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Propagation d’un Virus Sigma Défectif au Niveau de Disques Imaginaux d’Aile Implantés dans des Drosophiles Adultes
Abstract
SOMMAIRE
Le virus héréditaire de la Drosophile, Sigma, peut être propagé au niveau de disques imaginaux d’aile implantés dans la cavité abdominale de mouches adultes. Cette propagation peut avoir lieu à travers les divisions cellulaires même lorsque le variant utilisé est défectif pour les fonctions de maturation (variant u-ρ).
L’étude des modalités de la transmission de cellule mère à cellules filles nous conduit à penser qu’il s’établit un équilibre stable sans que les génomes viraux soient intégrés au génome de la cellule hôte. Cet état porteur serait du type ‘Regulated infection of cells’.
SUMMARY
A variant of σ virus defective for maturation functions was studied. Stabilized flies for this virus were called ultra-ρ flies. They were not CO2-sensitive and extracts were not infectious. The presence of the virus was detected because it conferred to imagos a characteristic immunity against a superinfecting σ virus: these flies were not immunized against a superinfecting virus of the same group, such as vesicular stomatitis virus.
Wing discs were taken from larvae of two ultra-ρ strains (u-ρ46 and u-ρ751) and were exposed to superinfection by implantation into hosts infected with a non-defective σ virus. The blastemas were then implanted into a detector host able to support virus multiplication until the symptom appeared showing superinfection. Control experiments were made with originally virus-free discs. We have thus shown that the characteristic ultra-ρ immunity is present in the imaginal wing disc of ultra-ρ larvae. It is concluded that embryonic blastema cells contain ultra-ρ virus genomes.
In tests on the persistence of immunity through successive transfer generations the results differed with the ultra-ρ strain used. The detector hosts implanted with u-ρ46 blastemas were classified as early CO2-sensitive and CO2-resistant; the number of CO2-resistant hosts did not decrease and the u-ρ46 immunity was therefore stable. On the other hand, the detector hosts implanted with u-ρ751 blastemas were of three classes: early CO2-resistant and late sensitive hosts decreased as a function of time indicating that u-ρ751 immunity was unstable. This instability suggests that blastemas giving late sensitivity are mosaics of ultra-ρ cells and virus-free cells.
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© Journal of General Virology 1970