Geographical variation in AdhF and alcoholic resource utilization in Indian populations of Drosophila melanogaster

Indian geographical populations of Drosophila melanogaster, collected at latitude 10–32.3 ^oN, longitude 76.1–80.1 ^oE and altitude 16–2050 m, were analysed for changes in Adh ¹ frequency and utilization potential of diverse alcoholic resources. Until now, there have been limited data on climatic association of correlated changes on these aspects in continental populations of D. melanogaster. Indian populations demonstrate an increase in Adh ^F frequency by 0.04 per degree latitude and significantly higher utilization of ethanol (9.0–15.2%), acetic acid (8.1–12.5%), n-propanol (2.55-4.25%), 2-propanol (1.5-3.5%), n-butanol (2.15 3.5%) and 2-butanol (0.68-1.2%). Data also revealed significant correlation with latitude as well as altitude. Regression analysis of climatic data from collection sites confirmed the observed clinal variation of Adh ^F as well as alcoholic utilization in D. melanogaster. On the Indian subcontinent, variation in Adh ^F frequency and alcoholic resource utilization along increasing latitude as well as altitude are due to climatic selection factors such as temperature and rainfall.     

An ecological interaction between citrus fruit, Penicillium moulds and Drosophila immigrans Sturtevant (Diptera: Drosophilidae)

Abstract. 1. Potential Drosophila breeding sites were collected from a fruit market, and the adults allowed to emerge from them.
2. D.immigrans and D.melanogaster were the species with the highest frequency of emergences from citrus fruit.
3. D.immigrans was especially associated with citrus fruits infected with Penicillium italicum or P.digitatum , two specialist moulds of citrus. D.melanogaster was more often found in uninfected fruit.
4. In the laboratory D.immigrans larvae survived better than D.melanogaster larvae on Penicillium-infected citrus fruit.
5. These adaptations suggest that D.immigrans may have originally evolved as a citrus specialist, becoming a domestic species as these fruits were exploited commercially.     

Metabolic response to ethanol and isopropanol in D. funebris and D. immigrans

Ethanol at low concentration increases larval viability in D. funebris and D. melanogaster and decreases it in D. immigrans. Isopropanol decreases viability in all three species. Isopropanol depresses alcohol dehydrogenase activity. This is accompanied by a change in the relative proportion of electrophoretic forms of the enzyme. Acetone appears in the medium when larvae of D. funebris and D. immigrans develop in the presence of isopropanol. It can be transformed again into isopropanol on reaching a threshold value. It seems that this transformation cannot be carried out by alcohol dehydrogenase alone.     

Genetic and developmental factors in the olfactory response of Drosophila melanogaster larvae to alcohols.

Olfactory responses of Drosophila melanogaster larvae to a homologous series of primary alcohols (methanol ... decanol) were tested. Alcohols at either extreme of the chain lengths studied (methanol, ethanol and decanol) evoked no significant responses. Heptanol and nonanol both produced dose-independent responses, larvae being attracted to heptanol and repulsed by nonanol. The remaining alcohols elicited dose-related attractive responses. Responses to hexanol and nonanol decline with increasing larval age. Genetic differences were found for the response to heptanol, with larvae from a Japanese strain, Katsunuma, being indifferent to this substance. Chromosome exchange revealed that a major factor involved in the response to heptanol is located on chromosome II; factors on chromosome III quantitatively modulate this response. Three mutant strains were isolated following EMS mutagenesis of chromosome III. These three strains, IndifferentA, IndifferentB and IndifferentC, show incomplete or total anosmia when stimulated with nonanol. Adult flies from these strains show similar effects. IndifferenB and C strains are dominant over the Canton-S control strain; the IndifferentA strain shows semi-dominance. Results are discussed in the light of the ecology of Drosophila larvae and the relation between olfactory stimulus and receptor conformation and number.     

