Our work is supported by grants from NIH/NIGMS, NSF, USDA/NIFA, and BARD to VC.

Background
Symplastic transport of macromolecules through plant intercellular connections, the plasmodesmata, is of interest to many plant pathologists and biologists. For example, several viral proteins are known to regulate plasmodesmal size exclusion limits to enable viral movement1-3. Also, some endogenous proteins, among them important developmental regulators, are assumed to move from cell to cell, presumably through plasmodesmata, to function non-cell-autonomously4. Thus, a reliable methodology to identify and visualize macromolecular transport between plant cells is much in demand.
1)Grow the target plants
For high transformation efficiency, healthy, robust plants should be used.
1. Arabidopsis plants 
Grow one Arabidopsis plant on Pro-Mix BX in a pot (10 cm x 10 cm x 10 cm) in an environment-controlled chamber with a short photoperiod (8 hr of 130-150 &mu;E m-2 s-1 light at 23&deg;C/16 hr dark at 20&deg;C) and 40-65% relative humidity for 6 to 8 weeks5. Fertilize them occasionally with commercially available products as described5. Leaves with the size larger than 15 mm x 35 mm (the length measurement includes petiole) are selected for the experiments.
2. N. benthamiana and N. tabacum
Grow one plant on Pro-Mix BX in a pot (20 cm x 20 cm x 20 cm) in an environment-controlled chamber with a long photoperiod (16 hr of 130-150 &mu;E m-2 s-1 light at 23&deg;C/8 hr dark at 20&deg;C) and 40-65% relative humidity for 7 to 10 weeks. Fertilize them occasionally with commercially available products as describe. Leaves with size larger than 50 mm x 70 mm for N. benthamiana, or 100 mm x 125 mm for N. tabacum (these length measurements do not include petiole) are selected for the experiments.
2) Preparation of the Gene Gun Cartridge with DNA-coated Gold Microparticles
The protocol for this experimental step has been described in detail previously6. It is very important to use well purified plasmid DNA at high concentrations (~1 &mu;g/&mu;l) to obtain the highest transformation efficiency for the ease of confocal microscopy analysis during the later stages of the experiment.
For this assay, it is important to ascertain that the prepared cartridge does not transform two or more adjacent cells simultaneously at high frequency, because the numbers of cells associating with a fluorescent signal cluster is used as an indicator of the extent of symplastic transport (i.e., a single cell containing the signal indicates no movement, whereas a multicell signal cluster indicates movement). The quality of the each cartridge can be checked by analyzing the expression of the protein 16-20 hours post bombardment. Our protocol6 produces cartridges that yield multicell expression clusters only in &lt;3% of all expression events in this time frame, thus suitable for this experiment.
3) Biolistic Delivery of DNA-coated Microparticles
<ol>
	<li>Remove the leaves of the same developmental stage (i.e. with the same size and same age, see step 1) with a sharp razor blade and immediately place them with the abaxial sides facing up onto a flat Styrofoam surface. The abaxial side of the leaf represents a better substrate for bombardment due to its lower trichome density and thinner cuticle. Arabidopsis leaves, because of their relatively small size, should be covered with a piece of window screen mesh, and the mesh then secured with pushpins to the Styrofoam surface. Maintaining leaves flat increases the efficiency of the particle delivery and minimizes the damage to the tissue during microbombardment.</li>
	<li>Insert the cartridge with DNA-coated microparticles (prepared in step 1) into the gun. For Arabidopsis, the shooting is performed at pressures of 80-110 psi for 1-&mu;m microparticles, and 140-160 psi for 0.6-&mu;m microparticles. For N. benthamiana and tobacco, the shooting is performed at pressures of 100-120 psi for 1-&mu;m microparticles, and 160-180 psi for 0.6-&mu;m microparticles. For Arabidopsis, we usually utilize one cartridge per leaf, because each leaf has enough surface area only for one shot which spreads microparticles over an area of 10-12 mm in diameter. With larger N. benthamiana and tobacco leaves, multiple bombardments of the same leaf are possible, however, they must be done at the symmetrical positions on each side of the mid-rib to target the leaf areas at the same developmental stage (see Discussion).</li>
	<li>Remove the leaves from the Styrofoam surface and place them into a Petri dish on 3 layers of wet Whatman filter paper, seal the Petri dish with Parafilm, and incubate it at room temperature for 36-48 hr to allow expression of the delivered transgenes and potential cell-to-cell movement of their protein products.</li>
</ol>
4) Imaging of Protein Expression
The fluorescent signal of the transiently expressed tagged proteins is visualized by confocal microscopy. Care should be taken to find optimal microscopy settings for detection of each tested protein. For example, proteins that show limited intracellular accumulation with weak signal intensities, such as the plasmodesmal localization of the Tobacco mosaic virus movement protein (TMV MP)1-3,6, should be observed under a 40X objective lens, which affords higher resolution and sensitivity, whereas proteins that show cytoplasmic distribution with strong signal intensities, such as free YFP, can be visualized under a 10X objective lens with confocal zoom function for faster imaging (see Figure 1).
Symplastic transport is inferred from the appearance of multicell clusters that contain the fluorescent signal. The number of such clusters and number of cells in each cluster is indicative of the extent of cell-to-cell transport. To obtain reliable data, at least 100 expression clusters should be recorded per each experimental system. For example, if the cell-to-cell movement of a protein is compared in two different genetic backgrounds (e.g., wild type and transgenic plants), of a total 200 expression clusters should be recorded. Importantly, experiments, the results of which are to be compared to each other, should be carried out simultaneously.
5. Representative Results
The figure below illustrates representative experiments for detection of symplastic transport of fluorescently tagged proteins. Panels A and B show the typical confocal images that are obtained following microbombardment of a N. benthamiana leaf with a TMV MP-YFP-expressing construct. In panel A, symplastic movement of TMV MP-YFP is observed based on the appearance of multicell clusters of the YFP signal. Not all transiently expressed TMV MP-YFP is able to move as evidenced by single-cell signal in some microbombardments (panel B). Statistically, in &lt;40% of the counted signal clusters, TMV MP-YFP is unable to move between cells whereas in &gt;60% of the clusters, the protein moves between 2-5 cells, with the two-cell spread being the most frequent (ca. ~50% cases) (Figure 1C).
The proteins with relatively small molecular size without innate movement activity can diffuse through PD to move cell-to-cell. For example, free YFP, or 1xYFP (ca. 27 kDa, panel D), spreads between several cells in 30% of the counted clusters (panels C). This non-specific diffusion does not occur for a translational YFP dimmer, or 2xYFP (54 kDa, panel E), which is comparable in size to TMV MP-YFP fusion protein (57 kDa), and which is completely cell-autonomous (Figure 1C).
<img src="/files/ftp_upload/2208/2208fig1.jpg" alt="Figure 1" /> 
Figure 1.Typical results obtained from the symplastic transport assay in N. benthamiana leaf tissues. (A, B) Visualization of TMV MP-YFP. (C) Quantitation of signal clusters. 1xYFP and 2xYFP, free YFP and translational YFP dimer, respectively. (D) Visualization of 1xYFP. (E) Visualization of 2xYFP. In micrographs, the left panels show the YFP signal and the right panels show merged images of YFP (in green) and chloroplast autofluorescence (in white) signals. Images are single confocal sections. Asterisks in the micrographs show the epidermal cells showing YFP signal. Bars = 50 &mu;m.

