title: Colletotrichum orbiculare WHI2, a Yeast Stress-Response Regulator Homolog, Controls the Biotrophic Stage of Hemibiotrophic Infection Through TOR Signaling.
abstract: The hemibiotrophic fungus Colletotrichum orbiculare first establishes a biotrophic infection stage in cucumber (Cucumber sativus) epidermal cells and subsequently transitions to a necrotrophic stage. Here, we found that C. orbiculare established hemibiotrophic infection via C. orbiculare WHI2, a yeast stress regulator homolog, and TOR (target of rapamycin) signaling. Plant defense responses such as callose deposition, H2O2, and antimicrobial proteins were strongly induced by the C. orbiculare whi2Δ mutant, resulting in defective pathogenesis. Expression analysis of biotrophy-specific genes evaluated by the promoter VENUS fusion gene indicated weaker VENUS signal intensity in the whi2Δ mutant, thereby suggesting that C. orbiculare WHI2 plays a key role in regulating biotrophic infection of C. orbiculare. The involvement of CoWHI2 in biotrophic infection was further explored with a DNA microarray. In the Cowhi2Δ mutant, TOR-dependent ribosomal protein-related genes were strikingly upregulated compared with the wild type. Moreover, callose deposition in the host plant after inoculation with the Cowhi2Δ mutant treated with rapamycin, which inhibits TOR activity, was reduced, and the mutant remained biotrophic in contrast to the untreated mutant. Thus, regulation of TOR by Whi2 is apparently crucial to the biotrophic stage of hemibiotrophic infection in C. orbiculare.
authors.affiliation: 1 Laboratory of Plant Pathology, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan; and.
authors.forename: Ken
authors.initials: K
authors.lastname: Harata
authors.affiliation: 2 Division of Functional Genomics, Advanced Science Research Centre, Kanazawa University, Kanazawa, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Nishiuchi
authors.affiliation: 1 Laboratory of Plant Pathology, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan; and.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kubo
mesh_terms: D002473:Cell Wall / Q000378:metabolism; D020231:Colletotrichum / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D018553:Cucumis sativus / Q000382:microbiology* / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D058685:Genetic Pleiotropy; D005936:Glucans / Q000378:metabolism; D054884:Host-Pathogen Interactions; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D005936:Glucans; D029701:Saccharomyces cerevisiae Proteins; C470937:Whi2 protein, S cerevisiae; C048306:callose; D006861:Hydrogen Peroxide; D058570:TOR Serine-Threonine Kinases