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 cop y (peach) of the mariner transposable element, inserted in the white g ene and responsible of the mutation (w(pch)), was investigated in isof emale lines from 3 natural Populations of D simulans. The somatic exci sion rate of the peach element was measured by the proportion of mosai c males in the offspring of a test-cross between a wild type male (ori ginating from natural populations) and white peach females of a refere nce 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 mosai c males increased with temperature. In the third population (Agadir, M orocco), the proportion of mosaic males was always high whatever the t emperature. A slight correlation between the excision rate and the num ber of mariner copies was observed. Finally, this temperature effect m ay 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.