The work in the VC laboratory was supported by grants from NIH (R35GM144059), NSF (MCB 1913165 and IOS 1758046), and BARD (IS-5276-20) to VC. The funders had no role in study design, data collection, and interpretation, or the decision to publish.

The details of the reagents and the equipment used in this study are listed in the Table of Materials.
1. Plant growth
<ol>
	<li>Grow Nicotiana benthamiana seeds in wet soil in a controlled environment chamber at 23 &#730;C under 16 h of light and 8 h of darkness.</li>
	<li>After about 2 weeks, carefully transfer the seedlings with the peat pellets around their roots to larger pots and continue growth under the same conditions for 4-5 weeks for the ...

Exploring Plasmodesmata Function: Confocal Microscopy of Targeted Proteins

<ol>
	<li>Lee, 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=A+plasmodesmata-localized+protein+mediates+crosstalk+between+cell-to-cell+communication+and+innate+immunity+in+Arabidopsis.">A plasmodesmata-localized protein mediates crosstalk between cell-to-cell communication and innate immunity in Arabidopsis.</a> The Plant Cell. 23 (9), 3353-3373 (2011).</li><li>Benitez-Alfonso, Y., Faulkner, C., Ritzenthaler, C., Maule, 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=Plasmodesmata+gateways+to+local+and+systemic+virus+infection.">Plasmodesmata gateways to local and systemic virus infection.</a> Mol Plant-Microbe Interact. 23 (11), 1403-1412 (2010).</li><li>Bayer, E. M., Benitez-Alfonso, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmodesmata:+Channels+under+pressure.">Plasmodesmata: Channels under pressure.</a> Annu Rev Plant Biol. 75, 21 (2024).</li><li>Maule, 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=Plasmodesmata:+Structure,+function+and+biogenesis.">Plasmodesmata: Structure, function and biogenesis.</a> Curr Opin Plant Biol. 11, 680-686 (2008).</li><li>Fernandez-Calvino, 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=Arabidopsis+plasmodesmal+proteome.">Arabidopsis plasmodesmal proteome.</a> PLoS One. 6 (4), e18880 (2011).</li><li>Kirk, P., Amsbury, S., German, L., Gaudioso-Pedraza, R., Benitez-Alfonso, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+meta-proteomic+pipeline+for+the+identification+of+plasmodesmata+proteins+and+regulatory+conditions+in+diverse+plant+species.">A comparative meta-proteomic pipeline for the identification of plasmodesmata proteins and regulatory conditions in diverse plant species.</a> BMC Biol. 20, 128 (2022).</li><li>Levy, A., Erlanger, M., Rosenthal, M., Epel, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+plasmodesmata-associated+&#946;-1,3-glucanase+in+Arabidopsis.">A plasmodesmata-associated &#946;-1,3-glucanase in Arabidopsis.</a> The Plant J. 49 (4), 669-682 (2007).</li><li>Kankanala, P., Czymmek, K., Valent, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Roles+for+rice+membrane+dynamics+and+plasmodesmata+during+biotrophic+invasion+by+the+blast+fungus.">Roles for rice membrane dynamics and plasmodesmata during biotrophic invasion by the blast fungus.</a> The Plant Cell. 19 (2), 706-724 (2007).</li><li>Aung, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogenic+bacteria+target+plant+plasmodesmata+to+colonize+and+invade+surrounding+tissues.">Pathogenic bacteria target plant plasmodesmata to colonize and invade surrounding tissues.</a> The Plant Cell. 32 (3), 595-611 (2020).</li><li>Cui, W., Lee, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arabidopsis+callose+synthases+CalS1/8+regulate+plasmodesmal+permeability+during+stress.">Arabidopsis callose synthases CalS1/8 regulate plasmodesmal permeability during stress.</a> Nat Plants. 2 (5), 160 (2016).</li><li>Liu, N. 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=Phytosphinganine+affects+plasmodesmata+permeability+via+facilitating+PDLP5-stimulated+callose+accumulation+in+Arabidopsis.">Phytosphinganine affects plasmodesmata permeability via facilitating PDLP5-stimulated callose accumulation in Arabidopsis.</a> Mol Plant. 13 (1), 128-143 (2020).</li><li>Caillaud, M. 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=The+plasmodesmal+protein+PDLP1+localizes+to+haustoria-associated+membranes+during+downy+mildew+infection+and+regulates+callose+deposition.">The plasmodesmal protein PDLP1 localizes to haustoria-associated membranes during downy mildew infection and regulates callose deposition.</a> PLoS Pathog. 10 (11), e1004496 (2014).