Nature Immunol. (2015)

The innate immune system of higher organisms efficiently senses potentially dangerous microbes by detecting foreign, conserved molecular patterns such as flagellin — part of the flagellum present in many bacteria. In both plants and mammals this recognition is achieved by membrane pattern recognition receptors (PRRs). In another example of independent and convergent evolution, Stefanie Ranf and colleagues have identified the sensor for lipopolysaccharide (LPS) in Arabidopsis, which is one component of the outer membrane of Gram-negative bacteria.

LPS is also called an endotoxin because it induces a potent immune response in animals that can lead to septic shock and death. In mammals, it is sensed by the receptor TLR4 — a Nobel Prize winning discovery. The authors isolate a mutant, named lore, in which LPS-induced calcium influx is abolished. The corresponding gene encodes a member of the B-type lectin domain receptor-like kinase subfamily. It confers LPS responsiveness by inducing downstream immune responses, making plants more resistant to bacterial infection, and is responsible for LPS-triggered immunity.

LORE is restricted to the genomes of crucifers, including cabbages, oilseeds and cress. However, when expressed in tobacco it confers LPS sensitivity, confirming that interfamily transfer of PRRs can broaden the range of pathogen detection, like adding more antennas to an air defence radar station, making this strategy of potential interest in crop engineering.