Plant virus satellites are molecular parasites of plant viruses that rely on a helper virus for replication but do not supply any essential function to the helper virus. They can affect the accumulation of the helper virus and alter the host symptoms induced by the helper virus. They include satellite viruses, satellite ribonucleic acids (RNAs) and satellite deoxyribonucleic acids (DNAs). Size, genome structure and replication strategies vary greatly among plant virus satellites. Some plant virus satellites have been used as biocontrol reagents or as vectors to express exogenous genes. They have also been used as reporters for studying the evolutionary mechanisms of the helper virus.
Key Concept:
Plant virus satellites depend on a helper virus for replication, but they may use different host factors.
Plant virus satellites do not provide any essential function for the helper virus.
Plant virus satellites have varied effects on their helper viruses and hosts, including reduction in virus titer and exacerbation or attenuation of symptoms.
Some plant satellite RNAs use ribozymes to resolve multimers generated during replication.
Satellite DNAs are the symptom determinants in an increasing number of crop diseases caused by geminiviruses.