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1.
BMC Genomics ; 21(1): 34, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31924169

RESUMO

BACKGROUND: Venom is one of the most important sources of regulation factors used by parasitic Hymenoptera to redirect host physiology in favour of the developing offspring. This has stimulated a number of studies, both at functional and "omics" level, which, however, are still quite limited for ectophagous parasitoids that permanently paralyze and suppress their victims (i.e., idiobiont parasitoids). RESULTS: Here we present a combined transcriptomic and proteomic study of the venom of the generalist idiobiont wasp Bracon nigricans, an ectophagous larval parasitoid of different lepidopteran species, for which we recently described the host regulation strategy and the functional role of the venom in the induction of physiological changes in parasitized hosts. The experimental approach used led to the identification of the main components of B. nigricans venom involved in host regulation. Enzymes degrading lipids, proteins and carbohydrates are likely involved in the mobilization of storage nutrients from the fat body and may concurrently be responsible for the release of neurotoxic fatty acids inducing paralysis, and for the modulation of host immune responses. CONCLUSION: The present work contributes to fill the gap of knowledge on venom composition in ectoparasitoid wasps, and, along with our previous physiological study on this species, provides the foundation on which to develop a functional model of host regulation, based both on physiological and molecular data. This paves the way towards a better understanding of parasitism evolution in the basal lineages of Hymenoptera and to the possible exploitation of venom as source of bioinsecticidal molecules.

2.
BMC Genomics ; 20(1): 893, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31752718

RESUMO

BACKGROUND: Parasitic insects are well-known biological control agents for arthropod pests worldwide. They are capable of regulating their host's physiology, development and behaviour. However, many of the molecular mechanisms involved in host-parasitoid interaction remain unknown. RESULTS: We sequenced the genomes of two parasitic wasps (Cotesia vestalis, and Diadromus collaris) that parasitize the diamondback moth Plutella xylostella using Illumina and Pacbio sequencing platforms. Genome assembly using SOAPdenovo produced a 178 Mb draft genome for C. vestalis and a 399 Mb draft genome for D. collaris. A total set that contained 11,278 and 15,328 protein-coding genes for C. vestalis and D. collaris, respectively, were predicted using evidence (homology-based and transcriptome-based) and de novo prediction methodology. Phylogenetic analysis showed that the braconid C. vestalis and the ichneumonid D. collaris diverged approximately 124 million years ago. These two wasps exhibit gene gains and losses that in some cases reflect their shared life history as parasitic wasps and in other cases are unique to particular species. Gene families with functions in development, nutrient acquisition from hosts, and metabolism have expanded in each wasp species, while genes required for biosynthesis of some amino acids and steroids have been lost, since these nutrients can be directly obtained from the host. Both wasp species encode a relative higher number of neprilysins (NEPs) thus far reported in arthropod genomes while several genes encoding immune-related proteins and detoxification enzymes were lost in both wasp genomes. CONCLUSIONS: We present the annotated genome sequence of two parasitic wasps C. vestalis and D. collaris, which parasitize a common host, the diamondback moth, P. xylostella. These data will provide a fundamental source for studying the mechanism of host control and will be used in parasitoid comparative genomics to study the origin and diversification of the parasitic lifestyle.

3.
Plants (Basel) ; 8(10)2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31623335

RESUMO

Plant defense peptides represent an important class of compounds active against pathogens and insects. These molecules controlling immune barriers can potentially be used as novel tools for plant protection, which mimic natural defense mechanisms against invaders. The constitutive expression in tomato plants of the precursor of the defense peptide systemin was previously demonstrated to increase tolerance against moth larvae and aphids and to hamper the colonization by phytopathogenic fungi, through the expression of a wealth of defense-related genes. In this work we studied the impact of the exogenous supply of systemin to tomato plants on pests to evaluate the use of the peptide as a tool for crop protection in non-transgenic approaches. By combining gene expression studies and bioassays with different pests we demonstrate that the exogenous supply of systemin to tomato plants enhances both direct and indirect defense barriers. Experimental plants, exposed to this peptide by foliar spotting or root uptake through hydroponic culture, impaired larval growth and development of the noctuid moth Spodoptera littoralis, even across generations, reduced the leaf colonization by the fungal pathogen Botrytis cinerea and were more attractive towards natural herbivore antagonists. The induction of these defense responses was found to be associated with molecular and biochemical changes under control of the systemin signalling cascade. Our results indicate that the direct delivery of systemin, likely characterized by a null effect on non-target organisms, represents an interesting tool for the sustainable protection of tomato plants.

