This research was funded by the Projects of the National Natural Science Foundation of China (32172476, 32102275), the Agricultural Science and Technology Innovation Program (CAAS-ZDRW202203, CAAS-ZDRW202108), and Central Funds Guiding the Local Science and Technology Development (XZ202301YD0042C).

NOTE: See the Table of Materials for details related to all materials, instruments, software, and reagents used in this protocol.
1. Collection and maintenance of insect culture
<ol>
	<li>Adhere a group of ~5,000 eggs of Corcyra cephalonica (Stainton) onto a 9 cm by 16 cm card using a 1:5 (v/v) solution of gum arabic powder and water25,26. 
	NOTE: Avoid attaching too many host eggs to the card as overcrowding makes it impractical for subsequent transfer and dissection procedures.</li>
	<li>To prevent the hatching of host eggs, subject the host egg cards to 30 min of ultraviolet (UV) irradiation (Figure 1-i). Subsequently, cut the paper with inactivated eggs into egg cards measuring 1 cm thick and 8 cm in diameter, each containing approximately 300-500 eggs (Figure 1-ii)25,26,27.</li>
	<li>Introduce a cohort of 80-120 T. denrolimi wasps into a glass tube measuring 2 cm in diameter and 8 cm in length. Seal the tube with cotton. 
	NOTE: Maintain the wasps at a temperature of 25 &#177; 1 &#176;C, with a light/dark cycle of 16 h of light and 8 h of darkness and maintain a relative humidity of approximately 75%.</li>
	<li>Present a host egg card to the wasps for parasitization (Figure 1-ii). Permit the wasps to deposit their eggs into the host eggs for 6 h, after which promptly remove the wasps. 
	&#8203;NOTE: Avoid prolonging the parasitization period excessively as this can lead to overcrowding of T. denrolimi offspring within a host egg, resulting in increased offspring wasp mortality28,29.</li>
</ol>
2. Synthesis of dsRNA
<ol>
	<li>Design primer sets containing a T7 promoter for the synthesis of double-stranded RNA (dsRNA). Choose a 300-400 bp segment from the targeted gene (Ferhch) for dsRNA synthesis.</li>
	<li>Acquire commercially synthesized primer sets for the production of dsRNA for the targeted gene and dsGFP for use as a negative control.</li>
	<li>Extract RNA content from 100 T. denrolimi wasps using the referenced kit following the manufacturer&#39;s protocol9. Check the quality of RNA content; proceed if the value of OD260/OD280 ranges from 1.8 to 2.09.</li>
	<li>Purify the RNA content with 2 &#181;L of 5x buffer (1 U/50 &#181;L), 1 &#181;L of DNAse (1 U/50 &#181;L), and 6.5 &#181;L of RNA (~100 ng/&#181;L), 0.5 &#181;L of H2O at 42 &#176;C for 2 min.</li>
	<li>Perform reverse transcriptase polymerase chain reaction (RT-PCR) to generate a cDNA template with 10 &#181;L of purified RNA (~100 ng/&#181;L), 4 &#181;L of 5x buffer (1 U/50 &#181;L), 1 &#181;L of Enzyme Mix I (1 U/50 &#181;L), and 4 &#181;L of H2O. Perform RT-PCR using the following settings: 37 &#176;C for 15 min, 85 &#176;C for 5 s. Store the cDNA product at -4 &#176;C until use.</li>
	<li>Perform polymerase chain reaction (PCR) to amplify the dsRNA sequences in accordance with the referenced master mix (10 &#181;L of Taq II [1 U/50 &#181;L], 0.8 &#181;L of forward primer [0.4 &#181;M], 0.8 &#181;L of reverse primer [0.4 &#181;M], 0.8 &#181;L of DNA template [40 ng/&#181;L], and 7.6 &#181;L of H2O). Perform PCR using the following settings: 94 &#176;C for 2 min; 35 cycles with 94 &#176;C for 30 s, 60 &#176;C for 30 s, 72 &#176;C for 30; 72 &#176;C for 2 min.</li>
	<li>Assess the quality of PCR products by electrophoresis on a 2.0% agarose gel5,9 and confirm the target sequence through Sanger sequencing.</li>
	<li>Purify the PCR product using the Gel Extraction Kit as per the manufacturer&#39;s guidelines9,23.</li>
	<li>Utilize an RNAi System to synthesize dsRNA for the target gene with 10 &#181;L of 2x buffer (0.02 U/&#181;L), 8 &#181;L of DNA template (75 ng/&#181;L), and 2 &#181;L of enzyme mix (1 U/50 &#181;L) with the following settings: 37 &#176;C for 30 min, 70 &#176;C for 10 min, and 25 &#176;C for 20 min. Elute the synthesized dsRNA with 30 &#181;L of Nuclease-Free Water.</li>
	<li>Assess the quality of the dsRNA product by visualizing it on a 1.0% agarose gel5,9. Dilute the dsRNA to 7,000 ng/&#181;L. Check the quality of the dsRNA product; proceed if the value of OD260/OD280 ranges from 1.8 to 2.09. Store the dsRNA product at -20 &#176;C until use.</li>
</ol>
3. Transplantation of T. denrolimi pupae
<ol>
	<li>Cultivate the parasitized host eggs for approximately 8 days at 25 &#177; 1&#176;C, maintaining a 16 h light/8 h dark cycle and a relative humidity of ~75%. The parasitized host eggs will blacken after 5 days30 (Figure 1-iv,v).</li>
