Plant & Animal Genomes XV Conference Plant & Animal Genomes XV ConferenceJanuary 13-17, 2007
Town & Country Convention Center
San Diego, CA
Comprehensive polymorphism data are a prerequisite for the systematic identification of sequence variants affecting phenotypes. In the first part of my talk, I will discuss our efforts to provide a whole genome resource for the study of population level evolutionary processes in an experimentally tractable, multicellular organism, Arabidopsis thaliana. In collaboration with several groups, including Joe Ecker (Salk Institute) and Perlegen Sciences, Inc., we identified up to 1.1 million non-redundant SNPs at various levels of precision. These data allow for the first time a systematic description of the types of genes that harbor major changes (e.g., stop codons or whole gene deletions) in wild populations. Disease resistance (R) genes are found to be the most polymorphic class of genes. Through our work on natural variation, we have also become involved in more general questions of species-wide evolution. To understand the mechanisms underlying nascent incompatibilities, we performed an extensive survey for hybrid incompatibilities within A. thaliana. We identified numerous independent F1 incompatibilities with a range of phenotypically related abnormalities. Each case is attributable to two to three epistatic loci. A common autoimmune mechanism--activation of pathogen responses in the absence of pathogens--underlies the majority of incompatibilities. Detailed characterization of one hybrid interaction identified a disease resistance (R) gene variant as causal for the incompatibility phenotype. Since R genes constitute the fastest evolving gene family in plants, this suggests that such incompatibilities arise frequently as a by-product of natural selection.