Genetic basis ofArabidopsis thalianaresponses to infection with naïve and adapted isolates of turnip mosaic virus

Abstract

SummaryPlant viruses account for enormous agricultural losses worldwide, and the most effective way to combat them is to identify genetic material conferring plant resistance to these pathogens. Aiming to identify genetic associations with responses to infection, we screened a large panel ofArabidopsis thaliananatural inbred lines for four disease-related traits caused by infection byA. thaliana-naïve and -adapted isolates of the natural pathogen turnip mosaic virus (TuMV). We detected a strong, replicable association in a 1.5 Mb region on chromosome 2 with a 10-fold increase in relative risk of systemic necrosis. The region contains several plausible causal genes as well as abundant structural variation, including an insertion of aCopiatransposon into an TIR-NBS-LRR coding gene, that could be either a driver or a consequence of the disease-resistance locus. When inoculated with TuMV, loss-of-function mutant plants of this gene exhibited different symptoms than wild-type plants, being the magnitude and sign of the difference dependent on the degree of adaptation of the viral isolate toA. thaliana. This increase in symptoms severity was specific for infections with the naïve isolate. Necrosis-associated alleles are found worldwide, and their distribution is consistent with a trade-off between resistance during viral outbreaks and a cost of resistance otherwise, leading to negative frequency-dependent selection.