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  • Drosophila  (308)
  • Yeast  (261)
  • Calcification
  • Springer  (626)
  • MDPI Publishing
  • 1990-1994  (396)
  • 1980-1984  (212)
  • 1965-1969  (18)
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  • 1
    Electronic Resource
    Electronic Resource
    Unrewarding experiences and their effect on foraging in the parasitic waspLeptopilina heterotoma (Hymenoptera: Eucoilidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 465-481 
    Details
    ISSN: 1572-8889
    Keywords: host selection ; experience ; learning ; extinction ; reinforcement ; parasitoids ; Drosophila ; Leptopilina heterotoma ; Hymenoptera ; Eucoilidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The host-foraging behavior of female entomophagous parasitoids is commonly modified by positive associative learning. Typically, a rewarding experience (e.g., successful oviposition in a host) increases a female's foraging effort in a host microhabitat of the type associated with that experience. Less well understood are the effects of unrewarding experiences (i.e., unsuccessful foraging). The influence of unrewarding experience on microhabitat choice and residence time within a microhabitat was examined for the eucoilid parasitoid,Leptopilina heterotoma, in laboratory and greenhouse assays. As determined previously, females which oviposited successfully in either of two microhabitat types (fermenting apple or decaying mushroom) strongly preferred to forage subsequently on that microhabitat type. However, failure to find hosts in the formerly rewarding microhabitat caused females to reverse their preference in favor of a novel microhabitat type. The effect, though striking, was transient: within 1–2 h, the original learned preference was nearly fully restored. Similar effects of unrewarding experiences were observed with respect to the length of time spent foraging in a microhabitat. As determined previously, oviposition experience in a particular microhabitat type increased the time spent foraging in a patch of that microhabitat type. However, failure to find hosts in the patch caused the time a wasp spent in the next unoccupied patch of that type to decrease to almost nothing. In addition, there was a tendency for an unrewarding experience on a formerly rewarding microhabitat type to extend the time spent in a patch of a novel type. The function of the observed effects of unrewarding experiences is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025444
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  • 2
    Electronic Resource
    Electronic Resource
    Drosophila do not skew offspring sex ratio as predicted by trivers and willard (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 8 (1994), S. 231-239 
    Details
    ISSN: 1572-8889
    Keywords: Drosophila ; sex ratio ; life history ; optimality model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Based on both previously published literature and results reported here, it appears thatDrosophila melanogaster meet the explicit assumptions of the Trivers and Willard offspring sex allocation model. However, contrary to the model's predictions, offspring sex ratio was not significantly affected when we manipulated factors that influence offspring quality. We suggest that contrary to implicit predictions of offspring sex ratio models,Drosophila may lack the genetic plasticity to readily alter sex ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01988907
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  • 3
    Electronic Resource
    Electronic Resource
    Egg-laying experience and acceptance of parasitized hosts by the parasitoid,Leptopilina heterotoma (Hymenoptera: Eucoilidae) (1994)
    Springer
    Journal of insect behavior 8 (1994), S. 331-342 
    Details
    ISSN: 1572-8889
    Keywords: parasitoid ; superparasitism ; learning ; motivation ; egg load ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of egg-laying experience on the response of females of the eucoilid parasitoid,Leptopilina heterotoma, to parasitized and unparasitizedDrosophila melanogaster host larvae was examined under more controlled conditions than those used in past studies. In laboratory assays, we precisely manipulated both the number of eggs laid by females and the kind of larvae (parasitized versus unparasitized) in which the eggs were laid. We found that the tendency to avoid laying eggs in parasitized hosts depended markedly on whether or not eggs had been laid previously, but depended little on whether those eggs had been laid in parasitized or unparasitized hosts. The observed effect of general egg-laying experience on avoidance of parasitized hosts may reflect responses to either changes in the wasp's internal state (perhaps, changes in egg load) or changes in the wasp's neural representation of the external environment (such as those presumed to occur during learning). In light of these results, we offer a tentative reinterpretation of several earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01989362
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  • 4
    Electronic Resource
    Electronic Resource
    Courtship success and multivariate analysis of sexual selection on morphometric traits inDrosophila buzzatii (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 8 (1994), S. 219-229 
    Details
    ISSN: 1572-8889
    Keywords: Drosophila ; sexual selection gradients ; courtship success
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using wild-reared flies, we examined sexual selection on five phenotypic traits (thorax length, wing length, wing width, head width, and face width) inDrosophila buzzatii, by scoring copulatory status in nine mass mating cages. Only male face width was identified as a direct target of sexual selection in an analysis of selection gradient, while indirect selection was present on all other studied traits, as expected from their correlations with face width. In contrast to males, there was no indication of selection in females. Nor was there evidence of assortative mating. The suggested direct selection on face width seems to take place during licking behavior of the courtship and might be related to courtship feeding. This study suggests that courtship success gives rise to indirect selection on body size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01988906
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  • 5
    Electronic Resource
    Electronic Resource
    Parasitization of embedded and nonembeddedDrosophila melanogaster (Diptera: Drosophilidae) pupae by the parasitoidPachycrepoideus vindemniae (Hymenoptera: Pteromalidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 129-131 
    Details
    ISSN: 1572-8889
    Keywords: Drosophila ; parasitoid wasp ; behavior ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01989833
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of acclimation and rearing conditions on the response of tropical and temperate populations ofDrosophila melanogaster andD. simulans to a temperature gradient (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 279-288 
