This work was supported by grants from the National Natural Science Foundation of China (31772124 and 31972239) and Fujian Agriculture and Forestry University (Grant KSYLX014).

The non-viruliferous adult leafhoppers were propagated in the Vector-borne Virus Research Center in Fujian Agriculture and Forestry University, China.
1. Nonviruliferous insect rearing
<ol>
	<li>Rear the adults on rice seedlings in a cube cage that is 40 cm x 35 cm x 20 cm (length x width x height). Keep one side of the cage covered with an insect-proof net for ventilation.
	<ol>
		<li>Keep the cages with leafhoppers in an incubator that contains an in-built humidity controller at 26 &#176;C with a relative humidity of 60-75% under a photoperiod of 16 h light and 8 h dark.</li>
	</ol>
	</li>
	<li>Use an aspirator to gently transfer all the adults from their cage into a new cage that contains fresh rice seedlings each week.
	<ol>
		<li>Let more than 200 adults mate and lay eggs in the rice.</li>
		<li>Retain the old rice seedlings for the nymphs to emerge. Rear these new nonviruliferous nymphs to the 2-instar stage.</li>
	</ol>
	</li>
</ol>
2. Virus acquisition and the collection of viruliferous insects
<ol>
	<li>Carefully transfer the 2-instar nonviruliferous nymphs to a glass culture tube (2.5 cm in diameter by 15 cm high) for 1-2 h for starvation using the aspirator.
	<ol>
		<li>Release the nymphs to a cage that contains an RDV-infected rice plant grown in a pot.</li>
		<li>Allow the nymphs to feed on the infected rice plant for 2 days. 
		NOTE: Carefully water the rice plant and avoid washing away the nymphs. The 2-instar nymphs are approximately 1.6-2 mm long.</li>
	</ol>
	</li>
	<li>Carefully transfer these nymphs to a new cage that contains fresh virus-free rice seedlings with a relative humidity of 60-75% under a photoperiod of 16 h light and 8 h dark. Allow the nymphs to feed on the infected rice plant for 12 days to complete the circulative transmission period of RDV.</li>
</ol>
3. Collection of salivary proteins using a feeding cage
<ol>
	<li>Prepare five small pipe-like feeding cages (2.5 cm in diameter by 4 cm high) in which one end is covered with insect-proof netting.</li>
	<li>Confine 15-20 leafhoppers in each feeding cage, and then cover the other end of the cage with a thin foam mat.
	<ol>
		<li>Fix one rice seedling (5-6 cm high) between the end of cage and a foam mat with tapes. Ensure that the leafhoppers in the feeding cage can feed on the rice seedlings exposed to the interior of the cage.</li>
	</ol>
	</li>
	<li>Immerse the seedling roots in water so that the rice plant will remain alive. Allow the leafhoppers to feed on them for 2 days.</li>
	<li>Remove the leafhoppers from their feeding cages and collect the rice seedlings on which they fed. Cut the parts of seedlings outside of the cage and recover the feeding regions of seedlings. 
	&#8203;NOTE: This sample can be stored at -80 &#176;C for 3 months at the most, if it is not instantly used for detection.</li>
</ol>
4. Reagent preparation
<ol>
	<li>Dissolve 15.1 g of Tris-base, 94 g of glycine, and 5 g of SDS in 1 L of sterile water to prepare 5xTris-glycine buffer. Dilute 200 mL of 5xTris-glycine buffer with 800 mL of sterile water to prepare 1xTris-glycine buffer (see Table 1 for buffer composition).</li>
	<li>Dissolve 80 g of NaCl, 30 g of Tris-base, and 2 g of KCl in 1 L of sterile water to prepare 10xTris-buffered saline (TBS) buffer. Autoclave the solution at 121 &#176;C for 15 min.</li>
	<li>Dissolve 8 g of SDS, 4 mL of &#223;-mercaptoethanol, 0.02 g of bromophenol blue, and 40 mL of glycerol in 40 mL of 0.1 M Tris-HCl (pH 6.8) to prepare 4x protein sample buffer.</li>
	<li>Mix 800 mL Tris-glycine buffer with 200 mL methanol to prepare the transfer buffer.</li>
	<li>Add 100 mL 10xTBS solution and 3 mL Tween 20 to 900 mL sterile water to prepare the TBS buffer with Tween 20 (TBST) solution.</li>
</ol>
5. Western blotting to detect the saliva and viral proteins
<ol>
	<li>Grind 0.1 g of the rice samples with liquid nitrogen until the tissue becomes a powder. Add 200 &#181;L of 4x protein sample buffer to the sample and boil it for 10 min. Centrifuge the samples at 12,000 x g for 10 min at room temperature.
	<ol>
		<li>Remove the supernatant and place it in a new vial. Load 10 &#181;L of the sample into an SDS-PAGE gel, and run it in Tris-glycine buffer at 150 V for 45-60 min. 
		NOTE: The residue after centrifugation can be discarded.</li>
	</ol>
	</li>
	<li>Put a 0.45 &#181;m nitrocellulose membrane and other sandwich supplies in the Transfer buffer for 30 min. 
	NOTE: This step can be done before the gel has completed its run.</li>
	<li>Sandwich the gel and transfer it for 90-120 min at 100 V in the Transfer buffer.</li>
	<li>Take the membrane and place it in 7% non-fat dry milk blocking solution in TBST solution for 20 min. Add the specific antibody against RDV P8 or Vg to a 7% solution of non-fat dry milk in TBST. Incubate with the antibody for staining the membrane for 2 h or overnight.</li>
	<li>Wash the membrane with TBST solution three times, with 5 min washing each time.</li>
	<li>Add the goat anti-rabbit IgG as a secondary antibody to 7% non-fat dry milk with TBST. Incubate with the antibody for 60-90 min at room temperature.</li>
	<li>Wash the membrane with TBST solution three times for 5 min each time.</li>
	<li>Use the ECL Western kit for the chemiluminescent method. Mix Detection Reagents 1 and 2 in the kit at a ratio of 1:1 in a tube. Put the mixed reagent onto the membrane and incubate the blot for 5 min.</li>
	<li>Drain the excess reagent and take a colorimetric picture of the chemiluminescent picture. Combine them to see the ladder with protein bands.</li>
</ol>

