Polydnaviridae

Polydnaviridae is a family of viruses that are symbiotically associated with parasitic wasps in the families Ichneumonidae and Braconidae. The viruses are not pathogenic to the wasps, but are required for successful parasitism of the wasps' hosts. The family is divided into two subfamilies, the Bracovirinae and the Ichnovirinae, associated with the Braconidae and Ichneumonidae, respectively.

Life Cycle

The life cycle of Polydnaviridae is unique among viruses. The virus particles are produced only in the female wasp's ovaries, and are injected into the host insect along with the wasp's eggs during oviposition. The virus does not replicate in the host, but the viral genomic DNA is integrated into the host's cells and expresses genes that manipulate the host's immune system and development to the benefit of the developing wasp larvae.

Genomics

The genomes of Polydnaviridae are large and complex, with multiple circular DNA molecules. The number and size of these molecules varies widely among different species. The genomes contain many genes that are not related to any known viral genes, but have similarity to eukaryotic genes, suggesting that they were acquired from the wasp or host genomes.

Evolution

The Polydnaviridae are thought to have evolved from nudiviruses, a group of large DNA viruses that infect insects. The transition from a pathogenic to a symbiotic lifestyle is thought to have involved the integration of the viral genome into the wasp genome, followed by a long period of co-evolution.

See Also

• Virus classification
• Parasitoid wasp
• Endosymbiont

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