Divergent strategies for adaptation to desiccation stress in two Drosophila species of immigrans group

Water balance mechanisms have been investigated in desert Drosophila species of the subgenus Drosophila from North America, but changes in mesic species of subgenus Drosophila from other continents have received lesser attention. We found divergent strategies for coping with desiccation stress in two species of immigrans group--D. immigrans and D. nasuta. In contrast to clinal variation for body melanization in D. immigrans, cuticular lipid mass showed a positive cline in D. nasuta across a latitudinal transect (10°46'-31°43'N). Based on isofemale lines variability, body melanization showed positive correlation with desiccation resistance in D. immigrans but not in D. nasuta. The use of organic solvents has supported water proofing role of cuticular lipids in D. nasuta but not in D. immigrans. A comparative analysis of water budget of these two species showed that higher water content, reduced rate of water loss and greater dehydration tolerance confer higher desiccation resistance in D. immigrans while the reduced rate of water loss is the only possible mechanism to enhance desiccation tolerance in D. nasuta. We found that carbohydrates act as metabolic fuel during desiccation stress in both the species, whereas their rates of utilization differ significantly between these two species. Further, acclimation to dehydration stress improved desiccation resistance due to increase in the level of carbohydrates in D. immigrans but not in D. nasuta. Thus, populations of D. immigrans and D. nasuta have evolved different water balance mechanisms under shared environmental conditions. Multiple measures of desiccation resistance in D. immigrans but reduction in water loss in D. nasuta are consistent with their different levels of adaptive responses to wet and dry conditions on the Indian subcontinent.     

Olfactory shifts parallel superspecialism for toxic fruit in Drosophila melanogaster sibling, D. sechellia

Olfaction in the fruit fly Drosophila melanogaster is increasingly understood, from ligand-receptor-neuron combinations to their axonal projection patterns into the antennal lobe . Drosophila thus offers an excellent opportunity to study the evolutionary and ecological dynamics of olfactory systems. We compared the structure and function of the generalist D. melanogaster with that of specialist D. sechellia, which oviposits exclusively on morinda fruit . Our analyses show that whereas the fruit's headspace was dominated by acids, antennae responded most strongly to hexanoates. D. sechellia exhibited an extraordinarily strong response to methyl hexanoate (MeHex). Behaviorally, D. sechellia was much more attracted to these morinda fruit volatiles than was D. melanogaster. The high sensitivity to MeHex was paralleled by a 2.5x-3 x overrepresentation of MeHex neurons on the antenna and a concordant 2.9 x increase in volume of the corresponding glomerulus as compared to D. melanogaster. In addition, the MeHex neuron exhibited an extreme sensitivity down to femtograms of its ligand. In contrast, no peripherally mediated shift was found paralleling D. sechellia's increased attraction to acids. These findings are a demonstration of evolution acting at several levels in the olfactory circuitry in mediating a fruit fly's unique preference for fruit toxic to its sibling species .     

Phylogeny of the Drosophila immigrans species group (Diptera: Drosophilidae) based on Adh and Gpdh sequences

The immigrans species group in the Drosophilinae is one of the representative species groups of Drosophila in East Asia. Although this group constitutes a significant part of the drosophilid fauna in the Old World, only a few species have been analyzed in previous molecular phylogenetic studies. To study the phylogeny of the immigrans group, we analyzed the nucleotide sequences of two nuclear genes, alcohol dehydrogenase (Adh) and glycerol-3-phosphate dehydrogenase (Gpdh), for 36 drosophilid species, including 12 species of the immigrans group. In the resultant phylogenetic trees, 10 species of the immigrans group (D. immigrans, D. formosana, D. ruberrima, D. albomicans, D. nasuta, D. neonasuta, D. pallidifrons, D. hypocausta, D. neohypocausta, D. siamana) consistently formed a clade (the immigrans group proper), although the phylogeny within this clade did not exactly correspond to the classification of species subgroups. However, D. annulipes and D. quadrilineata, both of which belong to the quadrilineata subgroup of the immigrans group, were not included in the immigrans group proper. Furthermore, we obtained the unexpected result that D. annulipes was included in a clade comprising Scaptomyza and Hawaiian Drosophila, together with D. maculinotata of the funebris group, although the phylogenetic relationships within this clade remain uncertain and need to be substantiated with further studies. Thus, according to the present study, the immigrans group is polyphyletic.     

