EVOLUTIONARY DYNAMICS OF GENE-FOR-GENE SYSTEMS

Summary

Principal Investigator: JOY M BERGELSON
Affiliation: University of Chicago
Country: USA
Abstract: This proposal links the molecular biology of disease genes to the population-level processes that determine the frequencies of these genes and their evolutionary history. The host organism is the plant Arabidopsis thaliana and the pathogen is Pseudomonas viridiflava. The proposal focuses on host loci that affect resistance or susceptibility and pathogen loci that affect virulence (successful infection) or avirulence (unsuccessful infection). The first aim begins with measuring the phenotypic patterns of infection success or resistance for different host plants and pathogen isolates. In each of 10 populations, the investigators will analyze the outcome of infection for 50 pathogen isolates tested against each of 10 host genotypes. Next, three pathogen loci that affect virulence will be cloned. The three loci will be chosen based on their different infection successes when tested against host genotypes that have been well characterized at the sequence level and that provide helpful molecular tools for later analysis. Once the three pathogen loci have been chosen, the investigators will search for three matching loci in the host plant that interact with the pathogen virulence loci. Matching gene-for-gene interactions between plant and pathogen have been frequently observed and are likely to be found in this case. The final step for the first aim measures epidemiological aspects of natural populations. In particular, the investigators will study various natural populations for infection rates, host population densities and migration rates, and patterns of DNA polymorphism in the three host and pathogen loci that have been cloned. The second aim develops mathematical models. These models will be used to formulate hypotheses about how the population biology influences the frequencies of host and pathogen alleles and the pattern of molecular evolution at the cloned loci. The models emphasize how epidemiological processes of infection frequency and spread of disease influence aspects of gene frequency and molecular evolution. The third aim will use the data generated to estimate parameters of the mathematical models. Estimates include rates of epidemiological spread of disease, the fitness differences between plants that have or lack particular resistance alleles (cost of resistance), the fitness differences between pathogens that have or lack alleles that allow them to attack particular plant genotypes (costs of virulence), migration rates between populations, and the effects of environment (e.g., humidity) and host density on rates of pathogen transmission. The fourth aim uses the parameter estimates to expand the mathematical models and to study various aspects of epidemiology and evolution. For example, if weather has a significant impact on transmission, then that factor will be incorporated into the epidemiological components of the model. The model will be tested in the sense that the investigators will search for consistent explanations for how observed patterns of polymorphism, molecular evolution, and epidemiology fit together. For example, the epidemiology along with costs of resistance and virulence allow estimates for tendency of allele frequencies to fluctuate over time. The tendency of allele frequencies to fluctuate has, in turn, consequences for the expected patterns of molecular evolution. Thus, the investigators can use a particular aspect of their data to estimate processes such as the tendency of allele frequencies to fluctuate. They can then use their estimate of allele frequency fluctuations to make testable predictions about observable patterns, such as the distribution of nucleotide polymorphisms.
Funding Period: 2001-03-01 - 2006-02-28
more information: NIH RePORT

Top Publications

  1. pmc Cheating, trade-offs and the evolution of aggressiveness in a natural pathogen population
    Luke G Barrett
    Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
    Ecol Lett 14:1149-57. 2011
  2. pmc Impact of initial pathogen density on resistance and tolerance in a polymorphic disease resistance gene system in Arabidopsis thaliana
    Fabrice Roux
    Department of Ecology and Evolution, University of Chicago, 1101 E 57th Street, Chicago, IL 60637, USA
    Genetics 185:283-91. 2010
  3. ncbi Variation in resistance and virulence in the interaction between Arabidopsis thaliana and a bacterial pathogen
    Erica M Goss
    Department of Ecology and Evolution, University of Chicago, 1101 E 57th Street, Chicago, Illinois 60637, USA
    Evolution 60:1562-73. 2006
  4. ncbi Fitness consequences of infection of Arabidopsis thaliana with its natural bacterial pathogen Pseudomonas viridiflava
    Erica M Goss
    Department of Ecology and Evolution, University of Chicago, 1101 E 57th Street, Chicago, IL 60637, USA
    Oecologia 152:71-81. 2007
  5. ncbi The role of pectate lyase and the jasmonic acid defense response in Pseudomonas viridiflava virulence
    Katrin Jakob
    Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago 60637, USA
    Mol Plant Microbe Interact 20:146-58. 2007
  6. pmc Molecular evolution of pathogenicity-island genes in Pseudomonas viridiflava
    Hitoshi Araki
    Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA
    Genetics 177:1031-41. 2007

Scientific Experts

Detail Information

Publications6

  1. pmc Cheating, trade-offs and the evolution of aggressiveness in a natural pathogen population
    Luke G Barrett
    Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
    Ecol Lett 14:1149-57. 2011
    ..These results suggest that niche differentiation can contribute to the maintenance of virulence polymorphisms, and that both within-host and between-host growth rates modulate cheating and cooperation in P. syringae populations...
  2. pmc Impact of initial pathogen density on resistance and tolerance in a polymorphic disease resistance gene system in Arabidopsis thaliana
    Fabrice Roux
    Department of Ecology and Evolution, University of Chicago, 1101 E 57th Street, Chicago, IL 60637, USA
    Genetics 185:283-91. 2010
    ..Genetic variation for tolerance was also found within the S and R natural accessions, suggesting the potential for selection to act upon this important trait...
  3. ncbi Variation in resistance and virulence in the interaction between Arabidopsis thaliana and a bacterial pathogen
    Erica M Goss
    Department of Ecology and Evolution, University of Chicago, 1101 E 57th Street, Chicago, Illinois 60637, USA
    Evolution 60:1562-73. 2006
    ....
  4. ncbi Fitness consequences of infection of Arabidopsis thaliana with its natural bacterial pathogen Pseudomonas viridiflava
    Erica M Goss
    Department of Ecology and Evolution, University of Chicago, 1101 E 57th Street, Chicago, IL 60637, USA
    Oecologia 152:71-81. 2007
    ..Underlying these average effects we observed both negative and positive effects of infection, and variation in both fitness among plant genotypes and sensitivity to environmental conditions...
  5. ncbi The role of pectate lyase and the jasmonic acid defense response in Pseudomonas viridiflava virulence
    Katrin Jakob
    Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago 60637, USA
    Mol Plant Microbe Interact 20:146-58. 2007
    ..viridiflava virulence on A. thaliana and found that pectate lyase activity is correlated with virulence, whereas the removal of pectate lyase or HrpL significantly reduced virulence...
  6. pmc Molecular evolution of pathogenicity-island genes in Pseudomonas viridiflava
    Hitoshi Araki
    Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA
    Genetics 177:1031-41. 2007
    ..Evolutionarily stable PAIs may be preferable in this species because preexisting genetic variation enables P. viridiflava to respond rapidly to natural selection...