Articoli di riviste: "Insect nematodes Molecular genetics"

1

Clarke, David J. "Photorhabdus: a tale of contrasting interactions". Microbiology 166, n. 4 (1 aprile 2020): 335–48. http://dx.doi.org/10.1099/mic.0.000907.

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Abstract (sommario):

Different model systems have, over the years, contributed to our current understanding of the molecular mechanisms underpinning the various types of interaction between bacteria and their animal hosts. The genus Photorhabdus comprises Gram-negative insect pathogenic bacteria that are normally found as symbionts that colonize the gut of the infective juvenile stage of soil-dwelling nematodes from the family Heterorhabditis. The nematodes infect susceptible insects and release the bacteria into the insect haemolymph where the bacteria grow, resulting in the death of the insect. At this stage the nematodes feed on the bacterial biomass and, following several rounds of reproduction, the nematodes develop into infective juveniles that leave the insect cadaver in search of new hosts. Therefore Photorhabdus has three distinct and obligate roles to play during this life-cycle: (1) Photorhabdus must kill the insect host; (2) Photorhabdus must be capable of supporting nematode growth and development; and (3) Photorhabdus must be able to colonize the gut of the next generation of infective juveniles before they leave the insect cadaver. In this review I will discuss how genetic analysis has identified key genes involved in mediating, and regulating, the interaction between Photorhabdus and each of its invertebrate hosts. These studies have resulted in the characterization of several new families of toxins and a novel inter-kingdom signalling molecule and have also uncovered an important role for phase variation in the regulation of these different roles.

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Rosenzweig, W. D., D. Premachandran e D. Pramer. "Role of trap lectins in the specificity of nematode capture by fungi". Canadian Journal of Microbiology 31, n. 8 (1 agosto 1985): 693–95. http://dx.doi.org/10.1139/m85-131.

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Seven adhesive-producing nematode-trapping fungi were tested for their ability to capture nine different nematodes. The nematodes included species that are free living as well as plant and insect parasites. The fungi displayed no selectivity. Each fungus was able to trap and consume all of the different nematodes tested. A study of cuticle surface saccharides of five of the nematodes revealed the presence on all the nematodes of glucose–mannose and N-acetylgalactosamine residues. L-Fucose residues were not found on any of the nematodes. The involvement of lectins in the capture of prey by nematode-trapping fungi is discussed.

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Ciche, Todd A., e Jerald C. Ensign. "For the Insect Pathogen Photorhabdus luminescens, Which End of a Nematode Is Out?" Applied and Environmental Microbiology 69, n. 4 (aprile 2003): 1890–97. http://dx.doi.org/10.1128/aem.69.4.1890-1897.2003.

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ABSTRACT The nematode Heterorhabditis bacteriophora is the vector for transmitting the entomopathogenic bacterium Photorhabdus luminescens between insect larvae. The dauer juvenile (DJ) stage nematode selectively retains P. luminescens in its intestine until it releases the bacteria into the hemocoel of an insect host. We report the results of studying the transmission of the bacteria by its nematode vector. Cells of P. luminescens labeled with green fluorescent protein preferentially colonized a region of the DJ intestine immediately behind the basal bulb, extending for various distances toward the anus. Incubation of DJ nematodes in vitro in insect hemolymph induced regurgitation of the bacteria. Following a 30-min lag, the bacteria migrated in a gradual and staggered movement toward and ultimately exited the mouth. This regurgitation reaction was induced by a low-molecular-weight, heat- and protease-stable, anionic component present in arthropod hemolymph and in supernatants from insect cell cultures. Nematodes anesthetized with levamisole or treated with the antihelmenthic agent ivermectin did not release their bacteria into hemolymph. The ability to visualize P. luminescens in the DJ nematode intestine provides the first clues to the mechanism of release of the bacteria during infection of insect larvae. This and the partial characterization of a component of hemolymph triggering release of the bacteria render this fascinating example of both a mutualistic symbiosis and disease transmission amenable to future genetic and molecular study.

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FALAHZADAH, MOHAMMAD HUSSAIN, EBRAHIM SHOKOOHI, GHOLAM HOSSEIN MORAVEJ, PHATU WILLIAM MASHELA, ABDUL KHALID MADADI e JAVAD KARIMI. "Entomophilic nematodes, Diploscapter coronatus and Oscheius tipulae from Afghanistan". Zootaxa 4926, n. 3 (9 febbraio 2021): 401–16. http://dx.doi.org/10.11646/zootaxa.4926.3.5.

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Several soil samples from different habitats in Badakhshan province of Afghanistan were collected to isolate and characterize bacteria feeding nematodes. The Galleria mellonella-baiting method was used for the isolation of the Afghan insect-associated nematodes. The nematodes were studied using morphological and morphometric data. The Oscheius specimen was characterized by a longer body (630–820 µm) and shorter pharynx (125–145 µm), whereas other morphological characters were not unusual. The Diploscapter specimen had an annulated cuticle, with lip region width 1.5 times shorter than the stoma, and had separated pharyngeal corpus from the isthmus and vulva located in the middle of the body. The molecular data were derived using three loci; 18S, 28S (D2/D3 segment), and ITS rRNA region, which were utilized to measure the genetic distance. The phylogenetic analysis was conducted to reconstruct the relationship tree. Both morphological and molecular approaches confirmed the identity of nematode isolates as Oscheius tipulae and Diploscapter coronatus. This is the first report of insect-associated nematodes from the soil of Afghanistan. Both species were capable of infecting and killing G. mellonella larvae in less than 96 h.

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Parks, Sophia C., Susan Nguyen, Shyon Nasrolahi, Chaitra Bhat, Damian Juncaj, Dihong Lu, Raghavendran Ramaswamy et al. "Parasitic nematode fatty acid- and retinol-binding proteins compromise host immunity by interfering with host lipid signaling pathways". PLOS Pathogens 17, n. 10 (29 ottobre 2021): e1010027. http://dx.doi.org/10.1371/journal.ppat.1010027.

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Parasitic nematodes cause significant morbidity and mortality globally. Excretory/secretory products (ESPs) such as fatty acid- and retinol- binding proteins (FARs) are hypothesized to suppress host immunity during nematode infection, yet little is known about their interactions with host tissues. Leveraging the insect parasitic nematode, Steinernema carpocapsae, we describe here the first in vivo study demonstrating that FARs modulate animal immunity, causing an increase in susceptibility to bacterial co-infection. Moreover, we show that FARs dampen key components of the fly immune response including the phenoloxidase cascade and antimicrobial peptide (AMP) production. Our data also reveal that FARs deplete lipid signaling precursors in vivo as well as bind to these fatty acids in vitro, suggesting that FARs elicit their immunomodulatory effects by altering the availability of lipid signaling molecules necessary for an efficient immune response. Collectively, these data support a complex role for FARs in immunosuppression in animals and provide detailed mechanistic insight into parasitism in phylum Nematoda.

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Grewal, P. S., S. Selvan, E. E. Lewis e R. Gaugler. "Male insect-parasitic nematodes: a colonizing sex". Experientia 49, n. 6-7 (luglio 1993): 605–8. http://dx.doi.org/10.1007/bf01955173.

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Matuska-Łyżwa, Joanna, Paulina Żarnowiec e Wiesław Kaca. "Comparison of Biological Activity of Field Isolates of Steinernema feltiae with a Commercial S. feltiae Biopesticide Product". Insects 12, n. 9 (12 settembre 2021): 816. http://dx.doi.org/10.3390/insects12090816.

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Insect trap studies were carried out to determine the presence of entomopathogenic nematodes (EPN) from the family Steinernematidae in the soils of Poland and to compare the biological activities of field nematode isolates with nematodes from commercial biopesticide. The fauna of these organisms in central Poland is poorly studied in both taxonomic and biological terms. Tilled soils representative of this region were sampled from cultivated fields. EPN were isolated from soil samples under laboratory conditions and identified using a key for species identification and molecular analysis. Basic morphometric parameters of infective juveniles and adult males of the first generation were determined. The research showed that males and infective juveniles Steinernema feltiae from Łoniów were the largest. The smallest infective juveniles were found in the isolate from Oblasy, and the smallest males in the isolate from Danków. In Poland, new field isolates showed close genetic similarity to other S. feltiae isolates. The research showed that the field isolates from Poland had greater infectivity and rate of reproduction compared with nematodes from the commercial biopesticide. The findings indicate the potential use of field S. feltiae isolates from Poland (iso1Lon, iso1Dan and iso1Obl) to develop new biopesticide products.

