title: Population genetics of duplicated disease-defense genes, hm1 and hm2, in maize (Zea mays ssp. mays L.) and its wild ancestor (Zea mays ssp. parviglumis).
abstract: Plant defense genes are subject to nonneutral evolutionary dynamics. Here we investigate the evolutionary dynamics of the duplicated defense genes hm1 and hm2 in maize and its wild ancestor Zea mays ssp. parviglumis. Both genes have been shown to confer resistance to the fungal pathogen Cochliobolus carbonum race 1, but the effectiveness of resistance differs between loci. The genes also display different population histories. The hm1 locus has the highest nucleotide diversity of any gene yet sampled in the wild ancestor of maize, and it contains a large number of indel polymorphisms. There is no evidence, however, that high diversity in hm1 is a product of nonneutral evolution. In contrast, hm2 has very low nucleotide diversity in the wild ancestor of maize. The distribution of hm2 polymorphic sites is consistent with nonneutral evolution, as indicated by Tajima's D and other neutrality tests. In addition, one hm2 haplotype is more frequent than expected under the equilibrium neutral model, suggesting hitchhiking selection. Both defense genes retain >80% of the level of genetic variation in maize relative to the wild ancestor, and this level is similar to other maize genes that were not subject to artificial selection during domestication.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine 92697, USA.
authors.forename: Liqing
authors.initials: L
authors.lastname: Zhang
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Peek
authors.forename: Detiger
authors.initials: D
authors.lastname: Dunams
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Gaut
mesh_terms: D001203:Ascomycota / Q000472:pathogenicity; D019143:Evolution, Molecular; D014644:Genetic Variation; D010088:Oxidoreductases / Q000235:genetics*; D010940:Plant Proteins; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D003313:Zea mays / Q000201:enzymology / Q000235:genetics* / Q000382:microbiology
chemical_list: D010940:Plant Proteins; C078135:HC toxin reductase, Zea mays; D010088:Oxidoreductases