4.
Front Physiol ; 10: 745, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31293434

RESUMO

Beneficial fungi in the genus Trichoderma are among the most widespread biocontrol agents of plant pathogens. Their role in triggering plant defenses against pathogens has been intensely investigated, while, in contrast, very limited information is available on induced barriers active against insects. The growing experimental evidence on this latter topic looks promising, and paves the way toward the development of Trichoderma strains and/or consortia active against multiple targets. However, the predictability and reproducibility of the effects that these beneficial fungi is still somewhat limited by the lack of an in-depth understanding of the molecular mechanisms underlying the specificity of their interaction with different crop varieties, and on how the environmental factors modulate this interaction. To fill this research gap, here we studied the transcriptome changes in tomato plants (cultivar "Dwarf San Marzano") induced by Trichoderma harzianum (strain T22) colonization and subsequent infestation by the aphid Macrosiphum euphorbiae. A wide transcriptome reprogramming, related to metabolic processes, regulation of gene expression and defense responses, was induced both by separate experimental treatments, which showed a synergistic interaction when concurrently applied. The most evident expression changes of defense genes were associated with the multitrophic interaction Trichoderma-tomato-aphid. Early and late genes involved in direct defense against insects were induced (i.e., peroxidase, GST, kinases and polyphenol oxidase, miraculin, chitinase), along with indirect defense genes, such as sesquiterpene synthase and geranylgeranyl phosphate synthase. Targeted and untargeted semi-polar metabolome analysis revealed a wide metabolome alteration showing an increased accumulation of isoprenoids in Trichoderma treated plants. The wide array of transcriptomic and metabolomics changes nicely fit with the higher mortality of aphids when feeding on Trichoderma treated plants, herein reported, and with the previously observed attractiveness of these latter toward the aphid parasitoid Aphidius ervi. Moreover, Trichoderma treated plants showed the over-expression of transcripts coding for several families of defense-related transcription factors (bZIP, MYB, NAC, AP2-ERF, WRKY), suggesting that the fungus contributes to the priming of plant responses against pest insects. Collectively, our data indicate that Trichoderma treatment of tomato plants induces transcriptomic and metabolomic changes, which underpin both direct and indirect defense responses.

5.
Front Physiol ; 10: 813, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31333483

RESUMO

Numerous microbial root symbionts are known to induce different levels of enhanced plant protection against a variety of pathogens. However, more recent studies have demonstrated that beneficial microbes are able to induce plant systemic resistance that confers some degree of protection against insects. Here, we report how treatments with the fungal biocontrol agent Trichoderma atroviride strain P1 in tomato plants induce responses that affect pest insects with different feeding habits: the noctuid moth Spodoptera littoralis (Boisduval) and the aphid Macrosiphum euphorbiae (Thomas). We observed that the tomato plant-Trichoderma P1 interaction had a negative impact on the development of moth larvae and on aphid longevity. These effects were attributed to a plant response induced by Trichoderma that was associated with transcriptional changes of a wide array of defense-related genes. While the impact on aphids could be related to the up-regulation of genes involved in the oxidative burst reaction, which occur early in the defense reaction, the negative performance of moth larvae was associated with the enhanced expression of genes encoding for protective enzymes (i.e., Proteinase inhibitor I (PI), Threonine deaminase, Leucine aminopeptidase A1, Arginase 2, and Polyphenol oxidase) that are activated downstream in the defense cascade. In addition, Trichoderma P1 produced alterations in plant metabolic pathways leading to the production and release of volatile organic compounds (VOCs) that are involved in the attraction of the aphid parasitoid Aphidius ervi, thus reinforcing the indirect plant defense barriers. Our findings, along with the evidence available in the literature, indicate that the outcome of the tripartite interaction among plant, Trichoderma, and pests is highly specific and only a comprehensive approach, integrating both insect phenotypic changes and plant transcriptomic alterations, can allow a reliable prediction of its potential for plant protection.

