Research in the laboratory of M.T. is supported by grants from the National Science Foundation (DBI-0820610 and IOS-1022102) and the NY Department of Health (NYSTEM-C024308). C.M. received postdoctoral fellowships from the Spanish Ministry of Education and Science (2007-0937) and the Foundation Rafael del Pino, Spain.

<ol>
	<li>Rensink, W. A., Buell, 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=Microarray+expression+profiling+resources+for+plant+genomics.">Microarray expression profiling resources for plant genomics.</a> Trends. Plant. Sci. 10, 603-609 (2005).</li><li>Li, P., Ponnala, L., Gandotra, N., Wang, L., Si, Y., Tausta, S. L., Kebrom, T. H., Provart, N., Patel, R., Myers, 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=The+developmental+dynamics+of+the+maize+leaf+transcriptome.">The developmental dynamics of the maize leaf transcriptome.</a> Nat. Genet. 42, 1060-1067 (2010).</li><li>Lister, R., O'Malley, R. C., Tonti-Filippini, J., Gregory, B. D., Berry, C. C., Millar, A. H., Ecker, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+integrated+single-base+resolution+maps+of+the+epigenome+in+Arabidopsis.">Highly integrated single-base resolution maps of the epigenome in Arabidopsis.</a> Cell. 133, 523-536 (2008).</li><li>Brady, S. M., Orlando, D. A., Lee, J. Y., Wang, J. Y., Koch, J., Dinneny, J. R., Mace, D., Ohler, U., Benfey, P. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-resolution+root+spatiotemporal+map+reveals+dominant+expression+patterns.">A high-resolution root spatiotemporal map reveals dominant expression patterns.</a> Science. 318, 801-806 (2007).</li><li>Brooks, L., Strable, J., Zhang, X., Ohtsu, K., Zhou, R., Sarkar, A., Hargreaves, S., Elshire, R. J., Eudy, D., Pawlowska, T., Ware, D., Janick-Buckner, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microdissection+of+shoot+meristem+functional+domains.">Microdissection of shoot meristem functional domains.</a> PLoS. Genet. 5, e1000476-e1000476 (2009).</li><li>Galbraith, D. W., Birnbaum, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+studies+of+cell+type-specific+gene+expression+in+plants.">Global studies of cell type-specific gene expression in plants.</a> Annu. Rev. Plant. Biol. 57, 451-475 (2006).</li><li>Ohtsu, K., Smith, M., Emrich, S., Borsuk, L., Zhou, R., Chen, T., Zhang, X., Timmermans, M., Beck, J., Buckner, B., Janick-Buckner, D., Nettleton, D., Scanlon, M., Schnable, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+gene+expression+analysis+of+the+shoot+apical+meristem+of+maize+(Zea+mays+L.).">Global gene expression analysis of the shoot apical meristem of maize (Zea mays L.).</a> Plant. J. 52, 391-404 (2007).</li><li>Juarez, M. T., Kui, J. S., Thomas, J., Heller, B. A., Timmermans, M. C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=microRNA-mediated+repression+of+rolled+leaf1+specifies+maize+leaf+polarity.">microRNA-mediated repression of rolled leaf1 specifies maize leaf polarity.</a> Nature. 428, 84-88 (2004).</li><li>Kramer, E. M., Irish, V. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+genetic+mechanisms+controlling+petal+development.">Evolution of genetic mechanisms controlling petal development.</a> Nature. 399, 144-148 (1999).</li><li>Stuurman, J., Jäggi, F., Kuhlemeier, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shoot+meristem+maintenance+is+controlled+by+a+GRAS-gene+mediated+signal+from+differentiating+cells.">Shoot meristem maintenance is controlled by a GRAS-gene mediated signal from differentiating cells.</a> Genes Dev. 16, 2213-2218 (2002).</li><li>Kim, M., McCormick, S., Timmermans, M., Sinha, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+expression+domain+of+PHANTASTICA+determines+leaflet+placement+in+compound+leaves.">The expression domain of PHANTASTICA determines leaflet placement in compound leaves.</a> Nature. 424, 438-443 (2003).