Miriam Krüger

Philipps University of Marburg, Marburg, Hesse, Germany

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Publications (3)16.4 Total impact

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    M Krüger · R Fischer
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    ABSTRACT: Genetic features determine the site of polarized growth in filamentous fungi and lead to hyphal tip extension or subapical branching. We have isolated the samB gene (suppressor of anucleate metulae) of Aspergillus nidulans which encodes a 66 kDa protein carrying an atypical Cys4 and an additional Cys2/His/Cys Zn finger motif at the carboxy-terminus. Such novel Zn finger-like domains have recently been found in several other developmental regulators in organisms ranging from yeast to man. Deletion of this domain at the carboxy-terminus of SamB led to premature hyphal ramification, mislocalization of septa and suppression of the asporogenous phenotype of the developmental mutant aps (anucleate primary sterigmata). A DeltasamB deletion strain displayed an identical phenotype. A homologous gene in Saccharomyces cerevisiae was also characterized whose deletion resulted in a multi-budding phenotype; thus it was named MUB1. An underlying common mechanism for both genes in determination of the onset of polarized growth and its links to other cellular developmental processes is discussed.
    Preview · Article · Feb 1998 · The EMBO Journal
  • Nicole Sievers · Miriam Krüger · Reinhard Fischer
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    ABSTRACT: Aspergillus nidulans ist ein filamentöser Schlauchpilz (Euascomycet), der ubiquitär im Boden verbreitet ist und auch im Labor sehr leicht kultiviert werden kann. Dieser Pilz eignet sich neben anderen Pilzarten, wie Schizosaccharomyces (die Spalthefe) oder Neurospora (der Brot- oder Bäckerschimmel), sehr gut für genetische Untersuchungen. Er kann sich asexuell durch Konidiosporen und sexuell durch Ascosporen vermehren. Der sexuellen Sporenbildung kann eine Paarung unterschiedlicher Stämme vorangehen, was in Kreuzungsexperimenten ausgenutzt wird. Bei einer Kreuzung kann man beispielsweise Mutanten verwenden, die Defekte in Genen der Pigmentbiosynthese aufweisen, wodurch sie leicht phänotypisch unterschieden werden können (Abbildung 1). Die unterschiedlichen Phänotypen treten direkt wieder bei den Nachkommen einer Kreuzung auf, da es sich bei A. nidulans um einen haploiden Organismus handelt. Neben den Mutationen in den Genen für die Pigmentbiosynthese kommen bei A. nidulans viele weitere Mutanten vor, in denen bestimmte Enzyme von Stoffwechselwegen defekt sind. Diese können durch Kultivierung der Stämme auf Selektivmedien festgestellt werden (siehe unten).
    No preview · Article · Nov 1997 · Biologie in unserer Zeit
  • Source
    Miriam Krüger · Reinhard Fischer
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    ABSTRACT: Aspergillus nidulans reproduces asexually with single nucleated conidia. In apsA (anucleate primary sterigmata) strains, nuclear positioning is affected and conidiation is greatly reduced. To get further insights into the cellular functions of apsA, aconidial apsA strains were mutagenized and conidiating suppressor strains were isolated. The suppressors fell into two complementation groups, samA and samB (suppressor of anucleate metulae), samA mapped on linkage group 1 close to pyrG. The mutant allele was dominant in diploids homozygous for apsA. Viability of conidia of samA suppressor strains (samA-; apsA-) was reduced to 50% in comparison to wild-type conidia. Eighty percent of viable spores produced small size colonies that were temperature and benomyl-sensitive. samB mapped to chromosome VIII and was recessive. Viability of conidia from samB suppressor strains (apsA-; samB) was also affected but no small size colonies were observed. Both suppressors produced partial defects in sexual reproduction and both suppressed an apsA deletion mutation. In wild-type background the mutant loci affected hyphal growth rate (samA) or changed the colony morphology (samB) and inhibited sexual spore formation (samA and samB). Only subtle effects on conidiation were found. We conclude that both suppressor genes bypass the apsA function and are involved in microtubule-dependent processes.
    Preview · Article · Nov 1996 · Genetics