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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Sporulation in the yeast Saccharomyces cerevisiae is a meiotic developmental process that occurs in MAT a/MATα heterozygotes in response to nutrient deprivation. Here, the fate and role of peroxisomes during sporulation and germination has been examined by a combination of immunoelectron microscopy and the use of pex mutants defective in peroxisomal functions. Using a green fluorescent protein probe targeted to peroxisomes we show that peroxisomes are inherited through meiosis and that they do not increase in number either during sporulation or spore germination. In addition, there is no requirement for peroxisome degradation prior to spore packaging. Unlike the situation in filamentous fungi, peroxisomes do not proliferate during the yeast life cycle. Functional peroxisomes are dispensable for efficient meiotic development on acetate medium since homozygous Δpex6 diploids sporulated well and produced mature spores that were resistant to diethyl ether. Like haploids, diploid cells can proliferate their peroxisomes in response to oleate as sole carbon source in liquid medium, but under these conditions they do not sporulate. On solid oleate medium, homozygous pex5,Δpex6, and pex7 cells were unable to sporulate efficiently, whereas the wild type was. The results presented here are discussed in terms of the transmission of organelles to progeny cells.
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  • 2
    ISSN: 1432-0983
    Keywords: Key wordsCOX1 ; Intron ; Yeast ; Promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Screening of a promoter probe gene bank for DNA sequences that could act as inducible promoters following growth on non-fermentable carbon sources led to the identification of the mitochondrially encoded cytochrome oxidase subunit 1 gene (COX1) as an active sequence. Carbon-source regulation of this promoter was confirmed by a β-galactosidase assay which showed a 31- and 180-fold induction of expression after growth on ethanol or lactate-based media respectively. Two elements matching the CCAAT-binding-factor motif, which is involved in activating transcription on non-fermentable carbon sources, were identified in the putative promoter. Expression was found to be reduced to low levels in otherwise isogenic hap3 and hap4 mutant strains. Thus, this mitochondrial DNA when placed in the nucleus can act as a promoter that is subject to strict carbon-source regulation. These observations are discussed both with respect to the origin of the S. cerevisiae COX1 gene in particular and with respect to the origin of introns in general.
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  • 3
    ISSN: 1432-0983
    Keywords: Key wordsSaccharomyces cerevisiae ; Oxidative stress ; Ageing ; Gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The UTH1 gene was identified by screening a Saccharomyces cerevisiae promoter-probe gene bank for oxidative stress-responsive genes. Transcription of UTH1 was decreased by the superoxide anion and increased by hydrogen peroxide. Deletion of UTH1 did not affect the growth of grande cells, however in a ρ 0 background it caused retarded growth. The uth1 mutant showed increased resistance to peroxides and, in contrast, was sensitive to superoxide or the thiol oxidant diamide. Furthermore, the mutant exhibited increased survival under starvation conditions, with elevated levels of dormant cells in starved cell cultures. A multicopy plasmid containing the first half of the ORF could confer increased resistance to superoxide and increased sensitivity to peroxides/diamide/starvation on wild-type cells. The same plasmid in the uth1 background caused a highly increased mortality.
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  • 4
    ISSN: 1432-072X
    Keywords: Bacillus subtilis ; Spores ; Outgrowth ; Inhibition ; chloroquine ; Synergism ; Ionophores ; Membrane potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloroquine inhibited the outgrowth of Bacillus subtilis spores at a 10-fold lower concentration than that required to prevent vegetative growth. Analysis of macromolecular synthesis in outgrowing spores and vegetative cells in the presence of chloroquine indicated that it acted preferentially on transcription. Differential sensivivity of outgrowing spores and vegetative cells to chloroquine was not due to changes in the specificity of the RNA-polymerase, since RNA-polymerase activity measured in permeabilized cells was not affected differently by the drug. The preferential inhibition of spore outgrowth was not evident at pH 8.0, at which the majority of chloroquine is in a monovalent, more lipophilic, form. In the presence of inhibitors affecting membrane potential, vegetative cells were as sensitive to chloroquine as outgrowing spores. Measurement of [14C]-chloroquine uptake showed that early outgrowing spores accumulated twice as much drug as resistant late outgrowing spores and seven times more than vegetative cells. Treatment of vegetative cells with metabolic inhibitors led them to accumulate chloroquine to the levels found in outgrowing spores. Therefore, the preferential inhibition of outgrowing spores by chloroquine is the result of increased uptake of the drug, reflecting differences in energy metabolism from vegetative cells.