</li><li>Kramer, E. M., Holappa, L., Gould, B., Jaramillo, M. A., Setnikov, D., Santiago, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elaboration+of+B+gene+function+to+include+the+identity+of+novel+floral+organs+in+the+lower+eudicot+Aquilegia.">Elaboration of B gene function to include the identity of novel floral organs in the lower eudicot Aquilegia.</a> Plant Cell. 19, 750-766 (2007).</li><li>Lippman, Z. B., Cohen, O., Alvarez, J. P., Abu-Abied, M., Pekker, I., Paran, I., Eshed, Y., Zamir, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+making+of+a+compound+inflorescence+in+tomato+and+related+nightshades.">The making of a compound inflorescence in tomato and related nightshades.</a> PLoS Biol. 6, e288-e288 (2008).</li><li>Kidner, C., Timmermans, M. C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+hybridization+as+a+tool+to+study+the+role+of+microRNAs+in+plant+development.">In situ hybridization as a tool to study the role of microRNAs in plant development.</a> Methods. Mol. Biol. 342, 159-179 (2006).</li><li>Jackson, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double+labeling+of+KNOTTED1+mRNA+and+protein+reveals+multiple+potential+sites+of+protein+trafficking+in+the+shoot.">Double labeling of KNOTTED1 mRNA and protein reveals multiple potential sites of protein trafficking in the shoot.</a> 129, 1423-1429 (2002).</li><li>Jensen, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Botanical Histochemistry. , 408-408 (1962).</li><li>Jackson, D., Bowles, D. J., Gurr, S. J., McPherson, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+hybridization+in+plants.">In situ hybridization in plants.</a> Molecular Plant Pathology: A Practical Approach. , 163-174 (1991).</li><li>Chitwood, D. H., Nogueira, F. T., Howell, M. o. n. t. g. o. m. e. r. y., Carrington, T. A., C, J., Timmermans, M. C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pattern+formation+via+small+RNA+mobility.">Pattern formation via small RNA mobility.</a> Genes. Dev. 23, 549-554 (2009).</li><li>Piette, D., Hendrickx, M., Willems, E., Kemp, C. R., Leyns, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+optimized+procedure+for+whole-mount+in+situ+hybridization+on+mouse+embryos+and+embryoid+bodies.">An optimized procedure for whole-mount in situ hybridization on mouse embryos and embryoid bodies.</a> Nat. Protoc. 3, 1194-1201 (2008).</li><li>Blilou, I., Xu, J., Wildwater, M., Willemsen, V., Paponov, I., Friml, J., Heidstra, R., Aida, M., Palme, K., Scheres, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+PIN+auxin+efflux+facilitator+network+controls+growth+and+patterning+in+Arabidopsis+roots.">The PIN auxin efflux facilitator network controls growth and patterning in Arabidopsis roots.</a> Nature. 433, 39-44 (2005).</li><li>Jackson, D., Hake, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+phyllotaxy+in+maize+by+the+abphyl1+gene.">Control of phyllotaxy in maize by the abphyl1 gene.</a> Development. , 126-315 (1999).</li><li>Chuck, G., Whipple, C., Jackson, D., Hake, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+maize+SBP-box+transcription+factor+encoded+by+tasselsheath4+regulates+bract+development+and+the+establishment+of+meristem+boundaries.">The maize SBP-box transcription factor encoded by tasselsheath4 regulates bract development and the establishment of meristem boundaries.</a> Development. 137, 1243-1250 (2010).</li><li>Long, J. A., Barton, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+development+of+apical+embryonic+pattern+in+Arabidopsis.">The development of apical embryonic pattern in Arabidopsis.</a> Development. 125, 3027-3035 (1998).</li><li>Nogueira, F. T., Chitwood, D. H., Madi, S., Ohtsu, K., Schnable, P. S., Scanlon, M. J., Timmermans, M. C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+small+RNA+accumulation+in+the+maize+shoot+apex.">Regulation of small RNA accumulation in the maize shoot apex.</a> PLoS Genet. 5, e1000320-e1000320 (2009).</li></ol>

