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Characterization of human homologs of the Drosophila seven in absentia (sina) gene.

Studies of Drosophila photoreceptor development have illustrated the means by which signal transduction events regulate cell fate decisions in a multicellular organization. Development of the R7 photoreceptor is best understood, and its formation is dependent on the seven in absentia (sina) gene. We have characterized two highly conserved human homologs of sina, termed SIAH1 and SIAH2. SIAH1 maps to chromosome 16q12 and encodes a 282-amino-acid protein with 76% amino acid identity to the Drosophila SINA protein. SIAH2 maps to chromosome 3q25 and encodes a 324-amino-acid protein that shares 68% identity with Drosophila SINA and 77% identity with human SIAH1. SIAH1 and SIAH2 were expressed in many normal and neoplastic tissues, and only subtle differences in their expression were noted. However, one of three murine homologs, Siah1B, was strongly induced in fibroblasts undergoing apoptotic cell death. While a previous study suggested that SINA was a nuclear protein, epitope-tagged SINA and SIAH1 proteins were found in the cytoplasm of Drosophila and mammalian cells. Their substantial evolutionary conservation, role in specifying cell fate, and activation in apoptotic cells suggest the SIAH proteins have important roles in vertebrate development. Furthermore, given the role of sina in Drosophila photoreceptor development, SIAH2 is a candidate for the Usher syndrome type 3 gene at chromosome 3q21-q25.

Adult↗

Identification of candidate Drosophila olfactory receptors from genomic DNA sequence.

We have taken advantage of the availability of a large amount of Drosophila genomic DNA sequence in the Berkeley Drosophila Genome Project database ( approximately 1/5 of the genome) to identify a family of novel seven transmembrane domain encoding genes that are putative Drosophila olfactory receptors. Members of the family are expressed in distinct subsets of olfactory neurons, and certain family members are restricted to distinct portions of the olfactory system. This pattern of expression has interesting similarities to and differences from the expression patterns observed for olfactory receptors in vertebrates. The Drosophila olfactory system is simpler than mammalian systems, yet it is complex enough to present a fascinating system in which to study neural information processing. Moreover, the powerful genetic manipulations available in Drosophila, when combined with electrophysiological and behavioral analyses, make this an attractive model system in which to study olfactory discrimination.

Amino Acid Sequence↗

Fusion between human and Drosophila melanogaster cells induced by polyethylene glycol.

Polyethylene glycol was used to induce interspecific somatic cell fusion between human fibroblasts (stock F6) and Drosophila melanogaster cells from established cell lines (Cl 82 and 11 P102), characterized by different ploidy levels. The present investigation defines some parameters for Drosophila cell fusion and interspecific fusion between Drosophila and human cells. The cytological analysis provided evidence of spontaneous as well as induced human-Drosophila heterokaryon formation. The presence in the same cell of two types of nuclei, distinguishable because of their different size and morphology, was confirmed autoradiographically by 3H-thymidine pre-labelling of Drosophila cells. Furthermore, the retained DNA synthetic activity and some examples of mitotic figures of both types of nuclei in the heterokaryons indicate the viability of the fused cells.

Animals↗

Phylogeny of Drosophila and related genera inferred from the nucleotide sequence of the Cu,Zn Sod gene.

The phylogeny and taxonomy of the drosophilids have been the subject of extensive investigations. Recently, Grimaldi (1990) has challenged some common conceptions, and several sets of molecular data have provided information not always compatible with other taxonomic knowledge or consistent with each other. We present the coding nucleotide sequence of the Cu,Zn superoxide dismutase gene (Sod) for 15 species, which include the medfly Ceratitis capitata (family Tephritidae), the genera Chymomyza and Zaprionus, and representatives of the subgenera Dorsilopha, Drosophila, Hirtodrosophila, Scaptodrosophila, and Sophophora. Phylogenetic analysis of the Sod sequences indicates that Scaptodrosophila and Chymomyza branched off the main lineage before the major Drosophila radiations. The presence of a second intron in Chymomyza and Scaptodrosophila (as well as in the medfly) confirms the early divergence of these two taxa. This second intron became deleted from the main lineage before the major Drosophila radiations. According to the Sod sequences, Sophophora (including the melanogaster, obscura, saltans, and willistoni species groups) is older than the subgenus Drosophila; a deep branch splits the willistoni and saltans groups from the melanogaster and obscura groups. The genus Zaprionus and the subgenera Dorsilopha and Hirtodrosophila appear as branches of a prolific "bush" that also embraces the numerous species of the subgenus Drosophila. The Sod results corroborate in many, but not all, respects Throckmorton's (King, R.C. (ed) Handbook of Genetics. Plenum Press, New York, pp. 421-469, 1975) phylogeny; are inconsistent in some important ways with Grimaldi's (Bull. Am. Museum Nat. Hist. 197: 1-139, 1990) cladistic analysis; and also are inconsistent with some inferences based on mitochondrial DNA data. The Sod results manifest how, in addition to the information derived from nucleotide sequences, structural features (i.e., the deletion of an intron) can help resolve phylogenetic issues.

