Name: chitosan/interfering rna nanoparticle mediated gene silencing in disease vector mosquito larvae
Uploaded: 2015-03-25T13:00:00
Description: Watch this Scientific Journal Video about Chitosan/Interfering RNA Nanoparticle Mediated Gene Silencing in Disease Vector Mosquito Larvae at JoVE.com

Funding from the Kansas Agricultural Experiment Station and K-State Arthropod Genomics Center to KYZ supported the original development of chitosan/dsRNA-mediated gene silencing in A. gambiae19.The A. gambiae work described here was supported in part by R01-AI095842 from NIH/NIAID to KM. Development of chitosan/siRNA-mediated gene silencing in A. aegypti20,21 was supported by NIH/NIAID Award R01-AI081795 to MDS. The contents of this study are solely the responsibility of the authors and do not necessarily represent the official views of the NIH.

1. Mosquito Species and Rearing
<ol>
	<li>Maintain A. gambiae G3 and A. aegypti&#160;Liverpool IB12 strains (used in the representative studies below) or other strains of interest according to standard lab practice or as described previously23,24.</li>
</ol>
2. dsRNA and siRNA Design and Production
<ol>
	<li>Design primers to construct long dsRNA templates specific to the gene of interest. Use the E-RNAi tool25. Produce dsRNA according to the method of c...

<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=Chitosan/double-stranded+RNA+nanoparticle-mediated+RNA+interference+to+silence+chitin+synthase+genes+through+larval+feeding+in+the+African+malaria+mosquito+(Anopheles+gambiae).">Chitosan/double-stranded RNA nanoparticle-mediated RNA interference to silence chitin synthase genes through larval feeding in the African malaria mosquito (Anopheles gambiae).</a> Insect molecular biology. 19 (5), 683-693 (2010).</li><li>Mysore, K., Flannery, E. M., Tomchaney, M., Severson, D. 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The chitosan/interfering RNA nanoparticle methodology described herein has been used to effectively target genes during larval development in A. gambiae (Figures&#160;2, 3) and A. aegypti (Figures 4, 5,&#160;6, Tables 1, 2). Chitosan nanoparticles can be prepared with either long dsRNA or siRNA, both of which have been used successfully in mosquitoes as evidenced by the representative results described herein. Synthesis of dsRNA is less...

