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Immunogenetic and tolerance strategies against a novel parasitoid of wild field crickets

ABSTRACT: Among the parasites of insects, endoparasitoids impose a costly challenge to host defenses because they use their host’s body for the development and maturation of their eggs or larvae, and ultimately kill the host. Tachinid flies are highly specialized acoustically-orienting parasitoids that release first instar mobile larvae which burrow into the host’s body to feed. We investigated the possibility that Teleogryllus oceanicus field crickets employ post-infestation strategies to maximize survival when infested with the larvae of the parasitoid fly Ormia ochracea. Using crickets from the Hawaiian island of Kauai, where the parasitoid is present, and crickets from the Cook Islands (Mangaia), where the parasitoid is absent, we evaluated fitness consequences of infestation by comparing feeding behavior, reproductive capacity, and survival of males experimentally infested with O. ochracea larvae. We also evaluated genetic mechanisms underlying host responses by comparing gene expression in crickets infested with fly larvae for different lengths of time with that of uninfested control crickets. We observe some differences in fitness (spermatophore production) and survival (total survival time post-infestation) between populations. However, for both traits significant population effects 1) were not associated with the slope of the response to different numbers of larvae and 2) only emerged from models containing body condition at one but not both time points evaluated. Gene expression patterns also revealed population differences in response to infestation. We did not find evidence for consistent differences in genes associated with immunity or stress response. Taken together, these results suggest that coevolution with the fly does not strongly select for either post-infestation resistance or tolerance of parasitoid larvae in male crickets.

ORGANISM(S): Teleogryllus oceanicus

PROVIDER: GSE151539 | GEO | 2020/06/02

REPOSITORIES: GEO

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Project description:INTRODUCTION: Larvae of the invasive emerald ash borer [EAB, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae)], kill over 99% of green ash (Fraxinus pennsylvanica Marshall) trees they infest, yet a small percentage of green ash (“lingering ash”) survive years of heavy EAB attack. In the face of an ongoing invasion that threatens multiple North American Fraxinus species with extinction, any evidence for reproducible defensive responses in the native species merits investigation.METHODS: We evaluated the capacity of 3 families of green ash F1 progeny to kill EAB larvae when challenged in greenhouse studies by infestation with a uniform density of EAB eggs followed by dissection 8 weeks post-infestation and comparison of the host metabolomic profiles.RESULTS: The mean proportions of host-killed larvae in the 2 families of F1 progeny from lingering ash parents were significantly higher than that of host-killed larvae in the family of F1 progeny from susceptible ash parents (p < 0.001). Untargeted metabolomics comparing F1 progeny in the quartile with the highest percent host-killed larvae (HHK) to F1 progeny in the quartile with the lowest percent host-killed larvae (LHK) and to the uninfested F1 progeny within each family revealed evidence for induced biochemical responses to EAB. Infested trees produced significantly higher levels of select secoiridoids than uninfested trees, and LHK progeny produced significantly higher levels of select secoiridoids than the HHK progeny. HHK progeny produced significantly higher abundances of 3 metabolites annotated as aromatic alkaloids than the LHK and uninfested individuals.DISCUSSION: Based on these results, we hypothesize that green ash responds to EAB infestation. However, only certain trees have the genetic capacity to tailor a response that kills enough EAB larvae to prevent lethal damage to the vascular system. Rigorous tests of this hypothesis will require 15–20 years of additional crossing, phenotyping, and omics analyses. The results of this investigation will encourage the establishment and continuation of breeding programs that, in concert with biocontrol and management, could provide trees that slow, if not halt, the decimation of the Fraxinus gene pool. At the same time, ongoing work on host-insect interaction will contribute to our understanding of how forest trees recognize and defend themselves against phloem-feeding insects.

