Centromeres: Sequences, structure, and biology

Although technological advances have continued to change the speed, cost, and number of plant genomes sequenced (see Flagel and Blackman 2012, this volume), parts of genomes remain to be sequenced and explored. Even the best-sequenced plant genomes, including Arabidopsis thaliana and rice, are missing 7–8% of their total genomic information (Kaul et al. 2000; Goff et al. 2002; Yu et al. 2002). One chromosomal region not often sequenced in genome projects is the centromere. Centromeres of almost all higher eukaryotes contain large stretches (up to several megabases) of tandemly repeated arrays of satellite DNA and retrotransposons. Such long arrays of highly homogenized repetitive DNA sequences cannot readily be cloned, sequenced, and assembled using the currently available cloning and sequencing technologies.