Blood feeding vector mosquitoes of the Anopheline and Aedine genera transmit disease-causing agents responsible for several of the worst scourges of humankind. An estimated 3.4 billion people are at risk for contracting malaria, which is responsible for over one-half million deaths annually worldwide. Malaria results from infection by Plasmodiumsp. parasites, which are transmitted to people through the bites of infected mosquitoes of the Anopheles genus, including the principal African vector Anopheles gambiae (<a href="http://www.who.int/topics/malaria/en/">http://www.who.int/topics/malaria/en/</a>, 2014)1. Aedes aegypti is the primary mosquito vector for dengue virus, which causes dengue fever, a nonspecific febrile illness that is the most widespread and significant arboviral disease in the world. Dengue virus is presently a threat to &#62;2.5 billion people in the tropics, with a yearly incidence of approximately 50 million cases resulting in ~24,000 deaths annually (<a href="http://www.cdc.gov/dengue/">http://www.cdc.gov/dengue/</a>, 2014)2. Despite the devastating global impact of mosquito-borne illnesses on human health, effective means of preventing and treating these diseases are lacking. Mosquito control is presently the best method of disease prevention.
The potential for controlling arthropod-borne diseases by the genetic manipulation of vector insects has been recognized for over four decades3. Transgenic strains of A. aegypti engineered to have a repressible female-specific flightless phenotype have recently made the potential for using transgenic vector control strategies a reality4-6. These advancements have challenged researchers to identify novel genetic targets for vector control and additional means of manipulating gene function in vector mosquitoes. Alteration of gene expression during development, as was the case in female-flightless mosquitoes4, may promote the elucidation of novel vector control strategies. However, largely due to technical challenges, the functions of very few genes have been characterized during development of A. gambiae, A. aegypti, or other mosquito species.
Since its discovery in C. elegans7, RNA interference (RNAi), which is conserved in animals, plants, and microorganisms, has been extensively used for functional genetic studies in a wide variety of organisms, including insects8,9. The RNAi pathway is initiated by Dicer, which cleaves long dsRNA into short 20-25 nucleotide-long siRNAs that function as sequence-specific interfering RNA. siRNAs silence genes that are complementary in sequence by promoting transcript turnover, cleavage, and disruption of translation9. Long dsRNA molecules (typically 300-600 bp) or custom siRNAs targeting a particular sequence can be used in the research laboratory for silencing any gene of interest. By managing when interfering RNA is delivered, researchers can control the time at which gene silencing initiates. This advantage is useful as it can be used to overcome challenges such as developmental lethality or sterility, which can hinder the production and maintenance of strains bearing heritable mutations, an expensive and labor-intensive process that is not yet available in all insect species. Although the degree of gene silencing by RNAi can vary from gene to gene, tissue to tissue, and animal to animal, RNAi is widely used for functional analysis of genes in mosquitoes and other insects8,9.
Three interfering RNA delivery strategies have been used in mosquitoes: microinjection, soaking/topical application, and ingestion. For a detailed history and comparison of the use of these three techniques in insects, please refer to Yu et al8. We have successfully used microinjection10 as a means of delivering siRNAs to target developmental genes in A. aegypti embryos, larvae, and pupae11-14. However, this labor-intensive delivery strategy requires both a microinjection setup and a skilled hand. Moreover, microinjection is stressful to the organism, a confounding factor, particularly when behavioral phenotypes will be assessed. Finally, microinjection delivery cannot be extended to the field for vector control. As an alternative, soaking the organism in interfering RNA solution has also become a popular means of inducing gene silencing, as it is convenient and requires little equipment or labor. Soaking has primarily been applied in insect cell line studies8, but in a recent study, knockdown was achieved in A. aegypti larvae immersed in a solution of dsRNA15, which the animals appeared to be ingesting. However, for studies involving analysis of multiple experimental groups or phenotypes, soaking is rather costly. Lopez-Martinez et al.16 described rehydration driven RNAi, a novel approach for interfering RNA delivery that involves dehydration in saline solution and rehydration with a single drop of water containing interfering RNA. This approach does cut the costs associated with whole animal immersion, but is more expensive than microinjection and may be limited in its application to species that can tolerate high osmotic pressures. Moreover, it is difficult to envision how immersion or dehydration/rehydration immersion methodology could be adapted for vector control in the field. For these reasons, for post-embryonic studies, delivery of interfering RNA with ingested food is a viable alternative strategy.
Although ingestion-based strategies do not work in all insect species, perhaps most notably Drosophila melanogaster, oral delivery of interfering RNA mixed with food has promoted gene silencing in a variety of insects8,17, including A. aegypti adults18. We described chitosan nanoparticle-mediated RNAi in A. gambiae larvae19 and have successfully applied this approach for reduction of gene expression in A. aegypti larvae20,21. Here, methodology for this RNAi procedure, which involves entrapping of interfering RNA by the polymer chitosan, is detailed. Chitosan/interfering RNA nanoparticles are formed by self-assembly of polycations with interfering RNA through the electrostatic forces between positive charges of the amino groups in chitosan and negative charges carried by the phosphate groups on the backbone of interfering RNA19. The procedure described is compatible with both long dsRNA molecules (hereafter referred to as dsRNA) or double stranded siRNA (hereafter referred to as siRNA). Following synthesis, chitosan/interfering RNA nanoparticles are mixed with larval food and delivered to larvae through oral ingestion. This methodology is relatively inexpensive, requires little equipment and labor19, and facilitates high-throughput analysis of multiple phenotypes, including analysis of behaviors20,21. This methodology, which can be adapted for gene silencing studies in other insects, including other disease vectors and insect agricultural pests, could potentially be used for gene silencing in a variety of other animal species. Moreover, chitosan, an inexpensive, non-toxic and biodegradable polymer22, could potentially be utilized in the field for species-specific mosquito control.