</li><li>Li, Z., Su-Ling, L., Christian, M., Walley, J. W., Aung, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmodesmata-located+protein+6+regulates+plasmodesmal+function+in+Arabidopsis+vasculature.">Plasmodesmata-located protein 6 regulates plasmodesmal function in Arabidopsis vasculature.</a> The Plant Cell. , (2024).</li><li>Chen, 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=Arabidopsis+PDLP7+modulated+plasmodesmata+function+is+related+to+BG10-dependent+glucosidase+activity+required+for+callose+degradation.">Arabidopsis PDLP7 modulated plasmodesmata function is related to BG10-dependent glucosidase activity required for callose degradation.</a> Sci Bull. , (2024).</li><li>Simpson, C., Thomas, C., Findlay, K., Bayer, E., Maule, 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=An+Arabidopsis+GPI-anchor+plasmodesmal+neck+protein+with+callose+binding+activity+and+potential+to+regulate+cell-to-cell+trafficking.">An Arabidopsis GPI-anchor plasmodesmal neck protein with callose binding activity and potential to regulate cell-to-cell trafficking.</a> The Plant Cell. 21 (2), 581-594 (2009).</li><li>Thomas, C. L., Bayer, E. M., Ritzenthaler, C., Fernandez-Calvino, L., Maule, 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=Specific+targeting+of+a+plasmodesmal+protein+affecting+cell-to-cell+communication.">Specific targeting of a plasmodesmal protein affecting cell-to-cell communication.</a> PLoS Biol. 6 (1), e7 (2008).</li><li>Lim, G., 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=Plasmodesmata+localizing+proteins+regulate+transport+and+signaling+during+systemic+acquired+immunity+in+plants.">Plasmodesmata localizing proteins regulate transport and signaling during systemic acquired immunity in plants.</a> Cell Host Microbe. 19 (4), 541-549 (2016).</li><li>Sheludko, Y. V., Sindarovska, Y. R., Gerasymenko, I. M., Bannikova, M. A., Kuchuk, N. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+several+Nicotiana+species+as+hosts+for+high-scale+Agrobacterium-mediated+transient+expression.">Comparison of several Nicotiana species as hosts for high-scale Agrobacterium-mediated transient expression.</a> Biotechnol Bioeng. 96 (3), 608-614 (2007).</li><li>Walhout, A. 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=GATEWAY+recombinational+cloning:+Application+to+the+cloning+of+large+numbers+of+open+reading+frames+or+ORFeomes.">GATEWAY recombinational cloning: Application to the cloning of large numbers of open reading frames or ORFeomes.</a> Methods Enzymol. 328, 575-592 (2000).</li><li>Huang, 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=dsRNA-induced+immunity+targets+plasmodesmata+and+is+suppressed+by+viral+movement+proteins.">dsRNA-induced immunity targets plasmodesmata and is suppressed by viral movement proteins.</a> The Plant Cell. 35 (10), 3845-3869 (2023).</li><li>Roberts, I. 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=Dynamic+changes+in+the+frequency+and+architecture+of+plasmodesmata+during+the+sink-source+transition+in+tobacco+leaves.">Dynamic changes in the frequency and architecture of plasmodesmata during the sink-source transition in tobacco leaves.</a> Protoplasma. 218, 31-44 (2001).</li><li>Yuan, C., Lazarowitz, S. G., Citovsky, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+plasmodesmal+localization+signal+of+TMV+MP+is+recognized+by+plant+synaptotagmin+SYTA.">The plasmodesmal localization signal of TMV MP is recognized by plant synaptotagmin SYTA.</a> mBio. 9 (4), e01314-e01318 (2018).</li><li>Ward, S. J., Ramirez, M. D., Neelakantan, H., Walker, E. 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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+tobamovirus+Turnip+vein+clearing+virus+30-kilodalton+movement+protein+localizes+to+novel+nuclear+filaments+to+enhance+virus+infection.">The tobamovirus Turnip vein clearing virus 30-kilodalton movement protein localizes to novel nuclear filaments to enhance virus infection.</a> J Virol. 87 (11), 6428-6440 (2013).</li><li>Yuan, C., Lazarowitz, S. 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Any cell biological studies of plant intercellular communication and cell-to-cell transport during normal plant development and morphogenesis, as well as during plant-pathogen interactions, necessitate the detection and monitoring of the sorting of proteins-both endogenous and pathogen-encoded-to plant intercellular connections, the plasmodesmata (PD). These experiments would be substantially facilitated by using reference proteins, whether endogenous or pathogen-derived, that faithfully and consistently localize to PD, ...

