Recent advances in rice blast effector research

To cause rice blast disease, the fungus Magnaporthe oryzae produces biotrophic invasive hyphae that secrete effectors at the host-pathogen interface. Effectors facilitate disease development, but some (avirulence effectors) also trigger the host's resistance gene-mediated hypersensitive response and block disease. The number of cloned M. oryzae avirulence effector genes has recently doubled, largely based on resequencing with a Japanese field isolate and association of avirulence activity with presence/absence polymorphisms in novel genes for secreted proteins. Effectors secreted by hyphae in rice cells accumulate in biotrophic interfacial complexes, and this property correlates with their translocation across plasma membrane into the rice cytoplasm. Interestingly, the translocated effectors moved into surrounding uninvaded cells, suggesting that effectors prepare host cells before the fungus enters them.