Wg. Dougherty et al., RNA-MEDIATED VIRUS-RESISTANCE IN TRANSGENIC PLANTS - EXPLOITATION OF A CELLULAR PATHWAY POSSIBLY INVOLVED IN RNA DEGRADATION, Molecular plant-microbe interactions, 7(5), 1994, pp. 544-552
Transgenic Nicotiana tabacum cv. Burley 49 plants were generated that
express the 5' untranslated region of the tobacco etch potyvirus (TEV)
genome ligated to a mutated version of the TEV coat protein gene sequ
ence that rendered it untranslatable. Eight different transgenic plant
lines were analyzed for transgene expression and for resistance to TE
V. Three different responses were noted when the transgenic plant line
s were inoculated with TEV: 1) some were highly resistant, and no viru
s replication occurred; 2) some were susceptible but able to recover f
rom systemic TEV infection; and 3) some were susceptible to TEV infect
ion. Plant tissue displaying the recovery phenotype was analyzed for v
irus replication and transgene expression. Recovered tissue could not
be infected with TEV and had steady-state transgene RNA levels which w
ere five- to eightfold lower than those of unchallenged transgenic pla
nt tissue. Nuclear runoff assays suggested a posttranscriptional reduc
tion in specific RNA levels. The highly resistant and recovery phenoty
pes associated with TEV challenge inoculation and the reduction of ste
ady-state RNA levels in recovered transgenic leaf tissue may be manife
stations of a common mechanism.