Identification And Functional Analysis Of Magnaporthe Oryzae Effectors Targeting To The Host Nucleus

Rice blast disease, caused by the fungus Magnaporthe oryzae, is one of the most severe diseases of cultivated rice worldwide and impacts global food security. Successful infection of rice plants by M. oryzae requires sequential development of specialized infection structures, including appressoria for initial penetration, and infectious hyphae formed inside epidermal cells. It was hypothesized that invasive hyphae secrete effector proteins that target host defense to facilitate disease development. Although the M. oryzae genome encodes a large number of secreted proteins, only a dozen of them have been cloned and proved to be functional effectors. Discovery of M. oryzae Nuclear Localization Effectors （MoNLEs） was initiated by computational analysis of infection stage-specific expressed secreted proteins. We identified32MoNLE genes that have a putative plant nuclear localization motif. Among them, MGG₀4776（MoNLE1）, MGG₀2253（MoNLE2）, MGG₀9875（MoNLE3） and MGG₀6509（MoNLE4） were identified using the tobacco transient expression system. In addition, all of these four genes were also found to suppress Bax-induced cell death in Nicotiana benthamiana. Fluorescent expression patterns of the MoNLE genes fused with the GFP tag were determined in M. oryzae. Transient expression analysis showed that MoNLEl and MoNLE2were targeted to the nucleus in rice cells. To determine the function of the putative effectors genes in pathogenesis, we generated the MoNLEl mutant and evaluated the vegetative growth and pathogenicity of the mutant. We found that MoNLEl may play an important role in facilitating fungal colonization and fungal growth during infection. Characterization of these fungal effector genes will provide new insights into the molecular basis of the rice and M. oryzae interactions.