<ol>
	<li>Waigmann, E., Ueki, S., Trutnyeva, K., 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+ins+and+outs+of+non-destructive+cell-to-cell+and+systemic+movement+of+plant+viruses.+.">The ins and outs of non-destructive cell-to-cell and systemic movement of plant viruses. .</a> Crit Rev Plant Sci. 23, 195-250 (2004).</li><li>Lucas, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+viral+movement+proteins:+agents+for+cell-to-cell+trafficking+of+viral+genomes.">Plant viral movement proteins: agents for cell-to-cell trafficking of viral genomes.</a> Virology. 344, 169-184 (2006).</li><li>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=Plant+viruses+spread+by+diffusion+on+ER-associated+movement-protein-rafts+through+plasmodesmata+gated+by+viral+induced+host+beta-1,3-glucanases.">Plant viruses spread by diffusion on ER-associated movement-protein-rafts through plasmodesmata gated by viral induced host beta-1,3-glucanases.</a> Semin Cell Dev Biol. 20, 1074-1081 (2009).</li><li>Zambryski, P. C., Crawford, 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:+gatekeepers+for+cell-to-cell+transport+of+developmental+signals+in+plants.">Plasmodesmata: gatekeepers for cell-to-cell transport of developmental signals in plants.</a> Annu Rev Cell Dev Biol. 16, 393-421 (2000).</li><li>Rivero-Lepinckas, L., Crist, D., Scholl, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+plants+and+presercation+of+seeds.">Growth of plants and presercation of seeds.</a> Methods Mol Biol. 323, 3-12 (2006).</li><li>Ueki, S., Lacroix, B., Krichevsky, A., 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=Functional+transient+genetic+transformation+of+Arabidopsis+leaves+by+biolistic+bombardment.">Functional transient genetic transformation of Arabidopsis leaves by biolistic bombardment.</a> Nat Protoc. 4, 71-77 (2009).</li><li>Oparka, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple,+but+not+branched,+plasmodesmata+allow+the+nonspecific+trafficking+of+proteins+in+developing+tobacco+leaves.">Simple, but not branched, plasmodesmata allow the nonspecific trafficking of proteins in developing tobacco leaves.</a> Cell. 97, 743-754 (1999).</li><li>Imlau, A., Truernit, E., Sauer, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-to-cell+and+long-distance+trafficking+of+the+green+fluorescent+protein+in+the+phloem+and+symplastic+unloading+of+the+protein+into+sink+tissues.">Cell-to-cell and long-distance trafficking of the green fluorescent protein in the phloem and symplastic unloading of the protein into sink tissues.</a> Plant Cell. 11, 309-322 (1999).</li><li>Gisel, A., Barella, S., Hempel, F. D., Zambryski, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+and+spatial+regulation+of+symplastic+trafficking+during+development+in+Arabidopsis+thaliana+apices.">Temporal and spatial regulation of symplastic trafficking during development in Arabidopsis thaliana apices.</a> Development. 126, 1879-1889 (1999).</li><li>Kim, I., Cho, E., Crawford, K. M., Hempel, F. D., Zambryski, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-to-cell+movement+of+GFP+during+embryogenesis+and+early+seedling+development+in+Arabidopsis.">Cell-to-cell movement of GFP during embryogenesis and early seedling development in Arabidopsis.</a> Proc Natl Acad Sci USA. 102, 2227-2231 (2005).</li><li>Crawford, K. M., Zambryski, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-targeted+and+targeted+protein+movement+through+plasmodesmata+in+leaves+in+different+developmental+and+physiological+states.">Non-targeted and targeted protein movement through plasmodesmata in leaves in different developmental and physiological states.</a> Plant Physiol. 125, 1802-1812 (2001).</li><li>Roberts, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phloem+unloading+in+sink+leaves+of+Nicotiana+benthamiana:+comparison+of+a+fluorescent+solute+with+a+fluorescent+virus.">Phloem unloading in sink leaves of Nicotiana benthamiana: comparison of a fluorescent solute with a fluorescent virus.</a> Plant Cell. 9, 1381-1396 (1997).</li><li>Guenoune-Gelbart, D., Elbaum, M., Sagi, G., Levy, A., 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=Tobacco+mosaic+virus+(TMV)+replicase+and+movement+protein+function+synergistically+in+facilitating+TMV+spread+by+lateral+diffusion+in+the+plasmodesmal+desmotubule+of+Nicotiana+benthamiana.">Tobacco mosaic virus (TMV) replicase and movement protein function synergistically in facilitating TMV spread by lateral diffusion in the plasmodesmal desmotubule of Nicotiana benthamiana.</a> Mol Plant Microbe Interact. 21, 335-345 (2008).</li></ol>

