Williams, Trevor

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https://academica-e.unavarra.es/handle/2454/50181

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Williams

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Trevor

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Producción Agraria

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1173239

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2621

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2013 - 20192
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Has files: true × Subject: Spodoptera frugiperda multiple nucleopolyhedrovirus ×

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    PublicationOpen Access
    Expression of a peroral infection factor determines pathogenicity and population structure in an insect virus
    (Public Library of Science, 2013) Simón de Goñi, Oihane; Williams, Trevor; Cerutti, Martine; Caballero Murillo, Primitivo; López Ferber, Miguel; Nekazaritza Ekoizpena; Producción Agraria; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
    A Nicaraguan isolate of Spodoptera frugiperda multiple nucleopolyhedrovirus is being studied as a possible biological insecticide. This virus exists as a mixture of complete and deletion genotypes; the latter depend on the former for the production of an essential per os transmission factor (pif1) in coinfected cells. We hypothesized that the virus population was structured to account for the prevalence of pif1 defector genotypes, so that increasing the abundance of pif1 produced by a cooperator genotype in infected cells would favor an increased prevalence of the defector genotype. We tested this hypothesis using recombinant viruses with pif1 expression reprogrammed at its native locus using two exogenous promoters (egt, p10) in the pif2/pif1 intergenic region. Reprogrammed viruses killed their hosts markedly faster than the wild-type and rescue viruses, possibly due to an earlier onset of systemic infection. Group success (transmission) depended on expression of pif1, but overexpression was prejudicial to group-specific transmissibility, both in terms of reduced pathogenicity and reduced production of virus progeny from each infected insect. The presence of pif1-overproducing genotypes in the population was predicted to favor a shift in the prevalence of defector genotypes lacking pif1-expressing capabilities, to compensate for the modification in pif1 availability at the population level. As a result, defectors increased the overall pathogenicity of the virus population by diluting pif1 produced by overexpressing genotypes. These results offer a new and unexpected perspective on cooperative behavior between viral genomes in response to the abundance of an essential public good that is detrimental in excess.
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    PublicationOpen Access
    Post-mortem incubation influences occlusion body production in nucleopolyhedrovirus-infected larvae of Spodoptera frugiperda
    (Elsevier, 2019) Ramírez-Arias, Fernando G.; Lasa, Rodrigo; Murillo Pérez, Rosa; Navarro de la Fuente, Laura; Mercado, Gabriel; Williams, Trevor; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
    The inefficient production of nucleopolyhedrovirus occlusion bodies (OBs) can limit the commercialization of virus-based insecticides. The production of OBs in SfMNPV-infected Spodoptera frugiperda fourth instars was compared among groups of larvae that were frozen (−20 °C) immediately following death, or subjected to a 9-day period of post-mortem incubation at 5 °C or 15 °C. Incubation at 15 °C resulted in a ∼40% increase in total OB production and OBs per mg larval weight, compared to the −20 °C and 5 °C treatments. OBs from the 5 °C treatment were ∼10% smaller in cross sectional area and small OBs (<1 µm 2 ) were more abundant than in other treatments, possibly due to reduced post-mortem OB maturation in this treatment. SfMNPV genomic DNA in OB samples was 3.6-fold higher in the −20 °C treatment than the 5 °C treatment and 1.7-fold higher than the 15 °C treatment, possibly due to differences in the exposure of viral genomes to degradative enzymes. However, these differences did not affect the concentration-mortality relationship or speed of kill of OBs from the different treatments. The abundance of aerobic microbes increased from ∼3 × 10 7 CFU/ml in the −20 °C treatment, to approximately 2 × 10 8 and 3 × 10 8 CFU/ml in the 5 °C and 15 °C incubation treatments, respectively, similar to levels seen in other nucleopolyhedroviruses produced in insects. We conclude that post-mortem incubation at 15 °C likely involves continuing processes of virion occlusion and OB maturation that increase overall OB production without loss of insecticidal activity, although the value of this step in commercial virus insecticide production will depend on the cost of the incubation step and the value of the additional OBs produced.