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The authors have nothing to disclose.

The saliva directly secreted by the salivary glands of the piercing-sucking insects plays a pivotal role because it predigests and detoxifies the host tissues and vectors&#39; cross-kingdom biological factors into the hosts1,3,4. The cross-kingdom biological factors, including elicitors, effectors, and small RNA, are critical for insect-host communication14,15,</sup...

The vector-host transmission mode of arboviruses, a fundamental problem, is at the frontier of biological science. Many plant viruses of agricultural importance are horizontally transmitted by insect vectors1. More than one-half of plant viruses are vectored by hemipteran insects, including aphids, whiteflies, leafhoppers, planthoppers, and thrips. These insects have distinct features that enable them to efficiently transmit plant viruses1. They possess piercing-sucking mouthparts and feed on the sap from phloem and xylem, and secrete their saliva1,2,3,4. With the development and improvement of techniques, the identification and functional analyses of salivary components are becoming a new focus of intensive research. The known salivary proteins in saliva include numerous enzymes, such as pectinesterase, cellulase, peroxidase, alkaline phosphatase, polyphenol oxidase, and sucrase, among others5,6,7,8,9,10,11,12,13. The proteins in saliva also include elicitors that trigger the host defense response, thereby altering the performance of insects, and effectors that suppress the host defense, which enhances insect fitness and components that induce host pathological responses14,15,16,17. Therefore, saliva proteins are vital materials for communication between insects and hosts. During the transmission of viruses, the saliva secreted by the salivary glands of piercing-sucking viruliferous insects also contains viral proteins. Viral components utilize the flow of saliva to release them from the insect to the plant host. Therefore, the insect saliva bridges the virus-vector-host tritrophic interaction. Investigating the biological function of saliva proteins secreted by viruliferous insects helps to understand the relationship of virus-vector-host.
For animal viruses, it is reported that the saliva of mosquitoes mediates the transmission and pathogenicity of West Nile virus (WNV) and Dengue virus (DENV). The saliva protein AaSG34 promotes dengue-2 virus replication and transmission, while the saliva protein AaVA-1 promotes DENV and Zika virus (ZIKV) transmission by activating autophagy18,19. The saliva protein D7 of mosquitoes can inhibit DENV infection in vitro and in vivo via direct interaction with the DENV virions and recombinant DENV envelope protein20. In plant viruses, the begomovirus tomato yellow leaf curl virus (TYLCV) induces the whitefly salivary protein Bsp9, which suppresses the WRKY33-mediated immunity of plant host, to increase the preference and performance of whiteflies, eventually increasing the transmission of viruses21. Because studies of the role that insect salivary proteins play in plant hosts have lagged behind those of animal hosts, a stable and reliable system to detect the salivary proteins in plant hosts is urgently required.
The plant virus known as rice dwarf virus (RDV) is transmitted by the leafhopper Nephotettix cincticeps (Hemiptera: Cicadellidae) with high efficiency and in a persistently propagative manner22,23. RDV was first reported to be transmitted by an insect vector and causes a severe disease of rice in Asia24,25. The virion is icosahedral and double-layered spherical, and the outer layer contains the P8 outer capsid protein22. The circulative transmission period of RDV in N. cincticeps is 14 days26,27,28,29,30. When the RDV arrives at salivary glands, virions are released into saliva-stored cavities in the salivary glands via an exocytosis-like mechanism23. The vitellogenin (Vg) is the yolk protein precursor essential for oocyte development in female