The MITE family Heartbreaker (Hbr): Molecular markers in maize

Transposable elements are ubiquitous in plant genomes, where they frequentl y comprise the majority of genomic DNA, The maize genome, which is believed to be structurally representative of large plant genomes, contains single genes or small gene islands interspersed with much longer blocks of retrotr ansposons. Given this organization, it would be desirable to identify molec ular markers preferentially located in genic regions. In this report, the f eatures of a newly described family of miniature inverted repeat transposab le elements (MITEs) (called Heartbreaker), including high copy number and p olymorphism, stability, and preference for genic regions, have been exploit ed in the development of a class of molecular markers for maize. To this en d, a modification of the AFLP procedure called transposon display was used to generate and display hundreds of genomic fragments anchored in Hbr eleme nts. An average of 52 markers were amplified for each primer combination te sted. In all, 213 polymorphic fragments were reliably scored and mapped in 100 recombinant inbred lines derived from a cross between the maize inbreds B73 x Mo17. In this mapping population, Hbr markers are distributed evenly across the 10 maize chromosomes. This procedure should be of general use i n the development of markers for other MITE families in maize and in other plant and animal species where MITEs have been identified.