Biochemical differences between products of the Adh locus in Drosophila

Different genetic basis for alcohol dehydrogenase activity and plasticity in a novel alcohol environment for Drosophila melanogaster

Phenotypic plasticity is known to enhance population persistence, facilitate adaptive evolution and initiate novel phenotypes in novel environments. How plasticity can contribute or hinder adaptation to different environments hinges on its genetic architecture. Even though plasticity in many traits is genetically controlled, whether and how plasticity's genetic architecture might change in novel environments is still unclear. Because much of gene expression can be environmentally influenced, each environment may trigger different sets of genes that influence a trait. Using a quantitative trait loci (QTL) approach, we investigated the genetic basis of plasticity in a classic functional trait, alcohol dehydrogenase (ADH) activity in D. melanogaster, across both historical and novel alcohol environments. Previous research in D. melanogaster has also demonstrated that ADH activity is plastic in response to alcohol concentration in substrates used by both adult flies and larvae. We found that across all environments tested, ADH activity was largely influenced by a single QTL encompassing the Adh-coding gene and its known regulatory locus, delta-1. After controlling for the allelic variation of the Adh and delta-1 loci, we found additional but different minor QTLs in the 0 and 14% alcohol environments. In contrast, we discovered no major QTL for plasticity itself, including the Adh locus, regardless of the environmental gradients. This suggests that plasticity in ADH activity is likely influenced by many loci with small effects, and that the Adh locus is not environmentally sensitive to dietary alcohol.

Selection on structural allelic variation biases plasticity estimates

Wang and Althoff (2019) explored the capacity of Drosophila melanogaster to exhibit adaptive plasticity in a novel environment. In a full-sib, half-sib design, they scored the activity of the enzyme alcohol dehydrogenase (ADH) and plastic responses, measured as changes in ADH activity across ethanol concentrations in the range of 0-10% (natural variation) and 16% (the novel environment). ADH activity increased with alcohol concentration, and there was a positive association between larval viability and ADH activity in the novel environment. They also reported that families exhibiting greater plasticity had higher larval survival in the novel environment, concluding that ADH plasticity is adaptive. However, the four authors now concur that, since the study estimated plasticity from phenotypic differences across environments using full-sib families, it is not possible to disentangle the contributions of allele frequency changes at the Adh locus from regulatory control at loci known to influence ADH activity. Selective changes in allele frequencies may thus conflate estimates of plasticity; any type of "plasticity" (adaptive, neutral, or maladaptive) could be inferred depending on allele frequencies. The problem of scoring sib-groups after selection should be considered in any plasticity study that cannot use replicated genotypes. Researchers should monitor changes in allele frequencies as one mechanism to deal with this issue.

ALCOHOL TOLERANCE, ADH ACTIVITY, AND ECOLOGICAL NICHE OF DROSOPHILA SPECIES

In vitro alcohol dehydrogenase (ADH) activity was measured in adults of species belonging to Drosophila and to the related genus Zaprionus. Data were analyzed according to the known breeding sites and the level of ethanol tolerance of these species. Alcohol dehydrogenase activity was assayed with both ethanol (E) and isopropanol (I). Our results show a very broad range of activities among the 71 species investigated, the ratio of the highest value observed (D. melanogaster) to the lowest (D. pruinosa) being 65:1. A general positive correlation was found between the level of ADH activity and the capacity to detoxify ethanol. Nevertheless, many species show exceptions to this rule. Contrary to a logical expectation, adaptation to high alcoholic resources, which has been a recurrent evolutionary event, was not mediated by a more efficient use of ethanol, that is, an increase of the E/I ratio. This ratio seems to be quite variable according to the phylogeny and is especially low in the subgenus Sophophora as well as in Zaprionus. Alcohol tolerance clearly is related to the larval habitat of the species and shows that adaptation to alcoholic resources has been a major evolutionary challenge in drosophilids. This adaptation is not related to phylogeny, having occurred independently several times during the evolution of the group. Finally, it should be borne in mind that, besides metabolization and detoxification, other physiological processes such as nervous‐system tolerance or ethanol excretion may be involved in ethanol tolerance, and such functions also should be investigated. Environmental ethanol, which is certainly a major ecological parameter for many drosophilids, has selected a diversity of physiological adaptations, all related to the Adh locus, but presumably much more complicated than was previously believed.

