The Interplay Of Centromeric Retrotransposons With Their Host Genome

Maize centromeres contain centromere-specific retrotransposons (CR) and variable amounts of the tandem repeat CentC.  The role of these repeats in centromere function has not yet been fully characterized, but recent in vitro evidence indicates that both repeats preferentially bind nucleosomes containing the centromeric histone H3 variant CENH3 over canonical nucleosomes. CRM elements target their insertion to the functional centromere regions of the host genome, and we recently discovered tandem repeats derived from extant CRM elements.  Taken together, these data suggest that the tandem centromere repeats that are common to plant centromeres may be derived from retrotransposons with characteristics similar to CR elements.  The documented ability of CR elements to generate more active variants by recombination provides a mechanism by which these elements might adapt to changing requirements for centromere compatibility over evolutionary time.