DEVELOPMENTAL TEMPERATURE AND SOMATIC EXCISION RATE OF MARINER TRANSPOSABLE ELEMENT IN 3 NATURAL-POPULATIONS OF DROSOPHILA-SIMULANS

The temperature effect on the somatic excision rate of an inactive copy (peach) of the mariner transposable element, inserted in the white gene and responsible of the mutation (w(pch)), was investigated in isofemale lines from 3 natural Populations of D simulans. The somatic excision rate of the peach element was measured by the proportion of mosaic males in the offspring of a test-cross between a wild type male (originating from natural populations) and white peach females of a reference strain (GB1). A significant effect of the breeding temperature was detected in 2 out of the 3 populations investigated, ie Loua (Congo) and Bordeaux (France). In these 2 populations, the proportion of mosaic males increased with temperature. In the third population (Agadir, Morocco), the proportion of mosaic males was always high whatever the temperature. A slight correlation between the excision rate and the number of mariner copies was observed. Finally, this temperature effect may be related to a 14-bp sequence localized in the 5' inverted repeat of the element showing 50-57% of homology with sequences of heat shock protein promoters.