TRANSPOSABLE ELEMENTS BEHAVIOR FOLLOWING VIRAL GENOMIC STRESS IN DROSOPHILA-MELANOGASTER INBRED LINE

To analyze the behavior of endogenous transposable elements under geno mic stress, a Drosophila melanogaster inbred line was submitted to thr ee kinds of viral perturbations. First, a retroviral plasmid containin g the avian Rous Associated Virus type 2 (RAV-2) previously deleted fo r the viral envelope coding gene (env) was introduced by P element tra nsformation into the Drosophila genome. An insertion of this avian ret roviral sequence was detected by in situ hybridization in site 53C on polytene chromosome arm 2R. Second, Drosophila embryos were injected w ith RAV-2 particles produced by cell culture after transfection with t he retroviral plasmid. Third, the Drosophila melanogaster inbred line was stably infected by the sigma native virus. It appears that neither the offspring of the flies in which the viral DNA was found integrate d nor those from the infected sigma flies showed copia or mdg1 element mobilization, Injection of the avian RAV-2 particles led, however, to the observation of somatic transpositions of mdg1 element on the 2L, chromosome, the copia element insertion pattern remaining stable. Thus , endogenous transposable elements show more instability in sublines i njected with exogenous viral particles than in a transgenic subline co ntaining a foreign viral insert, all transposable elements not being e qually sensitive to such genomic stress.