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Marroquin, Lisa D., Dino Elyassnia, Joel S. Griffitts, Jerald S. Feitelson e Raffi V. Aroian. "Bacillus thuringiensis (Bt) Toxin Susceptibility and Isolation of Resistance Mutants in the Nematode Caenorhabditis elegans". Genetics 155, n. 4 (1 agosto 2000): 1693–99. http://dx.doi.org/10.1093/genetics/155.4.1693.

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Abstract The protein toxins produced by Bacillus thuringiensis (Bt) are the most widely used natural insecticides in agriculture. Despite successful and extensive use of these toxins in transgenic crops, little is known about toxicity and resistance pathways in target insects since these organisms are not ideal for molecular genetic studies. To address this limitation and to investigate the potential use of these toxins to control parasitic nematodes, we are studying Bt toxin action and resistance in Caenorhabditis elegans. We demonstrate for the first time that a single Bt toxin can target a nematode. When fed Bt toxin, C. elegans hermaphrodites undergo extensive damage to the gut, a decrease in fertility, and death, consistent with toxin effects in insects. We have screened for and isolated 10 recessive mutants that resist the toxin's effects on the intestine, on fertility, and on viability. These mutants define five genes, indicating that more components are required for Bt toxicity than previously known. We find that a second, unrelated nematicidal Bt toxin may utilize a different toxicity pathway. Our data indicate that C. elegans can be used to undertake detailed molecular genetic analysis of Bt toxin pathways and that Bt toxins hold promise as nematicides.

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Thanwisai, Aunchalee, Paramaporn Muangpat, Wipanee Meesil, Pichamon Janthu, Abdulhakam Dumidae, Chanakan Subkrasae, Jiranun Ardpairin, Sarunporn Tandhavanant, Timothy P. Yoshino e Apichat Vitta. "Entomopathogenic Nematodes and Their Symbiotic Bacteria from the National Parks of Thailand and Larvicidal Property of Symbiotic Bacteria against Aedes aegypti and Culex quinquefasciatus". Biology 11, n. 11 (13 novembre 2022): 1658. http://dx.doi.org/10.3390/biology11111658.

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Entomopathogenic nematodes (EPNs) are insect parasitic nematodes of the genera Het-erorhabditis and Steinernema. These nematodes are symbiotically associated with the bacteria, Photorhabdus and Xenorhabdus, respectively. National parks in Thailand are a potentially rich resource for recovering native EPNs and their symbiotic bacteria. The objectives of this study are to isolate and identify EPNs and their bacterial flora from soil samples in four national parks in Thailand and to evaluate their efficacy for controlling mosquito larvae. Using a baiting method with a Galleria mellonella moth larvae and a White trap technique, 80 out of 840 soil samples (9.5%) from 168 field sites were positive for EPNs. Sequencing of an internal transcribed spacer resulted in the molecular identification of Heterorhabditis nematode isolates as H. indica, H. baujardi and Heterorhabditis SGmg3, while using 28S rDNA sequencing, Steinernema nematode species were identified as S. guang-dongense, S. surkhetense, S. minutum, S. longicaudum and one closely related to S. yirgalemense. For the symbiotic bacterial isolates, based on recA sequencing, the Photorhabdus spp. were identified as P. luminescens subsp. akhurstii, P. luminescens subsp. hainanensis and P. luminescens subsp. australis. Xenorhabdus isolates were identified as X. stockiae, X. indica, X. griffiniae, X. japonica and X. hominickii. Results of bioassays demonstrate that Photorhabdus isolates were effective on both Aedes aegypti and Culex quinquefasciatus. Therefore, we conclude that soil from Thailand’s national parks contain a high diversity of entomopathogenic nematodes and their symbiotic bacteria. Photorhabdus bacteria are larvicidal against culicine mosquitoes and may serve as effective biocontrol agents.

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Chung, Matthew, Preston J. Basting, Rayanna S. Patkus, Alexandra Grote, Ashley N. Luck, Elodie Ghedin, Barton E. Slatko et al. "A Meta-Analysis of Wolbachia Transcriptomics Reveals a Stage-Specific Wolbachia Transcriptional Response Shared Across Different Hosts". G3 Genes|Genomes|Genetics 10, n. 9 (1 settembre 2020): 3243–60. http://dx.doi.org/10.1534/g3.120.401534.

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Abstract Wolbachia is a genus containing obligate, intracellular endosymbionts with arthropod and nematode hosts. Numerous studies have identified differentially expressed transcripts in Wolbachia endosymbionts that potentially inform the biological interplay between these endosymbionts and their hosts, albeit with discordant results. Here, we re-analyze previously published Wolbachia RNA-Seq transcriptomics data sets using a single workflow consisting of the most up-to-date algorithms and techniques, with the aim of identifying trends or patterns in the pan-Wolbachia transcriptional response. We find that data from one of the early studies in filarial nematodes did not allow for robust conclusions about Wolbachia differential expression with these methods, suggesting the original interpretations should be reconsidered. Across datasets analyzed with this unified workflow, there is a general lack of global gene regulation with the exception of a weak transcriptional response resulting in the upregulation of ribosomal proteins in early larval stages. This weak response is observed across diverse Wolbachia strains from both nematode and insect hosts suggesting a potential pan-Wolbachia transcriptional response during host development that diverged more than 700 million years ago.

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Rae, Robbie. "Phasmarhabditis hermaphrodita – a new model to study the genetic evolution of parasitism". Nematology 19, n. 4 (2017): 375–87. http://dx.doi.org/10.1163/15685411-00003053.

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The evolutionary genetic mechanisms that are responsible for the transition of free-living nematodes to parasites are unknown and current nematode models used to study this have limitations. The gastropod parasitePhasmarhabditis hermaphroditacould be used as a new model to dissect the molecular mechanisms involved in the evolution of parasitism.Phasmarhabditis hermaphroditais a facultative parasite of slugs and snails that, likeCaenorhabditis elegansandPristionchus pacificus, can also be maintained easily under laboratory conditions.Phasmarhabditis hermaphroditaandPhasmarhabditisspecies are easy to isolate from the wild and have been found around the world. The phylogenetic position ofPhasmarhabditisis ideal for genomic comparison with other clade 9 species such asC. elegansandP. pacificus, as well as mammalian and insect parasites. These attributes could makeP. hermaphroditaan excellent choice of model to study the evolutionary emergence of parasitism.

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Lulamba, Tshikala Eddie, Ezekiel Green e Mahloro Hope Serepa-Dlamini. "Photorhabdus sp. ETL Antimicrobial Properties and Characterization of Its Secondary Metabolites by Gas Chromatography–Mass Spectrometry". Life 11, n. 8 (4 agosto 2021): 787. http://dx.doi.org/10.3390/life11080787.

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Entomopathogenic nematodes (EPNs) are known to be highly pathogenic to insect pests, due to their associated symbiotic bacteria, which produce virulence factors, exo-enzymes and other harmful secondary metabolites to conquer, kill, and degrade their insect hosts. However, these properties are not fully characterized. This study reports on the antimicrobial activities of Photorhabdus sp. strain ETL, symbiotically associated to an insect pathogenic nematode, Heterorhabditis zealandica, against human pathogenic bacteria and toxigenic fungi, as well as the non-targeted profiling of its secondary metabolites (SMs) using gas chromatography coupled to high-resolution time-of-flight mass spectrometry. Fatty acids including 3-eicosene, (E)-; 5-eicosene, (E)-; eicosene; 9-octadecenamide; undecanoic acid with shown antimicrobial activities were detected. This provided more insight on the composition and bioactivities of SMs produced by the Photorhabdus sp.

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Tomar, Preety, Neelam Thakur e Ajar Nath Yadav. "Indigenous entomopathogenic nematode as biocontrol agents for insect pest management in hilly regions". Plant Science Today 8, sp1 (5 luglio 2022): 51–59. http://dx.doi.org/10.14719/pst.1501.

