24 research outputs found

    Gene for spiralin, the major membrane protein of the helical mollicute Spiroplasma citri: cloning and expression in Escherichia coli.

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    A library of cloned Spiroplasma citri genomic sequences was constructed by incorporating HindIII digestion fragments into the plasmid vector pBR328. Immunological screening allowed the identification of a recombinant plasmid containing the gene for spiralin, the major membrane protein of S. citri. The spiralin produced by the Escherichia coli transformant was characterized by immunological detection with monoclonal antibody after Western blotting of two-dimensional (isoelectric focusing and sodium dodecyl sulfate-polyacrylamide) electrophoresis gels and by partial proteolytic mapping. The gene for spiralin occurred within a 6.5-kilobase-pair cloned DNA fragment. Spiralin in E. coli was produced regardless of the orientation of the insert within the pBR328 vector. A spiroplasmal DNA sequence which acted as a promoter in E. coli was cloned along with the structural spiralin gene which is expressed in E. coli from that sequence

    Worldwide migration of amplified insecticide resistance genes in mosquitos

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    International audienceIn Culex pipiens, overproduction of nonspecific esterases is a common mechanism of resistance to organophosphate insecticides 1,2. The esterases are attributed to closely linked loci named A and B according to substrate preference 3-6, and overproduction of all esterases B is due to gene amplification 7,8. Distribution of electrophoretically distinct variants of overproduced esterases A and B is geographically restricted, with the exception of esterases A2 and B2, always found together throughout at least three continents (Fig. 1). To determine whether this situation is due to migration or to a high mutation rate, esterase B structural genes and their flanking regions were compared by sequence and/or restriction fragment length polymorphism analysis. Whereas structural genes were similar, flanking regions of electrophoretically dissimilar esterases B varied considerably. In contrast, flanking sequences of esterases B2 from different geographical locations (Africa, Asia, North America) were identical. These results suggest that amplified esterase B2 genes originated from an initial event that has subsequently spread organophosphate insecticide resistance by migration
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