CUCUMBER MOSAIC-VIRUS PROTECTION IN TRANSGENIC TOBACCO PLANTS EXPRESSING MONOMERIC, DIMERIC OR PARTIAL SEQUENCES OF A BENIGN SATELLITE RNA

Transgenic tobacco plants expressing precursor sequences of a complete monomeric, a dimeric and two different partial sequences of a benign cucumber mosaic virus (CMV) satellite RNA have been obtained and their capacity to protect the plants against CMV-1 challenge infection has been investigated and compared. Plants expressing a single copy of the satellite are efficiently protected against CMV-1 infection since viral symptoms do not appear in the infected plants. Satellite perfect dimer-expressing plants are less efficiently protected at the first stages postinoculation than monomer-expressing ones, suggesting that RNA transcripts containing dimers are inefficiently recognized by the CMV replicative machinery. Tobacco plants expressing two different fragments of the same satellite molecule each containing an open reading frame (ORF) with in vitro coding capacity do not show any satellite RNA-related sequence amplification upon infection with CMV-1, but present a short delay of 1 or 2 days in the appearance of viral symptoms that is irrespective of the virus inoculum concentration.