WHITE-IVORY ASSAY OF DROSOPHILA-MELANOGASTER UNDER DEFICIENT REPAIR CONDITIONS

The prediction ability of a test to detect genotoxic activity may be i ncreased, at least from a theoretical point of view, by carrying it ou t under deficient repair conditions. The white-ivory (w(i)) assay of D rosophila melanogaster is a somatic mutation and recombination test (S MART) that essentially differs from other SMARTS by the endpoints that can be detected. In this article, we study the consequences, with the w(i) essay, of the introduction of two mutations, mus201 and mei-41, which produce deficiency in two different repair mechanisms: the nucle otide excision repair system and in a G2/M cell-cycle checkpoint, resp ectively. Ten chemicals, previously classified as positive in the w(i) assay, have been assayed in both deficient repair conditions. As in t he w/w(+) and mwh/flr(3) SMARTS, the results obtained with the w(i) as say show that the use of deficient repair strains does not improve the detection of genotoxic effects. However, the utilization of these def icient repair strains has been shown to be a useful tool in mechanisti c studies. In fact, it seems that the nucleotide excision repair syste m mainly eliminates some spontaneous and chemically-induced damages in volved in the reversion of w(i), whereas the repair system deficient i n mei-41 flies is partly necessary to recover revertant w(i) spots. (C ) 1998 Wiley-Liss, Inc.