Nav: Home

How plants defend themselves

April 11, 2019

Like humans and animals, plants defend themselves against pathogens with the help of their immune system. But how do they activate their cellular defenses? Researchers at the Technical University of Munich (TUM) have now discovered that receptors in plant cells identify bacteria through simple molecular building blocks.

"The immune system of plants is more sophisticated than we thought," says Dr. Stefanie Ranf from the Chair of Phytopathology of the TU Munich. Together with an international research team, the biochemist has discovered substances that activate plant defense.

Until now, scientists have thought that plant cells - similar to those of humans and animals - recognize bacteria through complex molecular compounds, for example from the bacterial cell wall. In particular, certain molecules composed of a fat-like part and sugar molecules, lipopolysaccharides or LPS for short, were suspected of triggering an immune response.

In 2015, Ranf's team successfully identified the respective receptor protein: lipo-oligosaccharide-specific reduced elicitation, or LORE for short. All experiments indicated that this LORE protein activates the plant cell's immune system when it detects LPS molecules from the cell wall of certain bacteria.

A throwback leads to the right track

"The surprise came when we wanted to study this receptor protein more closely," recalls Ranf. "Our goal was to find out how LORE distinguishes different LPS molecules. For this we needed high-purity LPS. "

The researchers found that only LPS samples with certain short fatty acid constituents triggered plant defense. Surprisingly, they found in all these active LPS samples also extremely strong adhering free fatty acid molecules. Only after months of experimentation was the team able to separate these free fatty acids from the LPS.

"When we finally succeeded in producing highly purified LPS, it became apparent that the plant cell did not respond to them at all! Thus, it was clear that the immune response is not triggered by LPS, but instead by these short fatty acids" said Ranf.

Targeting bacteria building blocks

The 3-hydroxy fatty acids are very simple chemical building blocks compared to the much larger LPS. They are indispensable for bacteria and are produced in large quantities for incorporation into diverse cellular components.

"The strategy of plant cells to identify bacteria through these basic building blocks is extremely sophisticated; the bacteria require these 3-hydroxy fatty acids and therefore cannot bypass the immune response," summarizes Ranf.

Fitness program for plants

In the future, these results could help in breeding or genetically engineering plants with an improved immune response. It is also conceivable that plants treated with 3-hydroxy fatty acids would have increased resistance to pathogens.
-end-
The work was performed by an international and interdisciplinary collaboration of plant molecular biologists, chemists, and microbiologists. In addition to the Chair of Phytopathology and the Chair of Food Chemistry and Molecular Sensory Science of TUM, the Research Center Borstel (Leibniz Lung Center), the Helmholtz Zentrum München, the Austrian Gregor Mendel Institute for Molecular Plant Biology, the University of Maryland / USA, and the French University of Reims Champagne-Ardenne were involved in this work.

Stefanie Ranf's research was funded by the German Research Foundation (DFG) as part of the Collaborative Research Center (SFB) 924 and the Emmy Noether Program.

Publication:

Bacterial medium chain 3-hydroxy fatty acid metabolites trigger immunity in Arabidopsis plants

Alexander Kutschera, Corinna Dawid, Nicolas Gisch, Christian Schmid, Lars Raasch, Tim Gerster, Milena Schäffer, Elwira Smakowska-Luzan, Youssef Belkhadir, A. Corina Vlot, Courtney E. Chandler, Romain Schellenberger, Dominik Schwudke, Robert K. Ernst, Stéphan Dorey, Ralph Hückelhoven, Thomas Hofmann, Stefanie Ranf

Science, April 12, 2019 - DOI: 10.1126/science.aau1279

Technical University of Munich (TUM)

Related Immune System Articles:

Immune system upgrade
Theoretically, our immune system could detect and kill cancer cells.
Using the immune system as a defence against cancer
Research published today in the British Journal of Cancer has found that a naturally occurring molecule and a component of the immune system that can successfully target and kill cancer cells, can also encourage immunity against cancer resurgence.
First impressions go a long way in the immune system
An algorithm that predicts the immune response to a pathogen could lead to early diagnosis for such diseases as tuberculosis
Filming how our immune system kill bacteria
To kill bacteria in the blood, our immune system relies on nanomachines that can open deadly holes in their targets.
Putting the break on our immune system's response
Researchers have discovered how a tiny molecule known as miR-132 acts as a 'handbrake' on our immune system -- helping us fight infection.
Decoding the human immune system
For the first time ever, researchers are comprehensively sequencing the human immune system, which is billions of times larger than the human genome.
Masterswitch discovered in body's immune system
Scientists have discovered a critical part of the body's immune system with potentially major implications for the treatment of some of the most devastating diseases affecting humans.
How a fungus can cripple the immune system
An international research team led by Professor Oliver Werz of Friedrich Schiller University, Jena, has now discovered how the fungus knocks out the immune defenses, enabling a potentially fatal fungal infection to develop.
How the immune system protects us against bowel cancer
Researchers from Charité - Universitätsmedizin Berlin have discovered a protective mechanism which is used by the body to protect intestinal stem cells from turning cancerous.
How herpesviruses shape the immune system
DZIF scientists at the Helmholtz Zentrum München have developed an analytic method that can very precisely detect viral infections using immune responses.
More Immune System News and Immune System Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Accessing Better Health
Essential health care is a right, not a privilege ... or is it? This hour, TED speakers explore how we can give everyone access to a healthier way of life, despite who you are or where you live. Guests include physician Raj Panjabi, former NYC health commissioner Mary Bassett, researcher Michael Hendryx, and neuroscientist Rachel Wurzman.
Now Playing: Science for the People

#544 Prosperity Without Growth
The societies we live in are organised around growth, objects, and driving forward a constantly expanding economy as benchmarks of success and prosperity. But this growing consumption at all costs is at odds with our understanding of what our planet can support. How do we lower the environmental impact of economic activity? How do we redefine success and prosperity separate from GDP, which politicians and governments have focused on for decades? We speak with ecological economist Tim Jackson, Professor of Sustainable Development at the University of Surrey, Director of the Centre for the Understanding of Sustainable Propserity, and author of...
Now Playing: Radiolab

An Announcement from Radiolab