	<li>Transfer the host egg card to a dissecting microscope. Employ a pair of tungsten needles (Figure 1-vi) to meticulously remove the chorion from the host eggs (Figure 1-vii) and retrieve the pupa from within (Figure 1-viii)5,17,18. 
	NOTE: The tip of the dissecting needle should be less than 0.05 mm.</li>
	<li>Prepare a clean plate for the substrate. Pour out 10-15 mL of a 15 g/L agar solution, allowing it to naturally cool (Figure 2-i). 
	NOTE: Mix the agar solution with 0.5 g of streptomycin to inhibit the growth of contaminants in vitro.</li>
	<li>Employ a disinfected graver to etch several grooves measuring 0.2-0.3 mm in depth and 0.4-0.8 mm in width (Figure 2-ii).</li>
	<li>Use a small brush (Figure 2-iii) to transplant a pupa from the dissected host egg into one of the grooves on the agar substrate (Figure 2-iv).</li>
	<li>Repeat steps 3.4 and 3.5, transplanting 100-300 pupae individually into the grooves one by one (Figure 2-v).</li>
</ol>
4. Micro-injecting dsRNA into T. denrolimi pupa
<ol>
	<li>Use a glass needle puller to pull a glass capillary (Figure 3-i,ii). Set the Heat to 280, the Velocity to 170, the Delay to 250, and the Pull to 30 on a needle puller (Figure 3-iii). Prepare multiple capillary glass needles for microinjection (Figure 3-iv,v).</li>
	<li>Bevel the tip of the glass needle using an abrasive plate (Figure 3-vi). 
	NOTE: Ensure that the injection needle&#39;s tip remains sharp; otherwise, it may result in pupal mortality or impede reagent flow through the needle (Figure 3-vii).</li>
	<li>Load approximately 2 &#181;L of the dsRNA injection solution with 7,000 ng/&#181;L into the prepared injection needle using a micro-injection pump (Figure 3-vii).</li>
	<li>Transfer the agar substrate containing hundreds of pupae onto the platform of a compound microscope (Figure 3-viii).</li>
	<li>Carefully insert the injection needle into the abdomen of a T. denrolimi pupa at a ~30&#176; angle to the abdomen under the lens (Figure 3-ix).</li>
	<li>Gradually inject ~5 nL of the injection solution (step 4.3) into the T. denrolimi pupa as gently as possible. 
	NOTE: The T. denrolimi pupa may slightly swell as the dsRNA solution is injected. Injecting an excessive amount of solution into the pupa or using needles with overly large openings may result in premature pupal death. Change the needles when they become clogged after injecting several to tens of pupae.</li>
	<li>Repeat steps 4.5 and 4.6, injecting dsRNA into 600 pupae one by one. 
	&#8203;NOTE: For reliable RT-qPCR analysis, RNA content should be isolated from at least 100 pupae. Inject at least 600 pupae for three replicates in the dsRNA treatment and three replicates in the dsGFP negative control9.</li>
</ol>
5. Incubation of T. denrolimi pupae
<ol>
	<li>Transfer the substrate containing injected pupae to an incubator at 25 &#177; 1 &#176;C with a 16 h/8 h light/dark cycle and ~75% RH.</li>
	<li>Incubate approximately 700 T. denrolimi pupae per treatment for either 24 h or 48 h. Extract RNA content from a group of 100 pupae per replicate9. 
	&#8203;NOTE: Remove the shrunk pupae (dead pupae) from the samples; otherwise, it may result in errors in the detection of gene expression.</li>
	<li>Incubate ~50 T. denrolimi pupae per treatment until the wasps emerge (Figure 3-x). Record the emergence rate and deformity rate.</li>
</ol>
6. Detection of targeted gene expression
<ol>
	<li>Design the primer set for the target gene and reference genes for RT-qPCR using a design tool. 
	NOTE: Ensure that the sequences of the RT-qPCR primers do not overlap with the targeted region of dsRNA.</li>
	<li>Employ the gene forkhead box O (FoxO) as the reference gene in the RT-qPCR analysis; the primers of FoxO have been reported previously9.</li>
	<li>Obtain commercially synthesized primer sets. Perform RT-qPCR with 10 &#181;L of Taq II (1 U/50 &#181;L), 0.8 &#181;L of forward primer (0.4 &#181;M), 0.8 &#181;L of reverse primer (0.4 &#181;M), 0.8 &#181;L of template (10 ng/&#181;L), and 7.6 &#181;L of H2O. Perform RT-qPCR using the following settings: 95 &#176;C for 30 s; 35 cycles with 95 &#176;C for 5 s, 57 &#176;C for 30 s, 72 &#176;C for 30; 95 &#176;C for 10 s; 60 &#176;C for 5 s, and 95 &#176;C for 5 s.</li>
	<li>Calculate the expression value of the targeted gene by using the 2-&#916;&#916;Ct method9,25.</li>
	<li>Employ the Kruskal-Wallis test to analyze the expression of the target gene under the influence of different treatments (dsFerhch, dsGFP, non-injection). 
	NOTE: Avoid using parametric tests (e.g., t-test) for post-hoc comparisons as the data&#39;s heteroscedasticity and non-normality may lead to erroneous conclusions25.</li>
</ol>

