Name: efficient agroinfiltration of plants for high-level transient expression of recombinant proteins
Uploaded: 2013-07-23T12:00:00
Description: Watch this Scientific Journal Video about Efficient Agroinfiltration of Plants for High-level Transient Expression of Recombinant Proteins at JoVE.com

We thank R. Sun and other students of Chen's Laboratory for their contribution to plant material generation. We also thank Dr. D. Green for his support of undergraduate research in the College of Technology and Innovation (CTI). This research was supported in part by NIH grants U01 AI075549 and 1R21AI101329 to Q. Chen, and a SSE grant from CTI of Arizona State University to Q. Chen. K. Leuzinger, M. Dent, J. Hurtado, and J. Stahnke are undergraduate students supported by the SSE grant.

1. Plant Growth
<ol>
	<li>Place 60 peat pellets into a propagation tray. Add 4 L of tap water and let the peat pellets absorb the water for 2 hr.</li>
	<li>Add 2 N. benthamiana seeds into each peat pellet using a seeder, cover the tray with a transparent plastic dome, and allow them to germinate in a 25 &deg;C, 84% humidity environment with a 16/8 hr day/night cycle (Figure 1A).</li>
	<li>Remove the dome two weeks after seeding, drain water from the tray, and add 2 L of Jack's fertilizer at a ...

<ol>
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Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemistry,+mutagenesis,+and+oligomerization+of+DsRed,+a+red+fluorescent+protein+from+coral.">Biochemistry, mutagenesis, and oligomerization of DsRed, a red fluorescent protein from coral.</a> Proceedings of the National Academy of Sciences. 97, 11984-11989 (2000).</li><li>Lai, H., He, J., Engle, M., Diamond, M. 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Bioeng. 106, 9-17 (2010).</li><li>Kuta, D., Tripathi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Agrobacterium-induced+hypersensitive+necrotic+reaction+in+plant+cells:+a+resistance+response+against+Agrobacterium-mediated+DNA+transfer.">Agrobacterium-induced hypersensitive necrotic reaction in plant cells: a resistance response against Agrobacterium-mediated DNA transfer.</a> African Journal of Biotechnology. 4, 752-757 (2005).</li><li>Phoolcharoen, W., 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=Expression+of+an+immunogenic+Ebola+immune+complex+in+Nicotiana+benthamiana.">Expression of an immunogenic Ebola immune complex in Nicotiana benthamiana.</a> Plant Biotechnology Journal. 9, 807-816 (2011).</li><li>Phoolcharoen, W., 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+nonreplicating+subunit+vaccine+protects+mice+against+lethal+Ebola+virus+challenge.">A nonreplicating subunit vaccine protects mice against lethal Ebola virus challenge.</a> Proceedings of the National Academy of Sciences. 108, 20695-20700 (2011).</li><li>Herbst-Kralovetz, M., Mason, H. S., Chen, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Norwalk+virus-like+particles+as+vaccines.">Norwalk virus-like particles as vaccines.</a> Expert Rev. Vaccines. 9, 299-307 (2010).</li><li>Chen, Q., 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=Agroinfiltration+as+an+effective+and+scalable+strategy+of+gene+delivery+for+production+of+pharmaceutical+proteins.">Agroinfiltration as an effective and scalable strategy of gene delivery for production of pharmaceutical proteins.</a> Adv. Tech. Biol. Med. 1, 103 (2013).</li></ol>

The increasing demands for protein-based pharmaceuticals worldwide require new production platforms that are robust, scalable, low-cost and safe. Plants have shown to be one of the most promising alternative production systems for pharmaceutical protein production. In recent years, the development of deconstructed virus-based vectors has enabled transient expression of proteins in plants, which greatly enhances the speed and yield of plant expression systems 2,10. To further optimize the utility of the transie...

