Plants detect bacterial endotoxin in similar process to mammals

Plants possess an innate immune system that protects them from invading pathogens. Molecular structures that only occur in pathogens enable their recognition and trigger the immune response. Lipopolysaccharide (endotoxin) is one such substance, occurring in the outer membrane of certain bacteria. A team of scientists has now described the first endotoxin immunosensor in plants.

Plants possess an innate immune system equipped with various immunosensors that detect substances occurring only in microorganisms and trigger a defensive reaction. In mammals, for instance, toll-like receptor 4 (TLR4) detects lipopolysaccharide, which is also referred to as endotoxin and is the main component of the outer membrane of many bacterial pathogens.

Since plants also mount an immune response to lipopolysaccharide, the assumption was that they too possess an immunosensor for this substance. The nature of this sensor was previously unknown. Researchers have succeeded in decoding the detection mechanism for bacterial lipopolysaccharide in the model plant Arabidopsis thaliana (thale cress).

The search for the plant's lipopolysaccharide sensor was complicated by the fact that the endotoxin does not consist of a single defined molecule, but of a complex mixture of similar lipopolysaccharide molecules. For that reason, it has also not yet been possible to synthesize it for testing.

For further details see:

Stefanie Ranf, Nicolas Gisch, Milena Schäffer, Tina Illig, Lore Westphal, Yuriy A Knirel, Patricia M Sánchez-Carballo, Ulrich Zähringer, Ralph Hückelhoven, Justin Lee, Dierk Scheel. A lectin S-domain receptor kinase mediates lipopolysaccharide sensing in Arabidopsis thaliana. Nature Immunology, 2015; DOI: 10.1038/ni.3124

Posted by Tim Sandle