Name: improved fecundity and fertility assay for aedes aegypti using 24 well tissue culture plates (eagal plates)
Uploaded: 2021-05-04T12:30:00
Description: Watch this Scientific Journal Video about Improved Fecundity and Fertility Assay for Aedes aegypti using 24 Well Tissue Culture Plates EAgaL Plates at JoVE.com

We thank Texas A&#38;M Agrilife Research Insect Vectored Diseases Grant Program for funding. We also thank the Adelman lab members for help on developing this method and suggestions when drafting the manuscript, as well as Kevin Myles lab members. We also thank the reviewers and editors for their help to make this manuscript better.

1. Plate preparation
<ol>
	<li>Drill holes in 24 well tissue culture plate lids (4&#8722;6 holes per well) using a household drill with a ~1.6 mm (1/16 in) bit (Figure 2). 
	NOTE: These holes prevent water condensation from agarose to accumulate on the lid, where mosquitoes may lay eggs. The standard size of female Ae. aegypti (&#34;Liverpool&#34; strain) is ~3.11 mm wingspan. Reducing the size of the holes is recommended when using smaller mosquitoes to avoid escape from the...

<ol>
	<li>Bond, J. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+irradiation+dose+to+Aedes+aegypti+and+Ae.+albopictus+in+a+sterile+insect+technique+program.">Optimization of irradiation dose to Aedes aegypti and Ae. albopictus in a sterile insect technique program.</a> PLoS One. 14 (2), 0212520 (2019).</li><li>Fernandes, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aedes+aegypti+larvae+treated+with+spinosad+produce+adults+with+damaged+midgut+and+reduced+fecundity.">Aedes aegypti larvae treated with spinosad produce adults with damaged midgut and reduced fecundity.</a> Chemosphere. 221, 464-470 (2019).</li><li>Inocente, E. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insecticidal+and+Antifeedant+Activities+of+Malagasy+Medicinal+Plant+(Cinnamosma+sp.)+Extracts+and+Drimane-Type+Sesquiterpenes+against+Aedes+aegypti+Mosquitoes.">Insecticidal and Antifeedant Activities of Malagasy Medicinal Plant (Cinnamosma sp.) Extracts and Drimane-Type Sesquiterpenes against Aedes aegypti Mosquitoes.</a> Insects. 10 (11), 373 (2019).</li><li>Marrelli, M. T., Moreira, C. K., Kelly, D., Alphey, L., Jacobs-Lorena, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquito+transgenesis:+what+is+the+fitness+cost.">Mosquito transgenesis: what is the fitness cost.</a> Trends in Parasitology. 22 (5), 197-202 (2006).</li><li>da Silva Costa, G., Rodrigues, M. M. S., Silva, A. A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+a+blood-free+diet+for+Anopheles+darlingi+(Diptera:+Culicidae).">Toward a blood-free diet for Anopheles darlingi (Diptera: Culicidae).</a> Journal of Medical Entomology. , 217 (2019).</li><li>Gonzales, K. K., Tsujimoto, H., Hansen, I. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+serum+and+BSA,+but+neither+red+blood+cells+nor+hemoglobin+can+support+vitellogenesis+and+egg+production+in+the+dengue+vector+Aedes+aegypti.">Blood serum and BSA, but neither red blood cells nor hemoglobin can support vitellogenesis and egg production in the dengue vector Aedes aegypti.</a> PeerJ. 3, 938 (2015).</li><li>Gonzales, K. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Effect+of+SkitoSnack,+an+Artificial+Blood+Meal+Replacement,+on+Aedes+aegypti+Life+History+Traits+and+Gut+Microbiota.">The Effect of SkitoSnack, an Artificial Blood Meal Replacement, on Aedes aegypti Life History Traits and Gut Microbiota.</a> Scientific Reports. 8 (1), 11023 (2018).</li><li>Tsujimoto, H., Anderson, M. A. E., Myles, K. M., Adelman, Z. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+Candidate+Iron+Transporters+From+the+ZIP/ZnT+Gene+Families+in+the+Mosquito+Aedes+aegypti.">Identification of Candidate Iron Transporters From the ZIP/ZnT Gene Families in the Mosquito Aedes aegypti.</a> Frontiers in Physiology. 9, 380 (2018).</li><li>Ioshino, R. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oviplate:+A+Convenient+and+Space-Saving+Method+to+Perform+Individual+Oviposition+Assays+in+Aedes+aegypti.">Oviplate: A Convenient and Space-Saving Method to Perform Individual Oviposition Assays in Aedes aegypti.</a> Insects. 9 (3), 103 (2018).</li><li>Price, D. P., Schilkey, F. D., Ulanov, A., Hansen, I. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+mosquitoes,+large+implications:+crowding+and+starvation+affects+gene+expression+and+nutrient+accumulation+in+Aedes+aegypti.">Small mosquitoes, large implications: crowding and starvation affects gene expression and nutrient accumulation in Aedes aegypti.</a> Parasites &amp; Vectors. 8, 252 (2015).</li><li>Valerio, L., Matilda Collins, C., Lees, R. S., Benedict, M. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Benchmarking+vector+arthropod+culture:+an+example+using+the+African+malaria+mosquito,+Anopheles+gambiae+(Diptera:+Culicidae).">Benchmarking vector arthropod culture: an example using the African malaria mosquito, Anopheles gambiae (Diptera: Culicidae).</a> Malaria Journal. 15 (1), 262 (2016).</li><li>Rueden, C. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ImageJ2:+ImageJ+for+the+next+generation+of+scientific+image+data.">ImageJ2: ImageJ for the next generation of scientific image data.</a> BMC Bioinformatics. 18 (1), 529 (2017).</li></ol>

