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McClure CR, Patel R, Hallem EA. Invade or die: behaviours and biochemical mechanisms that drive skin penetration in Strongyloides and other skin-penetrating nematodes. Philos Trans R Soc Lond B Biol Sci 2024; 379:20220434. [PMID: 38008119 PMCID: PMC10676818 DOI: 10.1098/rstb.2022.0434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 04/05/2023] [Indexed: 11/28/2023] Open
Abstract
Skin-penetrating nematodes, including the human threadworm Strongyloides stercoralis and hookworms in the genera Necator and Ancylostoma, are gastrointestinal parasites that are a major cause of neglected tropical disease in low-resource settings worldwide. These parasites infect hosts as soil-dwelling infective larvae that navigate towards hosts using host-emitted sensory cues such as odorants and body heat. Upon host contact, they invade the host by penetrating through the skin. The process of skin penetration is critical for successful parasitism but remains poorly understood and understudied. Here, we review current knowledge of skin-penetration behaviour and its underlying mechanisms in the human parasite S. stercoralis, the closely related rat parasite Strongyloides ratti, and other skin-penetrating nematodes such as hookworms. We also highlight important directions for future investigations into this underexplored process and discuss how recent advances in molecular genetic and genomic tools for Strongyloides species will enable mechanistic investigations of skin penetration and other essential parasitic behaviours in future studies. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.
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Affiliation(s)
- Courtney R. McClure
- Molecular Toxicology Interdepartmental PhD Program, University of California, Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Ruhi Patel
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Elissa A. Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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2
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Cadd LC, Crooks B, Marks NJ, Maule AG, Mousley A, Atkinson LE. The Strongyloides bioassay toolbox: A unique opportunity to accelerate functional biology for nematode parasites. Mol Biochem Parasitol 2022; 252:111526. [PMID: 36240960 DOI: 10.1016/j.molbiopara.2022.111526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 10/04/2022] [Accepted: 10/10/2022] [Indexed: 12/31/2022]
Abstract
Caenorhabditis elegans is a uniquely powerful tool to aid understanding of fundamental nematode biology. While C. elegans boasts an unrivalled array of functional genomics tools and phenotype bioassays the inherent differences between free-living and parasitic nematodes underscores the need to develop these approaches in tractable parasite models. Advances in functional genomics approaches, including RNA interference and CRISPR/Cas9 gene editing, in the parasitic nematodes Strongyloides ratti and Strongyloides stercoralis provide a unique and timely opportunity to probe basic parasite biology and reveal novel anthelmintic targets in species that are both experimentally and therapeutically relevant pathogens. While Strongyloides functional genomics tools have progressed rapidly, the complementary range of bioassays required to elucidate phenotypic outcomes post-functional genomics remain more limited in scope. To adequately support the exploitation of functional genomic pipelines for studies of gene function in Strongyloides a comprehensive set of species- and parasite-specific quantitative bioassays are required to assess nematode behaviours post-genetic manipulation. Here we review the scope of the current Strongyloides bioassay toolbox, how established Strongyloides bioassays have advanced knowledge of parasite biology, opportunities for Strongyloides bioassay development and, the need for investment in tractable model parasite platforms such as Strongyloides to drive the discovery of novel targets for parasite control.
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Affiliation(s)
- Luke C Cadd
- Microbes & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK
| | - Bethany Crooks
- Microbes & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK
| | - Nikki J Marks
- Microbes & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK
| | - Aaron G Maule
- Microbes & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK
| | - Angela Mousley
- Microbes & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK
| | - Louise E Atkinson
- Microbes & Pathogen Biology, The Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK.
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3
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Lillis PE, Kennedy IP, Carolan JC, Griffin CT. Low-temperature exposure has immediate and lasting effects on the stress tolerance, chemotaxis and proteome of entomopathogenic nematodes. Parasitology 2022; 150:1-14. [PMID: 36328953 PMCID: PMC10090647 DOI: 10.1017/s0031182022001445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 10/03/2022] [Accepted: 10/07/2022] [Indexed: 11/07/2022]
Abstract
Temperature is one of the most important factors affecting soil organisms, including the infective stages of parasites and entomopathogenic nematodes, which are important biological control agents. We investigated the response of 2 species of entomopathogenic nematodes to different storage regimes: cold (9°C), culture temperature (20°C) and temperature swapped from 9 to 20°C. For Steinernema carpocapsae, cold storage had profound effects on chemotaxis, stress tolerance and protein expression that were retained in temperature-swapped individuals. These effects included reversal of chemotactic response for 3 (prenol, methyl salicylate and hexanol) of the 4 chemicals tested, and enhanced tolerance to freezing (−10°C) and desiccation (75% RH). Label-free quantitative proteomics showed that cold storage induced widespread changes in S. carpocapsae, including an increase in heat-shock proteins and late embryogenesis abundant proteins. For Heterorhabditis megidis, cold storage had a less dramatic effect on chemotaxis (as previously shown for proteomic expression) and changes were not maintained on return to 20°C. Thus, cold temperature exposure has significant effects on entomopathogenic nematodes, but the nature of the change depends on the species. Steinernema carpocapsae, in particular, displays significant plasticity, and its behaviour and stress tolerance may be manipulated by brief exposure to low temperatures, with implications for its use as a biological control agent.
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Affiliation(s)
- Peter E. Lillis
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
| | - Ian P. Kennedy
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
| | - James C. Carolan
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
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4
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Urbanization impacts parasite diversity in the cane toad Rhinella horribilis (Anura: Bufonidae). Glob Ecol Conserv 2022. [DOI: 10.1016/j.gecco.2022.e02275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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5
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Mendez P, Walsh B, Hallem EA. Using newly optimized genetic tools to probe Strongyloides sensory behaviors. Mol Biochem Parasitol 2022; 250:111491. [PMID: 35697205 PMCID: PMC9339661 DOI: 10.1016/j.molbiopara.2022.111491] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/25/2022] [Accepted: 06/07/2022] [Indexed: 11/26/2022]
Abstract
The oft-neglected human-parasitic threadworm, Strongyloides stercoralis, infects roughly eight percent of the global population, placing disproportionate medical and economic burden upon marginalized communities. While current chemotherapies treat strongyloidiasis, disease recrudescence and the looming threat of anthelminthic resistance necessitate novel strategies for nematode control. Throughout its life cycle, S. stercoralis relies upon sensory cues to aid in environmental navigation and coordinate developmental progression. Odorants, tastants, gases, and temperature have been shown to shape parasite behaviors that drive host seeking and infectivity; however, many of these sensory behaviors remain poorly understood, and their underlying molecular and neural mechanisms are largely uncharacterized. Disruption of sensory circuits essential to parasitism presents a promising strategy for future interventions. In this review, we describe our current understanding of sensory behaviors - namely olfactory, gustatory, gas sensing, and thermosensory behaviors - in Strongyloides spp. We also highlight the ever-growing cache of genetic tools optimized for use in Strongyloides that have facilitated these findings, including transgenesis, CRISPR/Cas9-mediated mutagenesis, RNAi, chemogenetic neuronal silencing, and the use of fluorescent biosensors to measure neuronal activity. Bolstered by these tools, we are poised to enter an era of rapid discovery in Strongyloides sensory neurobiology, which has the potential to shape pioneering advances in the prevention and treatment of strongyloidiasis.
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Affiliation(s)
- Patricia Mendez
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA; Molecular Biology Interdepartmental PhD Program, University of California Los Angeles, Los Angeles, CA, USA.
| | - Breanna Walsh
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA; Molecular Biology Interdepartmental PhD Program, University of California Los Angeles, Los Angeles, CA, USA; Medical Scientist Training Program, University of California, Los Angeles, Los Angeles, CA, USA.
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, USA.