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The present investigation mainly emphasized on the development and use of entomopathogenic nematodes (EPNs) as a bio-insecticide. The success in controlling insect pests in the soil environments increased the production and use of the adapted indigenous EPNs species for insect management in the fields. EPNs as biocontrol agents were capable for high virulence, easy for application, safe for non-target animals and eco-friendly in nature. These nematodes have ubiquitous nature. These occur in low population in their natural habitat which was mass multiplied in the laboratory. In the present investigation, 5 concentrations (30IJs, 60IJs, 90IJs, 120IJs and 150IJs) of Heterorhabditis bacteriophora strain S15 were applied against the 3rd and 4th instar larvae of four major agricultural insect pests, namely Helicoverpa armigera, Spodoptera litura, Agrotis segetum and Mythimna separata under laboratory conditions at different time exposure (24, 48, 72 and 96 hr). It was observed that the 3rd and 4th larval instars of all 4 insects (H. armigera, S. litura, A. segetum and M. separata) were highly susceptible for the pathogenesis caused by H. bacteriophora Sirmaur isolates. Amongst all insects, both the larval instars of M. separata are highly susceptible for EPNs infection with highest 96% and 98% mortality in highest dose @150IJs. In 3rd instar larvae of other insects such as H. armigera, S. litura and A. segetum larval mortality ranges from 84%, 92% and 94% respectively. Among 4th instar larvae of H. armigera, S. litura and A. segetum the pathogenicity varies from 88%, 94% and 96% respectively. The recorded median lethal concentration (LC50) in 3rd instar larvae of H. armigera, S. litura, A. segetum and M. separata varies from 36.15, 30.05, 30.97 and 23.8. Similarly in 4th instar larvae of H. armigera, S. litura, A. segetum and M. separata, LC50 ranged from 31.41, 28.64, 26.92 and 20.64 respectively. Statistically significant variations were observed in the data recorded on the mortality, in all the treatments. EPNs are the best weapon to overcome insect resistance problems and must be employed to manage insect population.

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Koshel, E. I., V. V. Aleshin, G. A. Eroshenko e V. V. Kutyrev. "Phylogenetic Analysis of Entomoparasitic Nematodes, Potential Control Agents of Flea Populations in Natural Foci of Plague". BioMed Research International 2014 (2014): 1–26. http://dx.doi.org/10.1155/2014/135218.

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Entomoparasitic nematodes are natural control agents for many insect pests, including fleas that transmitYersinia pestis, a causative agent of plague, in the natural foci of this extremely dangerous zoonosis. We examined the flea samples from the Volga-Ural natural focus of plague for their infestation with nematodes. Among the six flea species feeding on different rodent hosts (Citellus pygmaeus,Microtus socialis, andAllactaga major), the rate of infestation varied from 0 to 21%. The propagation rate of parasitic nematodes in the haemocoel of infected fleas was very high; in some cases, we observed up to 1,000 juveniles per flea specimen. Our study of morphology, life cycle, and rDNA sequences of these parasites revealed that they belong to three distinct species differing in the host specificity. On SSU and LSU rRNA phylogenies, these species representing three genera (Rubzovinema,Psyllotylenchus, andSpilotylenchus), constitute a monophyletic group close to Allantonema and Parasitylenchus, the type genera of the families Allantonematidae and Parasitylenchidae (Nematoda: Tylenchida). We discuss the SSU-ITS1-5.8S-LSU rDNA phylogeny of the Tylenchida with a special emphasis on the suborder Hexatylina.

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Poinar, G. O., e G. M. Thomas. "Infection of frog tadpoles (Amphibia) by insect parasitic nematodes (Rhabditida)". Experientia 44, n. 6 (giugno 1988): 528–31. http://dx.doi.org/10.1007/bf01958939.

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Hong, Ray L., e Ralf J. Sommer. "Chemoattraction in Pristionchus Nematodes and Implications for Insect Recognition". Current Biology 16, n. 23 (dicembre 2006): 2359–65. http://dx.doi.org/10.1016/j.cub.2006.10.031.

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Arefin, Badrul, Martin Kunc, Robert Krautz e Ulrich Theopold. "The Immune Phenotype of Three Drosophila Leukemia Models". G3 Genes|Genomes|Genetics 7, n. 7 (1 luglio 2017): 2139–49. http://dx.doi.org/10.1534/g3.117.039487.

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Abstract Many leukemia patients suffer from dysregulation of their immune system, making them more susceptible to infections and leading to general weakening (cachexia). Both adaptive and innate immunity are affected. The fruit fly Drosophila melanogaster has an innate immune system, including cells of the myeloid lineage (hemocytes). To study Drosophila immunity and physiology during leukemia, we established three models by driving expression of a dominant-active version of the Ras oncogene (RasV12) alone or combined with knockdowns of tumor suppressors in Drosophila hemocytes. Our results show that phagocytosis, hemocyte migration to wound sites, wound sealing, and survival upon bacterial infection of leukemic lines are similar to wild type. We find that in all leukemic models the two major immune pathways (Toll and Imd) are dysregulated. Toll–dependent signaling is activated to comparable extents as after wounding wild-type larvae, leading to a proinflammatory status. In contrast, Imd signaling is suppressed. Finally, we notice that adult tissue formation is blocked and degradation of cell masses during metamorphosis of leukemic lines, which is akin to the state of cancer-dependent cachexia. To further analyze the immune competence of leukemic lines, we used a natural infection model that involves insect-pathogenic nematodes. We identified two leukemic lines that were sensitive to nematode infections. Further characterization demonstrates that despite the absence of behavioral abnormalities at the larval stage, leukemic larvae show reduced locomotion in the presence of nematodes. Taken together, this work establishes new Drosophila models to study the physiological, immunological, and behavioral consequences of various forms of leukemia.

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Kitajima, Chihiro, Toshihiro Ichijo e Madoka Ichikawa-Seki. "The first genetic characterization of Setaria marshalli (Nematoda, Spirurida) with reliable DNA barcoding based on a mitochondrial genetic marker". Parasite 29 (2022): 54. http://dx.doi.org/10.1051/parasite/2022054.

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Setaria marshalli is a mosquito-borne filarial nematode that causes infection in calves younger than two years old. In the present study, nematodes were obtained from a calf in Japan and morphologically identified as S. marshalli. Additionally, the partial cytochrome oxidase subunit I (COI) region (596 bp) was analyzed for the first time to establish a reliable DNA barcode. Nucleotide sequences of COI were identical among the seven worms obtained. The COI region can be a useful marker for species discrimination in the case of S. marshalli since nucleotide variations observed between the closest congener, Setaria cervi (51/596 bp), were sufficient to allow species discrimination. However, the phylogenetic relationship of S. marshalli with its congeners was unclear in a maximum likelihood tree. We found that the partial COI sequence of S. marshalli analyzed in the present study matched a relevant section of the complete mitochondrial genome of S. labiatopapillosa that was deposited in the International Nucleotide Sequence Database. This finding suggests that S. marshalli was misdiagnosed as S. labiatopapillosa in a previous study. It is crucial to conduct accurate morphological analyses to obtain reliable molecular information regarding Setaria nematodes.

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Bhat, Aashaq Hussain, Swati Gautum, Aasha Rana, Ashok Kumar Chaubey, Joaquín Abolafia e Vladimír Půža. "Morphological, Morphometrical and Molecular Characterization of Oscheius siddiqii Tabassum and Shahina, 2010 (Rhabditida, Rhabditidae) from India with Its Taxonomic Consequences for the Subgenus Oscheius Andrássy, 1976". Biology 10, n. 12 (27 novembre 2021): 1239. http://dx.doi.org/10.3390/biology10121239.

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An insect parasitic nematode belonging to the genus Oscheius was recovered from the agricultural soils from the Hapur district in western Uttar Pradesh, India. Morphological studies on this species exhibited its high resemblance with two Pakistani species: Oscheius siddiqii and O. niazii. No molecular data are available for these taxa but, morphologically, both species do not differ significantly from our strains and each other. Hence, these nematodes can be considered conspecific, and the correct name for this taxon is O. siddiqii, the first described species. The phylogenetic analyses of the ITS-, 18S-, and the 28S rDNA sequences showed that O. siddiqii is a sister taxon to the group formed by Oscheius microvilli, O. myriophilus, O. safricanus, and several unidentified Oscheius species. Additionally, our analyses show that based on molecular and morphological data, the species Oscheius rugaoensis and O. microvilli cannot be distinguished from O. chongmingensis and O. myriophilus, respectively, and are thus considered junior synonyms of these taxa. Furthermore, the available data are not sufficient to evaluate the status of Oscheius basothovii and O. safricanus, which are, in consequence, considered species inquirendae. These findings highlight the necessity of the proper morphological and molecular characterisation of the described Oscheius species.