6.
Pest Manag Sci ; 75(9): 2505-2516, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31207012

RESUMO

BACKGROUND: Potassium ion channels play a critical role in the generation of electrical signals and thus provide potential targets for control of insect pests by RNA interference. RESULTS: Genes encoding the small conductance calcium-activated potassium channel (SK) and the voltage-gated potassium channel (SH) were knocked down in Tribolium castaneum by injection and oral delivery of dsRNA (dsTcSK and dsTcSH, respectively). Irrespective of the delivery mechanism a dose-dependent effect was observed for knockdown (KD) of gene expression and insect mortality for both genes. Larvae fed a 400 ng dsRNA mg-1 diet showed significant gene (P < 0.05) knockdown (98% and 83%) for SK and SH, respectively, with corresponding mortalities of 100% and 98% after 7 days. When injected (248.4 ng larva-1 ), gene KD was 99% and 98% for SK and SH, causing 100% and 73.4% mortality, respectively. All developmental stages tested (larvae, early- and late-stage pupae and adults) showed an RNAi-sensitive response for both genes. LC50 values were lower for SK than SH, irrespective of delivery method, demonstrating that the knockdown of SK had a greater effect on larval mortality. Biosafety studies using adult honeybee Apis mellifera showed that there were no significant differences either in expression levels or mortality of honeybees orally dosed with dsTcSK and dsTcSH compared to control-fed bees. Similarly, there was no significant difference in the titre of deformed wing virus, used as a measure of immune suppression, between experimental and control bees. CONCLUSION: This study demonstrates the potential of using RNAi targeting neural receptors as a technology for the control of T. castaneum. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.


Assuntos
Controle de Insetos/métodos , Proteínas de Insetos/antagonistas & inibidores , Bloqueadores dos Canais de Potássio/metabolismo , Tribolium/efeitos dos fármacos , Animais , Técnicas de Silenciamento de Genes , Larva/efeitos dos fármacos , Larva/genética , Larva/crescimento & desenvolvimento , Pupa/efeitos dos fármacos , Pupa/genética , Pupa/crescimento & desenvolvimento , Interferência de RNA , RNA de Cadeia Dupla/genética , Canais de Potássio Ativados por Cálcio de Condutância Baixa/antagonistas & inibidores , Tribolium/genética , Tribolium/crescimento & desenvolvimento
7.
Struct Dyn ; 6(2): 024304, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31041361

RESUMO

We demonstrate that highly ordered two-dimensional crystals of ligand-capped gold nanoparticles display a local photo-mechanical stiffness as high as that of solids such as graphite. In out-of-equilibrium electron diffraction experiments, a strong temperature jump is induced in a thin film with a femtosecond laser pulse. The initial electronic excitation transfers energy to the underlying structural degrees of freedom, with a rate generally proportional to the stiffness of the material. Using femtosecond small-angle electron diffraction, we observe the temporal evolution of the diffraction feature associated with the nearest-neighbor nanoparticle distance. The Debye-Waller decay for the octanethiol-capped nanoparticle supracrystal, in particular, is found to be unexpectedly fast, almost as fast as the stiffest solid known and observed by the same technique, i.e., graphite. Our observations unravel that local stiffness in a dense supramolecular assembly can be created by van der Waals interactions up to a level comparable to crystalline systems characterized by covalent bonding.

