Abstract
The powdery mildew Golovinomyces orontii is an obligate biotrophic fungus that infects Arabidopsis thaliana. For successful infection, powdery mildew has to overcome mutilayer defense system of plants. The conidial germination and appresorial formation are largely affected by the host cuticular components. After invasion, plant hormone salicylic acid (SA) limits powdery mildew growth and proliferation, although exact role of SA in the plant defense response remains to be elucidated. Our detailed morphological analyses revealed that powdery mildew germination and appresorial formation were suppressed on stems compared to leaves, and that this suppression was significantly reduced on wax2/yre/flp1 stems, in which the wax accumulation was reduced and cuticular components were altered. Interestingly, the mutation in WAX2/YRE/FLP1 showed an opposite effect at later infection stages; on wax2/yre/flp1 leaves, mycelial growth and conidiophore formation were retarded. We are currently carrying out further morphological analyses as well as RT-PCR analysis to discuss the multiple roles of WAX2/YRE/FLP1 in the Arabidopsis defense response against powdery mildew.
