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Il-Pyung Ahn,Kyungseok Park,Choong-Hoe Kim 한국분자세포생물학회 2002 Molecules and cells Vol.13 No.2
Selected strain of nonpathogenic rhizobacterium EXTN-1 from the Bacillus amyloliquefaciens is capable of eliciting broad-spectrum induced systemic resistance (ISR) in several crops that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). In tobacco (Nicotiana tabacum cv. Samsun- nn), EXTN-1 treatment also perturbs the disease progress by Pepper mild mottle virus (PMMoV), a member of Tobamovirus group. To investigate the defense mechanisms induced by this rhizobacterium, expression patterns of defense-related genes were analyzed. The EXTN-1-treated tobacco plants showed augmented, rapid transcript accumulation of defenserelated genes including PR-1a, phenylalanine ammonia- lyase (PAL), and 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) following inoculation with PMMoV. This was the typical phenomenon of potentiation. Accelerated expression of all these genes was subsequently detected in the noninoculated, upper leaves; thus, their expression is associated with the development of both local and systemic resistance. Coordinated reduction of viral genome accumulation was clearly detected in the leaves of tobacco pretreated with EXTN-1. EXTN-1 treatment on Arabidopsis wild type Col-0 resulted in the activation of PR-1 and PDF1.2 at the same time. All these results may indicated that EXTN-1 induces systemic resistance via salicylic acid- and jasmonic acid-dependent pathways and timely recognition followed by rapid counterattack against the viral invasion is the key differences between incompatible interaction and compatible one.
Ahn, Il-Pyung,Lee, Yong-Hwan The Korean Society of Plant Pathology 2000 Plant Pathology Journal Vol.16 No.4
A total of 90 isolates of Fusarium oxysporum f.sp. melonis, the causal agent of oriental melon (Cucumis melo var. makuwa) wilt, was isolated from symptomatic tissues of oriental melon from 4 provinces in Korea. These isolates were grouped into vegetative compatibility groups (VCGs) by demonstrating heterokaryosis through complementation using nitrate nonutilizing (nit) mutants. No self-incompatibility was observed in any of isolates. All isolates were grouped into 3 VCGs ; A, B, and C. iSOLATES BELONGING TO VCG A and VCG B accounted for 87% and 91% of the fungal population collected in 1991 and 1993, respectively. As the increment of cultivation period in the same field, the proportion of isolates belonging to VCG B increased whereas that of isolates belonging to VCG A decreased. Mean virulence of a total population increased as the increment of cultivation period in the same field. Isolates belonging to VCG B showed the highest increment of virulence. These data suggest that replanting of a host plant in the same field may cause increase of virulence in the pathogens. Furthermore, virulence of F. oxysporum f.sp. melonis isolates is related to the VCGs.
High Throughput Screening of Antifungal Metabolites Against Colletotrichum gloeosporioides
Ahn, Il-Pyung,Kim, Soon-Ok,Lee, Yong-Hwan The Korean Society of Plant Pathology 2008 Plant Pathology Journal Vol.24 No.1
Colletotrichum gloeosporioides forms an appressorium, a specialized infection structure, to infect its hosts. Among 400 and 600 culture filtrates from fungi and class Actinomycetes, six methanol extracts (A5005, A5314, A5387, A5560, A5597, and A5598) from the class Actinomycetes significantly inhibited appressorium formation in C. gloeosporioides infecting pepper fruits in a dose-dependent manner, while conidial germination was slightly enhanced. Two (A5005 and A5560) of them also exhibited distinctive inhibitory effect on the disease progress of pepper anthracnose. Water fractions of both culture filtrates also specifically inhibited appressorium formation in C. gloeosporioides and pepper anthracnose disease. Inhibition of appressorium formation by culture filtrate of A5005 was partially restored by the exogenous calcium. This results suggests that chemicals within A5005 extents its biological activity through disturbance of intracellular $Ca^{2+}$ regulation during prepenetration morphogenesis by C. gloeosporioides. Together, cell-based and target-oriented screening system used in this study should be applicable for other plant pathogenic fungi prerequisite appressorium formation to infect their hosts.
Rhizobacteria-induced priming in Arabidopsis is dependent on ethylene, jasmonic acid, and NPR1.
Ahn, Il-Pyung,Lee, Sang-Woo,Suh, Seok-Cheol APS Press 2007 Molecular plant-microbe interactions Vol.20 No.7
<P>A nonpathogenic rhizobacterium, Pseudomonas putida LSW17S, elicited systemic protection against Fusarium wilt and pith necrosis caused by Fusarium oxysporum f. sp. lycopersici and P. corrugata in tomato (Lycopersicon esculentum L.). LSW17S also confers disease resistance against P. syringae pv. tomato DC3000 (DC3000) on Arabidopsis ecotype Col-0. To investigate mechanisms underlying disease protection, expression patterns of defense-related genes PR1, PR2, PR5, and PDF1.2 and cellular defense responses such as hydrogen peroxide accumulation and callose deposition were investigated. LSW17S treatment exhibited the typical phenomena of priming. Strong and faster transcription of defense-related genes was induced and hydrogen peroxide or callose were accumulated in Arabidopsis treated with LSW17S and infected with DC3000. In contrast, individual actions of LSW17S and DC3000 did not elicit rapid molecular and cellular defense responses. Priming by LSW17S was translocated systemically and retained for more than 10 days. Treatment with LSW17S reduced pathogen proliferation in Arabidopsis ecotype Col-0 expressing bacterial NahG; however, npr1, etr1, and jar1 mutations impaired inhibition of pathogen growth. Cellular and molecular priming responses support these results. In sum, LSW17S primes Arabidopsis for NPR1-, ethylene-, and jasmonic acid-dependent disease resistance, and efficient molecular and cellular defense responses.</P>
Il-Pyung Ahn,Sang-Woo Lee,김민갑,Sang-Ryeol Park,황덕주,배신철 한국분자세포생물학회 2011 Molecules and cells Vol.32 No.1
A selected strain of rhizobacterium, Pseudomonas putida strain LSW17S (LSW17S), protects tomato plants (Lyco-persicon esculentum L. cv. Seokwang) from bacterial speck by biotrophic Pseudomonas syringae pv. tomato strain DC3000 (DC3000) and bacterial wilt by necrotrophic Ralstonia solanacearum KACC 10703 (Rs10703). To investigate defense mechanisms induced by LSW17S in tomato plants, transcription patterns of pathogenesis-related (PR) genes and H2O2 production were analyzed in plants treated with LSW17S and subsequent pathogen inoculation. LSW17S alone did not induce transcriptions of employed PR genes in leaves and roots. DC3000 challenge following LSW17S triggered rapid transcriptions of PR genes and H_2O_2 production in leaves and roots. Catalase infiltration with DC3000 attenuated defense-related responses and resistance against DC3000 infection. Despite depriving H_2O_2 production and PR1b transcription by the same treatment, resistance against Rs10703 infection was not deterred significantly. H_2O_2 is indispensable for defense signaling and/or mechanisms primed by LSW17S and inhibition of bacterial speck, however, it is not involved in resistance against bacterial wilt.