Advancing RNAi Techniques in Trichogramma dendrolimi for Gene Function Analysis

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The authors declare that they have no conflicts of interest.

Trichogramma wasps are recognized as effective biological control agents, specifically targeting a range of lepidopteran pests in agriculture and forestry1. These diminutive wasps undergo their immature stages within the host egg, a characteristic that presents challenges in conducting RNAi experiments5,18. This study offers a comprehensive visual guide for conducting RNAi experiments in T. denrolimi. Given the shared bio...

Trichogramma spp. are a group of egg parasitoids that have been extensively utilized as highly efficient biological control agents against a wide spectrum of lepidopteran pests in agricultural and forest ecosystems worldwide1,2,3,4. The application of mass-reared Trichogramma provides an environmentally friendly approach for the sustainable management of pests5,6,7. Understanding the molecular biology of Trichogramma wasps provides valuable insights into enhancing the mass-rearing efficiency and field performance of these biological control agents8,9by investigating the methodology of gene regulation and genome editing10.
Since the discovery of double-stranded RNA (dsRNA)-mediated specific genetic interference in Caenorhabditis elegans in 1998, the RNA-interference (RNAi) method has evolved into a vital genetic toolkit for exploring the regulatory mechanisms of organisms by suppressing the expression of target genes11. RNAi experiments have become a standard methodology widely applied to study gene function in numerous insect species12,13. Nevertheless, the manipulation of RNAi presents a formidable challenge in many parasitoid species, particularly among those belonging to the endoparasitic Chalcidoidea family14,15,16. The RNAi method has been documented in at least 13 parasitoid species14,15,16,17,18,19. Among these, the RNAi approach has been comprehensively conducted in Nasonia wasps and is applicable throughout the developmental stages, including embryos, larvae, pupae, and adults14,15,16. It is noteworthy that Nasonia wasps are ectoparasitoids, with their offspring developing in the interstitial space between the host pupa and the puparium, enabling their cultivation in vitro and making them tolerate certain treatments, such as micro-injection. Unlike Nasonia wasps, Trichogramma individuals undergo their entire embryonic, larval, and pupal development inner the host egg. The layer at embryo and larva stages (which may impede dsRNA permeability), vulnerability to damage, and the difficulty in surviving in vitro present formidable obstacles20,21,22. Additionally, the diminutive size of Trichogramma individuals, approximately ~0.5 mm in adult or pupal length, renders them exceedingly intricate to manipulate20,21,22.
In the present study, we outline a comprehensive procedure for conducting RNA interference (RNAi) experiments in Trichogramma denrolimi Matsumura. This procedure encompasses the following procedures: (1) the design and synthesis of double-stranded RNA (dsRNA), (2) microinjection of T. denrolimi pupae, (3) the transplantation and in vitro incubation of these pupae, and (4) the detection of target gene knockdown through RT-qPCR analysis. The target gene selected for the RNAi experiment is the ferritin heavy chain homology (Ferhch). FerHCH, an iron-binding protein, contains a ferroxidase center endowed with antioxidant capabilities, facilitating the oxidation of Fe2+ to Fe3+. It plays an indispensable role in the growth and development of various organisms by maintaining redox equilibrium and iron homeostasis. Depletion of FerHCH can result in the overaccumulation of iron, leading to irreversible tissue damage, and often culminating in significant phenotypic alterations, including growth defects, deformities, and mortality23,24. This study offers a step-by-step guide for conducting RNAi in T. denrolimi, which will be invaluable for investigating the gene functions within the broader context of Trichogramma wasps.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2x ES Taq MasterMix (Dye)</td>
			<td>Cowin Biotech, China</td>
			<td>CW0690H</td>
			<td>To amplify the dsRNA sequences</td>
		</tr>
		<tr>
			<td>20x PBS Buffer, DEPC treated (7.2-7.6)</td>
			<td>Sangon Biotech, China</td>
			<td>B540627-0500</td>
			<td>To dilute dsRNA</td>
		</tr>
		<tr>
			<td>Agar strip</td>
			<td>Shishi Globe Agar Industries Co.,Ltd, China</td>
			<td>n/a</td>
			<td>To make culture medium</td>
		</tr>
		<tr>
			<td>Ampicillin sodium</td>
			<td>Sangon Biotech, China</td>
			<td>A610028</td>
			<td>To make culture medium</td>
		</tr>
		<tr>
			<td>Bioer Constant temperature metal bath&#160;</td>
			<td>BIOER, China</td>
			<td>MB-102</td>
			<td>To synthesis dsRNA</td>
		</tr>
		<tr>
