Summary

实验和生物信息学议定书光周期滞育的亚洲虎蚊的RNA序列分析,<em>白纹伊蚊</em

Published: November 30, 2014
doi:

Summary

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

Abstract

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

Introduction

Rapid advances in next-generation sequencing (NGS) technologies are providing exciting opportunities to probe the molecular underpinnings of a wide range of genetically complex ecological adaptations in a broad diversity of non-model organisms13. This approach is extremely powerful because it establishes a basis for population and functional genomics studies of organisms with an especially interesting and/or well-described ecology or evolutionary history, as well as organisms of practical concern, such as agricultural pests and disease vectors. Thus, NGS technologies are leading to rapid advances in the fields of ecology and have the potential to address problems such as understanding the mechanistic bases of biological responses to rapid contemporary climate change4, the spread of invasive species5, and host-pathogen interactions6,7.

The extraordinary potential of NGS technologies for addressing basic and applied questions in ecology and evolutionary biology is in part due to the fact that these approaches can be applied to any organism at a moderate cost that is feasible for most research laboratories. Furthermore, these approaches provide genome-wide information without the requirement of a priori genetic resources such as a microarray chip or complete genome sequence. Nevertheless, to maximize the productivity of NGS experiments requires careful consideration of experimental design including issues such as the developmental timing and tissue-specificity of RNA sampling. Furthermore, the technical skills required to analyze the massive amounts of data produced by these experiments, often up to several hundred million DNA sequence reads, has been a particular challenge and has limited the widespread implementation of NGS approaches.

Recent RNA-Seq studies on the transcriptional bases of diapause in the invasive and medically important mosquito Aedes albopictus provide a useful example of some of the experimental protocols that can be employed to successfully apply NGS technology to studying the molecular basis of a complex ecological adaptation in a non-model organism810. A. albopictus is a highly invasive species that is native to Asia but has recently invaded North America, South America, Europe, and Africa11,12. Like many temperate insects, temperate populations of A. albopictus survive through winter by entering a type of dormancy referred to as photoperiodic diapause. In A. albopictus, exposure of pupal and adult females to short (autumnal) day lengths leads to the production of diapause eggs in which embryological development is completed, but the pharate larva inside the chorion of the egg enters a developmental arrest that renders the egg refractory to hatching stimulus1517. Diapause eggs are more desiccation resistant5,18 and contain more total lipids19 than non-diapause eggs. Photoperiodic diapause in A. albopictus is thus a maternally controlled, adaptive phenotypic plasticity that is essential for surviving the harsh conditions of winter in temperate environments. Despite the well-understood ecological significance of photoperiodic diapause in a wide range of insects20,21, the molecular basis of this crucial adaptation is not well characterized in any insect22. In organisms such as A. albopictus that undergo an embryonic diapause at the pharate larval stage, it remains a particularly compelling challenge to understand how the photoperiodic signal received by the mother is passed to the offspring and persists through the course of embryonic development to cause arrest at the pharate larval stage.

This protocol describes mosquito rearing, experimental design and bioinformatics analyses for NGS experiments (transcriptome sequencing) performed to elucidate transcriptional components of photoperiodic diapause in A. albopictus. This protocol can be used for additional studies of diapause in A. albopictus, can be adapted to investigate diapause in other closely related species such as other aedine mosquitoes that undergo egg diapause23, and is also more generally relevant to employing NGS approaches to study the transcriptional bases of any complex adaptation in any insect.

Protocol

两个A. 1.苗种培育白纹伊蚊组以共创成长设置两个光周期柜带有可编程照明在21℃为最佳滞育表达16和大约80%的相对湿度。 计划一个机柜为16L:8D光:暗周期(非滞育诱导LD光周期)。设置第二个柜的8L:16D光:暗周期(滞育诱导)13。 程序“灯”在同一时间在两个机柜来同步光周期之间的昼夜时间。 计算来执行实验所需的蛋的数量?…

Representative Results

两个有代表性的RNA样品荧光显示两个频段约2000新台币( 图1A,B)。昆虫28S核糖体RNA是由通过氢键,这很容易被简单加热或扰乱氢键35代理人打乱在一起举行了两次多核苷酸链。将所得的两组件是大致相同的尺寸的18S核糖体RNA。第二RNA样品显示出高程度的退化( 图1B)。 光周期处理一组有代表性A.的伊蚊蚊子导致高滞育发病饲养?…

