Pathway to resistance in blight-devastated wheat found

The role that a specific gene plays in developing resistance to the fungal pathogen has been demonstrated by a Chinese-Australian research team.

As climate change causes more humid conditions, the risk of fusarium head blight is increasing. The blight – sometimes called ‘head scab’ – is caused mainly by the fungus Fusarium graminearum.

The disease affects wheat, barley and a range of other cereal crops, causing a ‘bleaching’ of the plant heads. In some cases, it produces toxins that are harmful to vertebrates if consumed.

But not all wheat species are prone to the fungus and a joint investigation by scientists from South Australia’s University of Adelaide and Nanjing Agriculture University in China have identified the process in which a blight-resistant gene works its magic.

The gene, called TaHRC, has previously been shown by Chinese researchers to manufacture a protein that increases susceptibility to fusarium head blight, but a mutation that deletes the beginning of its code renders wheat more resistant to the disease.

The new research published in the journal Cell Host & Microbe digs further into the code of TaHRC – expanding knowledge of the two variants it dubs blight-susceptible, ‘S’, and resistant, ‘R’. These variants influence the way a protein complex within the nucleus condenses: susceptible variants are more condensed, while resistant ones are diffuse.

“Our contribution is, basically, to uncover the molecular activity of the HRC gene, or HRC protein, how it recruits a bunch of other proteins to form a complex, and how this complex helps fight the disease,” Dr Xiujuan Yang, an agricultural scientist at the University of Adelaide, tells Cosmos.

“In HRC-S, it condensates easily compared to HRC-R. And importantly, the mycotoxin from the fungus can trigger the protein condensate for the S version, but not the R version.

“The state [variant] is critical here, in fighting the disease.”

Rather than being a single gene change, the research group points to the role of the protein complex in conferring resistance on certain wheat strains.

“In cells, nothing works alone,” Yang says.

“Sometimes in other plants…  the condensate is actually required for disease resistance. It depends on what disease or proteins are involved.

“In our case here, you actually need a diffused state. In the condensate state, the proteins are ‘trapped’ in the complex and cannot function cannot function properly.”

Identifying the absence of key genes appears to provide resistance to Fusarium graminearum in the HRC-R variant, the researchers note opportunities for breeding new, disease-resistant crops.

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