Innate Immunity in Plants Goes to the PUB

Every organism has to contend with the risk of infection. To cope, organisms have evolved two types of immune responses: the more recent “adaptive” system, found only in vertebrates; and the more ancient “innate” system, which is present in both plants and animals. Researchers have uncovered remarkable evolutionary conservation of innate immune mechanisms between plants and animals (see the figure). They use similar receptor molecules to sense pathogens, for example, and for immune system signaling. On page 1439 of this issue, Lu et al. (1) detail how one plant cell receptor that senses bacterial flagellin triggers an innate immune response. They describe how the activity of the Arabidopsis flagellin-sensing receptor 2 (FLS2) is attenuated by a posttranslational modification process called ubiquitination and subsequent degradation. The research offers insight into the general workings of innate immunity and shows that FLS2 activity has clear parallels to the activity of Toll-like receptors (TLRs), an important class of innate immune system receptors. It also indicates that genetic modification to enhance disease resistance in plants is a practical possibility.