The role of frass and cocoon volatiles in host location by Monodontomerus aeneus, a parasitoid of Megachilid solitary bees

Monodontomerus aeneus (Fonscolombe) is a parasitic wasp that oviposits on the prepupae and pupae of Osmia cornuta (Latreille) and other solitary bee species. A two-armed olfactometer was used to test the olfactory attractiveness of O. cornuta prepupae, cocoon, and larval frass to female M. aeneus. Both cocoon and frass attracted the female parasitoids, but frass alone was more attractive than the cocoon and the cocoon with frass was more attractive than frass alone. Female parasitoids were not attracted by the host prepupa. M33 (methanol) was the organic volatile most emitted by cocoons and m61 (acetic acid) was the compound most emitted by frass. However, cocoons showed higher emission for almost all compounds, including m61 (acetic acid). Although acetic acid alone attracted M. aeneus, a complex volatile signal is probably involved in the attraction process because the ratio of acetic acid and acetaldehyde characteristic of the frass was more attractive than other ratios.     

Some behavioral features in Drosophila melanogaster lines carrying a flamenco gene mutation]

Olfactory sensitivity and locomotor activity was assayed in Drosophila melanogaster strains carrying a mutation of the flamenco gene, which controls transposition of the mobile genetic element 4 (MGE4) retrotransposon the gypsy mobile element. A change in olfactory sensitivity was detected. The reaction to the odor of acetic acid was inverted in flies of the mutator strain (MS), which carried the flam mutation and active MGE4 copies and were characterized by genetic instability. Flies of the genetically unstable strains displayed a lower locomotor activity. The behavioral changes in MS flies can be explained by the pleiotropic effect of the flam mutation or by insertion mutations which arise in behavior genes as a result of genome destabilization by MGE4.     

Intraspecific and interspecific larval interaction in Drosophila assessed by integrated fitness measure

Intraspecific density effect was investigated for D. simulans , D. suzukii , D. auraria , D. rufa and D. immigrans , and interspecific density effect was examined for combinations of D. simulans , D. rufa and D. immigrans . Different numbers of their eggs were introduced to artificial substrates, and intra- and interspecific interaction were evaluated on the basis of per capita egg production of individuals (eggs) introduced. If individuals died before pupation, their per capita egg production was zero; if individuals survived to pupae, their per capita egg production was estimated from their size based on the relation between the pupal size and lifetime egg production. Per capita egg production thus estimated generally decreased with the increase of the density of conspecific larvae, although a slight increase was detected at high densities in some cases. When two species were introduced, per capita egg production of a species was reduced only when the larval density of co-introduced species was very high, suggesting weak interspecific competition. Interspecific interaction was asymmetric; the effect of D. simulans on D. rufa and D. immigrans was often significantly negative, but the effect of D. rufa or D. immigrans on D. simulans was not significant.     

Alcohol dehydrogenase from Drosophila funebris and Drosophila immigrans: Molecular and evolutionary aspects

Alcohol dehydrogenase from Drosophila funebris and D. immigrans is evident at all developmental stages. The highest activity level appears in third-instar larvae and declines to a lower level at all later stages of development. Both species are monomorphic. The enzyme is a dimer consisting of two identical subunits with molecular weight 27,600. The pI values are 8.6 for D. funebris and 9.02 for D. immigrans. The optimum pH is 8.6 and 8.7 for D. funebris and D. immigrans, respectively. The Km values for NAD+, propan-2-ol, and butan-2-ol are 0.15, 2.90, and 2.08 mM, respectively, for D. funebris and 0.16, 1.53, and 1.49 mM, respectively, for D. immigrans. The half-life for the purified enzyme is 45 days for D. funebris and 18 days for D. immigrans at 4 degrees C. Data on the amino acid composition of both enzymes and peptide maps of alcohol dehydrogenase of D. immigrans reveal that they have marked homologies between them and also with alcohol dehydrogenases of other species. D. funebris shows reduced levels of alcohol dehydrogenase synthesis but has the highest specific activity reported to date for a Drosophila species. D. immigrans synthesises six times more enzyme but the specific activity is comparable to that of other species of Drosophila. This evidence could explain their different alcohol tolerance. The molecular properties of these alcohol dehydrogenases together with other species of Drosophila suggest that the alcohol dehydrogenase of Drosophila has arisen by divergent evolution from a common ancestral gene.     

