title: Nuclear Function of Subclass I Actin-Depolymerizing Factor Contributes to Susceptibility in Arabidopsis to an Adapted Powdery Mildew Fungus.
abstract: Actin-depolymerizing factors (ADFs) are conserved proteins that function in regulating the structure and dynamics of actin microfilaments in eukaryotes. In this study, we present evidence that Arabidopsis (Arabidopsis thaliana) subclass I ADFs, particularly ADF4, functions as a susceptibility factor for an adapted powdery mildew fungus. The null mutant of ADF4 significantly increased resistance against the adapted powdery mildew fungus Golovinomyces orontii. The degree of resistance was further enhanced in transgenic plants in which the expression of all subclass I ADFs (i.e. ADF1-ADF4) was suppressed. Microscopic observations revealed that the enhanced resistance of adf4 and ADF1-4 knockdown plants (ADF1-4Ri) was associated with the accumulation of hydrogen peroxide and cell death specific to G. orontii-infected cells. The increased resistance and accumulation of hydrogen peroxide in ADF1-4Ri were suppressed by the introduction of mutations in the salicylic acid- and jasmonic acid-signaling pathways but not by a mutation in the ethylene-signaling pathway. Quantification by microscopic images detected an increase in the level of actin microfilament bundling in ADF1-4Ri but not in adf4 at early G. orontii infection time points. Interestingly, complementation analysis revealed that nuclear localization of ADF4 was crucial for susceptibility to G. orontii. Based on its G. orontii-infected-cell-specific phenotype, we suggest that subclass I ADFs are susceptibility factors that function in a direct interaction between the host plant and the powdery mildew fungus.
authors.affiliation: Laboratory of Plant Function Analysis, Plant Global Educational Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan (N.I.); andDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8562, Japan (T.H., S.H.) noriko@bs.s.u-tokyo.ac.jp.
authors.forename: Noriko
authors.initials: N
authors.lastname: Inada
authors.affiliation: Laboratory of Plant Function Analysis, Plant Global Educational Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan (N.I.); andDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8562, Japan (T.H., S.H.).
authors.forename: Takumi
authors.initials: T
authors.lastname: Higaki
authors.affiliation: Laboratory of Plant Function Analysis, Plant Global Educational Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan (N.I.); andDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8562, Japan (T.H., S.H.).
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Hasezawa
mesh_terms: D051339:Actin Depolymerizing Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota / Q000472:pathogenicity*; D002467:Cell Nucleus / Q000378:metabolism; D055785:Gene Knockdown Techniques; D017343:Genes, Plant; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000502:physiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000378:metabolism; D030821:Plants, Genetically Modified; D015398:Signal Transduction
chemical_list: C542432:ADF4 protein, Arabidopsis; D051339:Actin Depolymerizing Factors; D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; D006861:Hydrogen Peroxide