Evolutionary origin of Venturia canescens virus‐like particles

Abstract

Insect host-parasitoid interactions provide fascinating examples of evolutionary adaptations in which the parasitoid employs a variety of measures and countermeasures to overcome the immune responses of its host. Maternal factors introduced by the female wasps during egg deposition play an important role in interfering with cellular and humoral components of the host's immune defence. Some of these components actively suppress host immune components and some are believed to confer protection for the developing endoparasitoid by rather passive means. The Venturia canescens/Ephestia kuehniella parasitoid-host system is unique among other systems in that the cellular defence capacity of the host remains virtually intact after parasitization. This system raises some important questions that are discussed in this mini-review: If immune protection of the egg and the emerging larva is achieved by surface properties comprising glycoproteins and virus-like particles (VLPs) produced by the female wasp, why is the prophenoloxidase activating cascade blocked in parasitized caterpillars? Another question is the evolutionary origin of these particles, given that the functional role and structural features of V. canescens VLP proteins are more related to cellular proteins than to viruses.

When parasitic wasps hijacked viruses: genomic and functional evolution of polydnaviruses

“…However, there might be a cost to the wasp for the replication of PDVs. Some wasps do not use PDVs at all, and the case of V. canescens [25,100] suggests reversal from PDV use could be possible. In this light, why are PDV genomes so large?…”

Recurrent DNA virus domestication leading to different parasite virulence strategies

“…In the parasitized host, they protect the eggs against encapsulation, an insect immune response involving the engulfment of foreign bodies in a sheath of immune cells. Unlike polydnaviruses, which convey virulence genes, VLPs are devoid of DNA ( 10 , 11 ) and enclose virulence proteins ( 12 ). VLPs do not resemble the particles of known viruses, and a debate about whether these particles are truly of viral origin has raged since the early 1970s ( 12 ).…”

“…Unlike polydnaviruses, which convey virulence genes, VLPs are devoid of DNA ( 10 , 11 ) and enclose virulence proteins ( 12 ). VLPs do not resemble the particles of known viruses, and a debate about whether these particles are truly of viral origin has raged since the early 1970s ( 12 ). We show here that VLPs are clearly of viral origin and consist of virulence proteins wrapped in viral envelopes.…”

Innate immunity: Eggs of Manduca sexta are able to respond to parasitism by Trichogramma evanescens

“…Similarly, transcription of Glov, another antibacterial peptide was suppressed for 2 d after parasitization. It has been shown that several larval parasitoids are able to suppress immune responses of their hosts by injection of viruses, virus-like particles, or venom (Edson et al, 1981;Beckage, 1998;Strand and Pech, 1995;Zhang et al, 2004;Amaya et al, 2005;Reineke et al, 2006). Trichogramma species are known to inject a venom into host eggs (Strand 1986;Strand and Pech, 1995) that might suppress some host immune reactions.…”