Minireview Maize DNA-sequencing strategies and genome organization Ron J Okagaki and Ronald L Phillips Address: Department of Agronomy and Plant Genetics, and Center for Plant and Microbial Genomics, The University of Minnesota, St. Paul, MN 55108, USA. Correspondence: Ron J Okagaki. E-mail: okaga002@ comment reviews Published: 16 April 2004 Genome Biology 2004, 5:223 The electronic version of this article is the complete one and can be found online at © 2004 BioMed Central Ltd reports Abstract A large amount of repetitive DNA complicates the assembly of the maize genome sequence. Genome-filtration techniques, such as methylation-filtration and high-CoT separation, enrich gene sequences in genomic libraries. These methods may. | Minireview Maize DNA-sequencing strategies and genome organization Ron J Okagaki and Ronald L Phillips Address Department of Agronomy and Plant Genetics and Center for Plant and Microbial Genomics The University of Minnesota St. Paul MN 55108 USA. Correspondence Ron J Okagaki. E-mail okaga002@ Published 16 April 2004 Genome Biology 2004 5 223 The electronic version of this article is the complete one and can be found online at http 2004 5 5 223 2004 BioMed Central Ltd Abstract A large amount of repetitive DNA complicates the assembly of the maize genome sequence. Genome-filtration techniques such as methylation-filtration and high-CoT separation enrich gene sequences in genomic libraries. These methods may provide a low-cost alternative to whole-genome sequencing for maize and other complex genomes. The maize and human genomes have similar sizes 2 500 and 3 200 megabases respectively and contain large amounts of repetitive sequence 1 2 . But differences between the two genomes create unique challenges. The available data suggest that most maize repetitive sequences accumulated in the past six million years 3 . This means that they should be more conserved than human repetitive sequences most of which are over 25 million years old 2 . Plant genes including maize genes tend to be small Arabidopsis and rice genes average between and 5 kilobases 4-6 whereas human genes average about 27 kilobases 2 . Identifying genes may therefore be easier in maize but whole-genome sequence assembly may prove more difficult because of the degree of conservation of its repetitive sequences. Completion of a draft rice genome sequence 5 7 stimulated discussion on how to proceed with similar efforts for other crops. This discussion is tempered by an awareness of the difficulties to be faced with most crops. Plant genomes are usually large composed largely of repetitive sequences and are often polyploid. The costs of whole-genome sequencing will be .