Plasmodesmata (PD) play a fundamental role in controlling plant development, environmental responses, and interactions with viral pathogens through the regulation of intercellular communication1,2. PD initially forms during cytokinesis, with hundreds of PD inserted into the new cell between the two daughter cells, thus supplying the channels for cell-to-cell communication3,4. PD is a membrane-rich structure, containing the endoplasmic reticulum (ER)-derived membrane, a trans-PD desmotubule, in the central part of the pores that are lined by the plasma membrane3,4. Comparative proteomic approaches identified numerous PD functional proteins, including &#946;-1,3-glucanases (BGs), callose synthases (CALSs), plasmodesmata-located proteins (PDLPs), callose-binding proteins (PDCBs), multiple C2 domains transmembrane region proteins (MCTPs)3, and leucine-rich repeat receptor-like kinases (RLK)5. Recently, Kirk et al. developed a tool termed plasmodesmata in silico proteome 1 (PIP1), which made it possible to predict new PD proteins in 22 plant species6. PD varies in permeability and structure during plant development and response to various stresses. Callose (&#946;-1,3-glucan) deposition and hydrolysis at the neck region surrounding the PD is one of the broadly known mechanisms of PD regulation7.
Many pathogenic microbes, including fungi, bacteria, and viruses, can manipulate the PD dilation or structure during their infection2,8,9. Magnaporthe oryzae, the causative agent of rice blast, deploys intracellular invasive hyphae to move from cell to cell through PD8. A bacterial pathogen Pseudomonas syringae pv.&#160;tomato requires an effector protein HopO1-1 for intercellular movement and spread in the host plant through interacting with and destabilizing PDLP7, thus increasing the molecular flux in neighboring cells in Arabidopsis9. However, plant viruses are more versatile in regulating PD during their intercellular transmission, with the viral movement protein (MP) promoting cell-to-cell movement2. Owing to their important function in regulating plant development and growth, as well as their interaction with plant pathogenic microbes, PD has gained increasing attention in recent years. In Arabidopsis thaliana, there are two major types of PD functional proteins, PDLPs (1-8) and PDCBs (1-5), and many of them, e.g., PDLP51,10,11, PDLP112, PDLP613, PDLP714, and PDCB115, were found to play a role in manipulating the PD permeability through regulation of callose deposition. However, some PDLPs were found to have a functional redundancy, e.g., knockout mutants of pdlp1 and pdlp1,2 did not affect the molecular trafficking, although double knockout mutants of pdlp1,3 and pdlp2,3 showed increased plasmodesmal permeability16. Interestingly, downregulation/knockout or over-expression of PDLP5 alone results in an increase or decrease in plasmodesmal permeability, respectively1,17. Recently, Li et al. have found that PDLP5 and PDLP6 function at different cell interfaces13. These results indicate that PDLP5 might have non-redundant functions with other PDLPs.
Due to the critical function of PD in intercellular communication, we developed a protocol for deploying the plant PD proteins PDLP5 and PDCB1 and the viral cell-to-cell movement protein (MP) of the Turnip vein-clearing virus (TVCV) as simple, convenient, and reliable PD markers for cell biology experimentation. For further verification, visualization of PD using aniline blue staining of the sampled tissues proceeded in parallel. The protocols described for PD localization of PDLP5, PDCB1, and TVCV MP can be easily adapted to analyze potential PD localization of any cellular or pathogen-derived proteins in living plants.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>ABT AC 1 phase motor</td>
			<td>BRANDTECH</td>
			<td>&#160;ABF63/4C-7RQ</td>
			<td></td>
		</tr>
		<tr>
			<td>Agrobacterium tumefaciens EHA105</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Contamination control&#160;</td>
			<td>CCI</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gateway BP Clonase II Enzyme mix</td>
			<td>Invitrogen</td>
			<td>#11789020</td>
			<td></td>
		</tr>
		<tr>
			<td>Gateway LR Clonase II Enzyme mix</td>
			<td>Invitrogen</td>
			<td>#11791020</td>
			<td></td>
		</tr>
		<tr>
			<td>GraphPad Prism 8.0.1.</td>
			<td>GraphPad Software Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>National Institutes of Health and the Laboratory for Optical and Computational Instrumentation</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Laser scanning confocal microscope</td>
			<td>Zeiss</td>
			<td>LSM 900</td>
			<td></td>
		</tr>
		<tr>
			<td>Nicotiana benthamiana</td>
			<td>Plant species</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pDONR207</td>
			<td>Invitrogen</td>
			<td>#12213013</td>
			<td></td>
		</tr>
		<tr>
			<td>Q5 High-Fidelity DNA Polymerase</td>
			<td>NEB</td>
			<td>#M0491S</td>
			<td></td>
		</tr>
	</tbody>
</table>

