title: Magnaporthe oryzae Glycine-Rich Secretion Protein, Rbf1 Critically Participates in Pathogenicity through the Focal Formation of the Biotrophic Interfacial Complex.
abstract: Magnaporthe oryzae, the fungus causing rice blast disease, should contend with host innate immunity to develop invasive hyphae (IH) within living host cells. However, molecular strategies to establish the biotrophic interactions are largely unknown. Here, we report the biological function of a M. oryzae-specific gene, Required-for-Focal-BIC-Formation 1 (RBF1). RBF1 expression was induced in appressoria and IH only when the fungus was inoculated to living plant tissues. Long-term successive imaging of live cell fluorescence revealed that the expression of RBF1 was upregulated each time the fungus crossed a host cell wall. Like other symplastic effector proteins of the rice blast fungus, Rbf1 accumulated in the biotrophic interfacial complex (BIC) and was translocated into the rice cytoplasm. RBF1-knockout mutants (Δrbf1) were severely deficient in their virulence to rice leaves, but were capable of proliferating in abscisic acid-treated or salicylic acid-deficient rice plants. In rice leaves, Δrbf1 inoculation caused necrosis and induced defense-related gene expression, which led to a higher level of diterpenoid phytoalexin accumulation than the wild-type fungus did. Δrbf1 showed unusual differentiation of IH and dispersal of the normally BIC-focused effectors around the short primary hypha and the first bulbous cell. In the Δrbf1-invaded cells, symplastic effectors were still translocated into rice cells but with a lower efficiency. These data indicate that RBF1 is a virulence gene essential for the focal BIC formation, which is critical for the rice blast fungus to suppress host immune responses.
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Mochizuki
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Ishii-Minami
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Yukiko
authors.identifier: http://orcid.org/0000-0002-4054-0947
authors.initials: Y
authors.lastname: Fujisawa
authors.affiliation: Division of Basic Research, Institute of Crop Science, NARO, Tsukuba, Ibaraki, Japan.|Bioinformatics Team, Advanced Analysis Center, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawahara
authors.affiliation: Biotechnology Research Center, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Yoshida
authors.affiliation: Biotechnology Research Center, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Okada
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Sugihiro
authors.initials: S
authors.lastname: Ando
authors.affiliation: Iwate Biotechnology Research Center, Kitakami, Iwate, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsumura
authors.affiliation: Iwate Biotechnology Research Center, Kitakami, Iwate, Japan.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Terauchi
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Minami
authors.affiliation: Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nishizawa
mesh_terms: D005656:Fungal Proteins / Q000378:metabolism*; D020082:Magnaporthe / Q000472:pathogenicity*; D009181:Mycoses / Q000382:microbiology*; D012275:Oryza; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D014774:Virulence
chemical_list: D005656:Fungal Proteins