The EAgaL plate drastically reduces labor, time, and space to conduct individual fecundity and fertility assays in Aedes aegypti when compared to the FT method. Preliminary comparison between the FT method and the EAgaL plate resulted in shorter times for all steps (imaging technique was applied to the FT method) (Table 1). As a reference, an estimate of startup and&#160;per assay (one 24 well EAgaL plate versus 24 FTs) costs are provided in Table 2.
<p class="jove_...

The control of mosquitoes to protect humans from vector-borne pathogens is an important public health goal, mainly due to the lack of effective vaccines for most of the pathogens carried by mosquitoes. Many studies aim to reduce mosquito fitness in conjunction with a field-applicable population reduction strategy1,2,3. This includes extensive studies to create transgenic mosquitoes and/or CRISPR/Cas9 knockout lines. Such population modification approaches require a detailed assessment of individual fitness parameters4. Conventional laboratory techniques to assess the fitness of female mosquitoes includes the individual containment of mated, blood-fed female mosquitoes in 100 mL containers5, modified 50 mL conical tubes, or tubes for Drosophila rearing modified by providing moist surfaces using damp cotton and filter paper discs for oviposition (i.e., egg papers)1,2,6,7. Such methods require a relatively large space (e.g., 30 cm x 30 cm x 10 cm: W x L x H for up to 100 Drosophila tubes) (Figure 1), and the manipulation of individual egg papers for counting eggs and hatching larvae, which can be labor intensive. This manuscript presents a method to count mosquito eggs and determine hatch rates using 24 well plates and agarose as an oviposition surface to circumvent these issues8.
Concurrently, Ioshino et al.9 described a detailed method using 12 and 24 well plates to perform egg counting obtained from individual females. Their protocol represented a significant improvement from conventional methods in saving time and space9. However, the protocol they described continues to use wet filter paper as a surface for oviposition, which requires unfolding each individual paper to get counts, as eggs are often found underneath or in folds. Their protocol also did not include the use of imaging technologies or a method for larval counting.
Presented is an improved method to perform fitness assays for egg number (i.e., fecundity) and hatch rate (i.e., fertility) using agarose as an oviposition surface in a 24 well tissue culture plate format for Ae. aegypti that oviposit on moist surfaces. These plates were named &#8220;EAgaL&#8221; plates, from Egg, Agarose, and Larva. These 24 well plates provide individual mosquitoes with a minimal surface to lay eggs, thus simplifying and drastically reducing the time and effort needed to count and maintain eggs and hatched larvae for a few days. The EAgaL plate uses translucent agarose for the oviposition surface, which eliminates the need for handling egg papers and finding the eggs and larvae when hatched; photographing each well establishes a long-term archived record of the results and separates the counting process in both time and space from the rearing/handling process, where time is often limited.

