F. Vanderwilk et al., EXPRESSION OF THE POTATO LEAFROLL VIRUS ORF0 INDUCES VIRAL-DISEASE-LIKE SYMPTOMS IN TRANSGENIC POTATO PLANTS, Molecular plant-microbe interactions, 10(2), 1997, pp. 153-159
The role of the open reading frame 0 (ORF0) of luteoviruses in the vir
al infection cycle has not been resolved, although the translation pro
duct (p28) of this ORF has been suggested to play a role in host recog
nition, To investigate the function of the potato leafroll luteovirus
(PLRV) p28 protein, transgenic potato plants were produced containing
the ORF0. In the lines in which the ORF0 transcripts could be detected
by Northern (RNA) analysis, the plants displayed an altered phenotype
resembling virus-infected plants. A positive correlation was observed
between levels of accumulation of the transgenic transcripts and seve
rity of the phenotypic aberrations observed, In contrast, potato plant
s transformed with a modified, untranslatable ORF0 sequence were pheno
typically indistinguishable from wild-type control plants. These resul
ts suggest that the p28 protein is involved in viral symptom expressio
n, Southern blot analysis showed that the transgenic plants that accum
ulated low levels of ORF0 transcripts detectable only by reverse trans
cription-polymerase chain reaction, contained methylated ORF0 DNA sequ
ences, indicating down-regulation of the transgene provoked by the put
atively unfavorable effects p28 causes in the plant cell.