Viral satellites: parasitic nucleic acids capable of modulating disease expression

Viral satellites are small nucleic acids that can replicate only in conjunction with the nucleic acids of certain viruses in certain hosts. In spite of the absence of any known nucleotide sequence relationships between a viral satellite, its helper virus, and its host, the trilateral interaction that ensues is usually extremely specific. This specificity is often expressed as a highly characteristic modulation of the disease symptom(s) normally associated with a viral presence in a particular host. This opens up very interesting possibilities for the control of viral plant diseases.