8.
Proc Biol Sci ; 286(1901): 20190331, 2019 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-30991929

RESUMO

The association between the deformed wing virus and the parasitic mite Varroa destructor has been identified as a major cause of worldwide honeybee colony losses. The mite acts as a vector of the viral pathogen and can trigger its replication in infected bees. However, the mechanistic details underlying this tripartite interaction are still poorly defined, and, particularly, the causes of viral proliferation in mite-infested bees. Here, we develop and test a novel hypothesis that mite feeding destabilizes viral immune control through the removal of both virus and immune effectors, triggering uncontrolled viral replication. Our hypothesis is grounded on the predator-prey theory developed by Volterra, which predicts prey proliferation when both predators and preys are constantly removed from the system. Consistent with this hypothesis, we show that the experimental removal of increasing volumes of haemolymph from individual bees results in increasing viral densities. By contrast, we do not find consistent support for alternative proposed mechanisms of viral expansion via mite immune suppression or within-host viral evolution. Our results suggest that haemolymph removal plays an important role in the enhanced pathogen virulence observed in the presence of feeding Varroa mites. Overall, these results provide a new model for the mechanisms driving pathogen-parasite interactions in bees, which ultimately underpin honeybee health decline and colony losses.

9.
PLoS Genet ; 15(3): e1007998, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30835731

RESUMO

Genome sequencing data have recently demonstrated that eukaryote evolution has been remarkably influenced by the acquisition of a large number of genes by horizontal gene transfer (HGT) across different kingdoms. However, in depth-studies on the physiological traits conferred by these accidental DNA acquisitions are largely lacking. Here we elucidate the functional role of Sl gasmin, a gene of a symbiotic virus of a parasitic wasp that has been transferred to an ancestor of the moth species Spodoptera littoralis and domesticated. This gene is highly expressed in circulating immune cells (haemocytes) of larval stages, where its transcription is rapidly boosted by injection of microorganisms into the body cavity. RNAi silencing of Sl gasmin generates a phenotype characterized by a precocious suppression of phagocytic activity by haemocytes, which is rescued when these immune cells are incubated in plasma samples of control larvae, containing high levels of the encoded protein. Proteomic analysis demonstrates that the protein Sl gasmin is released by haemocytes into the haemolymph, where it opsonizes the invading bacteria to promote their phagocytosis, both in vitro and in vivo. Our results show that important physiological traits do not necessarily originate from evolution of pre-existing genes, but can be acquired by HGT events, through unique pathways of symbiotic evolution. These findings indicate that insects can paradoxically acquire selective advantages with the help of their natural enemies.


Assuntos
Evolução Molecular , Transferência Genética Horizontal/genética , Larva/imunologia , Vespas/imunologia , Animais , Hemolinfa/imunologia , Hemolinfa/virologia , Larva/genética , Larva/virologia , Filogenia , Proteômica , Simbiose/genética , Simbiose/imunologia , Vespas/genética , Vespas/virologia
10.
Viruses ; 10(4)2018 03 30.
Artigo em Inglês | MEDLINE | ID: mdl-29601473

RESUMO

Any attempt to outline a logical framework in which to interpret the honey bee health decline and its contribution to elevated colony losses should recognize the importance of the multifactorial nature of the responsible syndrome and provide a functional model as a basis for defining and testing working hypotheses. We propose that covert infections by deformed wing virus (DWV) represent a sword of Damocles permanently threatening the survival of honey bee colonies and suggest that any factor affecting the honey bee’s antiviral defenses can turn this pathogen into a killer. Here we discuss the available experimental evidence in the framework of a model based on honey bee immune competence as affected by multiple stress factors that is proposed as a conceptual tool for analyzing bee mortality and its underlying mechanisms.