<table>
	<tbody>
		<tr>
			<td>1.6 mm &#934; drill bit</td>
			<td></td>
			<td></td>
			<td>alternatively heated nails can be used</td>
		</tr>
		<tr>
			<td>1000 &#956;L pipette tips (long)</td>
			<td>Olympus plastics</td>
			<td>24-165RL</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well tissue culture plate</td>
			<td>Thermo Scientific</td>
			<td>930186</td>
			<td>clear, flat-bottom with ringed lid plates</td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>VWR</td>
			<td>0710-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Compact digital camera</td>
			<td>Olympus</td>
			<td>TG-5/TG-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Computer (Windows, Mac or Linux)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Deionized water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fiji (imageJ) software</td>
			<td></td>
			<td></td>
			<td>download from: https://fiji.sc/</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Dumont</td>
			<td></td>
			<td>sharp forceps may break mosquito&#39;s body</td>
		</tr>
		<tr>
			<td>Glass Petri dishes</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Household bleach</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Household electric drill</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>illuminator for stereomicroscope (gooseneck)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>P-1000 pipette</td>
			<td>Gilson</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>paint brushes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rubber bands</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SD card</td>
			<td></td>
			<td></td>
			<td>to record digital camera images (DSHC, SDXC should be better)</td>
		</tr>
		<tr>
			<td>Spreadsheet software (Microsoft Excel)</td>
			<td>Microsoft</td>
			<td></td>
			<td>Any spreadsheet software works</td>
		</tr>
		<tr>
			<td>TetraMin fish food</td>
			<td>Tetra</td>
			<td></td>
			<td>ground with coffee grinder, blender or morter &#38; pestle</td>
		</tr>
		<tr>
			<td>Transfer pipetts</td>
			<td>VWR</td>
			<td>16011-188</td>
			<td></td>
		</tr>
	</tbody>
</table>

improved fecundity and fertility assay for aedes aegypti using 24 well tissue culture plates (eagal plates)

Mosquitoes represent a significant public health problem as vectors of various pathogens. For those studies that require an assessment of mosquito fitness parameters, in particular egg production and hatch rates at the individual level, conventional methods have put a substantial burden on investigators due to high labor intensity and laboratory space requirements. Described is a simple method using 24 well tissue culture plate with agarose in each well and digital imaging of each well to determine egg numbers and hatch rates at an individual level with substantially reduced time and space requirements.

Mosquitoes were injected with dsRNA targeting a candidate iron transporter (FeT) or control gene (EGFP), blood-fed, and measured for fecundity and fertility output using the EAgaL plate method, following the procedure described above.
Mosquitoes in which FeT expression was silenced following dsRNA injection exhibited a significant reduction in both egg number and hatch rate (Figure 11A&#8722;C). All control and treatment mosquitoes were placed in ...

Watch this Scientific Journal Video about Improved Fecundity and Fertility Assay for Aedes aegypti using 24 Well Tissue Culture Plates EAgaL Plates at JoVE.com

Improved Fecundity and Fertility Assay for Aedes aegypti using 24 Well Tissue Culture Plates EAgaL Plates

Described is a time and space-saving method to count eggs and determine hatch rates of individual mosquitoes using 24 well tissue culture plates, which can substantially increase the scale and speed of fecundity and fertility assays.

