Recent insights into the evolution of genetic diversity of maize

Evolutionary changes that occur within the maize genome can be divided into two classes: In the protein-coding regions, mutations that survive selective pressure primarily consist of single nucleotide polymorphisms which evolve at a relatively slow rate (10-9 mutations/ bp/generation), and functionally detrimental insertions are strongly selected against. In intergenic regions rapidly evolving (10-4 10-8 mutations/bp/generation) transposon insertions and deletions predominate. While genic single nucleotide changes are expected in part to result in amino acid sequence variants leading to the modification of protein properties (catalytic properties of enzymes, binding constants, etc.), transposable elements and other large insertions and deletions, when functionally relevant, are predicted to be regulatory in nature and may affect gene expression at distances of up to 100 kb away. Here, we discuss recent experimental evidence for massive dynamic changes of maize intergenic regions and the predicted functional consequences of genome diversity within this species.