Genetics and genomics of alcohol sensitivity

Alcohol abuse and alcoholism incur a heavy socioeconomic cost in many countries. Both genetic and environmental factors contribute to variation in the inebriating effects of alcohol and alcohol addiction among individuals within and across populations. From a genetics perspective, alcohol sensitivity is a quantitative trait determined by the cumulative effects of multiple segregating genes and their interactions with the environment. This review summarizes insights from model organisms as well as human populations that represent our current understanding of the genetic and genomic underpinnings that govern alcohol metabolism and the sedative and addictive effects of alcohol on the nervous system.

Gene expression variation and expression quantitative trait mapping of human chromosome 21 genes

Inter-individual differences in gene expression are likely to account for an important fraction of phenotypic differences, including susceptibility to common disorders. Recent studies have shown extensive variation in gene expression levels in humans and other organisms, and that a fraction of this variation is under genetic control. We investigated the patterns of gene expression variation in a 25 Mb region of human chromosome 21, which has been associated with many Down syndrome (DS) phenotypes. Taqman real-time PCR was used to measure expression variation of 41 genes in lymphoblastoid cells of 40 unrelated individuals. For 25 genes found to be differentially expressed, additional analysis was performed in 10 CEPH families to determine heritabilities and map loci harboring regulatory variation. Seventy-six percent of the differentially expressed genes had significant heritabilities, and genomewide linkage analysis led to the identification of significant eQTLs for nine genes. Most eQTLs were in trans, with the best result (P=7.46 x 10(-8)) obtained for TMEM1 on chromosome 12q24.33. A cis-eQTL identified for CCT8 was validated by performing an association study in 60 individuals from the HapMap project. SNP rs965951 located within CCT8 was found to be significantly associated with its expression levels (P=2.5 x 10(-5)) confirming cis-regulatory variation. The results of our study provide a representative view of expression variation of chromosome 21 genes, identify loci involved in their regulation and suggest that genes, for which expression differences are significantly larger than 1.5-fold in control samples, are unlikely to be involved in DS-phenotypes present in all affected individuals.

Drosophila melanogaster, a genetic model system for alcohol research

In its natural environment, which consists of fermenting plant materials, the fruit fly Drosophila melanogaster encounters high levels of ethanol. Flies are well equipped to deal with the toxic effects of ethanol; they use it as an energy source and for lipid biosynthesis. The primary ethanol-metabolizing pathway in flies involves the enzymes alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH); their role in adaptation to ethanol-rich environments has been studied extensively. The similarity between Drosophila and mammals is not restricted to the manner in which they metabolize ethanol; behaviors elicited by ethanol exposure are also remarkably similar in these organisms. Flies show signs of acute intoxication, which range from locomotor stimulation at low doses to complete sedation at higher doses, they develop tolerance upon intermittent ethanol exposure, and they appear to like ethanol, showing preference for ethanol-containing media. Molecular genetic analysis of ethanol-induced behaviors in Drosophila, while still in its early stages, has already revealed some surprising parallels with mammals. The availability of powerful tools for genetic manipulation in Drosophila, together with the high degree of conservation at the genomic level, make Drosophila a promising model organism to study the mechanism by which ethanol regulates behavior and the mechanisms underlying the organism's adaptation to long-term ethanol exposure.