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Grewal, Parwinder S., Susan Bornstein-Forst, Ann M. Burnell, Itamar Glazer e Ganpati B. Jagdale. "Physiological, genetic, and molecular mechanisms of chemoreception, thermobiosis, and anhydrobiosis in entomopathogenic nematodes". Biological Control 38, n. 1 (luglio 2006): 54–65. http://dx.doi.org/10.1016/j.biocontrol.2005.09.004.

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Kucerova, Lucie, Vaclav Broz, Badrul Arefin, Houda Ouns Maaroufi, Jana Hurychova, Hynek Strnad, Michal Zurovec e Ulrich Theopold. "The Drosophila Chitinase-Like Protein IDGF3 Is Involved in Protection against Nematodes and in Wound Healing". Journal of Innate Immunity 8, n. 2 (23 dicembre 2015): 199–210. http://dx.doi.org/10.1159/000442351.

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Chitinase-like proteins (CLPs) of the 18 glycosyl hydrolase family retain structural similarity to chitinases but lack enzymatic activity. Although CLPs are upregulated in several human disorders that affect regenerative and inflammatory processes, very little is known about their normal physiological function. We show that an insect CLP (Drosophila imaginal disc growth factor 3, IDGF3) plays an immune-protective role during entomopathogenic nematode (EPN) infections. During these infections, nematodes force their entry into the host via border tissues, thus creating wounds. Whole-genome transcriptional analysis of nematode-infected wild-type and Idgf3 mutant larvae have shown that, in addition to the regulation of genes related to immunity and wound closure, IDGF3 represses Jak/STAT and Wingless signaling. Further experiments have confirmed that IDGF3 has multiple roles in innate immunity. It serves as an essential component required for the formation of hemolymph clots that seal wounds, and Idgf3 mutants display an extended developmental delay during wound healing. Altogether, our findings indicate that vertebrate and invertebrate CLP proteins function in analogous settings and have a broad impact on inflammatory reactions and infections. This opens the way to further genetic analysis of Drosophila IDGF3 and will help to elucidate the exact molecular context of CLP function.

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Dunlop, Jason A., e Russell J. Garwood. "Terrestrial invertebrates in the Rhynie chert ecosystem". Philosophical Transactions of the Royal Society B: Biological Sciences 373, n. 1739 (18 dicembre 2017): 20160493. http://dx.doi.org/10.1098/rstb.2016.0493.

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Abstract (sommario):

The Early Devonian Rhynie and Windyfield cherts remain a key locality for understanding early life and ecology on land. They host the oldest unequivocal nematode worm (Nematoda), which may also offer the earliest evidence for herbivory via plant parasitism. The trigonotarbids (Arachnida: Trigonotarbida) preserve the oldest book lungs and were probably predators that practiced liquid feeding. The oldest mites (Arachnida: Acariformes) are represented by taxa which include mycophages and predators on nematodes today. The earliest harvestman (Arachnida: Opiliones) includes the first preserved tracheae, and male and female genitalia. Myriapods are represented by a scutigeromorph centipede (Chilopoda: Scutigeromorpha), probably a cursorial predator on the substrate, and a putative millipede (Diplopoda). The oldest springtails (Hexapoda: Collembola) were probably mycophages, and another hexapod of uncertain affinities preserves a gut infill of phytodebris. The first true insects (Hexapoda: Insecta) are represented by a species known from chewing (non-carnivorous?) mandibles. Coprolites also provide insights into diet, and we challenge previous assumptions that several taxa were spore-feeders. Rhynie appears to preserve a largely intact community of terrestrial animals, although some expected groups are absent. The known fossils are (ecologically) consistent with at least part of the fauna found around modern Icelandic hot springs. This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.

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Razia, M., R. Karthik Raja, K. Padmanaban, P. Chellapandi e S. Sivaramakrishnan. "16S rDNA-Based Phylogeny of Non-Symbiotic Bacteria of Entomopathogenic Nematodes from Infected Insect Cadavers". Genomics, Proteomics & Bioinformatics 9, n. 3 (giugno 2011): 104–12. http://dx.doi.org/10.1016/s1672-0229(11)60013-2.

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24

Careddu, Giulio, Marcovalerio Botti, Massimo Cristofaro, Simona Sporta Caputi, Edoardo Calizza, Loreto Rossi e Maria Letizia Costantini. "The Feeding Behaviour of Gall Midge Larvae and Its Implications for Biocontrol of the Giant Reed: Insights from Stable Isotope Analysis". Biology 11, n. 12 (12 dicembre 2022): 1805. http://dx.doi.org/10.3390/biology11121805.

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Abstract (sommario):

The gall midge Lasioptera donacis, whose larval stage interferes with the reed’s leaf development, is a potential candidate agent for the biological control of Arundo donax. Reed infestation is always associated with the presence of a saprophytic fungus, Arthrinium arundinis, which is believed to provide food for the larvae. Larvae also interact with a parasitic nematode, Tripius gyraloura, which can be considered its natural enemy. To deepen our knowledge of the plant–fungus–insect trophic interactions and to understand the effects of the nematode on midge larval feeding behaviour, we applied stable isotope analysis, one of the most effective methods for investigating animal feeding preferences in various contexts. The results showed that on average the fungus accounted for 65% of the diet of the midge larvae, which however consumed the reed and the fungus in variable proportions depending on reed quality (expressed as the C:N ratio). No differences in feeding behaviour were observed between parasitised and non-parasitised midge larvae, indicating that nematodes have no effect in this regard. Due to its trophic habits, L. donacis could be an effective control agent of A. donax and these results need to be considered when implementing biological control measures.

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Kanzaki, Natsumi, Robin M. Giblin-Davis, Rudolf H. Scheffrahn, Hisatomo Taki, Alejandro Esquivel, Kerrie A. Davies e E. Allen Herre. "Reverse Taxonomy for Elucidating Diversity of Insect-Associated Nematodes: A Case Study with Termites". PLoS ONE 7, n. 8 (28 agosto 2012): e43865. http://dx.doi.org/10.1371/journal.pone.0043865.

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26

Elbrense, Hanaa, Amr M. A. Elmasry, Mahmoud F. Seleiman, Mohammad S. AL-Harbi e Ahmed M. Abd El-Raheem. "Can Symbiotic Bacteria (Xenorhabdus and Photorhabdus) Be More Efficient than Their Entomopathogenic Nematodes against Pieris rapae and Pentodon algerinus Larvae?" Biology 10, n. 10 (4 ottobre 2021): 999. http://dx.doi.org/10.3390/biology10100999.

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Abstract (sommario):

Pieris rapae and Pentodon algerinus are considered a global threat to agricultural crops and food security; hence, their control is a critical issue. Heterorhabditid and Steinernematid nematodes, along with their symbiotic bacteria, can achieve the optimal biocontrol agent criterion. Therefore, this study aimed to evaluate the efficacy of Heterorhabditis bacteriophora, Steinernema riobravis, and their symbiotic bacteria (Xenorhabdus and Photorhabdus) against P. rapae and P. algerinus larvae. The virulence of entomopathogenic nematodes (EPNs) was determined at different infective juvenile concentrations and exposure times, while the symbiotic bacteria were applied at the concentration of 3 × 107 colony-forming units (CFU)/mL at different exposure times. Gas chromatography–mass spectrophotometry (GC-MS) analysis and the cytotoxic effect of Photorhabdus sp. and Xenorhabdus sp. were determined. The results indicated that H. bacteriophora, S. riobravis, and their symbiotic bacteria significantly (p ≤ 0.001) induced mortality in both insect species. However, H. bacteriophora and its symbiont, Photorhabdus sp., were more virulent. Moreover, the data clarified that both symbiotic bacteria outperformed EPNs against P. rapae but the opposite was true for P. algerinus. GC-MS analysis revealed the main active compounds that have insecticidal activity. However, the results revealed that there was no significant cytotoxic effect. In conclusion, H. bacteriophora, S. riobravis, and their symbiotic bacteria can be an optimal option for bio-controlling both insect species. Furthermore, both symbiotic bacteria can be utilized independently on EPNs for the management of both pests, and, hence, they can be safely incorporated into biocontrol programs and tested against other insect pests.

