Arabidopsis thaliana genes contributing to differences in the outcome of infection with generalist and specialist strains of Turnip mosaic virus identified by genome-wide association studies

Abstract

Pathogens can be classified as generalists or specialists depending on their host breadth. While generalists are able to successfully infect a wide variety of host species, the host range of specialists is limited to a few related species. Even though generalists seem to gain an advantage due to their wide host range, they usually pay a cost in terms of fitness within each host species (i.e., the jack-of-all trades, master of none). On the contrary, specialists have high fitness within their own host. A highly relevant yet poorly explored question is whether generalist and specialist viruses differ in the way they interact with their hosts gene expression networks. To identify host genetic factors relevant for the infection of specialist or generalist viruses, we undertook a genome-wide association study (GWAS) approach. Four hundred fifty natural accessions of Arabidopsis thaliana were inoculated with turnip mosaic potyvirus strains that were either generalist (TuMV-G) or specialist (TuMV-S). Several disease-related traits have been associated with different sets of host genes for each TuMV strain. While most of the mapped loci were traitor strain-specific, one shared locus was mapped for both strains, a disease resistance TIR-NBS-LRR class protein. Likewise, only one locus was found involved in more than one of the disease-related traits evaluated, a putative cysteine-rich receptor-like protein kinase 20. To validate these results, the corresponding null mutant plants were inoculated with TuMV-G or -S and the outcome of infection was characterized. Author summaryGeneralist and specialist viruses are commonly found in nature, where they have potential for epidemics, and are classified depending on their host breath. In this study we used a genome-wide association study to characterize differences in the genetic basis of both infection strategies from a host perspective. Our experimental setup consisted of 450 accessions of A. thaliana and two strains of TuMV. We found differences in the number of associated genes and their functions in disease-related traits. Results were validated by characterization of viral infections in null mutant plants deficient for a set of the identified genes.