Improved Fecundity and Fertility Assay for Aedes aegypti using 24 Well Tissue Culture Plates (EAgaL Plates)

Mosquitoes represent a significant public health problem as vectors of various pathogens. For those studies that require an assessment of mosquito fitness ...

This procedure allows mosquito researchers to easily address their mosquitoes'reproductive fitness at the individual level. Compared to conventional methods, this protocol significantly reduces the time, space and labor required to test mosquitoes'fecundity and fertility at the individual level. Begin by preparing plates for the oviposition experiment.Drill four to six holes per well in the lid of a 24-well culture plate using a household drill with a 1.6 millimeter bit. One day before the experiment, wash and rinse the plates and soak them in 1%to 5%bleach for 30 to 60 minutes at room temperature. Then, rinse the plates thoroughly under running deionized water and dry them.Melt 2%agarose in deionized water and immediately add 500 microliters of the molten agarose to each well of a 24-well plate. Leave the plates on the lab bench overnight to dry out any condensation. At least 16 hours before the blood feeding, remove any source of water or sugar from the female mosquitoes.On the day of the feeding, heat a water circulator to 37 degrees Celsius and feed the mosquitoes with vertebrate blood placed in artificial feeders for 15 to 30 minutes. Then, transfer the mosquitoes to a glass dish on ice. Select the ones that are engorged with blood and place them into a container with 30%sucrose water.Allow at least 72 hours for the females to finish excretion and egg development. About one hour before transferring mosquitoes to the 24-well plate, use a transfer pipette to add two to three drops of water into each well. Knock down mosquitoes with carbon dioxide and transfer them to a glass dish on ice.Then, individually place each mosquito on an inverted lid of the 24-well plate. Once all 24 mosquitoes have been placed, cover the lid with an inverted plate bottom, secure it with a fresh new rubber band and place it in an environmental chamber until mosquitoes recover. Then, turn the plate right side up.Allow the female mosquitoes to oviposit for 24 to 48 hours. Then, remove the females by releasing them from the plates into a large cage. Before counting the eggs, check each well for eggs that are on the well walls and at the margin of the agarose and plastic surface where they are difficult to resolve in photographs.Use a wet paintbrush to move these eggs to the flat surface so that all eggs are in a uniform plane and do not overlap each other. Use forceps to remove any broken legs, wings, and other particles in the wells that may interfere with imaging eggs. Set a compact digital camera in microscope mode, which allows the user to focus on objects as close as one centimeter and take an image of each well.After photographing each well of a plate, take an image of the entire plate. Use an imaging order label to distinguish each plate later. Add about five drops of water to each well to prevent its agarose plug and the eggs from drying and to induce embryo development and hatching.Transfer the images to a computer and rename the files with the plate and well IDs for easier organization. Open the images with ImageJ and use the Multi-point Tool to mark each egg, zooming in or out to count the egg clumps. After marking all the eggs, double click the Multi-point icon to bring up the number of marks and record the results in a spreadsheet.Start adding food to the wells that contain hatched larvae as soon as they appear. Approximately five to eight days later, anesthetize the larvae by covering the plate with crushed ice for 15 to 20 minutes. Insert a black material underneath the plate to enhance the contrast and take images of each well while keeping the plates on ice.After photographing each well, take an image of the entire plate with an imaging order label. Open images with ImageJ and use the Multi-point Tool to count the larvae. Larvae can vary in shape, angle and focus.Exclude the shed cuticles, which look like head-only larvae with a little bit of body, or shrunken larvae. Record the results in the spreadsheet. Mosquitoes were injected with double-stranded RNA targeting a candidate iron transporter, FeT, or a control gene, EGFP.Then, they were blood-fed and measured for fecundity and fertility output using the Eagle plate method. Mosquitoes in which iron transporter expression was silenced exhibited a significant reduction in both egg number and hatch rate. FeT-silenced mosquitoes also exhibited delayed excretion and small and light-colored eggs.Taking good pictures is a critical step for this method because the quality of the pictures and quantity of individual eggs or larvae directly affect the quality of the results.