No conflicts of interest declared.

The in situ hybridization method outlined here allows the direct visualization of the spatiotemporal expression pattern of any gene of interest with great cellular resolution, high sensitivity and specificity. The protocol does not allow a quantitative comparison of expression levels between genes. However, the method's high sensitivity and resolution can reveal gradients of gene expression within a tissue8, 18, which is not possible with most other methods of analyzing gene expression. 
The protocol includes many steps, which can make trouble-shooting problematic. The most critical steps of the protocol are the fixation of the tissue and the selection and labeling of the probe. Poorly infiltrated tissues and probes with low DIG incorporation will yield very weak signals that might be difficult to detect above background. For each new gene of interest, it is advisable to try a few distinct probes derived from different regions of the transcript. Occasionally, two or three probes targeting different smaller regions of the gene may need to be combined to obtain a strong and specific hybridization signal. In addition, the hybridization conditions, such as the temperature and composition of the hybridization buffer, can be optimized for each gene or tissue to lower or increase the hybridization stringency. Also the protease treatment step is a variable and can be changed to adapt the protocol for different plant species or for the detection of transcripts with very low abundance. The inclusion of both positive and negative control probes will be helpful in identifying problematic points of the protocol. 
The procedure is optimized for paraffin-embedded plant tissue sections but with minor modifications can be used also for whole-mount in situ hybridization. Although widely used in animal research19, whole mount in situ hybridization will be limited to plant tissues that can be easily infiltrated, such as embryos, roots or young meristematic tissues20,21. The protocol can also be easily modified to simultaneously detect two distinct mRNAs or localize transcripts alongside proteins15,22,23. Finally, it is possible to extend the application of this method to the visualization of small RNA expression patterns in plants. miRNA expression patterns have been determined using this protocol in both maize and Arabidopsis8,14. More recently, the in vitro transcribed probes have been replaced by commercially available DIG-labeled locked nucleic acid (LNA) oligo probes that increase signal sensitivity18, 24.

<table border="1">
<tbody>
<tr>
<th>Product</th>
<th>Company</th>
<th>Catalogue number</th>
<th>Remarks</th>
</tr>
<tr>
<td>Cytoseal 60 4oz</td>
<td>Fisher</td>
<td>23-244-256</td>
<td>Toluene-based 8310-4</td>
</tr>
<tr>
<td>Histoclear		</td>
<td>Fisher</td>
<td>50-899-90147</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Tissue Path Paraplast Plus	 	</td>
<td>Fisher</td>
<td>23-021-400</td>
<td>&nbsp;</td>
</tr>
<tr>
<td> N+ nylon membrane Hybond-N+		 </td>
<td>GE Healthcare</td>
<td>RPN203B	</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>RNase OUT; 40 U/&mu;L			 	</td>
<td>Invitrogen</td>
<td>10777019</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>RQ1 RNase-Free DNase; 1 U/&mu;l 			 	</td>
<td>Promega</td>
<td>M6101</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>DIG-labeled Control RNA 			</td>
<td>Roche</td>
<td>11585746910 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>DIG RNA labeling mix</td>
<td>Roche</td>
<td>11277073910</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>SP6 RNA polymerase 1,000 U		 	</td>
<td>Roche</td>
<td>10810274001	</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>T3 RNA polymerase 1,000 U		 	</td>
<td>Roche</td>
<td>11031163001	</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>T7 RNA polymerase 1,000 U		 	</td>
<td>Roche</td>
<td>10881767001	</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>RNase-A 				 	</td>
<td>Roche</td>
<td>109142</td>
<td>dissolve in glycerol 50% Tris 100mM pH8.0</td>
</tr>
<tr>
<td>Blocking Reagent 			</td>
<td>Roche</td>
<td>1 096 176</td>
<td>Heat up to 70&deg;C in TBS buffer</td>
</tr>
<tr>
<td>Anti-Digoxygenin-AP, Fab fragments from sheep 150 U		 	</td>
<td>Roche</td>
<td>1 093 274</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>NBT/BCIP stock solution			 	</td>
<td>Roche</td>
<td>1 681 451</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>mini Quick Spin RNA Columns 	 	</td>
<td>Roche</td>
<td>11814427001	</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>tRNA from E. coli 	 		 	</td>
<td>Roche</td>
<td>109541</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Triton&reg;X-100 			 	</td>
<td>Sigma</td>
<td>T8787</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Tween-20 	</td>
<td>Sigma</td>
<td>P9416</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Deionized formamide			 	</td>
<td>Sigma</td>
<td>F9037</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Protease from Streptomyces griseus Type XIV	 	</td>
<td>Sigma</td>
<td>P5147</td>
<td>Dilute in milliQ water and pre-digest 4 hours at 37&deg;C </td>
</tr>
<tr>
<td>Triethanolamine 	 	</td>
<td>Sigma</td>
<td>90279</td>
<td>Dilute in water, bring to pH8.0 with HCl</td>
</tr>
<tr>
<td>Acetic anhydride 	 	</td>
<td>Sigma		 </td>
<td>A6404</td>
<td>&nbsp;</td>
</tr>
<tr>
<td> Dextran sulfate sodium salt from Leuconostoc spp.			 	</td>
<td>Sigma</td>
<td>D8906-5G</td>
<td>Dextran Sulfate should be heated to 80&deg;C to dissolve.</td>
</tr>
<tr>
<td>Denhardt&#x2019;s Solution 50x Concentrate			 	</td>
<td>Sigma</td>
<td>D2532</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Albumin from bovine serum - &ge;98%			 	</td>
<td>Sigma</td>
<td>A7906</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Eosin Y disodium salt				</td>
<td>Sigma</td>
<td>E4382</td>
<td>Dissolve in 96-100% ethanol until saturated	 </td>
</tr>
<tr>
<td>Paraformaldehyde 	 	</td>
<td>	Sigma</td>
<td>	P6148</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Ethanol absolute 200 proof	 	</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Phenol/chloroform	 	</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Base moulds			 	</td>
<td>Electronic Microsocpy Science</td>
<td>62352-15</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Embedding rings			 	</td>
<td>Fisher</td>
<td>22-038-197</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>20ml disposable scintillation vials, with caps			 	</td>
<td>VWR</td>
<td>66020-326</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Probe-on-plus slides			 	</td>
<td>Fisher</td>
<td>22-230-900</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Micro cover glasses 24x50 mm		 	</td>
<td>VWR</td>
<td>48404-452</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Whatman paper 3mm		 	</td>
<td>VWR</td>
<td>89022-360</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Three glass dishes and one stainless steel slide rack	 	</td>
<td>Electronic Microsocpy Science</td>
<td>71420-25</td>
<td>Two glass dished are necessary for histoclear treatment and the last one is used for the acetic anhydride treatment</td>
</tr>
<tr>
<td>18 clean plastic containers			 	</td>
<td>Electronic Microsocpy Science</td>
<td>71402</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>2 or 3 large flat plastic boxes with sealable lids		 	</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>required for the hybridization and antibody steps</td>
</tr>