insects31,32,33. Most insect species have at least one Vg transcript of 6-7 kb, which encodes a precursor protein of approximately 220 kDa. The protein precursors of Vg can usually be cleaved into large (140 to 190 kDa) and small (&#60;50 kDa) fragments before entering the ovary18,19. Previous proteomic analysis revealed the presence of the peptides derived from Vg in the secreted saliva of the leafhopper Recilia dorsalis, although their function is unknown (unpublished data). It is newly reported that Vg, which is orally secreted from planthoppers, functions as an effector to damage the defenses of plants34. It is unknown whether the Vg of N. cincticeps could also be released to the plant host with salivary flow, and then could play a role in the plant to interfere with plant defenses. To address whether N. cincticeps exploits salivary proteins, such as Vg, to inhibit or activate plant defenses, the first step is identifying proteins released to the plant during feeding. Understanding the method to identify the salivary proteins present in the plant is potentially essential to explain the function of saliva proteins and the interactions between Hemiptera and plants.
In the protocol presented here, N. cincticeps is used as an example to provide a method to examine the presence of salivary proteins in the plant host introduced through insect feeding. The protocol primarily details the collection and detection of salivary proteins and is helpful for further investigation on most hemipterans.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tris base</td>
			<td>Roche</td>
			<td>D609K69032</td>
			<td>For 5&#215;Tris-glycine buffer and 10&#215;TBS buffer preparation</td>
		</tr>
		<tr>
			<td>glycine</td>
			<td>Sigma-Aldrich</td>
			<td>WXBD0677V</td>
			<td>For 5&#215;Tris-glycine buffer preparation</td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>Sigma-Aldrich</td>
			<td>SLCB4394</td>
			<td>For 5&#215;Tris-glycine buffer preparation</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10019318</td>
			<td>For 10&#215;TBS buffer preparation</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10016318</td>
			<td>For 10&#215;TBS buffer preparation</td>
		</tr>
		<tr>
			<td>&#223;-mercaptoethanol</td>
			<td>Xiya Reagent</td>
			<td>B14492</td>
			<td>For 4&#215; protein sample buffer preparation</td>
		</tr>
		<tr>
			<td>bromophenol blue</td>
			<td>Sigma-Aldrich</td>
			<td>SHBL3668</td>
			<td>For 4&#215; protein sample buffer preparation</td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10010618</td>
			<td>For 4&#215; protein sample buffer preparation</td>
		</tr>
		<tr>
			<td>methanol</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10014118</td>
			<td>For transfer buffer preparation</td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>Coolaber SCIENCE&#38;TeCHNoLoGY</td>
			<td>CT30111220</td>
			<td>For TBST preparation</td>
		</tr>
		<tr>
			<td>non-fat dry milk</td>
			<td>Becton.Dickinso and company</td>
			<td>252038</td>
			<td>For membrane blocking, antibodies dilution</td>
		</tr>
		<tr>
			<td>goat anti-rabbit IgG</td>
			<td>Sangon Biotech</td>
			<td>D110058-0001</td>
			<td>Recognization of the primary andtibody</td>
		</tr>
		<tr>
			<td>ECL Western kit</td>
			<td>ThermoFisher Scientific</td>
			<td>32209</td>
			<td>Chemiluminescent substrate</td>
		</tr>
		<tr>
			<td>nitrocellulose membrane</td>
			<td>Pall Corporation</td>
			<td>25312915</td>
			<td>For proteins transfer</td>
		</tr>
		<tr>
			<td>Buffers and Solutions</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Buffer</td>
			<td>Composition</td>
			<td></td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>&#160;5&#215;Tris-glycine buffer</td>
			<td>15.1 g Tris base 
			94 g glycine 
			&#160;5 g SDS in 1 L sterile water</td>
			<td></td>
			<td>&#160;Stock solution</td>
		</tr>
		<tr>
			<td>1&#215;Tris-glycine buffer</td>
			<td>200 mL of 5&#215;Tris-glycine buffer 
			800 mL sterile water</td>
			<td></td>
			<td>Work solution, for SDS-PAGE</td>
