mix using the TissueLyser for 3 hr at 8 Hz.</li>
	<li>Centrifuge samples at 12,000 x g, carefully remove the supernatants and store at 4 &deg;C.</li>
	<li>Wash pellets in 1 ml of de-ionized water to dilute and remove any remaining solvent, vortex and centrifuge at 13,000 x g. Repeat this step without disturbing the pellet and remove all liquid from the tubes before proceeding to the next step.</li>
	<li>Cross-linking glycans are sequentially extracted from the remaining cell wall pellet with 500 &mu;l of 4M NaOH with 0.1% w/v NaBH4, using the same procedure described in steps 2.1 - 2.4 for the CDTA extraction. NaBH4 is added to reduce the aldehyde (or keto) group at the reducing end of the polysaccharides to an alcohol thereby preventing base peeling of polysaccharides.</li>
	<li>After centrifugation, supernatants are again removed, stored at 4 &deg;C, and the pellets washed twice in de-ionized water before proceeding to the next extraction.</li>
	<li>As an optional step, residual polymers, such as cellulose are extracted with 500 &mu;l cadoxen (31% v/v 1,2-diaminoethane with 0.78 M CdO) using the same procedure as described in steps 2.1 - 2.4. Alternatively, absolute cellulosic content in remaining pellets can be determined using Acetic/Nitric assays (See Discussion).</li>
</ol>
3. Printing Microarrays
<ol>
	<li>Centrifuge supernatants containing extracted cell wall polymers at 13,000 x g to remove any particulate matter.</li>
	<li>Load 50 &mu;l of each sample into a polypropylene 384 well microtiter plate using a pre-designed custom layout where samples are arranged according to tissue type and extraction type.</li>
	<li>Dilute the cell wall polymer sample in a 0, 5 and 25&times; serial dilution series with deionized water.</li>
	<li>Parameters such as pin height, collection and dwell time, and washing steps are set on the software controlling the microarrayer.</li>
	<li>The humidity of the printing chamber is controlled at 60% to prevent sample evaporation.</li>
	<li>The printing job is started using LabNEXT software and a program which corresponds to the microarray layout.</li>
	<li>The robot uses capillary channel pins to print solutions from the sample plate onto 20 x 20 cm nitrocellulose membrane which is attached to a flat plate in the machine. Each spot on the array contains 15 nl of solution and is printed in triplicate.</li>
	<li>Identical microarrays are printed next to each other on the membrane and cut into individual arrays after the print job is complete.</li>
	<li>In each experiment the arrays can be modified in order to accommodate more or less samples, dilutions or replicates.</li>
</ol>
4. Probing of Glycan Microarrays
<ol>
	<li>After printing, block the individual microarrays in 5% w/v skimmed milk powder dissolved in phosphate buffered saline (MPBS) at room temperature for 2 hr to reduce non-specific binding.</li>
	<li>Probe microarrays with monoclonal antibodies specific for cell-wall glycan epitopes for 2 hr in MPBS. The majority of monoclonal antibodies against cell wall glycans are commercially available from three companies; Biosupplies (<a href="http://www.biosupplies.com.au" target="_blank">www.biosupplies.com.au</a>), Carbosource Services (<a href="http://www.carbosource.net" target="_blank">www.carbosource.net</a>) and PlantProbes (<a href="http://www.plantprobes.net" target="_blank">www.plantprobes.net</a>).</li>
	<li>Include a negative control, a microarray incubated with only MPBS and no primary antibody.</li>
	<li>Wash the microarrays 3 times in phosphate buffered saline (PBS) for 5 min to remove non-specific binding.</li>
	<li>Probe the microarrays with secondary antibody conjugated to horseradish peroxidase (HRP) in MPBS for 2 hr. Most monoclonal antibodies against cell wall glycans require anti-mouse or anti-rat secondary antibodies.</li>
	<li>Repeat the washing steps 3 times with PBS buffer for 5 min to remove non-specific binding.</li>
	<li>Develop the microarrays using chromogenic (3,3-Diaminobenzidine) or chemiluminecent (luminol) substrates.</li>
</ol>
5. Quantification
<ol>
	<li>After development, scan the individual microarrays using a high-resolution (1,200 dpi) desktop scanner and save the images as negative, 16-bit TIFF files (Figure 3).</li>
	<li>Calculate the integral intensity of each spot using Xplore Image Processing Software (LabNEXT) fitted with an automated grid tool. The integral spot intensity is derived from the sum of pixels in the grid area surrounding each spot.</li>
	<li>The grid data for each microarray is exported as a txt file and can be manually imported into an Excel spreadsheet for analysis. An online tool (<a href="http://arraytemplates.charliehart.com.au/" target="_blank">http://microarray.plantcell.unimelb.edu.au/</a> ) has been developed to automatically translate and process data from individual txt files.</li>
	<li>The integral spot intensity is averaged across printing replicates and dilutions to obtain a 'mean spot intensity' value for each sample (Figure 2). Alternatively, spot signals corresponding to just one dilution value on the array are used to quantify the relative glycan epitope abundance for each sample.</li>
	<li>The relative mean spot intensities between different samples are presented as a heatmap (Figure 4) using conditional formatting in excel or online heatmapper tools (<a href="http://bar.utoronto.ca/welcome.htm" target="_blank">http://bar.utoronto.ca/welcome.htm</a>). The data for each antibody type is corrected to 100 and a 5% cutoff value is imposed to remove background signal and false positives.</li>
</ol>