No conflicts of interest declared.

The key for the success of the symplastic transport assay is to obtain high transformation efficiency, which allows production of statistically significant and easily detectible signal clusters. This can be achieved using the leaves harvested from healthy, robust plants, and preparing gold particles coated by a pure and concentrated DNA preparation.
Using the leaves at the same growth stage is also vital for the assay reliability. Plasmodesmal aperture is known to be differentially regulated,...

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<td>Gold microparticles, 1.0 &mu;m in diameter</td>
<td>&nbsp;</td>
<td>Bio-Rad</td>
<td>165-2262</td>
<td>&nbsp;</td>
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<td>Gold microparticles, 0.6 &mu;m in diameter</td>
<td>&nbsp;</td>
<td>Bio-Rad</td>
<td>165-2263</td>
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<td>Spermidine</td>
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<td>Sigma</td>
<td>S0266-1G</td>
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<td>Tefzel tubing</td>
<td>&nbsp;</td>
<td>Bio-Rad</td>
<td>165-2441</td>
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<td>Helios cartridge preparatory station</td>
<td>&nbsp;</td>
<td>Bio-Rad</td>
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<td>Tubing cutter</td>
<td>&nbsp;</td>
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a cell-to-cell macromolecular transport assay in planta utilizing biolistic bombardment

Here, we present a simple and rapid protocol to detect and assess the extent of cell-to-cell macromolecular transport in planta. In this protocol, a fluorescently tagged-protein of interest is transiently expressed in plant tissue following biolistic delivery of its encoding DNA construct. The intra- and intercellular distribution of the tagged protein is then analyzed by confocal microscopy. We describe this technology in detail, providing step-by-step protocols to assay and evaluate the extent of symplastic protein transport in three plant species, Arabidopsis thaliana, Nicotiana benthamiana and N. tabacum (tobacco).