			<td>Borosilicate glass capillary&#160;</td>
			<td>WPI, USA</td>
			<td>1B100-4</td>
			<td>To pull capillary glass needle</td>
		</tr>
		<tr>
			<td>Clean bench&#160;</td>
			<td>Airtech, China</td>
			<td>SW-CJ-1FD</td>
			<td>To extract RNA</td>
		</tr>
		<tr>
			<td>Double distilled water</td>
			<td>Sangon Biotech, China</td>
			<td>A500197-0500</td>
			<td>To dilute cDNA</td>
		</tr>
		<tr>
			<td>Environmental Testing chamber&#160;</td>
			<td>Panasonic, Japan</td>
			<td>MLR-352H-PC</td>
			<td>To culture T. denrolimi</td>
		</tr>
		<tr>
			<td>Eppendorf Centrifuge&#160;</td>
			<td>Eppendrof, Germany</td>
			<td>5418R</td>
			<td>To store RNA content</td>
		</tr>
		<tr>
			<td>Eppendorf FemtoJet 4i</td>
			<td>Eppendrof, Germany</td>
			<td>FemtoJet 4i</td>
			<td>To inject T. denrolimi</td>
		</tr>
		<tr>
			<td>Eppendorf Refrigerated Centrifuge&#160;</td>
			<td>Eppendrof, Germany</td>
			<td>5810R</td>
			<td>Centrifuge</td>
		</tr>
		<tr>
			<td>Ethanol solution (75%, RNase-free)</td>
			<td>Aladdin, China</td>
			<td>M052131-500ml</td>
			<td>To extract RNA</td>
		</tr>
		<tr>
			<td>Gel Extraction Kit</td>
			<td>Omega, USA</td>
			<td>D25000-02</td>
			<td>To extract cDNA</td>
		</tr>
		<tr>
			<td>GUM Arabic</td>
			<td>Solarbio, China</td>
			<td>CG5991-500g</td>
			<td>To make egg card</td>
		</tr>
		<tr>
			<td>Isopropyl alchohol</td>
			<td>Aladdin, China</td>
			<td>80109218</td>
			<td>To extract RNA</td>
		</tr>
		<tr>
			<td>Laser-Based Micropipette Puller&#160;</td>
			<td>SUTTER, USA</td>
			<td>P-2000</td>
			<td>To pull capillary glass needle</td>
		</tr>
		<tr>
			<td>Microloader&#160;</td>
			<td>Eppendrof, Germany</td>
			<td>20 &#181;L</td>
			<td>To load dsRNA</td>
		</tr>
		<tr>
			<td>Multi-sample tissue grinder&#160;</td>
			<td>LICHEN, China</td>
			<td>LC-TG-24</td>
			<td>To grind T. denrolimi</td>
		</tr>
		<tr>
			<td>Needle Grinder&#160;</td>
			<td>SUTTER, USA</td>
			<td>BV-10-E</td>
			<td>To grind capillary glass needle</td>
		</tr>
		<tr>
			<td>Nuclease-Free Water</td>
			<td>Sangon Biotech, China</td>
			<td></td>
			<td>To dilute RNA</td>
		</tr>
		<tr>
			<td>OLYMPUS Microscope</td>
			<td>OLYMPUS, Japan</td>
			<td>XZX16</td>
			<td>To observe T. denrolimi</td>
		</tr>
		<tr>
			<td>PCR machine&#160;</td>
			<td>Bio-rad, USA</td>
			<td>S-1000</td>
			<td>For DNA amplification</td>
		</tr>
		<tr>
			<td>PowerPac Basic</td>
			<td>Bio-rad, USA</td>
			<td>PowerPacTM Basic</td>
			<td>To detect the quality of dsRNA&#160;</td>
		</tr>
		<tr>
			<td>Primer of dsGFP (Forward)</td>
			<td></td>
			<td></td>
			<td>[TAATACGACTCACTATAGGG] 
			ACAAACCAAGGCAAGTAATA</td>
		</tr>
		<tr>
			<td>Primer of dsGFP (Reverse)</td>
			<td></td>
			<td></td>
			<td>[TAATACGACTCACTATAGGG] 
			CAGAGGCATCTTCAACG</td>
		</tr>
		<tr>
			<td>Primer of Ferhch for qPCR (Forward)</td>
			<td></td>
			<td></td>
			<td>TGAAGAGATTCTGCGTTCTGCT</td>
		</tr>
		<tr>
			<td>Primer of Ferhch for qPCR (Reverse)</td>
			<td></td>
			<td></td>
			<td>CTGTAGGAACATCAGCAGGCTT</td>
		</tr>
		<tr>
			<td>Primer of Ferhch for RNAi (Reverse)</td>
			<td></td>
			<td></td>
			<td>[TAATACGACTCACTATAGGG]AG 
			TAGCCATCATCTTTCC</td>
		</tr>
		<tr>
			<td>Primer of Ferhch for RNAi(Forward)</td>
			<td></td>
			<td></td>
			<td>[TAATACGACTCACTATAGGG] 
			ACACTGTCAATCGTCCTG</td>
		</tr>
		<tr>
			<td>Primer of FoxO for qPCR (Forward)</td>
			<td></td>
			<td></td>
			<td>CTACGCCGATCTCATAACGC</td>
		</tr>
		<tr>
			<td>Primer of FoxO for qPCR (Reverse)</td>
			<td></td>
			<td></td>
			<td>TGCTGTCGCCCTTGTCCT</td>
		</tr>
		<tr>
			<td>PrimeScript RT reagent Kit with gDNA Eraser (Perfect Real Time)</td>
			<td>TaKaRa, Japan</td>
			<td>RR047A</td>
			<td></td>
		</tr>
		<tr>
			<td>Quantitative Real-time PCR&#160;</td>
			<td>Bio-rad, USA</td>
			<td>CFX 96 Touch</td>
			<td>To perform reverse transcriptase polymerase chain reaction (RT-PCR)&#160;</td>
		</tr>
		<tr>
			<td>Real-time PCR (TaqMan) Primer and Probes Design Tool</td>
			<td></td>
			<td></td>
			<td>https://www.genscript.com/tools/real-time-pcr-taqman-primer-design-tool/</td>
		</tr>
		<tr>
			<td>T7 RiBoMAX Express RNAi System</td>
			<td>Promega, USA</td>
			<td>P1700</td>
			<td>To synthesis dsRNA &#160;in vitro&#160;</td>
		</tr>
		<tr>
			<td>TB Green Premix Ex TaqTM <img alt="Equation 1" src="/files/ftp_upload/66250/66250eq01.jpg" style="margin: auto;" /> (Til RnaseH Plus)</td>
			<td>TaKaRa, Japan</td>
			<td>RR820A</td>
			<td>To perform RT-qPCR</td>
		</tr>
		<tr>
			<td>Trichloromethane</td>
			<td>KESHI, China</td>
			<td>GB/T682-2002</td>
			<td>To extract RNA</td>
		</tr>
		<tr>
			<td>TRIzol Reagent</td>
			<td>Ambion, USA</td>
			<td>15596018</td>
			<td>To extract total RNA content from samples</td>
		</tr>
		<tr>
			<td>Ultra-low Temperature Freezer&#160;</td>
			<td>Thermo, USA</td>
			<td>Forma 911</td>
			<td></td>
		</tr>
	</tbody>
</table>