improved-fecundity-fertility-assay-for-aedes-aegypti-using-24-well

Research

JoVE Journal

Biology

Measuring Caenorhabditis elegans Life Span in 96 Well Microtiter Plates

Lifespan is a biological process regulated by several genetic pathways. One strategy to investigate the biology of aging is to study animals that harbor mutations in components of age-regulatory pathways. If these mutations perturb the function of the age-regulatory pathway and therefore alter the lifespan of the entire organism, they provide important mechanistic insights1-3.
Another strategy to investigate the regulation of lifespan is to use small molecules to perturb age-regulatory pathways. To date, a number of molecules are known to extend lifespan in various model organisms and are used as tools to study the biology of aging4-16. The number of molecules identified thus far is small compared to the genetic "toolset" that is available to study the biology of aging.
Caenorhabditis elegans is one of the principle models used to study aging because of its excellent genetics and short lifespan of three weeks. More recently, C.elegans has emerged as a model organism for phenotype based drug screens5,7,16-20 because of its small size and its ability to grow in microtiter plates.
Here we present an assay to measure C.elegans lifespan in 96 well microtiter plates. The assay was developed and successfully used to screen large libraries for molecules that extend C.elegans lifespan7. The reliability of the assay was evaluated in multiple tests: first, by measuring the lifespan of wild type animals grown at different temperatures; second, by measuring the lifespan of mutants with altered lifespans; third, by measuring changes in lifespan in response to different concentrations of the antidepressant Mirtazepine. Mirtazepine has previously been shown to extend lifespan in C.elegans7. The results of these tests show that the assay is able to replicate previous findings from other assays and is quantitative. The microtiter format also makes this lifespan assay compatible with automated liquid handling systems and allows integration into automated platforms.

Measuring Caenorhabditis elegans Life Span in 96 Well Microtiter Plates

In this protocol we present a method to measure Caenorhabditis elegans lifespan in 96 well microtiter plates.

Lifespan is a biological process regulated by several genetic pathways. One strategy to investigate the biology of aging is to study animals that harbor ...

Ice-Cap: A Method for Growing Arabidopsis and Tomato Plants in 96-well Plates for High-Throughput Genotyping

It is becoming common for plant scientists to develop projects that require the genotyping of large numbers of plants. The first step in any genotyping project is to collect a tissue sample from each individual plant. The traditional approach to this task is to sample plants one-at-a-time. If one wishes to genotype hundreds or thousands of individuals, however, using this strategy results in a significant bottleneck in the genotyping pipeline. The Ice-Cap method that we describe here provides a high-throughput solution to this challenge by allowing one scientist to collect tissue from several thousand seedlings in a single day 1,2. This level of throughput is made possible by the fact that tissue is harvested from plants 96-at-a-time, rather than one-at-a-time.
The Ice-Cap method provides an integrated platform for performing seedling growth, tissue harvest, and DNA extraction. The basis for Ice-Cap is the growth of seedlings in a stacked pair of 96-well plates. The wells of the upper plate contain plugs of agar growth media on which individual seedlings germinate. The roots grow down through the agar media, exit the upper plate through a hole, and pass into a lower plate containing water. To harvest tissue for DNA extraction, the water in the lower plate containing root tissue is rapidly frozen while the seedlings in the upper plate remain at room temperature. The upper plate is then peeled away from the lower plate, yielding one plate with 96 root tissue samples frozen in ice and one plate with 96 viable seedlings. The technique is named "Ice-Cap" because it uses ice to capture the root tissue. The 96-well plate containing the seedlings can then wrapped in foil and transferred to low temperature. This process suspends further growth of the seedlings, but does not affect their viability. Once genotype analysis has been completed, seedlings with the desired genotype can be transferred from the 96-well plate to soil for further propagation. We have demonstrated the utility of the Ice-Cap method using Arabidopsis thaliana, tomato, and rice seedlings. We expect that the method should also be applicable to other species of plants with seeds small enough to fit into the wells of 96-well plates.