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Vancaester, Emmelien, e Mark Blaxter. "Phylogenomic analysis of Wolbachia genomes from the Darwin Tree of Life biodiversity genomics project". PLOS Biology 21, n. 1 (23 gennaio 2023): e3001972. http://dx.doi.org/10.1371/journal.pbio.3001972.

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Abstract (sommario):

The Darwin Tree of Life (DToL) project aims to sequence all described terrestrial and aquatic eukaryotic species found in Britain and Ireland. Reference genome sequences are generated from single individuals for each target species. In addition to the target genome, sequenced samples often contain genetic material from microbiomes, endosymbionts, parasites, and other cobionts. Wolbachia endosymbiotic bacteria are found in a diversity of terrestrial arthropods and nematodes, with supergroups A and B the most common in insects. We identified and assembled 110 complete Wolbachia genomes from 93 host species spanning 92 families by filtering data from 368 insect species generated by the DToL project. From 15 infected species, we assembled more than one Wolbachia genome, including cases where individuals carried simultaneous supergroup A and B infections. Different insect orders had distinct patterns of infection, with Lepidopteran hosts mostly infected with supergroup B, while infections in Diptera and Hymenoptera were dominated by A-type Wolbachia. Other than these large-scale order-level associations, host and Wolbachia phylogenies revealed no (or very limited) cophylogeny. This points to the occurrence of frequent host switching events, including between insect orders, in the evolutionary history of the Wolbachia pandemic. While supergroup A and B genomes had distinct GC% and GC skew, and B genomes had a larger core gene set and tended to be longer, it was the abundance of copies of bacteriophage WO who was a strong determinant of Wolbachia genome size. Mining raw genome data generated for reference genome assemblies is a robust way of identifying and analysing cobiont genomes and giving greater ecological context for their hosts.

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Frey, Jürg E., Beatrice Frey, Daniel Frei, Simon Blaser, Morgan Gueuning e Andreas Bühlmann. "Next generation biosecurity: Towards genome based identification to prevent spread of agronomic pests and pathogens using nanopore sequencing". PLOS ONE 17, n. 7 (25 luglio 2022): e0270897. http://dx.doi.org/10.1371/journal.pone.0270897.

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Abstract (sommario):

The unintentional movement of agronomic pests and pathogens is steadily increasing due to the intensification of global trade. Being able to identify accurately and rapidly early stages of an invasion is critical for developing successful eradication or management strategies. For most invasive organisms, molecular diagnostics is today the method of choice for species identification. However, the currently implemented tools are often developed for certain taxa and need to be adapted for new species, making them ill-suited to cope with the current constant increase in new invasive species. To alleviate this impediment, we developed a fast and accurate sequencing tool allowing to modularly obtain genetic information at different taxonomical levels. Using whole genome amplification (WGA) followed by Oxford nanopore MinION sequencing, our workflow does not require any a priori knowledge on the investigated species and its classification. While mainly focusing on harmful plant pathogenic insects, we also demonstrate the suitability of our workflow for the molecular identification of bacteria (Erwinia amylovora and Escherichia coli), fungi (Cladosporium herbarum, Colletotrichum salicis, Neofabraea alba) and nematodes (Globodera rostochiensis). On average, the pairwise identity between the generated consensus sequences and best GenBank BLAST matches was 99.6 ± 0.6%. Additionally, assessing the generated insect genomic dataset, the potential power of the workflow to detect pesticide resistance genes, as well as arthropod-infecting viruses and endosymbiotic bacteria is demonstrated.

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Alotaibi, Saqer S., Hadeer Darwish, Madiha Zaynab, Sarah Alharthi, Akram Alghamdi, Amal Al-Barty, Mohd Asif, Rania H. Wahdan, Alaa Baazeem e Ahmed Noureldeen. "Isolation, Identification, and Biocontrol Potential of Entomopathogenic Nematodes and Associated Bacteria against Virachola livia (Lepidoptera: Lycaenidae) and Ectomyelois ceratoniae (Lepidoptera: Pyralidae)". Biology 11, n. 2 (11 febbraio 2022): 295. http://dx.doi.org/10.3390/biology11020295.

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Abstract (sommario):

Virachola livia (Lepidoptera: Lycaenidae) and Ectomyelois ceratoniae (Lepidoptera: Pyralidae) are the key pests of pomegranates in Saudi Arabia that are managed mainly using broad-spectrum pesticides. Interactions between the entomopathogenic nematodes (EPNs) Steinernematids, and Heterorhabditids, and their entomopathogenic bacterial symbionts (EPBs) have long been considered monoxenic 2-partner associations responsible for killing insects and, therefore, are widely used in insect pest biocontrol. However, there are limited reports identifying such organisms in Taif, Saudi Arabia. The current study aimed to identify the EPNs and their associated bacteria isolated from Taif, Saudi Arabia, and evaluate their biocontrol potential on third instar larvae of V. livia and E. ceratoniae under laboratory conditions. A total of 35 EPN isolates belonging to Steinernema (20) and Heterorhabditis (15) were recovered from 320 soil samples. Twenty-six isolates of symbiotic or associated bacteria were isolated from EPNs and molecularly identified as Xenorhabdus (6 isolates), Photorhabdus (4 isolates), Pseudomonas (7), or Stenotrophomonas (9). A pathogenicity assay revealed that Steinernema spp. were more virulent than Heterorhabditis spp. against the two pomegranate insects, with LC50 values of 18.5 and 13.6 infective juveniles (IJs)/larva of V. livia for Steinernema spp. and 52 and 32.4 IJs/larva of V. livia for Heterorhabditis spp. at 48 and 72 h post-treatment, respectively. Moreover, LC50 values of 9 and 6.6 IJs/larva (Steinernema spp.) and 34.4 and 26.6 IJs/larva (Heterorhabditis spp.) were recorded for E. ceratoniae larvae at 48 and 72 h post-treatment. In addition, the EPB Stenotrophomonas maltophilia CQ1, isolated from Steinernema spp., surpassed Pseudomonas mosselii SJ10, associated with Heterorhabditis spp., in their ability to kill V. livia or E. ceratoniae larvae within 6 h post-application, resulting in 100% mortality in both insects after 24 and 48 h of exposure. We conclude that either application of EPNs’ IJs or their associated EPBs could serve as potential biocontrol agents for V. livia and E. ceratoniae.

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Ávila-López, Mariana B., José Q. García-Maldonado, Héctor Estrada-Medina, David I. Hernández-Mena, Daniel Cerqueda-García e Víctor M. Vidal-Martínez. "First record of entomopathogenic nematodes from Yucatán State, México and their infectivity capacity against Aedes aegypti". PeerJ 9 (2 luglio 2021): e11633. http://dx.doi.org/10.7717/peerj.11633.

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Abstract (sommario):

Background Biological control using entomopathogenic nematodes (EPN) has demonstrated good potential to contribute to the integral control of mosquito larvae, which as adults are vectors of diseases such as Dengue fever, Zika and Chikungunya. However, until now there are no records of the presence of EPN or their killing capacity in Yucatán state, southern México. The objectives of the current study were: (1) to report the entomopathogenic nematodes present in Yucatán soils and (2) to determine the killing capacity of the most frequent and abundant EPN against Aedes aegypti mosquito larvae and the microbial community developed by Ae. Aegypti exposed to this EPN. Methods The nematodes were collected by the insect trap technique using the great wax moth Galleria mellonella. Internal transcribed spacer (ITS), 28S gene of ribosomal DNA and phylogenetic analyses were performed to identify the EPN. For the bioassay, four concentrations of the most frequent and abundant EPN were tested: 1,260:1 infective juveniles (IJs) per mosquito larvae, 2,520 IJs:1, 3,780 IJs:1 and 5,040 IJs:1. High-throughput sequencing of the 16S rRNA gene was used to identify bacterial amplicon sequences in the mosquito larvae infected with EPN. Results Six isolates of Heterorhabditis were recovered from 144 soil samples. Heterorhabditis indica (four isolates) was the most frequent and abundant EPN, followed by Heterorhabditis n. sp. (two isolates). Both nematodes are reported for the first time for Yucatán state, Mexico. The concentration of 2,520 IJs:1 produced 80% of mosquito larvae mortality in 48 h. Representative members of Photorhabdus genus were numerically dominant (74%) in mosquito larvae infected by H. indica. It is most likely that these bacteria produce secondary toxic metabolites that enhance the mortality of these mosquito larvae.