Watch this Scientific Journal Video about A Cell-to-cell Macromolecular Transport Assay in Planta Utilizing Biolistic Bombardment at JoVE.com

A Cell-to-cell Macromolecular Transport Assay in Planta Utilizing Biolistic Bombardment

Macromolecular trafficking between plant cells can be assessed by transiently expressing a fluorescently-tagged protein of interest and analyzing its intra- and intercellular distribution by confocal microscopy.

A Cell-to-cell Macromolecular Transport Assay in Planta Utilizing Biolistic Bombardment

Here, we present a simple and rapid protocol to detect and assess the extent of cell-to-cell macromolecular transport in planta. In this protocol, a ...

a-cell-to-cell-macromolecular-transport-assay-planta-utilizing

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JoVE Journal

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11.8K Views.  State University of New York at Stony Brook. Macromolecular trafficking between plant cells can be assessed by transiently expressing a fluorescently-tagged protein of interest and analyzing its intra- and intercellular distribution by confocal microscopy.

Video: A Cell-to-cell Macromolecular Transport Assay in Planta Utilizing Biolistic Bombardment

Generation of Transgenic C. elegans by Biolistic Transformation

The number of laboratories using the free living nematode C. elegans is rapidly growing. The popularity of this biological model is attributed to a rapid generation time and short life span, easy and inexpensive maintenance, fully sequenced genome, and array of RNAi resources and mutant animals. Additionally, analysis of the C. elegans genome revealed a great similarity between worms and higher vertebrates, which suggests that research in worms could be an important adjunct to studies performed in whole mice or cultured cells. A powerful and important part of worm research is the ability to use transgenic animals to study gene localization and function. Transgenic animals can be created either via microinjection of the worm germline or through the use of biolistic bombardment. Bombardment is a newer technique and is less familiar to a number of labs. Here we describe a simple protocol to generate transgenic worms by biolistic bombardment with gold particles using the Bio-Rad PDS-1000 system. Compared with DNA microinjection into hermaphrodite germline, this protocol has the advantage of not requiring special skills from the operator with regards to identifying worm anatomy or performing microinjection. Further multiple transgenic lines are usually obtained from a single bombardment. Also in contrast to microinjection, biolistic bombardment produces transgenic animals with both extrachromosomal arrays and integrated transgenes. The ability to obtain integrated transgenic lines can avoid the use of mutagenic protocols to integrate foreign DNA. In conclusion, biolistic bombardment can be an attractive method for the generation of transgenic animals, especially for investigators not interested in investing the time and effort needed to become skilled at microinjection.

Generation of Transgenic C. elegans by Biolistic Transformation

Transgenic worms are commonly used in C. elegans research. Described is a simple, yet effective, protocol to introduce transgenes into worms using biolistic bombardment with DNA-coated gold particles. The effort involved and results of bombardment compare favorably with microinjection for the generation of transgenic animals.

The number of laboratories using the free living nematode C. elegans is rapidly growing. The popularity of this biological model is attributed to a rapid ...

Harvesting and Cryo-cooling Crystals of Membrane Proteins Grown in Lipidic Mesophases for Structure Determination by Macromolecular Crystallography

