Retrotransposon evolution in diverse plant genomes

Retrotransposon or retrotransposon-like sequences have been reported to be conserved components of cereal centromeres. Here we show that the published sequences are derived from a single conventional wTy3-gypsy family or a no nautonomous derivative. Both autonomous and nonautonomous elements are like ly to have colonized Poaceae centromeres at the time of a common ancestor b ut have been maintained since by active retrotransposition. The retrotransp oson family is also present at a lower copy number in the Arabidopsis genom e, where it shows less pronounced localization. The history of the family i n the two types of genome provides an interesting contrast between "boom an d bust" and persistent evolutionary patterns.