Because maize has served as a model plant for basic genetics research for the last 100 years, the completion of its genome sequence has important implications for basic research--as already evidenced by the immediate publication of the two companion papers in Science. In addition, the November 20, 2009 issue of PLoS Genetics features an editorial on the new maize sequence and ten more companion studies--each of which either provides background information on the development of the maize sequence or uses the new maize sequence to produce additional insights into maize genetics. In addition to advancing research on maize, the maize genome sequence is also expected to advance other cereal genome sequencing projects, such as those for wheat and barley.
A daunting task
The maize sequencing project, which was initiated in 2005, is a notable achievement because it was completely quickly and because the maize genome is among the most challenging genomes sequenced to date. The complexity of the maize genome is partly due to its size: with 2.5 billion base pairs covering ten chromosomes, the maize genome is almost as big as the human genome. "The maize genome is the largest plant genome sequenced to date," says Wilson.
The complexity of the maize genome is also partly due to the fact that about 85 percent of its DNA is composed of transposable elements--segments of DNA that can move between locations. "Transposable elements are found in all organisms, but were discovered in maize by Nobel Prize winner Barbara McClintock more than 60 years ago," said Rob Martienssen of Cold Spring Harbor Laboratory. "It is a remarkable achievement to be able to visualize these elements in such detail in the genome sequence."
An easy-to-understand explanation of McClintock's discovery and a photo of an ear of corn that was grown by McClintock at Cold Spring Harbor in 1949 are included in an eye-catching poster about maize genetics that accompanies the Science paper announcing the new maize genome.