Animals↗

Juvenile hormone stimulation of ornithine decarboxylase activity during vitellogenesis in Drosophila melanogaster.

The activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, becomes elevated in intact female Drosophila melanogaster shortly after adult eclosion. This activity reaches a peak at 24 h following eclosion, and then drops to lower levels by 48 h. This pattern is not observed in males, consistent with the hypothesis that polyamine synthesis is involved in ovarian maturation in Drosophila. Abdomens isolated within 2 h of adult eclosion do not display elevated ODC activity or ovarian maturation. However, a 250-ng dose of the juvenile hormone analog methoprene (ZR-515) applied in acetone to these abdomens, recovers ovarian maturation and causes a 5-10 fold increase in enzyme activity over controls treated with acetone alone. The same dose of the inactive precursor methyl farnesoate caused no such increase, whereas a 500-ng dose of the newly discovered natural Drosophila JHB3 stimulated a four-fold response. The response to methoprene was dose-dependent, showing stimulatory activity at a dose as low as 10 ng. This stimulation by JHA is rapid, occurring between 1 and 3 h following hormone treatment, reminiscent of JH induction of fat body vitellogenin synthesis in Drosophila. Elevated ODC activity appeared to be localized in the adult fat body. During embryogenesis, ODC activity remained undetectable until just prior to hatching, when a large increase was detected. We postulate that JH may, either directly or indirectly, regulate polyamine biosynthesis in vivo, and that this synthesis may be required for the production of macromolecules during Drosophila vitellogenesis or embryogenesis.

Animals↗

Correlation of guanosine triphosphate cyclohydrolase activity and the synthesis of pterins in Drosophila melanogaster.

The enzyme guanosine triphosphate cyclohydrolase (GTP cyclohydrolase), which in bacteria is known to be the first enzyme in the biosynthetic pathway for the synthesis of pteridines, has been discovered in extracts of Drosophila melanogaster. Most of the enzyme (80%) is located in the head of the adult fly. An analysis of enzyme activity during development in Drosophila has revealed the presence of a relatively small peak of activity at pupariation and a much larger peak that appears at about the time of eclosion. Enzyme activity declines radidly as the fly ages. Analysis for the production of the typical pteridine pigments of Drosophila have indicated that the small peak of GTP cyclohydrolase activity evident at pupariation coincides with the appearance of isoxanthopterin, sepiapterin, and pterin, and the larger peak at eclosion roughly corresponds to the accumulation of drospterin as well as to the appearence in larger amounts of pterin and sepiaterin. These observations strongly suggest that in Drosophila, like bacteria, GTP cyclohydrolase is involved in the biosynthesis of pteridines. Analyses of a variety of zeste mutants of Drosophila melanogaster have shown that these mutants all contain GTP cyclohydrolase equal approximately to the amount found in the wild-type fly. These observations do not support the suggestions made by Rasmusson et al. (1973) that zeste is the strucural locus for GTP cyclohydrolase.

Aminohydrolases↗

Insectivory and social digestion in Drosophila.

It has long believed that Drosophila larvae feed almost entirely by ingesting yeast and possibly other microorganisms that are associated with fermenting fruits or other vegetable matter. However, we have discovered that the larvae of a number of Drosophila species can consume such diverse substrates as insect tissues, including the exoskeleton. Experiments reported here, which include raising sterile dechorionated eggs to adulthood on adult carcasses under axenic conditions, show that larvae can consume complex chitinous substrates directly without the assistance of microorganisms. We show that Drosophila larvae are able externally to digest amylose, cellulose, and chitin, without coming into physical contact with them. We conclude that not only do Drosophila larvae produce enzymes enabling them to digest a wide variety of substrates, but also these enzymes are egested onto the substrates so that at least some digestion, especially of large polymers, takes place externally. Finally, we suggest that the phenomenon of external digestion explains both the previously unexplained massiveness of Drosophila salivary glands and their chromosomes and the tendency of larvae to cluster, which may also be true of other dipterans.

