A CIS-DOMINANT MUTATION IN ASPERGILLUS NIDULANS AFFECTING THE EXPRESSION OF THE amdS GENE IN THE PRESENCE OF MUTATIONS IN THE UNLINKED GENE, amdA
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ABSTRACT A mutant producing very high levels of the acetamidase enzyme encoded by the amdS gene has been isolated in a strain containing the amdA7 mutation, which itself causes high levels of this enzyme. Genetic analysis has shown that this mutation, designated amdI66, is adjacent to the amdS gene and is cis-dominant in its effect. The amdI66 mutation has little effect on amdS expression when present in strains not containing the amdA7 mutation. Two other amdA mutations investigated also interact with the amdI66 mutation to result in high acetamidase levels. No interaction between amdI66 and any of the other putative regulatory genes affecting amdS expression has been observed. The amdI66 mutation has been located by fine structure mapping at the extreme end of the controlling region, which has previously been defined by genetic mapping (Hynes 1979). Analysis of this region has been extended by mapping new mutations resulting in loss of amdS expression. One of these defines the most extreme site capable of mutation to loss of gene function found so far.Keywords:
Aspergillus nidulans
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Transgenic mutation assays generally use mutant frequencies to estimate mutation frequencies but the degree to which clonal expansion inflates mutant frequencies is largely unknown. Mutant frequency is defined as the fraction of cells carrying mutations in the gene of interest and, according to the standard Big Blue protocol, is determined by dividing the number of mutant plaques by the total number of plaques screened. Mutation frequency is determined as the fraction of cells carrying definitely independent mutations and therefore requires correction for clonal expansion. Mutant and mutation frequencies were determined for brain, thymus and male germ cells of four mice from two age groups (3-versus 10-month old). The mutant frequency in thymus differed significantly between 3- and 10-month old mice (P < 0.05). By sequencing all mutants, the mutation frequency (i.e., corrected for jackpot mutations) in thymus was determined and was not significantly different between 3- and 10-month old mice. Mutant frequency does not fit a Poisson distribution, but mutation frequency corrected for jackpot mutations is substantially less variable and does fit a Poisson distribution.
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Many waterbodies across the United States do not meet water quality standards. To help determine where and to what extent improvements should be sought, policymakers must consider the costs of regulations with their monetized values. We ...Scientific knowledge related to quantifying the monetized benefits for landscape-wide water quality improvements does not meet current regulatory and benefit–cost analysis needs in the United States. In this study we addressed this knowledge gap by ...
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Mutants of Bacillus subtilis which carried suppressor mutations for catabolite-resistance gene crsA47 were isolated from methylmethanesulfonate-treated cultures of GLU-47 (crsA47). The suppressor mutation, sca19, suppressed resistance of crsA47 mutant to glucose and other inhibitors of sporulation. Moreover, the suppressor mutation could restore the rate of growth and the level of IMP dehydrogenase and alkaline phosphatase of crsA47 mutant to the wild-type level. The sca19 mutation was also able to suppress catabolite resistance of other crs mutants. The map position of the sea19 mutation indicated that this mutation was an intergenic suppressor for the crs mutants. It was also found that an erythromycin-resistance mutation, ery1, could suppress the catabolite resistance of some of the crs mutants. Our results were discussed in relation to the importance of a proper state of metabolic activities and membrane functions during the initiation of sporulation.
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Aspergillus nidulans
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Abstract Nuclear migration plays an important role in the growth and development of many organisms including the filamentous fungus Aspergillus nidulans. We have cloned three genes from A. nidulans, nudA, nudC, and nudF, in which mutations affect nuclear migration. The nudA gene encodes the heavy chain of cytoplasmic dynein. The nudC gene encodes a 22-kD protein. The nudF gene was identified as an extra copy suppressor of the temperature sensitive (ts-) nudC3 mutation. The nudC3 mutation substantially decreases the intracellular concentration of the nudF protein at restrictive temperature. This is restored toward the normal level by an extra copy of nudF. To identify other genes whose products interact directly or indirectly with the NUDC protein, we have isolated a set of extragenic suppressors showed them to represent nine different genes, designated sncA-sncI (for suppressor of nudC). sncA-sncH were either dominant or semidominant in diploids homozygous for nudC3 and heterozygous for the snc mutations. All of the suppressors reversed the ts- phenotype of nudC3 by restoring the intracellular concentration of the NUDF protein.
Aspergillus nidulans
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Transgenic mutation assays generally use mutant frequencies to estimate mutation frequencies but the degree to which clonal expansion inflates mutant frequencies is largely unknown. Mutant frequency is defined as the fraction of cells carrying mutations in the gene of interest and, according to the standard Big Blue® protocol, is determined by dividing the number of mutant plaques by the total number of plaques screened. Mutation frequency is determined as the fraction of cells carrying definitely independent mutations and therefore requires correction for clonal expansion. Mutant and mutation frequencies were determined for brain, thymus and male germ cells of four mice from two age groups (3- versus 10-month old). The mutant frequency in thymus differed significantly between 3- and 10-month old mice (P < 0.05). By sequencing all mutants, the mutation frequency (i.e., corrected for jackpot mutations) in thymus was determined and was not significantly different between 3- and 10-month old mice. Mutant frequency does not fit a Poisson distribution, but mutation frequency corrected for jackpot mutations is substantially less variable and does fit a Poisson distribution. © 1996 Wiley-Liss, Inc.
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The ompR and envZ genes, which together constitute the ompB operon, are involved in osmoregulatory expression of the OmpF and OmpC proteins, major outer membrane proteins of Escherichia coli. The envZ11 mutation results in the OmpF- OmpC-constitutive phenotype. A mutant which suppressed defects caused by the envZ11 mutation was isolated. The suppressor mutation also suppressed the LamB- PhoA- phenotype caused by the envZ11 mutation. The mutation occurred in the ompR gene and hence was termed ompR77. The ompR77 mutation alone produced no obvious phenotype. Functioning of the ompR77 allele remained envZ gene dependent. Although the ompR77 mutation suppressed the envZ11 mutation, it did not suppress a mutation that occurred in another position within the envZ gene (envZ160). These results indicate that OmpR and EnvZ, two regulatory proteins, functionally interact with each other.
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