• The Korean Journal of Mycology
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• v.36 no.2
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• pp.189-195
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• 2008

When a homothallic ascomycete Aspergillus nidulans is exposed to visible light, cleistothecial development is inhibited. The light response of development in A. nidulans implies the existence of delicate regulation process including reception and translocation of light signaling and determination of development. Previously, mutants that could develop cleistothecia even in the presence of relatively intensive visible light were isolated and several complementation groups were identified. A gene that was able to complement the silA98 mutation, which was responsible for preferred cleistothecia development under visible light, was isolated from AMA-NotI genomic library. The silA gene retained in the 4.3 kb recovered genomic library DNA has an open reading frame (ORF) consisted of 2,388 bp nucleotides, interrupted by 3 introns and consequently encoding 795 amino acids. The putative SilA carries a ${Zn_2}{Cys_6}$ binuclear cluster motif at N terminus and shows high amino acid sequence similarity to Aro80p of Saccharomyces cerevisiae. Deletion mutants of silA showed a strong induction of sexual development under visible light, indicating that SilA is involved in the negative regulation of sexual development in response to the light.

• Journal of Microbiology
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• v.41 no.3
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• pp.224-231
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• 2003

The null pigmentation mutant (npgA1) of Aspergillus nidulans was previously characterized by its production of no pigment at any stage of its life cycle, its reduction in hyphal branching, and its delay in the asexual spore development. The chemical composition of the cell wall was also altered in npgA1 mutants that became more sensitive to Novozyme 234$\^$TM/, which is possibly due to a structural defect in the cell wall. To investigate the effects of the cell wall structure on these pleiomorphic phenomena, we examined the ultrastructure of the cell wall in the npgA1 mutant (WX17). Scanning electron micrographs (SEM) showed that after being cultured for six days, the outermost layer of the conidial wall of WX17 peeled off. Although this phenotype suggested that the cell wall structure in WX17 may be modified, examination using TEM of the fine structure of cross-sectioned hyphal wall of WX17 did not show any differences from that of FGSC4. However, staining for carbohydrates of wall layers showed that the electron-translucent layer of the cell wall was missing in WX17. In addition, the outermost layer H1 of the hyphal wall was also absent in WX17. The ultrastructural observation and cytochemical analysis of cell walls suggested that the pigmentation defect in WX17 may be attributed to the lack of a layer in the cell wall.

• Korean Journal of Microbiology
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• v.47 no.4
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• pp.281-288
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• 2011

To screen downstream genes of Aspergillus nidulans MsnA showing amino acid sequence similarity to the zinc finger region of Msn2/4 stress response transcription factors in Saccharomyces cerevisiae, differentially expressed genes (DEG) in MsnA overexpressed or msnA null mutant strains compared to wild type have been isolated. The cognate gene IDs were identified by DNA sequencing of the selected DEGs. Among those, DEG6 was known as mstB encoding a putative monosaccharide transporter. Expression level of mstB mRNA was increased in MsnA overproducing strains and MsnA bound directly to the promoter region of mstB in vitro. MstB containing twelve transmembrane domains exhibited 80% of amino acid sequence identities to A. niger MstA a high-affinity monosaccharide transporter. A null mutant of mstB was phenotypically undistinguishable to wild type. On the other hand, forced overexpression of MstB caused the increased formation of sexual structure cleistothecia in 0.1% glucose condition where wild type showed almost no cleistothecia. This result implies that mstB is involved in transport of monosaccharide required for sexual differentiation.

• Korean Journal of Microbiology
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• v.24 no.3
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• pp.221-227
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• 1986

The strain of Aspergillus nidulans carring a uvsH mutation which had been shown to be absolutely required for UV or 4-NQO induced mutagenic processes was studied on mitotic recombinational behaviour. Although the effect of uvsH locus on spontaneous mitotic crossing over between fpB37 and centromere was not considerable, UV-induced intergenic recombination did not occur in uvsH/uvsH homozygotic diploid. In case of gene conversion at riboflavin locus between a pair of non-complementary alleles, riboA1 and riboA3, the uvsH mutation was not concerned with that process occurred spontaneously or induced by UV irradiation. When the cells were irradiated by UV light, high degrees of aneuploid productions were detected in diploid homozygous for uvsH as compared with wild type, while much difference was not found during normal growth.

