Genetic regulation of Aspergillus nidulans conidiophore development by fluG abd flbA /
The filamentous fungus Aspergillus nidulans reproduces asexually by forming thousands of spores atop multicellular organs termed conidiophores. Initiation of conidiophore development requires a development-specific transcription factor called brla. Mutations in ftba, flbb, flbc, flbd, flbe (fluff...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742535201&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The filamentous fungus Aspergillus nidulans reproduces asexually by forming thousands of spores atop multicellular organs termed conidiophores. Initiation of conidiophore development requires a development-specific transcription factor called brla. Mutations in ftba, flbb, flbc, flbd, flbe (fluffy low brIA) and flug (fluffy) fail to activate brIA or conidiation. These mutants produce masses of aerial hyphae and form cotton-like colonies described as "fluffy". This dissertation describes the characterization of the enes 9 identified by the flug and flba mutations and examination of their roles in controlling development. The flug mutant phenotype can be suppressed extracellularly by growth next to a wild-type colony, even when the two colonies are separated by dialysis membrane having a 6-8 kd molecular weight cut-off, indicating that flug is required for the production of an extracellular factor that stimulates conidiation. The requirement for flug can be substituted by nutrient limitation, suggesting that brIA can be activated in more than one way, one requires flug and another is flug-independent. FluG is a 96 kd cytoplasmic protein that is present constitutively during the A. nidulans lifecycle. The carboxyl-terminal half of FluG polypeptide has 28% identity to prokaryotic glutamine synthetase I leading us to propose that FluG has an enzymatic role related to glutamine synthetase in synthesizing the conidiation signal. Overexpression of flug in A. nidulans hyphae causes conidiophore development and brla expression indicating that flug is an early regulator of conidiation. flba mutants have a distinct fluffy phenotype characterized by interwoven aerial hyphae that autolyse as the colony matures. flba encodes a 717-amino acid polypeptide with 30% identity to Saccharomyces cerevisiae SST2, a protein required for normal regulation of the signaling pathway for response to mating pheromone. Overexpression of flba, like flug, results in inappropriate activation of brIA and conidiation. flba and flug are each required for overexpression of the other to cause development suggesting a close relationship between these two genes. I propose a model for control of conidiophore development in which FluG is a signal producer and FIBA is the signal transducer (see Figure 6-7). |
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| Item Description: | Vita. "Major Subject: Microbiology". |
| Physical Description: | xi, 164 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |