It’s not the holy grail of the complete wheat genome, but an international consortium has identified nearly 100,000 genes in the DNA of wheat.
The research and the identification of specific genes, published in the journal Nature in late November, should help wheat breeders develop varieties with increased yield, disease resistance and other desirable traits.
“This work moves us one step closer to a comprehensive and highly detailed genome sequence for bread wheat, which along with rice and maize is one of the three pillars on which the global food supply rests,” Jan Dvorak, professor of plant sciences at the University of California Davis and a co-author of the study, said in a statement.
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“This sequencing effort has yielded important information that will accelerate wheat genetics and breeding and help us better understand wheat evolution.”
A team of scientists from UC Davis, Kansas State University, Cold Spring Harbor Laboratory in New York, the University of Liverpool University of Bristol, the European Bioinformatics Institute and the U.S. Department of Agriculture, collaborated on the research, which sheds light on a piece of wheat’s complex genome.
With 17 billion base pairs, the wheat genome has about five times more DNA than the human genome. It is known as a hexaploid genome because it has six copies of its seven chromosomes. In comparison, the corn genome, which has already been decoded, has two billion base pairs of DNA. Bases are chemical units represented in the genetic code by the letters T, C, G and A.
The team of scientists behind the Nature paper noted this is only a step towards the full wheat genome, but Curt McCartney, a cereal genetics specialist with Agriculture Canada in Winnipeg, said the discovery is significant.
Using a technique called shotgun sequencing, the scientists identified 94,000 to 96,000 genes and found 132,000 single nucleotide polymorphisms (SNIPs) within the wheat genome. A SNIP, or a change in the sequence of letters in a genome, is the most common type of genetic variation.
“A SNIP is a type of DNA marker. When we’re doing our genetic studies, we need markers to track the inheritance of different pieces of the chromosome,” McCartney said from his office at the Cereal Research Centre in Winnipeg.
“So if you’re looking at the same region of the genome, in two different (wheat) varieties, a SNIP marker between those two varieties would constitute a single change in a single base. So you’d have a G in one parent and a C in another parent.”
Wheat genetic experts like McCartney will use the SNIPs to pinpoint regions on wheat’s DNA associated with particular traits, such as resistance to leaf rust.
Scientists have already mapped disease resistance genes in certain regions of wheat’s chromosome, but they often don’t know precisely which gene is responsible for the desirable trait.
“The addition of all these markers is very helpful when you’re actually trying to get to the actual gene that’s encoding a particular trait that you’re interested in,” McCartney said.
The research team is continuing its efforts to decode the plant’s complex genome.
“While we and our collaborators continue to work to enhance the resolution of our knowledge of the wheat genome, these results should have a significant impact on breeding efforts and further research studies of the wheat genomes,” said Richard McCombie, a genetics expert at the Cold Spring Harbor Laboratory and one of the lead authors of the paper.
McCartney said it may take another five to 10 years to decode wheat’s entire genome because it is so large and intricate.
“Ultimately, once that’s developed, that’s a resource you can take forward forever (to) study all these economically important traits,” he said.
“Right now, you’re basically struggling a bit in the dark when you’re trying to identify genes that are controlling traits.”
What is the alphabet of DNA?
The code of DNA is written in only four “letters:” A, C, G and T. They stand for the chemical bases adenine (A), guanine (G), cytosine (C) and thymine (T). The bases pair together to form units called base pairs.
The meaning of the DNA code is determined by the sequence of A, T, C and G, similar to how the meaning of a word lies in the sequence of alphabet letters.
With 17 billion base pairs, wheat is five times larger than the human genome and 40 times larger than the rice genome.
Source: Trust Sanger Institute, National Institute of Health and staff research