• Proceedings of the Microbiological Society of Korea Conference
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• 2006.05a
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• pp.137-137
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• 2006

• Korean Journal of Microbiology
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• v.42 no.4
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• pp.246-251
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• 2006

A lot of mutants which cannot initiate sexual development were screened and several loci including nsdA, nsdB, nsdC, and nsdD were identified in homothallic ascomycetes Aspergillus nidulans. The NSD206, which has nsdC6 allele, showed typical phenotype of NSD (Never in sexual development) mutants. The nsdC gene was cloned by transforming NSDP697 ($nsdC^-$, $pryG^-$) with AMA1-NotI genomic library. The transforming library DNA recovered from several transformants showing wild phenotype carried about 10 kb genomic DNA insert. The DNA sequence of nsdC was analysed using GPS (Genome priming system). The nsdC gene has an open reading frame (ORF) of 1,929 bp encoding a putative polypeptide of 643 amino acids. The NsdC carries $C_2H_2C_2H_2C_2HC$ type zinc finger DNA binding domains in the middle of the polypeptide. A coiled-coil domain at its C terminus were also found. In nsdC6 allele, a single T insertion was occurred between 407-408 bp leading to the frameshift mutation and early termination of translation producing the truncated protein which has only 139 amino acids.

• Korean Journal of Microbiology
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• v.17 no.3
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• pp.137-151
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• 1979

Germinating conidia of Aspergillus nidulans diploid heterozygous for color and other genetic markers were used to direct and distinguish genetic events such as mutation, mitotic crossingover and nondisjunction in a single test after treatment with N-methyl-N'-nitro-N-nitrosoguanidine (NG), mitomycin C(MC), and chloral hydrate(CH). The following results were obtained : 1. NG reduced the survival of conidia and increased the frequencies of miototic segregants about sevenfoli over the control ; among the mitotic segregants the predominant genetic event was mitotic crossingover. NG also produced many abnormal colonies, which appeared to be of the types caused by induced semidominant lethals or chromosomal aberrations, and the aneuploid types found spontaneously. 2. After treatment with MC the survival of conidia was reduced but few abnormal colonies were produced. The frequencies of miotic segregants were increased about threefold over the control ; in the mitotic segeregants the induced genetic event was mitotic crossingover. 3. CH gave no apparent effect on the survival of conidia and the frequencies of mitotic segregants. However, CH generated abnormal colonies, very greatly, which turned out to be of the aneuploid types. This result suggests that CH interferes with the normal distribution of chromosomes in mitosis.

• Journal of Microbiology and Biotechnology
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• v.26 no.5
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• pp.928-937
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• 2016

S-Nitrosoglutathione reductase (GSNOR) metabolizes S-nitrosoglutathione (GSNO) and has been shown to play important roles in regulating cellular signaling and formulating host defense by modulating intracellular nitric oxide levels. The enzyme has been found in bacterial, yeast, mushroom, plant, and mammalian cells. However, to date, there is still no evidence of its occurrence in filamentous fungi. In this study, we cloned and investigated a GSNOR-like enzyme from the filamentous fungus Aspergillus nidulans. The enzyme occurred in native form as a homodimer and exhibited low thermal stability. GSNO was an ideal substrate for the enzyme. The apparent K_m and k_cat values were 0.55 mM and 34,100 min^-1, respectively. Substrate binding sites and catalytic center amino acid residues based on those from known GSNORs were conserved in this enzyme, and the corresponding roles were verified using site-directed mutagenesis. Therefore, we demonstrated the presence of GSNOR in a filamentous fungus for the first time.

• Journal of Microbiology
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• v.41 no.1
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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.

• Korean Journal of Microbiology
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• v.47 no.4
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• pp.302-307
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• 2011

Native chitin deacetylase of Aspergillus nidulans was purified to apparent homogeneity by a combination of phenyl-Sepharose and Q-Sepharose column chromatography. In order to analyze the amino acid residues involved in the enzyme activity, the enzyme was chemically modified with chemical agent, which selectively reacted with the specific amino acid residue on the protein. When the enzyme was chemically modified with diethylpyrocarbonate, which specifically reacted with histidine residues on the protein, the activity was eliminated. The chitin deacetylase, chemically modified with 100 ${\mu}M$ modifier at the residue of arginine or tyrosine, has shown to have decreased activities. It was shown that the modification at aspartic acid or glutamic acid did not affect the enzyme activity to a greater extent, which would not implicate that acid amino residues were directly involved in catalytic reaction and would affect on the global structures of the proteins. This results demonstrated that histidine and tyrosine residues of enzyme would participate in an important function of the chitin deacetylase activity.