At high dietary levels ethanol alters the structure of mid- and hindgut epithelial cells of Drosophila melanogaster larvae

Stable Host Gene Expression in the Gut of Adult Drosophila melanogaster with Different Bacterial Mono-Associations

There is growing evidence that the microbes found in the digestive tracts of animals influence host biology, but we still do not understand how they accomplish this. Here, we evaluated how different microbial species commonly associated with laboratory-reared Drosophila melanogaster impact host biology at the level of gene expression in the dissected adult gut and in the entire adult organism. We observed that guts from animals associated from the embryonic stage with either zero, one or three bacterial species demonstrated indistinguishable transcriptional profiles. Additionally, we found that the gut transcriptional profiles of animals reared in the presence of the yeast Saccharomyces cerevisiae alone or in combination with bacteria could recapitulate those of conventionally-reared animals. In contrast, we found whole body transcriptional profiles of conventionally-reared animals were distinct from all of the treatments tested. Our data suggest that adult flies are insensitive to the ingestion of the bacteria found in their gut, but that prior to adulthood, different microbes impact the host in ways that lead to global transcriptional differences observable across the whole adult body.

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.

The toxicities of short-chain primary alcohols and the accumulation of storage bodies in the larval fat body of Drosophila melanogaster

In terms of the LD50 values for alcohols, third-instar wild-type larvae of Drosophila melanogaster had a greater tolerance to ethanol, n-propanol and n-butanol than alcohol dehydrogenase (ADH)-deficient larvae. The tolerances of the two strains to methanol were similar. Methanol, ethanol, n-propanol and n-butanol all induced higher ADH activity in wild-type larvae. Ethanol, n-propanol, methanol and n-butanol slowed the growth for ADH-deficient larvae, whereas only methanol had this effect on wild-type larvae. The proportion of wild-type pupae to eclose was increased by n-butanol, n-propanol and ethanol. Cytometric methods to measure the densities of storage bodies--glycogen rosettes, protein bodies and lipid droplets--in fat body cells indicated that all of the test alcohols exerted some negative influence on the accumulation of at least one type of storage body. Analyses of total protein, glycogen and acylglycerols indicated that ethanol and n-butanol were associated with an accumulation of acylglycerols in both wild-type and ADH-deficient larvae; whereas, the other test alcohols resulted in low glycogen and protein concentrations in both test strains. The short-chain primary alcohols may in part be toxic to larvae because of disruptions in metabolism that lead to reductions in one or more kinds of storage bodies in the larval fat body.

Protective effect of ethanol on X-ray-induced mitotic recombination in Drosophila melanogaster

The effect of ethanol pretreatment on X-ray-induced mitotic recombination in D. melanogaster females was investigated by means of the white/white+ (w/w+) spot test. White females inseminated by yellow males were allowed to oviposit for 8 hr on medium containing 5%, 7.5% and 10% (v/v) ethanol and submitted to 10 Gy of X-rays 52 hr after the beginning of the egg laying period (chronic treatments). For acute treatments 56 +/- 4-hr-old larvae grown in regular medium were held in petri dishes containing filter paper soaked with 50% (v/v) ethanol for 30 min before being irradiated with 10 Gy. The emerging heterozygous w/w+ females were inspected for the presence of white spots (LS) in their eyes. Acute ethanol pretreatments lead to a significant reduction in the frequency of LS. This is suggested to be due to the scavenging by ethanol of free radicals originating during irradiation. If so, the contribution of the indirect action of radiation to mitotic recombination induced by X-rays must be significant. Chronic ethanol pretreatments also resulted in a decrease of LS, though impairment of larval development by ethanol may have partly contributed to the effect observed. At the concentrations tested, ethanol by itself did not modify the frequency of LS observed in the control.

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).