Magnaporthe oryzae Glycine-Rich Secretion Protein, Rbf1 Critically Participates in Pathogenicity through the Focal Formation of the Biotrophic Interfacial Complex

PLoS Pathogens

Yuri Yoshida¹  Kazunori Okada²  Sugihiro Ando²  Yoshihiro Kawahara³  Susumu Mochizuki⁴  Takeshi Nishimura⁴  Hideo Matsumura⁴  Yukiko Fujisawa⁴  Naoko Ishii-Minami⁴  Yoko Nishizawa⁴  Ryohei Terauchi⁵  Eiichi Minami⁵ 

[1] Bioinformatics Team, Advanced Analysis Center, NARO, Tsukuba, Ibaraki, Japan;Biotechnology Research Center, The University of Tokyo, Bunkyo-ku, Tokyo, Japan;Division of Basic Research, Institute of Crop Science, NARO, Tsukuba, Ibaraki, Japan;Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, NARO, Tsukuba, Ibaraki, Japan;Iwate Biotechnology Research Center, Kitakami, Iwate, Japan

关键词: Leaves;    Rice;    Rice blast fungus;    Appressoria;    Fungi;    Fungal structure;    Fungal genetics;    Host cells;   

DOI  :  10.1371/journal.ppat.1005921

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

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.

【 授权许可】

CC BY