rna interference in the egg parasitoid, trichogramma dendrolimi matsumura

The egg parasitoids, Trichogramma spp, are recognized as efficient biological control agents against various lepidopteran pests in agriculture and forests. The immature stages of Trichogramma offspring develop within the host egg, exhibiting remarkable diminutiveness (approximately 0.5 mm in adult length). RNA-interference (RNAi) methodology has emerged as a crucial tool for elucidating gene functions in numerous organisms. However, manipulating RNAi in certain small parasitoid species, such as Trichogramma, has generally posed significant challenges. In this study, we present an efficient RNAi method in Trichogramma denrolimi. The outlined procedure encompasses the acquisition and isolation of individual T. dendrolimi specimens from host eggs, the design and synthesis of double-stranded RNA (dsRNA), the in vitro transplantation and cultivation of T. dendrolimi pupae, the micro-injection of dsRNA, and the subsequent assessment of target gene knockdown through RT-qPCR analysis. This study furnishes a comprehensive, visually detailed procedure for conducting RNAi experiments in T. dendrolimi, thereby enabling researchers to investigate the gene regulation in this species. Furthermore, this methodology is adaptable for RNAi studies or micro-injections in other Trichogramma species with minor adjustments, rendering it a valuable reference for conducting RNAi experiments in other endoparasitic species.

The emergence rate of T. denrolimi pupae injected with dsFerhch was significantly lower than that of those injected with dsGFP or those without injection (Table 1). Among the emerged wasps, 51.85% of T. denrolimi wasps subjected to dsFerhch developed deformed small wings. The deformed wasps were not observed in the wasps injected with dsGFP or without any injection (Table 1). Moreover, the abdomens of T. denrolimi pupae injec...

Watch this Scientific Journal Video about RNA Interference in the Egg Parasitoid, Trichogramma dendrolimi Matsumura at JoVE.com

Author Spotlight: Investigating Wolbachia-Induced Thelytokous Parthenogenesis and Genetic Toolkit Development Through RNA Interference

The manipulation of RNA interference (RNAi) presents a formidable challenge in many parasitoid species with diminutive size, such as Trichogramma wasps. This study delineated an efficient RNAi method in Trichogramma denrolimi. The present methodology provides a robust model for investigating gene regulation in Trichogramma wasps.

RNA Interference in the Egg Parasitoid, Trichogramma dendrolimi Matsumura

The egg parasitoids, Trichogramma spp, are recognized as efficient biological control agents against various lepidopteran pests in agriculture and ...

Trichogramma wasps are a group of egg parasitoids used to control lepidopteran pests in agriculture. The intracellular bacteria Wolbachia induces thelytokous parthenogenesis in some Trichogramma wasps. We are trying to answer the mechanism of Wolbachia and sex-determination systems in Trichogramma wasps.We have developed the RNA interference method in Trichogramma wasps. This method is a vital genetic toolkit for investigating the gene functions of Trichogramma. The immature stages of Trichogramma offspring develop within the host egg.The body size of Trichogramma is extremely small and is approximately 0.5 millimeter in adult length. The manipulation of genetic tools such as RNA interference and genome editing presents a formidable challenge for these tiny parasitoid wasps. For decades, gene functions within the entire Trichogramma genus have been rarely explored.The present methodology provides a robust model for investigating gene regulation during developmental and physiological activities in Trichogramma wasps.

rna-interference-egg-parasitoid-trichogramma-dendrolimi

Research

JoVE Journal

Biology

1.1K Views.  Shenyang Agricultural University. Trichogramma wasps are a group of egg parasitoids used to control lepidopteran pests in agriculture. The intracellular bacteria Wolbachia induces thelytokous parthenogenesis in some Trichogramma wasps. We are trying to answer the mechanism of Wolbachia and sex-determination systems in Trichogramma wasps.We have developed the RNA interference method in Trichogramma wasps. This method is a vital genetic toolkit for investigating the gene functions of Trichogramma. The immature stages of ...

Video: Author Spotlight: Investigating Wolbachia-Induced Thelytokous Parthenogenesis and Genetic Toolkit Development Through RNA Interference

In vitro Transcription and Capping of Gaussia Luciferase mRNA Followed by HeLa Cell Transfection

In vitro transcription is the synthesis of RNA transcripts by RNA polymerase from a linear DNA template containing the corresponding promoter sequence (T7, T3, SP6) and the gene to be transcribed (Figure 1A). A typical transcription reaction consists of the template DNA, RNA polymerase, ribonucleotide triphosphates, RNase inhibitor and buffer containing Mg2+ ions.
Large amounts of high quality RNA are often required for a variety of applications. Use of in vitro transcription has been reported for RNA structure and function studies such as splicing1, RNAi experiments in mammalian cells2, antisense RNA amplification by the "Eberwine method"3, microarray analysis4 and for RNA vaccine studies5. The technique can also be used for producing radiolabeled and dye labeled probes6. Warren, et al. recently reported reprogramming of human cells by transfection with in vitro transcribed capped RNA7. The T7 High Yield RNA Synthesis Kit from New England Biolabs has been designed to synthesize up to 180 &mu;g RNA per 20 &mu;l reaction. RNA of length up to 10kb has been successfully transcribed using this kit. Linearized plasmid DNA, PCR products and synthetic DNA oligonucleotides can be used as templates for transcription as long as they have the T7 promoter sequence upstream of the gene to be transcribed.
Addition of a 5' end cap structure to the RNA is an important process in eukaryotes. It is essential for RNA stability8, efficient translation9, nuclear transport10 and splicing11. The process involves addition of a 7-methylguanosine cap at the 5' triphosphate end of the RNA. RNA capping can be carried out post-transcriptionally using capping enzymes or co-transcriptionally using cap analogs. In the enzymatic method, the mRNA is capped using the Vaccinia virus capping enzyme12,13. The enzyme adds on a 7-methylguanosine cap at the 5' end of the RNA using GTP and S-adenosyl methionine as donors (cap 0 structure). Both methods yield functionally active capped RNA suitable for transfection or other applications14 such as generating viral genomic RNA for reverse-genetic systems15 and crystallographic studies of cap binding proteins such as eIF4E16.
In the method described below, the T7 High Yield RNA Synthesis Kit from NEB is used to synthesize capped and uncapped RNA transcripts of Gaussia luciferase (GLuc) and Cypridina luciferase (CLuc). A portion of the uncapped GLuc RNA is capped using the Vaccinia Capping System (NEB). A linearized plasmid containing the GLuc or CLuc gene and T7 promoter is used as the template DNA. The transcribed RNA is transfected into HeLa cells and cell culture supernatants are assayed for luciferase activity. Capped CLuc RNA is used as the internal control to normalize GLuc expression.