Amylose↗

The three-dimensional structure of the central region in a synaptonemal complex: a comparison between rat and two insect species, Drosophila melanogaster and Blaps cribrosa.

The highly ordered central region of the synaptonemal complex (SC) in Blaps cribrosa has recently been studied by electron microscope tomography (EMT), and a simple three-dimensional model presented. Using the same experimental approach we have now compared the central region in Blaps with the central regions in Drosophila melanogaster and rat. In all three species, the SCs exhibit a central element (CE) flanked by two lateral elements (LEs). The central region between the two LEs is crossed by transverse filaments (TFs). The Blaps CE element is the most ordered one with a well-defined ladder-like structure with two longitudinal components bridged by a number of regularly spaced transverse components, the rungs of the ladder. At the junctions between the longitudinal and transverse components there are prominent dense structures. The CE is multi-layered with the ladders of the separate layers in approximate register. In Drosophila the transverse CE components are as distinct and well organized as in Blaps, while in rat they are present but are less frequent and less well ordered. The longitudinal CE components in Drosophila are often fragmented and even more so in rat. The tomographic analysis revealed that in all three species the central region contains the same structural units: a single TF associated with two short pillars (or globules), which correspond to the junction structures. A fibrous lattice connects the two pillars/globules on the same TF forming the transverse CE component and those on adjacent TFs forming the longitudinal CE component; fibers between pillars/globules also link consecutive CE layers together. In the longitudinal component the number of fibrous bridges between the pillars/globules is related to the conspicuousness of the longitudinal component, i.e. Blaps has most, Drosophila almost as many, and rat considerably fewer bridges. We conclude that the central region in rat, Drosophila and Blaps contains the same basic structural unit but the degree of order and concentration of the units differ: a higher density seems to be accompanied by a higher order within the CE.

Animals↗

Expression of a Drosophila heat-shock gene in cells of the yeast Saccharomyces cerevisiae.

A 3.52-kilobase (kb) segment of Drosophila melanogaster DNA carrying the 2.15-kb transcribed sequence for the 70 000-dalton heat-shock protein (hsp70) and 1.14-kb of the 5' flanking sequence was inserted into an autonomously replicating chimeric plasmid and used to transform the yeast Saccharomyces cerevisiae. The Drosophila gene is efficiently transcribed in the transformed cells, yielding a transcript which is 21 nucleotides shorter than the normal Drosophila mRNA at the 5' end. Significant increases in the amount of Drosophila-specific RNA occur when the transformed cells are subjected to heat shock, indicating that the Drosophila gene is inducible in the yeast cells.

Animals↗

Expression of Drosophila hsp 70-CAT hybrid gene in Aedes cells induced by heat shock.

DNA-mediated transfer of a Drosophila hsp 70-CAT hybrid gene into Drosophila S3 cells leads to the appearance of heat shock (37 degrees C)-inducible chloramphenicol acetyltransferase (CAT) activity. When this hybrid gene construction was transfected into cultured Aedes, Plodia, or Manduca cells, only trace levels of heat-inducible CAT activity were observed. Induction could be somewhat improved by using Schneider's Drosophila medium for transfection. In the case of Aedes cells, levels of CAT induction comparable to that seen using Drosophila cells could be achieved by raising the heat-shock temperature to 41 degrees C, a treatment which is lethal to Drosophila.

Acetyltransferases↗

Reconstitution of heterologous and chimeric casein kinase II with recombinant subunits from human and Drosophila: identification of species-specific differences in the beta subunit.

Casein kinase II is composed of two catalytic (alpha) and two regulatory (beta) subunits, the amino acid sequences of the alpha and beta subunits are highly conserved between species. To examine whether heterologous casein kinase II could be formed, recombinant alpha and beta subunits from human and Drosophila were reconstituted from inclusion bodies. Casein kinase II containing either human alpha and Drosophila beta or Drosophila alpha and human beta subunits exhibited enzymatic properties similar to those of the homologous holoenzymes with regard to specific activity, salt optima, and autophosphorylation. However, renaturation and reconstitution of casein kinase II was dependent on the type of beta subunits and the redox conditions, with the Drosophila beta subunits requiring more reduced conditions. Chimeric beta subunits prepared from human and Drosophila cDNA revealed that the N-terminal region was responsible for the requirement for the reduced redox state during renaturation. The N-terminal region also affected solubility and electrophoretic mobility of the beta subunit.