Micro-evolution in a wine cellar population: an historical perspective

The population of Drosophila melanogaster inside the wine cellar of Chateau Tahbilk of Victoria, Australia was found by McKenzie and Parsons (1974) to have undergone microevolution for greater alcohol tolerance when compared to the neighboring population outside the cellar. This triggered additional studies at Tahbilk, and at other wine cellars throughout the world. The contributions and interactions of researchers and the development of ideas on the ecology and genetics of this unique experimental system are traced. Although the ADH-F/ADH-S polymorphism was found to be maintained by selection in the Tahbilk populations, the selection is not significantly associated with alcohol tolerance. The environment inside the Tahbilk wine cellar is not as rich in ethanol as was originally anticipated, and selection that affects the alcohol dehydrogenase polymorphism may be more concerned with the relative efficiency with which ethanol is used as a nutrient by D. melanogaster. The synthesis and modification of lipids, particularly in membranes, appears to be important to alcohol tolerance. The studies of the Tahbilk population are at a crossroad. New experimental approaches promise to provide the keys to the selection that maintains the alcohol dehydrogenase polymorphism, and to factors that are important to alcohol tolerance and stress adaptation. From these research foundations at Tahbilk very significant contributions to our future understanding of the genetic processes of evolution can be made.

Evolutionary genetics of the Drosophila alcohol dehydrogenase gene-enzyme system

Evolutionary genetics embodies a broad research area that ranges from the DNA level to studies of genetic aspects in populations. In all cases the purpose is to determine the impact of genetic variation on evolutionary change. The broad range of evolutionary genetics requires the involvement of a diverse group of researchers: molecular biologists, (population) geneticists, biochemists, physiologists, ecologists, ethologists and theorists, each of which has its own insights and interests. For example, biochemists are often not concerned with the physiological function of a protein (with respect to pH, substrates, temperature, etc.), while ecologists, in turn, are often not interested in the biochemical-physiological aspects underlying the traits they study. This review deals with several evolutionary aspects of the Drosophila alcohol dehydrogenase gene-enzyme system, and includes my own personal viewpoints. I have tried to condense and integrate the current knowledge in this field as it has developed since the comprehensive review by van Delden (1982). Details on specific issues may be gained from Sofer and Martin (1987), Sullivan, Atkinson and Starmer (1990); Chambers (1988, 1991); Geer, Miller and Heinstra (1991); and Winberg and McKinley-McKee (1992).

Adaptive significance of amylase polymorphism in Drosophila--VI. Properties of two amylase variants and the effect of food components on amylase activity in Drosophila subobscura

1. Properties of amylase from two D. subobscura strains homozygous for two different amylase variants (AmyS and AmyF) were determined. 2. Amylase of both strain adults showed a pH optimum of 7.8. 3. The AmyF enzyme showed a higher thermostability. 4. They differed in both maximum activity and Michaelis constant (Vmax of 6.25 and 3.45, Km of 0.7% and 0.42% starch for AmyS and AmyF, respectively). 5. The effect of different feeding conditions in amylase activity in the above Drosophila strains was also studied. Amylase activity was always detected but to a different level depending on diet composition.

The involvement of alcohol dehydrogenase and aldehyde dehydrogenase in alcohol/aldehyde metabolism in Drosophila melanogaster

In this study we have examined the roles of alcohol dehydrogenase, aldehyde oxidase, and aldehyde dehydrogenase in the adaptation of Drosophila melanogaster to alcohol environments. Fifteen strains were characterized for genetic variation at the above loci by protein electrophoresis. Levels of in vitro enzyme activity were also determined. The strains examined showed considerable variation in enzyme activity for all three gene-enzyme systems. Each enzyme was also characterized for coenzyme requirements, effect of inhibitors, subcellular location, and tissue specific expression. A subset of the strains was chosen to assess the physiological role of each gene-enzyme system in alcohol and aldehyde metabolism. These strains were characterized for both the ability to utilize alcohols and aldehydes as carbon sources as well as the capacity to detoxify such substrates. The results of the above analyses demonstrate the importance of both alcohol dehydrogenase and aldehyde dehydrogenase in the in vivo metabolism of alcohols and aldehydes.

