title: Induction of defense response against Rhizoctonia solani in cucumber plants by endophytic bacterium Bacillus thuringiensis GS1.
abstract: An endophytic bacterium, Bacillus thuringiensis GS1, was isolated from bracken (Pteridium aquilinum) and found to have maximal production of chitinase (4.3 units/ml) at 5 days after culture. This study investigated the ability of B. thuringiensis GS1 to induce resistance to Rhizoctonia solani KACC 40111 (RS) in cucumber plants. Chitinase activity was greatest in RS-treated plants at 4 days. beta-1,3- Glucanase activity was highest in GS1-treated plants at 5 days. Guaiacol peroxidase (GPOD) activity increased continuously in all treated plants for 5 days. Ascorbate peroxidase (APX) activity in RS-treated plants was increased 1.5-fold compared with the control at 4 days. Polyphenol oxidase (PPO) activity in RS-treated plants was increased 1.5-fold compared with the control at 3 days. At 5 days after treatment, activity staining revealed three bands with chitinase activity (Ch1, Ch2, and Ch3) on SDSPAGE of cucumber plants treated with GS1+RS, whereas only one band was observed for RS-treated plants (Ch2). One GPOD isozyme (Gp1) was also observed in response to treatment with RS and GS1+RS at 4 days. One APX band (Ap2) was present on the native-PAGE gel of the control, and GS1- and GS1+RS-treated plants at 1 day. PPO bands (Po1 and Po2) from RS- and GS1+RS-treated plants were stronger than in the control and GS1-treated plants upon native-PAGE at 5 days. Taken together, these results indicate that the induction of PR proteins and defense-related enzymes by B. thuringiensis GS1 might have suppressed the damping-off caused by R. solani KACC 40111 in cucumber plants.
authors.affiliation: Division of Applied Bioscience and Biotechnology, Institute of Environmentally-Friendly Agriculture (IEFA), Chonnam National University, Gwangju 500-757, Korea.
authors.forename: Dong-Jun
authors.initials: DJ
authors.lastname: Seo
authors.forename: Dang-Minh-Chanh
authors.initials: DM
authors.lastname: Nguyen
authors.forename: Yong-Su
authors.initials: YS
authors.lastname: Song
authors.forename: Woo-Jin
authors.initials: WJ
authors.lastname: Jung
mesh_terms: D000898:Antibiosis; D060387:Ascorbate Peroxidases / Q000276:immunology; D001413:Bacillus thuringiensis / Q000201:enzymology / Q000302:isolation & purification / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism; D002688:Chitinases / Q000378:metabolism; D018553:Cucumis sativus / Q000201:enzymology / Q000276:immunology* / Q000382:microbiology*; D060026:Endophytes / Q000201:enzymology / Q000302:isolation & purification / Q000502:physiology*; D009195:Peroxidase / Q000276:immunology; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology* / Q000517:prevention & control; D010940:Plant Proteins / Q000276:immunology; D032498:Pteridium / Q000382:microbiology* / Q000502:physiology; D012232:Rhizoctonia / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D010940:Plant Proteins; C121048:guaiacol peroxidase; D060387:Ascorbate Peroxidases; D009195:Peroxidase; D002688:Chitinases