Since the 1970s, plants have been explored as alternatives to mammalian, insect, and bacterial cell cultures for the commercial production of recombinant proteins and protein therapeutics 1. Plant-based systems for the expression of biopharmaceuticals have shown promise in recent years as several novel treatments for diseases, like Gaucher's Disease 2, and avian H5N1 influenza 3, have shown success in clinical trials. The development of competent mechanisms for recombinant protein expression in plants in the decades since those initial experiments has created the potential for plant-based systems to alter the current paradigm of protein production for three primary reasons. Firstly, there is a notable decrease in cost as mammalian, insect, and bacterial bioreactors require considerable startup costs, expensive growth media, and complicated processes for downstream purification 4. The creation of stable transgenic plant lines also allows them to outpace the scalability of other expression systems as protein expressing plants could be grown and harvested on an agricultural scale 5. Secondly, plant-based expression systems significantly reduce the risk of transmitting a human or animal pathogen from the protein-expressing host to humans, demonstrating superiority in public safety 6. Lastly, plants utilize a eukaryotic endomembrane system that is similar to mammalian cells, allowing for proper post-translational modification of proteins including glycosylation and the assembly of multiple-subunit proteins 7. This ability puts plant-based systems ahead of those based on prokaryotic systems, such as bacteria, since a wider number of pharmaceutical recombinant proteins, including monoclonal antibodies (mAbs), have a more complicated structure and require extensive posttranslational modifications or assembly 8.
There are two major approaches to expressing recombinant proteins in plants. The first is the development of a stably transgenic line, where DNA coding for the target protein is cloned into an expression cassette and introduced to either the nuclear or chloroplast genomes. In doing so, the foreign DNA becomes heritable through succeeding generations and allows for tremendously improved scalability, far beyond that of other expression systems 1. Introduction of exogenous DNA to the nuclear genome is usually achieved by Agrobacterium tumefaciens infection of plant tissue or, less often, by microprojectile bombardment of the tissue 9. Plant hormones are then used to induce differentiation and growth of transgenic plant tissue such as roots and leaves. Transformation of the chloroplast genome cannot be achieved with A. tumefaciens, but relies entirely on gold or tungsten particles coated with DNA fired ballistically into plant cells. The second method of expressing recombinant protein in plants is through transient expression 10. In this scenario, virus-derived vectors harboring the gene of interest are delivered via A. tumefaciens to fully developed plants through a process called agroinfiltration. Instead of integrating into the plant genome, the delivered gene construct will then begin to direct the transient production of the desired protein, which can be harvested and isolated after a short incubation period. Transient gene expression offers the advantage of greater overall protein accumulation as well as an improved time of protein production, as plants will be ready to harvest approximately 1-2 weeks after agroinfiltration 11. This is significantly faster than the processes of generation, selection, and confirmation of stable transgenic plant lines, which can take several months to a year. This however, is also the limitation of the transient expression system, as it will not yield genetically stable plant lines that can be used to generate a seed bank for large scale commercial production. Despite this, approaches have been developed to improve large scale transient expression. Here we demonstrate one method of generation of transient protein-expressing Nicotiana benthamiana plants using deconstructed viral vectors delivered by A. tumefaciens.
Two major methods are being developed for the delivery of A. tumefaciens into plant tissue: bench scale infiltration via syringe and large scale infiltration via vacuum chamber. Both protocols are described here using N. benthamiana, which is closely related to the common tobacco plant, as the host plant for transient expression of two fluorescent proteins: the green fluorescent protein (GFP) from jellyfish Aequorea victoria and the red fluorescent protein from Discosoma coral (DsRed) 12,13. N. benthamiana is the most common host plant for recombinant protein because it is amenable to genetic transformation, can yield high amounts of biomass rapidly, and is a prolific seed producer for scale-up production 14. Another advantage of using N. benthamiana as hosts for protein expression is the availability of a variety of expression vectors 2,5. In this study, two deconstructed viral vectors, one based on a tobacco mosaic virus (TMV) RNA replicon system (MagnICON vectors) and the other derived from the bean yellow dwarf virus (BeYDV) DNA replicon system (geminiviral vectors) 4,11,15-18 , are used to carry the GFP and DsRed gene and deliver them into N. benthamiana cells via A. tumefaciens. Three DNA constructs will be used for GFP or DsRed expression with MagnICON vectors. They include the 5' module (pICH15879) containing the promoter and other genetic elements for driving the expression of the target gene, the 3' module containing the gene of interest (pICH-GFP or pICH-DsRed), and the integrase module (pICH14011) coding for an enzyme that integrates the 5' and 3' modules together upon expression 8,15. Three DNA constructs are also needed for expression with geminiviral vectors. In addition to vectors containing the replicon of the target gene ( pBYGFP or pBYDsRed), a vector coding for the replication protein (pREP110) is required for the amplification of the target replicon 11,14,16. Furthermore, the inclusion of a vector encoding the silencing suppressor p19 from tomato bushy stunt virus is desired for high level target gene expression 11,16.
There are generally three major steps for the introduction of genes of recombinant proteins into plant cells by agroinfiltration including plant growth, A. tumefaciens culture preparation, and infiltration. As every step is critical for the ultimate success of this procedure, therefore, a detailed description for each is provided for both syringe infiltration and vacuum infiltration below.

