A research team led by scientists from the United States, Canada, Germany and the Czech Republic has sequenced the genome of bread wheat. The investigation started in 2011 and took almost three years to be accomplished due to the long sequence of around 100,000 genes. In comparison with the human genetic code of 20,000 units, the genetic code of bread wheat is significantly more complex.
The research results revealed information about evolutionary development that surprised scientists. Klaus Mayer, one of the project leaders, said: “It’s always astonishing [that] the number of genes does not directly translate into the complexity of the organism.” Scientists determined that the complexity of a species depends on when and how activation of genes takes place. Another determining characteristic is the co-action between tissues and genes.
Scientists have been able to identify ancient ancestors of bread wheat and the reasons behind the complexity and longevity of the DNA sequence. The huge genome of the species could be explained by the polyploidization process in which offspring inherits extra copies of the DNA. Plants normally get one copy from each parent, but in case of polyploidy, both zygotes, sperm and egg, receive two copies, which results in tetraploid offspring with four copies of DNA.
The history of the bread wheat species is not limited to tetraploidy. First, two ancient grass species, Aegilops speltoides and Tricium urartu, underwent poliploidization and produced emmer wheat. Later, the rare process repeated again, when the grass Aegilops tauschii hybridized with emmer wheat, which resulted in bread wheat that has six copies of DNA (hexaploid). The history of interbreeding between species explains why the genetic code of bread wheat is so long.
Methods that research scientists used for determining the sequence of the bread wheat genome are called mapping methods. These allows scientists to determine the exact order of genes in a sequence, but does not imply anything about the orientation of genes. However, the obtained information was sufficient to note that genes responsible for the same functions were not redundant, as usually happens. The bread wheat genome has numerous duplicated genes and scientists suppose that this is the trait which allowed the species to be useful in the production of porous and airy white bread.
The obtained DNA sequence draft is expected to allow plant breeders to locate and isolate desired genes more easily and quickly. Plant breeders are interested in genes that improve resistance to stress, climate change and insects. Isolation of a gene previously would take around ten years, but Mayer believes that after the full map of genetic sequence is published, the process will speed up.
Chief Executive of the Biotechnology and Biological Sciences Research Council (BBSRC), Prof. Douglass Kell, explained that sequencing the bread wheat genome is a breakthrough for many scientists because it will improve breeding strategies. Development of new bread wheat species could increase yields and avoid severe crop losses.
The international team of scientists involved in the research has revealed facts valuable for natural selection and evolutionary science by sequencing the genome of bread wheat. The results demonstrated to scientists that hybridization could be more common in nature than people think. Therefore, hybridization of species is a natural process and artificial selection might have a positive effect on evolution in general. Further research on the genetic traits that could improve quality and quantity of various species of wheat is expected.
By Yevgeniya Migranova