V. Pantaleo et al., Synthesis of infectious transcripts of olive latent virus 1: genes required for RNA replication and virus movement, ARCH VIROL, 144(6), 1999, pp. 1071-1079
Genomic RNA of olive latent virus I (OLV-1) contains five open reading fram
es (ORFs) encoding proteins of 23, 82, 8, 6 and 30 (CP) kDa. A full-length
cDNA copy of OLV-1 RNA was prepared and cloned in a low-copy-number vector
(pMUC-19) downstream of or T7 RNA polymerase promoter. Transcripts derived
from this template, denoted pMUC-OLV, were highly infectious when inoculate
d in local and systemic hosts and infected tissues contained virus-like par
ticles. Genes required for replication and virus movement were mapped by si
te-directed and deletion mutogenesis of the pMUC-OLV. ORF1 and ORF2 mutants
were not viable, suggesting that replication requires the 23 and 82 kDa pr
oteins. The 8 and 6 kDa polypeptides were involved in cell-to-cell movement
, since their absence did not interfere with RNA replication but prevented
systemic infection of inoculated plants. Mutant clones in R and S domains o
f the CP gene could replicate, but they did not systemically infect Nicotia
na benthamiana, indicating that the CP gene is required for OLV-1 long-dist
ance translocation. Mutant clones with large deletions in the CP gene were
not viable, probably due to loss of 3'-proximal sequences required for RNA
replication.