The in situ localization of Adh transcripts in Drosophila species reveals evolved regulatory differences in spatially restricted expression

Spatial and temporal aspects of Adh expression were examined during oogenesis and embryogenesis of Drosophila melanogaster, D. simulans, and D. virilis by in situ hybridization. In stage 14 and 15 embryos, differences in zygotic expression of Adh in the primordia of the gastric caecae of D. simulans and in the fat body of D. virilis were observed. These zygotic differences appear to be transient because Adh expression is seen in the gastric caecae of stage 16 embryos of D. simulans and in the fat body of stage 17 embryos of D. virilis. Analysis of D. melanogaster × D. simulans hybrids revealed that the parental difference for transcriptional activity of Adh in the primordia of the gastric caecae is under dominant control. These results provide the basis for exploring evolved regulatory differences in Adh expression during oogenesis and embryogenesis of Drosophila, which are until now unexplored. The potential of in situ hybridization in analyzing evolved regulatory differences in gene expression is briefly discussed.Key words: Drosophila, Adh, tissue-specific expression, interspecific variation, in situ hybridization.

Drosophila melanogaster alcohol dehydrogenase: product-inhibition studies

The Drosophila melanogaster alleloenzymes AdhS and AdhF have been studied with respect to product inhibition by using the two substrate couples propan-2-ol/acetone and ethanol/acetaldehyde together with the coenzyme couple NAD+/NADH. With both substrate couples the reaction was consistent with an ordered Bi Bi mechanism. The substrates added to the enzyme in a compulsory order, with coenzyme as the leading substrate, to give two interconverting ternary complexes. The second ternary complex broke down with release of products in an obligatory order, with the aldehyde/ketone leaving first. Both the acetaldehyde and acetone products formed binary complexes with the enzyme that affected NAD+ binding. However, only an enzyme-acetone complex seemed to affect NADH binding and hence the reverse reaction. The inhibitory pattern with acetaldehyde as product was also affected by the formation of a ternary enzyme-NAD(+)-acetaldehyde complex, which broke down to acetic acid and NADH. The product-inhibition pattern shown in the present work is different from that published for Drosophila Adh previously and this discrepancy can not be explained by the use of different variants of Drosophila Adh.