Uncovered, the mystery of exchanging genes with wild relatives

The genetic mechanism controlling wheat breeding has been uncovered by a team of scientists at the John Innes Centre.

Wheat plants, like most plants, have a big complex genome that is surprisingly stable but also extremely puzzling.

For over 50 years scientists have been trying to understand how wheat can handle six sets of chromosomes without losing fertility.

Now, a team of scientists led by Professor Graham Moore at the John Innes Centre have finally cracked this mystery, and it could have big implications for agriculture. This breakthrough could help plant breeders who are trying to find ways to breed more valuable crops and produce more food for everyone.

The discovery Graham’s team have made is how the Ph1 region of the wheat genome controls genetic exchange. Ph1 is a part of the wheat genome that prevents incorrect chromosomes exchanging parts with each other.

To be highly fertile and therefore high yielding, wheat must sort its chromosomes into the correct sets, without them incorrectly joining together and exchanging sections of their DNA. Wild relatives of wheat carry very important traits that could make wheat resistance to pests, tolerant to heat or produce more flour, but they cannot be bred into wheat.

When breeding varieties of wheat, matching (homologous) chromosomes can associate and exchange if Ph1 is present, but the chromosomes of wild relatives do not.

Following experiments conducted on developing wheat anthers the team has come up with an explanation of how the Ph1 region works. Their publication in Nature Communications outlines exactly how Ph1 promotes the pairing of homologous chromosomes at specific sites.

If breeders ‘switch-off’ the Ph1 region the chromosomes become heavily rearranged and the plants lose their fertility. What breeders need now, is a way to ‘turn off’ the function of the Ph1 region to allow rearrangement of wheat and wild relative genes and then easily ‘turn it on’ again to prevent the loss of fertility.

“The easier it is for plant breeders to cross wheat with wild relatives, the more likely we are to get the desirable characteristics from those relatives into modern wheat varieties,” said Professor Graham Moore. “This discovery will help breeders, and other researchers along the road to our goal of food security.”

Graham’s team discovered that the proteins produced by the Ph1 region reduce the activity of proteins which bind to the sections of the chromosomes where the DNA exchange occurs. This prevents  genes swapping between chromosomes. The discovery of how these plants stabilise their genomes and protect their fertility could lead to ways for breeders to temporarily ‘turn off’ Ph1.

For over two decades, Graham has been investigating the inner workings of cells and trying to understand how plants reproduce. He now leads a team of scientists who are searching for ways to breed desirable traits such as salt tolerance, drought resistance and disease resistance into wheat. He was recently highlighted in a report by BBSRC, highlighting the impact of publically funded wheat genetics research.

The work Graham is carrying out on wheat not only tackles global food security but could result in new insights into reproduction in mammals. The genes found in the Ph1 region are similar to a set of genes that produce proteins called cyclin-dependent kinases (CDK) that control the cell cycle in humans.

These proteins regulate the replication of cells and can control the structure of chromosomes. They are an extremely important group of proteins that are so well conserved in evolution that when yeast CDKs are replaced with the human version they will still work and allow normal proliferation of the cells.

The research team included Peter Shaw, Azahara Martin and Steve Reader from the John Innes Centre and Dylan Phillips from the Institute of Biological, Environmental and Rural Sciences at Aberystwyth University.

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