Relocating immune receptors
Q.H. Shen et al., "Nuclear activity of MLA immune receptors links isolate-specific and basal disease–resistance responses," Science, 315:1098–1103, 2007. (Cited in 76 papers)
After staining the nuclei of barley cells, Paul Schulze-Lefert and his colleagues at the Max Planck Institute for Plant Breeding Research in Cologne discovered something unexpected—trace amounts of the cytoplasmic immune protein, mildew A receptor (MLA). They thought it was an artifact, but when they forced all of the MLA out of the nucleus by attaching a nuclear export signal to the protein, the plant was no longer able to stave off infection, indicating that MLA must be in the nucleus in order to function.
"Everyone in the field presumed that these proteins acted in the cytoplasm" rather than the nucleus, says Shulze-Lefert. He suspects that MLA may be "shuttling"...
Using fluorescence lifetime imaging to visualize protein-protein interactions, Shulze-Lefert's team showed that the receptor interacts directly with a genetic repressor in the nucleus to trigger an immune response.
"The field is hot on the trail of generalizing those findings," says Jeffery Dangl of the University of North Carolina at Chapel Hill. "There are 120 to 140 of these [receptors] in Arabidopsis," he says, "but there's no rule to say they have to act the same way."
|Other plant proteins showing nuclear relocation|
|RPS4 receptor in Arabidopsis (Curr Biol, 17:2023–29, 2007)|
|Tobacco N in tobacco plants (PLoS Biol, 5:e68, 2007)|