Induction of notch-like phenocopies by methoxyacetate dependent on alcohol dehydrogenase allozymes of Drosophila melanogaster

Abstract

1. 1. Third instar larvae of two wild type strains of Drosophila melanogaster, homozygous for Adh 71 k and Adh F respectively were exposed to methoxyacetate, an inhibitor of sarcosine dehydrogenase. The two strains showed a different Notch-like phenocopy frequency. This is explained as a consequence of the different oxidation rates of sarcosine by the two alcohol dehydrogenase allozymes, ADH 71k and ADH F. 2. 2. Inhibition of ADH activity in vivo by acetone, before the administration of methoxyacetate, enhanced in both strains differentially the frequency of wing-notches and mortality. Then the phenocopy frequency in the Adh 71 k strain almost equalled that of the Adh F -strain. 3. 3. The activity of sarcosine dehydrogenase is controlled by the Notch locus. Activity of sarcosine dehydrogenase is lowered by Notch mutations and methoxyacetate, whereas at the same time they do not affect the activity of alcohol dehydrogenase. 4. 4. Therefore we suppose that ADH 71k forms a bypass for sarcosine oxidation, when in vivo sarcosine dehydrogenase activity is reduced either by artificial in vivo inhibition or by a mutation. 5. 5. This explains also the fixation of the Adh 71 k allele in stocks with Notch mutants of Drosophila melanogaster.