What is it about?
For plants to stay healthy, they need an immune sensor that can recognize diverse pathogens like bacteria and fungi. Scientists have mapped out a complicated landscape of sensing molecules (“NLRs”) with many strategies, from direct recognition of foreign molecules to indirect monitoring through plant symptoms. We developed a simple model based on the physics of protein-protein interactions to explain how molecular networks can form a robust immune sensor and how different networks obey functional trade-offs. We found that the intuitive behavior of molecules competing for binding partners can explain a variety of non-intuitive observations, such as pathogen molecules that interfere with recognition and the way sensing strategies may have been shaped by evolution.
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Why is it important?
The plant immune system is essential for maintaining natural biodiversity as well as agriculture and food security. It’s very complex, however, with hundreds of NLR sensors together providing a surveillance system that initiates immune response upon infection. We know little about the coordination of this system nor how to explain the diversity of its components. We developed a simple model to help organize this complexity. Our model provides insights into how molecular interactions between plant NLRs, plant targets and pathogen effectors combine to regulate immune responses. We explore this modeling framework to better understand why the immune system is composed of components with diverse architectures (such as direct interactions, guarded interactions, decoys and integrated domains) and how the responses of these components are integrated at the system level. The work is important in shedding light on the selective forces that shape the interaction between plant hosts and their pathogens, and in providing a conceptual framework for extrapolating molecular interactions to their consequence for physiology, ecology and evolution.
Perspectives
Research on the functioning and regulation of plant immunity has revealed exquisite complexity at almost every level. This work has proved enlightening in providing simple, principled explanations for several well-known phenomena. The history of science is filled with examples where bewildering complexity was tamed by a simple, quantitative model, from Newton’s replacement of epicycles to Landau’s theory of phase transitions. While raising more questions than it answers, our model takes a modest step in this direction by providing a framework for connecting molecular mechanisms to patterns that we observe at the population level.
Benjamin Weiner
Read the Original
This page is a summary of: A physical model links structure and function in the plant immune system, Proceedings of the National Academy of Sciences, June 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2502872122.
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