confocal microscopy analysis of protein sorting to plasmodesmata in nicotiana benthamiana

Plasmodesmata are membranous nanopores that connect the cytoplasm of adjacent plant cells and enable the cell-to-cell trafficking of nutrients, macromolecules, as well as invading viruses. Plasmodesmata play fundamental roles in the regulation of intercellular communication, contributing to plant development, environmental responses, and interactions with viral pathogens. Discovering plasmodesmal localization of plant or viral proteins could provide useful functional information about the protein and is important for understanding the mechanisms of plant-virus interactions. To facilitate these studies, we describe a protocol for confocal microscopy-based analysis of different plasmodesmal targeting proteins to select the best plasmodesmal marker for studying the virus-plasmodesmata interactions or plasmodesmal transport. Specifically, the analyses of these events are illustrated using the cell-to-cell movement protein (MP) of the Turnip vein-clearing virus (TVCV), the Arabidopsis Plasmodesmata-Localized Protein 5 (PDLP5) and Plasmodesmata Callose-Binding Protein 1 (PDCB1). The protein plasmodesmal localization data are analyzed in parallel with the global visualization of plasmodesmata using aniline blue staining of the sampled tissues. These approaches can be easily adapted to analyze the plasmodesmal localization of any cellular or pathogen proteins in planta.

Author Spotlight: Microscopic Analysis of Protein Localization at Plasmodesmata in Plants

Confocal Microscopy Analysis of Protein Sorting to Plasmodesmata in Nicotiana benthamiana

My research is focused on the plant various movement, from cell to cell. And I'm trying to understand the mechanisms of the various plant interactions during the local spread after infection. Recently, we found that plasmodesmata-localized protein 5 can move from cell to cell in nicotiana benthamiana.This result will help us to understand the mechanisms of plasmodesmata functions in the future. Knowing a protein's subcellular localization is quite important for learning its function. This protocol provides good plasmodesmata-localized microbes, PDLP5 and TVCV MP, that can be used during protein localization studies.

To facilitate studies of PD function in plant physiology and interactions with pathogens, three simple and reliable reference proteins were developed for PD localization. Two cellular PD proteins and a pathogen-derived MP protein encoded by the plant tobamovirus TVCV were selected. The subcellular localization of these proteins was visualized using an autofluorescent reporter EGFP fused to the C-terminus of each protein. In an alternative approach, PD were visualized using aniline blue staining of the PD-associated callo...

This protocol describes the selection of optimal plasmodesmal markers for confocal microscopy-based analyses of protein targeting to plasmodesmata during virus-plasmodesmata interactions or plasmodesmal transport.

Plasmodesmata are membranous nanopores that connect the cytoplasm of adjacent plant cells and enable the cell-to-cell trafficking of nutrients, ...

confocal-microscopy-analysis-protein-sorting-to-plasmodesmata