Assuntos
Abelhas/imunologia , Colapso da Colônia , Modelos Imunológicos , Animais , Abelhas/microbiologia , Abelhas/parasitologia , Abelhas/virologia , Inseticidas , Microbiota , Neonicotinoides , Vírus de RNA/fisiologia , Simbiose , Varroidae/fisiologia
11.
Insect Biochem Mol Biol ; 95: 26-32, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29559251

RESUMO

Polydnaviruses (PDV) are viral symbionts associated with ichneumonid and braconid wasps parasitizing moth larvae, which are able to disrupt the host immune response and development, as well as a number of other physiological pathways. The immunosuppressive role of PDV has been more intensely investigated, while very little is known about the PDV-encoded factors disrupting host development. Here we address this research issue by further expanding the functional analysis of ankyrin genes encoded by the bracovirus associated with Toxoneuron nigriceps (Hymenoptera, Braconidae). In a previous study, using Drosophila melanogaster as experimental model system, we demonstrated the negative impact of TnBVank1 impairing the ecdysone biosynthesis by altering endocytic traffic in prothoracic gland cells. With a similar approach here we demonstrate that another member of the viral ank gene family, TnBVank3, does also contribute to the disruption of ecdysone biosynthesis, but with a completely different mechanism. We show that its expression in Drosophila prothoracic gland (PG) blocks the larval-pupal transition by impairing the expression of steroidogenic genes. Furthermore, we found that TnBVank3 affects the expression of genes involved in the insulin/TOR signaling and the constitutive activation of the insulin pathway in the PG rescues the pupariation impairment. Collectively, our data demonstrate that TnBVANK3 acts as a virulence factor by exerting a synergistic and non-overlapping function with TnBVANK1 to disrupt the ecdysone biosynthesis.


Assuntos
Anquirinas/metabolismo , Ecdisona/biossíntese , Regulação da Expressão Gênica , Himenópteros/virologia , Polydnaviridae/metabolismo , Proteínas Virais/metabolismo , Animais , Anquirinas/genética , Drosophila melanogaster , Ecdisona/genética , Polydnaviridae/genética , Proteínas Virais/genética
12.
Protein Sci ; 27(3): 620-632, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29168260

RESUMO

Prosystemin, originally isolated from Lycopersicon esculentum, is a tomato pro-hormone of 200 aminoacid residues which releases a bioactive peptide of 18 aminoacids called Systemin. This signaling peptide is involved in the activation of defense genes in solanaceous plants in response to herbivore feeding damage. Using biochemical, biophysical and bioinformatics approaches we characterized Prosystemin, showing that it is an intrinsically disordered protein possessing a few secondary structure elements within the sequence. Plant treatment with recombinant Prosystemin promotes early and late plant defense genes, which limit the development and survival of Spodoptera littoralis larvae fed with treated plants.


Assuntos
Lycopersicon esculentum/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/farmacologia , Spodoptera/crescimento & desenvolvimento , Animais , Dicroísmo Circular , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Proteínas Intrinsicamente Desordenadas/química , Proteínas Intrinsicamente Desordenadas/farmacologia , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Lycopersicon esculentum/química , Lycopersicon esculentum/genética , Modelos Moleculares , Ressonância Magnética Nuclear Biomolecular , Proteínas de Plantas/metabolismo , Estrutura Secundária de Proteína , Spodoptera/efeitos dos fármacos
13.
Sci Rep ; 7(1): 15522, 2017 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-29138416

RESUMO

Plants actively respond to herbivory by inducing various defense mechanisms in both damaged (locally) and non-damaged tissues (systemically). In addition, it is currently widely accepted that plant-to-plant communication allows specific neighbors to be warned of likely incoming stress (defense priming). Systemin is a plant peptide hormone promoting the systemic response to herbivory in tomato. This 18-aa peptide is also able to induce the release of bioactive Volatile Organic Compounds, thus also promoting the interaction between the tomato and the third trophic level (e.g. predators and parasitoids of insect pests). In this work, using a combination of gene expression (RNA-Seq and qRT-PCR), behavioral and chemical approaches, we demonstrate that systemin triggers metabolic changes of the plant that are capable of inducing a primed state in neighboring unchallenged plants. At the molecular level, the primed state is mainly associated with an elevated transcription of pattern -recognition receptors, signaling enzymes and transcription factors. Compared to naïve plants, systemin-primed plants were significantly more resistant to herbivorous pests, more attractive to parasitoids and showed an increased response to wounding. Small peptides are nowadays considered fundamental signaling molecules in many plant processes and this work extends the range of downstream effects of this class of molecules to intraspecific plant-to-plant communication.