		</tr>
		<tr>
			<td>10&#215;Tris-buffered saline (TBS) buffer</td>
			<td>80 g NaCl 
			30 g Tris base 
			2 g KCl 
			in 1 L sterile water</td>
			<td></td>
			<td>Stock solution</td>
		</tr>
		<tr>
			<td>TBS with Tween 20 (TBST) solution</td>
			<td>100 mL 10&#215;TBS solution 
			3 mL Tween 20 
			900 mL sterile water</td>
			<td></td>
			<td>Work solution</td>
		</tr>
		<tr>
			<td>4&#215; protein sample buffer</td>
			<td>8 g SDS 
			4 mL &#223;-mercaptoethanol 
			0.02 g bromophenol blue 
			40 mL glycerol 
			in 40 mL 0.1 M Tris-HCl (pH 6.8)</td>
			<td></td>
			<td>For protein extraction</td>
		</tr>
		<tr>
			<td>Transfer buffer</td>
			<td>800 mL Tris-glycine buffer 
			200 mL methanol</td>
			<td></td>
			<td>For protein transfer</td>
		</tr>
		<tr>
			<td>Instruments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Sigma-Aldrich</td>
			<td>SHBL3668</td>
			<td>For 4x protein sample buffer preparation</td>
		</tr>
		<tr>
			<td>Constant temperature incubator</td>
			<td>Ningbo Saifu Experimental Instrument Co., Ltd.</td>
			<td>PRX-1200B</td>
			<td>For rearing leafhoppers</td>
		</tr>
		<tr>
			<td>Electrophoresis</td>
			<td>Tanon Science &#38; Technology Co.,Ltd.</td>
			<td>Tanon EP300</td>
			<td>For SDS-PAGE</td>
		</tr>
		<tr>
			<td>Electrophoretic transfer core module</td>
			<td>BIO-RAD</td>
			<td>1703935</td>
			<td>For SDS-PAGE</td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10010618</td>
			<td>For 4x protein sample buffer preparation</td>
		</tr>
		<tr>
			<td>glycine</td>
			<td>Sigma-Aldrich</td>
			<td>WXBD0677V</td>
			<td>For 5x Tris-glycine buffer preparation</td>
		</tr>
		<tr>
			<td>goat anti-rabbit IgG</td>
			<td>Sangon Biotech</td>
			<td>D110058-0001</td>
			<td>Recognization of the primary andtibody</td>
		</tr>
		<tr>
			<td>High-pass tissue grinding instrument</td>
			<td>Shanghai Jingxin Industrial Development Co., Ltd.</td>
			<td>JXFSIPRP-24</td>
			<td>For grinding plant tissues</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10016318</td>
			<td>For 10x TBS buffer preparation</td>
		</tr>
		<tr>
			<td>methanol</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10014118</td>
			<td>For transfer buffer preparation</td>
		</tr>
		<tr>
			<td>Mini wet heat transfer trough</td>
			<td>BIO-RAD</td>
			<td>1703930</td>
			<td>For SDS-PAGE</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sinopharm Chemical Reagent Co., Ltd</td>
			<td>10019318</td>
			<td>For 10x TBS buffer preparation</td>
		</tr>
		<tr>
			<td>nitrocellulose membrane</td>
			<td>Pall Corporation</td>
			<td>25312915</td>
			<td>For proteins transfer</td>
		</tr>
		<tr>
			<td>non-fat dry milk</td>
			<td>Becton.Dickinso and company</td>
			<td>252038</td>
			<td>For membrane blocking, antibodies dilution</td>
		</tr>
		<tr>
			<td>Pierce ECL Western kit</td>
			<td>ThermoFisher Scientific</td>
			<td>32209</td>
			<td>Chemiluminescent substrate</td>
		</tr>
		<tr>
			<td>Protein color instrument</td>
			<td>GE Healthcare bio-sciences AB</td>
			<td>Amersham lmager 600</td>
			<td>For detecting proteins</td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>Sigma-Aldrich</td>
			<td>SLCB4394</td>
			<td>For 5x Tris-glycine buffer preparation</td>
		</tr>
		<tr>
			<td>Tris base</td>
			<td>Roche</td>
			<td>D609K69032</td>
			<td>For 5x Tris-glycine buffer and 10&#215;TBS buffer preparation</td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>Coolaber SCIENCE&#38;TeCHNoLoGY</td>
			<td>CT30111220</td>
			<td>For TBST preparation</td>
		</tr>
		<tr>
			<td>Vertical plate electrophoresis tank</td>
			<td>BIO-RAD</td>
			<td>1658001</td>
			<td>For SDS-PAGE</td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>Shanghai Jinghong Experimental equipment Co., Ltd.</td>
			<td>XMTD-8222</td>
			<td>For boil the protein samples</td>
		</tr>
		<tr>
			<td>&#946;-mercaptoethanol</td>
			<td>Xiya Reagent</td>
			<td>B14492</td>
			<td>For 4x protein sample buffer preparation</td>
		</tr>
	</tbody>
</table>

