title: The citrus postharvest pathogen Penicillium digitatum depends on the PdMpkB kinase for developmental and virulence functions.
abstract: The postharvest pathogen Penicillium digitatum causes green mold decay on citrus fruit, resulting in severe economic losses. To explore possible factors involved in fungal pathogenesis, phenotypic characterization of the budding yeast Fus3/Kiss1 mitogen-activated protein (MAP) kinase homolog was carried out. The P. digitatum MAP kinase B coding gene, designated PdMpkB, was functionally inactivated via homologous recombination. The fungal strain (∆PdMpkB) carrying a PdMpkBdeletion demonstrated altered gene expression profiles, reduced growth and conidiogenesis, elevated resistance to osmotic stress, and failed to induce green mold decay on citrus fruit. ∆PdMpkB was more resistant to CaCl2, NaCl and sorbitol than its progenitor strain, indicating a negative regulatory function of PdMpkB in osmotic stress adaptation. Fungal infection assays on citrus fruit revealed that ∆PdMpkB proliferated poorly within host tissues, induced water-soaking lesions, failed to break through host cuticle layers and thus, failed to produce aerial hyphae and conidia. Introduction of a functional copy of PdMpkB into a null mutant restored all defective phenotypes. Transcriptome analysis revealed that inactivation of PdMpkB impacted expression of the genes associated with cell wall-degrading enzyme activities, carbohydrate and amino acid metabolisms, conidial formation, and numerous metabolic processes. Our results define pivotal roles of the PdMpkB-mediated signaling pathway in developmental and pathological functions in the citrus postharvest pathogen P. digitatum.
authors.affiliation: Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
authors.forename: Haijie
authors.initials: H
authors.lastname: Ma
authors.affiliation: Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xuepeng
authors.initials: X
authors.lastname: Sun
authors.affiliation: Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
authors.forename: Mingshuang
authors.initials: M
authors.lastname: Wang
authors.affiliation: Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Gai
authors.affiliation: Department of Plant Pathology, National Chung-Hsing University, Taichung 40227, Taiwan. Electronic address: krchung@nchu.edu.tw.
authors.forename: Kuang-Ren
authors.initials: KR
authors.lastname: Chung
authors.affiliation: Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China. Electronic address: hyli@zju.edu.cn.
authors.forename: Hongye
authors.initials: H
authors.lastname: Li
mesh_terms: D002957:Citrus / Q000382:microbiology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009997:Osmotic Pressure; D010407:Penicillium / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology*; D013172:Spores, Fungal / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D059467:Transcriptome; D014774:Virulence
chemical_list: D005656:Fungal Proteins; D020928:Mitogen-Activated Protein Kinases
keywords: Fruit decay; Green mold; Orange; Osmotic; Pathogenicity