Imma Perfetto
Cosmos science journalist
Plant diseases are a major threat to global food security, causing about 20-30% losses in crop production each year. Climate change is worsening the problem, allowing certain pathogens to persist in new places and evolve faster to overcome plant resistance.
One fungal pathogen has caused epidemics of stem rust disease in wheat across the world. Wheat is a staple food crop estimated to contribute about 20% of dietary calories and proteins worldwide, so finding ways to develop new resistant varieties is critical.
A study in the journal Science reveals the mechanism behind an important new resistance gene (Sr62), with implications for new wheat varieties.
Sr62 was found in a wild relative of wheat and cloned for the first time in 2022 by the same team of researchers, from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.
It encodes a type of protein known as a tandem kinase, named because it is made of 2 proteins physically linked together. When they are in this state, they are inactive.
For this research, the KAUST team collaborated with researchers from Australia’s national science agency CSIRO, who had previously developed a platform that can quickly screen and identify pathogen effectors.
According to Jian Chen from CSIRO Agriculture and Food, co-first author of the study, these are “…small proteins that are secreted by pathogens into plants that can inhibit the plant’s immunity.”
In this case, however, they found that when the pathogen effector binds to the tandem kinase proteins, it releases one of them. This starts an immune response which ultimately kills the infected plant cell, robbing the fungus of nutrients and preventing it from proliferating and going on to infect more.
Importantly, they identified a second gene, known as NLR, which is linked to Sr62 andis essential to triggering this immune response. While the tandem kinase acts as a sensor, the NLR protein acts as an executor to trigger the immune response.
This means that future efforts to engineer wheat with Sr62 resistance to stem rust must ensure both genes are in the plant. Otherwise, says Chen, they cannot function.
As the rapid evolution of pathogens threatens the effectiveness of current resistant genes and makes it even more crucial to find new ones, the study highlights the importance of understanding their function before using them.
“In the future, maybe a lot of different types of resistance genes will be found,” says Chen.
“Understanding how they function, how they transfer their recognition signal to cause immunity, is very important for us to use them.
“If you don’t understand how they function and you use them for breeding, it’s like using them blindly. You don’t know how they work.”
Chen says that pathogens evolve much faster than plants do, so engineering plants to recognise more pathogen effectors can provide broader resistance. The new recognition and activation model in wheat will benefit future breeding efforts to manage disease in wheat, and potentially other crops.
