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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 245 (1994), S. 25-31 
    ISSN: 1617-4623
    Keywords: Glutathione transferase ; Musca domestica ; Insecticide resistance ; Multigene family ; Evolutionary rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three new glutathione transferase (GST) genes from the housefly Musca domestica are described. These genes, identified as MdGST-2, -3, and -4, were from cDNA clones obtained from a cDNA bank in phage λ. The bank was prepared using poly(A)+ RNA from a housefly that is highly resistant to organophosphate insecticides because of enhanced expression of multiple members of the glutathione transferase gene family. The DNA sequence of each is reported and has a complete open reading frame that specified an amino acid sequence similar to other dipteran glutathione transferases. Based on phylogenetic analysis, we can conclude that the insect glutathione transferase gene family falls into two groups, each of which evolves at a different rate, presumably due to differences in functional constraints. We show that MdGST-1 (and their homologues from Drosophila and Lucilia) evolve at a significantly slower rate than the other members of the gene family. Each housefly GST cDNA was inserted into a bacterial plasmid expression system and a glutathione transferase activity was expressed in Escherichia coli. The transcription pattern of each of these glutathione transferases was examined in a variety of different housefly strains that are known to differ in their resistance to organophosphate insecticides due to different patterns of glutathione transferase expression. We found that the level of transcription for two of our clones was positively correlated with the level of organophosphate resistance.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Glutathione S-transferase ; Musca domestica ; cDNA sequence ; Organophosphate triesters ; Insecticide resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report the cloning and sequencing of a glutathione S-transferase (GST) gene from the housefly Musca domestica. A cDNA λgt11 library was prepared from the organophosphate insecticide-resistant housefly strain Cornell-R — a variant that has elevated GST activity. The λ phage GST clone was identified on the basis of its ability to cross-hybridize to a GST DNA probe from Drosophila melanogaster. Based on amino acid homology to other GSTs and expression of GST activity in Escherichia coli, the Musca GST gene (MdGST-1) belongs to the GST gene family. Although organophosphate resistance in Cornell-R is largely due to one of the GSTs, MdGST-1 is probably not the enzyme responsible for resistance. The mutation that controls resistance to organophosphate insecticides in Cornell-R is highly unstable and we isolated spontaneous variants to both insecticide sensitivity and to even higher levels of resistance. This provided us with an isogenic set of three strains. We found that MdGST-1 transcript levels as measured by Northern assays are higher in all three Cornell-R strains relative to the sensitive wild type, but that the sensitive Cornell-R strain has more MdGST-1 transcript than does the highly resistant Cornell-R strain. These data as well as Southern analysis of genomic DNA allow us to conclude: (1) there are multiple GST genes in M. domestica; (2) the natural variant Cornell-R excess transcript from two and probably more of these genes; and (3) the unstable mutation in Cornell-R influences the levels of multiple GSTs.
    Type of Medium: Electronic Resource
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