detecting virus and salivary proteins of a leafhopper vector in the plant host

Insect vectors horizontally transmit many plant viruses of agricultural importance. More than one-half of plant viruses are transmitted by hemipteran insects that have piercing-sucking mouthparts. During viral transmission, the insect saliva bridges the virus-vector-host because the saliva vectors viruses, and the insect proteins, trigger or suppress the immune response of plants from insects into plant hosts. The identification and functional analyses of salivary proteins are becoming a new area of focus in the research field of arbovirus-host interactions. This protocol provides a system to detect proteins in the saliva of leafhoppers using the plant host. The leafhopper vector Nephotettix cincticeps infected with rice dwarf virus (RDV) serves as an example. The vitellogenin and major outer capsid protein P8 of RDV vectored by the saliva of N. cincticeps can be detected simultaneously in the rice plant that N. cincticeps feeds on. This method is applicable for testing the salivary proteins that are transiently retained in the plant host after insect feeding. It is believed that this system of detection will benefit the study of hemipteran-virus-plant or hemipteran-plant interactions.

Figure 1&#160;illustrates all of the steps in this protocol: insect rearing, virus acquisition, the collection of salivary proteins via rice feeding, and the western blot. The western blots results showed that specific and expected bands of approximately 220 kDa were observed in the samples of feeding rice and salivary glands of insects on the membrane incubated with antibodies against Vg. In contrast, no band was observed in the non-feeding rice sample. The result in </stro...

Watch this Scientific Journal Video about Detecting Virus and Salivary Proteins of a Leafhopper Vector in the Plant Host at JoVE.com

Detecting Virus and Salivary Proteins of a Leafhopper Vector in the Plant Host

This protocol demonstrates how to use the plant host to detect salivary proteins of leafhopper and plant viral proteins released by leafhopper vectors.

Insect vectors horizontally transmit many plant viruses of agricultural importance. More than one-half of plant viruses are transmitted by hemipteran ...

detecting-virus-salivary-proteins-leafhopper-vector-plant

Research

JoVE Journal

Biology

1.5K Views.  Fujian Agriculture and Forestry University. This protocol demonstrates how to use the plant host to detect salivary proteins of leafhopper and plant viral proteins released by leafhopper vectors.

Video: Detecting Virus and Salivary Proteins of a Leafhopper Vector in the Plant Host

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 ...

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 ...

Electroantennographic Bioassay as a Screening Tool for Host Plant Volatiles

Plant volatiles play an important role in plant-insect interactions. Herbivorous insects use plant volatiles, known as kairomones, to locate their host plant.1,2 When a host plant is an important agronomic commodity feeding damage by insect pests can inflict serious economic losses to growers. Accordingly, kairomones can be used as attractants to lure or confuse these insects and, thus, offer an environmentally friendly alternative to pesticides for insect control.3 Unfortunately, plants can emit a vast number volatiles with varying compositions and ratios of emissions dependent upon the phenology of the commodity or the time of day. This makes identification of biologically active components or blends of volatile components an arduous process. To help identify the bioactive components of host plant volatile emissions we employ the laboratory-based screening bioassay electroantennography (EAG). EAG is an effective tool to evaluate and record electrophysiologically the olfactory responses of an insect via their antennal receptors. The EAG screening process can help reduce the number of volatiles tested to identify promising bioactive components. However, EAG bioassays only provide information about activation of receptors. It does not provide information about the type of insect behavior the compound elicits; which could be as an attractant, repellent or other type of behavioral response. Volatiles eliciting a significant response by EAG, relative to an appropriate positive control, are typically taken on to further testing of behavioral responses of the insect pest. The experimental design presented will detail the methodology employed to screen almond-based host plant volatiles4,5 by measurement of the electrophysiological antennal responses of an adult insect pest navel orangeworm (Amyelois transitella) to single components and simple blends of components via EAG bioassay. The method utilizes two excised antennae placed across a "fork" electrode holder. The protocol demonstrated here presents a rapid, high-throughput standardized method for screening volatiles. Each volatile is at a set, constant amount as to standardize the stimulus level and thus allow antennal responses to be indicative of the relative chemoreceptivity. The negative control helps eliminate the electrophysiological response to both residual solvent and mechanical force of the puff. The positive control (in this instance acetophenone) is a single compound that has elicited a consistent response from male and female navel orangeworm (NOW) moth. An additional semiochemical standard that provides consistent response and is used for bioassay studies with the male NOW moth is (Z,Z)-11,13-hexdecadienal, an aldehyde component from the female-produced sex pheromone.6-8