<table border="1">
		<tbody>
		 <tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Reagents</td>
		 </tr>
		 <tr>
			<td>GFP </td>
			<td>Invitrogen</td>
			<td>V353-20</td>
			<td><a href="http://www.invitrogen.com/" target="_blank">www.invitrogen.com</a> See reference: Lico and Chen, et al 2008</td>
		 </tr>
		 <tr>
			<td>DsRed</td>
			<td>Clontech</td>
			<td>632152</td>
			<td><a href="http://www.clontech.com/" target="_blank">www.clontech.com</a> See reference: Baird and Zacharias, et al 2000</td>
		 </tr>
		 <tr>
			<td>MagnICON Vector</td>
			<td>Icon Genetics</td>
			<td>n/a</td>
			<td><a href="http://www.icongenetics.com/" target="_blank">www.icongenetics.com</a> See reference: giritch and Marillonnet, et al 2006</td>
		 </tr>
		 <tr>
			<td>Geminiviral Vector</td>
			<td>Author's Lab</td>
			<td>n/a</td>
			<td>See reference: Chen and He, et al 2011</td>
		 </tr>
		 <tr>
			<td>N. benthamiana</td>
			<td>Author's Lab</td>
			<td>n/a</td>
			<td><a href="http://www.herbalistics.com.au" target="_blank">herbalistics.com.au</a></td>
		 </tr>
		 <tr>
			<td>Agrobacterium tumefaciens strain gv3101</td>
			<td>Author's Lab</td>
			<td>n/a</td>
			<td>See reference: Lai and Chen 2012</td>
		 </tr>
		 <tr>
			<td>LB Agar Carbenicillin-100, plates</td>
			<td>Sigma</td>
			<td>L0418</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>LB Agar Kanamycin-50, plates</td>
			<td>Sigma</td>
			<td>L0543</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Magnesium sulfate hepa hydrate</td>
			<td>Sigma</td>
			<td>M2773-500 g</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Bacto-Tryptone</td>
			<td>Fisher</td>
			<td>73049-73-7</td>
			<td><a href="http://www.fishersci.com/" target="_blank">www.fishersci.com</a></td>
		 </tr>
		 <tr>
			<td>Bacto Yeast Extract</td>
			<td>Becton, Dickinson &amp; CO.</td>
			<td>REF 212750</td>
			<td><a href="http://www.bd.com/" target="_blank">www.bd.com</a></td>
		 </tr>
		 <tr>
			<td>Difco Nutrient Broth</td>
			<td>Becton, Dickinson &amp; CO.</td>
			<td>REF 234000</td>
			<td><a href="http://www.bd.com/" target="_blank">www.bd.com</a></td>
		 </tr>
		 <tr>
			<td>MES hydrate Buffer</td>
			<td>Sigma</td>
			<td>M8250-1kg</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Carbenicillin</td>
			<td>Sigma</td>
			<td>C1613-1ML</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Kanamycin</td>
			<td>Sigma</td>
			<td>70560-51-9</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Sodium Hydroxide</td>
			<td>Sigma</td>
			<td>221465</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Jack's Fertilizer</td>
			<td>Hummert International</td>
			<td>Jul-25</td>
			<td><a href="http://www.hummert.com/" target="_blank">www.hummert.com</a></td>
		 </tr>
		 <tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		 </tr>
		 <tr>
			<td>Vacuubrand MD4 Vacuum Pump</td>
			<td>Fisher</td>
			<td>13-878-113</td>
			<td><a href="http://www.fishersci.com/" target="_blank">www.fishersci.com</a></td>
		 </tr>
		 <tr>
			<td>Vacuum Air Regulator Valve</td>
			<td>Fisher</td>
			<td>NC9386590</td>
			<td><a href="http://www.fishersci.com/" target="_blank">www.fishersci.com</a></td>
		 </tr>
		 <tr>
			<td>Desiccator 12 1/8" with O ring</td>
			<td>Fisher</td>
			<td>08-594-15C </td>
			<td><a href="http://www.fishersci.com/" target="_blank">www.fishersci.com</a></td>
		 </tr>
		 <tr>
			<td>3 L Tub</td>
			<td>Rubber-Maid</td>
			<td>n/a</td>
			<td>Rubbermaid Servn' Saver Bowl, 10-cup will work</td>
		 </tr>
		 <tr>
			<td>plate/shelf 230ML</td>
			<td>Fisher</td>
			<td>NC9489269</td>
			<td><a href="http://www.fishersci.com/" target="_blank">www.fishersci.com</a></td>
		 </tr>
		 <tr>
			<td>Peat Pellet</td>
			<td>Hummert International</td>
			<td>14-2370-1</td>
			<td><a href="http://www.hummert.com/" target="_blank">www.hummert.com</a></td>
		 </tr>
		 <tr>
			<td>Propagation Tray Dome</td>
			<td>hydrofarm</td>
			<td>132052</td>
			<td><a href="http://www.hydroponics.net/" target="_blank">www.hydroponics.net</a></td>
		 </tr>
		 <tr>
			<td>Propagaiton Tray</td>
			<td>hydrofarm</td>
			<td>138758</td>
			<td><a href="http://www.hydroponics.net/" target="_blank">www.hydroponics.net</a></td>
		 </tr>
		 <tr>
			<td>Virbo Hand Seeder</td>
			<td>Gro-Mor INC</td>
			<td>n/a</td>
			<td><a href="http://www.gro-morent.com/" target="_blank">www.gro-morent.com</a></td>
		 </tr>
		 <tr>
			<td>Flora Cart 4 shelf</td>
			<td>Hummert International</td>
			<td>65-6924-1</td>
			<td><a href="http://www.hummert.com/" target="_blank">www.hummert.com</a></td>
		 </tr>
		 <tr>
			<td>15 ml Round Bottom Culture Tubes</td>
			<td>Sigma</td>
			<td>CLS430172-500EA</td>
			<td><a href="http://www.sigmaaldrich.com/" target="_blank">http://www.sigmaaldrich.com</a></td>
		 </tr>
		 <tr>
			<td>Spectrophotometer</td>
			<td>Bio-Rad</td>
			<td>170-2525</td>
			<td><a href="http://www.bio-rad.com/" target="_blank">www.bio-rad.com</a></td>
		 </tr>
		 <tr>
			<td>Spectrophotometer Cuvettes</td>
			<td>Bio-Rad</td>
			<td>223-9950</td>
			<td><a href="http://www.bio-rad.com/" target="_blank">www.bio-rad.com</a></td>
		 </tr>
		 <tr>
			<td>Microcentrifuge Tubes</td>
			<td>USA Scientific</td>
			<td>1415-2500</td>
			<td><a href="http://www.usascientific.com/" target="_blank">www.usascientific.com</a></td>
		 </tr>
		 <tr>
			<td>Benchtop Centrifuge</td>
			<td>Bio-Rad</td>
			<td>166-0602EDU</td>
			<td><a href="http://www.bio-rad.com/" target="_blank">www.bio-rad.com</a></td>
		 </tr>
		 <tr>
			<td>Incubator/Shaker</td>
			<td>Eppendorf</td>
			<td>Excella E25</td>
			<td><a href="http://www.eppendorf.com/" target="_blank">www.eppendorf.com</a></td>
		 </tr>
		 <tr>
			<td>Ultraviolet Light Model#: UVGL-25</td>
			<td>UVP</td>
			<td>95-0021-12</td>
			<td><a href="http://www.uvp.com/" target="_blank">www.uvp.com</a></td>
		 </tr>
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efficient agroinfiltration of plants for high-level transient expression of recombinant proteins