Comparison of in vitro and in vivo activities associated with the G6PD allozyme polymorphism in Drosophila melanogaster

Earlier studies of the A and B allozymes at the G6pd locus show a differential ability of the genotypes to suppress the loss of viability associated with a low activity 6-phosphogluconate dehydrogenase mutation, 6Pgdlo1. This observation indicates a relatively lower activity for the A allozyme genotype, but it is not known if this level of suppression required a large difference in in vivo activity. To clarify this difference an analysis of the biochemical properties of the purified allozymes was carried out, as well as an analysis of the activity level associated with an original low activity P element-derived allele which had partially reverted and lost its suppression ability. G6PD activity and protein level were studied in 47 X chromosome lines from North America. The A genotype averages a 9% lower Vmax. From analysis of the correlation between G6PD activity and protein level it remains unclear whether the allozyme Vmax difference results from dissimilarity in protein level or kcat. At 25 degrees and physiological pH, comparative studies of the steady-state kinetics show the two purified allozyme variants differ significantly in their KM values for glucose-6-phosphate and NADP, and the K1 for NADPH. In aggregate these parameters predict the A genotype possesses a 20% lower in vitro catalytic efficiency. A partial revertant of a P element-derived low activity B variant, was shown to lose the ability to suppress 6Pgdlo1 low viability after acquiring only 60% of normal B activity. This last comparison shows the A genotype activity must be reduced in vivo by at least 40%.

Insertion of a copia element 5' to the Drosophila melanogaster alcohol dehydrogenase gene (adh) is associated with altered developmental and tissue-specific patterns of expression

The Drosophila melanogaster alcohol dehydrogenase gene (adh) is under the control of two separate promoters (proximal and distal) which are preferentially utilized at the larval and adult life stages, respectively. A variant alcohol dehydrogenase allele (RI-42) isolated from a natural population contains a copia retroviral-like transposable element inserted 240 bp upstream from the distal (adult) adh transcriptional start site. Levels of adh transcripts in the RI-42 variant are reduced in tissues and at life stages where copia is actively expressed and are affected in trans- by mutant alleles at the suppressor-of-white-apricot (su(wa] and suppressor-of-forked (su(f] loci. These suppressor genes have no effect on adh expression in wild-type Drosophila.

ADH activity and ethanol tolerance in third chromosome substitution lines in Drosophila melanogaster

In vitro ADH activity and ethanol tolerance were studied in males of a series of third chromosome substitution lines in Drosophila melanogaster. The lines were divided into those with a random third chromosome from a vineyard population (VO lines) and those with a selected third chromosome from males obtained after an egg-to-adult ethanol survival test on the F4 of the previous population (VE lines). Both ADH activity and ethanol tolerance varied significantly among the lines, but the characters showed no significant correlation. Ethanol tolerance (at the higher ethanol concentrations) was higher in the selected lines (VE lines) but ADH activity was not. In our lines, the in vitro ADH activity variability, linked to the regulatory genes (located on the third chromosome) and unrelated to the polymorphism of the Adh locus (located on the second chromosome), is not involved in the ethanol tolerance variability. The data suggest that in this population ethanol tolerance was acquired in nature, at least partially, by means other than increasing ADH activity.

Quantitative analysis of RNA produced by slow and fast alleles of Adh in Drosophila melanogaster

The alcohol dehydrogenase (ADH) locus (Adh) of Drosophila melanogaster in polymorphic on a world-wide basis for two allozymes, Fast and Slow. This study was undertaken to determine whether the well-established difference in ADH protein concentration between the allozymes is due to a difference in mRNA levels. RNA gel blot hybridization and an RNase protection assay were used to quantify ADH mRNA levels. Each method used an Adh null mutant as an internal standard. Several Slow and Fast allele pairs of different geographic origins were analyzed. The results provide strong evidence that the ADH protein concentration difference is not accounted for by RNA level.

