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31. The nsdC gene encoding a putative [C.sub.2][H.sub.2]-type transcription factor is a key activator of sexual development in Aspergillus nidulans

Author

Kim, Hye-Ryun, Chae, Keon-Sang, Han, Kap-Hoon, and Han, Dong-Min

Subjects
Genetic code -- Research, Gene expression -- Physiological aspects, Transcription factors -- Properties, Aspergillus -- Growth, Aspergillus -- Genetic aspects, Developmental genetics -- Research, Company growth, Biological sciences
Abstract

The formation of the Aspergillus nidulans fruiting body is affected by a number of genetic and environmental factors. Here, the nsdC (never in sexual development) gene--encoding a putative transcription factor carrying a novel type of zinc-finger DNA-binding domain consisting of two [C.sub.2][H.sub.2]'s and a [C.sub.2]HC motif that are highly conserved in most fungi but not in plants or animals--was investigated. Two distinct transcripts of 2.6 and 3.0 kb were generated from nsdC. The 2.6-kb mRNA accumulated differentially in various stages of growth and development, while the level of the 3.0-kb mRNA remained relatively constant throughout the life cycle. While the deletion of nsdC resulted in the complete loss of fruiting body formation under all conditions favoring sexual development, overexpression of nsdC not only enhanced formation of fruiting bodies (cleistothecia) but also overcame inhibitory effects of certain stresses on cleistothecial development, implying that NsdC is a key positive regulator of sexual development. Deletion of nsdCalso retarded vegetative growth and hyperactive asexual sporulation, suggesting that NsdC is necessary not only for sexual development but also for regulating asexual sporulation negatively. Overexpression of veA or nsdD does hot rescue the failure of fruiting body formation caused by nsdC deletion. Furthermore, nsdCexpression is hot affected by either VeA or NsdD, and vice versa, indicating that NsdC regulates sexual development independently of VeA or NsdD. DOI: 10.1534/genetics.109.101667

Published
2009

34. The GanB G[alpha]-protein negatively regulates asexual sporulation and plays a positive role in conidial germination in Aspergillus nidulans

Author

Chang, Mi-Hee, Chae, Keon-Sang, Han, Dong-Min, and Jahng, Kwang-Yeop

Subjects
Proteins -- Research, Biological sciences
Abstract

We isolated the ganB gene encoding the G[alpha]-protein homolog from Aspergillus nidulans. To investigate the cellular function of GanB, various mutant strains were isolated. Deletion of constitutively inactive ganB mutants showed conidiation and derepressed brlA expression in a submerged culture. Constitutive activation of GanB caused a reduction in hyphal growth and a severe defect in asexual sporulation. We therefore propose that GanB may negatively regulate asexual sporulation through the BrlA pathway. In addition, deletion or constitutive inactivation of GanB reduced germination rate while constitutive activation led to precocious germination. Furthermore, conidia of a constitutively active mutant could germinate even without carbon source. Taken together, these results indicated that GanB plays a positive role during germination, possibly through carbon source sensing, and negatively regulates asexual conidiation in A. nidulans.

Published
2004

48. Membrane-Bound Methyltransferase Complex VapA-VipC-VapB Guides Epigenetic Control of Fungal Development

Author

Sarikaya-Bayram, Ozlem, Bayram, Ozgur, Feussner, Kirstin, Kim, Jong-Hwa, Kim, Hee-Soo, Kaever, Alexander, Feussner, Ivo, Chae, Keon-Sang, Han, Dong-Min, Han, Kap-Hoon, Braus, Gerhard H., Sarikaya-Bayram, Ozlem, Bayram, Ozgur, Feussner, Kirstin, Kim, Jong-Hwa, Kim, Hee-Soo, Kaever, Alexander, Feussner, Ivo, Chae, Keon-Sang, Han, Dong-Min, Han, Kap-Hoon, and Braus, Gerhard H.

Abstract

Epigenetic and transcriptional control of gene expression must be coordinated in response to external signals to promote alternative multicellular developmental programs. The membrane-associated trimeric complex VapA-VipC-VapB controls a signal transduction pathway for fungal differentiation. The VipC-VapB methyltransferases are tethered to the membrane by the FYVE-like zinc finger protein VapA, allowing the nuclear VelB-VeA-LaeA complex to activate transcription for sexual development. Once the release from VapA is triggered, VipCVapB is transported into the nucleus. VipC-VapB physically interacts with VeA and reduces its nuclear import and protein stability, thereby reducing the nuclear VelB-VeA-LaeA complex. Nuclear VapB methyltransferase diminishes the establishment of facultative heterochromatin by decreasing histone 3 lysine 9 trimethylation (H3K9me3). This favors activation of the regulatory genes brlA and abaA, which promote the asexual program. The VapA-VipCVapB methyltransferase pathway combines control of nuclear import and stability of transcription factors with histone modification to foster appropriate differentiation responses.

Published
2014

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