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  • 5
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; Oleate response element (ORE) ; Pip2p-Oaf1p ; Peroxisome ; SPS19
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Saccharomyces cerevisiae cells grown on oleic acid, genes encoding enzymes of β-oxidation are induced by the interaction of a transcription factor composed of Pip2p and Oaf1p with an oleate response element (ORE) in their promoters. The SPS19 gene, which encodes peroxisomal 2,4-dienoyl-CoA reductase, an auxiliary β-oxidation enzyme, has been shown previously to be up-regulated by a canonical ORE. To determine whether additional elements contribute to this transcriptional up-regulation, deletion analysis of the SPS19 promoter was conducted using SPS19-lacZ reporter genes. In a reporter construct containing a deletion adjacent to the ORE, transcriptional activation of SPS19 in oleic acid medium was impaired. Together with an additional segment that overlaps a portion of the canonical ORE, this region forms a continuous element (termed UASSPS19) that is essential for de-repression of SPS19 when glucose levels are low. The potentially bi-partite UASSPS19 element was able to initiate bi-directional transcription from a promoterless CYC1-lacZ reporter construct under de-repression conditions, whereas the canonical ORE was not. In oleic acid-containing medium, UASSPS19 stimulated transcription of the reporter gene 2.4-fold compared to the intact SPS19 ORE, but did so only in the presence of Pip2p and Oaf1p. UASSPS19, which is similar to a transcriptional enhancer in the promoter of the sporulation-specific gene SPS4, was shown specifically to bind several proteins, including Pip2p and Oaf1p. We propose that UASSPS19 and other sequences like it are required to enhance the transcriptional effects mediated by more specific response elements.
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  • 6
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Temperature-sensitive mutants defective in bacterial spore outgrowth have been isolated and in all cases examined have also been found to be blocked in vegetative growth at the restrictive temperature. Four of these mutants have been studied to determine the stage at which outgrowth is blocked, the period of development when they are sensitive to the restrictive condition, and their ability to undergo macromolecular synthesis. These mutants were blocked at various stages of outgrowth during swelling and elongation. Once the point in development had been reached at which they were sensitive to the restrictive condition, they remained sensitive at all further stages of development. One very interesting mutant (ts 8) showed a constant time lag of one hour between the shift to the restrictive condition and expression of the resulting lesion, provided that the mutant was maintained for that time at the restrictive temperature. None of the mutants responded to diffusible substrates produced by the wild-type during germination and outgrowth.
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A well-defined set of isogenic yeast strains has been constructed whereby each strain contains a different LPD::lacZ gene fusion integrated at the ura3 locus. These LPD::lacZ fusions differ in the amount of the LPD1 gene (encoding lipoamide dehydrogenase) that is fused to the lacZ reporter. Comparison of the β-galactosidase activities of each strain during growth on glucose or ethanol revealed that some part of the LPD1 coding region between +13 and +700 is involved in activating gene expression in a carbon source-dependent manner. This activation occurs at the mRNA level, and is not mediated by changes in mRNA stability. Therefore, the LPD1 gene appears to contain a transcriptional enhancer that lies 3′ to the transcriptional start site, and which responds to carbon source.
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  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The nature of the growth medium determines both the packing and the position of the chromosomes and this in turn apparently determines whether the cells will grow or ...
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