Identification and characterization of a locus (RTM1) that restricts long-distance movement of tobacco etch virus in Arabidopsis thaliana

Screens of Arabidopsis thaliana for susceptibility to tobacco etch virus (TEV) revealed that each of 10 ecotypes were able to support genome replication and cell-to-cell movement in inoculated leaves. However, only four ecotypes, including C24 and La-er, supported complete infections in which TEV was able to replicate and move from cell to cell and long distances through the vasculature. The rates of cell-to-cell movement of a reporter-tagged TEV strain (TEV-GUS) in inoculated leaves of C24 and Columbia (Col-3) were similar, and infection foci continued to expand in both ecotypes through 10 days post-inoculation. No visible or microscopic hypersensitive or cell death responses were evident in inoculated leaves of Col-3 plants. Infection of neither C24 nor Col-3 plants with TEV-GUS resulted in induction of PR-1a gene expression, which is normally associated with active defence responses and systemic acquired resistance. The genetic basis for the restriction of long-distance movement of TEV-GUS in Columbia was investigated using C24 x Col-3 crosses and backcrosses and using La-er x Col-0 recombinant inbred lines. A dominant locus conditioning the restricted TEV infection phenotype was identified on chromosome I between markers ATEAT1 and NCC1 at approximately 14 cM in both genetic analyses. This locus was designated RTM1 (restricted TEV movement 1). It is proposed that RTM1 mediates a restriction of long-distance movement through a mechanism that differs substantially from those conditioned by the dominant resistance genes normally associated with gene-for-gene interactions.