• YAKHAK HOEJI
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• v.56 no.6
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• pp.366-371
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• 2012

In this present study, we determined whether or not there is an immunoadjuvant effect of ochnaflavone, a biflavone isolated from Lonicera japonica. As an antigenic source, the cell wall (CACW) of Candida albicans, a fungal pathogen, was used. CACW consists of 95% carbohydrate (mannan). In the experiments, BALB/c mice were immunized with emersion forms of CACW combined with or without ochnaflavone (Och) in the presence of IFA containing mineral oil or CACW alone. Then, the amounts of antisera collected from these mice groups were measured by the ELISA method. Data from these experiments showed that CACW combined with Och (CACW/Och/IFA) provoked the production of antisera app. 2.2 or 5 times more than the corresponding CACW/IFA or CACW alone (CACW/DPBS), respectively, in mice (P<0.05). We further examined the immune response type induced by Och. Analysis of the values of the IgG1/IgG2a ratios obtained from IgG isotyping revealed that Och induced Th2-immunity more dominantly than Th1. This finding was confirmed by cytokine profile. CACW/Och/IFA formulation induced IL-4 (Th2-type cytokine) more than IFN${\gamma}$ (Th1-type cytokine) as compared with CACW/IFA and CACW/DPBS formulations (P<0.05). All data combined, Och appears to have an immunoadjuvant activity that may convert Th1 immunity into Th2 immunity.

• The Plant Pathology Journal
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• v.37 no.3
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• pp.291-298
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• 2021

False smut caused by Ustilaginoidea virens is an important rice fungal disease that significantly decreases its production. In the recent past, conventional methods have been developed for its detection that is time-consuming and need high-cost equipments. The research and development in nanotechnology have made it possible to assemble efficient recognition interfaces in biosensors. In this study, we present a simple, sensitive, and selective oxidized graphene-based geno-biosensor for the detection of rice false smut. The biosensor has been developed using a probe DNA as a biological recognition element on paper electrodes, and oxidized graphene to enhance the limit of detection and sensitivity of the sensor. Probe single-stranded DNA (ssDNA) and target ssDNA hybridization on the interface surface has been quantitatively measured with the electrochemical analysis tools namely, cyclic voltammetry, and linear sweep voltammetry. To confirm the selectivity of the device, probe hybridization with non-complementary ssDNA target has been studied. In our study, the developed sensor was able to detect up to 10 fM of target ssDNA. The paper electrodes were employed to produce an effective and cost-effective platform for the immobilization of the DNA and can be extended to design low-cost biosensors for the detection of the other plant pathogens.

• Research in Plant Disease
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• v.25 no.3
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• pp.103-107
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• 2019

Roles of nutrients in controlling plant diseases have been documented for a long time. Among the nutrients having impact on susceptibility/resistance to crop diseases, nitrogen is one of the most important nutrients for plant growth and development. In rice plants, excess nitrogen via fertilization in agricultural systems is known to increase susceptibility to the rice blast disease. Mechanisms underlying such phenomenon, despite its implication in yield and sustainable agriculture, have not been fully elucidated yet. A few research efforts attempted to link nitrogen-induced susceptibility to concomitant changes in rice plant and rice blast fungus in response to excess nitrogen. However, recent studies focusing on phytobiome are offering new insights into effects of nitrogen on interaction between plants and pathogens. In this review, I will first briefly describe importance of nitrogen as a key nutrient for plants and what changes excess nitrogen can bring about in rice and the fungal pathogen. Next, I will highlight some of the recent phytobiome studies relevant to nitrogen utilization and immunity of plants. Finally, I propose the hypothesis that changes in phytobiome upon excessive nitrogen fertilization contribute to nitrogen-induced susceptibility, and discuss empirical evidences that are needed to support the hypothesis.

