Gene control of developmental competence in Aspergillus nidulans

Axelrod, David E.; Gealt, Michael A.; Pastushok, M.

doi:10.1016/0012-1606(73)90335-7

Cited by 118 publications

(119 citation statements)

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“…These results suggest that the VosA-VelB heterodimer activates expression of NsdD in conidia, which confers proper downregulation of brlA during the initial period of vegetative growth. It has been shown that conidiation does not typically occur in A. nidulans until cells have gone through a defined period ($18 hr) of vegetative growth (Axelrod et al 1973;Champe et al 1981); i.e., A. nidulans cells require $18 hr of growth before they are competent to conidiate. It is important to note that the deletion of both nsdD and vosA might have reduced this developmental competence period to 16 hr or earlier ( Figure 6, B and C).…”

Section: Discussionmentioning

confidence: 99%

NsdD Is a Key Repressor of Asexual Development inAspergillus nidulans

et al. 2014

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Asexual development (conidiation) of the filamentous fungus Aspergillus nidulans occurs via balanced activities of multiple positive and negative regulators. For instance, FluG (+) and SfgA (2) govern upstream regulation of the developmental switch, and BrlA (+) and VosA (2) control the progression and completion of conidiation. To identify negative regulators of conidiation downstream of FluG-SfgA, we carried out multicopy genetic screens using sfgA deletion strains. After visually screening .100,000 colonies, we isolated 61 transformants exhibiting reduced conidiation. Responsible genes were identified as AN3152 (nsdD), AN7507, AN2009, AN1652, AN5833, and AN9141. Importantly, nsdD, a key activator of sexual reproduction, was present in 10 independent transformants. Furthermore, deletion, overexpression, and double-mutant analyses of individual genes have led to the conclusion that, of the six genes, only nsdD functions in the FluG-activated conidiation pathway. The deletion of nsdD bypassed the need for fluG and flbA$flbE, but not brlA or abaA, in conidiation, and partially restored production of the mycotoxin sterigmatocystin (ST) in the DfluG, DflbA, and DflbB mutants, suggesting that NsdD is positioned between FLBs and BrlA in A. nidulans. Nullifying nsdD caused formation of conidiophores in liquid submerged cultures, where wild-type strains do not develop. Moreover, the removal of both nsdD and vosA resulted in even more abundant development of conidiophores in liquid submerged cultures and high-level accumulation of brlA messenger (m)RNA even at 16 hr of vegetative growth. Collectively, NsdD is a key negative regulator of conidiation and likely exerts its repressive role via downregulating brlA.T HE filamentous ascomycete Aspergillus nidulans has served as an excellent model system for studying cell biology, asexual development (conidiation), and secondary metabolism (Timberlake 1990;Martinelli 1994;Yu and Keller 2005). The A. nidulans asexual reproductive cycle can be divided into two distinct phases: growth and development. The growth phase involves germination of an asexually derived spore called a conidium and formation of an undifferentiated network of interconnected hyphal cells that form the mycelium. After a certain vegetative growth period, under appropriate conditions, some of the hyphal cells stop normal growth and begin development by forming complex structures called conidiophores that bear multiple chains of conidia (Adams et al. 1988;Park and Yu 2012a).A key and essential step for conidiophore development in Aspergillus is the activation of brlA, which encodes a C 2 H 2 zinc-finger transcription factor (TF) ( Figure 1A) (Adams et al. 1988;Chang and Timberlake 1993). Further genetic and biochemical studies identified the additional key regulators abaA and wetA that function during the middle and late stages of conidiation, respectively ( Figure 1A) (Sewall et al. 1990;Andrianopoulos and Timberlake 1991;Marshall and Timberlake 1991). These three genes have been proposed to define a c...

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Section: Discussionmentioning

confidence: 99%

NsdD Is a Key Repressor of Asexual Development inAspergillus nidulans

et al. 2014

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“…Colonies do not normally conidiate in submerged culture but do if they have acquired competence and are subsequently exposed to an air interface (Axelrod et al 1973). The transfer of mycelia from liquid to surface culture, termed induction, initiates and synchronizes asexual development (Timberlake 1980).…”

Section: A Nidulans Responds To Light At a Specific Period Followingmentioning

confidence: 99%

“…The extrinsic environmental conditions required for initiating sporulation in this organism are poorly understood. It has been shown previously that conidiation is strongly inhibited in submerged culture but occurs readily when the mycelia are exposed to an air interface (Morton 1961;Axelrod et al 1973). The physiological basis for this effect does not appear to involve an osmotic change, because conidiation occurs in surface cultures when the atmosphere is saturated with water (Timberlake and Hamer 1986).…”

mentioning

confidence: 96%

Light is required for conidiation in Aspergillus nidulans.

Mooney¹,

Yager²

1990

Genes Dev.

274

195

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Light is necessary for asexual sporulation in Aspergillus nidulans but will elicit conidiation only if irradiation occurs during a critical period of development. We show that conidiation is induced by red light and suppressed by an immediate shift to far red light. Conidiation-specific gene functions switch from light-independent to light-dependent activities coincident with the expression of brlA, a regulator of conidiophore development. We also show that light dependence is abolished by a mutation in the velvet gene, which allows conidiation to occur in the absence of light. We propose that the initiation of late gene expression is regulated by velvet and controlled by a red light photoreceptor, whose properties are reminiscent of phytochrome-mediated responses observed in higher plants.

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“…After growing to a certain age, mycelia acquire competence for development after which differentiation is normally induced by air exposure (Axelrod et al 1973). Environmental factors that affect the growth of mycelia-including nutritional status, culture conditions, and some environmental stresses-are responsible for developmental decisions determining sexual or asexual reproduction (Zonneveld 1977;Han et al 1990Han et al , 2003Han et al , 2007.…”

mentioning

confidence: 99%

ThensdCGene Encoding a Putative C2H2-Type Transcription Factor Is a Key Activator of Sexual Development inAspergillus nidulans

Kim¹,

Chae

Han

et al. 2009

Genetics

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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 2 H 2 's and a C 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 nsdC also 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 not rescue the failure of fruiting body formation caused by nsdC deletion. Furthermore, nsdC expression is not affected by either VeA or NsdD, and vice versa, indicating that NsdC regulates sexual development independently of VeA or NsdD.

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Gene control of developmental competence in Aspergillus nidulans

Cited by 118 publications

References 13 publications

NsdD Is a Key Repressor of Asexual Development inAspergillus nidulans

NsdD Is a Key Repressor of Asexual Development inAspergillus nidulans

Light is required for conidiation in Aspergillus nidulans.

ThensdCGene Encoding a Putative C2H2-Type Transcription Factor Is a Key Activator of Sexual Development inAspergillus nidulans

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