wheat genome draft sequence
July 18, 2014

International Consortium Completes Draft Sequence Of The Bread Wheat Genome

redOrbit Staff & Wire Reports - Your Universe Online

An international team of researchers has successfully completed the chromosome-based draft of the bread wheat genome, giving them the first-ever genetic blueprint of the crop grown on over 500 million acres worldwide and used to produce nearly 700 million tons of food annually.

The group, which is known as the International Wheat Genome Sequencing Consortium (IWGSC), managed to produce an ordered draft sequence of the 17-gigabase hexaploid Triticum aestivum genome by sequencing isolated chromosome arms. A paper detailing their findings appears in the latest edition of the journal Science.

While the technical jargon can be intimidating, Rachel Feltman of the Washington Post explained that the discovery could have a drastic impact on the global food supply by allowing scientists to genetically enhance a crop that is known as “one of the most common and versatile” in the world and serves as “the main food staple for a third of the world population.”

While bread wheat is “remarkably good at adapting to change,” Feltman said that “efforts to grow higher yielding, more nutritious and more resilient wheat in the face of population growth and climate change have been slow and stilted for one simple reason. Its genes are a big, complicated mess.”

Scientists have been attempting to determine how the genes of the crop are ordered so that they can more quickly identify specific genes and traits, and it has been a long and arduous process. With the release of this new study, however, the IWGSC is “more than halfway there and that an entire sequence is on the horizon,” she added.

Even though the sequence is only a draft, it provides plant breeders and researchers with the genetic blueprint required to detect specific genes on individual chromosomes throughout the wheat genome, IWGSC collaborator and Kansas State University associate professor of plant pathology Eduard Akhunov explained in a statement Thursday.

“This resource is invaluable for identifying those genes that control complex traits, such as yield, grain quality, disease, pest resistance and abiotic stress tolerance. They will be able to produce a new generation of wheat varieties with higher yields and improved sustainability to meet the demands of a growing world population in a changing environment,” he said, calling the research a “significant advancement for wheat genetics.”

“The wheat genome sequence provides a foundation for studying genetic variation and understanding how changes in the genetic code can impact important agronomic traits,” Akhunov added. “In our lab we use this sequence to create a catalog of single base changes in DNA sequence of a worldwide sample of wheat lines to get insights into the evolution and origin of wheat genetic diversity.”

To put the enormity of their work into perspective, National Geographic reporter Jennifer Frazer explained that the bread wheat genome contains approximately 100,000 genes – five times more than the human genome. However, the true complexity lies not solely in the absolute number of genes it contains, but in knowing how and when those genes are activated, as well as understanding the interaction 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,” said Frazer. “Wheat essentially combines three grasses in one genetic package. While the process is relatively common in plants,” wheat is unusual because “some strains went through polyploidization more than once.”

“Bread wheats retain three subgenomes, each of which represents about 35,000 genes from the three original grass species, and about 80 percent to 90 percent of bread wheat's genome is made up of long, repetitive sequences of 12,000 to 15,000 base pairs. These repeats defy conventional sequencing methods,” she added.

According to Frazer, the IWGSC began the colossal task of mapping the bread wheat genome in 2011, and the paper published this week represents a draft sequence – indicating that all of the genes are understood in the correct order alongside their respective chromosomes, but the orientation of those genes and the sequences of the regions between each of them are still missing. Nonetheless, the work is expected to dramatically decrease how long it takes plant breeders to identify and isolate the specific genes they are most interested in.