John Innes Centre Engineers Wheat Immune Receptor to Tackle Blast Fungus Crop Disease
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Scientists at the John Innes Centre, working with Kobe University, have engineered a plant immune receptor that detects effector proteins from two different strains of blast fungus at once, as reported in Science Advances.
The team mapped how receptor decoy domains bind fungal effectors using X-ray crystallography, then used that map to modify the receptor, and tested it in wheat protoplasts (wheat cells with their walls removed).
The aim is to stack several independent recognition systems in one cereal variety, which should be harder for the fungus to overcome, though the work has not yet been shown in whole plants.
A Pathogen That Keeps Adapting
Blast fungus, known scientifically as Magnaporthe oryzae, is described in a report by Global Agriculture as one of the most damaging cereal pathogens in the world. Host-adapted strains, called pathotypes, of the same species cause rice blast, which has long threatened rice production across Asia, and wheat blast, a more recently emerged disease. Wheat blast devastated crops in Brazil in the 1980s before spreading to Bangladesh and Zambia.
The fungus can infect wheat, barley and rice, and it evolves quickly enough to overcome single resistance genes bred into a variety. According to the report, that is how many resistant varieties have historically failed within a few growing seasons of release.
How the Engineered Receptor Works
The team focused on tandem kinase proteins, a class of plant immune receptors. Each carries a built-in decoy domain, in this case one that mimics a heavy metal-associated protein which the fungus normally targets during infection. The decoy is fused to signalling machinery that alerts the plant's immune system. When the fungus deploys a small protein called an effector to disable the decoy, the receptor detects the interference and triggers a defence response.
The researchers used structural biology, including X-ray crystallography, which reveals the atomic-scale, three-dimensional shape of a protein. This allowed them to map how the decoy domains bind to different fungal effectors. The map showed which parts of a domain could be altered without breaking its function. They used that knowledge to build a modified receptor able to bind two distinct effector proteins from different blast pathotypes simultaneously, whereas natural receptors typically bind only one.
The dual specificity was demonstrated in wheat protoplasts, which are wheat cells stripped of their rigid outer wall so that genetic constructs can be introduced and tested quickly in a dish.
Towards Stacked Resistance
Dr Yu and Professor Banfield leading this research describe the result as evidence that these receptors are more programmable than previously understood. That opens the possibility of deliberately stacking resistance rather than waiting for it to arise through breeding and selection. The stated long-term goal is to combine engineered tandem kinase receptors with NLR genes, another class of resistance genes that recognise different types of pathogen signal, in a single variety. A plant carrying several independent, well-characterised recognition systems would be harder for the fungus to defeat through a single mutation, the report says.
The commercial relevance is clearest for wheat. The report notes that wheat blast spread from South America into Bangladesh in 2016 and is considered a significant emerging threat to South Asian wheat production, partly because many South Asian varieties are genetically similar to those found susceptible elsewhere. It adds that the breeding programmes of ICAR and CIMMYT already track the disease as a priority.
Resistance management is a recurring concern across the Fungi sector. Related coverage looks at how fungicide resistance is mapped before it spreads and at a partnership addressing disease resistance in European cereals.
Limitations and the Road Ahead
The research is at an early stage. The dual-specificity receptor has been shown to work only in isolated plant cells in a laboratory dish, not in a growing wheat, barley or rice plant in a glasshouse or field. The researchers describe the next phase as moving the finding from protoplasts into whole plants, and the John Innes Centre said its wheat gene editing and transformation platform will support those experiments.
A commercial variety would then need further years of conventional breeding or gene editing to place the trait in elite, locally adapted lines. That would be followed by regulatory and field testing, which the report says varies significantly by country.