An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at atomic resolution. Presently, there is only one way to capture such information as applied to integral membrane proteins (Figure 1), and the complexes they form, and that method is macromolecular X-ray crystallography (MX). To do MX diffraction quality crystals are needed which, in the case of membrane proteins, do not form readily. A method for crystallizing membrane proteins that involves the use of lipidic mesophases, specifically the cubic and sponge phases1-5, has gained considerable attention of late due to the successes it has had in the G protein-coupled receptor field6-21 (<a href="http://www.mpdb.tcd.ie" target="_blank">www.mpdb.tcd.ie</a>). However, the method, henceforth referred to as the in meso or lipidic cubic phase method, comes with its own technical challenges. These arise, in part, due to the generally viscous and sticky nature of the lipidic mesophase in which the crystals, which are often micro-crystals, grow. Manipulating crystals becomes difficult as a result and particularly so during harvesting22,23. Problems arise too at the step that precedes harvesting which requires that the glass sandwich plates in which the crystals grow (Figure 2)24,25 are opened to expose the mesophase bolus, and the crystals therein, for harvesting, cryo-cooling and eventual X-ray diffraction data collection.
The cubic and sponge mesophase variants (Figure 3) from which crystals must be harvested have profoundly different rheologies4,26. The cubic phase is viscous and sticky akin to a thick toothpaste. By contrast, the sponge phase is more fluid with a distinct tendency to flow. Accordingly, different approaches for opening crystallization wells containing crystals growing in the cubic and the sponge phase are called for as indeed different methods are required for harvesting crystals from the two mesophase types. Protocols for doing just that have been refined and implemented in the Membrane Structural and Functional Biology (MS&amp;FB) Group, and are described in detail in this JoVE article (Figure 4). Examples are given of situations where crystals are successfully harvested and cryo-cooled. We also provide examples of cases where problems arise that lead to the irretrievable loss of crystals and describe how these problems can be avoided. In this article the Viewer is provided with step-by-step instructions for opening glass sandwich crystallization wells, for harvesting and for cryo-cooling crystals of membrane proteins growing in cubic and in sponge phases.

Herein is described procedures implemented in the Caffrey Membrane Structural and Functional Biology Group to harvest and cryo-cool membrane protein crystals grown in lipidic cubic and sponge phases for use in structure determination using macromolecular X-ray crystallography.

An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at ...

In Vitro Analysis of PDZ-dependent CFTR Macromolecular Signaling Complexes

Cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel located primarily at the apical membranes of epithelial cells, plays a crucial role in transepithelial fluid homeostasis1-3. CFTR has been implicated in two major diseases: cystic fibrosis (CF)4 and secretory diarrhea5. In CF, the synthesis or functional activity of the CFTR Cl- channel is reduced. This disorder affects approximately 1 in 2,500 Caucasians in the United States6. Excessive CFTR activity has also been implicated in cases of toxin-induced secretory diarrhea (e.g., by cholera toxin and heat stable E. coli enterotoxin) that stimulates cAMP or cGMP production in the gut7.
Accumulating evidence suggest the existence of physical and functional interactions between CFTR and a growing number of other proteins, including transporters, ion channels, receptors, kinases, phosphatases, signaling molecules, and cytoskeletal elements, and these interactions between CFTR and its binding proteins have been shown to be critically involved in regulating CFTR-mediated transepithelial ion transport in vitro and also in vivo8-19. In this protocol, we focus only on the methods that aid in the study of the interactions between CFTR carboxyl terminal tail, which possesses a protein-binding motif [referred to as PSD95/Dlg1/ZO-1 (PDZ) motif], and a group of scaffold proteins, which contain a specific binding module referred to as PDZ domains. So far, several different PDZ scaffold proteins have been reported to bind to the carboxyl terminal tail of CFTR with various affinities, such as NHERF1, NHERF2, PDZK1, PDZK2, CAL (CFTR-associated ligand), Shank2, and GRASP20-27. The PDZ motif within CFTR that is recognized by PDZ scaffold proteins is the last four amino acids at the C terminus (i.e., 1477-DTRL-1480 in human CFTR)20. Interestingly, CFTR can bind more than one PDZ domain of both NHERFs and PDZK1, albeit with varying affinities22. This multivalency with respect to CFTR binding has been shown to be of functional significance, suggesting that PDZ scaffold proteins may facilitate formation of CFTR macromolecular signaling complexes for specific/selective and efficient signaling in cells16-18.
Multiple biochemical assays have been developed to study CFTR-involving protein interactions, such as co-immunoprecipitation, pull-down assay, pair-wise binding assay, colorimetric pair-wise binding assay, and macromolecular complex assembly assay16-19,28,29. Here we focus on the detailed procedures of assembling a PDZ motif-dependent CFTR-containing macromolecular complex in vitro, which is used extensively by our laboratory to study protein-protein or domain-domain interactions involving CFTR16-19,28,29.

In Vitro Analysis of PDZ-dependent CFTR Macromolecular Signaling Complexes

Cystic fibrosis transmembrane conductance regulator (CFTR), an epithelial chloride channel, has been reported to interact with various proteins and regulate important cellular processes; among them the CFTR PDZ motif-mediated interactions have been well documented. This protocol describes methods we developed to assemble a PDZ-dependent CFTR macromolecular signaling complex in vitro.

Cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel located primarily at the apical membranes of epithelial cells, plays a ...

Culturing Caenorhabditis elegans in Axenic Liquid Media and Creation of Transgenic Worms by Microparticle Bombardment

In this protocol, we present the required materials, and the procedure for making modified&#160;C. elegans&#160;Habituation and Reproduction media (mCeHR). Additionally, the steps for exposing and acclimatizing C. elegans grown on E. coli to axenic liquid media are described. Finally, downstream experiments that utilize axenic C. elegans illustrate the benefits of this procedure. The ability to analyze and determine C. elegans&#160;nutrient requirement was illustrated by growing N2 wild type worms in axenic liquid media with varying heme concentrations. This procedure can be replicated with other nutrients to determine the optimal concentration for worm growth and development or, to determine the toxicological effects of drug treatments. The effects of varied heme concentrations on the growth of wild type worms were determined through qualitative microscopic observation and by quantitating the number of worms that grew in each heme concentration. In addition, the effect of varied nutrient concentrations can be assayed by utilizing worms that express fluorescent sensors that respond to changes in the nutrient of interest. Furthermore, a large number of worms were easily produced for the generation of transgenic C. elegans using microparticle bombardment.

Culturing Caenorhabditis elegans in Axenic Liquid Media and Creation of Transgenic Worms by Microparticle Bombardment

C. elegans is usually grown on solid agar plates or in liquid cultures seeded with E. coli. To prevent bacterial byproducts from confounding toxicological and nutritional studies, we utilized an axenic liquid medium, CeHR, to grow and synchronize a large number of worms for a range of downstream applications.

In this protocol, we present the required materials, and the procedure for making modified&#160;C. elegans&#160;Habituation and Reproduction media ...

Open Source High Content Analysis Utilizing Automated Fluorescence Lifetime Imaging Microscopy

We present an open source high content analysis instrument utilizing automated fluorescence lifetime imaging (FLIM) for assaying protein interactions using F&#246;rster resonance energy transfer (FRET) based readouts of fixed or live cells in multiwell plates. This provides a means to screen for cell signaling processes read out using intramolecular FRET biosensors or intermolecular FRET of protein interactions such as oligomerization or heterodimerization, which can be used to identify binding partners. We describe here the functionality of this automated multiwell plate FLIM instrumentation and present exemplar data from our studies of HIV Gag protein oligomerization and a time course of a FRET biosensor in live cells. A detailed description of the practical implementation is then provided with reference to a list of hardware components and a description of the open source data acquisition software written in &#181;Manager. The application of FLIMfit, an open source MATLAB-based client for the OMERO platform, to analyze arrays of multiwell plate FLIM data is also presented. The protocols for imaging fixed and live cells are outlined and a demonstration of an automated multiwell plate FLIM experiment using cells expressing fluorescent protein-based FRET constructs is presented. This is complemented by a walk-through of the data analysis for this specific FLIM FRET data set.

We present an open source high content analysis (HCA) instrument utilizing automated fluorescence lifetime imaging (FLIM) for assaying protein interactions using F&#246;rster resonance energy transfer (FRET) based readouts. Data acquisition for this openFLIM-HCA instrument is controlled by software written in &#181;Manager and data analysis is undertaken in FLIMfit.

We present an open source high content analysis instrument utilizing automated fluorescence lifetime imaging (FLIM) for assaying protein interactions ...

Optimization of Crystal Growth for Neutron Macromolecular Crystallography

The use of neutron macromolecular crystallography (NMX) is expanding rapidly with most structures determined in the last decade thanks to new NMX beamlines having been built and increased availability of structure refinement software. However, the neutron sources currently available for NMX are significantly weaker than equivalent sources for X-ray crystallography. Despite advances in this field, significantly larger crystals will always be required for neutron diffraction studies, particularly with the tendency to study ever-larger macromolecules and complexes. Further improvements in methods and instrumentation suited to growing larger crystals are therefore necessary for the use of NMX to expand.
In this work, we introduce rational strategies and a crystal growth bench (OptiCrys) developed in our laboratory that combines real-time observation through a microscope-mounted video camera with precise automated control of crystallization solutions (e.g., precipitant concentration, pH, additive, temperature). We then demonstrate how this control of temperature and chemical composition facilitates the search for optimal crystallization conditions using model soluble proteins. Thorough knowledge of the crystallization phase diagram is crucial for selecting the starting position and the kinetic path for any crystallization experiment. We show how a rational approach can control the size and number of crystals generated based on knowledge of multidimensional phase diagrams.

