Abstract
BackgroundMeiotic recombination is a major source of genetic variation in eukaryotes. The role of recombination in evolution is recognized but little is known about how evolutionary forces affect the recombination pathway itself. Although the recombination pathway is fundamentally conserved across different species, genetic variation in recombination components and outcomes has been observed. Theoretical predictions and empirical studies suggest that changes in the recombination pathway are likely to provide adaptive abilities to populations experiencing directional or strong selection pressures, such as those occurring during species domestication. We hypothesized that adaptive changes in recombination may be associated with adaptive evolution patterns of genes involved in meiotic recombination.ResultsTo examine how maize evolution and domestication affected meiotic recombination genes, we studied patterns of sequence polymorphism and divergence in eleven genes controlling key steps in the meiotic recombination pathway in a diverse set of maize inbred lines and several accessions of teosinte, the wild ancestor of maize. We discovered that, even though the recombination genes generally exhibited high sequence conservation expected in a pathway controlling a key cellular process, they showed substantial levels and diverse patterns of sequence polymorphism. Among others, we found differences in sequence polymorphism patterns between tropical and temperate maize germplasms. Several recombination genes displayed patterns of polymorphism indicative of adaptive evolution.ConclusionsDespite their ancient origin and overall sequence conservation, meiotic recombination genes can exhibit extensive and complex patterns of molecular evolution. Changes in these genes could affect the functioning of the recombination pathway, and may have contributed to the successful domestication of maize and its expansion to new cultivation areas.
Highlights
Meiotic recombination is a major source of genetic variation in eukaryotes
MRE11 and RAD51A were studied in maize before and examined at the functional level [31, 47,48,49]
At least some of the sequence polymorphisms that we found have the potential to cause changes in the functioning of the recombination pathway
Summary
Meiotic recombination is a major source of genetic variation in eukaryotes. The role of recombination in evolution is recognized but little is known about how evolutionary forces affect the recombination pathway itself. The recombination pathway is fundamentally conserved across different species, genetic variation in recombination components and outcomes has been observed. Theoretical predictions and empirical studies suggest that changes in the recombination pathway are likely to provide adaptive abilities to populations experiencing directional or strong selection pressures, such as those occurring during species domestication. To gain more insight into the patterns of recombination gene evolution, we studied sequence polymorphism in genes involved in key steps of the meiotic recombination pathway in maize and teosinte. Theoretical predictions [24] as well as empirical studies [25] indicate that populations experiencing directional or strong selection pressures are likely to evolve increased recombination rates. Selection to alter recombination patterns might leave footprints in sequences of recombination genes To examine this issue, we analyzed patterns of sequence polymorphisms in several genes controlling key steps of meiotic recombination in maize (Fig. 1)
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