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Drouin, Guy. "Chromatin diminution in the copepod Mesocyclops edax: diminution of tandemly repeated DNA families from somatic cells". Genome 49, n. 6 (1 giugno 2006): 657–65. http://dx.doi.org/10.1139/g06-022.

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Abstract (sommario):

Chromatin diminution, i.e., the loss of selected chromosomal regions during the differentiation of early embryonic cells into somatic cells, has been described in taxa as varied as ciliates, copepods, insects, nematodes, and hagfish. The nature of the eliminated DNA has been extensively studied in ciliate, nematode, and hagfish species. However, the small size of copepods, which makes it difficult to obtain enough DNA from early embryonic cells for cloning and sequencing, has limited such studies. Here, to identify the sequences eliminated from the somatic cells of a copepod species that undergoes chromatin diminution, we randomly amplified DNA fragments from germ line and somatic line cells of Mesocyclops edax, a freshwater cyclopoid copepod. Of 47 randomly amplified germ line clones, 45 (96%) contained short, tandemly repeated sequences composed of either 2 bp CA-repeats, 8 bp CAAATAGA-repeats, or 9 bp CAAATTAAA-repeats. In contrast, of 83 randomly amplified somatic line clones, only 47 (57%) contained such short, tandemly repeated sequences. As previously observed in some nematode species, our results therefore show that there is partial elimination of chromosomal regions containing (CAAATAGA and CAAATTAAA) repeated sequences during the chromatin diminution observed in the somatic cells of M. edax. We speculate that chromatin diminution might have evolved repeatedly by recruitment of RNAi-related mechanisms to eliminate nonfunctional tandemly repeated DNA sequences from the somatic genome of some species.Key words: chromatin diminution, Mesocyclops edax, copepod, satellite DNA, hetorochromatin.

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Sanda, Nafiu Bala, Bofeng Hou e Youming Hou. "The Entomopathogenic Nematodes H. bacteriophora and S. carpocapsae Inhibit the Activation of proPO System of the Nipa Palm Hispid Octodonta nipae (Coleoptera: Chrysomelidae)". Life 12, n. 7 (9 luglio 2022): 1019. http://dx.doi.org/10.3390/life12071019.

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Abstract (sommario):

Entomopathogenic nematodes are biocontrol agents of invasive insect pests in soil and cryptic habitats. Nipa palm hispid, Octodonta nipae, is a pest of palm trees in Sothern China. To address its increasing damage, environmentally friendly control methods are required. This study aimed to test efficacy of Heterorhabditis bacteriophora and Steinernema carpocapsae on O. nipae and investigated the influence of secondary metabolites, nematodes, and their isolated cuticles on the activation of O. nipae’s prophenoloxidase system using qPCR analysis. Our data revealed that O. nipae were less susceptible to H. bacteriophora than S. carpocapsae and penetrations of infective juveniles were higher with S. carpocapsae treatment than H. bacteriophora. Moreover, expression levels of the serine protease P56, prophenoloxidase activation factor 1, PPO and serine protease inhibitor 28 upon S. carpocapsae and H. bacteriophora infections were generally downregulated at all times. However, upon heating, the cuticles lost their inhibitory effects and resulted in upregulation of the PPO gene. Similarly, the addition of arachidonic acid reversed the process and resulted in the upregulation of the PPO gene compared to the control. Further work is needed to identify toxic substances secreted by these EPNs to evade O. nipae’s immune system.

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Zhang, Hua-Bao, Zheng Cao, Jun-Xue Qiao, Zi-Qian Zhong, Chen-Chen Pan, Chen Liu, Li-Min Zhang e Yu-Feng Wang. "Metabolomics provide new insights into mechanisms of Wolbachia-induced paternal defects in Drosophila melanogaster". PLOS Pathogens 17, n. 8 (12 agosto 2021): e1009859. http://dx.doi.org/10.1371/journal.ppat.1009859.

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Abstract (sommario):

Wolbachia is a group of intracellular symbiotic bacteria that widely infect arthropods and nematodes. Wolbachia infection can regulate host reproduction with the most common phenotype in insects being cytoplasmic incompatibility (CI), which results in embryonic lethality when uninfected eggs fertilized with sperms from infected males. This suggests that CI-induced defects are mainly in paternal side. However, whether Wolbachia-induced metabolic changes play a role in the mechanism of paternal-linked defects in embryonic development is not known. In the current study, we first use untargeted metabolomics method with LC-MS to explore how Wolbachia infection influences the metabolite profiling of the insect hosts. The untargeted metabolomics revealed 414 potential differential metabolites between Wolbachia-infected and uninfected 1-day-old (1d) male flies. Most of the differential metabolites were significantly up-regulated due to Wolbachia infection. Thirty-four metabolic pathways such as carbohydrate, lipid and amino acid, and vitamin and cofactor metabolism were affected by Wolbachia infection. Then, we applied targeted metabolomics analysis with GC-MS and showed that Wolbachia infection resulted in an increased energy expenditure of the host by regulating glycometabolism and fatty acid catabolism, which was compensated by increased food uptake. Furthermore, overexpressing two acyl-CoA catabolism related genes, Dbi (coding for diazepam-binding inhibitor) or Mcad (coding for medium-chain acyl-CoA dehydrogenase), ubiquitously or specially in testes caused significantly decreased paternal-effect egg hatch rate. Oxidative stress and abnormal mitochondria induced by Wolbachia infection disrupted the formation of sperm nebenkern. These findings provide new insights into mechanisms of Wolbachia-induced paternal defects from metabolic phenotypes.

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Bleakley, Bruce H., e Xiang Chen. "Survival of insect pathogenic and human clinical isolates ofPhotorhabdus luminescensin previously sterile soil". Canadian Journal of Microbiology 45, n. 3 (1 marzo 1999): 273–78. http://dx.doi.org/10.1139/w98-231.

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Abstract (sommario):

Most characterized strains of the bacterium Photorhabdus luminescens are symbionts of entomopathogenic nematodes, whereas other strains have been isolated from human clinical specimens. The ability of P. luminescens strains to survive and grow in soil has received limited attention, with some studies indicating these bacteria have little or no ability to persist in soil. Survival and (or) growth of P. luminescens strains in previously sterilized soil, and examination of different soil amendments on their numbers in soil, have not been previously reported. Entomopathogenic P. luminescens (ATCC 29999) and a human clinical isolate (ATCC 43949) were introduced into a soil that had been sterilized by autoclaving, with or without different soil amendments, and bacterial numbers were estimated over time by viable plate count. In the previously sterilized soil receiving no exogenous amendments, numbers fell drastically over a week's time, followed by an increase in numbers by day 30. Treatments involving the addition of calcium carbonate and gelatin or casamino acids to soil usually resulted in higher bacterial numbers. For some sampling dates and soil treatments, there were statistically significant differences between the numbers of the two bacterial strains recovered from soil. The two strains of P. luminescens used in this study were able to survive and grow after being inoculated into previously sterilized soil.Key words: Photorhabdus luminescens, survival, soil.

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Quiroz-Castañeda, Rosa Estela, Ared Mendoza-Mejía, Verónica Obregón-Barboza, Fernando Martínez-Ocampo, Armando Hernández-Mendoza, Felipe Martínez-Garduño, Gabriel Guillén-Solís et al. "Identification of a NewAlcaligenes faecalisStrain MOR02 and Assessment of Its Toxicity and Pathogenicity to Insects". BioMed Research International 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/570243.

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Abstract (sommario):

We report the isolation of a bacterium fromGalleria mellonellalarva and its identification using genome sequencing and phylogenomic analysis. This bacterium was namedAlcaligenes faecalisstrain MOR02. Microscopic analyses revealed that the bacteria are located in the esophagus and intestine of the nematodesSteinernema feltiae, S. carpocapsae, andH. bacteriophora. UsingG. mellonellalarvae as a model, when the larvae were injected with 24,000 CFU in their hemocoel, more than 96% mortality was achieved after 24 h. Additionally, toxicity assays determined that 1 μg of supernatant extract fromA. faecalisMOR02 killed more than 70%G. mellonellalarvae 96 h after injection. A correlation of experimental data with sequence genome analyses was also performed. We discovered genes that encode proteins and enzymes that are related to pathogenicity, toxicity, and host/environment interactions that may be responsible for the observed phenotypic characteristics. Our data demonstrates that the bacteria are able to use different strategies to colonize nematodes and kill insects to their own benefit. However, there remains an extensive group of unidentified microorganisms that could be participating in the infection process. Additionally, a nematode-bacterium association could be established probably as a strategy of dispersion and colonization.

