Plant immune receptors perceive microbial molecules and
initiate an array of biochemical responses that are effective
against most invaders. The role of the plant immune system in
detecting and controlling pathogenic microorganism has been
well described. In contrast, much less is known about plant
immunity in the context of the wealth of commensals that inhabit
plants. Recent research indicates that, just like pathogens,
commensals in the plant microbiome can suppress or evade host
immune responses. Moreover, the plant immune system has an
active role in microbiome assembly and controls microbial
homeostasis in response to environmental variation. We propose
that the plant immune system shapes the microbiome, and that
the microbiome expands plant immunity and acts as an
additional layer of defense against pathogenic organisms
