Resistance to Turnip crinkle virus in Arabidopsis Conferred by HRT

A single dominant gene, HRT, was identified for HR resistance to TCV. HRT is located on chromosome 5 and encodes a CC-NBS-LRR protein with striking similarity to the RPP8 gene family for resistance to the oomycete Peronospora parasitica. Despite very high sequence similarity, HRT and RPP8 specifically control only their cognate pathogens. Analysis of resistance in HRT-expressing transgenic plants indicated that HRT is necessary but generally insufficient for resistance. About 90% of the HRT-transformed Col-0 plants developed HR and

Expressed PR-1 after TCV infection yet remained susceptible to TCV. Full resistance to TCV required both HRT and a recessive allele rrt. Later experiments demonstrated that the HRT-/rrt-mediated response is dependent on EDS1 and independent of RAR1 and SGT1. In this system, TCV CP is the avirulence determinant recognized by HRT. A host protein, TIP (TCV interacting protein) that belongs to the NAC family of transcriptional activators is known to interact with TCV CP. Although the relevance of this interaction to the mechanism of resistance remains unclear, this interaction apparently functions to keep TIP out of the nucleus.