Discussion

该协议提出的方法来发现,由于差异表达基因在光周期诱导A.白纹伊蚊 。该协议是在于其独特地结合蚊子饲养和生物信息学技术,使访问新手分子生理学方案的所有实验方面显著 – 特别是对那些集中在光周期滞育反应。现有的方法,据我们所知,不提供尽可能多的细节,在饲养协议 – 这往往是要找准饲养的错误 – 他们也不提供在饲养阶段,这将使得下游的成功生物信息学分析的实?…

Disclosures

The authors have nothing to disclose.

Acknowledgements

This work was supported by the National Institutes of Health grant 5R21AI081041-02 and Georgetown University.

Materials

Incubator – Model 818 Thermo-Scientific 3751 120V
Controlled environment room Thermax Scientific N/A Walk-in controlled environment room built to custom specifications by Thermax Scientific Products. A larger alternative to an incubator. http://thermmax.com/
Cool Fluorescent bulb Philips 392183 4 Watt
Petri Dish 100mm x 20mm Fisher 08-772-E
Filter Paper 20.5cm Fisher 09-803-6J
9.5L Bucket Plastican Bway Products http://www.bwayproducts.com/sites/portal/plastic-products/plastic-open-head-pails/117
Utility Fabric-Mosquito Netting White Joann 10173292 http://www.joann.com/utility-fabric-mosquito-netting-white/10173292.html
Orthopedic stockings Albahealth 23650-040 product no. 081420
Organic Raisins Newman's Own UPC: 884284040255
Oviposition cups (brown) Fisher Scientific 03-007-52 The product is actually an amber 125 mL bottle that we saw the top off of.
Recycled Paper Towels Seventh Generation 30BPT120
Modular Mates Square Tupperware Set Tupperware http://order.tupperware.com/pls/htprod_www/coe$www.add_items
Glass Grinder Corning Incorporated 7727-2 These Tenbroeck tissue grinders break the eggs and release RNA into the TRI Reagent.
TRI Reagent Sigma Aldrich T9424 Apply 1ml TRI Reagent per 50-100mg of tissue. Caution – this reagent is toxic.
TURBO DNA-free Ambion/Life Technologies AM1907 This kit generates greater yield than traditional DNase treatment followed by phenol/chloroform cleanup, and it is simpler to use.
RNaseZap Ambion/Life Technologies AM9782 Apply liberally on the bench surfaces and any equipment that might be in contact with the RNA samples. The solution is slightly alkaline/corrosive, can cause irritation and is harmful when swallowed.
2100 Bioanalyzer Agilent Technologies G2939AA Place up to 12 RNA samples on one chip.
Hemotek Membrane Feeder Hemotek  5W1 This system  provides 5 feeding stations that can be used simultaneously. Includes PS5 Power Unit and Power cord; 5 FUI Feeders + Meal Reservoirs and O-rings; Plastic Plugs, Hemotek collagen feeding membrane; Temperature setting tool; and Plug extracting tool. The company's mailing address is: Hemotek Ltd; Unit 5 Union Court; Alan Ramsbottom Way; Great Harwood; Lancashire, UK; BB6 7FD; tel: +44 1254 889 307.
Digital Thermometer and Probe Hemotek  MT3KFU MicroT3 thermometer and KFU probe. This is used to set the temperature of each FUI feeding unit.
Chicken Whole Blood, non-sterile with Sodium Citrate Pel-Freez Biologicals 33130-1 The 500 ml of blood were frozen and stored in 20 ml aliquots at -80 degrees C for up to 1 year.  Thaw blood at room temperature for at least 1 h before using.

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Cite This Article
Poelchau, M. F., Huang, X., Goff, A., Reynolds, J., Armbruster, P. An Experimental and Bioinformatics Protocol for RNA-seq Analyses of Photoperiodic Diapause in the Asian Tiger Mosquito, Aedes albopictus. J. Vis. Exp. (93), e51961, doi:10.3791/51961 (2014).

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