De novo emergence of a novel satellite RNA of cucumber mosaic virus following serial passages of the virus derived from RNA transcripts.

Satellite RNA (satRNA) is often associated with cucumber mosaic virus (CMV); however, its origin remains unexplained and a subject for speculation. We passaged progeny of molecularly cloned CMV-Fny and CMV-LS in Nicotiana tabacum cv. Ky 14 under greenhouse conditions. A satRNA emerged after at least eight successive transfers of CMV-Fny, but no satRNA was recovered after eleven serial transfers of CMV-LS under the same conditions. The sequences of the newly emerged satRNA were determined, and an infectious cDNA clone was synthesized. Comparison of the sequences of the newly emerged satRNA with those of known CMV satRNAs showed that it is unique. This observation raises interesting questions regarding the enigmatic nature of the origin of CMV satRNAs.