In vitro Transcription and Capping of Gaussia Luciferase mRNA Followed by HeLa Cell Transfection

This method describes high yield in vitro synthesis of both capped and uncapped mRNA from a linearized plasmid containing the Gaussia luciferase (GLuc) gene. The RNA is purified and a fraction of the uncapped RNA is enzymatically capped using the Vaccinia virus capping enzyme. In the final step, the mRNA is transfected into HeLa cells and cell culture supernatants are assayed for luciferase activity.

In vitro transcription is the synthesis of RNA transcripts by RNA polymerase from a linear DNA template containing the corresponding promoter sequence ...

Using RNA-mediated Interference Feeding Strategy to Screen for Genes Involved in Body Size Regulation in the Nematode C. elegans

Double-strand RNA-mediated interference (RNAi) is an effective strategy to knock down target gene expression1-3. It has been applied to many model systems including plants, invertebrates and vertebrates. There are various methods to achieve RNAi in vivo4,5. For example, the target gene may be transformed into an RNAi vector, and then either permanently or transiently transformed into cell lines or primary cells to achieve gene knockdown effects; alternatively synthesized double-strand oligonucleotides from specific target genes (RNAi oligos) may be transiently transformed into cell lines or primary cells to silence target genes; or synthesized double-strand RNA molecules may be microinjected into an organism. Since the nematode C. elegans uses bacteria as a food source, feeding the animals with bacteria expressing double-strand RNA against target genes provides a viable strategy6. Here we present an RNAi feeding method to score body size phenotype. Body size in C. elegans is regulated primarily by the TGF- &beta; - like ligand DBL-1, so this assay is appropriate for identification of TGF-&beta; signaling components7. We used different strains including two RNAi hypersensitive strains to repeat the RNAi feeding experiments. Our results showed that rrf-3 strain gave us the best expected RNAi phenotype. The method is easy to perform, reproducible, and easily quantified. Furthermore, our protocol minimizes the use of specialized equipment, so it is suitable for smaller laboratories or those at predominantly undergraduate institutions.

Using RNA-mediated Interference Feeding Strategy to Screen for Genes Involved in Body Size Regulation in the Nematode C. elegans

We demonstrate how to use the RNAi feeding technique to knock down target genes and score body size phenotype in C. elegans. This method could be used for a large scale screen to identify potential genetic components of interest, such as those involved in body size regulation by DBL-1/TGF-&beta; signaling.

Double-strand RNA-mediated interference (RNAi) is an effective strategy to knock down target gene expression1-3. It has been applied to many model systems ...

Reconstitution Of &#946;-catenin Degradation In Xenopus Egg Extract

Xenopus laevis egg extract is a well-characterized, robust system for studying the biochemistry of diverse cellular processes. Xenopus egg extract has been used to study protein turnover in many cellular contexts, including the cell cycle and signal transduction pathways1-3. Herein, a method is described for isolating Xenopus egg extract that has been optimized to promote the degradation of the critical Wnt pathway component, &beta;-catenin. Two different methods are described to assess &beta;-catenin protein degradation in Xenopus egg extract. One method is visually informative ([35S]-radiolabeled proteins), while the other is more readily scaled for high-throughput assays (firefly luciferase-tagged fusion proteins). The techniques described can be used to, but are not limited to, assess &beta;-catenin protein turnover and identify molecular components contributing to its turnover. Additionally, the ability to purify large volumes of homogenous Xenopus egg extract combined with the quantitative and facile readout of luciferase-tagged proteins allows this system to be easily adapted for high-throughput screening for modulators of &beta;-catenin degradation.

Reconstitution Of &amp;#946;-catenin Degradation In Xenopus Egg Extract

A method is described for analyzing protein degradation using radiolabeled and luciferase-fusion proteins in Xenopus egg extract and its adaptation for high-throughput screening for small molecule modulators of protein degradation.

Xenopus laevis egg extract is a well-characterized, robust system for studying the biochemistry of diverse cellular processes. Xenopus egg extract has ...

Larval RNA Interference in the Red Flour Beetle, Tribolium castaneum

The red flour beetle, Tribolium&#160;castaneum, offers a repertoire of experimental tools for genetic and developmental studies, including a fully annotated genome sequence, transposon-based transgenesis, and effective RNA interference (RNAi). Among these advantages, RNAi-based gene knockdown techniques are at the core of Tribolium research. T. castaneum show a robust systemic RNAi response, making it possible to perform RNAi at any life stage by simply injecting double-stranded RNA (dsRNA) into the beetle&#8217;s body cavity.
In this report, we provide an overview of our larval RNAi technique in T. castaneum. The protocol includes (i) isolation of the proper stage of T. castaneum larvae for injection, (ii) preparation for the injection setting, and (iii) dsRNA injection. Larval RNAi is a simple, but powerful technique that provides us with quick access to loss-of-function phenotypes, including multiple gene knockdown phenotypes as well as a series of hypomorphic phenotypes. Since virtually all T. castaneum tissues are susceptible to extracellular dsRNA, the larval RNAi technique allows researchers to study a wide variety of tissues in diverse contexts, including the genetic basis of organismal responses to the outside environment. In addition, the simplicity of this technique stimulates more student involvement in research, making T. castaneum an ideal genetic system for use in a classroom setting.