<tr>
<td>Fine brushes 	 	 			 	</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Help handing wax ribbons</td>
</tr>

<tr>
<td>Microtome			 	</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Leica</td>
</tr>

<tr>
<td>Self-cleaning dry vacuum system				 	</td>
<td>Welch</td>
<td>2025</td>
<td>&nbsp;</td>
</tr>

<tr>
<td>Slide warmer		 		 	</td>
<td>Fisher</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>

<tr>
<td>Heating block 	 	 			 	</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>needed at 60&deg;C and 85&deg;C</td>
</tr>

<tr>
<td>Incubator at 58-60&deg;C		 			 	</td>
<td>Fisher</td>
<td>&nbsp;</td>
<td>For steps with molten Paraplast</td>

</tr>

<tr>
<td>Ovens or water baths for 55&deg;C and 37&deg;C 		 			 	</td>
<td>Fisher</td>
<td>&nbsp;</td>
<td>Need two due to the quick change between temperatures</td>
</tr>
<tr>
<td>Centrifuge (4&deg;C - 20&deg;C)</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Fume hood</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>


</tbody>
</table>

in situ hybridization for the precise localization of transcripts in plants

With the advances in genomics research of the past decade, plant biology has seen numerous studies presenting large-scale quantitative analyses of gene expression. Microarray and next generation sequencing approaches are being used to investigate developmental, physiological and stress response processes, dissect epigenetic and small RNA pathways, and build large gene regulatory networks1-3. While these techniques facilitate the simultaneous analysis of large gene sets, they typically provide a very limited spatiotemporal resolution of gene expression changes. This limitation can be partially overcome by using either profiling method in conjunction with lasermicrodissection or fluorescence-activated cell sorting4-7. However, to fully understand the biological role of a gene, knowledge of its spatiotemporal pattern of expression at a cellular resolution is essential. Particularly, when studying development or the effects of environmental stimuli and mutants can the detailed analysis of a gene's expression pattern become essential. For instance, subtle quantitative differences in the expression levels of key regulatory genes can lead to dramatic phenotypes when associated with the loss or gain of expression in specific cell types. 
Several methods are routinely used for the detailed examination of gene expression patterns. One is through analysis of transgenic reporter lines. Such analysis can, however, become time-consuming when analyzing multiple genes or working in plants recalcitrant to transformation. Moreover, an independent validation to ensure that the transgene expression pattern mimics that of the endogenous gene is typically required. Immunohistochemical protein localization or mRNA in situ hybridization present relatively fast alternatives for the direct visualization of gene expression within cells and tissues. The latter has the distinct advantage that it can be readily used on any gene of interest. In situ hybridization allows detection of target mRNAs in cells by hybridization with a labeled anti-sense RNA probe obtained by in vitro transcription of the gene of interest. 
Here we outline a protocol for the in situ localization of gene expression in plants that is highly sensitivity and specific. It is optimized for use with paraformaldehyde fixed, paraffin-embedded sections, which give excellent preservation of histology, and DIG-labeled probes that are visualized by immuno-detection and alkaline-phosphatase colorimetric reaction. This protocol has been successfully applied to a number of tissues from a wide range of plant species, and can be used to analyze expression of mRNAs as well as small RNAs8-14.

