• Journal of Microbiology
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• 제37권1호
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• pp.27-34
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• 1999

Two fractions with unusual antifungal activity that suppress asexual sporulation of several fungi were obtained from culture filtrate of Pseudomonas aeruginosa and were partially purified through the repeated silicagel flash column chromatographies. The sporulation-suppressive actions of these fractions in Aspergillus nidulans, Rhizopus stolonifer, and Coprinus cinereus, were analyzed by light and electron microscopes. The germination ability of the spores produced in the presence of these fractions were also checked to determine the persistent effects of these antifungal substances on the next generation. Light microscopic observation of developing sporangia of R. stolonifer grown in the presence of both fractions revealed that the significant number of sporangia failed to reach maturity, and frequently, uncontrolled growths of hyphae and rhizoids from the sporangiophores were found. In A. nidulans addition of these fractions appeared to cause different classes of morphological abnormality in conidia development, which included aborted formation of conidiogenous cells from the apex of conidiophores and enhanced hyphal growths either at the tip or middle of the conidiophores. Germination abilities of spores obtained from the cultures grown in the presence of antifungal fractions were 40∼60% in Aspergillus, 50∼80% in Coprinus (thallic spores), and 30∼40% in Rhizopus compared to those of normal spores.

• Journal of Microbiology
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• 제41권1호
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• pp.34-40
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• 2003

Aspergillus nidulans, a homothalic ascomycete, has a complete sexual reproductive cycle as well as an asexual one. Both sexual and asexual development are known to be genetically programmed, but are also strongly affected by environmental factors including nutrients, light, temperature and osmolarity. We have examined these factors to define favored conditions for fruiting body (cleistothecium) formation. In general, fruiting body formation was enhanced where carbon and nitrogen sources were sufficient. Limitation of C-source caused predominant asexual development while inhibiting sexual development. When higher concentrations of glucose were supplied, more cleistothecia were formed. Other carbon sources including lactose, galactose and glycerol made the fungus develop cleistothecia very well, whereas acetate caused asexual sporulation only. Organic nitrogen sources like casein hydrolysate and glycine, and an increase in nitrate or ammonium concentration also enhanced sexual development. In addition to nutrient effects, low levels of aerobic respiration, caused either by platesealing or treatment with various chemicals, favored sexual development. Carbon limitation, light exposure and a high concentration of salts promoted asexual development preferentially, suggesting that stress conditions may drive the cell to develop asexual sporulation while comfortable and wellnourished growth conditions favored sexual development.

• The Plant Pathology Journal
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• 제36권4호
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• pp.314-322
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• 2020

Interplay between histone acetylation and deacetylation is one of the key components in epigenetic regulation of transcription. Here we report the requirement of MoHDA1-mediated histone deacetylation during asexual development and pathogenesis for the rice blast fungus, Magnaporthe oryzae. Structural similarity and phylogenetic analysis suggested that MoHDA1 is an ortholog of Saccharomyces cerevisiae Hda1, which is a representative member of class II histone deacetylases. Targeted deletion of MoHDA1 caused a little decrease in radial growth and large reduction in asexual sporulation. Comparison of acetylation levels for H3K9 and H3K14 showed that lack of MoHDA1 gene led to significant increase in H3K9 and H3K14 acetylation level, compared to the wild-type and complementation strain, confirming that it is a bona fide histone deacetylase. Expression analysis on some of the key genes involved in asexual reproduction under sporulation-promoting condition showed almost no differences among strains, except for MoCON6 gene, which was up-regulated more than 6-fold in the mutant than wild-type. Although the deletion mutant displayed little defects in germination and subsequent appressorium formation, the mutant was compromised in its ability to cause disease. Wound-inoculation showed that the mutant is impaired in invasive growth as well. We found that the mutant was defective in appressorium-mediated penetration of host, but did not lose the ability to grow on the media containing H₂O₂. Taken together, our data suggest that MoHDA1-dependent histone deacetylation is important for efficient asexual development and infection of host plants in M. oryzae.