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F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UNIT+12.10+Preparation+and+Analysis+of+Glycan+Microarray.">UNIT 12.10 Preparation and Analysis of Glycan Microarray.</a> Current Protocols in Protein Science. , (2011).</li><li>McCartney, L., Blake, A., Flint, 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=Differential+recognition+of+plant+cell+walls+by+microbial+xylan-specific+carbohydrate-binding+modules.">Differential recognition of plant cell walls by microbial xylan-specific carbohydrate-binding modules.</a> PNAS. 103, 4765-4770 (2006).</li><li>Ca&#241;o-Delgado, A. I., Metzlaff, K., Bevan, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+eli1+mutation+reveals+a+link+between+cell+expansion+and+secondary+cell+wall+formation+in+Arabidopsis+thaliana.">The eli1 mutation reveals a link between cell expansion and secondary cell wall formation in Arabidopsis thaliana.</a> Development. 127, 3395-3405 (2000).</li><li>Manabe, Y., Nafisi, M., Verhertbruggen, Y., 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=Loss-of-Function+Mutation+of+REDUCED+WALL+ACETYLATION2+in+Arabidopsis+Leads+to+Reduced+Cell+Wall+Acetylation+and+Increased+Resistance+to+Botrytis+cinerea.">Loss-of-Function Mutation of REDUCED WALL ACETYLATION2 in Arabidopsis Leads to Reduced Cell Wall Acetylation and Increased Resistance to Botrytis cinerea.</a> Plant Physiology. 155, 1068-1078 (2011).</li><li>Updegraff, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Semimicro+determination+of+cellulose+in+biological+materials.">Semimicro determination of cellulose in biological materials.</a> Anal. Biochem. 32, 420-424 (1969).</li><li>21Moller, I., Marcus, S. E., Haeger, 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=High-throughput+screening+of+monoclonal+antibodies+against+plant+cell+wall+glycans+by+hierarchial+clustering+of+their+carbohydrate+microarray+binding+profiles.">High-throughput screening of monoclonal antibodies against plant cell wall glycans by hierarchial clustering of their carbohydrate microarray binding profiles.</a> Glycoconjugate Journal. 25, 37-48 (2007).</li><li>S&#248;rensen, I., Pettolino, F. A., Wilson, S. 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=Mixed+linkage+(1&#8594;3),(1&#8594;4)-&#946;-D-glucan+is+not+unique+to+the+Poales+and+is+an+abundant+component+of+Equisetum+arvense+cell+walls.">Mixed linkage (1&#8594;3),(1&#8594;4)-&#946;-D-glucan is not unique to the Poales and is an abundant component of Equisetum arvense cell walls.</a> Plant J. 54 (13), 510-521 (2008).</li><li>Domozych, D. S., S&#248;rensen, I., Willats, W. G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+distribution+of+cell+wall+polymers+during+antheridium+development+and+spermatogenesis+in+the+Charophycean+green+alga,+Chara.">The distribution of cell wall polymers during antheridium development and spermatogenesis in the Charophycean green alga, Chara.</a> 2104, 1045-1056 (2009).</li><li>Singh, B., Avci, U., Eichler Inwood, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+specialized+outer+layer+of+the+primary+cell+wall+joins+elongating+cotton+fibers+into+tissue-like+bundles.">A specialized outer layer of the primary cell wall joins elongating cotton fibers into tissue-like bundles.</a> Plant Physiol. 150, 684-699 (2009).</li><li>&#216;bro, J., S&#248;rensen, I., Derkx, 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=High-throughput+screening+of+Erwinia+chrysanthemi+pectin+methylesterase+variants+using+carbohydrate+microarrays.">High-throughput screening of Erwinia chrysanthemi pectin methylesterase variants using carbohydrate microarrays.</a> Proteomics. 9, 1861-1868 (2009).</li></ol>

No conflicts of interest declared.

CoMPP is a fast and sensitive method for profiling the glycan composition of hundreds plant-derived samples in a matter of days. This method complements the already available bacterial or mammalian glycan array platforms for high-throughput screening of carbohydrate interactions with glycan-binding proteins such as lectins, receptors, and antibodies16. With a large diversity of probes available for detecting cell wall glycans, it is possible to gain detailed information about glycan epitopes belonging to all m...

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>3 mm Tungsten Carbide beads</td>
			<td>Qiagen</td>
			<td>69997</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Collection microtubes (1.2 mm)</td>
			<td>Qiagen</td>
			<td>19560</td>
			<td>1.5 ml microfuge tubes can also be used</td>
		</tr>
		<tr>
			<td>Qiagen TissueLyser II</td>
			<td>Qiagen</td>
			<td>85300</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>3 mm glass beads</td>
			<td>Sigma Aldrich</td>
			<td>Z143928</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>CDTA</td>
			<td>Sigma Aldrich</td>
			<td>34588</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cadmium oxide</td>
			<td>Sigma Aldrich</td>
			<td>202894</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>1,2-diaminoethane</td>
			<td>Sigma Aldrich</td>
			<td>03550</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Nitrocellulose membrane (0.22 &mu;m pore size)</td>
			<td>GE-water &amp; process technologies</td>
			<td>EP2HY00010</td>
			<td>different pore sized membranes are suitable for different pin types</td>
		</tr>
		<tr>
			<td>Xact II microarrayer robot</td>
			<td>Labnext</td>
			<td>001A</td>
			<td>the Xact II robot was fitted with a custom 20 x 20 cm ceramic plate to which the nitrocellulose membrane is attached</td>
		</tr>
		<tr>
			<td>Xtend RM microarray pins</td>
			<td>Labnext</td>
			<td>0037-350</td>
			<td>pins must be suitable for spotting on membranes</td>
		</tr>
		<tr>
			<td>384 well microtiter plates (polypropylene)</td>
			<td>Greiner</td>
			<td>781207</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Anti-glycan monoclonal antibodies</td>
			<td>Plant Probes/ 
			CarboSource/Biosupplies</td>
			<td>&nbsp;</td>
			<td>Websites; PlantProbes (<a href="http://www.plantprobes.net" target="_blank">www.plantprobes.net</a>), Carbosource (<a href="http://www.carbosource.net" target="_blank">www.carbosource.net</a>) and Biosupplies (<a href="http://www.biosupplies.com.au" target="_blank">www.biosupplies.com.au</a>).</td>
		</tr>
		<tr>
			<td>Anti-Rat IgG (whole molecule) - Peroxidase antibody produced in goat.</td>
			<td>Sigma</td>
			<td>A9037</td>
			<td>the type of secondary antibodies depends on the primary antibody used (e.g. raised in rat, mouse, goat etc).</td>
		</tr>
		<tr>
			<td>SIGMAFAST 3,3'-Diaminobenzidine tablets</td>
			<td>Sigma</td>
			<td>D4293</td>
			<td>the type of developing reagent depends on the secondary antibodies used and the detection method (colourmetric, or chemiluminecent).</td>
		</tr>
		<tr>
			<td>SuperSignal West Pico Chemiluminescent Substrate</td>
			<td>Thermoscientific</td>
			<td>34080</td>
			<td>see above</td>
		</tr>
		<tr>
			<td>Xplore Image Processing Software</td>
			<td>LabNext</td>
			<td>008</td>
			<td>many software types with automatic gridding tools are available to measure pixel value of microarray spots.</td>
		</tr>
		<tr>
			<td>Plant polysaccharides</td>
			<td>Sigma/Megazyme</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

glycan profiling of plant cell wall polymers using microarrays

Plant cell walls are complex matrixes of heterogeneous glycans which play an important role in the physiology and development of plants and provide the raw materials for human societies (e.g. wood, paper, textile and biofuel industries)1,2. However, understanding the biosynthesis and function of these components remains challenging.
Cell wall glycans are chemically and conformationally diverse due to the complexity of their building blocks, the glycosyl residues. These form linkages at multiple positions and differ in ring structure, isomeric or anomeric configuration, and in addition, are substituted with an array of non-sugar residues. Glycan composition varies in different cell and/or tissue types or even sub-domains of a single cell wall3. Furthermore, their composition is also modified during development1, or in response to environmental cues4.
In excess of 2,000 genes have Plant cell walls are complex matrixes of heterogeneous glycans been predicted to be involved in cell wall glycan biosynthesis and modification in Arabidopsis5. However, relatively few of the biosynthetic genes have been functionally characterized 4,5. Reverse genetics approaches are difficult because the genes are often differentially expressed, often at low levels, between cell types6. Also, mutant studies are often hindered by gene redundancy or compensatory mechanisms to ensure appropriate cell wall function is maintained7. Thus novel approaches are needed to rapidly characterise the diverse range of glycan structures and to facilitate functional genomics approaches to understanding cell wall biosynthesis and modification.
Monoclonal antibodies (mAbs)8,9 have emerged as an important tool for determining glycan structure and distribution in plants. These recognise distinct epitopes present within major classes of plant cell wall glycans, including pectins, xyloglucans, xylans, mannans, glucans and arabinogalactans. Recently their use has been extended to large-scale screening experiments to determine the relative abundance of glycans in a broad range of plant and tissue types simultaneously9,10,11.
Here we present a microarray-based glycan screening method called Comprehensive Microarray Polymer Profiling (CoMPP) (Figures 1 &amp; 2)10,11 that enables multiple samples (100 sec) to be screened using a miniaturised microarray platform with reduced reagent and sample volumes. The spot signals on the microarray can be formally quantified to give semi-quantitative data about glycan epitope occurrence. This approach is well suited to tracking glycan changes in complex biological systems12 and providing a global overview of cell wall composition particularly when prior knowledge of this is unavailable.

The relative abundance of glycans in six tissue types (anther filaments, pollen, ovaries, petals, sepals and stigma) from Nicotiana alata flowers was determined using CoMPP. Figure 3A shows a representative microarray that has been probed with mAb JIM5 specific for partially (low) methylesterified homogalacturonan (HG), an epitope which occurs on pectic polysaccharides14. The JIM5 epitope is detected in CDTA extracts of all flower tissues however is highest in pollen and lowest in stigmatic tissue (<s...

Watch this Scientific Journal Video about Glycan Profiling of Plant Cell Wall Polymers using Microarrays at JoVE.com

Glycan Profiling of Plant Cell Wall Polymers using Microarrays

A technique called Comprehensive Microarray Polymer Profiling (CoMPP) for the characterisation of plant cell wall glycans is described. This method combines the specificity of monoclonal antibodies directed to defined glycan-epitopes with a miniature microarray analytical platform allowing screening of glycan occurrence in a broad range of biological contexts.

Plant cell walls are complex matrixes of heterogeneous glycans which play an important role in the physiology and development of plants and provide the ...

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Research

JoVE Journal

Biology

14.5K Views.  University of Melbourne. A technique called Comprehensive Microarray Polymer Profiling (CoMPP) for the characterisation of plant cell wall glycans is described. This method combines the specificity of monoclonal antibodies directed to defined glycan-epitopes with a miniature microarray analytical platform allowing screening of glycan occurrence in a broad range of biological contexts.

Video: Glycan Profiling of Plant Cell Wall Polymers using Microarrays

Bacterial Gene Expression Analysis Using Microarrays

Measuring Plant Cell Wall Extension (Creep) Induced by Acidic pH and by Alpha-Expansin

Growing plant cell walls characteristically exhibit a property known as 'acid growth', by which we mean they are more extensible at low pH (&lt; 5) 1. The plant hormone auxin rapidly stimulates cell elongation in young stems and similar tissues at least in part by an acid-growth mechanism 2, 3. Auxin activates a H+ pump in the plasma membrane, causing acidification of the cell wall solution. Wall acidification activates expansins, which are endogenous cell wall-loosening proteins 4, causing the cell wall to yield to the wall tensions created by cell turgor pressure. As a result, the cell begins to enlarge rapidly. This 'acid growth' phenomenon is readily measured in isolated (nonliving) cell wall specimens. The ability of cell walls to undergo acid-induced extension is not simply the result of the structural arrangement of the cell wall polysaccharides (e.g. pectins), but depends on the activity of expansins 5. Expansins do not have any known enzymatic activity and the only way to assay for expansin activity is to measure their induction of cell wall extension. This video report details the sources and preparation techniques for obtaining suitable wall materials for expansin assays and goes on to show acid-induced extension and expansin-induced extension of wall samples prepared from growing cucumber hypocotyls.
 To obtain suitable cell wall samples, cucumber seedlings are grown in the dark, the hypocotyls are cut and frozen at -80 &deg;C. Frozen hypocotyls are abraded, flattened, and then clamped at constant tension in a special cuvette for extensometer measurements. To measure acid-induced extension, the walls are initially buffered at neutral pH, resulting in low activity of expansins that are components of the native cell walls. Upon buffer exchange to acidic pH, expansins are activated and the cell walls extend rapidly. We also demonstrate expansin activity in a reconstitution assay. For this part, we use a brief heat treatment to denature the native expansins in the cell wall samples. These inactivated cell walls do not extend even in acidic buffer, but addition of expansins to the cell walls rapidly restores their ability to extend.

Measuring Plant Cell Wall Extension Creep Induced by Acidic pH and by Alpha-Expansin

We demonstrate the use of a constant-force extensometer to measure long-term extension (creep) of plant cell wall specimens induced by acidic buffers and expansin protein.

Growing plant cell walls characteristically exhibit a property known as 'acid growth', by which we mean they are more extensible at low pH (&lt; 5) 1. The ...

Investigating Tissue- and Organ-specific Phytochrome Responses using FACS-assisted Cell-type Specific Expression Profiling in Arabidopsis thaliana

Light mediates an array of developmental and adaptive processes throughout the life cycle of a plant. Plants utilize light-absorbing molecules called photoreceptors to sense and adapt to light. The red/far-red light-absorbing phytochrome photoreceptors have been studied extensively. Phytochromes exist as a family of proteins with distinct and overlapping functions in all higher plant systems in which they have been studied1. Phytochrome-mediated light responses, which range from seed germination through flowering and senescence, are often localized to specific plant tissues or organs2. Despite the discovery and elucidation of individual and redundant phytochrome functions through mutational analyses, conclusive reports on distinct sites of photoperception and the molecular mechanisms of localized pools of phytochromes that mediate spatial-specific phytochrome responses are limited. We designed experiments based on the hypotheses that specific sites of phytochrome photoperception regulate tissue- and organ-specific aspects of photomorphogenesis, and that localized phytochrome pools engage distinct subsets of downstream target genes in cell-to-cell signaling. We developed a biochemical approach to selectively reduce functional phytochromes in an organ- or tissue-specific manner within transgenic plants. Our studies are based on a bipartite enhancer-trap approach that results in transactivation of the expression of a gene under control of the Upstream Activation Sequence (UAS) element by the transcriptional activator GAL43. The biliverdin reductase (BVR) gene under the control of the UAS is silently maintained in the absence of GAL4 transactivation in the UAS-BVR parent4. Genetic crosses between a UAS-BVR transgenic line and a GAL4-GFP enhancer trap line result in specific expression of the BVR gene in cells marked by GFP expression4. BVR accumulation in Arabidopsis plants results in phytochrome chromophore deficiency in planta5-7. Thus, transgenic plants that we have produced exhibit GAL4-dependent activation of the BVR gene, resulting in the biochemical inactivation of phytochrome, as well as GAL4-dependent GFP expression. Photobiological and molecular genetic analyses of BVR transgenic lines are yielding insight into tissue- and organ-specific phytochrome-mediated responses that have been associated with corresponding sites of photoperception4, 7, 8. Fluorescence Activated Cell Sorting (FACS) of GFP-positive, enhancer-trap-induced BVR-expressing plant protoplasts coupled with cell-type-specific gene expression profiling through microarray analysis is being used to identify putative downstream target genes involved in mediating spatial-specific phytochrome responses. This research is expanding our understanding of sites of light perception, the mechanisms through which various tissues or organs cooperate in light-regulated plant growth and development, and advancing the molecular dissection of complex phytochrome-mediated cell-to-cell signaling cascades.

Investigating Tissue- and Organ-specific Phytochrome Responses using FACS-assisted Cell-type Specific Expression Profiling in Arabidopsis thaliana

The molecular basis of spatial-specific phytochrome responses is being investigated using transgenic plants that exhibit tissue- and organ-specific phytochrome deficiencies. The isolation of specific cells exhibiting induced phytochrome chromophore depletion by Fluorescence-Activated Cell Sorting followed by microarray analyses is being utilized to identify genes involved in spatial-specific phytochrome responses.

