Genetic definition and sequence analysis of Arabidopsis centromeres

High-precision genetic mapping was used to define the regions that contain centromere functions on each natural chromosome in Arabidopsis thaliana. Th ese regions exhibited dramatic recombinational repression and contained com plex DNA surrounding large arrays of 180-base pair repeats. Unexpectedly, t he DNA within the centromeres was not merely structural but also encoded se veral expressed genes. The regions flanking the centromeres were densely po pulated by repetitive elements yet experienced normal levels of recombinati on. The genetically defined centromeres were well conserved among Arabidops is ecotypes but displayed Limited sequence homology between different chrom osomes, excluding repetitive DNA. This investigation provides a platform fo r dissecting the role of individual sequences in centromeres in higher euka ryotes.