Watch this Scientific Journal Video about In Situ Hybridization for the Precise Localization of Transcripts in Plants at JoVE.com

In Situ Hybridization for the Precise Localization of Transcripts in Plants

The in situ hybridization protocol described here allows a direct localization of mRNA and small RNA expression at the cellular level with high sensitivity and specificity. The procedure is optimized for paraffin-embedded plant tissue sections, is applicable to a wide range of plants and tissues, and can be completed within ten days.

In Situ Hybridization for the Precise Localization of Transcripts in Plants

With the advances in genomics research of the past decade, plant biology has seen numerous studies presenting large-scale quantitative analyses of gene ...

in-situ-hybridization-for-precise-localization-transcripts

Research

JoVE Journal

Biology

51.2K Views.  Cold Spring Harbor Laboratory. The in situ hybridization protocol described here allows a direct localization of mRNA and small RNA expression at the cellular level with high sensitivity and specificity. The procedure is optimized for paraffin-embedded plant tissue sections, is applicable to a wide range of plants and tissues, and can be completed within ten days.

Video: In Situ Hybridization for the Precise Localization of Transcripts in Plants

Double Whole Mount in situ Hybridization of Early Chick Embryos

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  gene expression in brain, neural tube, somite and heart primordia formation. This video demonstrates the different steps in 2-color whole mount in situ hybridization; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, the embryo is processed for prehybridization. The embryo is then hybridized with two different probes, one coupled to DIG, and one coupled to FITC.  Following overnight hybridization, the embryo is incubated with DIG coupled antibody. Color reaction for DIG substrate is performed, and the region of interest appears blue. The embryo is then incubated with FITC coupled antibody. The embryo is processed for color reaction with FITC, and the region of interest appears red. Finally, the embryo is fixed and processed for phtograph and sectioning. A troubleshooting guide is also presented.

This video demonstrates 2-color whole mount in situ hybridization, a method by which the spatial and temporal expression pattern of 2 different genes can be visualized in young chick embryos. This method was originally introduced by David Wilkinson, Domingos Henrique, Phil Ingham and David Ish -Horowicz.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Fluorescence in situ hybridization (FISH) Protocol in Human Sperm

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic process in the parents. In human males, these errors can lead to the production of spermatozoa with numerical chromosome abnormalities which represent an increased risk of transmitting these anomalies to the offspring.
For this reason, the technique of fluorescence in situ hybridization (FISH) on sperm nuclei has become a protocol widely incorporated in the context of clinical diagnosis. This practice provides an estimate of the frequencies of numerical chromosome abnormalities in the gametes of the patients that seek for genetic reproductive advice.
To date, the chromosomes most frequently included in sperm FISH analysis are chromosomes X, Y, 13, 18 and 21.
This video-article describes, step by step, how to process and fix a human semen sample, how to decondense and denature the sperm chromatin, how to proceed to obtain sperm FISH preparations, and how to visualize the results at the microscope. Special remarks of the most relevant steps are given to achieve the best results.

Fluorescence in situ hybridization FISH Protocol in Human Sperm

This video-article describes, step by step, how to process a semen sample to achieve good-quality fluorescence in situ hybridization on human spermatozoa. Preparations obtained can be used for aneuploidy screening in the context of clinical diagnosis.

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic ...

Radioactive in situ Hybridization for Detecting Diverse Gene Expression Patterns in Tissue

Knowing the timing, level, cellular localization, and cell type that a gene is expressed in contributes to our understanding of the function of the gene. Each of these features can be accomplished with in situ hybridization to mRNAs within cells. Here we present a radioactive in situ hybridization method modified from Clayton et al. (1988)1 that has been working successfully in our lab for many years, especially for adult vertebrate brains2-5. The long complementary RNA (cRNA) probes to the target sequence allows for detection of low abundance transcripts6,7. Incorporation of radioactive nucleotides into the cRNA probes allows for further detection sensitivity of low abundance transcripts and quantitative analyses, either by light sensitive x-ray film or emulsion coated over the tissue. These detection methods provide a long-term record of target gene expression. Compared with non-radioactive probe methods, such as DIG-labeling, the radioactive probe hybridization method does not require multiple amplification steps using HRP-antibodies and/or TSA kit to detect low abundance transcripts. Therefore, this method provides a linear relation between signal intensity and targeted mRNA amounts for quantitative analysis. It allows processing 100-200 slides simultaneously. It works well for different developmental stages of embryos. Most developmental studies of gene expression use whole embryos and non-radioactive approaches8,9, in part because embryonic tissue is more fragile than adult tissue, with less cohesion between cells, making it difficult to see boundaries between cell populations with tissue sections. In contrast, our radioactive approach, due to the larger range of sensitivity, is able to obtain higher contrast in resolution of gene expression between tissue regions, making it easier to see boundaries between populations. Using this method, researchers could reveal the possible significance of a newly identified gene, and further predict the function of the gene of interest.

Radioactive in situ Hybridization for Detecting Diverse Gene Expression Patterns in Tissue

This protocol is successfully used to quantitatively detect levels and spatial patterns of mRNA expression in multiple tissue types across vertebrate species. The method can detect low abundance transcripts and allows processing of hundreds of slides simultaneously. We present this protocol using expression profiling of avian embryonic brain formation as an example.

Knowing the timing, level, cellular localization, and cell type that a gene is expressed in contributes to our understanding of the function of the gene. ...

Detection of Viral RNA by Fluorescence in situ Hybridization (FISH)

Viruses that infect cells elicit specific changes to normal cell functions which serve to divert energy and resources for viral replication. Many aspects of host cell function are commandeered by viruses, usually by the expression of viral gene products that recruit host cell proteins and machineries. Moreover, viruses engineer specific membrane organelles or tag on to mobile vesicles and motor proteins to target regions of the cell (during de novo infection, viruses co-opt molecular motor proteins to target the nucleus; later, during virus assembly, they will hijack cellular machineries that will help in the assembly of viruses). Less is understood on how viruses, in particular those with RNA genomes, coordinate the intracellular trafficking of both protein and RNA components and how they achieve assembly of infectious particles at specific loci in the cell. The study of RNA localization began in earlier work. Developing lower eukaryotic embryos and neuronal cells provided important biological information, and also underscored the importance of RNA localization in the programming of gene expression cascades. The study in other organisms and cell systems has yielded similar important information. Viruses are obligate parasites and must utilise their host cells to replicate. Thus, it is critical to understand how RNA viruses direct their RNA genomes from the nucleus, through the nuclear pore, through the cytoplasm and on to one of its final destinations, into progeny virus particles 1.
FISH serves as a useful tool to identify changes in steady-state localization of viral RNA. When combined with immunofluorescence (IF) analysis 22, FISH/IF co-analyses will provide information on the co-localization of proteins with the viral RNA3. This analysis therefore provides a good starting point to test for RNA-protein interactions by other biochemical or biophysical tests 4,5, since co-localization by itself is not enough evidence to be certain of an interaction. In studying viral RNA localization using a method like this, abundant information has been gained on both viral and cellular RNA trafficking events 6. For instance, HIV-1 produces RNA in the nucleus of infected cells but the RNA is only translated in the cytoplasm. When one key viral protein is missing (Rev) 7, FISH of the viral RNA has revealed that the block to viral replication is due to the retention of the HIV-1 genomic RNA in the nucleus 8. 
Here, we present the method for visual analysis of viral genomic RNA in situ. The method makes use of a labelled RNA probe. This probe is designed to be complementary to the viral genomic RNA. During the in vitro synthesis of the antisense RNA probe, the ribonucleotide that is modified with digoxigenin (DIG) is included in an in vitro transcription reaction. Once the probe has hybridized to the target mRNA in cells, subsequent antibody labelling steps (Figure 1) will reveal the localization of the mRNA as well as proteins of interest when performing FISH/IF.

Detection of Viral RNA by Fluorescence in situ Hybridization FISH

A fluorescence in situ hybridization (FISH) method was developed to visually detect viral genomic RNA using fluorescence microscopy. A probe is made with specificity to the viral RNA that can then be identified using a combination of hybridization and immunofluorescence techniques. This technique offers the advantage of identifying the localization of the viral RNA or DNA at steady-state, providing information on the control of intracellular virus trafficking events.

Viruses  that infect cells elicit specific changes to normal cell functions which serve  to divert energy and resources for viral replication. Many ...

