Caenorhabditis elegans as an Emerging Model for Virus-Host Interactions

ABSTRACT Since 1999, Caenorhabditis elegans has been extensively used to study microbe-host interactions due to its simple culture, genetic tractability, and susceptibility to numerous bacterial and fungal pathogens. In contrast, virus studies have been hampered by a lack of convenient virus infection models in nematodes. The recent discovery of a natural viral pathogen of C. elegans and development of diverse artificial infection models are providing new opportunities to explore virus-host interplay in this powerful model organism.

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The Dietary Restriction-Like Genedrl-1, Which Encodes a Putative Serine/Threonine Kinase, Is Essential for Orsay Virus Infection inCaenorhabditis elegans

Journal of Virology ◽

10.1128/jvi.01400-18 ◽

2018 ◽

Vol 93 (3) ◽

Author(s):

Luis Enrique Sandoval ◽

Hongbing Jiang ◽

David Wang

Keyword(s):

Caenorhabditis Elegans ◽

Virus Infection ◽

Dietary Restriction ◽

Model Organism ◽

Serine Threonine Kinase ◽

Content Type ◽

Host Interactions ◽

Threonine Kinase ◽

Orsay Virus ◽

Natural Virus

ABSTRACTOrsay virus is the only known natural virus pathogen ofCaenorhabditis elegans, and its discovery has enabled virus-host interaction studies in this model organism. Host genes required for viral infection remain understudied. We previously established a forward genetic screen based on a virus-inducible green fluorescent protein transcriptional reporter to identify novel host factors essential for virus infection. Here, we report the essential role in Orsay virus infection of the dietary restriction-like (drl-1) gene, which encodes a serine/threonine kinase similar to the mammalian MEKK3 kinase. Ablation ofdrl-1led to a >10,000-fold reduction in Orsay virus RNA levels, which could be rescued by ectopic expression of DRL-1. DRL-1 was dispensable for Orsay replication from an endogenous transgene replicon, suggesting that DRL-1 affects a prereplication stage of the Orsay life cycle. Thus, this study demonstrates the power ofC. elegansas a model to identify novel virus-host interactions essential for virus infection.IMPORTANCEThe recent discovery of Orsay virus, the only known natural virus ofCaenorhabditis elegans, provides a unique opportunity to study virus-host interactions that mediate infection in a genetically tractable multicellular model organism. As viruses remain a global threat to human health, better insights into cellular components that enable virus infection and replication can ultimately lead to the development of new targets for antiviral therapeutics.

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An Evolutionarily Conserved Pathway Essential for Orsay Virus Infection of Caenorhabditis elegans

mBio ◽

10.1128/mbio.00940-17 ◽

2017 ◽

Vol 8 (5) ◽

Cited By ~ 13

Author(s):

Hongbing Jiang ◽

Kevin Chen ◽

Luis E. Sandoval ◽

Christian Leung ◽

David Wang

Keyword(s):

