Phenotypes of Double Conidiation Mutants of Aspergillus nidulans

Martinelli, Sylvia D.

doi:10.1099/00221287-114-2-277

Cited by 42 publications

(21 citation statements)

References 6 publications

(2 reference statements)

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“…At the morphological level, brlA mutations are epistatic to abaA and wetA mutations and abaA mutations are epistatic to wetA mutations (9). We determined that these epistatic relationships were manifested at the molecular level.…”

Section: Resultsmentioning

confidence: 99%

Isolation and physical characterization of three essential conidiation genes from Aspergillus nidulans.

Boylan¹,

Mirabito²,

Willett³

et al. 1987

Mol. Cell. Biol.

201

187

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We cloned and characterized three genes from Aspergillus nidulans, designated brUA, abaA, and wetA, whose activities are required to complete different stages of conidiophore development. Inactivation of these genes causes major abnormalities in conidiophore morphology and prevents expression of many unrelated, developmentally regulated genes, without affecting the expression of nonregulated genes. The three genes code for poly(A)+ RNAs that begin to accumulate at different times during conidiation. The briA-and abaA-encoded RNAs accumulate specifically in cells of the conidiophore. The weL4-encoded RNA accumulates in mature conidia. Inactivation of the brL4 gene prevents expression of the abaA and wet4 genes, whereas inactivation of the abaA gene prevents expression of the wetA gene. Our results confirm genetic predictions as to the temporal and spatial patterns of expression of these genes and demonstrate that these patterns are specified at the level of RNA accumulation.The mitotically derived spores, or conidia, of the ascomycetous fungus Aspergillus nidulans are produced on multicellular structures called conidiophores (14). Scanning electron microscope images of developing conidiophores are shown in Fig. 1. Under appropriate conditions, certain hyphal elements (Fig. 1A) differentiate into thick-walled foot cells and produce aerial stalk initials (Fig. 1B). The stalks grow away from the substratum for a defined period of time, growth stops, and a multinucleated vesicle forms by swelling of the stalk apex (Fig. 1C). A layer of primary sterigmata, or metullae, is formed on the surface of the vesicle by budding (Fig. 1D), and a single nucleus enters each cell. The metullae undergo a single division to produce a layer of secondary sporogenous sterigmata, or phialides (Fig. 1E). Conidia are formed following mitotic divisions of the phialide nucleus (Fig. 1F). After each division, one daughter nucleus is retained within the phialide, where it continues to undergo mitoses. The other daughter nucleus enters the tip of the phialide which buds off to form a conidium. As this process continues, previously formed conidia are displaced by newly formed conidia, producing a long chain of clonally derived spores at various stages of maturity. We have previously shown that conidiophore development in A. nidulans involves the stage-and cell-type-specific expression of approximately 1,000 different genes (15).The genetic mechanisms that control the differentiation and spatial organization of conidiophore cells have been investigated by Clutterbuck and co-workers, who isolated a variety of mutant strains with altered conidiophore morphologies (1,2,4,10). Many of the mutations they studied are conidiophore specific, having little or no detectable effect on hyphal growth or sexual reproduction. The mechanisms by which the genes identified by these mutations bring about the orderly assembly of the asexual reproductive apparatus are unknown.Mutations in three genes cause major developmental defects and thus are of particular inter...

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Section: Resultsmentioning

confidence: 99%

Isolation and physical characterization of three essential conidiation genes from Aspergillus nidulans.

Boylan¹,

Mirabito²,

Willett³

et al. 1987

Mol. Cell. Biol.

201

187

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“…It has been suggested that the conidiophore morphology of stuA mutants is a function of incorrect temporal or spatial expression of phialide-specific genes such as abaA. The result is a failure to differentiate metulae or phialides, and conidia are produced from buds on the conidiophore vesicle (Martinelli 1979;Miller et al 1991). Strain UI49 was constructed to test this hypothesis.…”

Section: Stua Is Required For Correct Spatial Expression Of the Abaa mentioning

confidence: 99%

“…They affect patterns of cell differentiation and the spatial organization of the conidiophore (Clutterbuck 1969;Martinelli 1979;Miller et al 1991J. stuA null mutants have greatly shortened conidiophores and lack normal metulae and phialides.…”

mentioning

confidence: 99%

“…Correct cell pattern formation requires the functions of at least five genes: abacus (abaA); bristle (brlA); medusa (medA); stunted (stuA); and wet-white conidia {wetAI (Clutterbuck 1969(Clutterbuck , 1977Martinelli and Clutterbuck 1971). Epistatic relationships suggest that these postinduction loci define two separate genetic pathways with some interaction, or overlap, in function (Martinelli 1979). The BRISTLE group of genes (brlA --, abaA --~ wetA) define a linear path of differentiation that cul~Corresponding author.…”

mentioning

confidence: 99%

“…Therefore, BrlA expression is necessary and sufficient to direct the linear transition from vegetative hyphae to conidia. Normal patterns of cell differentiation, however, require additional regulatory phenomena (Clutterbuck 1977;Martinelli 1979).…”

mentioning

confidence: 99%

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StuA is required for cell pattern formation in Aspergillus.

Miller¹,

Wu²,

Miller³

1992

Genes Dev.

189

209

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The stunted (stuA) gene product is required for the orderly differentiation and spatial organization of cell types of the Aspergillus nidulans conidiophore. Expression of the stuA gene is complex. Two transcripts, stuA~ and stuA~, are initiated from separate promoters. Transcription of both RNAs increases -50-fold during the establishment of developmental competence. Induction-dependent transcriptional and post-transcriptional regulatory mechanisms further enhance expression 15-fold. Consistent with the latter observation, both transcripts have structural features characteristic of RNAs subject to translational control. Conidiophore morphogenesis requires regulatory interactions between the products of the stuA, bristle (brlA), and abacus (abaA) genes. Enhanced stunted expression is cell type specific and dependent on a functional BrlA protein.StuA affects the spatial localization of AbaA by acting directly, or indirectly, to repress abaA expression.

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The Aspergillus nidulans brlA regulatory locus consists of overlapping transcription units that are individually required for conidiophore development.

1993

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The Aspergillus nidulans brlA locus controls conidiophore development in conjunction with the products of several other regulatory loci. In this paper, we show that the brlA locus consists of overlapping transcription units, designated alpha and beta, with alpha transcription initiating within beta intronic sequences. The predicted BrlA polypeptides differ by 23 amino acid residues at their N‐termini. Targeted mutations specifically eliminating either the alpha or beta transcript led to developmental abnormalities similar to those produced by previously identified hypomorphic mutants, showing that both transcripts have essential functions for normal development. However, provision of additional doses of alpha in a beta‐ strain or of beta in an alpha‐ strain remediated the developmental defects, indicating that the polypeptides have redundant functions. It is likely that differential regulation of alpha and beta expression in the wild type is important for the initiation and temporal regulation of development.

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Phenotypes of Double Conidiation Mutants of Aspergillus nidulans

Cited by 42 publications

References 6 publications

Isolation and physical characterization of three essential conidiation genes from Aspergillus nidulans.

Isolation and physical characterization of three essential conidiation genes from Aspergillus nidulans.

StuA is required for cell pattern formation in Aspergillus.

The Aspergillus nidulans brlA regulatory locus consists of overlapping transcription units that are individually required for conidiophore development.

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