Regulation of Development in<i>Aspergillus nidulans</i>and<i>Aspergillus fumigatus</i>

Yu, Jae‐Hyuk

doi:10.4489/myco.2010.38.4.229

Cited by 124 publications

(139 citation statements)

References 40 publications

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“…While the downstream central pathway of conidiation regulated by brlA (i.e., abaA and wetA) is common to A. nidulans and A. fumigatus, the upstream pathways that activate brlA are distinct in the two species (28,40,44). In both A. nidulans and A. fumigatus, deletion of brlA eliminates conidiation completely, whereas deletion of fluG in A. fumigatus, as in our study, only reduces conidiation.…”

Section: Discussionsupporting

confidence: 47%

Deletion of the Aspergillus flavus Orthologue of A. nidulans fluG Reduces Conidiation and Promotes Production of Sclerotia but Does Not Abolish Aflatoxin Biosynthesis

Chang

Scharfenstein

Mack

et al. 2012

Appl Environ Microbiol

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The fluG gene is a member of a family of genes required for conidiation and sterigmatocystin production in Aspergillus nidulans. We examined the role of the Aspergillus flavus fluG orthologue in asexual development and aflatoxin biosynthesis. Deletion of fluG in A. flavus yielded strains with an approximately 3-fold reduction in conidiation but a 30-fold increase in sclerotial formation when grown on potato dextrose agar in the dark. The concurrent developmental changes suggest that A. flavus FluG exerts opposite effects on a mutual signaling pathway for both processes. The altered conidial development was in part attributable to delayed expression of brlA, a gene controlling conidiophore formation. Unlike the loss of sterigmatocystin production by A. nidulans fluG deletion strains, aflatoxin biosynthesis was not affected by the fluG deletion in A. flavus. In A. nidulans, FluG was recently found to be involved in the formation of dehydroaustinol, a component of a diffusible signal of conidiation. Coculturing experiments did not show a similar diffusible meroterpenoid secondary metabolite produced by A. flavus. These results suggest that the function of fluG and the signaling pathways related to conidiation are different in the two related aspergilli.A spergillus nidulans has been the model system for studying asexual conidiation at the molecular level. The genes brlA (bristle) (1), abaA (abacus) (39), and wetA (wet-white conidia) (29) are expressed sequentially and form the central developmental pathway of conidiation (17). BrlA is a transcription factor that mediates the budding growth of conidiophores. Mutations in brlA prevent vesicle formation, yielding stalks that grow indeterminately and that are unable to bear conidia (1). BrlA activates the expression of abaA, a gene that controls phialide differentiation (39). AbaA further mediates transcriptional activation of wetA (31) and also expression of brlA (3, 4). Efforts to elucidate early events leading to activation of conidiation in A. nidulans have identified six genes, fluG (fluffy) (2) and flbA to flbE (fluffy with low brlA expression), that are required for normal activation of brlA (42). Mutations of these genes result in proliferation of undifferentiated vegetative hyphae that produce fluffy cotton-like colonies. A. nidulans fluG is not transcribed in dormant conidia and is significantly downregulated during early vegetative growth; its expression before and after induction of conidiation does not change significantly (2, 7). A positive role of fluG in brlA activation has been suggested in A. nidulans, although the genetic relationship of brlA and fluG is not well defined. A. nidulans fluG mutants do not produce the secondary metabolite sterigmatocystin (20), the penultimate precursor of the carcinogenic aflatoxins. Because contact of the wild-type A. nidulans strain with the fluG null mutant remediates phenotypic defects (26), it was postulated that FluG synthesizes a diffusible factor that initiates conidiation. The effector molecules have recently ...

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Section: Discussionsupporting

confidence: 47%

Deletion of the Aspergillus flavus Orthologue of A. nidulans fluG Reduces Conidiation and Promotes Production of Sclerotia but Does Not Abolish Aflatoxin Biosynthesis

Chang

Scharfenstein

Mack

et al. 2012

Appl Environ Microbiol

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“…Together with these three genes, there are upstream regulators (flbB, flbC, flbD, flbE) required for the normal production of conidiospores. stuA and medA are considered developmental modifiers and are required for a restricted series of cell divisions that establish the spatial organization of the conidiophore (Adams et al, 1998;Etxebeste et al, 2010;Yu, 2010). We searched for orthologues of these genes in the genomes of three species of Trichoderma, to find that almost all the genes are encoded in these genomes.…”

Section: Key Actors In Conidiophore Developmentmentioning

confidence: 99%

Trichoderma: sensing the environment for survival and dispersal

2012

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“…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 central regulatory pathway that acts in concert with other genes to control the spatial and temporal specificity of gene expression during conidiophore development and spore maturation (Mirabito et al 1989;Yu 2010;Park and Yu 2012a).Activation of brlA requires activities of various upstream elements including fluG, flbA, flbB, flbC, flbD, and flbE. Mutations in any of these genes result in "fluffy" colonies that are characterized by undifferentiated cotton-like masses of vegetative cells (Adams et al 1988).…”

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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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Regulation of Development inAspergillus nidulansandAspergillus fumigatus

Cited by 124 publications

References 40 publications

Deletion of the Aspergillus flavus Orthologue of A. nidulans fluG Reduces Conidiation and Promotes Production of Sclerotia but Does Not Abolish Aflatoxin Biosynthesis

Deletion of the Aspergillus flavus Orthologue of A. nidulans fluG Reduces Conidiation and Promotes Production of Sclerotia but Does Not Abolish Aflatoxin Biosynthesis

Trichoderma: sensing the environment for survival and dispersal

NsdD Is a Key Repressor of Asexual Development inAspergillus nidulans

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