Fitness costs of R-gene-mediated resistance in Arabidopsis thaliana.
Resistance genes (R-genes) act as an immune system in plants by recognizing pathogens and inducing defensive pathways. Many R-gene loci are present in plant genomes, presumably reflecting the need to maintain a large repertoire of resistance alleles. These loci also often segregate for resistance and susceptibility alleles that natural selection has maintained as polymorphisms within a species for millions of years. Given the obvious advantage to an individual of being disease resistant, what prevents these resistance alleles from being driven to fixation by natural selection? A cost of resistance is one potential explanation; most models require a lower fitness of resistant individuals in the absence of pathogens for long-term persistence of susceptibility alleles. Here we test for the presence of a cost of resistance at the RPM1 locus of Arabidopsis thaliana. Results of a field experiment comparing the fitness of isogenic strains that differ in the presence or absence of RPM1 and its natural promoter reveal a large cost of RPM1, providing the first evidence that costs contribute to the maintenance of an ancient R-gene polymorphism.
Department of Ecology and Evolution, University of Chicago, 1101 E. 57th Street, Chicago, Illinois 60637, USA.
D
D
Tian
M B
MB
Traw
J Q
JQ
Chen
M
M
Kreitman
J
J
Bergelson
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D017343:Genes, Plant / Q000235:genetics*; D006239:Haplotypes / Q000235:genetics; D007113:Immunity, Innate / Q000235:genetics; D008954:Models, Biological; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012639:Seeds / Q000235:genetics / Q000502:physiology; D012641:Selection, Genetic
D029681:Arabidopsis Proteins; C095014:RPM1 protein, Arabidopsis