The genome of bread wheat, which has an unusual form and size, has been decoded by an international team of scientists, revealing surprises on the grass-turned-crop's evolution.
The cultivation of wheat has long been viewed as an important factor in the rise of human civilization.
The work of the team of scientists, with the United States, Canada, Germany, and the Czech Republic represented, was published in the Science journal.
"It's always astonishing [that] the number of genes does not directly translate into the complexity of the organism," said Helmholtz Center Munich's Plant Genome and Systems Biology Group genome analytics director Klaus Mayer. Mayer is one of the leaders of the project.
There are roughly an unprecedented 100,000 genes in bread wheat genome, compared to only 20,000 genes in the human genome. However, Mayer said that the complexity within a genome is not how many genes there are, but when and how the genes are activated and the interaction between the genes and the organism's tissues.
The genes in the bread wheat genome elevated to that staggering number because of "polyploidization," which is a hybridization process which passes along multiple excess gene copies from the parents to their offspring. The wheat genome is the result of the polyploidization of three ancient, related kinds of grass, combining the three species into a single genetic package.
Polyploidization is rare in animals but commonly seen in plants. However, what makes the case if wheat unusual is that some strains within the genome underwent more than one instance of polyploidization. This resulted into three subgenomes for bread wheat, with each subgenome representing about 35,000 genes acquired from the original three species of ancient grass.
About 80 percent to 90 percent of the genome of bread wheat is composed of sequences of base pairs numbering between 12,000 to 15,000 which are long and repeated, which goes against normal sequencing methods.
Mayer said that it was the size and complexity of the bread wheat genome that made decoding it take a long time. The project on mapping out the genome began three years ago in 2011.
While mapping the genome of bread wheat took so long, the result is still a "draft" sequence, which means that the team has placed all the genome's genes in the right order along the right chromosomes, but the orientation of the genes and the order of the regions in between the genes are still missing.
While the result is still a "draft" genome, the team expects that it can be used to drastically reduce the time needed for the identification and isolation of genes of interest for plant breeders, such as genes that provide resistance for stress, heat, disease and insects.