Structural studies of biomacromolecules by crystallography require high-quality crystals. Here we demonstrate a protocol that can be used by OptiCrys (a fully automated instrument developed in our lab) and/or microdialysis buttons for growing large high-quality crystals based on knowledge of the crystallization phase diagram.

The use of neutron macromolecular crystallography (NMX) is expanding rapidly with most structures determined in the last decade thanks to new NMX ...

Simultaneous Live Imaging of Multiple Insect Embryos in Sample Chamber-Based Light Sheet Fluorescence Microscopes

Light sheet-based fluorescence microscopy offers efficient solutions to study complex processes on multiple biologically relevant scales. Sample chamber-based setups, which are specifically designed to preserve the three-dimensional integrity of the specimen and usually feature sample rotation, are the best choice in developmental biology. For instance, they have been used to document the entire embryonic morphogenesis of the fruit fly Drosophila melanogaster and the red flour beetle Tribolium castaneum. However, many available live imaging protocols provide only experimental frameworks for single embryos. Especially for comparative studies, such approaches are inconvenient, since sequentially imaged specimens are affected by ambient variance. Further, this limits the number of specimens that can be assayed within a given time. We provide an experimental framework for simultaneous live imaging that increases the throughput in sample chamber-based setups and thus ensures&#160;similar ambient conditions for all specimens. Firstly, we provide a calibration guideline for light sheet fluorescence microscopes. Secondly, we propose a mounting method for multiple embryos that is compatible with sample rotation. Thirdly, we provide exemplary three-dimensional live imaging datasets of Drosophila, for which we juxtapose three transgenic lines with fluorescently labeled nuclei, as well as of Tribolium, for which we compare the performance of three transgenic sublines that carry the same transgene, but at different genomic locations. Our protocol is specifically designed for comparative studies as it pro-actively addresses ambient variance, which is always present in sequential live imaging. This is especially important for quantitative analyses and characterization of aberrational phenotypes, which result e.g., from knockout experiments. Further, it increases the overall throughput, which is highly convenient when access to light sheet&#160;fluorescence microscopes is limited. Finally, the proposed mounting method can be adapted for other insect species and further model organisms, e.g., zebrafish, with basically no optimization effort.

Light sheet-based fluorescence microscopy is the most valuable tool in developmental biology. A major issue in comparative studies is ambient variance. Our protocol describes an experimental framework for simultaneous live imaging of multiple specimens and, therefore, addresses this issue pro-actively.

Light sheet-based fluorescence microscopy offers efficient solutions to study complex processes on multiple biologically relevant scales. Sample ...

Investigating Zinc Transport Mechanism in Mammalian Cells with FluoZin-3 Assay

Characterizing Mammalian Zinc Transporters Using an In Vitro Zinc Transport Assay

Transition metals such as Zn2+ ions must be tightly regulated due to their cellular toxicity. Previously, the activity of Zn2+ transporters was measured indirectly by determining the expression level of the transporter under different concentrations of Zn2+. This was done by utilizing immunohistochemistry, measuring mRNA in the tissue, or determining the cellular Zn2+ levels. With the development of intracellular Zn2+ sensors, the activities of zinc transporters are currently primarily determined by correlating changes in intracellular Zn2+, detected using fluorescent probes, with the expression of the Zn2+ transporters. However, even today, only a few labs monitor dynamic changes in intracellular Zn2+ and use it to measure the activity of zinc transporters directly. Part of the problem is that out of the 10 zinc transporters of the ZnT family, except for ZnT10 (transports manganese), only zinc transporter 1 (ZnT1) is localized at the plasma membrane. Therefore, linking the transport activity to changes in the intracellular Zn2+ concentration is hard. This article describes a direct way to determine the zinc transport kinetics using an assay based on a zinc-specific fluorescent dye, FluoZin-3. This dye is loaded into mammalian cells in its ester form and then trapped in the cytosol due to cellular di-esterase activity. The cells are loaded with Zn2+ by utilizing the Zn2+ ionophore pyrithione. The ZnT1 activity is assessed from the linear part of the reduction in fluorescence following the cell washout. The fluorescence measured at an excitation of 470 nm and emission of 520 nm is proportional to the free intracellular Zn2+. Selecting the cells expressing ZnT1 tagged with the mCherry fluorophore allows for monitoring only the cells expressing the transporter. This assay is used to investigate the contribution of different domains of ZnT1 protein to the transport mechanism of human ZnT1, a eukaryotic transmembrane protein that extrudes excess zinc from the cell.

