Bacteria-derived peptidoglycans constitute pathogen-associated molecular patterns triggering innate immunity in
Andrea A Gust1, Raja Biswas, Heike D Lenz
1Center for Plant Molecular Biology, Plant Biochemistry, and Microbial Genetics, University of Tübingen, 72076 Tübingen, Germany. andrea.gust@zmbp.uni-tuebingen.de
The Journal of Biological Chemistry
|September 1, 2007
Summary
Gram-positive bacteria peptidoglycan (PGN) is a novel immune trigger in Arabidopsis plants. This finding reveals convergent evolution of PGN perception systems in plants and animals.
Area of Science:
- Plant immunity
- Microbiology
- Molecular biology
Background:
- Plant immunity relies on recognizing conserved microbial structures called pathogen-associated molecular patterns (PAMPs).
- Existing PAMPs include flagellin and chitin, but the repertoire for Gram-positive bacteria recognition is less understood.
Purpose of the Study:
- To identify novel PAMPs from Gram-positive bacteria that elicit immune responses in Arabidopsis thaliana.
- To investigate the specific molecular components of peptidoglycan responsible for immune activation.
- To compare PGN perception with other PAMPs like chitin and explore evolutionary aspects.
Main Methods:
- Treatment of Arabidopsis thaliana with Staphylococcus aureus-derived peptidoglycan (PGN).
- Monitoring of cellular immune responses including medium alkalinization, calcium influx, nitric oxide, camalexin production, and MAPK activity.
- Gene expression analysis using microarrays to identify PGN-responsive genes.
- Comparative analysis of responses to PGN, fungal chitin, and muramyl dipeptide.
Main Results:
- PGN from Gram-positive bacteria activates key plant immune responses in Arabidopsis, including alkalinization, calcium elevation, nitric oxide, camalexin production, and MAPK activation.
- Microarray analysis revealed significant changes in the transcript levels of 236 genes in response to PGN.
- Arabidopsis perceives the PGN sugar backbone, distinguishing it from fungal chitin perception, and muramyl dipeptide does not elicit a response in plants, unlike in animals.
- PGN-induced immune responses share some similarities with flagellin-induced responses but also exhibit distinct features.
Conclusions:
- Peptidoglycan (PGN) from Gram-positive bacteria represents a novel PAMP in Arabidopsis thaliana, activating conserved plant immune pathways.
- PGN perception in plants relies on recognizing the PGN sugar backbone, indicating a distinct system from animal PGN recognition.
- The findings suggest that PGN recognition systems in plants and animals have evolved independently through convergent evolution, expanding the known repertoire of PAMPs and innate immunity mechanisms.
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