Caenorhabditis Elegans ◽

Virus Infection ◽

Tyrosine Kinase ◽

Model Organism ◽

Wiskott Aldrich Syndrome ◽

C Elegans ◽

Evolutionarily Conserved ◽

Conserved Genes ◽

Orsay Virus ◽

Syndrome Protein

ABSTRACT Many fundamental biological discoveries have been made in Caenorhabditis elegans. The discovery of Orsay virus has enabled studies of host-virus interactions in this model organism. To identify host factors critical for Orsay virus infection, we designed a forward genetic screen that utilizes a virally induced green fluorescent protein (GFP) reporter. Following chemical mutagenesis, two Viro (virus induced reporter off) mutants that failed to express GFP were mapped to sid-3, a nonreceptor tyrosine kinase, and B0280.13 (renamed viro-2), an ortholog of human Wiskott-Aldrich syndrome protein (WASP). Both mutants yielded Orsay virus RNA levels comparable to that of the residual input virus, suggesting that they are not permissive for Orsay virus replication. In addition, we demonstrated that both genes affect an early prereplication stage of Orsay virus infection. Furthermore, it is known that the human ortholog of SID-3, activated CDC42-associated kinase (ACK1/TNK2), is capable of phosphorylating human WASP, suggesting that VIRO-2 may be a substrate for SID-3 in C. elegans. A targeted RNA interference (RNAi) knockdown screen further identified the C. elegans gene nck-1, which has a human ortholog that interacts with TNK2 and WASP, as required for Orsay virus infection. Thus, genetic screening in C. elegans identified critical roles in virus infection for evolutionarily conserved genes in a known human pathway. IMPORTANCE Orsay virus is the only known virus capable of naturally infecting the model organism Caenorhabditis elegans, which shares many evolutionarily conserved genes with humans. We exploited the robust genetic tractability of C. elegans to identify three host genes, sid-3, viro-2, and nck-1, which are essential for Orsay virus infection. Mutant animals that lack these three genes are highly defective in viral replication. Strikingly, the human orthologs of these three genes, activated CDC42-associated kinase (TNK2), Wiskott-Aldrich syndrome protein (WASP), and noncatalytic region of tyrosine kinase adaptor protein 1 (NCK1) are part of a known signaling pathway in mammals. These results suggest that TNK2, WASP, and NCK1 may play important roles in mammalian virus infection. IMPORTANCE Orsay virus is the only known virus capable of naturally infecting the model organism Caenorhabditis elegans, which shares many evolutionarily conserved genes with humans. We exploited the robust genetic tractability of C. elegans to identify three host genes, sid-3, viro-2, and nck-1, which are essential for Orsay virus infection. Mutant animals that lack these three genes are highly defective in viral replication. Strikingly, the human orthologs of these three genes, activated CDC42-associated kinase (TNK2), Wiskott-Aldrich syndrome protein (WASP), and noncatalytic region of tyrosine kinase adaptor protein 1 (NCK1) are part of a known signaling pathway in mammals. These results suggest that TNK2, WASP, and NCK1 may play important roles in mammalian virus infection.

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Punctuated loci on chromosome IV determine natural variation in Orsay virus susceptibility of Caenorhabditis elegans strains Bristol N2 and Hawaiian CB4856

Journal of Virology ◽

10.1128/jvi.02430-20 ◽

2021 ◽

Author(s):

Mark G. Sterken ◽

Lisa van Sluijs ◽

Yiru A. Wang ◽

Wannisa Ritmahan ◽

Mitra L. Gultom ◽

...

Keyword(s):

Genetic Variation ◽

Caenorhabditis Elegans ◽

Virus Infection ◽

Genetic Architecture ◽

Recombinant Inbred Lines ◽

Model Organism ◽

C Elegans ◽

Viral Susceptibility ◽

Orsay Virus ◽

Insight Into

Host-pathogen interactions play a major role in evolutionary selection and shape natural genetic variation. The genetically distinct Caenorhabditis elegans strains, Bristol N2 and Hawaiian CB4856, are differentially susceptible to the Orsay virus (OrV). Here we report the dissection of the genetic architecture of susceptibility to OrV infection. We compare OrV infection in the relatively resistant wild-type CB4856 strain to the more susceptible canonical N2 strain. To gain insight into the genetic architecture of viral susceptibility, 52 fully sequenced recombinant inbred lines (CB4856 x N2 RILs) were exposed to OrV. This led to the identification of two loci on chromosome IV associated with OrV resistance. To verify the two loci and gain additional insight into the genetic architecture controlling virus infection, introgression lines (ILs) that together cover chromosome IV, were exposed to OrV. Of the 27 ILs used, 17 had an CB4856 introgression in an N2 background and 10 had an N2 introgression in a CB4856 background. Infection of the ILs confirmed and fine-mapped the locus underlying variation in OrV susceptibility and we found that a single nucleotide polymorphism in cul-6 may contribute to the difference in OrV susceptibility between N2 and CB4856. An allele swap experiment showed the strain CB4856 became as susceptible as the N2 strain by having an N2 cul-6 allele, although having the CB4856 cul-6 allele did not increase resistance in N2. Additionally, we found that multiple strains with non-overlapping introgressions showed a distinct infection phenotype from the parental strain, indicating that there are punctuated locations on chromosome IV determining OrV susceptibility. Thus, our findings reveal the genetic complexity of OrV susceptibility in C. elegans and suggest that viral susceptibility is governed by multiple genes. Importance Genetic variation determines the viral susceptibility of hosts. Yet, pinpointing which genetic variants determine viral susceptibility remains challenging. Here, we have exploited the genetic tractability of the model organism C. elegans to dissect the genetic architecture of Orsay virus infection. Our results provide novel insight into natural determinants of Orsay virus infection.

