• The Plant Pathology Journal
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• v.17 no.2
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• pp.77-82
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• 2001

Erwinia amylovora causes a devastating disease called fire blight in rosaceous trees and shrubs such as apple, pear, and raspberry. To successfully infect its hosts, the pathogen requires a set of clustered genes termed hrp. Studies on the hrp system of E. amylovora indicated that it consists of three functional classes of genes. Regulation genes including hrpS, hrpS, hrpXY, and hrpL produce proteins that control the expression of other genes in the cluster. Secretion genes, many of which named hrc, encode proteins that may form a transmembrane complex, which is devoted to type III protein secretion. Finally, several genes encode the proteins that are delivered by the protein secretion apparatus. They include harpins, DspE, and other potential effector proteins that may contribute to proliferation of E. amylovora inside the hosts. Harpins are glycine-rich heat-stable elicitors of the hypersensitive response, and induce systemic acquired resistance. The pathogenicity protein DseE is homologous and functionally similar to an avirulence protein of Pseudomonas syringae. The region encompassing the hrpldsp gene cluster of E. amylovora shows features characteristic of a genomic island : a cryptic recombinase/integrase gene and a tRNA gene are present at one end and genes corresponding to those of the Escherichia coli K-12 chromosome are found beyond the region. This island, designated the Hrp pathogenicity island, is more than 60 kilobases in size and carries as many as 60 genes.

• Microbiology and Biotechnology Letters
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• v.40 no.1
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• pp.70-75
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• 2012

In Salmonella enterica, many genes encoded within Salmonella pathogenicity islands (SPI) 1 and 2 are required to cause a range of diseases in a variety of hosts. The SPI1-encoded regulator HilD activates both the SPI1 and 2 genes at different times during growth in Luria-Bertani (LB) media. In this study, the expression levels of hilD during growth in LB were investigated. The data suggest that hilD expression is induced in the early stationary phase and decreases in the late stationary phase, when sseA, an SPI2 gene, is maximally expressed. However, HilD could act as an activator of sseA expression in the late stationary phase despite being present at low levels. SseA expression was investigated in SPI1 regulator mutant strains, hilA, hilD and invF mutants. As expected, hilD mutation decreased sseA expression. However, we found that invF mutation caused a 1.5-fold increase in sseA expression in not only LB but also M9 minimal media, which is thought to resemble an intracellular environment. InvF overexpression restored sseA expression to wild-type levels in an invF mutant but did not cause an additional reduction in sseA expression. These results suggest that SPI1 controls SPI2 expression either positively or negatively.

• Journal of Microbiology
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• v.43 no.spc1
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• pp.85-92
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• 2005

An early step in the pathogenesis of non-typhoidal Salmonella species is the ability to penetrate the intestinal epithelial monolayer. This process of cell invasion requires the production and transport of secreted effector proteins by a type III secretion apparatus encoded in Salmonella pathogenicity island I (SPI-1). The control of invasion involves a number of genetic regulators and environmental stimuli in complex relationships. SPI-1 itself encodes several transcriptional regulators (HilA, HilD, HilC, and InvF) with overlapping sets of target genes. These regulators are, in turn, controlled by both positive and regulators outside SPI-1, including the two-component regulators BarA/SirA and PhoP/Q, and the csr post-transcriptional control system. Additionally, several environmental conditions are known to regulate invasion, including pH, osmolarity, oxygen tension, bile, $Mg^{2+}$ concentration, and short chain fatty acids. This review will discuss the current understanding of invasion control, with emphasis on the interaction of environmental factors with genetic regulators that leads to productive infection.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.10a
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• pp.58.2-58
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• 1999

• Journal of Microbiology and Biotechnology
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• v.23 no.12
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• pp.1664-1672
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• 2013

In Salmonella enterica serovar Typhimurium, many genes encoded within Salmonella pathogenicity island 1 (SPI1) are required to induce intestinal/diarrheal disease. In this study, we compared the expression of four SPI1 genes (hilA, invF, prgH, and sipC) under shaking and standing culture conditions and found that the expression of these genes was highest during the transition from the exponential to stationary phase under shaking conditions. To identify regulators associated with the stationary phase-dependent activation of SPI1, the effects of selected regulatory genes, including relA/spoT (ppGpp), luxS, ihfB, hfq, and arcA, on the expression of hilA and invF were compared under shaking conditions. Mutations in the hfq and arcA genes caused a reduction in hilA and invF expression (more than 2-fold) in the early stationary phase only, whereas the lack of ppGpp and IHF decreased hilA and invF gene expression during the entire stationary phase. We also found that hfq and arcA mutations caused a reduction of hilD expression upon entry into the stationary phase under shaking culture conditions. Taken together, these results suggest that Hfq and ArcA regulate the hilD promoter, causing an accumulation of HilD, which can trigger a stationary phase-dependent activation of SPI1 genes under shaking culture conditions.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.725-728
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• 1998

Phytophthora crown rot of cymbidium was observed in Cheju island since June of 1996. The disease initiated at the basal portion of infected plant progressed upward to lower leaves. Soon after distinct water-soaking lesions appeared on lower leaves, the plant was wilted, blighted and died. Four orchid farms at Sogwipo out of 16 surveyed in the island were infected by the disease estimating 5~20% infection rates. The causal fungus was identified as P. palmivora based on following distinguishing characteristics. All isolates were heterothallic as A1 types and readily produced chlamydospores with cultural age. Sporangia were conspicuous papillate, ellipsoidal to ovoid, highly deciduous with short pedicels ca. 3~4 ${\mu}{\textrm}{m}$. Koch's rules were satisfied by a pathogenicity test and re-isolation of the fungus from inoculated plants. The pathogen has never been reported in Cheju island previously and its firstly recorded as the cause of Phytophthora crown rot of cymbidium in Korea.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.51-55
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• 2002

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.158-160
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• 2018

Streptomyces sp. P3 was isolated from potato scab diseased tubers in Pyeongchang, Gangwon-do, Republic of Korea in 2017. Here, we report the draft genome sequences of P3 with 9,851,971 bp size (71.2% GC content) of the chromosome. The genome comprises 8,548 CDS, 18 rRNA and 66 tRNA genes. Although strain P3 did not show pathogenicity both potato tuber assay and radish seedling assay, it possesses tomatinase (tomA) gene among conserved pathogenicity-related genes in well characterized pathogenic Streptomyces. Thus, the genome sequences determined in this study will be useful to understand for pathogenic evolution in Streptomyces species, which already adapted to potato scab pathogens.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.47.1-47
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• 2002

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2000.10a
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• pp.54.2-54
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• 2000