Plant perception systems for pathogen recognition and defence

Recognition of and defence against microbial infections are universal adaptations of multicellular organisms. Plants express a sophisticated molecular system for recognition of and response to potentially pathogenic microorganism. Although the environments of plant and animal cells are vastly different and present unique challenges to invading pathogens, the molecular basis of the innate immune response shows remarkable evolutionary conservation in both kingdoms. Even if more cellular components are continually being identified in plants, the mechanism, interactions and responses are only partly understood. Furthermore, most of this research has been performed in the model plant Arabidopsis thaliana and a significant effort will be needed to understand the above processes in crop species and in natural populations. In this review I will describe examples of the best characterized recognition systems in plants, that mediate pathogen perception either through the perception of highly variable and non-essential pathogen molecules or via conserved microbial structures called pathogen associated molecular patterns (PAMPs).