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Insertion du Transposon Tn4001 dans le génome de Spiroplasma citri : sélection d'un mutant non transmissible par la Cicadelle Circulifer Haematoceps et d'un mutant non phytopathogene : - contribution à l'étude de la spiraline protéine majeure de la membrane des spiroplasmes du groupe I

Abstract : Hundreds of plant diseases are caused by mollicutes, evolved bacteria without a cell-wall, such as phytoplasmas not available in culture, or Spiroplasma citri, S. kunkelii and S. phoeniceum, which are cultivated. In order to elucidate the mechanisms which govern the transmission by leafhopper of S. citri and its plant-pathogenicity, a mutant of S. citri not transmissible by the leafhopper vector Circulifer haematoceps and a mutant incapable of inducing symptoms in an indicator plant , are produced and selected. These mutants are obtained by random insertion of the transposon Tn4001 into the genome of S. citri strain GII3. They are selected by a transmission test to the Madagascar periwinkle Cathanranthus roseus, by C. haematoceps infected by intra-abdominal microinjection. The GMT470 mutant does not multiply in C. haematoceps and is therefore not transmitted to the plant. The GMT553 mutant normally multiplies in the vector insect. It is transmitted to the periwinkle C. roseus where it multiplies slowly. Periwinkles infected with this mutant lately reach a normal infection rate without showing the characteristic symptoms of infection with S. citri. Subsequently this mutant reverts in the plant, probably by precise excision of the transposon. In addition, Spiralin, a major lipoprotein of the S. citri membrane, is matured by acylation of an internal cysteine ​​and excision of a signal peptide by a type II signal peptidase, sensitive to globomycin, an inhibitor of this bacterial enzyme. The electrophoretic migration of Spiralin is different according to the strains of S. citri. This polymorphism can be explained neither by the classical maturation mechanism of bacterial lipoproteins, identical whatever the strain studied, nor by the molecular weights deduced from the genes which encode this protein in eight strains of S. citri. Finally, the sequence of the equivalent gene in S. kunkelii and S. melliferum shows that Spiralin has a repeated sequence specific to each species evocative of an adaptation of the spiroplasma to its vector insect.
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https://hal.inrae.fr/tel-02863648
Déposant : Xavier Foissac <>
Soumis le : mercredi 10 juin 2020 - 14:09:56
Dernière modification le : jeudi 11 juin 2020 - 09:57:29

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  • HAL Id : tel-02863648, version 1

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Xavier Foissac. Insertion du Transposon Tn4001 dans le génome de Spiroplasma citri : sélection d'un mutant non transmissible par la Cicadelle Circulifer Haematoceps et d'un mutant non phytopathogene : - contribution à l'étude de la spiraline protéine majeure de la membrane des spiroplasmes du groupe I. Sciences du Vivant [q-bio]. Université de Bordeaux II, 1995. Français. ⟨tel-02863648⟩

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