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.

Recent origin for a thermostable alcohol dehydrogenase allele of Drosophila melanogaster

The nucleotide sequence of the Fast-Chateau Douglas isolate of the thermostable alcohol dehydrogenase allele is compared with the sequences of the Slow and Fast alleles of Drosophila melanogaster. Conceptual translation of the FChD sequence indicates that the thermostable polypeptide has the diagnostic FAST amino acid replacement at residue 192 and an additional replacement of serine for proline at residue 214. This suggests a Fast origin for the thermostable Adh allele. However, some of the biochemical properties of the FCHD protein resemble those of the SLOW rather than the FAST polypeptides. The serine for proline replacement confers upon the thermostable polypeptide substrate specificities and some kinetic parameters similar to the SLOW protein. The same replacement substitution within the third coding exon also appears to alter the ADH protein concentration to a level similar to the SLOW polypeptide and the probable effect is at the level of mRNA concentration. The low level of nucleotide sequence variation, other than that leading to the amino acid substitution, suggests a recent origin for the thermostable allele. The time since divergence of the FChD sequence from Fast is estimated to be approximately 260,000-470,000 years.

Physiological significance of the alcohol dehydrogenase polymorphism in larvae of Drosophila

This study deals with biochemical and metabolic-physiological aspects of the relationship between variation in in vivo alcohol dehydrogenase activity and fitness in larvae homozygous for the alleles Adh71k, AdhF, AdhS, of Drosophila melanogaster, and for the common Adh allele of Drosophila simulans. The Adh genotypes differ in the maximum oxidation rates of propan-2-ol into acetone in vivo. There are smaller differences between the Adh genotypes in rates of ethanol elimination. Rates of accumulation of ethanol in vivo are negatively associated with larval-to-adult survival of the Adh genotypes. The rank order of the maximum rates of the ADHs in elimination of propan-2-ol, as well as ethanol, is ADH-71k greater than ADH-F greater than ADH-S greater than simulans-ADH. The ratio of this maximum rate to ADH quantity reveals the rank order of ADH-S greater than ADH-F greater than ADH-71k greater than simulans-ADH, suggesting a compensation for allozymic efficiency by the ADH quantity in D. melanogaster. Our findings show that natural selection may act on the Adh polymorphism in larvae via differences in rates of alcohol metabolism.

Post-translational control of alcohol dehydrogenase levels in Drosophila melanogaster

A trans-acting regulatory gene that alters in vivo protein levels of alcohol dehydrogenase (ADH) has been mapped to a region of the third chromosome of Drosophila melanogaster. The gene has been found to affect the in vivo stability of ADH protein. It was not found to alter levels of total protein of two other enzymes assayed. The action of the gene over development and its possible mode of control are discussed.

Historical effective size and the level of genetic diversity in Drosophila melanogaster and Drosophila pseudoobscura

We report the results of a sequential gel electrophoretic study of protein variation in Drosophila melanogaster and its comparison with D. pseudoobscura. The number of alleles and mean heterozygosity were lower in D. melanogaster than in D. pseudoobscura. On the other hand, geographical populations of Drosophila melanogaster have been shown to be much more differentiated than those of D. pseudoobscura. The results suggest that in D. melanogaster low-frequency alleles have been lost during the colonization process and that major alleles have become differentiated among populations. Population bottlenecks, due to various causes, appear to have played a significant role in the shaping of genetic variation in natural populations of many species. It is proposed that a comparison of genetic variation at homologous gene loci between related species can bring out effects of historical bottlenecks and provide an alternative approach for analyzing causes of genetic variation in natural populations.

