PLANT SCIENCES: Recognition at a Distance -- Schulze-Lefert and Bieri 308 (5721): 506 -- Science:
A key step in the evolution of eukaryotic immune systems was the ability to discriminate between self and nonself. Evidence suggests that animals and plants independently evolved dedicated and highly variable receptor families for recognition of nonself structures. The outcome of interactions between plants and the pathogenic microbes that invade them largely relies on a repertoire of receptors that serve as a radar system for detecting pathogen-derived nonself molecules. The function and specificity of these receptors were originally defined by genetic studies. Such studies revealed that for plants to recognize their intruders and to mount an effective resistance response, there needed to be a match between a strain-specific pathogen effector and its corresponding plant host resistance (R) gene product (1). Detection of a pathogen effector by a plant R receptor frequently leads to rapid death of plant host cells at sites of attempted invasion as part of the immune response. Most known R genes encode intracellular receptors containing a nucleotide binding site and leucine-rich repeats (LRRs) or membrane-bound surface receptors containing extracellular LRRs (2). Two new studies--by Coaker et al. (3) on page 548 of this issue and by Rooney et al. (4) in this week's Science Express--describe encounters between pathogen-secreted effector molecules and their host targets in Arabidopsis and the tomato (Lycopersicon), respectively. Although this interorganismal molecular liaison has entirely different consequences for the effector target proteins, in both cases, their manipulation holds the key to a better understanding of how plant immune receptors recognize nonself.
How 'bout that?