Project description:Although host-parasitoid interactions are becoming well characterized at the organismal and cellular levels, much remains to be understood of the molecular bases for the host immune response and the parasitoidsâ ability to defeat this immune response. Leptopilina boulardi and L. heterotoma, two closely related, highly infectious natural parasitoids of Drosophila melanogaster, appear to use very different infection strategies at the cellular level. Here, we further characterize cellular level differences in the infection characteristics of these two wasp species using newly derived, virulent inbred strains, and then use whole genome microarrays to compare the transcriptional response of Drosophila to each. While flies attacked by the melanogaster group specialist Leptopilina boulardi (strain Lb17) up-regulate numerous genes encoding proteolytic enzymes, components of the Toll and JAK/STAT pathways, and the melanization cascade as part of a combined cellular and humoral innate immune response, flies attacked by the generalist L. heterotoma (strain Lh14) do not appear to initiate an immune transcriptional response at the time points post-infection we assayed, perhaps due to the rapid venom-mediated lysis of host hemocytes (blood cells). Thus, the specialist parasitoid appears to invoke a full-blown immune response in the host, but suppresses and/or evades downstream components of this response. Given that activation of the host immune response likely depletes the energetic resources of the host, the specialistâs infection strategy seems relatively disadvantageous. However, we uncover the mechanism for one potentially important fitness tradeoff of the generalistâs highly immune suppressive infection strategy. Experiment Overall Design: The parasitoid wasps L. boulardi and L. heterotoma were allowed to attack late second instar D. melanogaster larvae (72 hrs old at 22ËC) in the following manner. Nine petri dishes containing 60 fly larvae were each exposed to six experienced L. boulardi (strain Lb17) female wasps for 2 hrs, another nine plates were exposed to five L. heterotoma (strain Lh14) females, and nine control plates were left uninfected. For each of three time points post-infection (2-5 hrs, 9-12 hrs, 21-24 hrs), 40 larvae from three replicate plates were removed and frozen at -80ËC for RNA extraction and microarray analysis (3 treatments x 3 time points x 3 replicates = 27 samples total).

Project description:BACKGROUND: The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen ‘Candidatus Liberibacter solanacearum’. Currently, the only effective strategies for controlling the diseases associated with this pathogen involve regular pesticide applications to manage psyllid population density. However, such practices are unsustainable and will eventually lead to widespread pesticide resistance in psyllids. Therefore, new control strategies must be developed to increase host-plant resistance to insect vectors. For example, expression of constitutive and inducible plant defenses can be improved through selection. Currently, it is still unknown whether psyllid infestation has any lasting consequences on tomato plant defense or tomato plant gene expression in general. RESULTS: To characterize the genes putatively involved in tomato defense against psyllid infestation, RNA was extracted from psyllid-infested and uninfested tomato leaves (Moneymaker) three weeks post-infestation. Transcriptome analysis identified 362 differentially expressed genes. These differentially expressed genes were primarily associated with defense responses to abiotic/biotic stress, transcription/translation, cellular signaling/transport, and photosynthesis. These gene expression changes suggested that tomato plants underwent a reduction in plant growth/health in exchange for improved defense against stress that was observable three weeks after psyllid infestation. Consistent with these observations, tomato plant growth experiments determined that the plants were shorter three weeks after psyllid infestation. Furthermore, psyllid nymphs had lower survival rates on tomato plants that had been previously psyllid infested. CONCLUSION: These results suggested that psyllid infestation has lasting consequences for tomato gene expression, defense, and growth.

Project description:Cultivated rice (Oryza sativa L.) is frequently exposed to multiple stresses, including Schizotetranychus oryzae mite infestation. Rice domestication has narrowed the genetic diversity of the species, leading to a wide susceptibility. This work aimed to observe the response of two wild rice species (Oryza barthii and O. glaberrima) and two O. sativa genotypes (cv. Nipponbare and f. spontanea) to S. oryzae infestation. Surprisingly, leaf damage, histochemistry, chlorophyll concentration and fluorescence showed that the wild species present higher level of leaf damage, increased accumulation of H2O2 and lower photosynthetic capacity when compared to O. sativa genotypes under infested conditions. Infestation decreased tiller number, except in Nipponbare. Infestation also caused the death of wild plants during the reproductive stage. While infestation did not affect the weight of 1,000 grains in both O. sativa genotypes, the number of panicles per plant was affected only in f. spontanea, and the percentage of full seeds per panicle and seed length were increased only in Nipponbare. Using proteomic analysis, we identified 195 differentially abundant proteins when comparing susceptible (O. barthii) and tolerant (Nipponbare) genotypes under control and infested conditions. O. barthii has a less abundant antioxidant arsenal and is unable to modulate proteins involved with general metabolism and energy production under infested condition. Nipponbare presents high abundance of detoxification-related proteins, general metabolic processes and energy production, suggesting that, under infested condition, the primary metabolism is maintained more active compared to O. barthii. Also, under infested conditions, Nipponbare presents higher levels of proline and a greater abundance of defense-related proteins, such as osmotin, ricin B-like lectin, and protease inhibitors. These differentially abundant proteins can be used as biotechnological tools in breeding programs aiming increased tolerance to mite infestation.

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Immunogenetic and tolerance strategies against a novel parasitoid of wild field crickets

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