Many pathogens, whether of plants or animals, export their own proteins in order to modify their local environment and to disable host defenses. Channeling secretory proteins into the molecular machines that allow them to cross membranes generally relies on short amino acid sequence motifs. Oomycetes are deep-branching eukaryotes that include the notorious Phytophthora, which causes devastating diseases such as potato late blight and sudden oak death. Phytophthora colonizes plants by establishing and residing within a membrane-bounded haustorium inside cells.
Bhattacharjee et al. show that Plasmodium and Phytophthora, phylogenetically distant eukaryotic pathogens, use similar host-targeting motifs. Plasmodium has a host-targeting motif that is linked to over 400 virulence factors, which make up the "secretome." Phytophthora possesses virulence determinants that are recognized by plant hosts and, like Plasmodium, the highly conserved leader sequence motif RxLR along with a nearby acidic domain can be found in multiple effectors that are delivered into the host cell cytoplasm. -- CA
PloS Pathol. 2, e50 (2006).
