Can this biotech innovation halt the destructive march of a cereal killer?

A UK-led research team has made a significant breakthrough in the fight against the blast fungus, a devastating pathogen that affects cereal crops such as wheat, barley, and rice. The study, published in Science Advances, reveals how recently discovered plant defense receptors could provide broader and more durable immunity against the blast pathogen.

The blast fungus, Magnaporthe oryzae, is responsible for the most severe disease affecting cultivated rice and has now spread to wheat and barley in Asia and Africa. To protect plants from infection, pathogens insert effectors - foreign molecules that manipulate the host and promote disease. Plants have receptors called nucleotide-binding and leucine-rich receptors (NLRs) that recognize these effectors as foreign and trigger an immune response, limiting the pathogen's spread.

However, a new class of intracellular immune receptors called tandem kinase proteins (TKPs) has gained attention in recent years. These TKPs contain an integrated heavy metal-associated (HMA) domain, which has been shown to be crucial for recognizing effectors and mounting an immune response. The HMA domain is important for binding to pathogen effectors, acting as a biological bait to lure them.

In this study, researchers at the John Innes Centre in the UK, in collaboration with Kobe University in Japan, used biophysical analysis and crystallography to reveal the structural interaction between HMA domains and blast pathogen effectors. They demonstrated that HMA domains play a critical role in TKPs by serving as biological baits to attract pathogen effectors.

By understanding this structure, they were able to bioengineer TKP immune receptors with dual specificity - binding to effectors associated with infection of both wheat and barley.

This breakthrough sets the stage for further research into other TKPs in various cereal crops, potentially leading to custom-engineered disease resistance receptors that respond to multiple effectors simultaneously. The team's next step is to translate these findings from surrogate assays (protoplasts, individual wheat cells) to greenhouse plants, aiming to test the effectiveness of these engineered receptors in whole plants.

The fundamental understanding of effector-receptor binding gained from this study could be augmented by advanced technologies such as precision breeding and AI approaches, which could help bioengineer novel specificity into HMA domains. By combining the immune responses of NLRs and TKPs, researchers hope to create more robust immunity in crops, making it harder for pathogens to evolve away from the defense.

This could be particularly important for cereal production in northern Europe, where a changing climate may threaten crops in the future.