Abstract
The powdery mildew (PM) Golovinomyces orontii is an obligate biotrophic fungus that is adapted to Arabidopsis thaliana. Upon infection, PM fungi form haustoria between host cell wall and plasma membrane, and through haustoria, fungi deliver effectors to suppress host immune response, and absorb plant nutrition such as water, sugars and amino acids. However, the molecular mechanisms of PM infection establishment through the haustoria remain to be elucidated. We discovered Arabidopsis Atadf4 null mutant showed resistance against G. orontii. This resistance against PM was even more prominent in RNAi lines, in which the expression of AtADF1~4 was suppressed. Powdery mildew sporulation was significantly suppressed on Atadf4, and on AtADF KD lines, almost no sporulation had occurred. This strong resistance of AtADF KD lines was accompanied with accumulation of hydrogen peroxide and cell death in infected cells. Live cell imaging revealed that Arabidopsis actin microfilaments strongly surrounded PM haustoria. Based on those findings, we hypothesized that PM fungi manipulate host actin microfilaments for rapid delivery of effectors and timely suppression of host immune response.