Ice-Cap: A Method for Growing Arabidopsis and Tomato Plants in 96-well Plates for High-Throughput Genotyping

The Ice-Cap method allows one to grow plants in 96-well plates and non-destructively harvest root tissue from each seedling. DNA extracted from this root tissue can be used for genotyping reactions. We have found that Ice-Cap works well for Arabidopsis thaliana, tomato, and rice seedlings.

It is becoming common for plant scientists to develop projects that require the genotyping of large numbers of plants. The first step in any genotyping ...

RNAi-mediated Gene Knockdown and In Vivo Diuresis Assay in Adult Female Aedes aegypti Mosquitoes

This video protocol demonstrates an effective technique to knockdown a particular gene in an insect and conduct a novel bioassay to measure excretion rate. This method can be used to obtain a better understanding of the process of diuresis in insects and is especially useful in the study of diuresis in blood-feeding arthropods that are able to take up huge amounts of liquid in a single blood meal. 
This RNAi-mediated gene knockdown combined with an in vivo diuresis assay was developed by the Hansen lab to study the effects of RNAi-mediated knockdown of aquaporin genes on Aedes aegypti mosquito diuresis1. 
The protocol is setup in two parts: the first demonstration illustrates how to construct a simple mosquito injection device and how to prepare and inject dsRNA into the thorax of mosquitoes for RNAi-mediated gene knockdown. The second demonstration illustrates how to determine excretion rates in mosquitoes using an in vivo bioassay.

RNAi-mediated Gene Knockdown and In Vivo Diuresis Assay in Adult Female Aedes aegypti Mosquitoes

In this protocol we combine RNAi-mediated gene silencing with an in vivo diuresis assay to study the effects knockdown of genes of interest has on mosquito fluid excretion.

This video protocol demonstrates an effective technique to knockdown a particular gene in an insect and conduct a novel bioassay to measure excretion ...

Physiological Recordings and RNA Sequencing of the Gustatory Appendages of the Yellow-fever Mosquito Aedes aegypti

Electrophysiological recording of action potentials from sensory neurons of mosquitoes provides investigators a glimpse into the chemical perception of these disease vectors. We have recently identified a bitter sensing neuron in the labellum of female Aedes aegypti that responds to DEET and other repellents, as well as bitter quinine, through direct electrophysiological investigation. These gustatory receptor neuron responses prompted our sequencing of total mRNA from both male and female labella and tarsi samples to elucidate the putative chemoreception genes expressed in these contact chemoreception tissues. Samples of tarsi were divided into pro-, meso- and metathoracic subtypes for both sexes. We then validated our dataset by conducting qRT-PCR on the same tissue samples and used statistical methods to compare results between the two methods. Studies addressing molecular function may now target specific genes to determine those involved in repellent perception by mosquitoes. These receptor pathways may be used to screen novel repellents towards disruption of host-seeking behavior to curb the spread of harmful viruses.

Physiological Recordings and RNA Sequencing of the Gustatory Appendages of the Yellow-fever Mosquito Aedes aegypti

Using two methods to estimate gene expression in the major gustatory appendages of Aedes aegypti, we have identified the set of genes putatively underlying the neuronal responses to bitter and repulsive compounds, as determined by electrophysiological examination.

Electrophysiological recording of action potentials from sensory neurons of mosquitoes provides investigators a glimpse into the chemical perception of ...

