Correlation between the Number of Insertions, Transcript Levels and Transposition Rate of Retrotransposon copia in Drosophila melanogaster

The amounts of copia transcript in the testes of flies from five Drosophila melanogaster lines were compared by means of Northern blot hybridization. Four of these lines were closely related, differing only by transposition rates and the number of copia sites in the genome. The fifth line, which was not related to the others, was characterized by a lack of transpositions and the lowest copia copy number. Positive correlation between the total copia transcript level and its copy number and transposition rate was observed. Therefore, the transcription rate of copia retrotransposon in testes is largely controlled by the level of its transcription, which, in turn, is regulated by the number of retrotransposon copies in the genome. These data contradict the hypothesis on the self-regulation of the retrotransposon copy number in the genome.