<table border="0" cellpadding="0" cellspacing="0" width="1429">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:347px;">Name of Reagent/Equipment</td>
			<td style="width:243px;">Company</td>
			<td style="width:177px;">Catalog Number</td>
			<td style="width:663px;">Comments/Descriptions</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">0.02 ml pipetteman</td>
			<td>Rainin</td>
			<td>PR20</td>
			<td>for resuspension of interfering RNA</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">0.2 ml pipetteman</td>
			<td>Rainin</td>
			<td>PR200</td>
			<td>for resuspension of interfering RNA and preparation of interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">0.5 ml graduated tube&#160;</td>
			<td>Fischer Scientific</td>
			<td>05-408-120</td>
			<td>for aliquoting resuspended interfering RNA</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">1 ml pipetteman</td>
			<td>Rainin</td>
			<td>PR1000</td>
			<td>for resuspension of interfering RNA and preparation of interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">1.5 ml graduated tube&#160;</td>
			<td>Fischer Scientific</td>
			<td>05-408-046</td>
			<td>for preparation of interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">1M Sodium Acetate, pH 4.5</td>
			<td>TEKnova</td>
			<td>S0299</td>
			<td>to prepare sodium acetate buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetic Acid, AIRSTAR. ACS, USP, FCC Grade</td>
			<td>BDH</td>
			<td>VWR BDH3092-500MLP</td>
			<td>to prepare sodium acetate buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Agarose Genetic Technology Grade</td>
			<td>MP Biomedicals LLC.</td>
			<td>800668</td>
			<td>to coat prepared interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Centrifuge</td>
			<td>Eppendorf AG</td>
			<td>5415D</td>
			<td>to pellet interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Chitosan, from shrimp shells</td>
			<td>Sigma-Aldrich</td>
			<td>C3646-25G</td>
			<td>to combine with interfering RNA for prepararation of interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dry Yeast</td>
			<td>Universal Food Corp</td>
			<td>NA</td>
			<td>to prepare mosquito larval food with interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">E-RNAi tool</td>
			<td>German Cancer Research Center</td>
			<td>NA</td>
			<td>for design of dsRNA; http://www.dkfz.de/signaling/e-rnai3//</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">goldfish food</td>
			<td>Wardley</td>
			<td>Goldfish FLAKE FOOD</td>
			<td>to prepare mosquito larval food with interfering RNA/nanoparticles</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Heated water bath</td>
			<td>Thermo Scientific</td>
			<td>51221048</td>
			<td>to heat the interfering RNA/nanoparticles at 55oC</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ice</td>
			<td>not applicable</td>
			<td>not applicable</td>
			<td>for thawing interfering RNA and preparation of interfering RNA/nanoparticles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ice bucket</td>
			<td>Fisher Scientific</td>
			<td>02-591-44</td>
			<td>for storage of ice used during the procedure</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">liver powder</td>
			<td>MP Biomedicals LLC.</td>
			<td>900396</td>
			<td>to feed mosquito larvae post interfering RNA/nanoparticle treatment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microwave oven</td>
			<td>A variety of vendors</td>
			<td>not applicable</td>
			<td>to prepare 2% agarose solution</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">petridish (100X15 mm)</td>
			<td>Fischer Scientific</td>
			<td>875713</td>
			<td>interfering RNA/nanoparticle feeding chamber for larvae</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">pH meter</td>
			<td>Mettler Toledo</td>
			<td>S220</td>
			<td>for preparation of buffers</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Razor blade</td>
			<td>Fischer Scientific</td>
			<td>12-640</td>
			<td>to divide the interfering RNA/nanoparticle pellet for feedings</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">siRNA</td>
			<td>Thermo Scientific/Dharmacon</td>
			<td>custom</td>
			<td>for preparation of siRNA/nanoparticles</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">Sodium Sulfate, Anhydrous (Na2SO4)</td>
			<td>BDH/distributed by VWR</td>
			<td>VWR BDH0302-500G</td>
			<td>to prepare 50mM sodium sulfate solution in which the interfering RNA will be resuspended</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Thermometer</td>
			<td>VWR</td>
			<td>61066-046</td>
			<td>to measure the water bath temperature</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tooth picks</td>
			<td>VWR</td>
			<td>470146-908</td>
			<td>for stirring during interfering RNA/nanoparticle food preparation and cutting gel pellets</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Ultralow freezer</td>
			<td>A variety of vendors</td>
			<td>not applicable</td>
			<td>for storage of interfering RNA aliquots and interfering RNA/nanoparticles at -80oC</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Vortex mixer</td>
			<td>Fischer Scientific</td>
			<td>02-216-108</td>
			<td>for preparation of chitosan/interfering RNA</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Weight paper</td>
			<td>Fischer Scientific</td>
			<td>NC9798735</td>
			<td>to divide the interfering RNA/nanoparticle pellet for feedings</td>
		</tr>
	</tbody>
</table>

