title: Multifaceted Roles of the Ras Guanine-Nucleotide Exchange Factor ChRgf in Development, Pathogenesis, and Stress Responses of Colletotrichum higginsianum.
abstract: The infection process of Colletotrichum higginsianum, which causes a disease of crucifers, involves several key steps: conidial germination, appressorial formation, appressorial penetration, and invasive growth in host tissues. In this study, the ChRgf gene encoding a Ras guanine-nucleotide exchange factor protein was identified by screening T-DNA insertion mutants generated from Agrobacterium tumefaciens-mediated transformation that were unable to cause disease on the host Arabidopsis thaliana. Targeted gene deletion of ChRgf resulted in a null mutant (ΔChrgf-42) with defects in vegetative growth, hyphal morphology, and conidiation, and poor surface attachment and low germination on hydrophobic surfaces; however, there were no apparent differences in appressorial turgor pressure between the wild type and the mutant. The conidia of the mutant were unable to geminate on attached Arabidopsis leaves and did not cause any disease symptoms. Intracellular cyclic adenosine monophosphate levels in the ΔChrgf mutant were lower than that of the wild type. Our results suggest that ChRgf is a key regulator in response to salt and osmotic stresses in C. higginsianum, and indicate that it is involved in fungal pathogenicity. This gene seems to act as an important modulator upstream of several distinct signaling pathways that are involved in regulating vegetative growth, conidiation, infection-related structure development, and stress responses of C. higginsianum.
authors.affiliation: First, second, and sixth authors: The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; first and fourth authors: Department of Biology, University of Saskatchewan, Saskatoon S7N 5E2, Canada; and fifth author: School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Canada.
authors.forename: Qiongnan
authors.initials: Q
authors.lastname: Gu
authors.affiliation: First, second, and sixth authors: The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; first and fourth authors: Department of Biology, University of Saskatchewan, Saskatoon S7N 5E2, Canada; and fifth author: School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Canada.
authors.forename: Meijuan
authors.initials: M
authors.lastname: Chen
authors.affiliation: First, second, and sixth authors: The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; first and fourth authors: Department of Biology, University of Saskatchewan, Saskatoon S7N 5E2, Canada; and fifth author: School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Canada.
authors.forename: Junbin
authors.initials: J
authors.lastname: Huang
authors.affiliation: First, second, and sixth authors: The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; first and fourth authors: Department of Biology, University of Saskatchewan, Saskatoon S7N 5E2, Canada; and fifth author: School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Canada.
authors.forename: Yangdou
authors.initials: Y
authors.lastname: Wei
authors.affiliation: First, second, and sixth authors: The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; first and fourth authors: Department of Biology, University of Saskatchewan, Saskatoon S7N 5E2, Canada; and fifth author: School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Canada.
authors.forename: Tom
authors.initials: T
authors.lastname: Hsiang
authors.affiliation: First, second, and sixth authors: The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; first and fourth authors: Department of Biology, University of Saskatchewan, Saskatoon S7N 5E2, Canada; and fifth author: School of Environmental Sciences, University of Guelph, Guelph N1G 2W1, Canada.
authors.forename: Lu
authors.initials: L
authors.lastname: Zheng
mesh_terms: D017360:Arabidopsis / Q000382:microbiology*; D020231:Colletotrichum / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D025301:Hyphae; D008954:Models, Biological; D016254:Mutagenesis, Insertional; D010641:Phenotype; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D013172:Spores, Fungal; D013312:Stress, Physiological; D014774:Virulence; D020663:ras Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D020663:ras Guanine Nucleotide Exchange Factors
keywords: morphogenesis