Molecular phylogeny and divergence times of drosophilid species

The phylogenetic relationships and divergence times of 39 drosophilid species were studied by using the coding region of the Adh gene. Four genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and Sophophora--were included. After conducting statistical analyses of the nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila as the outgroup. The phylogenetic tree obtained showed that the first major division of drosophilid species occurs between subgenus Sophophora (genus Drosophila) and the group including subgenera Drosophila and Engiscaptomyza plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then divided into D. willistoni and the clade of D. obscura and D. melanogaster species groups. In the other major drosophilid group, Zaprionus first separates from the other species, and then D. immigrans leaves the remaining group of species. This remaining group then splits into the D. repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila, Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups is monophyletic. The splitting of subgenera Drosophila and Sophophora apparently occurred about 40 Mya, whereas the D. repleta group and the Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya, suggesting that Scaptomyza experienced a rapid morphological evolution. The D. obscura and D. melanogaster groups apparently diverged about 25 Mya. Many of the D. repleta group species studied here have two functional Adh genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two duplication events.      

Structural analysis of glycerol-3-phosphate dehydrogenase from severalDrosophila species

This report describes preliminary protein structural studies of glycerol-3-phosphate dehydrogenase (alpha-GPDH) from Drosophila spp. and an important innovative feature of our enzyme purification protocol. The scheme involves the coupling of substrate (alpha-glycerophosphate) elution from CM-Sephadex and cofactor (NADH) elution from Affi-Gel blue resin. Using this method a 32.7% yield and a 111-fold purification were obtained from a D. melanogaster line carrying the alpha-GpdhS allele at the alpha-Gpdh locus. The product obtained from 0 to 3-day-old adult flies was electrophoretically homogeneous and consisted mainly of the adult alpha-GPDH-1 isozyme. The method was used to obtain alpha-GPDH protein from D. melanogaster (two lines), D. hydei, D. immigrans, and D. mercatorum. Peptide mapping revealed structural differences among the enzymes from the different species, and amino acid sequencing showed many similarities between D. melanogaster alpha-GPDH and the rabbit muscle enzyme.     

DNA homologies among Drosophila species and a related genus.

Deoxyribonucleic acids of members of the family Drosophilidae; e.g., D. melanogaster, D. robusta, D. pellewae, D, immigrans, D. mcclintockae, D. calloptera, C. procnemis and from a tissue culture cells of D. melanogaster have been compared with respect to base composition, heterogenecity, and nucleotide sequence homology. Considerable heterogeneity exists in DNA's from 3rd instar larvae and tissue culture cells. The DNA base composition of adult species ranges from 33-42 moles percent GC; in addition a polydAT component is apparent in larval DNA's. There are about 21 and 29 percent intragenomic homology in DNA's of D. melanogaster and D. immigrans, respectively. Relatively large differences were revealed in the nucleotide sequences of several species by DNA hybridization and thermal stability studies.     

Molecular evolution of Drosophila odorant receptor genes

A total of 752 odorant receptor (Or) genes, including pseudogenes, were identified in 11 Drosophila species and named after their orthologs in Drosophila melanogaster. The 813 Or genes, including 61 from D. melanogaster, were classified into 59 orthologous groups that are well supported by gene phylogeny. By reconciling with the gene family phylogeny, we estimated the number of gene duplication/loss events and intron gain/loss events in the species phylogeny. We found that these events are particularly frequent in Drosophila grimshawi, Drosophila willistoni, and obscura group. More than half of the duplicated genes stay as tandem arrays, whose size range from 2 to 8. These genes vary in sequence and some likely underwent positive selection, indicating that the gene duplication was important for flies to acquire new olfactory functions. We hypothesize that Or genes conferred the basic olfactory repertoire to ancestral flies before the speciation of the Drosophila and Sophophora subgenera about 40 Mya. This repertoire has been largely maintained in the current species, whereas lineage-specific gene duplication seems to have led to additional specialization in some species in response to specific ecological conditions.     