Measuring Oxidative Stress Resistance of Caenorhabditis elegans in 96-well Microtiter Plates

Oxidative stress, which is the result of an imbalance between production and detoxification of reactive oxygen species, is a major contributor to chronic human disorders, including cardiovascular and neurodegenerative diseases, diabetes, aging, and cancer. Therefore, it is important to study oxidative stress not only in cell systems but also using whole organisms. C. elegans is an attractive model organism to study the genetics of oxidative stress signal transduction pathways, which are highly evolutionarily conserved.
Here, we provide a protocol to measure oxidative stress resistance in C. elegans in liquid. Briefly, ROS-inducing reagents such as paraquat (PQ) and H2O2 are dissolved in M9 buffer, and solutions are aliquoted in the wells of a 96 well microtiter plate. Synchronized L4/young adult C. elegans animals are transferred to the wells (5-8 animals/well) and survival is measured every hour until most worms are dead. When performing an oxidative stress resistance assay using a low concentration of stressors in plates, aging might influence the behavior of animals upon oxidative stress, which could lead to an incorrect interpretation of the data. However, in the assay described herein, this problem is unlikely to occur since only L4/young adult animals are being used. Moreover, this protocol is inexpensive and results are obtained in one day, which renders this technique attractive for genetic screens. Overall, this will help to understand oxidative stress signal transduction pathways, which could be translated into better characterization of oxidative stress-associated human disorders.

Measuring Oxidative Stress Resistance of Caenorhabditis elegans in 96-well Microtiter Plates

C. elegans is an attractive model organism to study signal transduction pathways involved in oxidative stress resistance. Here we provide a protocol to measure oxidative stress resistance of C. elegans animals in liquid phase, using several oxidizing agents in 96 well plates.

Oxidative stress, which is the result of an imbalance between production and detoxification of reactive oxygen species, is a major contributor to chronic ...

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 ...

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Aedes aegypti mosquitoes experimentally infected with Wolbachia are being utilized in programs to control the spread of arboviruses such as dengue, chikungunya and Zika. Wolbachia-infected mosquitoes can be released into the field to either reduce population sizes through incompatible matings or to transform populations with mosquitoes that are refractory to virus transmission. For these strategies to succeed, the mosquitoes released into the field from the laboratory must be competitive with native mosquitoes. However, maintaining mosquitoes in the laboratory can result in inbreeding, genetic drift and laboratory adaptation which can reduce their fitness in the field and may confound the results of experiments. To test the suitability of different Wolbachia infections for deployment in the field, it is necessary to maintain mosquitoes in a controlled laboratory environment across multiple generations. We describe a simple protocol for maintaining Ae. aegypti mosquitoes in the laboratory, which is suitable for both Wolbachia-infected and wild-type mosquitoes. The methods minimize laboratory adaptation and implement outcrossing to increase the relevance of experiments to field mosquitoes. Additionally, colonies are maintained under optimal conditions to maximize their fitness for open field releases.

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Aedes aegypti mosquitoes infected with Wolbachia are being released into natural populations to suppress the transmission of arboviruses. We describe methods to rear Ae. aegypti with Wolbachia infections in the laboratory for experiments and field release, taking precautions to minimize laboratory adaptation and selection.

Aedes aegypti mosquitoes experimentally infected with Wolbachia are being utilized in programs to control the spread of arboviruses such as dengue, ...

Modified Methods for Loading of High-Throughput DNA Extraction Plates Reduce Potential for Contamination

High-throughput DNA sequencing techniques have contributed substantially to advances in our understanding of relationships among microbial communities, host characteristics, and broader ecosystem functions. With this rapid increase in breadth and depth of sequencing capabilities have come methods to extract, amplify, analyze, and interpret environmental DNA successfully with maximum efficiency. Unfortunately, performing DNA extractions quickly can come at the cost of increasing the risk of contamination among samples. In particular, high-throughput extractions that are based on samples contained in a 96-well plate offer a relatively quick method, compared to single-tube extractions, but also increase opportunities for well-to-well cross-contamination. To minimize the risk of cross-contamination among samples, while retaining the benefits of high-throughput extraction techniques, we developed a new method for loading environmental samples into 96-well plates. We used pierceable PCR sealing films to cover each plate while loading samples and added samples first to PCR tubes before moving them into wells; together, these practices reduce the risk of sample drift and unintended double loading of wells. The method outlined in this paper provides researchers with an approach to maximize available high-throughput extraction techniques while reducing the risk of cross-contamination inherent to 96-well plates. We provide a detailed step by step outline of how to move from sample collection to DNA extraction while minimizing the risk of unwanted cross-contamination.

