KAUST Researchers Clone Wheat Rust Resistance Genes

King Abdullah University of Science and Technology (KAUST) researchers have recently achieved a significant milestone in sustainable agriculture. They successfully cloned wheat rust resistance genes Lr9 and Sr43 and discovered that these genes encode unique kinase fusion proteins. Their study sets the stage for innovative solutions to the issue of disease resistance in bread wheat.

Annually, nearly 20% of global wheat production succumbs to pests and disease, losing about 3,500 grain ships. One of the most cost-effective and eco-friendly ways to mitigate this issue is to breed disease-resistant cultivars.

Historically, the wild relatives of wheat have been a rich source of genetic diversity for enhancing crop resilience. For example, the Lr9 leaf rust resistance gene, initially discovered in wild goatgrass (Aegilops umbellate), was incorporated into bread wheat in the 1950s by Dr. Ernest Sears in a landmark experiment. Today, nearly 40% of resistance genes in bread wheat have been introduced from wild relatives over the past six decades. However, this approach can sometimes introduce unfavorable genes from the wild relative, a phenomenon known as “linkage drag.”

KAUST’s Yajun Wang performed long-read sequencing to compare the genomes of an Lr9-containing bread wheat cultivar and Ae. Umbellate. Wang discovered that about 536 other genes from Ae. Umbellate was introduced into wheat along with Lr9, which inadvertently led to the deletion of a small fragment of the wheat genome containing 87 genes.

Following a similar lineage as Lr9, the stem rust resistance gene Sr43 is derived from tall wild wheatgrass (Thinopyrum elongatum).

Simon Krattinger and Brande Wulff led two separate teams at KAUST that successfully cloned Lr9 and Sr43. They used mutant genomes and compared them to the parent genomes. Their research will enable the development of bread wheat lines without linkage drags and facilitate the creation of multigene stacks, potentially offering superior and more durable resistance.

The teams also found that Lr9 and Sr43 encode unusual kinase fusion proteins, gaining recognition for their involvement in disease resistance in wheat and barley.

Their research also suggests that the fusion of these proteins to kinases might improve the host plant’s ability to detect the presence of pathogens and trigger defensive responses, according to Krattinger.

A vital trait of the Sr43 gene is its reduced resistance at elevated temperatures. “Now that we’ve cloned Sr43, we can start decoding its temperature sensitivity’s molecular mechanism. This could allow us to engineer a heat-resistant version better adapted to climate change,” said Wulff.

Read more on the article here, and the article on Sr43 encodes here.