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6
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Soil Nematodes as the Silent Sufferers of Climate-Induced Toxicity: Analysing the Outcomes of Their Interactions with Climatic Stress Factors on Land Cover and Agricultural Production. Appl Biochem Biotechnol 2022; 195:2519-2586. [PMID: 35593954 DOI: 10.1007/s12010-022-03965-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 05/10/2022] [Indexed: 11/02/2022]
Abstract
Unsustainable anthropogenic activities over the last few decades have resulted in alterations of the global climate. It can be perceived through changes in the rainfall patterns and rise in mean annual temperatures. Climatic stress factors exert their effects on soil health mainly by modifying the soil microenvironments where the soil fauna reside. Among the members of soil fauna, the soil nematodes have been found to be sensitive to these stress factors primarily because of their low tolerance limits. Additionally, because of their higher and diverse trophic positions in the soil food web they can integrate the effects of many stress factors acting together. This is important because under natural conditions the climatic stress factors do not exert their effect individually. Rather, they interact amongst themselves and other abiotic stress factors in the soil to generate their impacts. Some of these interactions may be synergistic while others may be antagonistic. As such, it becomes very difficult to assess their impacts on soil health by simply analysing the physicochemical properties of soil. This makes soil nematodes outstanding candidates for studying the effects of climatic stress factors on soil biology. The knowledge obtained therefrom can be used to design sustainable agricultural practices because most of the conventional techniques aim at short-term benefits with complete disregard of soil biology. This can partly ensure food security in the coming decades for the expanding population. Moreover, understanding soil biology can help to preserve landscapes that have developed over long periods of climatic stability and belowground soil biota interactions.
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7
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Filgueiras CC, Willett DS. Non-lethal effects of entomopathogenic nematode infection. Sci Rep 2021; 11:17090. [PMID: 34429457 PMCID: PMC8384869 DOI: 10.1038/s41598-021-96270-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 08/04/2021] [Indexed: 11/10/2022] Open
Abstract
Entomopathogenic nematodes are typically considered lethal parasites of insect hosts. Indeed they are employed as such for biological control of insect pests. The effects of exposure to entomopathogenic nematodes are not strictly limited to mortality, however. Here we explore non-lethal effects of exposure to entomopathogenic nematodes by introducing the relatively non-susceptible pupal stage of Delia antiqua to thirteen different strains. We specifically chose to inoculate the pupal stage because it tends to be more resistant to infection, yet resides in the soil where it could come into contact with EPN biological control agents. We find that there is no significant mortality at the pupal stage, but that there are a host of strain-dependent non-lethal effects during and after the transition to adulthood including altered developmental times and changes in risk of death compared to controls. We also find that exposure to specific strains can reduce risk of mortality. These results emphasize the strain-dependent nature of entomopathogenic nematode infection and highlight the positive and negative ramifications for non-lethal effects for biological control of insect pests. Our work emphasizes the need for strain-specific screening of biological control agents before wide-spread adoption.
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Affiliation(s)
- Camila C Filgueiras
- Natural Enemy Management and Applications (NEMA) Lab, Department of Biology, UNC Asheville, Asheville, USA.
| | - Denis S Willett
- Applied Chemical Ecology Technology (ACET) Lab, Cornell AgriTech, Cornell University, Ithaca, USA
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8
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Bryant AS, DeMarco SF, Hallem EA. Strongyloides RNA-seq Browser: a web-based software platform for on-demand bioinformatics analyses of Strongyloides species. G3 (BETHESDA, MD.) 2021; 11:jkab104. [PMID: 33823530 PMCID: PMC8104939 DOI: 10.1093/g3journal/jkab104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 03/25/2021] [Indexed: 12/03/2022]
Abstract
Soil-transmitted gastrointestinal parasitic nematodes infect approximately 1 billion people worldwide, predominantly in low-resource communities. Skin-penetrating gastrointestinal nematodes in the genus Strongyloides are emerging as model systems for mechanistic studies of soil-transmitted helminths due to the growing availability of functional genomics tools for these species. To facilitate future genomics studies of Strongyloides species, we have designed a web-based application, the Strongyloides RNA-seq Browser, that provides an open source, user-friendly portal for accessing and analyzing Strongyloides genomic expression data. Specifically, the Strongyloides RNA-seq Browser takes advantage of alignment-free read mapping tools and R-based transcriptomics tools to re-analyze publicly available RNA sequencing datasets from four Strongyloides species: Strongyloides stercoralis, Strongyloides ratti, Strongyloides papillosus, and Strongyloides venezuelensis. This application permits on-demand exploration and quantification of gene expression across life stages without requiring previous coding experience. Here, we describe this interactive application and demonstrate how it may be used by nematode researchers to conduct a standard set of bioinformatics queries.
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Affiliation(s)
- Astra S Bryant
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Stephanie F DeMarco
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
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9
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Susceptibility of Drosophila suzukii larvae to the combined administration of the entomopathogens Bacillus thuringiensis and Steinernema carpocapsae. Sci Rep 2021; 11:8149. [PMID: 33854098 PMCID: PMC8046782 DOI: 10.1038/s41598-021-87469-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 03/30/2021] [Indexed: 02/06/2023] Open
Abstract
Non-native pests are often responsible for serious crop damage. Since Drosophila suzukii has invaded North America and Europe, the global production of soft, thin-skinned fruits has suffered severe losses. The control of this dipteran by pesticides, although commonly used, is not recommended because of the negative impact on the environment and human health. A possible alternative is the use of bio-insecticides, including Bacillus thuringiensis and entomopathogenic nematodes, such as Steinernema carpocapsae. These biological control agents have a fair effectiveness when used individually on D. suzukii, but both have limits related to different environmental, methodological, and physiological factors. In this work, we tested various concentrations of B. thuringiensis and S. carpocapsae to evaluate their efficacy on D. suzukii larvae, when administered individually or in combination by using agar traps. In the combined trials, we added the nematodes after 16 h or concurrently to the bacteria, and assessed larvae lethality from 16 to 48 h. The assays demonstrated a higher efficacy of the combined administration, both time-shifted and concurrent; the obtained data also showed a relevant decrease of the time needed to kill the larvae. Particularly, the maximum mortality rate, corresponding to 79% already at 16 h, was observed with the highest concentrations (0.564 µg/mL of B. thuringiensis and 8 × 102 IJs of S. carpocapsae) in the concurrent trials. This study, conducted by laboratory tests under controlled conditions, is a good starting point to develop a further application step through field studies for the control of D. suzukii.
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Zhang X, Li L, Kesner L, Robert CAM. Chemical host-seeking cues of entomopathogenic nematodes. CURRENT OPINION IN INSECT SCIENCE 2021; 44:72-81. [PMID: 33866041 DOI: 10.1016/j.cois.2021.03.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 03/30/2021] [Accepted: 03/31/2021] [Indexed: 06/12/2023]
Abstract
Entomopathogenic nematodes (EPNs) are obligate parasites that infect a broad range of insect species. Host-seeking is a crucial step for EPN infection success and survival. Yet, the identity and ecological functions of chemicals involved in host-seeking by EPNs remain overlooked. In this review, we report known CO2, plant-derived and insect-derived cues shaping EPN host-seeking and recognition. Despite species-specific response to environmental cues, we highlight a hierarchical integration of chemicals by EPNs. We further emphasize the impact of EPN selection pressure, age, and experience on their responsiveness to infochemicals. Finally, we feature that EPN chemical ecology can translate into powerful sustainable strategies to control insect herbivores in agriculture.
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Affiliation(s)
- Xi Zhang
- Key Laboratory of Plant Stress Biology, State Key Laboratory of Cotton Biology, School of Life Sciences, Henan University, Kaifeng 475004, China.
| | - Lu Li
- Key Laboratory of Plant Stress Biology, State Key Laboratory of Cotton Biology, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Lucie Kesner
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Christelle Aurélie Maud Robert
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland; Oeschger Centre for Climate Change Research (OCCR), University of Bern, Falkenplatz 16, 3012 Bern, Switzerland.