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Take a Walk to the Wild Side of Caenorhabditis elegans-Pathogen Interactions

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.00146-20 ◽

2021 ◽

Vol 85 (2) ◽

Author(s):

Leah J. Radeke ◽

Michael A. Herman

Keyword(s):

Innate Immunity ◽

Caenorhabditis Elegans ◽

Recent Work ◽

Genetic Model ◽

Model Organism ◽

Bacterial Pathogen ◽

Content Type ◽

Microbiome Composition ◽

C Elegans ◽

Functional Studies

SUMMARY Microbiomes form intimate functional associations with their hosts. Much has been learned from correlating changes in microbiome composition to host organismal functions. However, in-depth functional studies require the manipulation of microbiome composition coupled with the precise interrogation of organismal physiology—features available in few host study systems. Caenorhabditis elegans has proven to be an excellent genetic model organism to study innate immunity and, more recently, microbiome interactions. The study of C. elegans-pathogen interactions has provided in depth understanding of innate immune pathways, many of which are conserved in other animals. However, many bacteria were chosen for these studies because of their convenience in the lab setting or their implication in human health rather than their native interactions with C. elegans. In their natural environment, C. elegans feed on a variety of bacteria found in rotting organic matter, such as rotting fruits, flowers, and stems. Recent work has begun to characterize the native microbiome and has identified a common set of bacteria found in the microbiome of C. elegans. While some of these bacteria are beneficial to C. elegans health, others are detrimental, leading to a complex, multifaceted understanding of bacterium-nematode interactions. Current research on nematode-bacterium interactions is focused on these native microbiome components, both their interactions with each other and with C. elegans. We will summarize our knowledge of bacterial pathogen-host interactions in C. elegans, as well as recent work on the native microbiome, and explore the incorporation of these bacterium-nematode interactions into studies of innate immunity and pathogenesis.

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Caenorhabditis elegans, a Model Organism for Investigating Immunity

Applied and Environmental Microbiology ◽

10.1128/aem.07486-11 ◽

2012 ◽

Vol 78 (7) ◽

pp. 2075-2081 ◽

Cited By ~ 86

Author(s):

Elizabeth K. Marsh ◽

Robin C. May

Keyword(s):

Caenorhabditis Elegans ◽

Viral Infections ◽

Model Organism ◽

Human Pathogens ◽

Microsporidian Parasite ◽

Content Type ◽

C Elegans ◽

Pathogen Virulence ◽

The Past ◽

Animal Hosts

ABSTRACTThe nematodeCaenorhabditis eleganshas been a powerful experimental organism for almost half a century. Over the past 10 years, researchers have begun to exploit the power ofC. elegansto investigate the biology of a number of human pathogens. This work has uncovered mechanisms of host immunity and pathogen virulence that are analogous to those involved during pathogenesis in humans or other animal hosts, as well as novel immunity mechanisms which appear to be unique to the worm. More recently, these investigations have uncovered details of the natural pathogens ofC. elegans, including the description of a novel intracellular microsporidian parasite as well as new nodaviruses, the first identification of viral infections of this nematode. In this review, we consider the application ofC. elegansto human infectious disease research, as well as consider the nematode response to these natural pathogens.

