• Mycobiology
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• 제50권6호
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• pp.457-466
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• 2022

Epicoccum nigrum is a saprophytic or endophytic fungus that is found worldwide. Because of the antagonist effects of E. nigrum on many plant pathogens, current studies on E. nigrum have focused on the development of biological control agents and the utilization of its various metabolites. In this study, E. nigrum was collected from a wheat field, and its genetic diversity was analyzed. Phylogenetic analyses identified 63 isolates of E. nigrum divided into seven groups, indicating a wide genetic diversity. Isolates antagonized the wheat pathogen Fusarium graminearum, and reduced disease symptoms caused by F. graminearum in wheat coleoptiles. Moreover, pretreatment of wheat coleoptiles with E. nigrum induced the upregulation of pathogen-related (PR) genes, PR1, PR2, PR3, PR5, PR9, and PR10 in wheat coleoptiles responding to F. graminearum invasion. Overall, this study indicates that E. nigrum isolates can be used as biological pathogen inhibitors applied in wheat fields.

• Journal of Applied Biological Chemistry
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• 제65권3호
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• pp.159-166
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• 2022

Epicoccum nigrum produces epipyrone A (orevactaene), a yellow polyketide pigment. Its biosynthetic gene cluster was previously characterized in E. nigrum KACC 40642. The YES liquid culture of this strain revealed high-level production of epicoccamide (EPC), with an identity that was determined using liquid chromatography-mass spectrometry analysis and molecular mass search using the SuperNatural database V2 webserver. The production of EPC was further confirmed by compound isolation and nuclear magnetic resonance spectroscopy. EPC is a highly reduced polyketide with tetramic acid and mannosyl moieties. The EPC structure guided us to localize the hypothetical EPC biosynthetic gene cluster (BGC) in E. nigrum ICMP 19927 genome sequence. The BGC contains genes encoding highly reducing (HR)-fungal polyketide synthase (fPKS)-nonribosomal peptide synthetase (NRPS), glycosyltransferase (GT), enoylreductase, cytochrome P450, and N-methyltrasnferase. Targeted inactivation of the HR-fPKS-NRPS and GT genes abolished EPC production, supporting the successful localization of EPC BGC. This study provides a platform to explore the hidden biological activities of EPC, a bolaamphiphilic compound.

• Journal of Applied Biological Chemistry
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• 제64권3호
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• pp.225-236
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• 2021

The epipyrone (EPN) biosynthetic gene cluster of Epicoccum nigrum is composed of epnC, epnB, and epnA, which encode cytochrome P450 oxidase, glycosyltransferase, and highly reducing polyketide synthase, respectively. Gene inactivation mutants for epnA, epnB, and epnC were previously generated, and it was found that all of them were incapable of producing EPN and any of its related compounds. It was also reported that epnB inactivation abolished epnA transcription, generating ΔepnAB. This study shows that the introduction of native epnC readily restored EPN production in ΔepnC, suggesting that epnC is essential for polyketide release from EpnA and implies that EpnC works during the polyketide chain assembly of EpnA. Introduction of epnC promoter-epnA restored EPN production in ΔepnA. The ΔepnB genotype was prepared by introducing the epnA expression vector into ΔepnAB, and it was found that the resulting recombinant strain did not produce any EPN-related compounds. A canonical epnB inactivation strain was also generated by deleting its 5'-end. At the deletion point, an Aspergllus nidulans gpdA promoter was inserted to ensure the transcription of epnA, which is located downstream of epnB. Examination of the metabolite profile of the resulting ΔepnB mutant via LC-mass spectrometry verified that no EPN-related compound was produced in this strain. This substantiates that C-glycosylation by EpnB is a prerequisite for the release of EpnA-tethered product. In conclusion, it is proposed that cytochrome P450 oxidase and glycosyltransferase work in concert with polyketide synthase to generate EPN without the occurrence of any free intermediates.

• 한국균학회지
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• 제40권3호
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• pp.136-140
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• 2012

생강나무에 공생하는 내생균의 다양성을 확인하기 위하여, 강원도 4 개 지역에서 병증이 없는 생강나무 잎을 채집하여 내생균을 분리하였다. 분리된 내생균의 rDNA의 ITS지역을 분석한 결과, Alternaria alternata, Annulohypoxylon annulatum, Creosphaeria sassafras, Diaporthe eres, Discosia sp., Epicoccum nigrum, Glomerella acutata, Glomerella cingulata, Paraconiothyrium brasiliense, Pestalotiopsis neglecta, Phomopsis amygdali, Xylaria sp.의 총 7과 11속 12종이 확인되었으며 Phomopsis amygdali가 모든 연구 지역의 생강나무 잎에서 가장 높은 빈도로 분리되었으며 채집지에 따라 내생균의 종 다양성에 차이가 있음을 확인하였다.

• 한국미생물·생명공학회지
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• 제36권4호
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• pp.276-284
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• 2008

숙성된 김치로부터 항진균 활성을 나타내는 균주 1종과 감수성을 나타내는 곰팡이 1종을 분리하였다. 분리된 균주는 형태학적, 생화학적 특성 조사와 165 rRNA 염기서열 결정을 통한 균주 동정 결과 Lactobacillus plantarum AF1으로 명명하였고, 감수성 곰팡이는 ITS-5.8S rRNA 염기서열 분석을 통하여 Epicoccum nigrum KF-1으로 명명하였다. Dual culture overlay assay를 통한 Lb. plantarum AF1의 항진균 활성 실험 결과 A. ochraceus, A fumigatus, C. gossypiicola 등 식품 부패 곰팡이 및 병원성 곰팡이에 강한 생육 저해 활성을 나타내었다. 또한 항균 물질에 의한 항미생물 활성 범위를 측정한 결과 항진균 활성 외에도 식중독균주를 포함한 그람 양성 및 음성 세균들에 강한 저해 활성을 나타내어 Lb. plantarum AF1은 넓은 항미생물 활성 범위를 가지는 것을 알 수 있었다. Lb. plantarum AF1의 생육에 따른 항진균 활성을 측정한 결과 항진균 활성은 배양 20시간부터 최대 활성(3,200 AU/ml)을 나타내어 120시간까지 활성이 감소되지 않고 유지되었다. 항진균 물질의 안정성 실험을 통하여 AF1 항진균 물질은 산성의 pH(pH $3.0{\sim}4.0$)와 열에 안정한 물질이며, 단백분해효소 처리에 영향을 받지 않으므로 비단백질성 물질이거나 단백분해효소의 영향을 받지않는 구조의 물질임을 추정하였다. AF1 항진균 물질의 분자량을 예측하기 위하여 Lb. plantarum AF1의 배양액을 3,000 Da 이상과 이하의 분획으로 나누어 항진균 활성을 측정한 결과 AF1 항진균 물질은 분자량 3,000 Da 미만의 물질임을 확인하였다. 본 실험에서 분리한 김치유산균인 Lb. plantarum AF1은 넓은 범위의 항진균 활성 및 항세균 활성을 나타내므로 강력한 천연 식품보존제 및 사료보존제로서 활용이 기대된다.