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DOI: 10.1101/2022.08.02.502433

Genetic basis of Arabidopsis thaliana responses to infection with naive and adapted isolates of turnip mosaic virus

A.Butkovic T. J. Ellis R. Gonzalez B. Jaegle M. Nordborg S. F. Elena
Plant 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 of Arabidopsis thaliana natural inbred lines for four disease-related traits caused by infection by A. thaliana-naive 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 a Copia transposon 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 to A. thaliana. This increase in symptoms severity was specific for infections with the naive 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.