A method to rapidly screen host plant volatiles by measurement of the electrophysiological response of adult navel orangeworm (Amyelois transitella) antennae to single components and blends via electroantennographic analysis is demonstrated.

Plant volatiles play an important role in plant-insect interactions. Herbivorous insects use plant volatiles, known as kairomones, to locate their host ...

Glycan Profiling of Plant Cell Wall Polymers using Microarrays

Plant cell walls are complex matrixes of heterogeneous glycans which play an important role in the physiology and development of plants and provide the raw materials for human societies (e.g. wood, paper, textile and biofuel industries)1,2. However, understanding the biosynthesis and function of these components remains challenging.
Cell wall glycans are chemically and conformationally diverse due to the complexity of their building blocks, the glycosyl residues. These form linkages at multiple positions and differ in ring structure, isomeric or anomeric configuration, and in addition, are substituted with an array of non-sugar residues. Glycan composition varies in different cell and/or tissue types or even sub-domains of a single cell wall3. Furthermore, their composition is also modified during development1, or in response to environmental cues4.
In excess of 2,000 genes have Plant cell walls are complex matrixes of heterogeneous glycans been predicted to be involved in cell wall glycan biosynthesis and modification in Arabidopsis5. However, relatively few of the biosynthetic genes have been functionally characterized 4,5. Reverse genetics approaches are difficult because the genes are often differentially expressed, often at low levels, between cell types6. Also, mutant studies are often hindered by gene redundancy or compensatory mechanisms to ensure appropriate cell wall function is maintained7. Thus novel approaches are needed to rapidly characterise the diverse range of glycan structures and to facilitate functional genomics approaches to understanding cell wall biosynthesis and modification.
Monoclonal antibodies (mAbs)8,9 have emerged as an important tool for determining glycan structure and distribution in plants. These recognise distinct epitopes present within major classes of plant cell wall glycans, including pectins, xyloglucans, xylans, mannans, glucans and arabinogalactans. Recently their use has been extended to large-scale screening experiments to determine the relative abundance of glycans in a broad range of plant and tissue types simultaneously9,10,11.
Here we present a microarray-based glycan screening method called Comprehensive Microarray Polymer Profiling (CoMPP) (Figures 1 &amp; 2)10,11 that enables multiple samples (100 sec) to be screened using a miniaturised microarray platform with reduced reagent and sample volumes. The spot signals on the microarray can be formally quantified to give semi-quantitative data about glycan epitope occurrence. This approach is well suited to tracking glycan changes in complex biological systems12 and providing a global overview of cell wall composition particularly when prior knowledge of this is unavailable.

A technique called Comprehensive Microarray Polymer Profiling (CoMPP) for the characterisation of plant cell wall glycans is described. This method combines the specificity of monoclonal antibodies directed to defined glycan-epitopes with a miniature microarray analytical platform allowing screening of glycan occurrence in a broad range of biological contexts.

Plant cell walls are complex matrixes of heterogeneous glycans which play an important role in the physiology and development of plants and provide the ...