Larval RNA Interference in the Red Flour Beetle, Tribolium castaneum

RNA interference (RNAi)-based gene knockdown techniques are at the core of Tribolium research. Here, we provide an overview of our larval RNAi technique in Tribolium castaneum. Larval RNAi is a simple, but powerful technique that provides quick access to loss-of-function phenotypes, allowing researchers to study gene functions in diverse contexts.

The red flour beetle, Tribolium&#160;castaneum, offers a repertoire of experimental tools for genetic and developmental studies, including a fully ...

Practical Use of RNA Interference: Oral Delivery of Double-stranded RNA in Liposome Carriers for Cockroaches

RNA interference (RNAi) has been widely applied for uncovering the biological functions of numerous genes, and has been envisaged as a pest control tool operating by disruption of essential gene expression. Although different methods, such as injection, feeding, and soaking, have been reported for successful delivery of double-stranded RNA (dsRNA), the efficiency of RNAi through oral delivery of dsRNA is highly variable among different insect groups. The German cockroach, Blattella germanica, is highly sensitive to the injection of dsRNA, as shown by many studies published previously. The present study describes a method to demonstrate that the dsRNA encapsulated with liposome carriers is sufficient to retard the degradation of dsRNA by midgut juice. Notably, the continuous feeding of dsRNA encapsulated by liposomes significantly reduces the tubulin expression in the midgut, and led to the death of cockroaches. In conclusion, the formulation and utilization of dsRNA lipoplexes, which protect dsRNA against nucleases, could be a practical use of RNAi for insect pest control in the future.

This manuscript demonstrates the depletion of gene expression in the midgut of the German cockroach through oral ingestion of double-stranded RNA encapsulated in liposomes.

RNA interference (RNAi) has been widely applied for uncovering the biological functions of numerous genes, and has been envisaged as a pest control tool ...

TChIP-Seq: Cell-Type-Specific Epigenome Profiling

Epigenetic regulation plays central roles in gene expression. Since histone modification was discovered in the 1960s, its physiological and pathological functions have been extensively studied. Indeed, the advent of next-generation deep sequencing and chromatin immunoprecipitation (ChIP) via specific histone modification antibodies has revolutionized our view of epigenetic regulation across the genome. Conversely, tissues typically consist of diverse cell types, and their complex mixture poses analytic challenges to investigating the epigenome in a particular cell type. To address the cell type-specific chromatin state in a genome-wide manner, we recently developed tandem chromatin immunoprecipitation sequencing (tChIP-Seq), which is based on the selective purification of chromatin by tagged core histone proteins from cell types of interest, followed by ChIP-Seq. The goal of this protocol is the introduction of best practices of tChIP-Seq. This technique provides a versatile tool for tissue-specific epigenome investigation in diverse histone modifications and model organisms.

We describe a step-by-step protocol for tandem chromatin immunoprecipitation sequencing (tChIP-Seq) that enables the analysis of cell-type-specific genome-wide histone modification.

Epigenetic regulation plays central roles in gene expression. Since histone modification was discovered in the 1960s, its physiological and pathological ...

Visualizing and Tracking Endogenous mRNAs in Live Drosophila melanogaster Egg Chambers

Fluorescence-based imaging techniques, in combination with developments in light microscopy, have revolutionized how cell biologists conduct live cell imaging studies. Methods for detecting RNAs have expanded greatly since seminal studies linked site-specific mRNA localization to gene expression regulation. Dynamic mRNA processes can now be visualized via approaches that detect mRNAs, coupled with microscopy set-ups that are fast enough to capture the dynamic range of molecular behavior. The molecular beacon technology is a hybridization-based approach capable of direct detection of endogenous transcripts in living cells. Molecular beacons are hairpin-shaped, internally quenched, single-nucleotide discriminating nucleic acid probes, which fluoresce only upon hybridization to a unique target sequence. When coupled with advanced fluorescence microscopy and high-resolution imaging, they enable one to perform spatial and temporal tracking of intracellular movement of mRNAs. Although this technology is the only method capable of detecting endogenous transcripts, cell biologists have not yet fully embraced this technology due to difficulties in designing such probes for live cell imaging. A new software application, PinMol, allows for enhanced and rapid design of probes best suited to efficiently hybridize to mRNA target regions within a living cell. In addition, high-resolution, real-time image acquisition and current, open source image analysis software allow for a refined data output, leading to a finer evaluation of the complexity underlying the dynamic processes involved in the mRNA&#39;s life cycle.
Here we present a comprehensive protocol for designing and delivering molecular beacons into Drosophila melanogaster egg chambers. Direct and highly specific detection and visualization of endogenous maternal mRNAs is performed via spinning disc confocal microscopy. Imaging data is processed and analyzed using object detection and tracking in Icy software to obtain details about the dynamic movement of mRNAs, which are transported and localized to specialized regions within the oocyte.

Visualizing and Tracking Endogenous mRNAs in Live Drosophila melanogaster Egg Chambers

Here, we present a protocol for the visualization, detection, analysis and tracking of endogenous mRNA trafficking in live Drosophila melanogaster egg chamber using molecular beacons, spinning disc confocal microscopy, and open-source analysis software.