• Journal of Microbiology and Biotechnology
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• v.30 no.12
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• pp.1827-1834
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• 2020

Candida albicans is a major fungal pathogen in humans. In our previous study, we reported that an ethanol extract from Aucklandia lappa weakens C. albicans cell wall by inhibiting synthesis or assembly of both (1,3)-β-D-glucan polymers and chitin. In the current study, we found that the extract is involved in permeabilization of C. albicans cell membranes. While uptake of ethidium bromide (EtBr) was 3.0% in control cells, it increased to 7.4% for 30 min in the presence of the A. lappa ethanol extract at its minimal inhibitory concentration (MIC), 0.78 mg/ml, compared to uptake by heat-killed cells. Besides, leakage of DNA and proteins was observed in A. lappa-treated C. albicans cells. The increased uptake of EtBr and leakage of cellular materials suggest that A. lappa ethanol extract induced functional changes in C. albicans cell membranes. Incorporation of diphenylhexatriene (DPH) into membranes in the A. lappa-treated C. albicans cells at its MIC decreased to 84.8%, after 60 min of incubation, compared with that of the controls, indicate that there was a change in membrane dynamics. Moreover, the anticandidal effect of the A. lappa ethanol extract was enhanced at a growth temperature of 40℃ compared to that at 35℃. The above data suggest that the antifungal activity of the A. lappa ethanol extract against C. albicans is associated with synergistic action of membrane permeabilization due to changes in membrane dynamics and cell wall damage caused by reduced formation of (1,3)-β-D-glucan and chitin.

• The Plant Pathology Journal
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• v.39 no.2
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• pp.181-190
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• 2023

The fungal pathogen Pseudocercospora fuligena, known to affect tomatoes in the tropics and subtropics, has been reported from temperate climates including the United States and Turkey in recent years. In this study, an isolate from fresh tomatoes and the disease it causes were characterized and infection mechanisms investigated. Macroscopically, both sides of tomato leaves show indistinct effuse patches but prolific production of fuliginous lesions is conspicuous on the abaxial side first but also on the adaxial side later on as infection progressed. Microscopically, fascicles of conidiophores (11-128 ㎛ × 3.5-9 ㎛) arising from stromata and conidia with up to 12 septations were observed. Molecular characterization of the isolate revealed high homology (99.8%) to other P. fuligena isolated from tomatoes in Turkey. Out of the 10 media tested, P. fuligena grew significantly well and sporulated better on unsealed tomato oatmeal agar and carrot leaf decoction agar, both supplemented with CaCO₃. Direct transfer of conidia from profusely sporulating lesions was the easiest and quickest method of isolation for in-vitro studies. Light and scanning electron microscopy on cleared and intact tomato leaves further confirmed stomatal penetration and egress as well as prevalence of primary and secondary infection hyphae. In situ, blocked stomatal aperture areas of 154, 401, and 2,043 ㎛² were recorded at 7, 12, and 17 days after inoculation, respectively. With the recent expanded horizon of the pathosystem and its consequential impact, such studies will be useful for a proper diagnosis, identification and management of the disease on tomato worldwide.

• The Plant Pathology Journal
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• v.39 no.6
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• pp.614-624
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• 2023

Botrytis cinerea is a major fungal plant pathogen that causes gray mold disease in strawberries, leading to a decrease in strawberry yield. While benzimidazole is widely used as a fungicide for controlling this disease, the increasing prevalence of resistant populations to this fungicide undermines its effectiveness. To investigate benzimidazole resistant B. cinerea in South Korea, 78 strains were isolated from strawberries grown in 78 different farms in 2022, and their EC₅₀ values for benzimidazole were examined. As a result, 64 strains exhibited resistance to benzimidazole, and experimental tests using detached strawberry leaves and the plants in a greenhouse confirmed the reduced efficacy of benzimidazole to control these strains. The benzimidazole resistant strains identified in this study possessed two types of mutations, E198A or E198V, in the TUB2 gene. To detect these mutations, TaqMan probes were designed, enabling rapid identification of benzimidazole resistant B. cinerea in strawberry and tomato farms. This study utilizes TaqMan real-time polymerase chain reaction analysis to swiftly identify benzimidazole resistant B. cinerea, thereby offering the possibility of effective disease management by identifying optimum locations and time of application.