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11
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Fanelli E, Troccoli A, Tarasco E, De Luca F. Molecular Characterization and Functional Analysis of the Hb-hsp90-1 Gene in Relation to Temperature Changes in Heterorhabditis bacteriophora. Front Physiol 2021; 12:615653. [PMID: 33732162 PMCID: PMC7959791 DOI: 10.3389/fphys.2021.615653] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 01/26/2021] [Indexed: 12/17/2022] Open
Abstract
Understanding how entomopathogenic nematodes respond to temperature changes and have adapted to the local environment is crucial to improve their potential as biocontrol agents. In order to improve understanding of Heterorhabditis bacteriophora's potential adaptability to future climate changes, full-length cDNA and the corresponding gene of heat shock protein 90 (Hsp90) were isolated and fully characterized. The reproductive potential of the Apulian strain of H. bacteriophora increased when the temperature rose from 23 to 30°C, but no reproduction was found at 12°C. Expression analyses revealed that Hb-hsp90-1 was differentially expressed in Infective Juveniles (IJs) and adults (hermaphrodites, females and males). Up-regulation of Hb-hsp90-1 was higher during the recovery process in Galleria mellonella larvae than adults, thus confirming the protective role of Hb-hsp90-1 in coping with the host environment. Silencing of Hb-hsp90-1 resulted in a significant reduction (76%) in the expression level. Silenced IJs took longer than untreated nematodes to infect G. mellonella, showing that Hb-hsp90-1 could be also involved in chemosensation. Furthermore, the number of adults and IJs recovered from G. mellonella infected with silenced nematodes and incubated at 30°C was higher than that obtained from G. mellonella infected with untreated nematodes. These data confirm the crucial role of Hb-hsp90-1 allowing acclimation to increased temperatures and modulation of the recovery process.
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Affiliation(s)
- Elena Fanelli
- Institute for Sustainable Plant Protection-CNR, Bari, Italy
| | | | - Eustachio Tarasco
- Institute for Sustainable Plant Protection-CNR, Bari, Italy
- Section of Entomology and Zoology, Department of Soil, Plant and Food Sciences, University of Bari “A. Moro”, Bari, Italy
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12
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Baiocchi T, Li C, Dillman AR. EPNs Exhibit Repulsion to Prenol in Pluronic Gel Assays. INSECTS 2020; 11:insects11080457. [PMID: 32707750 PMCID: PMC7468948 DOI: 10.3390/insects11080457] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 07/13/2020] [Accepted: 07/15/2020] [Indexed: 05/25/2023]
Abstract
Entomopathogenic nematodes (EPNs) are lethal parasites of insects that have become valuable in biological control and as a model system for studying host-parasite interactions, behavioral ecology, neurobiology, and genomics, among other fields. Their ability to locate hosts is paramount to successful infection and host seeking has been extensively studied in many species in the lab. Here, we explored the usefulness of pluronic gel as a medium to assess EPN host seeking in the lab by characterizing the response of Steinernema carpocapsae, S. feltiae, S. glaseri, S. riobrave, Heterorhabditis bacteriophora, and H. indica to the odor prenol. We found that the infective juveniles (IJs) of these species were repelled by prenol in pluronic gel. We then evaluated how storing the IJs of S. carpocapsae, S. feltiae, and S. glaseri for different amounts of time affected their behavioral responses to prenol. The response of S. carpocapsae was significantly affected by the storage time, while the responses of S. feltiae and S. glaseri were unaffected. Our data support the notion that pluronic gel is a useful medium for studying EPN behavior and that the response of S. carpocapsae to informative odors is significantly affected by long-term storage.
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Affiliation(s)
- Tiffany Baiocchi
- Department of Nematology, University of California, Riverside, CA 92521, USA;
| | - Chunjie Li
- Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, China;
| | - Adler R. Dillman
- Department of Nematology, University of California, Riverside, CA 92521, USA;
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13
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Chemosensory mechanisms of host seeking and infectivity in skin-penetrating nematodes. Proc Natl Acad Sci U S A 2020; 117:17913-17923. [PMID: 32651273 DOI: 10.1073/pnas.1909710117] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Approximately 800 million people worldwide are infected with one or more species of skin-penetrating nematodes. These parasites persist in the environment as developmentally arrested third-stage infective larvae (iL3s) that navigate toward host-emitted cues, contact host skin, and penetrate the skin. iL3s then reinitiate development inside the host in response to sensory cues, a process called activation. Here, we investigate how chemosensation drives host seeking and activation in skin-penetrating nematodes. We show that the olfactory preferences of iL3s are categorically different from those of free-living adults, which may restrict host seeking to iL3s. The human-parasitic threadworm Strongyloides stercoralis and hookworm Ancylostoma ceylanicum have highly dissimilar olfactory preferences, suggesting that these two species may use distinct strategies to target humans. CRISPR/Cas9-mediated mutagenesis of the S. stercoralis tax-4 gene abolishes iL3 attraction to a host-emitted odorant and prevents activation. Our results suggest an important role for chemosensation in iL3 host seeking and infectivity and provide insight into the molecular mechanisms that underlie these processes.
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14
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Eliáš S, Hurychová J, Toubarro D, Frias J, Kunc M, Dobeš P, Simões N, Hyršl P. Bioactive Excreted/Secreted Products of Entomopathogenic Nematode Heterorhabditis bacteriophora Inhibit the Phenoloxidase Activity during the Infection. INSECTS 2020; 11:insects11060353. [PMID: 32516962 PMCID: PMC7349556 DOI: 10.3390/insects11060353] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/27/2020] [Accepted: 06/03/2020] [Indexed: 12/11/2022]
Abstract
Entomopathogenic nematodes (EPNs) are efficient insect parasites, that are known for their mutualistic relationship with entomopathogenic bacteria and their use in biocontrol. EPNs produce bioactive molecules referred to as excreted/secreted products (ESPs), which have come to the forefront in recent years because of their role in the process of host invasion and the modulation of its immune response. In the present study, we confirmed the production of ESPs in the EPN Heterorhabditis bacteriophora, and investigated their role in the modulation of the phenoloxidase cascade, one of the key components of the insect immune system. ESPs were isolated from 14- and 21-day-old infective juveniles of H. bacteriophora, which were found to be more virulent than newly emerged nematodes, as was confirmed by mortality assays using Galleria mellonella larvae. The isolated ESPs were further purified and screened for the phenoloxidase-inhibiting activity. In these products, a 38 kDa fraction of peptides was identified as the main candidate source of phenoloxidase-inhibiting compounds. This fraction was further analyzed by mass spectrometry and the de novo sequencing approach. Six peptide sequences were identified in this active ESP fraction, including proteins involved in ubiquitination and the regulation of a Toll pathway, for which a role in the regulation of insect immune response has been proposed in previous studies.
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Affiliation(s)
- Sara Eliáš
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic; (S.E.); (J.H.); (M.K.)
| | - Jana Hurychová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic; (S.E.); (J.H.); (M.K.)
| | - Duarte Toubarro
- CBA and Faculty of Sciences and Technology, University of Azores, Rua Mãe de Deus n° 13, 9500-321 Ponta Delgada, Portugal; (D.T.); (J.F.); (N.S.)
| | - Jorge Frias
- CBA and Faculty of Sciences and Technology, University of Azores, Rua Mãe de Deus n° 13, 9500-321 Ponta Delgada, Portugal; (D.T.); (J.F.); (N.S.)
| | - Martin Kunc
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic; (S.E.); (J.H.); (M.K.)
| | - Pavel Dobeš
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic; (S.E.); (J.H.); (M.K.)
- Correspondence: (P.D.); (P.H.); Tel.: +420-549-49-3419 (P.D.); +420-549-49-4510 (P.H.)
| | - Nelson Simões
- CBA and Faculty of Sciences and Technology, University of Azores, Rua Mãe de Deus n° 13, 9500-321 Ponta Delgada, Portugal; (D.T.); (J.F.); (N.S.)
| | - Pavel Hyršl
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic; (S.E.); (J.H.); (M.K.)