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Pseudomonas brassicacearum Strain DF41 Kills Caenorhabditis elegans through Biofilm-Dependent and Biofilm-Independent Mechanisms

Applied and Environmental Microbiology ◽

10.1128/aem.02199-16 ◽

2016 ◽

Vol 82 (23) ◽

pp. 6889-6898 ◽

Cited By ~ 10

Author(s):

Munmun Nandi ◽

Chrystal Berry ◽

Ann Karen C. Brassinga ◽

Mark F. Belmonte ◽

W. G. Dilantha Fernando ◽

...

Keyword(s):

Caenorhabditis Elegans ◽

Biofilm Formation ◽

Fungal Pathogens ◽

Biocontrol Agent ◽

Regulatory System ◽

Xenorhabdus Nematophila ◽

Content Type ◽

C Elegans ◽

Pathogen Control ◽

Pseudomonas Brassicacearum

ABSTRACTPseudomonas brassicacearumDF41 is a biocontrol agent that suppresses disease caused by the fungal pathogenSclerotinia sclerotiorum. A number of exometabolites are produced by DF41, including the lipopeptide sclerosin, hydrogen cyanide (HCN), and degradative enzymes. The production of these compounds is controlled at both the transcriptional and posttranscriptional levels by quorum sensing (QS) and the Gac two-component regulatory system. In order to be successful, a biocontrol agent must persist in the environment at levels sufficient for pathogen control. Bacterivorous predators, including nematodes, represent a challenge to the establishment of introduced microorganisms. In the current study, DF41 was investigated for its ability to resist predation byCaenorhabditis elegans. We discovered that this bacterium is capable of killingC. elegansthrough two different mechanisms: the first involves exposure to toxic metabolites, and the second entails biofilm formation on the nematode head blocking the buccal cavity. Biofilm formation on nematodes, which has been reported only forYersiniaspp. andXenorhabdus nematophila, is dependent upon the Gac system. Biofilms were not observed when bacteria were grown on NaCl-containing medium or onC. elegansbiofilm-resistant mutants. Coculturing with nematodes led to the increased expression of thepdfRI-rfiAQS genes andhcnA, which is under QS control. HCN was the most nematicidal of the exometabolites, suggesting that this bacterium can respond to predator cues and upregulate expression of toxins accordingly. In summary, DF41 is able to respond to the presence ofC. elegans, and through two distinct mechanisms, it can escape predation.IMPORTANCEPseudomonas brassicacearumDF41 can suppress fungal pathogens through a process known as biocontrol. To be successful, a biocontrol agent must be able to persist in the environment at levels sufficient for pathogen control. Predators, including the nematodeCaenorhabditis elegans, represent a threat to persistence. The aim of the current study was to investigate the DF41-C. elegansinteraction. We discovered that DF41 is able to escape predation through two distinct mechanisms. The first involves exposure to toxic bacterial metabolites, and the second entails the formation of a sticky coating on the nematode head, called a biofilm, which blocks feeding and causes starvation. We report here a pseudomonad forming biofilms on theC. eleganssurface. When grown withC. elegans, DF41 exhibits altered gene expression and metabolite production, indicating that this bacterium can sense the presence of these predators and adjust its physiology accordingly.

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Antiviral RNA Interference against Orsay Virus Is neither Systemic nor Transgenerational in Caenorhabditis elegans

Journal of Virology ◽

10.1128/jvi.03664-14 ◽

2015 ◽

Vol 89 (23) ◽

pp. 12035-12046 ◽

Cited By ~ 26

Author(s):

Alyson Ashe ◽

Peter Sarkies ◽

Jérémie Le Pen ◽

Mélanie Tanguy ◽

Eric A. Miska

Keyword(s):