Use of P-element-mediated transformation to identify the molecular basis of naturally occurring variants affecting Adh expression in Drosophila melanogaster

The purpose of the work reported here is to identify the molecular basis of the difference in level of expression between the polymorphic Slow and Fast alcohol dehydrogenase (Adh) alleles in Drosophila melanogaster. Previous studies have shown that Fast lines typically have a two- to threefold higher activity level than Slow lines and they also have a substantially higher level of ADH-protein (estimated immunologically). The results of a restriction fragment length polymorphism study in relation to ADH activity variation had previously suggested that the difference in Adh expression between allozymes might not be due entirely to the amino acid replacement substitution, but could be due in part to linkage disequilibrium with a regulatory site polymorphism. Here we describe an approach that makes use of P-element-mediated transformation in order to identify the nucleotide substitution(s) responsible for this difference in ADH level. This approach consists of generating recombinants in vitro between Adh region clones derived from a typical Slow/Fast pair of alleles and then testing for the effects of particular restriction fragments on expression in vivo by transformation. Using this approach, the effect on both ADH activity and ADH-protein level clearly maps to a 2.3-kb restriction fragment that includes all of the Adh coding sequence and some intron and 3' flanking sequence, but excludes all of the 5' flanking sequence of the distal (adult) transcriptional unit. Comparison of Kreitman's DNA sequences for this fragment from several Slow and Fast alleles showing the typical difference in activity level shows that only three nucleotide substitutions distinguish all Fast from all Slow alleles. Thus, it is likely that one or more of these substitutions causes the major difference in Adh expression between allozymic classes. One of these substitutions is, of course, the Slow/Fast amino acid replacement substitution (at 1490) while the other two are nearby third position silent substitutions (at 1443 and 1527). A quantitative analysis of variation among transformant stocks shows that the P-element transformation approach can be used to localize even relatively small effects on gene expression (on the order of 20%).

The effect of temperature on biochemical and molecular properties of Drosophila alcohol dehydrogenase

The gene products of the two major alleles of alcohol dehydrogenase (ADH-F and ADH-S) have been subjected to kinetic and biochemical analyses over a range of temperatures. Although temperature was found to have a significant effect on both kinetic and biochemical properties of Drosophila ADH, no significant differential effect was observed between the major ADH allozymes. The results are discussed within the context of the selective maintenance of Adh polymorphism in natural populations.

Properties of allelic variants of phosphoglucomutase from the sea anemone Metridium senile

The phosphoglucomutase (Pgm) locus from populations of the sea anemone Metridium senile has three alleles in natural populations from the northeastern coast of North America. Two of the alleles exhibit clinal variation north of Cape Cod, suggesting a possible association of allele frequency with environmental temperature. This clinal pattern is reproducible and stable over at least brief periods of time. The allozymes encoded by each of the six Pgm genotypes have been partially purified and characterized. The symmetrical pH optimum for Vmax is pH 7.5; the apparent Km (Kmapp) of glucose-1-phosphate declines monotonically as the pH increases from 6.5 to 8.5. There are no pronounced differences in heat stabilities of PGM produced by various genotypes, nor are there significant differences in specific activities. There are no differences in the sensitivity of Vmax to temperature. Kmapp values are very low for all genotypes, ranging from about 2 to 12 microM, depending upon the temperature. Kmapp of glucose-1-phosphate declines as the temperature is raised for all genotypes, whether the pH is held constant or allowed to vary with the temperature. Under certain conditions, there are small significant differences among genotypes in Kappm values, but there is no systematic pattern to these differences. The present data provide no biochemical explanation for the maintenance of the Pgm cline by selection for functional differences under different thermal regimes.

The alcohol dehydrogenase alleloenzymes AdhS and AdhF from the fruitfly Drosophila melanogaster: an enzymatic rate assay to determine the active-site concentration

A rapid and reproducible enzymatic rate assay for the quantitative determination of the concentration of active sites is presented for the alleloenzymes AdhS and AdhF from Drosophila melanogaster. Using this procedure the turnover numbers as catalytic-center activities were found to be 12.2 sec-1 for AdhF and 3.4 sec-1 for AdhS with secondary alcohols. This showed a slower dissociation of the coenzyme from the binary enzyme-NADH complex with AdhS and hence a stronger binding of NADH to this alleloenzyme. With ethanol, the catalytic-center activity was 1.4 sec-1 for AdhS and 2.8 sec-1 for AdhF, and hence the single amino acid mutation distinguishing the two alleloenzymes also affected hydride transfer.