Mammalian cell culture is the major platform for commercial production of human vaccines and therapeutic proteins. However, it cannot meet the increasing worldwide demand for pharmaceuticals due to its limited scalability and high cost. Plants have shown to be one of the most promising alternative pharmaceutical production platforms that are robust, scalable, low-cost and safe. The recent development of virus-based vectors has allowed rapid and high-level transient expression of recombinant proteins in plants. To further optimize the utility of the transient expression system, we demonstrate a simple, efficient and scalable methodology to introduce target-gene containing Agrobacterium into plant tissue in this study. Our results indicate that agroinfiltration with both syringe and vacuum methods have resulted in the efficient introduction of Agrobacterium into leaves and robust production of two fluorescent proteins; GFP and DsRed. Furthermore, we demonstrate the unique advantages offered by both methods. Syringe infiltration is simple and does not need expensive equipment. It also allows the flexibility to either infiltrate the entire leave with one target gene, or to introduce genes of multiple targets on one leaf. Thus, it can be used for laboratory scale expression of recombinant proteins as well as for comparing different proteins or vectors for yield or expression kinetics. The simplicity of syringe infiltration also suggests its utility in high school and college education for the subject of biotechnology. In contrast, vacuum infiltration is more robust and can be scaled-up for commercial manufacture of pharmaceutical proteins. It also offers the advantage of being able to agroinfiltrate plant species that are not amenable for syringe infiltration such as lettuce and Arabidopsis. Overall, the combination of syringe and vacuum agroinfiltration provides researchers and educators a simple, efficient, and robust methodology for transient protein expression. It will greatly facilitate the development of pharmaceutical proteins and promote science education.

