Differential regulation of P and hobo mobile elements by two laboratory strains of Drosophila melanogaster.

Analysis of the transposition behaviour of the P and hobo elements borne by the 31.1/CyL4 MRF (P), 23.5 delta/CyL4 MRF (hobo) and 23.5*/Cy MRF (hobo) strains in the progeny of dysgenic crosses with two ME laboratory strains (Berlin-k and dp b cn bw) at 25 degrees C revealed that: (a) the two ME laboratory strains affect differently the transposition rates of P and hobo elements. More precisely, P element transposition is higher in heterozygotes with dp b cn bw than in those with Berlin-k. In contrast, the transposition rate of hobo elements is higher in Berlin-k than in dp b cn bw heterozygotes. (b) Like P, hobo has the potential to transpose at high frequencies and to nonhomologous chromosomes. (c) The dysgenically inactive hobo elements of the 31.1 MRF strain transpose more frequently than the dysgenically active hobo elements of the 23.5 MRF strains in certain crosses. (d) There are insertion hot spots for P and hobo elements. For the P elements there are enough data to suggest that the insertion hot spots are different in the two EM strains. The data are discussed on the basis of the involvement of putative host factors in transposition regulation of the P and hobo elements.