Current methods for loading 96-well plates for DNA extractions can be prone to contamination. We detail a new method for loading 96-well plates that reduces risk of cross-contamination among wells. Our method will help other researchers capitalize on the efficiency of high-throughput DNA extraction techniques and minimize risk of contamination.

High-throughput DNA sequencing techniques have contributed substantially to advances in our understanding of relationships among microbial communities, ...

Preparing Irradiated and Marked Male Aedes aegypti Mosquitoes for Release in an Operational Sterile Insect Technique Program

The control of such human diseases as dengue, Zika, and chikungunya relies on the control of their vector, the Aedes aegypti mosquito, because there is no prevention. Control of mosquito vectors can rely on chemicals applied to the immature and adult stages, which can contribute to the mortality of non-targets and more importantly, lead to insecticide resistance in the vector. The sterile insect technique (SIT) is a method of controlling populations of pests through the release of sterilized adult males that mate with wild females to produce non-viable offspring. This paper describes the process of producing sterile males for use in an operational SIT program for the control of Aedes aegypti mosquitoes. Outlined here are the steps used in the program including rearing and maintaining a colony, separating male and female pupae, irradiating and marking adult males, and shipping Aedes aegypti males to the release site. Also discussed are procedural caveats, program limitations, and future objectives.

Preparing Irradiated and Marked Male Aedes aegypti Mosquitoes for Release in an Operational Sterile Insect Technique Program

The sterile insect technique (SIT) is used to control specific, medically important mosquito populations that may be resistant to chemical controls. Here, we describe a method of mass rearing and preparation of sterile male mosquitoes for release in an operational SIT program targeting the Aedes aegypti mosquito.

The control of such human diseases as dengue, Zika, and chikungunya relies on the control of their vector, the Aedes aegypti mosquito, because there is no ...

Using the Fluorescent Dye, Rhodamine B, to Study Mating Competitiveness in Male Aedes aegypti Mosquitoes

The success of sterile or incompatible insect technique-based population suppression programs depends on the ability of released males to compete for wild-type females and induce sterility in the target population. Hence, laboratory assessment of male mating competitiveness is essential for evaluating the release strain&#8217;s fitness before field release. Conventionally, such an assay is performed by determining the proportion of viable eggs produced by the females after being simultaneously exposed to two sets of males (wild-type and release strains) for copulation. However, this process is time-consuming and laborious due to the need to first blood-feed the females for egg production and then hatch and enumerate the hatched eggs to determine egg viability.&#160;
Moreover, this method cannot discern the degree of competitiveness between two sterile or Wolbachia-infected mosquito lines as wild-type female mosquitoes will only produce non-viable eggs upon mating with both. To circumvent these limitations, this paper describes a more direct method of measuring male mosquito mating competitiveness in laboratory settings using the fluorescent dye, rhodamine B (RhB), which can be used to mark males by feeding them in sucrose solution containing RhB. After the mating assay, the presence of fluorescing sperms in the spermathecae of a female can be used to determine her mating partner. This method is cost-effective, reduces the experimental time by 90% and allows comparison of mating fitness between two sterile or Wolbachia-infected lines.&#160;

Using the Fluorescent Dye, Rhodamine B, to Study Mating Competitiveness in Male Aedes aegypti Mosquitoes

Here, we present a protocol for studying mating competitiveness of male Aedes aegypti using fluorescent dye as a marker. Female mosquitoes are exposed to both marked and unmarked males for copulation. Post mating, their spermathecae are examined under a fluorescence microscope to determine their mating partner.

The success of sterile or incompatible insect technique-based population suppression programs depends on the ability of released males to compete for ...