1. Expression of Fluorescent Proteins by Syringe Infiltration
To demonstrate the effectiveness of syringe infiltration of Agrobacterium into plant tissue, we tested the expression of two fluorescent proteins - GFP and DsRed - by two different deconstructed plant viral vectors - geminiviral and MagnICON - in N. benthamiana. For N. benthamiana leaves that were entirely infiltrated with Agrobacteria containing geminiviral vectors, GFP expression was observed over ...

Watch this Scientific Journal Video about Efficient Agroinfiltration of Plants for High-level Transient Expression of Recombinant Proteins at JoVE.com

Efficient Agroinfiltration of Plants for High-level Transient Expression of Recombinant Proteins

Plants offer a novel system for the production of pharmaceutical proteins on a commercial scale that is more scalable, cost-efficient and safe than current expression paradigms. In this study, we report a simple and convenient, yet scalable approach to introduce target-gene containing Agrobacterium tumefaciens into plants for protein transient expression.

Mammalian cell culture is the major platform for commercial production of human vaccines and therapeutic proteins. However, it cannot meet the increasing ...

efficient-agroinfiltration-plants-for-high-level-transient-expression

Research

JoVE Journal

Biology

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Expression of Recombinant Proteins in the Methylotrophic Yeast Pichia pastoris

Protein expression in the microbial eukaryotic host Pichia pastoris offers the possibility to generate high amounts of recombinant protein in a fast and easy to use expression system.
As a single-celled microorganism P. pastoris is easy to manipulate and grows rapidly on inexpensive media at high cell densities. Being a eukaryote, P. pastoris is able to perform many of the post-translational modifications performed by higher eukaryotic cells and the obtained recombinant proteins undergo protein folding, proteolytic processing, disulfide bond formation and glycosylation [1].
As a methylotrophic yeast P. pastoris is capable of metabolizing methanol as its sole carbon source. The strong promoter for alcohol oxidase, AOX1, is tightly regulated and induced by methanol and it is used for the expression of the gene of interest. Accordingly, the expression of the foreign protein can be induced by adding methanol to the growth medium [2; 3].
Another important advantage is the secretion of the recombinant protein into the growth medium, using a signal sequence to target the foreign protein to the secretory pathway of P. pastoris. With only low levels of endogenous protein secreted to the media by the yeast itself and no added proteins to the media, a heterologous protein builds the majority of the total protein in the medium and facilitates following protein purification steps [3; 4].
The vector used here (pPICZ&alpha;A) contains the AOX1 promoter for tightly regulated, methanol-induced expression of the gene of interest; the &alpha;-factor secretion signal for secretion of the recombinant protein, a Zeocin resistance gene for selection in both E. coli and Pichia and a C-terminal peptide containing the c-myc epitope and a polyhistidine (6xHis) tag for detection and purification of a recombinant protein. We also show western blot analysis of the recombinant protein using the specific Anti-myc-HRP antibody recognizing the c-myc epitope on the parent vector.

Expression of Recombinant Proteins in the Methylotrophic Yeast Pichia pastoris

The protocol describes protein expression using the methylotrophic yeast Pichia pastoris. The preparation of electrocompetent yeast cells, transformation of the vector with the gene of interest into P. pastoris and yeast DNA purification are also performed. Western blot analysis and protein purification build the last steps in this protein expression protocol.

Protein expression in the microbial eukaryotic host Pichia pastoris offers the possibility to generate high amounts of recombinant protein in a fast and ...