Assuntos
Comunicação Autócrina/genética , Regulação da Expressão Gênica de Plantas/imunologia , Lycopersicon esculentum/metabolismo , Peptídeos/genética , Imunidade Vegetal/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Sequência de Aminoácidos , Animais , Comunicação Autócrina/imunologia , Ontologia Genética , Herbivoria/fisiologia , Larva/fisiologia , Lycopersicon esculentum/genética , Lycopersicon esculentum/imunologia , Lycopersicon esculentum/parasitologia , Anotação de Sequência Molecular , Peptídeos/síntese química , Peptídeos/imunologia , Folhas de Planta/genética , Folhas de Planta/imunologia , Folhas de Planta/parasitologia , Proteínas de Plantas/classificação , Proteínas de Plantas/imunologia , Receptores de Reconhecimento de Padrão/genética , Transdução de Sinais , Spodoptera/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/imunologia , Transcrição Genética , Compostos Orgânicos Voláteis/imunologia , Compostos Orgânicos Voláteis/metabolismo
14.
Sci Rep ; 7(1): 13446, 2017 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-29044138

RESUMO

Clothianidin is a widely used neonicotinoid insecticide, which is a potent agonist of the nicotinic acetylcholine receptor in insects. This neurotoxic compound has a negative impact on insect immunity, as it down-regulates the activation of the transcription factor NF-κB. Given the evolutionary conserved role of NF-κB in the modulation of the immune response in the animal kingdom, here we want to assess any effect of Clothianidin on vertebrate defense barriers. In presence of this neonicotinoid insecticide, a pro-inflammatory challenge with LPS on the human monocytic cell line THP-1 results both in a reduced production of the cytokine TNF-α and in a down-regulation of a reporter gene under control of NF-κB promoter. This finding is corroborated by a significant impact of Clothianidin on the transcription levels of different immune genes, characterized by a core disruption of TRAF4 and TRAF6 that negatively influences NF-κB signaling. Moreover, exposure to Clothianidin concurrently induces a remarkable up-regulation of NGFR, which supports the occurrence of functional ties between the immune and nervous systems. These results suggest a potential risk of immunotoxicity that neonicotinoids may have on vertebrates, which needs to be carefully assessed at the organism level.


Assuntos
Guanidinas/efeitos adversos , Sistema Imunitário/efeitos dos fármacos , Sistema Imunitário/metabolismo , Inseticidas/efeitos adversos , Neonicotinoides/efeitos adversos , Transdução de Sinais/efeitos dos fármacos , Tiazóis/efeitos adversos , Biomarcadores , Linhagem Celular , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Sistema Imunitário/imunologia , NF-kappa B/genética , NF-kappa B/metabolismo , Transcriptoma , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismo
15.
J Insect Physiol ; 101: 73-81, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28694149