- Correspondence: (P.D.); (P.H.); Tel.: +420-549-49-3419 (P.D.); +420-549-49-4510 (P.H.)
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15
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Warnock ND, Cox D, McCoy C, Morris R, Dalzell JJ. Transcriptional variation and divergence of host-finding behaviour in Steinernema carpocapsae infective juveniles. BMC Genomics 2019; 20:884. [PMID: 31752671 PMCID: PMC6868747 DOI: 10.1186/s12864-019-6179-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 10/10/2019] [Indexed: 11/15/2022] Open
Abstract
Background Steinernema carpocapsae is an entomopathogenic nematode that employs nictation and jumping behaviours to find potential insect hosts. Here we aimed to investigate the transcriptional basis of variant host-finding behaviours in the infective juvenile (IJ) stage of three S. carpocapsae strains (ALL, Breton and UK1), with a focus on neuronal genes known to influence behaviour in other nematode species. Identifying gene expression changes that correlate with variant host-finding behaviours will further our understanding of nematode biology. Results RNA-seq analysis revealed that whilst up to 28% of the S. carpocapsae transcriptome was differentially expressed (P < 0.0001) between strains, remarkably few of the most highly differentially expressed genes (> 2 log2 fold change, P < 0.0001) were from neuronal gene families. S. carpocapsae Breton displays increased chemotaxis toward the laboratory host Galleria mellonella, relative to the other strains. This correlates with the up-regulation of four srsx chemosensory GPCR genes, and a sodium transporter gene, asic-2, relative to both ALL and UK1 strains. The UK1 strain exhibits a decreased nictation phenotype relative to ALL and Breton strains, which correlates with co-ordinate up-regulation of neuropeptide like protein 36 (nlp-36), and down-regulation of an srt family GPCR gene, and a distinct asic-2-like sodium channel paralogue. To further investigate the link between transcriptional regulation and behavioural variation, we sequenced microRNAs across IJs of each strain. We have identified 283 high confidence microRNA genes, yielding 321 predicted mature microRNAs in S. carpocapsae, and find that up to 36% of microRNAs are differentially expressed (P < 0.0001) between strains. Many of the most highly differentially expressed microRNAs (> 2 log2 fold, P < 0.0001) are predicted to regulate a variety of neuronal genes that may contribute to variant host-finding behaviours. We have also found evidence for differential gene isoform usage between strains, which alters predicted microRNA interactions, and could contribute to the diversification of behaviour. Conclusions These data provide insight to the transcriptional basis of behavioural variation in S. carpocapsae, supporting efforts to understand the molecular basis of complex behaviours in nematodes.
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Affiliation(s)
- Neil D Warnock
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland
| | - Deborah Cox
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland
| | - Ciaran McCoy
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland
| | - Robert Morris
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland
| | - Johnathan J Dalzell
- School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland.
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16
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Hartley CJ, Lillis PE, Owens RA, Griffin CT. Infective juveniles of entomopathogenic nematodes (Steinernema and Heterorhabditis) secrete ascarosides and respond to interspecific dispersal signals. J Invertebr Pathol 2019; 168:107257. [PMID: 31634473 DOI: 10.1016/j.jip.2019.107257] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/30/2019] [Accepted: 10/08/2019] [Indexed: 01/23/2023]
Abstract
Ascarosides are a modular series of signalling molecules that are widely conserved in nematodes where they function as pheromones with both behavioural and developmental effects. Here we show that the developmentally arrested infective juvenile (IJ) stage of entomopathogenic nematodes (EPN) secrete ascarosides into the surrounding medium. The exometabolome of Steinernema carpocapsae and Heterorhabditis megidis was examined at 0, 1, 7 and 21 days of storage. The concentration of several ascarosides (ascr#11, ascr#9, ascr#12, ascr#1 and ascr#14 for both species, plus ascr#10 for H. megidis) showed a progressive increase over this period, while the concentration of longer chain ascarosides increased up to day 7, with an apparent decline thereafter. Ascr #9 was the main ascaroside produced by both species. Similar ascarosides were found over a 7-day period for Steinernema longicaudum and S. feltiae. Ascaroside blends have previously been shown to promote nematode dispersal. S. carpocapsae and H. megidis IJs were stored for up to 12 weeks and assayed at intervals. IJs where exometabolome was allowed to accumulate showed higher dispersal rates than those where water was changed frequently, indicating that IJ exometabolome maintained high dispersal. Infectivity was not affected. IJ exometabolome accumulated over 7 days promoted dispersal of freshly harvested IJs, both of their own and other EPN species. Similarly, extracts of nematode-infected cadavers promoted dispersal of con- and heterospecific IJs. Thus, IJs are encouraged to disperse from a source cadaver or from other crowded conditions by public information cues, a finding that may have application in enhancing biocontrol. However, the complexity of the ascaroside blend produced by IJs suggests that it may have ecological functions other than dispersal.
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Affiliation(s)
- Cathryn J Hartley
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
| | - Peter E Lillis
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
| | - Rebecca A Owens
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland
| | - Christine T Griffin
- Department of Biology, Maynooth University, Maynooth, County Kildare, Ireland.
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17
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Abstract
Carbon dioxide (CO2) is an important sensory cue for many animals, including both parasitic and free-living nematodes. Many nematodes show context-dependent, experience-dependent and/or life-stage-dependent behavioural responses to CO2, suggesting that CO2 plays crucial roles throughout the nematode life cycle in multiple ethological contexts. Nematodes also show a wide range of physiological responses to CO2. Here, we review the diverse responses of parasitic and free-living nematodes to CO2. We also discuss the molecular, cellular and neural circuit mechanisms that mediate CO2 detection in nematodes, and that drive context-dependent and experience-dependent responses of nematodes to CO2.
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18
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Abstract
Purpose of Review This paper constitutes an update of recent studies on the general biology, molecular genetics, and cellular biology of Strongyloides spp. and related parasitic nematodes. Recent Findings Increasingly, human strongyloidiasis is considered the most neglected of neglected tropical diseases. Despite this, the last 5 years has seen remarkable advances in the molecular biology of Strongyloides spp. Genome sequences for S. stercoralis, S. ratti, S. venezuelensis, S. papillosus, and the related parasite Parastrongyloides trichosuri were created, annotated, and analyzed. These genomic resources, along with a practical transgenesis platform for Strongyloides spp., aided a major achievement, the advent of targeted mutagenesis via CRISPR/Cas9 in S. stercoralis and S. ratti. The genome sequences have also enabled significant molecular epidemiologic and phylogenetic findings on human strongyloidiasis, including the first genetic evidence of zoonotic transmission of S. stercoralis between dogs and humans. Studies of molecular signaling pathways identified the nuclear receptor Ss-DAF-12 as one that can be manipulated in the parasite by exogenous application of its steroid ligands. The chemotherapeutic implications of this were unscored by a study in which a Ss-DAF-12 ligand suppressed autoinfection by S. stercoralis in a new murine model of human strongyloidiasis. Summary Seminal advances in genomics of Strongyloides spp. have transformed research into strongyloidiasis, facilitating fundamental phylogenetic and epidemiologic studies and aiding the deployment of CRISPR/Cas9 gene disruption and editing as functional genomic tools in Strongyloides spp. Studies of Ss-DAF-12 signaling in S. stercoralis demonstrated the potential of this pathway as a novel chemotherapeutic target in parasitic nematodes.