chitosan/interfering rna nanoparticle mediated gene silencing in disease vector mosquito larvae

Vector mosquitoes inflict more human suffering than any other organism&#8212;and kill more than one million people each year. The mosquito genome projects facilitated research in new facets of mosquito biology, including functional genetic studies in the primary African malaria vector Anopheles gambiae and the dengue and yellow fever vector Aedes aegypti. RNA interference- (RNAi-) mediated gene silencing has been used to target genes of interest in both of these disease vector mosquito species. Here, we describe a procedure for preparation of chitosan/interfering RNA nanoparticles that are combined with food and ingested by larvae. This technically straightforward, high-throughput, and relatively inexpensive methodology, which is compatible with long double stranded RNA (dsRNA) or small interfering RNA (siRNA) molecules, has been used for the successful knockdown of a number of different genes in A. gambiae and A. aegypti larvae. Following larval feedings, knockdown, which is verified through qRT-PCR or in situ hybridization, can persist at least through the late pupal stage. This methodology may be applicable to a wide variety of mosquito and other insect species, including agricultural pests, as well as other non-model organisms. In addition to its utility in the research laboratory, in the future, chitosan, an inexpensive, non-toxic and biodegradable polymer, could potentially be utilized in the field.

A. gambiae: 
Chitosan/dsRNA nanoparticles are formed due to the electrostatic interaction between amino groups of chitosan and the phosphate groups of dsRNA. The efficiency of dsRNA incorporation into nanoparticles is usually above 90% as measured by depletion of dsRNA from the solution. Atomic force microscopy images show that chitosan-dsRNA particle size averages 140 nm in diameter, ranging from 100-200 nm (Figure 1).
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Watch this Scientific Journal Video about Chitosan/Interfering RNA Nanoparticle Mediated Gene Silencing in Disease Vector Mosquito Larvae at JoVE.com

Chitosan/Interfering RNA Nanoparticle Mediated Gene Silencing in Disease Vector Mosquito Larvae

Here we describe a procedure for inhibiting gene function in disease vector mosquitoes through the use of chitosan/interfering RNA nanoparticles that are ingested by larvae.

Vector mosquitoes inflict more human suffering than any other organism&#8212;and kill more than one million people each year. The mosquito genome projects ...

chitosaninterfering-rna-nanoparticle-mediated-gene-silencing-disease

Research

JoVE Journal

Biology

Virus-induced Gene Silencing (VIGS) in Nicotiana benthamiana and Tomato

RNA interference (RNAi) is a highly specific gene-silencing phenomenon triggered by dsRNA1. This silencing mechanism uses two major classes of RNA regulators: microRNAs, which are produced from non-protein coding genes and short interfering RNAs (siRNAs). Plants use RNAi to control transposons and to exert tight control over developmental processes such as flower organ formation and leaf development2,3,4. Plants also use RNAi to defend themselves against infection by viruses. Consequently, many viruses have evolved suppressors of gene silencing to allow their successful colonization of their host5.
Virus-induced gene silencing (VIGS) is a method that takes advantage of the plant RNAi-mediated antiviral defense mechanism. In plants infected with unmodified viruses the mechanism is specifically targeted against the viral genome. However, with virus vectors carrying sequences derived from host genes, the process can be additionally targeted against the corresponding host mRNAs. VIGS has been adapted for high-throughput functional genomics in plants by using the plant pathogen Agrobacterium tumefaciens to deliver, via its Ti plasmid, a recombinant virus carrying the entire or part of the gene sequence targeted for silencing. Systemic virus spread and the endogenous plant RNAi machinery take care of the rest. dsRNAs corresponding to the target gene are produced and then cleaved by the ribonuclease Dicer into siRNAs of 21 to 24 nucleotides in length. These siRNAs ultimately guide the RNA-induced silencing complex (RISC) to degrade the target transcript2.
Different vectors have been employed in VIGS and one of the most frequently used is based on tobacco rattle virus (TRV). TRV is a bipartite virus and, as such, two different A. tumefaciens strains are used for VIGS. One carries pTRV1, which encodes the replication and movement viral functions while the other, pTRV2, harbors the coat protein and the sequence used for VIGS6,7. Inoculation of Nicotiana benthamiana and tomato seedlings with a mixture of both strains results in gene silencing. Silencing of the endogenous phytoene desaturase (PDS) gene, which causes photobleaching, is used as a control for VIGS efficiency. It should be noted, however, that silencing in tomato is usually less efficient than in N. benthamiana. RNA transcript abundance of the gene of interest should always be measured to ensure that the target gene has efficiently been down-regulated. Nevertheless, heterologous gene sequences from N. benthamiana can be used to silence their respective orthologs in tomato and vice versa8.