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Mylonakis, Eleftherios, Lars Podsiadlowski, Maged Muhammed e Andreas Vilcinskas. "Diversity, evolution and medical applications of insect antimicrobial peptides". Philosophical Transactions of the Royal Society B: Biological Sciences 371, n. 1695 (26 maggio 2016): 20150290. http://dx.doi.org/10.1098/rstb.2015.0290.

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Abstract (sommario):

Antimicrobial peptides (AMPs) are short proteins with antimicrobial activity. A large portion of known AMPs originate from insects, and the number and diversity of these molecules in different species varies considerably. Insect AMPs represent a potential source of alternative antibiotics to address the limitation of current antibiotics, which has been caused by the emergence and spread of multidrug-resistant pathogens. To get more insight into AMPs, we investigated the diversity and evolution of insect AMPs by mapping their phylogenetic distribution, allowing us to predict the evolutionary origins of selected AMP families and to identify evolutionarily conserved and taxon-specific families. Furthermore, we highlight the use of the nematode Caenorhabditis elegans as a whole-animal model in high-throughput screening methods to identify AMPs with efficacy against human pathogens, including Acinetobacter baumanii and methicillin-resistant Staphylococcus aureus . We also discuss the potential medical applications of AMPs, including their use as alternatives for conventional antibiotics in ectopic therapies, their combined use with antibiotics to restore the susceptibility of multidrug-resistant pathogens, and their use as templates for the rational design of peptidomimetic drugs that overcome the disadvantages of therapeutic peptides. The article is part of the themed issue ‘Evolutionary ecology of arthropod antimicrobial peptides’.

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Zhou, Jiao, Li-Lin Zhao, Hai-Ying Yu, Yan-Hong Wang, Wei Zhang, Song-Nian Hu, Zhen Zou e Jiang-Hua Sun. "Immune tolerance of vector beetle to its partner plant parasitic nematode modulated by its insect parasitic nematode". FASEB Journal 32, n. 9 (2 aprile 2018): 4862–77. http://dx.doi.org/10.1096/fj.201800247r.

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Burjanadze, Medea, Natalia Kharabadze e Nona Сhkhidze. "Testing local isolates of entomopathogenic microorganisms against Brown Marmorated Stink Bug Halyomorpha halys in Georgia". BIO Web of Conferences 18 (2020): 00006. http://dx.doi.org/10.1051/bioconf/20201800006.

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Abstract (sommario):

The brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae) (BMSB) is an exotic invasive insect which has spread extensively and established in new area of Black sea regions of Georgia. During 2017-2019, infected adults with fungal disease symptoms were found in population of H. halys from different regions of Western Georgia. Three isolates of entomopathogenic fungus Beauveria bassiana sensu lato and one of Isaria cf fumosorosea were recovered. Mycoinsecticide Bover-Ge, based on a local strain of B. bassiana-024 (isolated from soil high mountain of Caucasus Range, provide molecular identification in CABI-UK, gave a unique cultural number - IMI # 501797 and keep in CABI Genetic Recourse Collection) two concentrations (1×107 and 1×108 conidia/ml) was tested on the adults of H. halys in laboratory and its efficiency reached 72.0-90.5%. Under laboratory conditions, local isolates of nematodes Heterorhabditis bacteriophora and Steinernema borjomiensis were tested on H. halys adults. At three increasing concentrations (200, 500 and 1000 IJs/mL), H. bacteriophora caused bug mortality at the rates of 33-47%. As for Steinernema borjomiensis, the respective values were 13-33%.

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Siozios, Stefanos, Jack Pilgrim, Alistair C. Darby, Matthew Baylis e Gregory D. D. Hurst. "The draft genome of strain cCpun from biting midges confirms insect Cardinium are not a monophyletic group and reveals a novel gene family expansion in a symbiont". PeerJ 7 (21 febbraio 2019): e6448. http://dx.doi.org/10.7717/peerj.6448.

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Abstract (sommario):

Background It is estimated that 13% of arthropod species carry the heritable symbiont Cardinium hertigii. 16S rRNA and gyrB sequence divides this species into at least four groups (A–D), with the A group infecting a range of arthropods, the B group infecting nematode worms, the C group infecting Culicoides biting midges, and the D group associated with the marine copepod Nitocra spinipes. To date, genome sequence has only been available for strains from groups A and B, impeding general understanding of the evolutionary history of the radiation. We present a draft genome sequence for a C group Cardinium, motivated both by the paucity of genomic information outside of the A and B group, and the importance of Culicoides biting midge hosts as arbovirus vectors. Methods We reconstructed the genome of cCpun, a Cardinium strain from group C that naturally infects Culicoides punctatus, through Illumina sequencing of infected host specimens. Results The draft genome presented has high completeness, with BUSCO scores comparable to closed group A Cardinium genomes. Phylogenomic analysis based on concatenated single copy core proteins do not support Cardinium from arthropod hosts as a monophyletic group, with nematode Cardinium strains nested within the two groups infecting arthropod hosts. Analysis of the genome of cCpun revealed expansion of a variety of gene families classically considered important in symbiosis (e.g., ankyrin domain containing genes), and one set—characterized by DUF1703 domains—not previously associated with symbiotic lifestyle. This protein group encodes putative secreted nucleases, and the cCpun genome carried at least 25 widely divergent paralogs, 24 of which shared a common ancestor in the C group. The genome revealed no evidence in support of B vitamin provisioning to its haematophagous host, and indeed suggests Cardinium may be a net importer of biotin. Discussion These data indicate strains of Cardinium within nematodes cluster within Cardinium strains found in insects. The draft genome of cCpun further produces new hypotheses as to the interaction of the symbiont with the midge host, in particular the biological role of DUF1703 nuclease proteins that are predicted as being secreted by cCpun. In contrast, the coding content of this genome provides no support for a role for the symbiont in provisioning the host with B vitamins.

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Wu, Yixia, Jacob D. Wickham, Lilin Zhao e Jianghua Sun. "CO2 drives the pine wood nematode off its insect vector". Current Biology 29, n. 13 (luglio 2019): R619—R620. http://dx.doi.org/10.1016/j.cub.2019.05.033.

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Arunkumar, K. P., e Javaregowda Nagaraju. "Unusually Long Palindromes Are Abundant in Mitochondrial Control Regions of Insects and Nematodes". PLoS ONE 1, n. 1 (20 dicembre 2006): e110. http://dx.doi.org/10.1371/journal.pone.0000110.

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Xue, Wen-Hua, Nan Xu, Sun-Jie Chen, Xin-Yang Liu, Jin-Li Zhang e Hai-Jun Xu. "Neofunctionalization of a second insulin receptor gene in the wing-dimorphic planthopper, Nilaparvata lugens". PLOS Genetics 17, n. 6 (28 giugno 2021): e1009653. http://dx.doi.org/10.1371/journal.pgen.1009653.

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Abstract (sommario):

A single insulin receptor (InR) gene has been identified and extensively studied in model species ranging from nematodes to mice. However, most insects possess additional copies of InR, yet the functional significance, if any, of alternate InRs is unknown. Here, we used the wing-dimorphic brown planthopper (BPH) as a model system to query the role of a second InR copy in insects. NlInR2 resembled the BPH InR homologue (NlInR1) in terms of nymph development and reproduction, but revealed distinct regulatory roles in fuel metabolism, lifespan, and starvation tolerance. Unlike a lethal phenotype derived from NlInR1 null, homozygous NlInR2 null mutants were viable and accelerated DNA replication and cell proliferation in wing cells, thus redirecting short-winged–destined BPHs to develop into long-winged morphs. Additionally, the proper expression of NlInR2 was needed to maintain symmetric vein patterning in wings. Our findings provide the first direct evidence for the regulatory complexity of the two InR paralogues in insects, implying the functionally independent evolution of multiple InRs in invertebrates.