Caenorhabditis Elegans ◽

Virus Infection ◽

Viral Infection ◽

Rna Virus ◽

Rnai Pathway ◽

Content Type ◽

C Elegans ◽

Systemic Rnai ◽

Endogenous Role ◽

Orsay Virus

ABSTRACTAntiviral RNA-mediated silencing (RNA interference [RNAi]) acts as a powerful innate immunity defense in plants, invertebrates, and mammals. InCaenorhabditis elegans, RNAi is systemic; i.e., RNAi silencing signals can move between cells and tissues. Furthermore, RNAi effects can be inherited transgenerationally and may last for many generations. Neither the biological relevance of systemic RNAi nor transgenerational RNAi is currently understood. Here we examined the role of both pathways in the protection ofC. elegansfrom viral infection. We studied the Orsay virus, a positive-strand RNA virus related toNodaviridaeand the first and only virus known to infectC. elegans. Immunity to Orsay virus infection requires the RNAi pathway. Surprisingly, we found that genes required for systemic or transgenerational RNAi did not have a role in antiviral defense. Furthermore, we found that Orsay virus infection did not elicit a systemic RNAi response even when a target for RNAi was provided by using transgenes. Finally, we show that viral siRNAs, the effectors of RNAi, are not inherited to a level that provides any significant resistance to viral infection in the next generation. We conclude that systemic or transgenerational RNAi does not play a role in the defense against natural Orsay virus infection. Furthermore, our data suggest that there is a qualitative difference between experimental RNAi and antiviral RNAi. Our data are consistent with a model of systemic and transgenerational RNAi that requires a nuclear or germ line component that is lacking in almost all RNA virus infections.IMPORTANCESince its discovery inCaenorhabditis elegans, RNAi has proven a valuable scientific tool in many organisms. InC. elegans, exogenous RNAi spreads throughout the organism and can be passed between generations; however, there has been controversy as to the endogenous role(s) that the RNAi pathway plays. One endogenous role for which spreading both within the infected organism and between generations would be advantageous is a role in viral defense. In plants, antiviral RNAi is systemic and the spread of RNAi between cells provides protection against subsequent viral infection. Here we investigated this by using the only naturally occurring virus known to infectC. elegans, Orsay virus, and surprisingly found that, in contrast to the exogenous RNAi pathway, the antiviral RNAi response targeted against this virus does not spread systemically throughout the organism and cannot be passed between generations. These results suggest that there are differences between the two pathways that remain to be discovered.

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Heat Stress Reduces the Susceptibility of Caenorhabditis elegans to Orsay Virus Infection

Genes ◽

10.3390/genes12081161 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1161

Author(s):

Yuqing Huang ◽

Mark G. Sterken ◽

Koen van Zwet ◽

Lisa van Sluijs ◽

Gorben P. Pijlman ◽

...

Keyword(s):

Heat Stress ◽

Caenorhabditis Elegans ◽

Virus Infection ◽

Intracellular Pathogen ◽

Potential Candidate ◽

Molecular Responses ◽

C Elegans ◽

Pathogen Response ◽

Orsay Virus ◽

Natural Virus

The nematode Caenorhabditis elegans has been a versatile model for understanding the molecular responses to abiotic stress and pathogens. In particular, the response to heat stress and virus infection has been studied in detail. The Orsay virus (OrV) is a natural virus of C. elegans and infection leads to intracellular infection and proteostatic stress, which activates the intracellular pathogen response (IPR). IPR related gene expression is regulated by the genes pals-22 and pals-25, which also control thermotolerance and immunity against other natural pathogens. So far, we have a limited understanding of the molecular responses upon the combined exposure to heat stress and virus infection. We test the hypothesis that the response of C. elegans to OrV infection and heat stress are co-regulated and may affect each other. We conducted a combined heat-stress-virus infection assay and found that after applying heat stress, the susceptibility of C. elegans to OrV was decreased. This difference was found across different wild types of C. elegans. Transcriptome analysis revealed a list of potential candidate genes associated with heat stress and OrV infection. Subsequent mutant screens suggest that pals-22 provides a link between viral response and heat stress, leading to enhanced OrV tolerance of C. elegans after heat stress.