Virus-induced Gene Silencing VIGS in Nicotiana benthamiana and Tomato

Description of a virus-induced gene silencing (VIGS) method for knock-down of gene expression in Nicotiana benthamiana and tomato.

RNA interference (RNAi) is a highly specific gene-silencing phenomenon triggered by dsRNA1. This silencing mechanism uses two major classes of RNA ...

Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms

In mammalian cells, the endoplasmic reticulum (ER) plays a key role in protein biogenesis as well as in calcium signalling1. The heterotrimeric Sec61 complex in the ER membrane provides an aqueous path for newly-synthesized polypeptides into the lumen of the ER. Recent work from various laboratories suggested that this heterotrimeric complex may also form transient Ca2+ leak channels2-8. The key observation for this notion was that release of nascent polypeptides from the ribosome and Sec61 complex by puromycin leads to transient release of Ca2+ from the ER. Furthermore, it had been observed in vitro that the ER luminal protein BiP is involved in preventing ion permeability at the level of the Sec61 complex9,10. We have established an experimental system that allows us to directly address the role of the Sec61 complex as potential Ca2+ leak channel and to characterize its putative regulatory mechanisms11-13. This system combines siRNA mediated gene silencing and live cell Ca2+ imaging13. Cells are treated with siRNAs that are directed against the coding and untranslated region (UTR), respectively, of the SEC61A1 gene or a negative control siRNA. In complementation analysis, the cells are co-transfected with an IRES-GFP vector that allows the siRNA-resistant expression of the wildtype SEC61A1 gene. Then the cells are loaded with the ratiometric Ca2+-indicator FURA-2 to monitor simultaneously changes in the cytosolic Ca2+ concentration in a number of cells via a fluorescence microscope. The continuous measurement of cytosolic Ca2+ also allows the evaluation of the impact of various agents, such as puromycin, small molecule inhibitors, and thapsigargin on Ca2+ leakage. This experimental system gives us the unique opportunities to i) evaluate the contribution of different ER membrane proteins to passive Ca2+ efflux from the ER in various cell types, ii) characterize the proteins and mechanisms that limit this passive Ca2+ efflux, and iii) study the effects of disease linked mutations in the relevant components.

Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms

The endoplasmic reticulum plays a key role in protein biogenesis and in calcium homeostasis. We have established an experimental system that allows us to address the role of Ca2+ leak channels and to characterize their putative regulatory mechanisms. This system involves siRNA mediated gene silencing and live cell Ca2+ imaging.

In mammalian cells, the endoplasmic reticulum (ER) plays a key role in protein biogenesis as well as in calcium signalling1. The heterotrimeric Sec61 ...