High-throughput Purification of Affinity-tagged Recombinant Proteins

X-ray crystallography is the method of choice for obtaining a detailed view of the structure of proteins. Such studies need to be complemented by further biochemical analyses to obtain detailed insights into structure/function relationships. Advances in oligonucleotide- and gene synthesis technology make large-scale mutagenesis strategies increasingly feasible, including the substitution of target residues by all 19 other amino acids. Gain- or loss-of-function phenotypes then allow systematic conclusions to be drawn, such as the contribution of particular residues to catalytic activity, protein stability and/or protein-protein interaction specificity.
In order to attribute the different phenotypes to the nature of the mutation - rather than to fluctuating experimental conditions - it is vital to purify and analyse the proteins in a controlled and reproducible manner. High-throughput strategies and the automation of manual protocols on robotic liquid-handling platforms have created opportunities to perform such complex molecular biological procedures with little human intervention and minimal error rates1-5.
Here, we present a general method for the purification of His-tagged recombinant proteins in a high-throughput manner. In a recent study, we applied this method to a detailed structure-function investigation of TFIIB, a component of the basal transcription machinery. TFIIB is indispensable for promoter-directed transcription in vitro and is essential for the recruitment of RNA polymerase into a preinitiation complex6-8. TFIIB contains a flexible linker domain that penetrates the active site cleft of RNA polymerase9-11. This linker domain confers two biochemically quantifiable activities on TFIIB, namely (i) the stimulation of the catalytic activity during the 'abortive' stage of transcript initiation, and (ii) an additional contribution to the specific recruitment of RNA polymerase into the preinitiation complex4,5,12 . We exploited the high-throughput purification method to generate single, double and triple substitution and deletions mutations within the TFIIB linker and to subsequently analyse them in functional assays for their stimulation effect on the catalytic activity of RNA polymerase4. Altogether, we generated, purified and analysed 381 mutants - a task which would have been time-consuming and laborious to perform manually. We produced and assayed the proteins in multiplicates which allowed us to appreciate any experimental variations and gave us a clear idea of the reproducibility of our results.
This method serves as a generic protocol for the purification of His-tagged proteins and has been successfully used to purify other recombinant proteins. It is currently optimised for the purification of 24 proteins but can be adapted to purify up to 96 proteins.

We describe a method for the affinity-tagged purification of recombinant proteins using liquid-handling robotics. This method is generally applicable to the small-scale purification of soluble His-tagged proteins in a high-throughput format.

X-ray crystallography is the method of choice for obtaining a detailed view of the structure of proteins. Such studies need to be complemented by further ...

Efficient Production and Purification of Recombinant Murine Kindlin-3 from Insect Cells for Biophysical Studies

Kindlins are essential coactivators, with talin, of the cell surface receptors&#160;integrins and also participate in integrin outside-in signalling, and the control of gene transcription in the cell nucleus. The kindlins are ~75 kDa multidomain proteins and bind to an NPxY motif and upstream T/S cluster of the integrin &#946;-subunit cytoplasmic tail. The hematopoietically-important kindlin isoform, kindlin-3, is critical for platelet aggregation during thrombus formation, leukocyte rolling in response to infection and inflammation and osteoclast podocyte formation in bone resorption. Kindlin-3&#39;s role in these processes has resulted in extensive cellular and physiological studies. However, there is a need for an efficient method of acquiring high quality milligram quantities of the protein for further studies. We have developed a protocol, here described, for the efficient expression and purification of recombinant murine kindlin-3 by use of a baculovirus-driven expression system in Sf9 cells yielding sufficient amounts of high purity full-length protein to allow its biophysical characterization. The same approach could be taken in the study of the other mammalian kindlin isoforms.

Kindlins are fundamental to cell adhesion through integrins but studies of them have been hampered by the difficulty encountered in expressing them recombinantly in bacterial hosts. We describe here methods for their efficient production in baculovirus-infected insect cells.

Kindlins are essential coactivators, with talin, of the cell surface receptors&#160;integrins and also participate in integrin outside-in signalling, and ...