Analysis of Single-cell Gene Transcription by RNA Fluorescent In Situ Hybridization (FISH)

Adhesion of Plasmodium falciparum infected erythrocytes (IE) to human endothelial receptors during malaria infections is mediated by expression of PfEMP1 protein variants encoded by the var genes.
The haploid P. falciparum genome harbors approximately 60 different var genes of which only one has been believed to be transcribed per cell at a time during the blood stage of the infection. How such mutually exclusive regulation of var gene transcription is achieved is unclear, as is the identification of individual var genes or sub-groups of var genes associated with different receptors and the consequence of differential binding on the clinical outcome of P. falciparum infections. Recently, the mutually exclusive transcription paradigm has been called into doubt by transcription assays based on individual P. falciparum transcript identification in single infected erythrocytic cells using RNA fluorescent in situ hybridization (FISH) analysis of var gene transcription by the parasite in individual nuclei of P. falciparum IE1.
Here, we present a detailed protocol for carrying out the RNA-FISH methodology for analysis of var gene transcription in single-nuclei of P. falciparum infected human erythrocytes. The method is based on the use of digoxigenin- and biotin- labeled antisense RNA probes using the TSA Plus Fluorescence Palette System2 (Perkin Elmer), microscopic analyses and freshly selected P. falciparum IE. The in situ hybridization method can be used to monitor transcription and regulation of a variety of genes expressed during the different stages of the P. falciparum life cycle and is adaptable to other malaria parasite species and other organisms and cell types.

Analysis of Single-cell Gene Transcription by RNA Fluorescent In Situ Hybridization FISH

Fluorescent in situ hybridization (FISH) to identify mRNA transcripts in individual cells allows analysis of polygenic activity such as the simultaneous transcription of more than one member of the var multigene family in Plasmodium falciparum infected erythrocytes 1. The technique is adaptable and can be used on different types of genes, cells and organisms.

Adhesion of Plasmodium falciparum infected erythrocytes (IE) to human endothelial receptors during malaria infections is mediated by expression of PfEMP1 ...

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

Mammalian DNA replication initiates at multiple sites along chromosomes at different times during S phase, following a temporal replication program. The specification of replication timing is thought to be a dynamic process regulated by tissue-specific and developmental cues that are responsive to epigenetic modifications. However, the mechanisms regulating where and when DNA replication initiates along chromosomes remains poorly understood. Homologous chromosomes usually replicate synchronously, however there are notable exceptions to this rule. For example, in female mammalian cells one of the two X chromosomes becomes late replicating through a process known as X inactivation1. Along with this delay in replication timing, estimated to be 2-3 hr, the majority of genes become transcriptionally silenced on one X chromosome. In addition, a discrete cis-acting locus, known as the X inactivation center, regulates this X inactivation process, including the induction of delayed replication timing on the entire inactive X chromosome. In addition, certain chromosome rearrangements found in cancer cells and in cells exposed to ionizing radiation display a significant delay in replication timing of &gt;3 hours that affects the entire chromosome2,3. Recent work from our lab indicates that disruption of discrete cis-acting autosomal loci result in an extremely late replicating phenotype that affects the entire chromosome4. Additional 'chromosome engineering' studies indicate that certain chromosome rearrangements affecting many different chromosomes result in this abnormal replication-timing phenotype, suggesting that all mammalian chromosomes contain discrete cis-acting loci that control proper replication timing of individual chromosomes5.
Here, we present a method for the quantitative analysis of chromosome replication timing combined with fluorescent in situ hybridization. This method allows for a direct comparison of replication timing between homologous chromosomes within the same cell, and was adapted from6. In addition, this method allows for the unambiguous identification of chromosomal rearrangements that correlate with changes in replication timing that affect the entire chromosome. This method has advantages over recently developed high throughput micro-array or sequencing protocols that cannot distinguish between homologous alleles present on rearranged and un-rearranged chromosomes. In addition, because the method described here evaluates single cells, it can detect changes in chromosome replication timing on chromosomal rearrangements that are present in only a fraction of the cells in a population.

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

A quantitative method for the analysis of chromosome replication timing is described. The method utilizes BrdU incorporation in combination with fluorescent in situ hybridization (FISH) to assess replication timing of mammalian chromosomes. This technique allows for the direct comparison of rearranged and un-rearranged chromosomes within the same cell.

Mammalian DNA replication initiates at multiple sites along chromosomes at different times during S phase, following a temporal replication program. The ...

