Infection by a symbiotic polydnavirus induces wasting and inhibits metamorphosis of the mothPseudoplusia includens

Abstract

SUMMARYInsect pathogens and parasites often affect the growth and development of their hosts, but understanding of these processes is fragmentary. Among the most species-rich and important mortality agents of insects are parasitoid wasps that carry symbiotic polydnaviruses (PDVs). Like many PDV-carrying wasps, Microplitis demolitor inhibits growth and pupation of its lepidopteran host, Pseudoplusia includens, by causing host hemolymph juvenile hormone (JH) titers to remain elevated and preventing ecdysteroid titers from rising. Here we report these alterations only occurred if P. includens was parasitized prior to achieving critical weight, and were fully mimicked by infection with only M. demolitor bracovirus (MdBV). Metabolic assays revealed that MdBV infection of pre-critical weight larvae caused a rapid and persistent state of hyperglycemia and reduced nutrient stores. In vitro ecdysteroid assays further indicated that prothoracic glands from larvae infected prior to achieving critical weight remained in a refractory state of ecdysteroid release, whereas infection of post-critical weight larvae had little or no effect on ecdysteroid release by prothoracic glands. Taken together, our results suggest MdBV causes alterations in metabolic physiology, which prevent the host from achieving critical weight. This in turn inhibits the endocrine events that normally trigger metamorphosis.

The Encapsidated Genome of Microplitis demolitor Bracovirus Integrates into the Host Pseudoplusia includens

“…Hosts used in the study were parasitized as third-instar larvae. A single wasp offspring emerges from the host's body on day 7 or 8 to pupate within a silken cocoon, followed by emergence into an adult 4 days later (26). CiE1 cells were cultured in Sf-900 medium (Gibco) supplemented with 5% fetal calf serum (HyClone) (16).…”

Two's a Crowd: Phenotypic Adjustments and Prophylaxis in Anticarsia gemmatalis Larvae Are Triggered by the Presence of Conspecifics

“…Besides mortality, the costs of this interaction may be expressed in different ways, such as a reduction in reproductive fitness, reduced survival or inhibition of metamorphosis as seen in insects (see [2]–[4]). Both empirical and theoretical studies have examined the higher risk of pathogen transmission for insects experiencing high conspecific densities [5]–[8].…”

Lepidopteran transcriptome analysis following infection by phylogenetically unrelated polydnaviruses highlights differential and common responses

“…One of these shared traits is that viruses in both genera encode several multimember gene families, but with exception of the ankyrin domain containing genes (Anks) most gene families are unique to one genus or the other (Espagne et al, 2004;Lapointe et al, 2007;Tanaka et al, 2007;Webb et al, 2006). Yet, a large literature also indicates IVs and BVs infect the same host tissues and have broadly similar effects on host physiology (Beckage and Kanost, 1993;Kroemer and Webb, 2004;Pennacchio and Strand, 2006;Pruijssers et al, 2009;Rodriguez-Perez and Beckage, 2006). Taken together, these patterns suggest that the different gene products IVs and BVs encode either target the same host molecules or they target different host molecules in a given pathway which results in similar alterations in host development and immune defenses.…”