Author Spotlight: Exploring Cellular Zinc Regulation Through ZnT1 Functionality 

Zinc transport has proven challenging to measure due to the weak causal links to protein function and the low temporal resolution. This protocol describes a method for monitoring, with high temporal resolution, Zn2+ extrusion from living cells by utilizing a Zn2+ sensitive fluorescent dye, thus providing a direct measure of Zn2+ efflux.

Transition metals such as Zn2+ ions must be tightly regulated due to their cellular toxicity. Previously, the activity of Zn2+ transporters was measured ...

Developing Gene Transformation and Editing Methods in Bamboo

In Planta Gene Expression and Gene Editing in Moso Bamboo Leaves

A novel in planta gene transformation method was developed for bamboo, which avoids the need for time-consuming and labor-intensive callus induction and regeneration processes. This method involves Agrobacterium-mediated gene expression via wounding and vacuum for bamboo seedlings. It successfully demonstrated the expression of exogenous genes, such as the RUBY reporter and Cas9 gene, in bamboo leaves. The highest transformation efficiency for the accumulation of betalain in RUBY seedlings was achieved using the GV3101 strain, with a percentage of 85.2% after infection. Although the foreign DNA did not integrate into the bamboo genome, the method was efficient in expressing the exogenous genes. Furthermore, a gene editing system has also been developed with a native reporter using this method, from which an in situ mutant generated by the edited bamboo violaxanthin de-epoxidase gene (PeVDE) in bamboo leaves, with a mutation rate of 17.33%. The mutation of PeVDE resulted in decreased non-photochemical quenching (NPQ) values under high light, which can be accurately detected by a fluorometer. This makes the edited PeVDE a potential native reporter for both exogenous and endogenous genes in bamboo. With the reporter of PeVDE, a cinnamoyl-CoA reductase gene was successfully edited with a mutation rate of 8.3%. This operation avoids the process of tissue culture or callus induction, which is quick and efficient for expressing exogenous genes and endogenous gene editing in bamboo. This method can improve the efficiency of gene function verification and will help reveal the molecular mechanisms of key metabolic pathways in bamboo.

Author Spotlight: Advancing Gene Editing in Bamboo Leaves for Sustainable Plastic Alternatives 

In this study, a novel in planta gene expression and gene editing method mediated by Agrobacterium was developed in bamboo. This method greatly improved the efficiency of gene function validation in bamboo, which has significant implications for accelerating the process of bamboo breeding.

A novel in planta gene transformation method was developed for bamboo, which avoids the need for time-consuming and labor-intensive callus induction and ...

In Planta Transient Transformation of Cacao Plants Using Agrobacterium tumefaciens

Vacuum-Forced Agroinfiltration for In planta Transformation of Recalcitrant Plants: Cacao as a Case Study

Transient in planta transformation is a fast and cost-effective alternative for plant genetic transformation. Most protocols for in planta transformation rely on the use of Agrobacterium-mediated transformation. However, the protocols currently in use are standardized for small-sized plants due to the physical and economic constraints of submitting large-sized plants to a vacuum treatment. This work presents an effective protocol for localized vacuum-based agroinfiltration customized for large-sized plants. To assess the efficacy of the proposed method, we tested its use in cacao plants, a tropical plant species recalcitrant to genetic transformation. Our protocol allowed applying up to 0.07 MPa vacuum, with repetitions, to a localized aerial part of cacao leaves, making it possible to force the infiltration of Agrobacterium into the intercellular spaces of attached leaves. As a result, we achieved the Agrobacterium-mediated transient in planta transformation of attached cacao leaves expressing for the RUBY reporter system. This is also the first Agrobacterium-mediated in planta transient transformation of cacao. This protocol would allow the application of the vacuum-based agroinfiltration method to other plant species with similar size constraints and open the door for the in planta characterization of genes in recalcitrant woody, large-size species.

Author Spotlight: Tissue Culture-Free Agrobacterium-Mediated Transformation in Large Woody Plants

Here, we present the first protocol for localized vacuum infiltration for in vivo studies of the genetic transformation of large-sized plants. Using this methodology, we achieved for the first time the Agrobacterium-mediated in planta transient transformation of cacao.

Transient in planta transformation is a fast and cost-effective alternative for plant genetic transformation. Most protocols for in planta transformation ...