Whole Mount RNA Fluorescent in situ Hybridization of Drosophila Embryos

Assessing the expression pattern of a gene, as well as the subcellular localization properties of its transcribed RNA, are key features for understanding its biological function during development. RNA in situ hybridization (RNA-ISH) is a powerful method used for visualizing RNA distribution properties, be it at the organismal, cellular or subcellular levels 1. RNA-ISH is based on the hybridization of a labeled nucleic acid probe (e.g. antisense RNA, oligonucleotides) complementary to the sequence of an mRNA or a non-coding RNA target of interest 2. As the procedure requires primary sequence information alone to generate sequence-specific probes, it can be universally applied to a broad range of organisms and tissue specimens 3. Indeed, a number of large-scale ISH studies have been implemented to document gene expression and RNA localization dynamics in various model organisms, which has led to the establishment of important community resources 4-11. While a variety of probe labeling and detection strategies have been developed over the years, the combined usage of fluorescently-labeled detection reagents and enzymatic signal amplification steps offer significant enhancements in the sensitivity and resolution of the procedure 12. Here, we describe an optimized fluorescent in situ hybridization method (FISH) employing tyramide signal amplification (TSA) to visualize RNA expression and localization dynamics in staged Drosophila embryos. The procedure is carried out in 96-well PCR plate format, which greatly facilitates the simultaneous processing of large numbers of samples.

Whole Mount RNA Fluorescent in situ Hybridization of Drosophila Embryos

Here we describe a whole-mount fluorescent in situ hybridization (FISH) protocol for determining the expression and localization properties of RNAs expressed during embryogenesis in the fruit fly, Drosophila melanogaster.

Assessing  the expression pattern of a gene, as well as the subcellular localization  properties of its transcribed RNA, are key features for ...

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for using FISH to quantify the number of mRNAs in single yeast cells. Cells can be grown in any condition of interest and then fixed and made permeable. Subsequently, multiple single-stranded deoxyoligonucleotides conjugated to fluorescent dyes are used to label and visualize mRNAs. Diffraction-limited fluorescence from single mRNA molecules is quantified using a spot-detection algorithm to identify and count the number of mRNAs per cell. While the more standard quantification methods of northern blots, RT-PCR and gene expression microarrays provide information on average mRNAs in the bulk population, FISH facilitates both the counting and localization of these mRNAs in single cells at single-molecule resolution.

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

This protocol describes an experimental procedure for performing Fluorescence in situ Hybridization (FISH) for counting mRNAs in single cells at single-molecule resolution.

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for ...

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA probes. This protocol, originally developed by Kloosterman and colleagues for broad use with Exiqon miRNA probes1, has been modified to overcome challenges inherent in miRNA analysis in kidney tissues. These include issues such as structure identification and hard to remove residual probe and antibody. Use of relatively thin, 5 mm thick, tissue sections allowed for clear visualization of kidney structures, while a strong probe signal was retained in cells. Additionally, probe concentration and incubation conditions were optimized to facilitate visualization of microRNA expression with low background and nonspecific signal. Here, the optimized protocol is described, covering the initial tissue collection and preparation through the mounting of slides at the end of the procedure. The basic components of this protocol can be altered for application to other tissues and cell culture models.

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

This article describes an in situ hybridization protocol optimized for colormetric detection of microRNA expression in formalin fixed kidney sections.

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA ...

Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

DNA in situ hybridization (DNA ISH) is a commonly used method for mapping sequences to specific chromosome regions. This approach is particularly effective at mapping highly repetitive sequences to heterochromatic regions, where computational approaches face prohibitive challenges. Here we describe a streamlined protocol for DNA ISH that circumvents formamide washes that are standard steps in other DNA ISH protocols. Our protocol is optimized for hybridization with short single strand DNA probes that carry fluorescent dyes, which effectively mark repetitive DNA sequences within heterochromatic chromosomal regions across a number of different insect tissue types. However, applications may be extended to use with larger probes and visualization of single copy (non-repetitive) DNA sequences. We demonstrate this method by mapping several different repetitive sequences to squashed chromosomes from Drosophila melanogaster neural cells and Nasonia vitripennis spermatocytes. We show hybridization patterns for both small, commercially synthesized probes and for a larger probe for comparison. This procedure uses simple laboratory supplies and reagents, and is ideal for investigators who have little experience with performing DNA ISH.

Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

Here, we present a simple method for performing fluorescence DNA in situ hybridization (DNA ISH) to visualize repetitive heterochromatic sequences on slide-mounted chromosomes. The method requires minimal reagents and it is versatile for use with short or long probes, different tissues, and detection with fluorescence or non-fluorescence-based signals.