Plants Have An Immune System…And It’s Complicated

Resisting pathogens — plant immunity.

(June 21, 2018) - Fresh insights into the sophisticated immune system of plants amounts to a new field of discovery that could deliver the next generation of disease-resistant crops.

The prospect is outlined by researchers at The Sainsbury Laboratory (TSL) in an article that challenges an enduring and highly-influential model established in the mid-20th century.

American plant pathologist Harold Henry Flor proposed the “gene-for-gene” hypothesis that explains how particular varieties of plants can resist certain races of plant killers (parasites).

Now, more than 75 years later, scientists from TSL based in Norwich, UK, describe how Flor’s model is superseded by a more complex view of pant immunity.

In a Perspective article published in the journal Science, the team reviewed recent scientific literature to conclude that the plant molecules that act as sensors of invading parasites typically work together to form networks. These networks are more complex than the interaction matrix proposed by Flor.

We knew little about how plant immune sensors work. Recent work shows that these plant sensors interact with each other to bring about a more robust and effective immune response.” says Chih-hang Wu, the first author of the article.

Youssef Belkhadir, a plant biologist at the Gregor Mendel Institute in Vienna, Austria, who wasn’t associated with the article but has published some of the most influential papers on the topic, says: “the network feature of immune receptors enables the plant to integrate multiple stimuli from the environment and deliver an optimal response. It’s the plant version of the fight or flee response.

Indeed, given that plants are typically rooted to the ground and can’t run away from attack, they have developed an intricate network of molecules that is very effective at detecting and fending off attacking parasites.

These networks enable plants to detect and resist pathogens more effectively. First, networks are more robust and can still function even when one of the components fails. Second, networks enable plants to mount an optimal immune response when the environmental conditions are changing. Finally, networks are more plastic and can evolve more rapidly to keep up with the fickle pathogens that are continuously morphing into new virulent races.

This network view of plant immunity has implications for plant breeding. If we can understand better how immune systems work, we can make plants more resistant to disease, and produce food without using as much pesticides as we do today.

Lida Derevnina, an author of the study, added “an improved understanding of plant immune systems could enable optimal use and deployment of disease resistance in agriculture. We lose much of our crops to pathogens. The fundamental knowledge we have acquired can directly guide new strategies of plant breeding.

The authors conclude that a new field, studying plant immune receptor networks, is emerging.

Sophien Kamoun, the senior author of the paper, says “Harold Flor’s model has been hugely insightful and effective in guiding both applied and basic research. But moving forward, we need to capture the full complexity of plant immune systems to advance knowledge and deliver the next generation of disease resistant crops.

New field emerging — plant immune receptor networks.