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Affiliation(s)
- Tegegn G. Jaleta
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - James B. Lok
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
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19
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Kin K, Baiocchi T, Dillman AR. Dispersal and Repulsion of Entomopathogenic Nematodes to Prenol. BIOLOGY 2019; 8:biology8030058. [PMID: 31382480 PMCID: PMC6783912 DOI: 10.3390/biology8030058] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 07/31/2019] [Accepted: 08/01/2019] [Indexed: 12/02/2022]
Abstract
Chemosensory cues are crucial for entomopathogenic nematodes (EPNs)—a guild of insect-killing parasitic nematodes that are used as biological control agents against a variety of agricultural pests. Dispersal is an essential element of the EPN life cycle in which newly developed infective juveniles (IJs) emerge and migrate away from a resource-depleted insect cadaver in order to search for new hosts. Emergence and dispersal are complex processes that involve biotic and abiotic factors, however, the elements that result in EPN dispersal behaviors have not been well-studied. Prenol is a simple isoprenoid and a natural alcohol found in association with EPN-infected, resource-depleted insect cadavers, and this odorant has been speculated to play a role in dispersal behavior in EPNs. This hypothesis was tested by evaluating the behavioral responses of five different species of EPNs to prenol both as a distal-chemotactic cue and as a dispersal cue. The results indicate that prenol acted as a repulsive agent for all five species tested, while only two species responded to prenol as a dispersal cue.
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Affiliation(s)
- Kassandra Kin
- Department of Nematology, University of California Riverside, Riverside, CA 92521, USA
| | - Tiffany Baiocchi
- Department of Nematology, University of California Riverside, Riverside, CA 92521, USA
| | - Adler R Dillman
- Department of Nematology, University of California Riverside, Riverside, CA 92521, USA.
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20
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Wu Y, Wickham JD, Zhao L, Sun J. CO2 drives the pine wood nematode off its insect vector. Curr Biol 2019; 29:R619-R620. [DOI: 10.1016/j.cub.2019.05.033] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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21
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Li C, Zhou X, Lewis EE, Yu Y, Wang C. Study on host-seeking behavior and chemotaxis of entomopathogenic nematodes using Pluronic F-127 gel. J Invertebr Pathol 2019; 161:54-60. [PMID: 30707919 DOI: 10.1016/j.jip.2019.01.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 12/31/2018] [Accepted: 01/26/2019] [Indexed: 10/27/2022]
Abstract
Pluronic F-127 gel (PF127) has proven to be a powerful medium in which to study host-finding behavior and chemotaxis for plant-parasitic nematodes. Pluronic gel can also be used to study host-habitat seeking behavior of entomopathogenic nematodes (EPN), which are natural enemies of root-feeding insect pests. In this study, PF127 was used to study tritrophic interactions among EPNs, host-habitat roots and insects. We also tested whether EPN aggregated to acetic acid (pH gradient) which mimicked the conditions near the roots. The chive root gnat Bradysia odoriphaga alone significantly attracted more nematodes than chive roots alone or the combination of roots plus insects. The attractiveness of B. odoriphaga differed (3.7-15.4%) among all tested species/strains of EPNs. In addition, we found that Heterorhabditis spp. and Steinernema spp. infective juveniles responded to pH gradients formed by acetic acid in Pluronic gel. The preferred pH ranges for strains of H. bacteriophora and H. megidis were from 4.32-5.04, and from 5.37-6.92 for Steinernema species, indicating that Heterorhabditis spp. prefer low pH conditions than Steinernema species. A narrow pH gradient between 6.84 and 7.05 was detected around chive root tips in which EPN was attracted. These results suggest that Pluronic gel can be broadly used for the study of host or host-habitat seeking behaviors and chemotaxis of nematodes.
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Affiliation(s)
- Chunjie Li
- Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, China
| | - Xianhong Zhou
- Shandong Key Laboratory of Plant Virology, Institute of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan 250100, China
| | - Edwin E Lewis
- Department of Entomology, Plant Pathology and Nematology, University of Idaho, Moscow, ID 83844, USA
| | - Yi Yu
- Shandong Key Laboratory of Plant Virology, Institute of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan 250100, China.
| | - Congli Wang
- Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, China.
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22
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Baiocchi T, Braun L, Dillman AR. Touch-stimulation increases host-seeking behavior in Steinernema Carpocapsae. J Nematol 2019; 51:1-5. [PMID: 31814369 PMCID: PMC6909391 DOI: 10.21307/jofnem-2019-067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Indexed: 11/20/2022] Open
Abstract
Previous research demonstrated that Steinernema carpocapsae infective juveniles (IJs) exposed to a host cuticle were more attracted toward certain host-associated volatile odors. We wanted to test the specificity of attraction that results from exposure to host cuticle. Host recognition behavior was analyzed after stimulating IJs by allowing them to physically interact with Galleria mellonella cuticles. The subsequent behavioral response and the proportion of the population participating in chemotaxis to multiple host odors were measured. We found that exposure to host cuticles resulted in a significantly higher percentage of the population participating in host-seeking behavior, with threefold more nematodes participating in chemotaxis. We tested whether exposure to live or dead host cuticle resulted in a different response and found that a higher percentage of IJs exposed to a live host cuticle participated in chemotaxis than IJs exposed to a dead host cuticle, but that IJs exposed to a dead host demonstrated significantly higher participation than was observed for non-stimulated IJs. To test whether the increase in IJ participation in host-seeking behaviors after exposure to a live host cuticle was specific, we exposed stimulated IJs to a known repulsive odor, a neutral odor, and two predicted attractants. We found that stimulation of IJs through physical contact with a host cuticle induces a specific enhancement of host-seeking behavior to host-specific odors rather than a general increased chemotactic response to all volatile stimuli. However, the nematodes displayed an enhanced response to multiple host-specific odors. Future work should focus on the mechanism through which contact with live host cuticle stimulates increased behavioral response.
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Affiliation(s)
- Tiffany Baiocchi
- Department of Nematology, University of California Riverside , Riverside, CA, 92521
| | - Lauren Braun
- Department of Nematology, University of California Riverside , Riverside, CA, 92521
| | - Adler R Dillman
- Department of Nematology, University of California Riverside , Riverside, CA, 92521
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23
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Bryant AS, Hallem EA. Terror in the dirt: Sensory determinants of host seeking in soil-transmitted mammalian-parasitic nematodes. Int J Parasitol Drugs Drug Resist 2018; 8:496-510. [PMID: 30396862 PMCID: PMC6287541 DOI: 10.1016/j.ijpddr.2018.10.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 10/22/2018] [Accepted: 10/24/2018] [Indexed: 12/12/2022]
Abstract
Infection with gastrointestinal parasitic nematodes is a major cause of chronic morbidity and economic burden around the world, particularly in low-resource settings. Some parasitic nematode species, including the human-parasitic threadworm Strongyloides stercoralis and human-parasitic hookworms in the genera Ancylostoma and Necator, feature a soil-dwelling infective larval stage that seeks out hosts for infection using a variety of host-emitted sensory cues. Here, we review our current understanding of the behavioral responses of soil-dwelling infective larvae to host-emitted sensory cues, and the molecular and cellular mechanisms that mediate these responses. We also discuss the development of methods for transgenesis and CRISPR/Cas9-mediated targeted mutagenesis in Strongyloides stercoralis and the closely related rat parasite Strongyloides ratti. These methods have established S. stercoralis and S. ratti as genetic model systems for gastrointestinal parasitic nematodes and are enabling more detailed investigations into the neural mechanisms that underlie the sensory-driven behaviors of this medically and economically important class of parasites.
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Affiliation(s)
- Astra S Bryant
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA.
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24
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Bryant AS, Hallem EA. Temperature-dependent behaviors of parasitic helminths. Neurosci Lett 2018; 687:290-303. [PMID: 30336196 PMCID: PMC6240462 DOI: 10.1016/j.neulet.2018.10.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 10/09/2018] [Accepted: 10/10/2018] [Indexed: 02/07/2023]
Abstract
Parasitic helminth infections are the most common source of neglected tropical disease among impoverished global communities. Many helminths infect their hosts via an active, sensory-driven process in which environmentally motile infective larvae position themselves near potential hosts. For these helminths, host seeking and host invasion can be divided into several discrete behaviors that are regulated by both host-emitted and environmental sensory cues, including heat. Thermosensation is a critical sensory modality for helminths that infect warm-blooded hosts, driving multiple behaviors necessary for host seeking and host invasion. Furthermore, thermosensory cues influence the host-seeking behaviors of both helminths that parasitize endothermic hosts and helminths that parasitize insect hosts. Here, we discuss the role of thermosensation in guiding the host-seeking and host-infection behaviors of a diverse group of helminths, including mammalian-parasitic nematodes, entomopathogenic nematodes, and schistosomes. We also discuss the neural circuitry and molecular pathways that underlie thermosensory responses in these species.
