The genome’s unusual size and form made the sequencing especially difficult for the team led by scientists from Germany, the United States, the Czech Republic, and Canada, they report in today’s Science. The gene map reveals unexpected surprises about the evolution of the crop behind the staff of life.
“It’s always astonishing [that] the number of genes does not directly translate into the complexity of the organism,” said Klaus Mayer, director of genome analytics with the Plant Genome and Systems Biology Group at the Helmholtz Center Munich and one of the leaders of the project.
The genome of bread wheat contains a staggering 100,000 or so genes (the human genome contains roughly 20,000). What determines complexity is not the absolute number of genes, he said, but how and when the genes are activated and the interplay between genes and tissues.
The huge wheat genome can be traced directly to three ancient, closely related grasses that underwent a hybridization process known as “polyploidization,” in which multiple excess copies of genes are passed along to offspring. Wheat essentially combines three grasses in one genetic package. While the process is relatively common in plants (but rare in animals), what’s unusual about wheat is that some strains went through polyploidization more than once.