Estimating single gene effects on quantitative traits : 2. Statistical properties of five experimental methods

Experimental designs for measuring the effects of single loci on quantitative traits are compared for statistical properties. The designs tested are single population, combined strains, multiple strains, diallel of strains, and co-isogenic strains. Testing was done by simulating population genotypic and phenotypic arrays. Statistical properties measured are type I error, power, bias and efficiency. The relative ranking of designs is consistent for all properties and over eight conditions examined. The co-isogenic design is superior, followed closely by the single population method. The other three designs are similar in ability, with the diallel design somewhat superior. Based on its good statistical performance and wide feasibility, the single population method is recommended. The diallel method provides the most information on genetic components of variation.

Estimating single gene effects on quantitative traits 1. A diallel method applied to Est 6 in D. melanogaster

A modified diallel cross is used to estimate effects of alleles at the esterase 6 locus, relative to strain and environmental variance, in Drosophila melanogaster. Three strains homozygous for Est 6 (s) and three homozygous for Est 6 (F) were crossed in all 36 combinations. Male progeny were scored for mating speed, copula duration and esterase 6 enzyme activity, and all progeny for developmental time. These alleles show a significant additive effect on mating speed, but not on the other traits. Copula duration, developmental time and enzyme activity show additive strain genetic variance. Enzyme activity and developmental time also have maternal or X-chromosome strain variance, and these two traits are significantly correlated. This modified diallel method is generally useful because it permits the partition of trait variance into additive and dominant locus, background genetic and environmental components.

The purification and biochemical properties of alcohol dehydrogenase--"fast (Chateau Douglas)" from Drosophila melanogaster

Alcohol dehydrogenase has been purified from Drosophila melanogaster lines bearing the AdhF, AdhS, and AdhFCh.D. alleles. Biochemical investigations show that the properties of the purified enzymes are very similar to those of crude enzyme extracts except that the pure enzymes are more heat stable. ADH-FCh.D. resembles ADH-S very closely in specific activity, substrate specificity, and a number of kinetic parameters including limiting values for Km(app.) for ethanol. However, it is considerably more heat stable than either of the two common variants. ADH-F differs from ADH-S and ADH-FCh.D. particularly with regard to the rate of oxidation of secondary alcohols. Atomic absorbtion spectroscopy shows that all three allozymes lack zinc or other divalent cations as active-site components. Peptide mapping experiments identify one very active cysteinyl residue; and amide residues in the NAD+ binding domain.

Alcohol dehydrogenase thermostability variants in Drosophila melanogaster: comparison of activity ratios and enzyme levels

Representatives of five allozymic classes of Drosophila alcohol dehydrogenase have been compared with respect to their activity levels on two alcohol substrates, quantities of ADH protein, and stability in crude extracts. Within each allozymic class, strains from widely diverse geographic locations differ in their enzyme activity levels but are identical for a measure known as "activity ratio," which is obtained by dividing the average activity reading on isopropanol by that obtained with ethanol. They are also similar in the rate at which ADH activity declines in crude extracts held at 25 degrees C. For several of the fast-resistant and fast-moderate strains, differences in ADH activity are associated with differences in the amount of enzyme present. The catalytic efficiencies of the fast-resistant forms are considerably lower than those of the fast-moderate allozymes. The origin and persistence of the rare but ubiquitous fast-resistant allozyme is discussed.