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Affiliation(s)
- Astra S Bryant
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
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25
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Mastore M, Quadroni S, Toscano A, Mottadelli N, Brivio MF. Susceptibility to entomopathogens and modulation of basal immunity in two insect models at different temperatures. J Therm Biol 2018; 79:15-23. [PMID: 30612676 DOI: 10.1016/j.jtherbio.2018.11.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 10/31/2018] [Accepted: 11/12/2018] [Indexed: 11/30/2022]
Abstract
In this work, we analysed the efficacy of different commercial bio-insecticides (Steinernema feltiae, Steinernema carpocapsae, Heterorhabditis bacteriophora and Bacillus thuringiensis) by valuating the mortality induced on two insect models, Galleria mellonella (Lepidoptera) and Sarcophaga africa (Diptera) after exposure to different temperatures (10, 20 and 30 °C). Moreover, we investigated the effects of temperature on the basal humoral immunity of the two target insects; particularly, phenoloxidase (PO) and lysozyme activity. Our results show that G. mellonella is susceptible to all bio-insecticides at all the examined temperatures, except when infected at 10 °C with S. carpocapsae and at 30 °C with S. feltiae and B. thuringiensis. S. africa is more susceptible at 30 °C to all bioinsecticides; whereas, when infected at 10 and 20 °C, H. bacteriophora is the most efficient. Temperature modulates PO activity of both G. mellonella and S. africa, otherwise variations in lysozyme activity is observed only in G. mellonella. Except for a possible correlation between the increased lysozyme activity and the delayed Bt efficacy recorded on G. mellonella at 30 °C, a different resistance to bio-insecticides at different temperatures does not seem to be associated to variations of the host basal immunity, probably due to immunoevasive and immunodepressive strategies of these entomopathogens.
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Affiliation(s)
- Maristella Mastore
- Lab. of Comparative Immunology and Parasitology, Dept. of Theoretical and Applied Sciences, University of Insubria, Varese, Italy
| | - Silvia Quadroni
- Lab. of Ecology, Dept. of Science and High Technology, University of Insubria, Varese, Italy
| | - Andrea Toscano
- Lab. of Comparative Immunology and Parasitology, Dept. of Theoretical and Applied Sciences, University of Insubria, Varese, Italy
| | - Nicolò Mottadelli
- Lab. of Comparative Immunology and Parasitology, Dept. of Theoretical and Applied Sciences, University of Insubria, Varese, Italy
| | - Maurizio F Brivio
- Lab. of Comparative Immunology and Parasitology, Dept. of Theoretical and Applied Sciences, University of Insubria, Varese, Italy.
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26
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Bryant AS, Ruiz F, Gang SS, Castelletto ML, Lopez JB, Hallem EA. A Critical Role for Thermosensation in Host Seeking by Skin-Penetrating Nematodes. Curr Biol 2018; 28:2338-2347.e6. [PMID: 30017486 PMCID: PMC6091634 DOI: 10.1016/j.cub.2018.05.063] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 05/18/2018] [Accepted: 05/22/2018] [Indexed: 12/31/2022]
Abstract
Skin-penetrating parasitic nematodes infect approximately one billion people worldwide and are a major source of neglected tropical disease [1-6]. Their life cycle includes an infective third-larval (iL3) stage that searches for hosts to infect in a poorly understood process that involves both thermal and olfactory cues. Here, we investigate the temperature-driven behaviors of skin-penetrating iL3s, including the human-parasitic threadworm Strongyloides stercoralis and the human-parasitic hookworm Ancylostoma ceylanicum. We show that human-parasitic iL3s respond robustly to thermal gradients. Like the free-living nematode Caenorhabditis elegans, human-parasitic iL3s show both positive and negative thermotaxis, and the switch between them is regulated by recent cultivation temperature [7]. When engaging in positive thermotaxis, iL3s migrate toward temperatures approximating mammalian body temperature. Exposing iL3s to a new cultivation temperature alters the thermal switch point between positive and negative thermotaxis within hours, similar to the timescale of thermal plasticity in C. elegans [7]. Thermal plasticity in iL3s may enable them to optimize host finding on a diurnal temperature cycle. We show that temperature-driven responses can be dominant in multisensory contexts such that, when thermal drive is strong, iL3s preferentially engage in temperature-driven behaviors despite the presence of an attractive host odorant. Finally, targeted mutagenesis of the S. stercoralis tax-4 homolog abolishes heat seeking, providing the first evidence that parasitic host-seeking behaviors are generated through an adaptation of sensory cascades that drive environmental navigation in C. elegans [7-10]. Together, our results provide insight into the behavioral strategies and molecular mechanisms that allow skin-penetrating nematodes to target humans.
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Affiliation(s)
- Astra S Bryant
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Felicitas Ruiz
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Spencer S Gang
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Michelle L Castelletto
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jacqueline B Lopez
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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27
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Host-Specific Activation of Entomopathogenic Nematode Infective Juveniles. INSECTS 2018; 9:insects9020059. [PMID: 29865224 PMCID: PMC6023527 DOI: 10.3390/insects9020059] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 05/28/2018] [Accepted: 06/01/2018] [Indexed: 01/09/2023]
Abstract
Entomopathogenic nematodes (EPNs) are potent insect parasites and have been used for pest control in agriculture. Despite the complexity of the EPN infection process, hosts are typically killed within 5 days of initial infection. When free-living infective juveniles (IJs) infect a host, they release their bacterial symbiont, secrete toxic products, and undergo notable morphological changes. Collectively, this process is referred to as “activation” and represents the point in a nematode’s life cycle when it becomes actively parasitic. The effect of different host tissues and IJ age on activation, and how activation itself is related to virulence, are not well understood. Here, we employed a recently developed bioassay, which quantifies IJ activation, as a tool to address these matters. Appreciating that activation is a key part of the EPN infection process, we hypothesized that activation would positively correlate to virulence. Using the EPNs Steinernema carpocapsae and S. feltiae we found that EPN activation is host-specific and influenced by infective juvenile age. Additionally, our data suggest that activation has a context-dependent influence on virulence and could be predictive of virulence in some cases such as when IJ activation is especially low.