High Throughput Quantitative Expression Screening and Purification Applied to Recombinant Disulfide-rich Venom Proteins Produced in E. coli

Escherichia coli (E. coli) is the most widely used expression system for the production of recombinant proteins for structural and functional studies. However, purifying proteins is sometimes challenging since many proteins are expressed in an insoluble form. When working with difficult or multiple targets it is therefore recommended to use high throughput (HTP) protein expression screening on a small scale (1-4&#160;ml cultures) to quickly identify conditions for soluble expression. To cope with the various structural genomics programs of the lab, a quantitative (within a range of 0.1-100 mg/L culture of recombinant protein) and HTP protein expression screening protocol was implemented and validated on thousands of proteins. The protocols were automated with the use of a liquid handling robot but can also be performed manually without specialized equipment.
Disulfide-rich venom proteins are gaining increasing recognition for their potential as therapeutic drug leads. They can be highly potent and selective, but their complex disulfide bond networks make them challenging to produce. As a member of the FP7 European Venomics project (<a href="http://www.venomics.eu">www.venomics.eu</a>), our challenge is to develop successful production strategies with the aim of producing thousands of novel venom proteins for functional characterization. Aided by the redox properties of disulfide bond isomerase DsbC, we adapted our HTP production pipeline for the expression of oxidized, functional venom peptides in the E. coli cytoplasm. The protocols are also applicable to the production of diverse disulfide-rich proteins. Here we demonstrate our pipeline applied to the production of animal venom proteins. With the protocols described herein it is likely that soluble disulfide-rich proteins will be obtained in as little as a week. Even from a small scale, there is the potential to use the purified proteins for validating the oxidation state by mass spectrometry, for characterization in pilot studies, or for sensitive micro-assays.

High Throughput Quantitative Expression Screening and Purification Applied to Recombinant Disulfide-rich Venom Proteins Produced in E. coli

A protocol for the quantitative, high throughput expression screening and analytical purification of fusion proteins from small-scale Escherichia coli cultures is described and applied to the expression of disulfide-rich animal venom protein targets.

Escherichia coli (E. coli) is the most widely used expression system for the production of recombinant proteins for structural and functional studies. ...

Transient Expression of Proteins by Hydrodynamic Gene Delivery in Mice

Efficient expression of transgenes in vivo is of critical importance in studying gene function and developing treatments for diseases. Over the past years, hydrodynamic gene delivery (HGD) has emerged as a simple, fast, safe and effective method for delivering transgenes into rodents. This technique relies on the force generated by the rapid injection of a large volume of physiological solution to increase the permeability of cell membranes of perfused organs and thus deliver DNA into cells. One of the main advantages of HGD is the ability to introduce transgenes into mammalian cells using naked plasmid DNA (pDNA). Introducing an exogenous gene using a plasmid is minimally laborious, highly efficient and, contrary to viral carriers, remarkably safe. HGD was initially used to deliver genes into mice, it is now used to deliver a wide range of substances, including oligonucleotides, artificial chromosomes, RNA, proteins and small molecules into mice, rats and, to a limited degree, other animals. This protocol describes HGD in mice and focuses on three key aspects of the method that are critical to performing the procedure successfully: correct insertion of the needle into the vein, the volume of injection and the speed of delivery. Examples are given to show the application of this method to the transient expression of two genes that encode secreted, primate-specific proteins, apolipoprotein L-I (APOL-I) and haptoglobin-related protein (HPR).

In vivo transfection of naked DNA by hydrodynamic gene delivery introduces genes into the tissue of an animal with minimal inflammatory response. Sufficient amounts of gene product are generated such that gene function and regulation as well as protein structure and function can be analyzed.

Efficient expression of transgenes in vivo is of critical importance in studying gene function and developing treatments for diseases. Over the past ...

HeLa Based Cell Free Expression Systems for Expression of Plasmodium Rhoptry Proteins

Malaria causes significant global morbidity and mortality. No routine vaccine is currently available. One of the major reasons for lack of a vaccine is the challenge of identifying suitable vaccine candidates. Malarial proteins expressed using prokaryotic and eukaryotic cell based expression systems are poorly glycosylated, generally insoluble and undergo improper folding leading to reduced immunogenicity. The wheat germ, rabbit reticulocyte lysate and Escherichia coli lysate cell free expression systems are currently used for expression of malarial proteins. However, the length of expression time and improper glycosylation of proteins still remains a challenge. We demonstrate expression of Plasmodium proteins in vitro using HeLa based cell free expression systems, termed &#8220;in vitro human cell free expression systems&#8221;. The 2 HeLa based cell free expression systems transcribe mRNA in 75 min and 3 &#181;l of transcribed mRNA is sufficient to translate proteins in 90 min. The 1-step expression system is a transcription and translation coupled expression system; the transcription and co-translation occurs in 3 hr. The process can also be extended for 6 hr by providing additional energy. In the 2-step expression system, mRNA is first transcribed and then added to the translation mix for protein expression. We describe how to express malaria proteins; a hydrophobic PF3D7_0114100 Maurer&#8217;s Cleft &#8211; 2 transmembrane (PfMC-2TM) protein, a hydrophilic PF3D7_0925900 protein and an armadillo repeats containing protein PF3D7_1361800, using the HeLa based cell free expression system. The proteins are expressed in micro volumes employing 2-step and 1-step expression strategies. An affinity purification method to purify 25 &#181;l of proteins expressed using the in vitro human cell free expression system is also described. Protein yield is determined by Bradford&#8217;s assay and the expressed and purified proteins can be confirmed by western blotting analysis. Expressed recombinant proteins can be used for immunizations, immunoassays and protein sequencing.