Light mediates an array of developmental and adaptive processes throughout the life cycle of a plant. Plants utilize light-absorbing molecules called ...

Genome-wide Analysis of Aminoacylation (Charging) Levels of tRNA Using Microarrays

tRNA aminoacylation, or charging, levels can rapidly change within a cell in response to the environment[1]. Changes in tRNA charging levels in both prokaryotic and eukaryotic cells lead to translational regulation which is a major cellular mechanism of stress response. Familiar examples are the stringent response in E. coli and the Gcn2 stress response pathway in yeast ([2-6]). Recent work in E. coli and S. cerevisiae have shown that tRNA charging patterns are highly dynamic and depends on the type of stress experienced by cells [1, 6, 7]. The highly dynamic, variable nature of tRNA charging makes it essential to determine changes in tRNA charging levels at the genomic scale, in order to fully elucidate cellular response to environmental variations. In this review we present a method for simultaneously measuring the relative charging levels of all tRNAs in S. cerevisiae . While the protocol presented here is for yeast, this protocol has been successfully applied for determining relative charging levels in a wide variety of organisms including E. coli and human cell cultures[7, 8].

Genome-wide Analysis of Aminoacylation Charging Levels of tRNA Using Microarrays

We describe a method for microarray analysis to determine relative aminoacylation levels of all tRNAs from S. cerivisiae.

tRNA aminoacylation, or charging, levels can rapidly change within a cell in response to the environment[1]. Changes in tRNA charging levels in both ...

OLIgo Mass Profiling (OLIMP) of Extracellular Polysaccharides

The direct contact of cells to the environment is mediated in many organisms by an extracellular matrix. One common aspect of extracellular matrices is that they contain complex sugar moieties in form of glycoproteins, proteoglycans, and/or polysaccharides. Examples include the extracellular matrix of humans and animal cells consisting mainly of fibrillar proteins and proteoglycans or the polysaccharide based cell walls of plants and fungi, and the proteoglycan/glycolipid based cell walls of bacteria. All these glycostructures play vital roles in cell-to-cell and cell-to-environment communication and signalling.
An extraordinary complex example of an extracellular matrix is present in the walls of higher plant cells. Their wall is made almost entirely of sugars, up to 75% dry weight, and consists of the most abundant biopolymers present on this planet. Therefore, research is conducted how to utilize these materials best as a carbon-neutral renewable resource to replace petrochemicals derived from fossil fuel. The main challenge for fuel conversion remains the recalcitrance of walls to enzymatic or chemical degradation due to the unique glycostructures present in this unique biocomposite.
Here, we present a method for the rapid and sensitive analysis of plant cell wall glycostructures. This method OLIgo Mass Profiling (OLIMP) is based the enzymatic release of oligosaccharides from wall materials facilitating specific glycosylhydrolases and subsequent analysis of the solubilized oligosaccharide mixtures using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS)1 (Figure 1). OLIMP requires walls of only 5000 cells for a complete analysis, can be performed on the tissue itself2, and is amenable to high-throughput analyses3. While the absolute amount of the solubilized oligosaccharides cannot be determined by OLIMP the relative abundance of the various oligosaccharide ions can be delineated from the mass spectra giving insights about the substitution-pattern of the native polysaccharide present in the wall.
OLIMP can be used to analyze a wide variety of wall polymers, limited only by the availability of specific enzymes4. For example, for the analysis of polymers present in the plant cell wall enzymes are available to analyse the hemicelluloses xyloglucan using a xyloglucanase5, 11, 12, 13, xylan using an endo-&beta;-(1-4)-xylanase 6,7, or for pectic polysaccharides using a combination of a polygalacturonase and a methylesterase 8. Furthermore, using the same principles of OLIMP glycosylhydrolase and even glycosyltransferase activities can be monitored and determined 9.

OLIgo Mass Profiling OLIMP of Extracellular Polysaccharides

A rapid way is described to gain insights into the structure of polysaccharides in an extracellular matrix. The method takes advantage of the specificity of glycosylhydrolases and the sensitivity of mass spectrometry allowing minute amounts of materials to be analyzed. This technique is adaptable to be used directly on tissue itself.

The direct contact of cells to the environment is mediated in many organisms by an extracellular matrix. One common aspect of extracellular matrices is ...