Agrobacterium-Mediated Virus-Induced Gene Silencing Assay In Cotton

Cotton (Gossypium hirsutum) is one of the most important crops worldwide. Considerable efforts have been made on molecular breeding of new varieties. The large-scale gene functional analysis in cotton has been lagged behind most of the modern plant species, likely due to its large size of genome, gene duplication and polyploidy, long growth cycle and recalcitrance to genetic transformation1. To facilitate high throughput functional genetic/genomic study in cotton, we attempt to develop rapid and efficient transient assays to assess cotton gene functions.
Virus-Induced Gene Silencing (VIGS) is a powerful technique that was developed based on the host Post-Transcriptional Gene Silencing (PTGS) to repress viral proliferation2,3. Agrobacterium-mediated VIGS has been successfully applied in a wide range of dicots species such as Solanaceae, Arabidopsis and legume species, and monocots species including barley, wheat and maize, for various functional genomic studies3,4. As this rapid and efficient approach avoids plant transformation and overcomes functional redundancy, it is particularly attractive and suitable for functional genomic study in crop species like cotton not amenable for transformation.
In this study, we report the detailed protocol of Agrobacterium-mediated VIGS system in cotton. Among the several viral VIGS vectors, the tobacco rattle virus (TRV) invades a wide range of hosts and is able to spread vigorously throughout the entire plant yet produce mild symptoms on the hosts5. To monitor the silencing efficiency, GrCLA1, a homolog gene of Arabidopsis Cloroplastos alterados 1 gene (AtCLA1) in cotton, has been cloned and inserted into the VIGS binary vector pYL156. CLA1 gene is involved in chloroplast development6, and previous studies have shown that loss-of-function of AtCLA1 resulted in an albino phenotype on true leaves7, providing an excellent visual marker for silencing efficiency. At approximately two weeks post Agrobacterium infiltration, the albino phenotype started to appear on the true leaves, with 100% silencing efficiency in all replicated experiments. The silencing of endogenous gene expression was also confirmed by RT-PCR analysis. Significantly, silencing could potently occur in all the cultivars we tested, including various commercially grown varieties in Texas. This rapid and efficient Agrobacterium-mediated VIGS assay provides a very powerful tool for rapid large-scale analysis of gene functions at genome-wide level in cotton.

We present the detailed protocol for Agrobacterium-mediated virus-induced gene silencing (VIGS) assay in cotton. The tobacco rattle virus (TRV)-derived VIGS vectors were deployed to induce RNA silencing of cotton GrCLA1, Cloroplastos alterados 1 gene. The albino phenotype caused by silencing GrCLA1 was observed at the seedling stage within 2 weeks after inoculation.

Cotton (Gossypium hirsutum) is one of the most important crops worldwide. Considerable efforts have been made on molecular breeding of new varieties.  The ...

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...

Using SecM Arrest Sequence as a Tool to Isolate Ribosome Bound Polypeptides

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway that polypeptide chain follows during co-translational folding to achieve its functional form is still an enigma. In order to understand this process and to determine the exact conformation of the co-translational folding intermediates, it is essential to develop techniques that allow the isolation of RNCs carrying nascent chains of predetermined sizes to allow their further structural analysis.
SecM (secretion monitor) is a 170 amino acid E. coli protein that regulates expression of the downstream SecA (secretion driving) ATPase in the secM-secA operon6. Nakatogawa and Ito originally found that a 17 amino acid long sequence (150-FSTPVWISQAQGIRAGP-166) in the C-terminal region of the SecM protein is sufficient and necessary to cause stalling of SecM elongation at Gly165, thereby producing peptidyl-glycyl-tRNA stably bound to the ribosomal P-site7-9. More importantly, it was found that this 17 amino acid long sequence can be fused to the C-terminus of virtually any full-length and/or truncated protein thus allowing the production of RNCs carrying nascent chains of predetermined sizes7. Thus, when fused or inserted into the target protein, SecM stalling sequence produces arrest of the polypeptide chain elongation and generates stable RNCs both in vivo in E. coli cells and in vitro in a cell-free system. Sucrose gradient centrifugation is further utilized to isolate RNCs.
The isolated RNCs can be used to analyze structural and functional features of the co-translational folding intermediates. Recently, this technique has been successfully used to gain insights into the structure of several ribosome bound nascent chains10,11. Here we describe the isolation of bovine Gamma-B Crystallin RNCs fused to SecM and generated in an in vitro translation system.

We describe here a technique that is now routinely used to isolate stably bound ribosome nascent chain complexes (RNCs). This technique takes advantage of the discovery that a 17 amino acid long SecM "arrest sequence" can halt translation elongation in a prokaryotic (E. coli) system, when inserted into (or fused to the C-terminus) of virtually any protein.

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway ...

Depletion of Ribosomal RNA for Mosquito Gut Metagenomic RNA-seq

The mosquito gut accommodates dynamic microbial communities across different stages of the insect's life cycle. Characterization of the genetic capacity and functionality of the gut community will provide insight into the effects of gut microbiota on mosquito life traits. Metagenomic RNA-Seq has become an important tool to analyze transcriptomes from various microbes present in a microbial community. Messenger RNA usually comprises only 1-3% of total RNA, while rRNA constitutes approximately 90%. It is challenging to enrich messenger RNA from a metagenomic microbial RNA sample because most prokaryotic mRNA species lack stable poly(A) tails. This prevents oligo d(T) mediated mRNA isolation. Here, we describe a protocol that employs sample derived rRNA capture probes to remove rRNA from a metagenomic total RNA sample. To begin, both mosquito and microbial small and large subunit rRNA fragments are amplified from a metagenomic community DNA sample. Then, the community specific biotinylated antisense ribosomal RNA probes are synthesized in vitro using T7 RNA polymerase. The biotinylated rRNA probes are hybridized to the total RNA. The hybrids are captured by streptavidin-coated beads and removed from the total RNA. This subtraction-based protocol efficiently removes both mosquito and microbial rRNA from the total RNA sample. The mRNA enriched sample is further processed for RNA amplification and RNA-Seq.

A ribosomal RNA (rRNA) depletion protocol was developed to enrich messenger RNA (mRNA) for RNA-seq of the mosquito gut metatranscriptome. Sample specific rRNA probes, which were used to remove rRNA via subtraction, were created from the mosquito and its gut microbes. Performance of the protocol can result in the removal of approximately 90-99% of rRNA.

The mosquito gut accommodates dynamic microbial communities across different stages of the insect's life cycle. Characterization of the genetic capacity ...

Analysis of Global RNA Synthesis at the Single Cell Level following Hypoxia

Hypoxia or lowering of the oxygen availability is involved in many physiological and pathological processes. At the molecular level, cells initiate a particular transcriptional program in order to mount an appropriate and coordinated cellular response. The cell possesses several oxygen sensor enzymes that require molecular oxygen as cofactor for their activity. These range from prolyl-hydroxylases to histone demethylases. The majority of studies analyzing cellular responses to hypoxia are based on cellular populations and average studies, and as such single cell analysis of hypoxic cells are seldom performed. Here we describe a method of analysis of global RNA synthesis at the single cell level in hypoxia by using Click-iT RNA imaging kits in an oxygen controlled workstation, followed by microscopy analysis and quantification.&nbsp; Using cancer cells exposed to hypoxia for different lengths of time, RNA is labeled and measured in each cell. This analysis allows the visualization of temporal and cell-to-cell changes in global RNA synthesis following hypoxic stress.

We describe a technique for analysis of global RNA synthesis in hypoxia using imaging. Click-chemistry labeling of RNA has not previously been performed under hypoxia and allows visualization of global RNA changes at the single cell level. This approach complements the existing averaged RNA techniques, allowing direct visualization of cell-to-cell changes in global RNA synthesis.

Hypoxia or lowering of the oxygen availability is involved in many physiological and pathological processes. At the molecular level, cells initiate a ...

An Experimental and Bioinformatics Protocol for RNA-seq Analyses of Photoperiodic Diapause in the Asian Tiger Mosquito, Aedes albopictus

Photoperiodic diapause is an important adaptation that allows individuals to escape harsh seasonal environments via a series of physiological changes, most notably developmental arrest and reduced metabolism. Global gene expression profiling via RNA-Seq can provide important insights into the transcriptional mechanisms of photoperiodic diapause. The Asian tiger mosquito, Aedes albopictus, is an outstanding organism for studying the transcriptional bases of diapause due to its ease of rearing, easily induced diapause, and the genomic resources available. This manuscript presents a general experimental workflow for identifying diapause-induced transcriptional differences in A. albopictus. Rearing techniques, conditions necessary to induce diapause and non-diapause development, methods to estimate percent diapause in a population, and RNA extraction and integrity assessment for mosquitoes are documented. A workflow to process RNA-Seq data from Illumina sequencers culminates in a list of differentially expressed genes. The representative results demonstrate that this protocol can be used to effectively identify genes differentially regulated at the transcriptional level in A. albopictus due to photoperiodic differences. With modest adjustments, this workflow can be readily adapted to study the transcriptional bases of diapause or other important life history traits in other mosquitoes.