• Journal of Microbiology and Biotechnology
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• v.34 no.2
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• pp.296-305
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• 2024

Peach tree gummosis is a botanical anomaly distinguished by the secretion of dark-brown gum from the shoots of peach trees, and Botryosphaeria dothidea has been identified as one of the fungal species responsible for its occurrence. In South Korea, approximately 80% of gummosis cases are linked to infections caused by B. dothidea. In this study, we isolated microbes from the soil surrounding peach trees exhibiting antifungal activity against B. dothidea. Subsequently, we identified several bacterial strains as potential candidates for a biocontrol agent. Among them, Bacillus velezensis KTA01 displayed the most robust antifungal activity and was therefore selected for further analysis. To investigate the antifungal mechanism of B. velezensis KTA01, we performed tests to assess cell wall degradation and siderophore production. Additionally, we conducted reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis based on whole-genome sequencing to confirm the presence of genes responsible for the biosynthesis of lipopeptide compounds, a well-known characteristic of Bacillus spp., and to compare gene expression levels. Moreover, we extracted lipopeptide compounds using methanol and subjected them to both antifungal activity testing and high-performance liquid chromatography (HPLC) analysis. The experimental findings presented in this study unequivocally demonstrate the promising potential of B. velezensis KTA01 as a biocontrol agent against B. dothidea KACC45481, the pathogen responsible for causing peach tree gummosis.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.468-472
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• 2013

Chrysanthemum is an economically important horticultural plant in many countries. The white rust is one of the most devastating diseases caused by an obligate fungal pathogen Puccinia horiana. This is being controlled mostly by application of chemicals. In Korea, 26 items are registered and 10 items contain 6 triazole compounds. To identify and to obtain the information of the drug target for triazoles, possible sterol 14-demethylase orthologues were extracted. From the draft genome information, the nucleotide sequence of the sterol 14-demethylase gene was identified. The amino acid sequence was deduced and the tertiary structure of the enzyme was predicted. This protein showed no less than 84% amino acid sequence identities to those of genus Puccinia and no more than 68% to those of other genus.

• The Plant Pathology Journal
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• v.35 no.6
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• pp.623-634
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• 2019

Little known the connections between soybeans mitogen-activated protein kinase (MAPK) gene expression and the rhizomicrobiome upon invasion of the root pathogen Fusarium oxysporum. To address this lack of knowledge, we assessed the rhizomicrobiome and root transcriptome sequencing of wild and cultivated soybean during the invasion of F. oxysporum. Results indicated F. oxysporum infection enriched Bradyrhizobium spp. and Glomus spp. and induced the expression of more MAPKs in the wild soybean than cultivated soybean. MAPK gene expression was positively correlated with Pseudomonadaceae but negatively correlated with Sphingomonadaceae and Glomeraceae in both cultivated and wild soybean. Specifically, correlation profiles revealed that Pseudomonadaceae was especially correlated with the induced expression of GmMAKKK13-2 (Glyma.14G195300) and GmMAPK3-2 (Glyma.12G073000) in wild and cultivated soybean during F. oxysporum invasion. Main fungal group Glomeraceae was positively correlated with GmMAPKKK14-1 (Glyma.18G060900) and negatively correlated with GmRaf6-4 (Glyma.02G215300) in the wild soybean response to pathogen infection; while there were positive correlations between Hypocreaceae and GmMAPK3-2 (Glyma.12G073000) and between Glomeraceae and GmRaf49-3 (Glyma.06G055300) in the wild soybean response, these correlations were strongly negative in the response of cultivated soybean to F. oxysporum. Taken together, MAPKs correlated with different rhizomicrobiomes indicating the host plant modulated by the host self-immune systems in response to F. oxysporum.

• Journal of Life Science
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• v.30 no.2
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• pp.122-128
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• 2020

Although Candida albicans is the major fungal pathogen of candidemia, severe infections by non-albicans Candida (NAC) spp. have been increasing in recent years. Among NAC spp., C. glabrata has emerged as the second most common pathogen. However, few studies have been conducted to investigate its structure, epidemiology, and basic biology. In the present study, multi-locus sequence typing (MLST) was performed with a total of 102 C. glabrata clinical isolates that were isolated from various types of clinical specimen. For MLST, six housekeeping genes-FKS, LEU2, NMT1, TRP1, UGP1, and URA3-were amplified and sequenced. The results were analyzed using the C. glabrata database. Out of a total of 3,345 base-pair DNA sequences, 49 variable nucleotide sites were found, and the results showed that 12 different sequence types (ST) were identified from the 102 clinical isolates. The data also demonstrated that the undetermined ST1 was the most predominant ST in Korea. Further, seven undetermined STs (UST) containing UST2-8 were classified at specific loci. The data from this study may provide a fundamental database for further studies on C. glabrata, including its epidemiology and evolution. The data may also contribute to the development of novel antifungal agents and diagnostic tests.