The MultiBac Protein Complex Production Platform at the EMBL

Proteomics research revealed the impressive complexity of eukaryotic proteomes in unprecedented detail. It is now a commonly accepted notion that proteins in cells mostly exist not as isolated entities but exert their biological activity in association with many other proteins, in humans ten or more, forming assembly lines in the cell for most if not all vital functions.1,2 Knowledge of the function and architecture of these multiprotein assemblies requires their provision in superior quality and sufficient quantity for detailed analysis. The paucity of many protein complexes in cells, in particular in eukaryotes, prohibits their extraction from native sources, and necessitates recombinant production. The baculovirus expression vector system (BEVS) has proven to be particularly useful for producing eukaryotic proteins, the activity of which often relies on post-translational processing that other commonly used expression systems often cannot support.3 BEVS use a recombinant baculovirus into which the gene of interest was inserted to infect insect cell cultures which in turn produce the protein of choice. MultiBac is a BEVS that has been particularly tailored for the production of eukaryotic protein complexes that contain many subunits.4 A vital prerequisite for efficient production of proteins and their complexes are robust protocols for all steps involved in an expression experiment that ideally can be implemented as standard operating procedures (SOPs) and followed also by non-specialist users with comparative ease. The MultiBac platform at the European Molecular Biology Laboratory (EMBL) uses SOPs for all steps involved in a multiprotein complex expression experiment, starting from insertion of the genes into an engineered baculoviral genome optimized for heterologous protein production properties to small-scale analysis of the protein specimens produced.5-8 The platform is installed in an open-access mode at EMBL Grenoble and has supported many scientists from academia and industry to accelerate protein complex research projects.

Protein complexes catalyze key cellular functions. Detailed functional and structural characterization of many essential complexes requires recombinant production. MultiBac is a baculovirus/insect cell system particularly tailored for expressing eukaryotic proteins and their complexes. MultiBac was implemented as an open-access platform, and standard operating procedures developed to maximize its utility.

Proteomics  research revealed the impressive complexity of eukaryotic proteomes in  unprecedented detail. It is now a commonly accepted notion that ...

High-throughput CRISPR Vector Construction and Characterization of DNA Modifications by Generation of Tomato Hairy Roots

Targeted DNA mutations generated by vectors with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology have proven useful for functional genomics studies. While most cloning strategies are simple to perform, they generally use multiple steps and can require several days to generate the ultimate constructs. The method presented here is based on DNA assembly and can produce fully functional CRISPR vectors in a single cloning reaction. Vector construction can also be pooled, further increasing the efficiency and utility of the process. A modification of the method is used to create CRISPR vectors with multiple gene targets. CRISPR vectors are then transformed into tomato hairy roots to generate transgenic materials with targeted DNA modifications. Hairy roots are a useful system for testing vector functionality as they are technically simple to generate and amenable to large-scale production. The methods presented here will have wide application as they can be used to generate a variety of CRISPR vectors and be used in a wide range of plant species.

Using DNA assembly, multiple CRISPR vectors can be constructed in parallel in a single cloning reaction, making the construction of large numbers of CRISPR vectors a simple task. Tomato hairy roots are an excellent model system to validate CRISPR vectors and generate mutant materials.

Targeted DNA mutations generated by vectors with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology have proven useful for ...

Fat Body Organ Culture System in Aedes Aegypti, a Vector of Zika Virus

The insect fat body plays a central role in insect metabolism and nutrient storage, mirroring functions of the liver and fat tissue in vertebrates. Insect fat body tissue is usually distributed throughout the insect body. However, it is often concentrated in the abdomen and attached to the abdominal body wall.
The mosquito fat body is the sole source of yolk proteins, which are critical for egg production. Therefore, the in vitro culture of mosquito fat body tissues represents an important system for the study of mosquito physiology, metabolism, and, ultimately, egg production. The fat body culture process begins with the preparation of solutions and reagents, including amino acid stock solutions, Aedes physiological saline salt stock solution (APS), calcium stock solution, and fat body culture medium. The process continues with fat body dissection, followed by an experimental treatment. After treatment, a variety of different analyses can be performed, including RNA sequencing (RNA-Seq), qPCR, Western blots, proteomics, and metabolomics.
In our example experiment, we demonstrate the protocol through the excision and culture of fat bodies from the yellow fever mosquito, Aedes aegypti, a principal vector of arboviruses including dengue, chikungunya, and Zika. RNA from fat bodies cultured under a physiological condition known to upregulate yolk proteins versus the control were subject to RNA-Seq analysis to demonstrate the potential utility of this procedure for investigations of gene expression.

Fat Body Organ Culture System in Aedes Aegypti, a Vector of Zika Virus

The fat body is the central metabolic organ in insects. We present a live organ culture system that enables the user to study the responses of isolated fat body tissue to various stimuli.

The insect fat body plays a central role in insect metabolism and nutrient storage, mirroring functions of the liver and fat tissue in vertebrates. Insect ...

