Cherry leafroll virus infections are affected by a satellite RNA that the virus does not support

Previous research showed that tobacco ringspot virus (TobRV), a member of the nepovirus group, acts as a supporting virus for the 359-nucleotide residue satellite tobacco ringspot virus RNA (STobRV RNA), resulting in STobRV RNA replication and its encapsidation in TobRV coat protein. In some hosts STobRV RNA decreases the yield of TobRV and the severity of TobRV-induced symptoms. We report here that inclusion of STobRV RNA in an inoculum of cherry leafroll virus (CLRV), another nepovirus, prevented the accumulation of CLRV in the inoculated leaves of cowpea (Vigna unguiculata) and caused the symptoms to be less severe than those induced when CLRV was inoculated alone. CLRV spread to, and increased in, uninoculated, developing leaves whether or not it was coinoculated with STobRV RNA. STobRV RNA was not detected in CLRV particles or in extracts of infected tissue from the coinoculated plants, indicating that CLRV does not support STobRV RNA. STobRV RNA strongly interfered with the in vitro translation of the RNAs of CLRV and of cowpea mosaic virus (CPMV). Coinoculation of STobRV RNA and CPMV had no detected effect on infections by CPMV, so inhibition of translation in vitro and of replication in vivo were correlated only for CLRV. Results from a new in vitro assay for proteolytic processing of CLRV polyproteins gave no indication of an effect of STobRV RNA on this reaction. © 1987.Peer reviewe

Restriction of Cherry leafroll and Tomato ringspot virus by a heterologous satellite RNA

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