Profiling Thiol Redox Proteome Using Isotope Tagging Mass Spectrometry

Pseudomonas syringae pv. tomato strain DC3000 not only causes bacterial speck disease in Solanum lycopersicum but also on Brassica species, as well as on Arabidopsis thaliana, a genetically tractable host plant1,2. The accumulation of reactive oxygen species (ROS) in cotyledons inoculated with DC3000 indicates a role of ROS in modulating necrotic cell death during bacterial speck disease of tomato3. Hydrogen peroxide, a component of ROS, is produced after inoculation of tomato plants with Pseudomonas3. Hydrogen peroxide can be detected using a histochemical stain 3'-3' diaminobenzidine (DAB)4. DAB staining reacts with hydrogen peroxide to produce a brown stain on the leaf tissue4. ROS has a regulatory role of the cellular redox environment, which can change the redox status of certain proteins5. Cysteine is an important amino acid sensitive to redox changes. Under mild oxidation, reversible oxidation of cysteine sulfhydryl groups serves as redox sensors and signal transducers that regulate a variety of physiological processes6,7. Tandem mass tag (TMT) reagents enable concurrent identification and multiplexed quantitation of proteins in different samples using tandem mass spectrometry8,9. The cysteine-reactive TMT (cysTMT) reagents enable selective labeling and relative quantitation of cysteine-containing peptides from up to six biological samples. Each isobaric cysTMT tag has the same nominal parent mass and is composed of a sulfhydryl-reactive group, a MS-neutral spacer arm and an MS/MS reporter10. After labeling, the samples were subject to protease digestion. The cysteine-labeled peptides were enriched using a resin containing anti-TMT antibody. During MS/MS analysis, a series of reporter ions (i.e., 126-131 Da) emerge in the low mass region, providing information on relative quantitation. The workflow is effective for reducing sample complexity, improving dynamic range and studying cysteine modifications. Here we present redox proteomic analysis of the Pst DC3000 treated tomato (Rio Grande) leaves using cysTMT technology. This high-throughput method has the potential to be applied to studying other redox-regulated physiological processes.

Reactive oxygen species level is elevated when cells encounter stress conditions. Here we show the example of 3'-3' diaminobenzidine staining as well as cysTMT labeling and mass spectrometry to profile the redox proteome in Pseudomonas syringae treated tomato leaves.

Pseudomonas syringae pv. tomato strain DC3000 not only causes bacterial speck disease in Solanum lycopersicum but also on Brassica species, as well as on ...

Histochemical Staining of Arabidopsis thaliana Secondary Cell Wall Elements

Arabidopsis thaliana is a model organism commonly used to understand and manipulate various cellular processes in plants, and it has been used extensively in the study of secondary cell wall formation. Secondary cell wall deposition occurs after the primary cell wall is laid down, a process carried out exclusively by specialized cells such as those forming vessel and fiber tissues. Most secondary cell walls are composed of cellulose (40&#8211;50%), hemicellulose (25&#8211;30%), and lignin (20&#8211;30%). Several mutations affecting secondary cell wall biosynthesis have been isolated, and the corresponding mutants may or may not exhibit obvious biochemical composition changes or visual phenotypes since these mutations could be masked by compensatory responses. Staining procedures have historically been used to show differences on a cellular basis. These methods are exclusively visual means of analysis; nevertheless their role in rapid and critical analysis is of great importance. Congo red and calcofluor white are stains used to detect polysaccharides, whereas M&#228;ule and phloroglucinol are commonly used to determine differences in lignin, and toluidine blue O is used to differentially stain polysaccharides and lignin. The seemingly simple techniques of sectioning, staining, and imaging can be a challenge for beginners. Starting with sample preparation using the A. thaliana model, this study details the protocols of a variety of staining methodologies that can be easily implemented for observation of cell and tissue organization in secondary cell walls of plants.

Histochemical Staining of Arabidopsis thaliana Secondary Cell Wall Elements

Plant cell wall composition varies between tissue types and can include lignin, cellulose, hemicelluloses, and pectin. Various staining techniques have been developed to visualize differences at the cell-type level. This paper is a compilation of commonly used cell wall staining techniques.

Arabidopsis thaliana is a model organism commonly used to understand and manipulate various cellular processes in plants, and it has been used extensively ...