HeLa Based Cell Free Expression Systems for Expression of Plasmodium Rhoptry Proteins

Expression of malarial proteins in cell based systems remains challenging. We demonstrate two step and one step IVT (in vitro translation) cell free expression systems for expressing malarial recombinant rhoptry proteins from HeLa cells. We use a Ni-resin affinity based purification system to purify the rhoptry proteins.

Malaria causes significant global morbidity and mortality. No routine vaccine is currently available. One of the major reasons for lack of a vaccine is ...

High Yield Expression of Recombinant Human Proteins with the Transient Transfection of HEK293 Cells in Suspension

The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and function. The rapid establishment and high recovery from transiently-transfected mammalian cell lines addresses this barrier and is an effective means of expressing proteins that are naturally channeled through the ER and Golgi-mediated secretory pathway. Here is one protocol for protein expression using the human HEK293F and HEK293S cell lines transfected with a mammalian expression vector designed for high protein yields. The applicability of this system is demonstrated using three representative glycoproteins that expressed with yields between 95-120 mg of purified protein recovered per liter of culture. These proteins are the human Fc&#947;RIIIa and the rat &#945;2-6 sialyltransferase, ST6GalI, both expressed with an N-terminal GFP fusion, as well as the unmodified human immunoglobulin G1 Fc. This robust system utilizes a serum-free medium that is adaptable for expression of isotopically enriched proteins and carbohydrates for structural studies using mass spectrometry and nuclear magnetic resonance spectroscopy. Furthermore, the composition of the N-glycan can be tuned by adding a small molecule to prevent certain glycan modifications in a manner that does not reduce yield.

Laboratory-scale production of eukaryotic proteins with appropriate post-translational modification represents a significant barrier. Here is a robust protocol with rapid establishment and turnaround for protein expression using a mammalian expression system. This system supports selective amino acid, selective labeling of proteins and small molecule modulators of glycan composition.

The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and ...

Transient Expression and Cellular Localization of Recombinant Proteins in Cultured Insect Cells

Heterologous protein expression systems are used for the production of recombinant proteins, the interpretation of cellular trafficking/localization, and the determination of the biochemical function of proteins at the sub-organismal level. Although baculovirus expression systems are increasingly used for protein production in numerous biotechnological, pharmaceutical, and industrial applications, nonlytic systems that do not involve viral infection have clear benefits but are often overlooked and underutilized. Here, we describe a method for generating nonlytic expression vectors and transient recombinant protein expression. This protocol allows for the efficient cellular localization of recombinant proteins and can be used to rapidly discern protein trafficking within the cell. We show the expression of four&#160;recombinant proteins in a commercially available insect cell line, including two aquaporin proteins from the insect Bemisia tabaci, as well as subcellular marker proteins specific for the cell plasma membrane and for intracellular lysosomes. All recombinant proteins were produced as chimeras with fluorescent protein markers at their carboxyl termini, which allows for the direct detection of the recombinant proteins. The double transfection of cells with plasmids harboring constructs for the genes of interest and a known subcellular marker allows for live cell imaging and improved validation of cellular protein localization.

Nonlytic insect cell expression systems are underutilized for production, cellular trafficking/localization, and recombinant protein functional analysis. Here, we describe methods to generate expression vectors and subsequent transient protein expression in commercially available lepidopteran cell lines. The co-localization of Bemisia tabaci aquaporins with subcellular fluorescent marker proteins is also presented.

Heterologous protein expression systems are used for the production of recombinant proteins, the interpretation of cellular trafficking/localization, and ...

In Planta Transient Transformation of Cacao Plants Using &lt;em&gt;Agrobacterium tumefaciens&lt;/em&gt;

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 &lt;em&gt;Agrobacterium&lt;/em&gt;-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 ...