Mixtures of complete and pif1- and pif2-deficient genotypes are required for increased potency of an insect nucleopolyhedrovirus
Fecha
2009Autor
Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión publicada / Argitaratu den bertsioa
Impacto
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10.1128/jvi.02020-08
Resumen
The insecticidal potency of a nucleopolyhedrovirus population (SfNIC) that infects Spodoptera frugiperda
(Lepidoptera) is greater than the potency of any of the component genotypes alone. Occlusion bodies (OBs)
produced in mixed infections comprising the complete genotype and a deletion genotype are as pathogenic as
the natural population of genotypes from the field. To test whether this incre ...
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The insecticidal potency of a nucleopolyhedrovirus population (SfNIC) that infects Spodoptera frugiperda
(Lepidoptera) is greater than the potency of any of the component genotypes alone. Occlusion bodies (OBs)
produced in mixed infections comprising the complete genotype and a deletion genotype are as pathogenic as
the natural population of genotypes from the field. To test whether this increased potency was due to the
deletion or to some other characteristic of the deletion variant genome, we used the SfNIC-B genome to
construct a recombinant virus (SfNIC-BΔ16K) with the same 16.4-kb deletion as that observed in SfNIC-C and
another recombinant (SfNIC-BΔpifs) with a deletion encompassing two adjacent genes (pif1 and pif2) that are
essential for transmission per os. Mixtures comprising SfNIC-B and SfNIC-B 16K in OB ratios that varied
between 10:90 and 90:10 were injected into insects, and the progeny OBs were fed to larvae in an insecticidal
potency assay. A densitometric analysis of PCR products indicated that SfNIC-B was generally more abundant
than expected in mixtures based on the proportions of OBs used to produce the inocula. Mixtures derived from
OB ratios of 10, 25, or 50% of SfNIC-BΔ16K and the corresponding SfNIC-B proportions showed a significant
increase in potency compared to SfNIC-B alone. The results of potency assays with mixtures comprising
various proportions of SfNIC-B plus SfNIC-BΔpifs were almost identical to the results observed with SfNICB
16K, indicating that deletion of the pif gene region was responsible for the increased potency observed in
mixtures of SfNIC-B and each deletion recombinant virus. Subsequently, mixtures produced from OB ratios
involving 10 or 90% of SfNIC-BΔ16K with the corresponding proportions of SfNIC-B were subjected to four
rounds of per os transmission in larvae. The composition of each experimental mixture rapidly converged to
a common equilibrium with a genotypic composition of ~85% SfNIC-B plus 15% SfNIC-BΔ16K. Nearly
identical results were observed in peroral-passage experiments involving mixtures of SfNIC-B plus SfNICBΔpifs. We conclude that (i) the deletion of the pif1 and pif2 region is necessary and sufficient to explain the
increased potency observed in mixtures of complete and deletion genotypes and (ii) viral populations with
decreased ratios of pif1- and pif2-deficient genotypes in the virus population increase the potency of genotypic
mixtures and are likely to positively influence the transmission of this pathogen. [--]
Materias
Nucleopolyhedrovirus,
Occlusion bodies,
SfNIC-BΔ16K,
SfNIC-BΔpifs
Editor
American Society for Microbiology
Publicado en
Journal of Virology, May 2009, Vol. 83, No. 10, p. 5127–5136
Departamento
Universidad Pública de Navarra. Departamento de Producción Agraria /
Nafarroako Unibertsitate Publikoa. Nekazaritza Ekoizpena Saila /
Universidad Pública de Navarra/Nafarroako Unibertsitate Publikoa. IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Versión del editor
Entidades Financiadoras
This study was funded by MEC project number AGL2005-07909-
CO3-01.