[Induction of transposition and excision of mobile genetic elements in Drosophila during isogenization]

Localization patterns of mobile genetic element (MGE) Dm412 were compared in chromosomes of ten isogenic lines and a heterogeneous control line riC of Drosophila. Isogenization was shown to induce MGE transpositions and excisions. Rates of induced transpositions and excisions were, respectively, 0.35 and 0.13 per site per haploid genome per isogenization, which is significantly (by two to three orders of magnitude) higher than corresponding rates in the control line. These values are also higher by an order of magnitude than previously obtained rates of transposition induction by means of heat shock treatment and gamma-irradiation of isogenic lines. In the average haploid genome of the original line, nc = 22.14 of the occupied Dm412 sites correspond to 11.9 transpositions and 4.6 excisions generated by isogenization. Calculated for the genomic system of copia-like MGE, these rates are approximately 105 and 39 events per approximately 300 initial MGE positions. Apparently, these rates exceed the "catastrophic limit of transpositions and excisions." A hypothesis on the role of inbreeding as genomic stress in induction of transpositions and excisions was proposed. Inbreeding is assumed to increase cell concentration of defective proteins, acting via the system of heat shock response-a general system of cell response to external and physiological stresses.