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28
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Ruiz F, Castelletto ML, Gang SS, Hallem EA. Experience-dependent olfactory behaviors of the parasitic nematode Heligmosomoides polygyrus. PLoS Pathog 2017; 13:e1006709. [PMID: 29190282 PMCID: PMC5708605 DOI: 10.1371/journal.ppat.1006709] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 10/24/2017] [Indexed: 12/26/2022] Open
Abstract
Parasitic nematodes of humans and livestock cause extensive disease and economic loss worldwide. Many parasitic nematodes infect hosts as third-stage larvae, called iL3s. iL3s vary in their infection route: some infect by skin penetration, others by passive ingestion. Skin-penetrating iL3s actively search for hosts using host-emitted olfactory cues, but the extent to which passively ingested iL3s respond to olfactory cues was largely unknown. Here, we examined the olfactory behaviors of the passively ingested murine gastrointestinal parasite Heligmosomoides polygyrus. H. polygyrus iL3s were thought to reside primarily on mouse feces, and infect when mice consume feces containing iL3s. However, iL3s can also adhere to mouse fur and infect orally during grooming. Here, we show that H. polygyrus iL3s are highly active and show robust attraction to host feces. Despite their attraction to feces, many iL3s migrate off feces to engage in environmental navigation. In addition, H. polygyrus iL3s are attracted to mammalian skin odorants, suggesting that they migrate toward hosts. The olfactory preferences of H. polygyrus are flexible: some odorants are repulsive for iL3s maintained on feces but attractive for iL3s maintained off feces. Experience-dependent modulation of olfactory behavior occurs over the course of days and is mediated by environmental carbon dioxide (CO2) levels. Similar experience-dependent olfactory plasticity occurs in the passively ingested ruminant-parasitic nematode Haemonchus contortus, a major veterinary parasite. Our results suggest that passively ingested iL3s migrate off their original fecal source and actively navigate toward hosts or new host fecal sources using olfactory cues. Olfactory plasticity may be a mechanism that enables iL3s to switch from dispersal behavior to host-seeking behavior. Together, our results demonstrate that passively ingested nematodes do not remain inactive waiting to be swallowed, but rather display complex sensory-driven behaviors to position themselves for host ingestion. Disrupting these behaviors may be a new avenue for preventing infections. Many parasitic nematodes infect by passive ingestion when the host consumes food, water, or feces containing infective third-stage larvae (iL3s). Passively ingested nematodes that infect humans cause severe gastrointestinal distress and death in endemic regions, and those that infect livestock are a major cause of production loss worldwide. Because these parasites do not actively invade hosts but instead rely on being swallowed by hosts, it has been assumed that they show only limited sensory responses and do not engage in host-seeking behaviors. Here, we investigate the olfactory behaviors of the passively ingested murine parasite Heligmosomoides polygyrus and show that this assumption is incorrect; H. polygyrus iL3s show robust attraction to a diverse array of odorants found in mammalian skin, sweat, and feces. Moreover, the olfactory responses of H. polygyrus iL3s are experience-dependent: some odorants are repulsive to iL3s cultured on feces but attractive to iL3s removed from feces. Olfactory plasticity is also observed in the ruminant parasite Haemonchus contortus, and may enable iL3s to disperse in search of new hosts or host fecal sources. Our results suggest that passively ingested nematodes use olfactory cues to navigate their environments and position themselves where they are likely to be swallowed. By providing new insights into the olfactory behaviors of these parasites, our results may enable the development of new strategies for preventing infections.
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Affiliation(s)
- Felicitas Ruiz
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Michelle L. Castelletto
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Spencer S. Gang
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Elissa A. Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Guillermin ML, Carrillo MA, Hallem EA. A Single Set of Interneurons Drives Opposite Behaviors in C. elegans. Curr Biol 2017; 27:2630-2639.e6. [PMID: 28823678 PMCID: PMC6193758 DOI: 10.1016/j.cub.2017.07.023] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/06/2017] [Accepted: 07/10/2017] [Indexed: 12/21/2022]
Abstract
Many chemosensory stimuli evoke innate behavioral responses that can be either appetitive or aversive, depending on an animal's age, prior experience, nutritional status, and environment [1-9]. However, the circuit mechanisms that enable these valence changes are poorly understood. Here, we show that Caenorhabditis elegans can alternate between attractive or aversive responses to carbon dioxide (CO2), depending on its recently experienced CO2 environment. Both responses are mediated by a single pathway of interneurons. The CO2-evoked activity of these interneurons is subject to extreme experience-dependent modulation, enabling them to drive opposite behavioral responses to CO2. Other interneurons in the circuit regulate behavioral sensitivity to CO2 independent of valence. A combinatorial code of neuropeptides acts on the circuit to regulate both valence and sensitivity. Chemosensory valence-encoding interneurons exist across phyla, and valence is typically determined by whether appetitive or aversive interneuron populations are activated. Our results reveal an alternative mechanism of valence determination in which the same interneurons contribute to both attractive and aversive responses through modulation of sensory neuron to interneuron synapses. This circuit design represents a previously unrecognized mechanism for generating rapid changes in innate chemosensory valence.
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Affiliation(s)
- Manon L Guillermin
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mayra A Carrillo
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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Host seeking parasitic nematodes use specific odors to assess host resources. Sci Rep 2017; 7:6270. [PMID: 28740104 PMCID: PMC5524962 DOI: 10.1038/s41598-017-06620-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 07/04/2017] [Indexed: 01/15/2023] Open
Abstract
Entomopathogenic nematodes (EPNs) are insect parasites used as biological control agents. Free-living infective juveniles (IJs) of EPNs employ host-seeking behaviors to locate suitable hosts for infection. We found that EPNs can differentiate between naïve and infected hosts, and that host attractiveness changes over time in a species-specific manner. We used solid-phase microextraction and gas chromatography/mass spectrometry to identify volatile chemical cues that may relay information about a potential host’s infection status and resource availability. Among the chemicals identified from the headspace of infected hosts, 3-Methyl-2-buten-1-ol (prenol) and 3-Hydroxy-2-butanone (AMC) were selected for further behavioral assays due to their temporal correlation with the behavioral changes of IJs towards the infected hosts. Both compounds were repulsive to IJs of Steinernema glaseri and S. riobrave in a dose-dependent manner when applied on an agar substrate. Furthermore, the repulsive effects of prenol were maintained when co-presented with the uninfected host odors, overriding attraction to uninfected hosts. Prenol was attractive to dauers of some free-living nematodes and insect larvae. These data suggest that host-associated chemical cues may have several implications in EPN biology, not only as signals for avoidance and dispersal of conspecifics, but also as attractants for new potential hosts.
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Lu D, Macchietto M, Chang D, Barros MM, Baldwin J, Mortazavi A, Dillman AR. Activated entomopathogenic nematode infective juveniles release lethal venom proteins. PLoS Pathog 2017; 13:e1006302. [PMID: 28426766 PMCID: PMC5398726 DOI: 10.1371/journal.ppat.1006302] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 03/20/2017] [Indexed: 12/20/2022] Open
Abstract
Entomopathogenic nematodes (EPNs) are unique parasites due to their symbiosis with entomopathogenic bacteria and their ability to kill insect hosts quickly after infection. It is widely believed that EPNs rely on their bacterial partners for killing hosts. Here we disproved this theory by demonstrating that the in vitro activated infective juveniles (IJs) of Steinernema carpocapsae (a well-studied EPN species) release venom proteins that are lethal to several insects including Drosophila melanogaster. We confirmed that the in vitro activation is a good approximation of the in vivo process by comparing the transcriptomes of individual in vitro and in vivo activated IJs. We further analyzed the transcriptomes of non-activated and activated IJs and revealed a dramatic shift in gene expression during IJ activation. We also analyzed the venom proteome using mass spectrometry. Among the 472 venom proteins, proteases and protease inhibitors are especially abundant, and toxin-related proteins such as Shk domain-containing proteins and fatty acid- and retinol-binding proteins are also detected, which are potential candidates for suppressing the host immune system. Many of the venom proteins have conserved orthologs in vertebrate-parasitic nematodes and are differentially expressed during IJ activation, suggesting conserved functions in nematode parasitism. In summary, our findings strongly support a new model that S. carpocapsae and likely other Steinernema EPNs have a more active role in contributing to the pathogenicity of the nematode-bacterium complex than simply relying on their symbiotic bacteria. Furthermore, we propose that EPNs are a good model system for investigating vertebrate- and human-parasitic nematodes, especially regarding the function of excretory/secretory products. Steinernema carpocapsae belongs to a special group of insect-parasitic nematodes known as entomopathogenic nematodes (EPNs). These differ from other insect parasites in at least two ways; first they kill their hosts quickly (within 2–3 days), and second they associate with bacteria to facilitate their parasitic lifestyle. The infective stage of these parasites, the infective juvenile (IJ) stage, is the only free-living stage and these IJs are developmentally arrested and only reinitiate development once they are inside a suitable host. Little is known about the early stages of parasitism and how these parasites initiate the parasitic phase of their life cycle and reinitiate development. Here we characterized the changes that occur to the nematodes' physical morphology, gene expression, and the release of protein molecules that accompany the transition from developmentally arrested IJ to active, developing parasite. We showed that contrary to long-held assumptions, the nematodes are not merely transporting pathogenic bacteria but that the nematodes contribute to parasitism by releasing toxic proteins into the host. Many of the S. carpocapsae toxins are also found in species of human-parasitic nematodes, and S. carpocapsae may serve as a valuable model for understanding the specific function of these toxins.
