Variation in alcohol dehydrogenase activity in vitro in flies from natural populations ofDrosophila melanogaster

ADH enzyme activity and Adh gene expression in Drosophila melanogaster lines differentially selected for increased alcohol tolerance

In Drosophila melanogaster, alcohol dehydrogenase (ADH) activity is essential for ethanol tolerance, but its role may not be restricted to alcohol metabolism alone. Here we describe ADH activity and Adh expression level upon selection for increased alcohol tolerance in different life-stages of D. melanogaster lines with two distinct Adh genotypes: Adh(FF) and Adh(SS). We demonstrate a positive within genotype response for increased alcohol tolerance. Life-stage dependent selection was observed in larvae only. A slight constitutive increase in adult ADH activity for all selection regimes and genotypes was observed, that was not paralleled by Adh expression. Larval Adh expression showed a constitutive increase, that was not reflected in ADH activity. Upon exposure to environmental ethanol, sex, selection regime life stage and genotype appear to have differential effects. Increased ADH activity accompanies increased ethanol tolerance in D. melanogaster but this increase is not paralleled by expression of the Adh gene.

Strains of Drosophila melanogaster differ in alcohol tolerance

The influence of environmental ethanol on different fitness components and the larval activities of some enzymes were studied in three strains of Drosophila melanogaster. All three strains carried the AdhS-alphaGpdhF allele combination on their second chromosomes while they had unique allele combinations at the Odh and Aldox loci on their third chromosomes (strain 1: OdhS-AldoxF; strain 2: OdhF-AldoxS; strain 3: OdhS-AldoxS). Normal lines and exposure lines, kept on 5% ethanol supplemented medium for at least 20 generations, were established from each strain and the responses of the two lines to different ethanol concentrations were compared. Two survival components were estimated in the juvenile life history stages. In addition, the weights of the emerging adult males were measured at various concentrations of ethanol. The changes in the activities of two enzymes (ADH and alpha GPDH) were also surveyed in the larvae after the different ethanol treatments. Strain-specific differences were observed in the responses of all investigated traits to ethanol. OdhS-AldoxF larvae seemed to be more tolerant to ethanol than the larvae of the other two strains while the utilisation of ethanol as energy source appeared to be the least effective in this strain. Larvae of the exposure lines had significantly higher tolerance to ethanol, and the adult males were heavier, than the ones from the normal lines. The enzymatic responses of the two lines to the ethanol treatments were also different. ADH activity, fresh male weight, and pupa-to-adult survival seemed only to be associated under short-term exposure to ethanol. Ethanol tolerance appeared to be independent of the utilisation of ethanol in the larva-to-pupa stage.

The alcohol dehydrogenase polymorphism in natural populations of Drosophila melanogaster: ADH activity variation restriction site polymorphism and the Adh cline

Alcohol dehydrogenase activity has been measured in 186 iso-second chromosome lines--104 from seven Australian populations and 82 from six Chinese populations. Restriction endonuclease variation in the Adh gene region in these lines has previously been described (Jiang & Gibson, 1991). The mean ADH activity of AdhF and AdhS lines was significantly higher in the Chinese samples than in the Australian samples. In each population on both continents the mean activity of the AdhF lines is significantly higher than that of the AdhS lines. Six lines homozygous for a thermostability variant, AdhFChD (detected in four of the Chinese populations), had intermediate levels of ADH activity and protein amount. In a subset of the lines with the highest and lowest levels of ADH, there was a correlation of 0.69 between ADH activity and ADH CRM. None of the restriction site variants was consistently associated with the amount of ADH activity. Associations between BamHI (-7.2), the Adh polymorphism and ADH activity suggest that there are modifiers of ADH 5' to the gene. The deletion (0.2) at position -2.8 on the restriction map (Jiang & Gibson, 1991) was associated with increased levels of ADH activity in AdhS lines from China. Two unique insertions in the gene region were associated with low activity in AdhF lines and a null activity allele had a deletion removing most of exon 2. A single line with a duplication of a part of the Adh coding region and of the 5' regulatory section had relatively high ADH activity. Considering all the data, the main factor affecting ADH activity levels in populations is the frequency of AdhF.

The alcohol dehydrogenase polymorphism in natural populations of Drosophila melanogaster: restriction map variation in the region of the Adh locus in populations from two hemispheres

Restriction endonuclease variation in the 12 kb region surrounding the Adh locus was measured in seven Australian and six Chinese populations of Drosophila melanogaster. There is a higher level of nucleotide-substitution variation in the Australian populations than in the Chinese, which is possibly a reflection of their origins. None of the restriction site polymorphisms, nor any of the insertions, showed a significant association with latitude. A 0.2 kb deletion varied with latitude in the Chinese populations. In accordance with previous studies, a majority of the insertions were located in a region 1.5-3.5 kb 3' from the Adh coding region, and a majority of the deletions were at a site 3 kb 5' to the Adh coding region. Two of the insertions shared homologies with known mobile elements. Overall, the data suggest that restriction endonuclease variation in the Adh region is not related to the cline in Adhs frequencies.

Nonlatitudinal environmental correlations for alcohol dehydrogenase in southern African populations of Drosophila melanogaster

The relation between alcohol dehydrogenase (ADH) allozyme frequencies and several environmental variables, as well as latitude and longitude, was examined in 17 natural populations of Drosophila melanogaster in Namibia, South Africa, and Zimbabwe. Unlike several other studies, we found no latitudinal allele-frequency clines and no significant correlation with temperature. We found that the frequency of the most common allele (AdhS) was positively correlated with an increase in rainfall. We suggest that substrate-induced toxicity may explain the geographic variability in our results.

The alcohol dehydrogenase polymorphism of Drosophila melanogaster in relation to environmental ethanol, ethanol tolerance and alcohol dehydrogenase activity

Ethanol levels in Drosophila breeding sites were higher in a winery storing fortified wines than in nearby grape pressings or in orchard fruits. The relative abundance of D. simulans to D. melanogaster was negatively correlated with ethanol levels. In D. melanogaster there were no significant differences in AdhF frequency between the orchard and winery populations. The ethanol tolerance of wild caught D. melanogaster males paralleled the levels of ethanol in the breeding sites but Adh alleles and ethanol tolerance segregated largely independently of each other. Levels of ADH activity were positively associated with the ethanol tolerance of the different populations and with levels of ethanol in the breeding sites, but it is argued that the ethanol levels are not causative. Flies from inside the winery had higher ADH levels due mainly to greater amounts of ADH-F. The difference in activity persisted for at least one generation in the laboratory. After ten generations of laboratory culture the differences in ethanol tolerance were still present but there were no significant differences in ADH activity.

Restriction endonucleases variation in the region of the alcohol dehydrogenase gene: a comparison of null and normal alleles from natural populations of Drosophila melanogaster

The restriction endonuclease variation in the 12 kb region surrounding twelve Adh null alleles extracted from three Tasmanian populations has been compared with normal alleles from the same populations. Each of the null alleles had the same haplotype as revealed by digestions with eight hexanucleotide restriction enzymes. This haplotype also occurred in 4 of the 46 chromosomes bearing normal alleles which were tested; these four chromosomes with the null allele haplotype carried the AdhS allele. The data suggest that the Adh null alleles from geographically separate populations share a common ancestry and are derived from the same mutation in an AdhS allele.