Virusoid

Definition

Virusoids are subviral particles composed of circular single-stranded RNA that depend on helper viruses for replication. They do not encode proteins and rely entirely on the host's cellular machinery and a helper virus for their lifecycle.

5 Must Know Facts For Your Next Test

1. Virusoids are classified as satellite RNAs since they require a helper virus for replication.
2. Unlike viroids, virusoids need a co-infecting virus to propagate within host cells.
3. The RNA genome of virusoids is circular and single-stranded, similar to viroids.
4. Virusoids do not encode any proteins; their RNA acts solely as a genetic element.
5. They are mostly associated with plant diseases, but their study helps understand RNA-based pathogens in general.

Review Questions

• What distinguishes virusoids from viroids in terms of replication dependency?
• How does the structure of a virusoid's genetic material compare to that of viroids?
• Why are virusoids considered satellite RNAs?

Related terms

Viroid:

An infectious agent composed solely of a short strand of circular, single-stranded RNA without protein coating.

Prion:

An infectious agent consisting of an abnormal form of a protein that can trigger normal proteins in the brain to fold abnormally.

Helper Virus: A virus that provides necessary functions for the replication or transmission of another viral entity such as a satellite or defective virus.