Biochemical and molecular analysis of naturally occurring Adh variants in Drosophila melanogaster

The results of a detailed analysis of the biochemical and molecular basis of alcohol dehydrogenase (ADH) activity variation existing among six naturally occurring and one ethyl methanesulfonate-induced Adh variant strain of Drosophila melanogaster are presented. Significant specific activity differences exist among the strains but the majority of ADH activity variation can be accounted for by differences in levels of ADH protein. These protein level differences can, in turn, be accounted for by ADH synthesis rate variation, which positively correlates with in vivo levels of cytoplasmic Adh mRNA. The functional variability is correlated with known structural variation in and around the area of the Adh gene.

The effect of alcohol stress on nicotinamide adenine dinucleotide (NAD+) levels in Drosophila

Previous studies carried out in mammalian systems indicated that an organism's NAD+/NADH balance is carefully regulated but can be destabilized by dietary stresses. Since Drosophila alcohol dehydrogenase (ADH) uses NAD+ to remove a hydrogen from ethanol in the first step of alcohol catabolism, it is possible that under alcohol stress conditions the in vivo NAD+ levels in Drosophila may decrease. In this study genetically homozygous flies were stressed with maximally sublethal concentrations of ethanol (10%) for periods of up to 24 hr. The results indicate that NAD+ levels do in fact drop by at least 20% in response to ethanol stress. Evidence is presented that suggests that this decrease is the direct result of ADH-mediated catabolism.

Selection at the alcohol dehydrogenase locus of Drosophila melanogaster: effects of ethanol and temperature

Drosophila melanogaster larvae were subjected to 10 generations of selection on 6% ethanol at 17, 25, and 30 degrees C. For each temperature there was a significant (P less than 0.01) increase in the frequency of the Adh isoallele. Controls with no ethanol showed no change in the frequency of the AdhF isoallele. Larvae subjected to stronger selection on 8% ethanol confirmed the results. When adults of various ages were subjected to 16 and 32 degrees C, the ADHF isoenzyme retained its twofold advantage in activity over ADHS regardless of the temperature. The same result was obtained with larvae at 16 and 35 degrees C. Although some effect of temperature was demonstrated, it was concluded that the effect was not strong enough for temperature to be a selective factor under the conditions studied. However, ethanol is a strong selective factor for laboratory populations.

Genetic variation in the expression of ADH in Drosophila melanogaster

Several chromosomes derived from natural populations have been identified that affect the expression of alcohol dehydrogenase (ADH). Second chromosomes, which also carry the structural gene Adh, show a great deal of polymorphism of genetic elements that determine how much enzyme protein accumulates. The level of enzyme was measured in third instar larvae, 6-to-8-day-old males and in larval fat bodies and alimentary canals. In general, activities in the different organs and stages are highly correlated with one another. One line was found, however, in which the ADH level in the fat body is more than twice the level one would expect on the basis of the activity in alimentary canal. We have also found evidence of third-chromosome elements that affect the level of ADH.

Changes in levels of alcohol dehydrogenase during the development of Drosophila melanogaster

The results of an analysis of the biochemical basis of changes in alcohol dehydrogenase (E.C.1.1.1.1) activity over Drosophila development are presented. The data indicate that (1) the characteristic changes that occur in ADH activity over development are predominantly, it not exclusively, the result of quantitative changes in the amount of enzyme present rather than qualitative changes affecting the enzyme's specific activity and (2) the fluctuations in amount of ADH which occur during development are not the result of the only known form of post-translational modification capable of affecting the biochemical properties of the enzyme. We conclude that developmental changes in amount of ADH are most likely the result of fluctuations in the turnover of the ADH protein.

Effect of environmental alcohol on in vivo properties of Drosophila alcohol dehydrogenase

The effects of environmental 2-propanol on the in vivo properties of Drosophila alcohol dehydrogenase (E.C. 1..1.1.1.) are presented. Exposed flies were found to exhibit a significant decrease in ADH specific activity with a concomitant increase in the enzyme's relative in vivo stability and concentration. The possible adaptive significance of the observed responses is discussed.