A complex glutathione transferase gene family in the housefly Musca domestica

Abstract

In most metazoans, the glutathione S-transferases (GST) are encoded by gene families, and are used to detoxify xenobiotics. We describe the structure of genomic loci coding for the GSTs in the housefly that have been implicated, by both genetic and biochemical means, in mediating insecticide resistance. In earlier work, we showed that one of the theta-class enzymes, MdGST-3, is overproduced in resistant flies and degrades certain insecticides. We used a fragment from a cDNA clone of MdGST-3 as a probe to screen a housefly genomic DNA bank in phage lambda. This probe detected multiple gst loci. Genes for GSTs were found in five different, nonoverlapping lambda clones, three of which carry multiple, closely linked gsts. Multiple genes for both MdGST-3 and MdGST-4 were found; some of which have introns in their 5' untranslated regions. In adults, the only MdGST-3 enzymes that are expressed are encoded by the intron-free genes. A new theta-class GST (called MdGST-5) was also discovered. Fusion genes comprising 5' MdGST-3 sequences and either MdGST-4 or MdGST-5 sequences in their 3' halves were encountered at three separate loci. The genes described here are found in both the ancestral sensitive strain and the insecticide-resistant strains.

Structural Analysis and Antibody Response to the Extracellular GlutathioneS-Transferases fromOnchocerca volvulus

“…4 for GP1 [44][45][46][47][48][49][50][51][52][53][54][55][56][57] and GP4 [144][145][146][147][148][149][150][151][152][153][154][155][156] . The assignment and the ratios of the glycan structures found at individual glycosylation sites of OvGST1a are as follows: for GP1 [44][45][46][47][48][49][50][51][52][53][54][55][56][57] and the relative ratios of oligosaccharides linked to glycosylation sites 1 (N50), 2 (N79), and 3 (N134) appear to be rather similar, at glycosylation site 4 (N144) clearly larger structures, bearing Man 5 GlcNAc 2 to Man 9 GlcNAc 2 , were detected. For further characterization of the (glyco)peptides, individual fractions from another HPLC run were collected and the amino acid sequences of all glycopeptides were confirmed by Edman sequencing.…”

“…For further characterization of the (glyco)peptides, individual fractions from another HPLC run were collected and the amino acid sequences of all glycopeptides were confirmed by Edman sequencing. Additionally, the MALDI-TOF MS spectrum shows the protonated molecular ions of tryptic GP1 [44][45][46][47][48][49][50][51][52][53][54][55][56][57] bearing two to five mannose residues (Fig. 4).…”

Insecticide Resistance and Vector Control

“…GST implicated in DDT insecticide resistance exist as clusters of genes that have been further shuffled through the genome by recombination (40). A number of resistance GST genes, including multiple forms in the same insect, have been characterized in vectors (41)(42)(43).…”

Molecular Evolution of Glutathione S-Transferases in the Genus Drosophila

“…Of particular interest to researchers are the d and e classes because they are insect specific, exist in some of the largest gene clusters in insect genomes, and, to date, are the only GSTs classes that have been implicated in insecticide resistance (Tang and Tu 1994;Ranson et al 2001;Ding et al 2003). The molecular complexity of dipteran GSTs may extend beyond the size of the gene clusters, as there is a suggestion that diversity may be generated within individuals by alternative splicing and within populations by gene fusions (Zhou and Syvanen 1997) and possibly by gene amplifications (Vontas et al 2002). A striking feature of the phylogenetic analyses is that, while there is a conservation of GST classes between D. melanogaster and An.…”