An Experimental and Bioinformatics Protocol for RNA-seq Analyses of Photoperiodic Diapause in the Asian Tiger Mosquito, Aedes albopictus

RNA-Seq analyses are becoming increasingly important for identifying the molecular underpinnings of adaptive traits in non-model organisms. Here, a protocol to identify differentially expressed genes between diapause and non-diapause Aedes albopictus mosquitoes is described, from mosquito rearing, to RNA sequencing and bioinformatics analyses of RNA-Seq data.

Photoperiodic diapause is an important adaptation that allows individuals to escape harsh seasonal environments via a series of physiological changes, ...

Meiotic Spindle Assessment in Mouse Oocytes by siRNA-mediated Silencing

Errors in chromosome segregation during meiotic division in gametes can lead to aneuploidy that is subsequently transmitted to the embryo upon fertilization. The resulting aneuploidy in developing embryos is recognized as a major cause of pregnancy loss and congenital birth defects such as Down&#8217;s syndrome. Accurate chromosome segregation is critically dependent on the formation of the microtubule spindle apparatus, yet this process remains poorly understood in mammalian oocytes. Intriguingly, meiotic spindle assembly differs from mitosis and is regulated, at least in part, by unique microtubule organizing centers (MTOCs). Assessment of MTOC-associated proteins can provide valuable insight into the regulatory mechanisms that govern meiotic spindle formation and organization. Here, we describe methods to isolate mouse oocytes and deplete MTOC-associated proteins using a siRNA-mediated approach to test function. In addition, we describe oocyte fixation and immunofluorescence analysis conditions to evaluate meiotic spindle formation and organization.

Here, we present a protocol for specific siRNA-mediated mRNA depletion followed by immunofluorescence analysis to evaluate meiotic spindle assembly and organization in mouse oocytes. This protocol is suitable for in vitro depletion of transcripts and functional assessment of different spindle and/or MTOC-associated factors in oocytes.

Errors in chromosome segregation during meiotic division in gametes can lead to aneuploidy that is subsequently transmitted to the embryo upon ...

Dissection and Lipid Droplet Staining of Oenocytes in Drosophila Larvae

Lipids are essential for animal development and physiological homeostasis. Dysregulation of lipid metabolism results in various developmental defects and diseases, such as obesity and fatty liver. Usually, lipids are stored in lipid droplets, which are the multifunctional lipid storage organelles in cells. Lipid droplets vary in size and number in different tissues and under different conditions. It has been reported that lipid droplets are tightly controlled through regulation of its biogenesis and degradation. In Drosophila melanogaster, the oenocyte is an important tissue for lipid metabolism and has been recently identified as a human liver analogue regarding lipid mobilization in response to stress. However, the mechanisms underlying the regulation of lipid droplet metabolism in oenocytes remain elusive. To solve this problem, it is of utmost importance to develop a reliable and sensitive method to directly visualize lipid droplet dynamic changes in oenocytes during development and under stressful conditions. Taking advantage of the lipophilic BODIPY 493/503, a lipid droplet-specific fluorescent dye, described here is a detailed protocol for the dissection and subsequent lipid droplet staining in the oenocytes of Drosophila larvae in response to starvation. This allows for qualitative analysis of lipid droplet dynamics under various conditions by confocal microscopy. Furthermore, this rapid and highly reproducible method can also be used in genetic screens for indentifying novel genetic factors involving lipid droplet metabolism in oenocytes and other tissues.

Dissection and Lipid Droplet Staining of Oenocytes in Drosophila Larvae

Presented here are detailed methods for the dissection and lipid droplet staining of oenocytes in Drosophila larvae using BODIPY 493/503, a lipid droplet-specific fluorescent dye.

Lipids are essential for animal development and physiological homeostasis. Dysregulation of lipid metabolism results in various developmental defects and ...