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A Breakthrough in Barley Disease Resistance: Understanding Immune Receptors
Powdery mildew poses a significant threat to barley crops, often leading to losses of as much as 40%. To combat this issue, barley has developed a variety of immune receptors tailored to detect specific proteins, termed effectors, produced by different strains of the powdery mildew fungus.
The successful recognition of these effectors by the immune receptors enhances the plant’s resilience against the disease. Insights from recent research into this complex interaction could empower scientists to bolster the resistance of barley and related species, such as wheat, against this detrimental fungal pathogen.
Researchers from the Max Planck Institute for Plant Breeding Research (MPIPZ) in Cologne, Germany, have utilized advanced techniques to elucidate the structural characteristics of an immune receptor named MLA13 and its interaction with the corresponding fungal effector, AVRA13-1. Their findings are documented in a publication in the EMBO Journal.
Under the guidance of Paul Schulze-Lefert from MPIPZ, Elmar Behrmann from the University of Cologne, and Jijie Chai from Westlake University in Hangzhou, China, the team employed cryogenic electron microscopy (cryo-EM) to capture the structures at a molecular level. Cryo-EM involves cooling samples to extremely low temperatures, thereby entraping biological specimens, including proteins, in a glass-like state of ice, which preserves their structural integrity for detailed analysis.
The atomic resolution of the resulting structure has unveiled the intricate dynamics of how the plant’s immune receptor interacts with the fungal effector while also revealing the configuration of the effector itself.
This breakthrough allowed first author Aaron W. Lawson to modify another immune receptor, MLA7, to better recognize an effector named AVRA7. The architectural similarities between the sequences of MLA immune receptors permitted the researchers to explore whether they could alter MLA7’s specificity for recognition based on insights gained from the MLA13-AVRA13-1 structure. Remarkably, by modifying just a single amino acid in MLA7’s protein sequence, they produced an engineered version that could now recognize both AVRA13-1 and AVRA7.
Traditionally, plant breeding has been characterized by laborious and time-consuming methods to achieve the desired combinations of traits. However, as the powdery mildew fungus rapidly evolves, these conventional techniques struggle to cope with the emergence of new, virulent variants.
The findings from this study underline the potential of using engineered immune receptors to modify or enhance specificity in a precise and timely manner. This innovative approach may offer a promising strategy for safeguarding barley against disease and contributing to global food security.
The genes responsible for MLA immune receptors trace back to a common ancestor within a grass family that includes barley, wheat, oats, and rye. These immune receptors are present across these important cereal crops, with the capacity to also provide protection against other destructive pathogens, such as rust fungi and the rice blast fungus. Consequently, gene editing of MLA receptors holds the potential to fortify multiple staple crops against economically significant diseases.
More information: Aaron W. Lawson et al, The barley MLA13-AVRA13 heterodimer reveals principles for immunoreceptor recognition of RNase-like powdery mildew effectors, The EMBO Journal (2025). DOI: 10.1038/s44318-025-00373-9
Citation: A blueprint for making cereal crops more resistant to fungal disease (2025, February 17) retrieved 17 February 2025 from https://phys.org/news/2025-02-blueprint-cereal-crops-resistant-fungal.html
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