title: Induction of defense responses in cucumber plants by using the cell-free filtrate of the plant growth-promoting fungus Penicillium simplicissimum GP17-2.
abstract: Penicillium simplicissimum GP17-2 is a plant growth-promoting fungus (PGPF) and an inducer of systemic defense responses. The mechanisms underlying the effect of GP17-2 on the reduction of cucumber leaf damage caused by the anthracnose pathogen Colletotrichum orbiculare were investigated. Cucumber leaves treated with the culture filtrate (CF) of GP17-2 exhibited a clear systemic resistance against subsequent infection with C. orbiculare. The number and size of lesions caused by the disease were reduced in CF-treated plants, in comparison with that in the control plants. The results showed that CF treatment could trigger a set of defense responses, including the production of hydrogen peroxide, formation of lignin, emission of ultra-weak photons, accumulation of salicylic acid, and increase in the transcription of the genes for the defense-related enzymes chitinase and peroxidase. Furthermore, subsequent inoculation of CF-pretreated plants with C. orbiculare resulted in higher systemic expression of the genes for chitinase, β-1,3-glucanase, and peroxidase relative to nontreated, inoculated plants; this indicated that CF mediates a potentiation state in the plant, enabling it to mount a rapid and effective response on infection by C. orbiculare. Our results indicate that the ability of CF of GP17-2 to stimulate active oxygen species, lignification, SA accumulation, and defense gene activation and potentiation in the host is the possible mode of action of the GP17-2 elicitor and inducer of induced systemic resistance against C. orbiculare infection in cucumber plants.
authors.affiliation: Laboratory of Plant Pathology, Faculty of Agriculture, Gifu University, Yanagido, Gifu, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Shimizu
authors.forename: Mohamed Motaher
authors.initials: MM
authors.lastname: Hossain
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kato
authors.forename: Mashaharu
authors.initials: M
authors.lastname: Kubota
authors.forename: Mitsuro
authors.initials: M
authors.lastname: Hyakumachi
mesh_terms: D002474:Cell-Free System / Q000502:physiology; D002688:Chitinases / Q000235:genetics; D020231:Colletotrichum / Q000472:pathogenicity; D018553:Cucumis sativus / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D005656:Fungal Proteins / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D010407:Penicillium / Q000502:physiology*; D009195:Peroxidase / Q000235:genetics; D017785:Photons; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology* / Q000382:microbiology; D018515:Plant Leaves; D020156:Salicylic Acid / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D003470:Culture Media; D005656:Fungal Proteins; D008031:Lignin; D006861:Hydrogen Peroxide; D009195:Peroxidase; D002688:Chitinases; D020156:Salicylic Acid