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Behavioral Effects of Volatile Anesthetics in Caenorhabditis elegans

Anesthesiology ◽

10.1097/00000542-199610000-00027 ◽

1996 ◽

Vol 85 (4) ◽

pp. 901-912 ◽

Cited By ~ 38

Author(s):

Michael C. Crowder ◽

Laynie D. Shebester ◽

Tim Schedl

Keyword(s):

Nervous System ◽

Caenorhabditis Elegans ◽

Time Course ◽

Model Organism ◽

Volatile Anesthetic ◽

Volatile Anesthetics ◽

Effective Concentration ◽

Forward Genetics ◽

C Elegans ◽

Median Effective Concentration

Background The nematode Caenorhabditis elegans offers many advantages as a model organism for studying volatile anesthetic actions. It has a simple, well-understood nervous system; it allows the researcher to do forward genetics; and its genome will soon be completely sequenced. C. elegans is immobilized by volatile anesthetics only at high concentrations and with an unusually slow time course. Here other behavioral dysfunctions are considered as anesthetic endpoints in C. elegans. Methods The potency of halothane for disrupting eight different behaviors was determined by logistic regression of concentration and response data. Other volatile anesthetics were also tested for some behaviors. Established protocols were used for behavioral endpoints that, except for pharyngeal pumping, were set as complete disruption of the behavior. Time courses were measured for rapid behaviors. Recovery from exposure to 1 or 4 vol% halothane was determined for mating, chemotaxis, and gross movement. All experiments were performed at 20 to 22 degrees C. Results The median effective concentration values for halothane inhibition of mating (0.30 vol%-0.21 mM), chemotaxis (0.34 vol%-0.24 mM), and coordinated movement (0.32 vol% - 0.23 mM) were similar to the human minimum alveolar concentration (MAC; 0.21 mM). In contrast, halothane produced immobility with a median effective concentration of 3.65 vol% (2.6 mM). Other behaviors had intermediate sensitivities. Halothane's effects reached steady-state in 10 min for all behaviors tested except immobility, which required 2 h. Recovery was complete after exposure to 1 vol% halothane but was significantly reduced after exposure to immobilizing concentrations. Conclusions Volatile anesthetics selectively disrupt C. elegans behavior. The potency, time course, and recovery characteristics of halothane's effects on three behaviors are similar to its anesthetic properties in vertebrates. The affected nervous system molecules may express structural motifs similar to those on vertebrate anesthetic targets.

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Stochastic left–right neuronal asymmetry in Caenorhabditis elegans

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0407 ◽

2016 ◽

Vol 371 (1710) ◽

pp. 20150407 ◽

Cited By ~ 16

Author(s):

Amel Alqadah ◽

Yi-Wen Hsieh ◽

Rui Xiong ◽

Chiou-Fen Chuang

Keyword(s):

Caenorhabditis Elegans ◽

Molecular Mechanisms ◽

Neurological Diseases ◽

Calcium Signalling ◽

Model Organism ◽

Brain Asymmetry ◽

C Elegans ◽

Left And Right ◽

Left Right Asymmetry ◽

Neuronal Asymmetry

Left–right asymmetry in the nervous system is observed across species. Defects in left–right cerebral asymmetry are linked to several neurological diseases, but the molecular mechanisms underlying brain asymmetry in vertebrates are still not very well understood. The Caenorhabditis elegans left and right amphid wing ‘C’ (AWC) olfactory neurons communicate through intercellular calcium signalling in a transient embryonic gap junction neural network to specify two asymmetric subtypes, AWC OFF (default) and AWC ON (induced), in a stochastic manner. Here, we highlight the molecular mechanisms that establish and maintain stochastic AWC asymmetry. As the components of the AWC asymmetry pathway are highly conserved, insights from the model organism C. elegans may provide a window onto how brain asymmetry develops in humans. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’.

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