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43

Chapman, Christine, e Louis S. Tisa. "Identification and characterization of Photorhabdus temperata mutants altered in hemolysis and virulence". Canadian Journal of Microbiology 62, n. 8 (agosto 2016): 657–67. http://dx.doi.org/10.1139/cjm-2016-0102.

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Photorhabdus temperata is a symbiont of the entomopathogenic nematode Heterorhabditis bacteriophora and an insect pathogen. This bacterium produces a wide variety of virulence factors and hemolytic activity. The goal of this study was to identify hemolysin-defective mutants and test their virulence. A genetic approach was used to identify mutants with altered hemolytic activity by screening a library of 10 000 P. temperata transposon mutants. Three classes of mutants were identified: (i) defective (no hemolytic activity), (ii) delayed (delayed initiation of hemolytic activity), and (iii) early (early initiation of hemolytic activity). The transposon insertion sites for these mutants were identified and used to investigate other physiological properties, including insect pathogenesis and motility. The hemolysin-defective mutants, P10A-C11, P10A-H12, and P79-B5, had inserts in genes involved in RNA turnover (RNase II and 5′-pentaphospho-5′-adenosine pyrophosphohydrolase) and showed reduced virulence and production of extracellular factors. These data support the role of RNA turnover in insect pathogenesis and other physiological functions.

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Grenier, Eric, Monique Abadon, Frédéric Brunet, Pierre Capy e Pierre Abad. "A Mariner-Like Transposable Element in the Insect Parasite Nematode Heterorhabditis bacteriophora". Journal of Molecular Evolution 48, n. 3 (marzo 1999): 328–36. http://dx.doi.org/10.1007/pl00006476.

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45

Burnell, Ann, e S. Patricia Stock. "Heterorhabditis, Steinernema and their bacterial symbionts — lethal pathogens of insects". Nematology 2, n. 1 (2000): 31–42. http://dx.doi.org/10.1163/156854100508872.

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AbstractThe entomopathogenic nematodes (EPN) Heterorhabditis and Steinernema together with their symbiont bacteria Photorhabdus and Xenorhabdus, respectively, are obligate and lethal parasites of insects. EPN can provide effective biological control of some important lepidopteran, dipteran and coleopteran pests of commercial crops and they are amenable to large-scale culture in liquid fermentors. They are unique among rhabditids in having a symbiotic relationship with an enteric bacterium species. The bacterial symbiont is required to kill the insect host and to digest the host tissues, thereby providing suitable nutrient conditions for nematode growth and development. This review describes the general biology of EPN and their symbionts and gives an overview of studies to date on EPN biodiversity, biogeography and phylogeny. The impetus for research in EPN and their symbionts has come about because of their biological control potential, with much of the focus in EPN research having been on applied aspects relating to pest control. However EPN and their symbionts are increasingly being viewed as exciting subjects for basic research in the areas of ecology, biodiversity, evolution, biochemistry, symbiosis and molecular genetics. Much progress has been made over the past 20 years in our understanding of the basic biology and genetics of EPN and their symbionts. We are now entering a new phase in which the tools of molecular genetics are being increasingly used to address a range of biological questions in EPN research. The knowledge gained from this endeavour should ensure that EPN will become even more effective biopesticides and should also ensure that EPN and their symbionts gain prominence as unique and intrinsically interesting biological systems. Les nématodes entomopathogènes (EPN) Heterorhabditis et Steinernema, avec leur bactéries symbiotes Photorhabdus et Xenorhabdus, respectivement, sont des parasites obligés et mortels des insectes. Les EPN peuvent servir à un contrôle biologique de quelques lépidoptères, diptères et coléoptères importants pour les cultures commerciales et ils sont élevables à grande échelle dans des fermenteurs liquides. Ils sont uniques chez les rhabditides par leur relation symbiotique avec une espèce de bactérie entérique. La bactérie symbiote est nécessaire pour tuer l’insecte hôte et pour digérer les tissus de l’hôte, permettant ainsi des conditons de nutrition favorables à la croissance et au développement du nématode. La présente revue décrit la biologie générale des EPN et de leur symbiotes et donne un état des études actuelles sur la biodiversité, la biogéographie et la phylogénie des EPN. L’impulsion donnée aux recherches sur les EPN et leur symbiotes provient de leur potentialités pour le contrôle biologique, une grande partie des recherches sur les EPN ayant trait à des aspects appliqués en relation avec ce contrôle des parasites. Cependant, les EPN et leur symbiotes bactériens sont de plus en plus considérés comme des sujets intéressants pour la recherche fondamentale dans les domaines de l’écologie, de la biodiversité, de l’évolution, de la biochimie, des processus symbiotiques et de la génétique moléculaire. De nombreux progrès ont été réalisés ces 20 dernières années dans la compréhension de la biologie et de la génétique des EPN et de leur symbiotes. Nous entrons actuellement dans une nouvelle phase ou les moyens de la biologie moléculaire sont utilisés de manière croissante pour formuler une série de questions biologiques pour la recherche sur les EPN. Les connaissances résultant de ces efforts doivent conduire à vérifier que les EPN deviendront des biopesticides toujours plus efficaces et que les EPN et leur symbiotes prendront de l’importance en tant que systèmes biologiques uniques et intrinsèquement intéressants.

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Toubarro, Duarte, Mónica Martinez Avila, Rafael Montiel e Nelson Simões. "A Pathogenic Nematode Targets Recognition Proteins to Avoid Insect Defenses". PLoS ONE 8, n. 9 (30 settembre 2013): e75691. http://dx.doi.org/10.1371/journal.pone.0075691.

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Chen, Jeng-Shong, Thomas W. Sappington e Alexander S. Raikhel. "Extensive Sequence Conservation Among Insect, Nematode, and Vertebrate Vitellogenins Reveals Ancient Common Ancestry". Journal of Molecular Evolution 44, n. 4 (aprile 1997): 440–51. http://dx.doi.org/10.1007/pl00006164.

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Li, Xiaogang, e Biao Liu. "A 2-Year Field Study Shows Little Evidence That the Long-Term Planting of Transgenic Insect-Resistant Cotton Affects the Community Structure of Soil Nematodes". PLoS ONE 8, n. 4 (16 aprile 2013): e61670. http://dx.doi.org/10.1371/journal.pone.0061670.

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Han, Richou. "ADVANCES IN THE RESEARCH OF ENTOMOPATHOGENIC NEMATODES STEINERNEMA AND HETERORHABDITIS IN CHINA". Insect Science 1, n. 4 (dicembre 1994): 346–64. http://dx.doi.org/10.1111/j.1744-7917.1994.tb00265.x.

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Li, Diyan, Yuan Su, Jianbo Tu, Ranlei Wei, Xiaolan Fan, Huadong Yin, Yaodong Hu et al. "Evolutionary conservation of the circadian gene timeout in Metazoa". Animal Biology 66, n. 1 (2016): 1–11. http://dx.doi.org/10.1163/15707563-00002482.

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Timeless (Tim) is considered to function as an essential circadian clock gene in Drosophila. Putative homologues of the Drosophila timeless gene have been identified in both mice and humans. While Drosophila contains two paralogs, timeless and timeout, acting in clock/light entrainment and chromosome integrity/photoreception, respectively, mammals contain only one Tim homolog. In this paper, we study the phylogeny of the timeless/timeout family in 48 species [including 1 protozoan (Guillardia theta), 1 nematode (Caenorhabditis elegans), 8 arthropods and 38 chordates], for which whole genome data are available by using MEGA (Molecular Evolutionary Genetics Analysis). Phylogenetic Analysis by Maximum Likelihood (PAML) was used to analyze the selective pressure acting on metazoan timeless/timeout genes. Our phylogeny clearly separates insect timeless and timeout lineages and shows that non-insect animal Tim genes are homologs of insect timeout. In this study, we explored the relatively rapidly evolving timeless lineage that was apparently lost from most deuterostomes, including chordates, and from Caenorhabditis elegans. In contrast, we found that the timeout protein, often confusingly called “timeless” in the vertebrate literature, is present throughout the available animal genomes. Selection results showed that timeout is under weaker negative selection than timeless. Finally, our phylogeny of timeless/timeout showed an evolutionary conservation of the circadian clock gene timeout in Metazoa. This conservation is in line with its multifunctionality, being essential for embryonic development and maintenance of chromosome integrity, among others.

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