• Mycobiology
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• 제42권1호
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• pp.1-5
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• 2014

The typical life cycle of filamentous fungi commonly involves asexual sporulation after vegetative growth in response to environmental factors. The production of asexual spores is critical in the life cycle of most filamentous fungi. Normally, conidia are produced from vegetative hyphae (termed mycelia). However, fungal species subjected to stress conditions exhibit an extremely simplified asexual life cycle, in which the conidia that germinate directly generate further conidia, without forming mycelia. This phenomenon has been termed as microcycle conidiation, and to date has been reported in more than 100 fungal species. In this review, first, we present the morphological properties of fungi during microcycle conidiation, and divide microcycle conidiation into four simple categories, even though fungal species exhibit a wide variety of morphological differences during microcycle conidiogenesis. Second, we describe the factors that influence microcycle conidiation in various fungal species, and present recent genetic studies that have identified the genes responsible for this process. Finally, we discuss the biological meaning and application of microcycle conidiation.

• 한국균학회지
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• 제22권4호
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• pp.332-337
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• 1994

Under standard condition (Han, et al., 1990: glucose 1%-nitrate 0.1% minimal medium, 30 ml in 9 cm plate, $10^6$ cells of inoculum per plate), wild type of Aspergillus nidulans developed both sexual and asexual organs in ballance, while velA1 mutant developed asexual ones preferentially. Increase of glucose concentration did not significantly affect the asexual sporulation. However, development of sexual organs were largely affected. It was greatly enhanced when favorable nitrogen source, for example, casein hydrolysate was added, which is contrary to the case of Neurospora or Saccharomyces where limitation of N source induces sexual development. On most of moderate C sources asexual development in $velA^+$ strain was largely inhibited except acetate on which only asexual spores were produced, while that in velA1 mutant strain was not affected. Lactose promoted the sexual development even in velA1 mutant indicating that lactose itself or its metabolic intermediate may induce sexual development independent of allelic state of velA gene. On other moderate favorable C sources, glycerol, galactose and ethanol, asexual development was largely inhibited in $velA^+$ strain but not in velA1 mutant strain. Sexual organs were, however, never produced on acetate. These results suggested that asexual development of wild type is largely dependent on C sources and the velA gene is involved in the repression of asexual development in not-enough-grown (non-competent) thalli resulting in preferential progression of sexual development.

• 한국균학회지
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• 제45권3호
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• pp.196-211
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• 2017

Aspergillus nidulans의 포자형성 및 무성분화에 관여하는 새로운 인자를 찾고자, 포자형성 촉진 조건인 0.6 M KCl이 첨가된 배지와 첨가되지 않은 배지에서 자란 균사체의 단백질체 분석을 시도하였다. 2DE 분석을 통해 2,400여개의 spot을 확인하였고, 무성분화 유도 9시간 및18시간 별로 생성양의 변화양상을 기준으로 총 5개의 그룹으로 나눌 수 있었다. 기능 분석이 아직까지 이루어지지 않은 단백질을 암호화하고 있는 유전자들 가운데 DU 그룹에 속하는 AN1342와 DD 그룹에 속하는 AN9419 두 개의 유전자의 기능을 알아보고자 유전자결손 돌연변이주를 제작하고 표현형을 관찰하였다. Alanine-glyoxylate aminotransferase의 기능을 할 것으로 예측되는 AN1342을 결손 시키면 무성분화 기관인 stalk의 길이가 짧아졌고, 액체 배양 시 야생형과 달리 배지로 분홍색 색소가 분비되어 sspA라 명명하였다. AN9419 결손균주는 균사생장이 심각하게 저해되고 알라닌이 첨가되어야 균사생장이 가능하였으나 무성포자 형성은 거의 이루어지지 않았으며 GO분석을 통하여 alanyl-tRNA synthetase의 기능을 할 것으로 유추된 점에 근거하여 alaA라 명명하였다.

• Journal of Microbiology
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• 제34권3호
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• pp.284-288
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• 1996

Among the bacteria isolated from compost piles of cattle excretion in a pasture located at the suburbs of Chunchon city, Pseudomonas aeruginosa KMCS-1 was selected for the test of antifungal substances produced. Six fractions were separated by silica gel column chromatography, and then the antifungal activity of each fraction was assayed against Escherichia coli, Bacillus subtilis, Candida albicans, Rhizopus sp., Aspergillus nidulans, Coprinus cinereus, and Pyricularia oryzae by paper disc method. Two fractions showed significant suppressive activities against A. nidulans, C. cinereus, and P. oryzae however, their mycelial growth was not affected by neither of these fractions. Inhibitory activities of these fractions to sporulation was assayed at the concentration of 50. 25, 12. 5, and 6.25 $\mu$g/ml and the average inhibition rates against sporulation of A. nidulans, C. cinereus, and P. oryzae were 94.0, 98.3, and 77.9%, respectively. Further purification and analysis of active substances are now being conducted.