Amino Acid Sequence↗

Evidence for interspecific transfer of the transposable element mariner between Drosophila and Zaprionus.

The transposable element mariner occurs widely in the melanogaster species group of Drosophila. However, in drosophilids outside of the melanogaster species group, sequences showing strong DNA hybridization with mariner are found only in the genus Zaprionus. The mariner sequence obtained from Zaprionus tuberculatus is 97% identical with that from Drosophila mauritiana, a member of the melanogaster species subgroup, whereas a mariner sequence isolated from Drosophila tsacasi is only 92% identical with that from D. mauritiana. Because D. tsacasi is much more closely related to D. mauritiana than is Zaprionus, the presence of mariner in Zaprionus may result from horizontal transfer. In order to confirm lack of a close phylogenetic relationship between the genus Zaprionus and the melanogaster species group, we compared the alcohol dehydrogenase (Adh) sequences among these species. The results show that the coding region of Adh is only 82% identical between Z. tuberculatus and D. mauritiana, as compared with 90% identical between D. tsacasi and D. mauritiana. Furthermore, the mariner gene phylogeny obtained by maximum likelihood and maximum parsimony analyses is discordant with the species phylogeny estimated by using the Adh genes. The only inconsistency in the mariner gene phylogeny is in the placement of the Zaprionus mariner sequence, which clusters with mariner from Drosophila teissieri and Drosophila yakuba in the melanogaster species subgroup. These results strongly suggest horizontal transfer.

Alcohol Dehydrogenase↗

Yeast Srp1, a nuclear protein related to Drosophila and mouse pendulin, is required for normal migration, division, and integrity of nuclei during mitosis.

This paper describes genes from yeast and mouse with significant sequence similarities to a Drosophila gene that encodes the blood cell tumor suppressor pendulin. The protein encoded by the yeast gene, Srp1p, and mouse pendulin share 42% and 51% amino acid identity with Drosophila pendulin, respectively. All three proteins consist of 10.5 degenerate tandem repeats of approximately 42 amino acids each. Similar repeats occur in a superfamily of proteins that includes the Drosophila Armadillo protein. All three proteins contain a consensus sequence for a bipartite nuclear localization signal (NLS) in the N-terminal domain, which is not part of the repeat structure. Confocal microscopic analysis of yeast cells stained with antibodies against Srp1p reveals that this protein is intranuclear throughout the cell cycle. Targeted gene disruption shows that SRP1 is an essential gene. Despite their sequence similarities, Drosophila and mouse pendulin are unable to rescue the lethality of an SRP1 disruption. We demonstrate that yeast cells depleted of Srp1p arrest in mitosis with a G2 content of DNA. Arrested cells display abnormal structures and orientations of the mitotic spindles, aberrant segregation of the chromatin and the nuclei, and threads of chromatin emanating from the bulk of nuclear DNA. This phenotype suggests that Srp1p is required for the normal function of microtubules and the spindle pole bodies, as well as for nuclear integrity. We suggest that Srp1p interacts with multiple components of the cell nucleus that are required for mitosis and discuss its functional similarities to, and differences from Drosophila pendulin.

Amino Acid Sequence↗

GABA transporters in Drosophila melanogaster: molecular cloning, behavior, and physiology.

Molecular cloning of GABA transporter-homologous cDNAs from a Drosophila melanogaster head-specific library was accomplished using a conserved oligomer from a highly conserved domain within the mammalian GABA transporters. Partial DNA sequencing of these cDNAs demonstrated homology with the mammalian transporters, indicating these are ancient, evolutionarily conserved molecules. Although the Drosophila cDNAs had distinct restriction enzyme patterns, they recognized the same locus in Drosophila genomic DNA, suggesting that the multiple isoforms might arise via alternative splicing. Antibodies specific for the mammalian GABA transporters GAT 1, GAT 2 and GAT 3 recognized non-overlapping and developmentally distinct patterns of expression in Drosophila neuronal tissues. Treatment of larval instars with nipecotic acid, a generalized GABA reuptake inhibitor, revealed specific, dose-dependent alterations in behavior consistent with the presence of multiple transporter molecules with differing affinities for this drug. Synaptic current recordings revealed that nipecotic acid treated larvae have an increase in latency jitter of evoked quantal release, resulting in a broader average excitatory junctional current which was manifested in a broader EJP. These results imply that alterations in the development of the CNS occur if GABAergic neurotransmission is potentiated during development. The data suggest that, as in mammals, there are multiple GABA transporters in Drosophila whose expression is differentially regulated.

