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Copyright William S. Justice. From USDA, NRCS 1999. The PLANTS database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Makeover Turns Model Plant Genome Into Supermodel OvernightBy Judy McBride
December 14, 2000
On Wednesday, a team of scientists announced the first complete sequence of a plant genome in the latest issue of Nature. In tomorrow’s issue of Science, a group of scientists will announce a computational analysis of the same Arabidopsis genome that makes it more reliable as a genetic model for other plant species.
The findings provide a clearer picture of the ancient history of this model genome. Clarification will allow researchers to compare genes across widely divergent crop species, such as grasses (rice and other grains) and broadleafed plants (soybeans, fruits and vegetables). And this will speed up identification of important genes in crop plants for breeding or genetic engineering programs.
Aligning the genetic maps of crop plants and Arabidopsis--a flowering plant in the mustard family--will provide important insights in comparative plant genomics, according to lead author and evolutionary geneticist Todd J. Vision. He is at the Agricultural Research Service’s Center for Agricultural Bioinformatics in Ithaca, N.Y.
Vision’s co-authors are Daniel G. Brown at the Whitehead Institute/MIT Center for Genome Research and Steven D. Tanksley at Cornell University’s Departments of Plant Breeding and Plant Biology.
Arabidopsis was chosen as a genetic model because its genome is one of the smallest and seemingly one of the simplest among flowering plants. But plant geneticists began finding duplicate sections of chromosomes, suggesting that the genome had doubled at least once during its ancestry. Duplications add to the difficulty of locating related chromosome sections in other plants because the genome gets shuffled--like a deck of cards--naturally over millions of years of evolution.
By applying some novel computations to an almost complete sequence of the Arabidopsis genome, Vision and colleagues found its ancestry to be more complex than suspected. Instead of duplicating only once, the genome has doubled at least four times. And those events occurred between 100 and 200 million years ago, about the time when dinosaurs walked the Earth and before many of our broadleaved crop plants began to diverge from Arabidopsis’ distant ancestor. So evidence of these duplications would be in many of today’s crop genomes.