- Regulation of nsdD Expression in Aspergillus nidulans
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Kap Hoon Han , Kyu-Yong Han , Min-Su Kim , Dong-Beom Lee , Jong-Hak Kim , Suhn-Kee Chae , Keon-Sang Chae , Dong-Min Han
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J. Microbiol. 2003;41(3):259-261.
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 Abstract
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The nsdD gene has been predicted to encode a GATA type transcription factor with the type IVb zinc finger DNA binding domain functions in activating sexual development of A. nidulans. In several allelic mutants of nsdD producing truncated NsdD polypeptides lacking the C-terminal zinc finger, the transcription level of nsdD gene was greatly increased. Also in an over-expressed mutant, the transcription under its own promoter was reduced. These results suggest that the expression of nsdD is negatively autoregulated. When the nsdD gene was over-expressed, cleistothecia were formed in excess amounts even in the presence of 0.6M KCl that inhibited sexual development of the wild type. Northern blot analysis revealed that the expression of nsdD was repressed by 0.6M KCl. These results strongly suggest that the inhibition of sexual development by salts was carried out via the nsdD involved regulatory network.
- Environmental factors affecting development of Aspergillus nidulans
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Kap-Hoon Han , Dong-Beom Lee , Jong-Hak Kim , Min-Su Kim , Kyu-Yong Han , Won-Shin Kim , Young-Soon Park , Heui-Baik Kim^ , Dong-Min Han^
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J. Microbiol. 2003;41(1):34-40.
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Abstract
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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.
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