Amino Acid Sequence↗

The development of a medium supplemented with egg extract for the maintenance of Drosophila cell lines.

A saline extract was prepared from Drosophila eggs. When diluted to a concentration of 1% with Drosophila tissue culture medium, it did not support growth of cells from the Drosophila line D1 during the first few days of subculture as well as medium containing serum. When cells reached a stationary phase, however, the cell density in medium containing extract was greater than in medium containing serum. By altering the concentrations of the extract, and by adding bovine albumin, a medium was obtained in which D1 cells survived initial culturing, and which supported cell growth by day 4 as well as medium plus serum. The initial retardation of growth in medium containing egg extract might be due to the need of the cells to adapt to the new medium. At the present time four Drosophila cell lines have been maintained in this medium for more than 16 passages. Preliminary experiments with primary embryonic Drosophila cells indicate that medium containing 2% extract and bovine albumin retards the differentiation of these cells.

Blood↗

Isolation and structural characterization of Drosophila TDVDHVFLRFamide and FMRFamide-containing neural peptides.

An extract of adult Drosophila melanogaster was separated by gel exclusion, ion exchange, and reversed-phase chromatography. Four peptides, each with an -ArgPheNH2 C-terminal sequence, were identified by radioimmunoassay. The primary sequences were determined by Edman degradation and confirmed by mass spectrometry and sequence-specific radioimmunoassay. Three of the peptides are encoded by Drosophila proFMRFamide: AspProLysGlnAspPheMetArgPheNH2 (DPKQDFMRFamide), ThrProAlaGluAspPheMetArgPheNH2 (TPAEDFMRFamide), and SerAspAsnPheMetArgPheNH2 (SDNFMRFamide). A novel Drosophila peptide ThrAspValAspHisValPheLeuArgPheNH2 (TDVDHVFLRFamide) was also isolated. TDVDHVFLRFamide is structurally related to peptides isolated from chicken, cockroach, locust, and snail; the cockroach, fruitfly, and locust peptides differ only by the N-terminal amino acid residue. Two Drosophila neural genes, dsk and FMRFamide, are known to encode -ArgPheNH2-containing peptides; however, neither encodes TDVDHVFLRFamide, indicating that Drosophila contains another precursor encoding -ArgPheNH2 peptides.

Amino Acid Sequence↗

Shaping of Drosophila alcohol dehydrogenase through evolution: relationship with enzyme functionality.

Drosophilidae is a large, widely distributed family of Diptera including 61 genera, of which Drosophila is the most representative. Drosophila feeding is part of the saprophytic trophic chain, because of its dependence upon decomposing organic matter. Many species have adapted to fermenting fruit feeding or to artificial (man-made) fermentation habitats, such as cellars and breweries. Actually, the efficient exploitation of niches with alcohols is considered one of the reasons for the worldwide success of this genus. Drosophila alcohol dehydrogenase (ADH), a member of the short-chain dehydrogenase/reductase family (SDR), is responsible for the oxidation of alcohols, but its direct involvement in fitness, including alcohol tolerance and utilization, gives rise to much controversy. Thus, it remains unclear whether ADH differentiation through evolution is somehow associated with natural adaptation to new feeding niches, and thus maybe to Drosophila speciation, or if it is a simple reflection of neutral divergence correlated with time separation between species. To build a hypothesis which could shed light on this dilemma, we analyzed the amino acid variability found in the 57 protein ADH sequences reported up to now, identified the taxon-specific residues, and localized them in a three-dimensional ADH model. Our results define three regions whose shaping has been crucial for ADH differentiation and would be compatible with a contribution of ADH to Drosophila speciation.

Adaptation, Biological↗

Strong purifying selection on the Odysseus gene in two clades of sibling species of the Drosophila montium species subgroup.

The Odysseus (OdsH) gene was duplicated from its ancestral neuron-expressed gene, unc-4, and then evolved very rapidly under strong positive Darwinian selection as a speciation gene causing hybrid-male sterility between closely related species of the Drosophila simulans clade. Has OdsH also experienced similar positive selection between Drosophila sibling species other than those of the simulans clade? We cloned and sequenced OdsH and unc-4 from two clades of the Drosophila montium species subgroup, the Drosophila lini and the Drosophila kikkawai clades. The ratios of Ka/Ks for OdsH were remarkably low between sibling species of these two clades, suggesting that OdsH has been subjected to strong purifying selection in these two clades.

Amino Acid Sequence↗