Analysis of Aldoxn alleles isolated from natural populations of Drosophila melanogaster.

Aldox "null" alleles which were isolated from natural populations in Great Britain and North Carolina were analyzed for complementation. No complementation was observed between any combinations of "null" alleles for aldehyde oxidase (AO) specific activity in late third-instar larvae and newly emerged adults. AO immunologically cross-reacting material (AO-CRM) was quantitated in all homozygous stocks at both developmental stages as well as all allelic combinations in newly emerged adults. When the adult organism contains only Aldoxn alleles, the polypeptides are not immunologically recognizable or may be rapidly degraded. Larvae and adults have different abilities to degrade mutationally altered enzymatically inactive AO polypeptide or synthesize them differentially. This is indicated by easily measurable AO-CRM levels in late third-instar larvae of Aldoxn homozygotes, while newly emerged adult Aldoxn homozygotes have very little, if any, AO-CRM. Newly emerged adult heterozygotes of Aldoxn/Aldox+ do have increased AO-CRM, indicating that the Aldoxn alleles can code for a polypeptide which can be "rescued" if Aldox+ gene product is present. Heterozygotes containing an Aldox+ allele with a deficiency for the Aldox region produce 74.2% of the AO-CRM found in Aldox+ homozygotes. This may indicate the presence of trans-acting factors which serve to activate gene expression in a system in which each gene copy is not maximally expressed.