RESUMO

The host regulation process has been widely investigated in endophagous parasitoid wasps, which in most cases finely interact with living hosts (i.e. koinobiont parasitoids). In contrast, only very limited information is available for ectophagous parasitoids that permanently paralyze and rapidly suppress their victims (i.e. idiobiont parasitoids). Here we try to fill this research gap by investigating the host regulation by Bracon nigricans, an ectophagous idiobiont wasp species. Parasitism, mainly by venom action, is able to redirect host metabolism in order to enhance its nutritional suitability for the developing parasitoid larvae and to provide the required metabolic support to host tissues. The observed alterations of the host titers of haemolymph proteins, carbohydrates and acylglycerols are associated with a parasitoid-induced mobilization of nutrients stored in the fat body. This tissue undergoes a controlled degradation mediated by a close surface interaction with haemocytes, where a cathepsin L activity is localized, as demonstrated by immunolocalization, biochemical and transcriptional data. B. nigricans parasitism does not markedly influence the survival of haemocytes, even though a persistent suppression of the immune competence is observed in parasitized hosts, which show a reduced capacity to encapsulate and melanize non-self objects. These immune alterations likely allow a more efficient food uptake and use by the ectophagous larvae. The obtained results indicate that the host regulation process in basal lineages of parasitic Hymenoptera is more complex than expected and shares functional similarities with adaptive strategies occurring in derived koinobiont species.


Assuntos
Interações Hospedeiro-Parasita , Spodoptera/parasitologia , Vespas/fisiologia , Animais , Imunidade Inata , Larva/crescimento & desenvolvimento , Larva/parasitologia , Larva/fisiologia , Spodoptera/crescimento & desenvolvimento , Spodoptera/imunologia , Spodoptera/metabolismo , Vespas/crescimento & desenvolvimento
16.
Struct Dyn ; 4(4): 044032, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28713841

RESUMO

Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 105 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect). Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons.

17.
Insect Sci ; 24(6): 1025-1033, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28475289

RESUMO

Many fungal root symbionts of the genus Trichoderma are well-known for their beneficial effects on agronomic performance and protection against plant pathogens; moreover, they may enhance protection from insect pests, by triggering plant resistance mechanisms. Defense barriers against insects are induced by the activation of metabolic pathways involved in the production of defense-related plant compounds, either directly active against herbivore insects, or exerting an indirect effect, by increasing the attraction of herbivore natural enemies. In a model system composed of the tomato plant, the aphid Macrosiphum euphorbiae and the parasitoid Aphidius ervi, plant metabolic changes induced by Trichoderma harzianum and their effects on higher trophic levels have been assessed. T. harzianum T22 treatments induce a primed state that upon aphid attacks leads to an increased attraction of aphid parasitoids, mediated by the enhanced production of volatile organic compounds (VOCs) that are known to induce Aphidius ervi flight. Transcriptome sequencing of T22-treated plants infested by aphids showed a remarkable upregulation of genes involved in terpenoids biosynthesis and salicylic acid pathway, which are consistent with the observed flight response of A. ervi and the VOC bouquet profile underlying this behavioral response.


Assuntos
Afídeos/fisiologia , Lycopersicon esculentum/microbiologia , Trichoderma/fisiologia , Compostos Orgânicos Voláteis , Vespas/fisiologia , Animais , Afídeos/parasitologia , Feminino , Voo Animal , Herbivoria , Interações Hospedeiro-Parasita , Lycopersicon esculentum/genética , Simbiose
18.
Proc Natl Acad Sci U S A ; 113(34): 9486-91, 2016 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-27506800

RESUMO

Bacillus thuringiensis is a widely used bacterial entomopathogen producing insecticidal toxins, some of which are expressed in insect-resistant transgenic crops. Surprisingly, the killing mechanism of B. thuringiensis remains controversial. In particular, the importance of the septicemia induced by the host midgut microbiota is still debated as a result of the lack of experimental evidence obtained without drastic manipulation of the midgut and its content. Here this key issue is addressed by RNAi-mediated silencing of an immune gene in a lepidopteran host Spodoptera littoralis, leaving the midgut microbiota unaltered. The resulting cellular immunosuppression was characterized by a reduced nodulation response, which was associated with a significant enhancement of host larvae mortality triggered by B. thuringiensis and a Cry toxin. This was determined by an uncontrolled proliferation of midgut bacteria, after entering the body cavity through toxin-induced epithelial lesions. Consequently, the hemolymphatic microbiota dramatically changed upon treatment with Cry1Ca toxin, showing a remarkable predominance of Serratia and Clostridium species, which switched from asymptomatic gut symbionts to hemocoelic pathogens. These experimental results demonstrate the important contribution of host enteric flora in B. thuringiensis-killing activity and provide a sound foundation for developing new insect control strategies aimed at enhancing the impact of biocontrol agents by reducing the immunocompetence of the host.