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Affiliation(s)
- Dihong Lu
- Department of Nematology, University of California, Riverside, California, United States of America
| | - Marissa Macchietto
- Department of Developmental and Cell Biology, Center for Complex Biological Systems, University of California, Irvine, California, United States of America
| | - Dennis Chang
- Department of Nematology, University of California, Riverside, California, United States of America
| | - Mirayana M. Barros
- Department of Nematology, University of California, Riverside, California, United States of America
| | - James Baldwin
- Department of Nematology, University of California, Riverside, California, United States of America
| | - Ali Mortazavi
- Department of Developmental and Cell Biology, Center for Complex Biological Systems, University of California, Irvine, California, United States of America
| | - Adler R. Dillman
- Department of Nematology, University of California, Riverside, California, United States of America
- * E-mail:
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Cevallos JA, Okubo RP, Perlman SJ, Hallem EA. Olfactory Preferences of the Parasitic Nematode Howardula aoronymphium and its Insect Host Drosophila falleni. J Chem Ecol 2017; 43:362-373. [PMID: 28315996 DOI: 10.1007/s10886-017-0834-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/09/2017] [Accepted: 03/06/2017] [Indexed: 10/19/2022]
Abstract
Many parasitic nematodes have an environmental infective stage that searches for hosts. Olfaction plays an important role in this process, with nematodes navigating their environment using host-emitted and environmental olfactory cues. The interactions between parasitic nematodes and their hosts are also influenced by the olfactory behaviors of the host, since host olfactory preferences drive behaviors that may facilitate or impede parasitic infection. However, how olfaction shapes parasite-host interactions is poorly understood. Here we investigated this question using the insect-parasitic nematode Howardula aoronymphium and its host, the mushroom fly Drosophila falleni. We found that both H. aoronymphium and D. falleni are attracted to mushroom odor and a subset of mushroom-derived odorants, but they have divergent olfactory preferences that are tuned to different mushroom odorants despite their shared mushroom environment. H. aoronymphium and D. falleni respond more narrowly to odorants than Caenorhabditis elegans and Drosophila melanogaster, consistent with their more specialized niches. Infection of D. falleni with H. aoronymphium alters its olfactory preferences, rendering it more narrowly tuned to mushroom odor. Our results establish H. aoronymphium-D. falleni as a model system for studying olfaction in the context of parasite-host interactions.
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Affiliation(s)
- James A Cevallos
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Ryo P Okubo
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Steve J Perlman
- Department of Biology, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada
| | - Elissa A Hallem
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.
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Morris R, Wilson L, Sturrock M, Warnock ND, Carrizo D, Cox D, Maule AG, Dalzell JJ. A neuropeptide modulates sensory perception in the entomopathogenic nematode Steinernema carpocapsae. PLoS Pathog 2017; 13:e1006185. [PMID: 28253355 PMCID: PMC5333901 DOI: 10.1371/journal.ppat.1006185] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/15/2017] [Indexed: 11/19/2022] Open
Abstract
Entomopathogenic nematodes (EPNs) employ a sophisticated chemosensory apparatus to detect potential hosts. Understanding the molecular basis of relevant host-finding behaviours could facilitate improved EPN biocontrol approaches, and could lend insight to similar behaviours in economically important mammalian parasites. FMRFamide-like peptides are enriched and conserved across the Phylum Nematoda, and have been linked with motor and sensory function, including dispersal and aggregating behaviours in the free living nematode Caenorhabditis elegans. The RNA interference (RNAi) pathway of Steinernema carpocapsae was characterised in silico, and employed to knockdown the expression of the FMRFamide-like peptide 21 (GLGPRPLRFamide) gene (flp-21) in S. carpocapsae infective juveniles; a first instance of RNAi in this genus, and a first in an infective juvenile of any EPN species. Our data show that 5 mg/ml dsRNA and 50 mM serotonin triggers statistically significant flp-21 knockdown (-84%***) over a 48 h timecourse, which inhibits host-finding (chemosensory), dispersal, hyperactive nictation and jumping behaviours. However, whilst 1 mg/ml dsRNA and 50 mM serotonin also triggers statistically significant flp-21 knockdown (-51%**) over a 48 h timecourse, it does not trigger the null sensory phenotypes; statistically significant target knockdown can still lead to false negative results, necessitating appropriate experimental design. SPME GC-MS volatile profiles of two EPN hosts, Galleria mellonella and Tenebrio molitor reveal an array of shared and unique compounds; these differences had no impact on null flp-21 RNAi phenotypes for the behaviours assayed. Localisation of flp-21 / FLP-21 to paired anterior neurons by whole mount in situ hybridisation and immunocytochemistry corroborates the RNAi data, further suggesting a role in sensory modulation. These data can underpin efforts to study these behaviours in other economically important parasites, and could facilitate molecular approaches to EPN strain improvement for biocontrol.
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Affiliation(s)
- Robert Morris
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Leonie Wilson
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Matthew Sturrock
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Neil D. Warnock
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Daniel Carrizo
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Deborah Cox
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Aaron G. Maule
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
| | - Johnathan J. Dalzell
- School of Biological Sciences, Institute for Global Food Security, Queen’s University Belfast, Belfast, United Kingdom
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Lu D, Sepulveda C, Dillman AR. Infective Juveniles of the Entomopathogenic Nematode Steinernema scapterisci Are Preferentially Activated by Cricket Tissue. PLoS One 2017; 12:e0169410. [PMID: 28046065 PMCID: PMC5207650 DOI: 10.1371/journal.pone.0169410] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 12/17/2016] [Indexed: 11/20/2022] Open
Abstract
Entomopathogenic nematodes are a subgroup of insect-parasitic nematodes that are used in biological control as alternatives or supplements to chemical pesticides. Steinernema scapterisci is an unusual member of the entomopathogenic nematode guild for many reasons including that it is promiscuous in its association with bacteria, it can reproduce in the absence of its described bacterial symbiont, and it is known to have a narrow host range. It is a powerful comparative model within the species and could be used to elucidate parasite specialization. Here we describe a new method of efficiently producing large numbers of S. scapterisci infective juveniles (IJs) in house crickets and for quantifying parasitic activation of the IJs upon exposure to host tissue using morphological features. We found that parasite activation is a temporal process with more IJs activating over time. Furthermore, we found that activated IJs secrete a complex mixture of proteins and that S. scapterisci IJs preferentially activate upon exposure to cricket tissue, reaffirming the description of S. scapterisci as a cricket specialist.
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Affiliation(s)
- Dihong Lu
- Department of Nematology, University of California Riverside, Riverside, California, United States of America
| | - Claudia Sepulveda
- Department of Nematology, University of California Riverside, Riverside, California, United States of America
| | - Adler R. Dillman
- Department of Nematology, University of California Riverside, Riverside, California, United States of America
- * E-mail:
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35
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Olfactory circuits and behaviors of nematodes. Curr Opin Neurobiol 2016; 41:136-148. [PMID: 27668755 DOI: 10.1016/j.conb.2016.09.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 08/19/2016] [Accepted: 09/05/2016] [Indexed: 12/29/2022]
Abstract
Over one billion people worldwide are infected with parasitic nematodes. Many parasitic nematodes actively search for hosts to infect using volatile chemical cues, so understanding the olfactory signals that drive host seeking may elucidate new pathways for preventing infections. The free-living nematode Caenorhabditis elegans is a powerful model for parasitic nematodes: because sensory neuroanatomy is conserved across nematode species, an understanding of the microcircuits that mediate olfaction in C. elegans may inform studies of olfaction in parasitic nematodes. Here we review circuit mechanisms that allow C. elegans to respond to odorants, gases, and pheromones. We also highlight work on the olfactory behaviors of parasitic nematodes that lays the groundwork for future studies of their olfactory microcircuits.
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