Plant pararetroviruses: interactions of cauliflower mosaic virus with plants and insects

- A virus associated protein mediates both virus cell-to-cell movement and insect transmission.
- An insect-stylet-based receptor as viral insect transmission factor.
- A viral protein involved in assembly, storage, translation and counter defense.
- An RNA-based silencing suppressor is described.
- A viral silencing suppressor interferes with the tasiRNA pathway.

Virion associated protein (VAP) binds to the icosahedral capsid of cauliflower mosaic virus (CaMV) - a plant pararetrovirus. The interactive coiled-coil domains of this protein can interact with the coiled-coils of either the movement protein or the aphid transmission factor, thereby mediating both cell-to-cell movement and aphid transmission. The host counters CaMV infection with two lines of defense: innate immunity and silencing. The viral protein 'transactivator/viroplasmin' (TAV) is recognized as an effector and either initiates the innate immunity reaction in a non-permissive host or interferes with it in a permissive host. As a silencing suppressor, TAV interferes with dicing of dsRNAs.