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix containing polysaccharides that include cellulose microfibrils that form both crystalline structures and cellulose chains of amorphous organization. The orientation of the cellulose fibers and their concentrations dictate the mechanical properties of the cell. Several methods are used to determine the levels of crystalline cellulose, each bringing both advantages and limitations. Some can distinguish the proportion of crystalline regions within the total cellulose. However, they are limited to whole-organ analyses that are deficient in spatiotemporal information. Others relying on live imaging, are limited by the use of imprecise dyes. Here, we report a sensitive polarized light-based system for specific quantification of relative light retardance, representing crystalline cellulose accumulation in cross sections of Arabidopsis thaliana roots. In this method, the cellular resolution and anatomical data are maintained, enabling direct comparisons between the different tissues composing the growing root. This approach opens a new analytical dimension, shedding light on the link between cell wall composition, cellular behavior and whole-organ growth.

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

Crystalline cellulose is an important constituent of the plant cell wall. However, its quantification at a cellular resolution is technically challenging. Here, we report the use of polarized light technology and root cross sections to obtain information of cell wall composition at a spatiotemporal resolution.

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix ...

Laser-assisted Microdissection (LAM) as a Tool for Transcriptional Profiling of Individual Cell Types

The understanding of developmental processes at the molecular level requires insights into transcriptional regulation, and thus the transcriptome, at the level of individual cell types. While the methods described here are generally applicable to a wide range of species and cell types, our research focuses on plant reproduction. Plant cultivation and seed production is of crucial importance for human and animal nutrition. A detailed understanding of the regulatory networks that govern the formation of the reproductive lineage (germline) and ultimately of seeds is a precondition for the targeted manipulation of plant reproduction. In particular, the engineering of apomixis (asexual reproduction through seeds) into crop plants promises great improvements, as it leads to the formation of clonal seeds that are genetically identical to the mother plant. Consequently, the cell types of the female germline are of major importance for the understanding and engineering of apomixis. However, as the corresponding cells are deeply embedded within the floral tissues, they are very difficult to access for experimental analyses, including cell-type specific transcriptomics. To overcome this limitation, sections of individual cells can be isolated by laser-assisted microdissection (LAM). While LAM in combination with transcriptional profiling allows the identification of genes and pathways active in any cell type with high specificity, establishing a suitable protocol can be challenging. Specifically, the quality of RNA obtained after LAM can be compromised, especially when small, single cells are targeted. To circumvent this problem, we have established a workflow for LAM that reproducibly results in high RNA quality that is well suitable for transcriptomics, as exemplified here by the isolation of cells of the female germline in apomictic Boechera. In this protocol, procedures are described for tissue preparation and LAM, also with regard to RNA extraction and quality control.

Laser-assisted Microdissection LAM as a Tool for Transcriptional Profiling of Individual Cell Types

Here we present a protocol for laser-assisted microdissection of specific plant cell types for transcriptional profiling. While the protocol is suitable for different species and cell types, the focus is on highly inaccessible cells of the female germline important for sexual and apomictic reproduction in the crucifer genus Boechera.

The understanding of developmental processes at the molecular level requires insights into transcriptional regulation, and thus the transcriptome, at the ...

An Easy Method for Plant Polysome Profiling

Translation of mRNA to protein is a fundamental and highly regulated biological process. Polysome profiling is considered as a gold standard for the analysis of translational regulation. The method described here is an easy and economical way for fractionating polysomes from various plant tissues. A sucrose gradient is made without the need for a gradient maker by sequentially freezing each layer. Cytosolic extracts are then prepared in a buffer containing cycloheximide and chloramphenicol to immobilize the cytosolic and chloroplastic ribosomes to mRNA and are loaded onto the sucrose gradient. After centrifugation, six fractions are directly collected from the bottom to the top of the gradient, without piercing the ultracentrifugation tube. During collection, the absorbance at 260 nm is read continuously to generate a polysome profile that gives a snapshot of global translational activity. Fractions are then pooled to prepare three different mRNA populations: the polysomes, mRNAs bound to several ribosomes; the monosomes, mRNAs bound to one ribosome; and mRNAs that are not bound to ribosomes. mRNAs are then extracted. This protocol has been validated for different plants and tissues including Arabidopsis thaliana seedlings and adult plants, Nicotiana benthamiana, Solanum lycopersicum, and Oryza sativa leaves.

This protocol describes an easy method to extract and fractionate transcripts from plant tissues on the basis of the number of bound ribosomes. It allows a global estimate of translation activity and the determination of the translational status of specific mRNAs.

Translation of mRNA to protein is a fundamental and highly regulated biological process. Polysome profiling is considered as a gold standard for the ...