• Mycobiology
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• 제51권5호
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• pp.273-280
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• 2023

The nucleolus is the largest, membrane-less organelle within the nucleus of eukaryotic cell that plays a critical role in rRNA transcription and assembly of ribosomes. Recently, the nucleolus has been shown to be implicated in an array of processes including the formation of signal recognition particles and response to cellular stress. Such diverse functions of nucleolus are mediated by nucleolar proteins. In this study, we characterized a gene coding a putative protein containing a nucleolar localization sequence (NoLS) in the rice blast fungus, Magnaporthe oryzae. Phylogenetic and domain analysis suggested that the protein is orthologous to Rrp8 in Saccharomyces cerevisiae. MoRRP8-GFP (translational fusion of MoRRP8 with green fluorescence protein) co-localizes with a nucleolar marker protein, MoNOP1 fused to red fluorescence protein (RFP), indicating that MoRRP8 is a nucleolar protein. Deletion of the MoRRP8 gene caused a reduction in vegetative growth and impinged largely on asexual sporulation. Although the asexual spores of DMorrp8 were morphologically indistinguishable from those of wild-type, they showed delay in germination and reduction in appressorium formation. Our pathogenicity assay revealed that the MoRRP8 is required for full virulence and growth within host plants. Taken together, these results suggest that nucleolar processes mediated by MoRRP8 is pivotal for fungal development and pathogenesis.

• Mycobiology
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• 제31권2호
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• pp.86-94
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• 2003

The effect of four sub-lethal concentrations(400, 800, 1,200 and 1,600 ${\mu}g/ml$) of three amino acids such as isoluecine, aspartic acid and phenylalanine on vegetative growth and sexual and asexual reproduction of Achlya racemosa, A. proliferoides and Saprolegnia furcata was investigated. The density of vegetative growth and diameters of vegetative colonies of species of the Oomycetes fungi decreased with rising the concentration of the applied amino acid. Vegetative hyphae of treated fungi almost appeared branched in case of S. furcata, thick in case of A. racemosa and distorted in case of A. proliferoides as compared with control. The different treatments with amino acids depressed both sporangial formation and discharge, which were dependent on the tested species of zoosporic fungi, the amino acid and its dosage. Phenylalanine was the most effective amino acid in inhibiting sporulation and S. furcata was the most sensitive fungal species. Aspartic acid and isoleucine stimulated germination of discharged spores through the formation of germlings. Gemmae formation by the three fungi was reduced at the low concentrations of amino acids and nearly missed at high concentrations. Sex organs(oogonia and antheridia) were affected partly; rudiment oogonia were observed at low concentrations(400 and 800 ${\mu}g/ml$) and disappeared at higher concentrations, whereas antheridial branch formation was stimulated as the fungi were treated with isoleucine and to some extent phenylalanine.

• 한국균학회지
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• 제18권4호
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• pp.225-232
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• 1990

몇몇 배양조건이 유성 또는 무성분화에 미치는 영향을 조사하여, 유성분화 결손 돌연변이주를 분리하기 위한 효율적인 조건을 찾고자 하였다. 무성분화는 억제하며, 유성분화는 촉진시키는 여러조건중 Casein hydrolysate를 첨가한 최소배지에 밀봉 배양하는 것이 가장 효율적인 조건으로 선택되었다. 접종 후 20시간 이전에 밀봉하고 계속 배양하면, 유 무성분화 모두가 억제되나, 밀봉 후 20시간 정도 후에 밀봉을 해제하면 유성분화만이 진행되었다. 이러한 성질을 이용하여 유성분화과정에 이상이 일어난 돌연변이주를 대랑 분리해 냈었으며, 이들의 분화양상에 따라 크게 3 group : NSD(never in sexual development), BSD(block in sexual development), ASD(abnormal in sexual development)으로 분류하였다. NSD 돌연변이주는 $H{\ddot{u}}lle$ cell이나 cleistothecia 등의 유성생식기관을 전혀 생성하지 못하였고, BSD 돌연변이주는 $H{\ddot{u}}lle$ cell, cleistothecia, crozier, asci 또는 ascospore 형성 중 어느 과정에서 중단되어 분화가 끝가지 진행되지 못하였으며, ASD 돌연변이주는 유성분화의 최종단계가지 진행은 되지만 유성생식 기관의 생성시기나 양이 야생형과 현저하게 차이를 보였다.