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Abstract Detail

The dynamics of evolution in plant and fungal interactions - from communities to genomes

Moeller, David [1], Tiffin, Peter [2].

Geographic variation in adaptation at the molecular level: pathogenesis-related proteins and plant-fungal interactions in Teosinte.

Plant-enemy interactions, including interactions between plants and fungal pathogens, frequently vary among geographic locations, which can result in spatially-variable selection and local adaptation. Although the molecular genetics of plant responses to invading enemies is increasingly well understood, less is known about the evolutionary dynamics of these genes in space and time. In particular, it is unclear whether geographically-variable selection is consistent or strong enough to influence patterns of nucleotide variation at individual defense loci. We examined patterns of nucleotide diversity and population genetic structure in 16 plant innate immunity genes (pathogenesis-related proteins), involved in plant defense against fungal pathogens and/or insect herbivores. Sequence variation within and among six populations of teosinte, the wild ancestor of maize (Zea mays ssp. parviglumis), was used to test the hypothesis that patterns of population structure and within-population diversity at immunity genes differed from patterns found at (1) non-immunity (reference) loci and (2) from neutral expectations derived from coalescent simulations of structured populations. For the majority of genes that we studied, including genes known to be upregulated in response to fungal pathogens, we did not detect evidence for geographically-variable selection at the molecular level. One gene that functions mainly in defense against insect herbivores exhibited unusually high divergence among populations, unusually low levels of polymorphism within populations, and a novel replacement substitution in the active site of the protein limited to one geographic region. Overall, our results indicate that a signature of local adaptation in pathogenesis-related proteins involved in plant defense may be uncommon. The results of our work are discussed in the context of molecular population genetic studies of plant defense genes in other species and in comparison to genes that function in the detection (R-genes) and signaling components of the plant defense response.

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1 - University of Georgia, Genetics, Davison Life Sciences, Athens, GA, 30602, USA
2 - University of Minnesota, Plant BIology, 1445 Gortner Avenue, Saint Paul, MN, 55108

local adaptation
nucleotide polymorphism
population structure
natural selection.

Presentation Type: Symposium or Colloquium Presentation
Session: SY2
Location: Ballroom 3/Cliff Lodge - Level B
Date: Monday, July 27th, 2009
Time: 11:30 AM
Number: SY2005
Abstract ID:408