Selectable viruses and altered susceptibility mutants in Arabidopsis thaliana.

The genetic basis for susceptibility or nonsusceptibility of plants to viruses is understood poorly. Two selectable tobacco etch virus (TEV) strains were developed for identification of Arabidopsis thaliana mutants with either gain-of-susceptibility or loss-of-susceptibility phenotypes. These strains conferred a conditional-survival phenotype to Arabidopsis based on systemic expression of herbicide resistance or proherbicide sensitivity genes, thereby facilitating mass selections and screens for Arabidopsis mutants that enhance or suppress TEV replication, cell-to-cell movement, or long-distance movement. A multicomponent mechanism that restricts systemic invasion of TEV was identified through isolation of gain-of-susceptibility mutants with alterations at two loci.