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Crop Biotech Update

Scientists Map Maize Genome

November 20, 2009

A team of researchers from the US announced that they have sequenced the genome of maize, an achievement that will boost research efforts to develop higher yielding varieties of one of the world's most important crops. The team, composed of more than 150 scientists, reported their findings in this week's issue of Science. They specifically sequenced the genome of an inbred line of maize called B73.

The team identified some 32,000 genes spread across the crop's 10 chromosomes. They also found that more than 85 percent of the genome is composed of transposable genetic elements and that the crop shares 8,494 gene families with Arabidopsis, sorghum and rice. "Just as cytogenetic and genetic maps revolutionized research and crop improvement over the last century, the B73 maize reference sequence promises to advance basic research and to facilitate efforts to meet the world's growing needs for food, feed, energy, and industrial feed stocks in an era of global climate change," the team wrote in the paper.

Maize's 3.2 billion base pair genome has many things to reveal, as evidenced by numerous companion papers published by Science, PLoS Genetics, PNAS and Plant Physiology analyzing everything from transposable genetic elements, maize centromere evolution, characterization of microRNA genes to hybrid vigor and the crop's evolutionary history.

With the B73 maize genome sequence available, researchers have begun sequencing other maize varieties. Luis Herrera-Estrella and colleagues, for instance, sequenced the variety Palomero, a maize from the Mexican highlands, and compared its features to those of the modern inbred line B73. They found that the genome is around 22 percent smaller and contained 20 percent less repetitive DNA. The team also identified several genes, mainly for heavy metal tolerance, that were present in both B73 and Palomero but were absent in the maize ancestor teosinte. Herrera–Estrella and colleagues suggested that environmental factors related to the metal contents of local soils may have been important in maize domestication.

Catherine Feuillet from INRA France and Kellye Eversole, in a perspectives article also published by Science, noted that "[the studies] represent a milestone in genetics and plant biology, as well as the crowning achievement of a group of corn growers and scientists who envisioned changing the world of agriculture."

The B73 maize genome report is available at http://dx.doi.org/10.1126/science.1178534 Herrera-Estrella and colleagues' paper, on the other hand, is available at http://dx.doi.org/10.1126/science.1178437 The companion papers published by Science are accessible at http://dx.doi.org/10.1126/science.1177837 and http://dx.doi.org/10.1126/science.1178294 The companion studies published by the open-access PLoS Genetics is collected at http://collections.plos.org/plosgenetics/maize.php Read the perspectives paper at http://dx.doi.org/10.1126/science.1183463