Assuntos
Bacillus thuringiensis/patogenicidade , Proteínas de Bactérias/biossíntese , Endotoxinas/biossíntese , Proteínas Hemolisinas/biossíntese , Proteínas de Insetos/antagonistas & inibidores , Microbiota/imunologia , Controle Biológico de Vetores/métodos , Spodoptera/imunologia , Animais , Bacillus thuringiensis/crescimento & desenvolvimento , Clostridium/crescimento & desenvolvimento , Clostridium/patogenicidade , Produtos Agrícolas/parasitologia , Regulação da Expressão Gênica , Hemócitos/imunologia , Hemócitos/microbiologia , Imunidade Inata , Imunossupressão , Proteínas de Insetos/genética , Proteínas de Insetos/imunologia , Intestinos/imunologia , Intestinos/microbiologia , Larva/genética , Larva/imunologia , Larva/microbiologia , Interferência de RNA , RNA de Cadeia Dupla/genética , RNA de Cadeia Dupla/metabolismo , Serratia/crescimento & desenvolvimento , Serratia/patogenicidade , Spodoptera/genética , Spodoptera/microbiologia
19.
Proc Natl Acad Sci U S A ; 113(12): 3203-8, 2016 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-26951652

RESUMO

Honey bee colony losses are triggered by interacting stress factors consistently associated with high loads of parasites and/or pathogens. A wealth of biotic and abiotic stressors are involved in the induction of this complex multifactorial syndrome, with the parasitic mite Varroa destructor and the associated deformed wing virus (DWV) apparently playing key roles. The mechanistic basis underpinning this association and the evolutionary implications remain largely obscure. Here we narrow this research gap by demonstrating that DWV, vectored by the Varroa mite, adversely affects humoral and cellular immune responses by interfering with NF-κB signaling. This immunosuppressive effect of the viral pathogen enhances reproduction of the parasitic mite. Our experimental data uncover an unrecognized mutualistic symbiosis between Varroa and DWV, which perpetuates a loop of reciprocal stimulation with escalating negative effects on honey bee immunity and health. These results largely account for the remarkable importance of this mite-virus interaction in the induction of honey bee colony losses. The discovery of this mutualistic association and the elucidation of the underlying regulatory mechanisms sets the stage for a more insightful analysis of how synergistic stress factors contribute to colony collapse, and for the development of new strategies to alleviate this problem.


Assuntos
Abelhas/imunologia , Ácaros/fisiologia , Simbiose , Animais , Abelhas/parasitologia , Abelhas/virologia
20.
Nano Lett ; 16(4): 2705-13, 2016 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-26918756

RESUMO

The design and the characterization of functionalized gold nanoparticles supracrystals require atomically resolved information on both the metallic core and the external organic ligand shell. At present, there is no known approach to characterize simultaneously the static local order of the ligands and of the nanoparticles, nor their dynamical evolution. In this work, we apply femtosecond small-angle electron diffraction combined with angular cross-correlation analysis, to retrieve the local arrangement from nanometer to interatomic scales in glassy aggregates. With this technique we study a two-dimensional distribution of functionalized gold nanoparticles deposited on amorphous carbon. We show that the dodecanethiol ligand chains, coating the gold cores, order in a preferential orientation on the nanoparticle surface and throughout the supracrystal. Furthermore, we retrieve the dynamics of the supracrystal upon excitation with light and show that the positional disorder is induced by light pulses, while its overall homogeneity is surprisingly found to transiently increase. This new technique will enable the systematic investigation of the static and dynamical structural properties of nanoassembled materials containing light elements, relevant for several applications including signal processing and biology.

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