Direct Agroinoculation of Maize Seedlings by Injection with Recombinant Foxtail Mosaic Virus and Sugarcane Mosaic Virus Infectious Clones

Agrobacterium-based inoculation approaches are widely used for introducing viral vectors into plant tissues. This study details a protocol for the injection of maize seedlings near meristematic tissue with Agrobacterium carrying a viral vector. Recombinant foxtail mosaic virus (FoMV) clones engineered for gene silencing and gene expression were used to optimize this method, and its use was expanded to include a recombinant sugarcane mosaic virus (SCMV) engineered for gene expression. Gene fragments or coding sequences of interest are inserted into a modified, infectious viral genome that has been cloned into the binary T-DNA plasmid vector pCAMBIA1380. The resulting plasmid constructs are transformed into Agrobacterium tumefaciens strain GV3101. Maize seedlings as young as 4 days old can be injected near the coleoptilar node with bacteria resuspended in MgSO4 solution. During infection with Agrobacterium, the T-DNA carrying the viral genome is transferred to maize cells, allowing for the transcription of the viral RNA genome. As the recombinant virus replicates and systemically spreads throughout the plant, viral symptoms and phenotypic changes resulting from the silencing of the target genes lesion mimic 22 (les22)&#160;or&#160;phytoene desaturase (pds) can be observed on the leaves, or expression of green fluorescent protein (GFP) can be detected upon illumination with UV light or fluorescence microscopy. To detect the virus and assess the integrity of the insert simultaneously, RNA is extracted from the leaves of the injected plant and RT-PCR is conducted using primers flanking the multiple cloning site (MCS) carrying the inserted sequence. This protocol has been used effectively in several maize genotypes and can readily be expanded to other viral vectors, thereby offering an accessible tool for viral vector introduction in maize.

An Agrobacterium-based injection (agroinjection) protocol is presented for the inoculation of foxtail mosaic virus&#160;and sugarcane mosaic virusclones into maize seedlings. Inoculation in this manner leads to viral infection, virus-induced gene silencing of marker genes, and viral overexpression of GFP.

Agrobacterium-based inoculation approaches are widely used for introducing viral vectors into plant tissues. This study details a protocol for the ...

Immunofluorescent Staining for Visualization of Heterochromatin Associated Proteins in Drosophila Salivary Glands

Visualization of heterochromatin aggregates by immunostaining can be challenging. Many mammalian components of chromatin are conserved in Drosophila melanogaster. Therefore, it is an excellent model to study heterochromatin formation and maintenance. Polytenized cells, such as the ones found in salivary glands of third instar D. melanogaster larvae, provide an excellent tool to observe the chromatin amplified nearly a thousand times and have allowed researchers to study changes in the distribution of heterochromatin in the nucleus. Although the observation of heterochromatin components can be carried out directly in polytene chromosome preparations, the localization of some proteins can be altered by the severity of the treatment. Therefore, the direct visualization of heterochromatin in cells complements this type of study. In this protocol, we describe the immunostaining techniques used for this tissue, the use of secondary fluorescent antibodies, and confocal microscopy to observe these heterochromatin aggregates with greater precision and detail.

Immunofluorescent Staining for Visualization of Heterochromatin Associated Proteins in Drosophila Salivary Glands

This protocol aims to visualize heterochromatin aggregates in Drosophila polytene cells.

Visualization of heterochromatin aggregates by immunostaining can be challenging. Many mammalian components of chromatin are conserved in Drosophila ...

Immunofluorescent Labeling of Plant Virus and Insect Vector Proteins in Hemipteran Guts

Most plant viruses in nature are transmitted from one plant to another by hemipteran insects. A high population density of the vector insects that are highly efficient at virus transmission plays a key role in virus epidemics in fields. Studying virus-insect vector interactions can advance our understanding of virus transmission and epidemics with the aim of designing novel strategies to control plant viruses and their vector insects. Immunofluorescence labeling has been widely used to analyze interactions between pathogens and hosts and is used here in the white-backed planthopper (WBPH, Sogatella furcifera), which efficiently transmits the southern rice black streaked dwarf virus (SRBSDV, genus Fijivirus, family Reoviridae), to locate the virions and insect proteins in the midgut epithelial cells. Using laser scanning confocal microscopy, we studied the morphological characteristics of midgut epithelial cells, cellular localization of insect proteins, and the colocalization of virions and an insect protein. This protocol can be used to study virus activities in insects, functions of insect proteins, and interactions between virus and vector insect.

This protocol for immunofluorescent labeling of both plant virus proteins and vector insect proteins in excised insect guts can be used to study interactions among virus and vector insects, insect protein functions and molecular mechanisms underlying virus transmission.

Most plant viruses in nature are transmitted from one plant to another by hemipteran insects. A high population density of the vector insects that are ...