Fluorescence-based imaging techniques, in combination with developments in light microscopy, have revolutionized how cell biologists conduct live cell ...

Nuclei Isolation from Adult Mouse Kidney for Single-Nucleus RNA-Sequencing

The kidneys regulate diverse biological processes such as water, electrolyte, and acid-base homeostasis. Physiological functions of the kidney are executed by multiple cell types arranged in a complex architecture across the corticomedullary axis of the organ. Recent advances in single-cell transcriptomics have accelerated the understanding of cell type-specific gene expression in renal physiology and disease. However, enzyme-based tissue dissociation protocols, which are frequently utilized for single-cell RNA-sequencing (scRNA-seq), require mostly fresh (non-archived) tissue, introduce transcriptional stress responses, and favor the selection of abundant cell types of the kidney cortex resulting in an underrepresentation of cells of the medulla.
Here, we present a protocol that avoids these problems. The protocol is based on nuclei isolation at 4 &#176;C from frozen kidney tissue. Nuclei are isolated from a central piece of the mouse kidney comprised of the cortex, outer medulla, and inner medulla. This reduces the overrepresentation of cortical cells typical for whole-kidney samples for the benefit of medullary cells such that data will represent the entire corticomedullary axis at sufficient abundance. The protocol is simple, rapid, and adaptable and provides a step towards the standardization of single-nuclei transcriptomics in kidney research.

Here, we present a protocol to isolate high-quality nuclei from frozen mouse kidneys that improve the representation of medullary kidney cell types and avoids the gene expression artifacts from enzymatic tissue dissociation.

The kidneys regulate diverse biological processes such as water, electrolyte, and acid-base homeostasis. Physiological functions of the kidney are ...

Effective Oral RNA Interference (RNAi) Administration to Adult Anopheles gambiae Mosquitoes

RNA interference has been a heavily utilized tool for reverse genetic analysis for two decades. In adult mosquitoes, double-stranded RNA (dsRNA) administration has been accomplished primarily via injection, which requires significant time and is not suitable for field applications. To overcome these limitations, here we present a more efficient method for robust activation of RNAi by oral delivery of dsRNA to adult Anopheles gambiae. Long dsRNAs were produced in Escherichia coli strain HT115 (DE3), and a concentrated suspension of heat-killed dsRNA-containing bacteria in 10% sucrose was offered on cotton balls ad-libitum to adult mosquitoes. Cotton balls were replaced every 2 days for the duration of the treatment. Use of this method to target doublesex (a gene involved in sex differentiation) or fork head (which encodes a salivary gland transcription factor) resulted in reduced target gene expression and/or protein immunofluorescence signal, as measured by quantitative Real-Time PCR (qRT-PCR) or fluorescence confocal microscopy, respectively. Defects in salivary gland morphology were also observed. This highly flexible, user-friendly, low-cost, time-efficient method of dsRNA delivery could be broadly applicable to target genes important for insect vector physiology and beyond.

Effective Oral RNA Interference RNAi Administration to Adult Anopheles gambiae Mosquitoes

The oral administration of dsRNA produced by bacteria, a delivery method for RNA interference (RNAi) that is routinely used in Caenorhabditis elegans, was successfully applied here to adult mosquitoes. Our method allows for robust reverse genetics studies and transmission-blocking vector studies without the use of injection.

RNA interference has been a heavily utilized tool for reverse genetic analysis for two decades. In adult mosquitoes, double-stranded RNA (dsRNA) ...

Application of RNA Interference in the Pinewood Nematode, Bursaphelenchus xylophilus

The pinewood nematode, Bursaphelenchus xylophilus, is one of the most destructive invasive species worldwide, causing the wilting and eventual death of pine trees. Despite the recognition of their economic and environmental significance, it has thus far been impossible to study the detailed gene functions of plant-parasitic nematodes (PPNs) using conventional forward genetics and transgenic methods. However, as a reverse genetics technology, RNA interference (RNAi) facilitates the study of the functional genes of nematodes, including B. xylophilus. 
This paper outlines a new protocol for RNAi of the ppm-1 gene in B. xylophilus, which has been reported to play crucial roles in the development and reproduction of other pathogenic nematodes. For RNAi, the T7 promoter was linked to the 5&#8242;-terminal of the target fragment by polymerase chain reaction (PCR), and double-stranded RNA (dsRNA) was synthesized by in vitro transcription. Subsequently, dsRNA delivery was accomplished by soaking the nematodes in a dsRNA solution mixed with synthetic neurostimulants. Synchronized juveniles of B. xylophilus (approximately 20,000 individuals) were washed and soaked in dsRNA (0.8 &#181;g/mL) in the soaking buffer for 24 h in the dark at 25 &#176;C.
The same quantity of nematodes was placed in a soaking buffer without dsRNA as a control. Meanwhile, another identical quantity of nematodes was placed in a soaking buffer with green fluorescent protein (gfp) gene dsRNA as a control. After soaking, the expression level of the target transcripts was determined using real-time quantitative PCR. The effects of RNAi were then confirmed using microscopic observation of the phenotypes and a comparison of the body size of the adults among the groups. The current protocol can help advance research to better understand the functions of the genes of B. xylophilus and other parasitic nematodes toward developing control strategies through genetic engineering.

Application of RNA Interference in the Pinewood Nematode, Bursaphelenchus xylophilus

Here, we introduce a detailed soaking method of RNA interference in Bursaphelenchus xylophilus to facilitate the study of gene functions.

The pinewood nematode, Bursaphelenchus xylophilus, is one of the most destructive invasive species worldwide, causing the wilting and eventual death of ...