视觉和嗅觉信号对果蝇食物搜寻行为的协同作用

为了探索视觉和嗅觉信号在昆虫食物搜寻过程中的作用, 本研究利用杨梅和橘子为引诱物, 在实验室条件下测定了嗅觉和视觉信号诱集到的黑腹果蝇Drosophila melanogaster数量, 分析了嗅觉经历对果蝇嗅觉和视觉食物搜寻的影响。发现同源性嗅觉和视觉信号存在的杨梅诱集到的果蝇数量显著大于单一的视觉信号和嗅觉信号, 但异源性嗅觉和视觉信号组合诱集到的果蝇数量和单独的嗅觉信号相似。嗅觉信号预处理不仅能够显著增加嗅觉信号诱集到的果蝇数量, 其中杨梅嗅觉信号对杨梅预处理果蝇的吸引能力与视觉和嗅觉信号存在的杨梅相似, 而且异源性嗅觉和视觉信号组合诱集到的预处理果蝇数量也不低于视觉和嗅觉信号存在的杨梅。另外杨梅嗅觉信号预处理也能够显著增强杨梅视觉信号诱集到的果蝇数量。但嗅觉预处理并不会改变同源性视觉和嗅觉信号组合诱集到的果蝇数量。本研究表明, 果蝇同时利用视觉和嗅觉信号进行食物搜寻, 因此同源性视觉和嗅觉信号在果蝇诱集过程中具有协同作用。另外果蝇具有较强的记忆和学习能力, 能够将记忆中的嗅觉信号应用于食物搜寻。本研究结果不仅有利于我们了解果蝇在自然状态下的食物搜寻机制, 而且有利于开发更有效的果蝇新型诱捕器。     

Oskar controls morphology of polar granules and nuclear bodies in Drosophila

Germ cell formation in Drosophila relies on polar granules, which are large ribonucleoprotein complexes found at the posterior end of the embryo. The granules undergo characteristic changes in morphology during development, including the assembly of multiple spherical bodies from smaller precursors. Several polar granule components, both protein and RNA, have been identified. One of these, the protein Oskar, acts to initiate granule formation during oogenesis and to recruit other granule components. To investigate whether Oskar has a continuing role in organization of the granules and control of their morphology, we took advantage of species-specific differences in polar granule structure. The polar granules of D. immigrans fuse into a single large oblong aggregate, as opposed to the multiple, distinct, spherical granules of D. melanogaster embryos. D. immigrans oskar rescues the body patterning and pole cell defects of embryos from D. melanogaster oskar(-) mothers, and converts the morphology of the polar granules to that of D. immigrans. The nuclear bodies, which are structures that appear to be closely related to polar granules, are also converted to the D. immigrans type morphology. We conclude that oskar plays a persistent and central role in the polar granules, not only initiating their formation but also controlling their organization and morphology.     

伊米果蝇种组（Drosophila immigrans species group）H2a-H2b和Cyt b分子系统发育关系（简报）

伊米果蝇种组(Drosophila immigrans speciesgroup)是果蝇科(Drosophilidae)、果蝇属(Drosophi-la)、果蝇亚属(Drosophila)中数量最多的一个类群,主要分布于东洋区。在分类学上该种组分为nasuta、immigrans、hypocausta、quadrilineata和curviceps五个种亚组(species subgroup)[1],东洋区果蝇区系中伊米果蝇种组中包括94个种,其中有45个种分布在中国[2]。而且curviceps种亚组是1992年新建立的中国特有果蝇类群[3]。迄今,对伊米果蝇种组分子系统关系的报道还很少,有些物种的归属仍存在争议。伊米果蝇种组还有些问题需要探讨[4]。组蛋白基因…     

Production of Acetic Acid and Other Volatile Compounds by Leuconostoc citrovorum and Leuconostoc dextranicum

Single-strain milk cultures of Leuconostoc dextranicum are capable of reducing added acetaldehyde, propionaldehyde, and butanone to the corresponding alcohols at 30 C. L. dextranicum and L. citrovorum reduced propionaldehyde to n-propanol quantitatively in 30 hr, and the reduction of this compound paralleled culture growth. Under unagitated conditions, these organisms produced large amounts of acetic acid and ethyl alcohol. The yield of acetic acid increased when cultures were agitated during growth. This increase in acetic acid production was accompanied by a 20- to 70-fold decrease in ethyl alcohol. The addition of acetaldehyde to the fermentation caused a reduction in the final concentration of acetic acid.