Dissection of the Molecular Mechanism of Rice Immunity Against Magnaporthe oryzae

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most serious rice diseases. We previously cloned the broad-spectrum R gene Piz-t in rice and its cognate Avr gene AvrPiz-t in M. oryzae. To elucidate the molecular mechanism underlying AvrPiz-t–Piz-t mediated immunity against M. oryzae, we performed a yeast two hybrid screen to identify potential host targets of AvrPiz-t in rice. Among the twelve APIPs (AvrPiz-t Interacting Proteins), APIP6 and APIP10 encode RING-type E3 ligases, and APIP5 is a bZIP-type transcription factor. We demonstrated that AvrPiz-t targets APIP5, APIP6 and APIP10 for the suppression of PAMP-triggered immunity (PTI) in rice. In addition, APIP6 ubiquitinates and degrades OsELF3-2 in rice. We also found that APIP5 positively and APIP10 negatively regulates the accumulation of Piz-t. Interestingly, Piz-t can stabilize APIP5 to prevent necrosis at the necrotrophic stage. Taken together, these results indicate that the fungal effector AvrPiz-t targets multiple rice proteins that play important roles in both PTI and ETI.