    Details
    ISSN: 1572-8889
    Keywords: temperature preference ; Drosophila ; acclimation ; compensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of rearing and acclimation on the response of adultDrosophila to temperature were investigated in a gradient.D. melanogaster flies preferred a higher mean temperature and were distributed over a wider range of temperatures thanD. simulans flies. Acclimating adults at different temperatures for a week did not influence the response of either species. Adults reared at 28°C as immatures had a lower mean preference than those reared at cooler temperatures, suggesting that flies compensated for the effects of rearing conditions. Adults from tropical and temperate populations ofD. melanogaster andD. simulans did not differ in the mean temperature they preferred in a gradient, suggesting little genetic divergence for this trait within species. The species differences and environmental responses may be related to changes in optimal physiological conditions for the flies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01989735
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  • 7
    Electronic Resource
    Electronic Resource
    Sensorimotor transformation from light reception to phototactic behavior inDrosophila larvae (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 553-567 
    Details
    ISSN: 1572-8889
    Keywords: review ; Drosophila ; larva ; phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we examine theDrosophila melanogaster larval response to light. We survey the morphology of the larval visual and motor systems in relation to larval locomotory behavior and phototaxis. In addition, this paper proposes a model of sensorimotor transformation and examines the reversal in taxis occurring at theD. melanogaster larval wnadering stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025449
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular evolution of the HSP70 multigene family (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 1-17 
    Details
    ISSN: 1432-1432
    Keywords: HSP70 ; Heat shock ; Evolution ; Phylogeny ; Yeast ; Multigene family ; Subcellular compartmentalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eukaryotic genomes encode multiple 70-kDa heat-shock proteins (HSP70s). The Saccharomyces cerevisiae HSP70 family is comprised of eight members. Here we present the nucleotide sequence of the SSA3 and SSB2 genes, completing the nucleotide sequence data for the yeast HSP70 family. We have analyzed these yeast sequences as well as 29 HSP70s from 24 additional eukaryotic and prokaryotic species. Comparison of the sequences demonstrates the extreme conservation of HSP70s; proteins from the most distantly related species share at least 45% identity and more than one-sixth of the amino acids are identical in the aligned region (567 amino acids) among all proteins analyzed. Phylogenetic trees constructed by two independent methods indicate that ancient molecular and cellular events have given rise to at least four monophyletic groups of eukaryotic HSP70 proteins. Each group of evolutionarily similar HSP70s shares a common intracellular localization and is presumed to be comprised of functional homologues; these include heat-shock proteins of the cytoplasm, endoplasmic reticulum, mitochondria, and chloroplasts. HSP70s localized in mitochondria and plastids are most similar to the DnaK HSP70 homologues in purple bacteria and cyanobacteria, respectively, which is consistent with the proposed prokaryotic origin of these organelles. The analyses indicate that the major eukaryotic HSP70 groups arose prior to the divergence of the earliest eukaryotes, roughly 2 billion years ago. In some cases, as exemplified by the SSA genes encoding the cytoplasmic HSP70s of S. cerevisiae, more recent duplication events have given rise to subfamilies within the major groups. The S. cerevisiae SSB proteins comprise a unique subfamily not identified in other species to date. This subfamily appears to have resulted from an ancient gene duplication that occurred at approximately the same time as the origin of the major eukaryotic HSP70 groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175490
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  • 9
    Electronic Resource
    Electronic Resource
    Phylogeny of the Drosophila obscura species group deduced from mitochondrial DNA sequences (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 478-488 
    Details
    ISSN: 1432-1432
    Keywords: Mitochondrial DNA ; Nucleotide sequences ; Drosophila ; Rapid phyletic radiation ; Molecular phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Approximately 2 kb corresponding to different regions of the mtDNA of 14 different species of the obscura group of Drosophila have been sequenced. In spite of the uncertainties arising in the phylogenetic reconstruction due to a restrictive selection toward a high mtDNA A+T content, all the phylogenetic analysis carried out clearly indicate that the obscura group is formed by, at least, four well-defined lineages that would have appeared as the consequence of a rapid phyletic radiation. Two of the lineages correspond to monophyletic subgroups (i.e., afftnis and pseudoobscura), whereas the obscura subgroup remains heterogeneous assemblage that could be reasonably subdivided into at least two complexes (i.e., subobscura and obscura).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173417
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  • 10
    Electronic Resource
    Electronic Resource
    Aspects of nonrandom turnover involved in the concerted evolution of intergenic spacers within the ribosomal DNA of Drosophila melanogaster (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 151-159 
    Details
    ISSN: 1432-1432
    Keywords: Concerted evolution ; Molecular drive ; Drosophila ; rDNA spacers ; PCR length polymorphism ; MVR-PCR mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polymerase chain reaction (PCR)-amplified, sequenced, and digitally typed intergenic spacers (IGSs) of the ribosomal (r)DNA in D. melanogaster reveal unexpected features of the mechanisms of turnover involved with the concerted evolution of the gene family. Characterization of the structure of three isolated IGS length variants reveals breakage “hot spots” within the 330-base-pair (bp) subrepeat array found in the spacers. Internal mapping of variant repeats within the 240-bp subrepeat array using a novel digital DNA typing procedure (minisatellite variant repeat [MVR]-PCR) shows an unexpected pattern of clustering of variant repeats. Each 240-bp subrepeat array consists of essentially two halves with the repeats in each half identified by specific mutations. This bipartite structure, observed in a cloned IGS unit, in the majority of genomic DNA of laboratory and wild flies and in PCR-amplified products, has been widely homogenized yet is not predicted by a model of unequal crossing over with randomly placed recombination breakpoints. Furthermore, wild populations contain large numbers of length variants in contrast to uniformly shared length variants in laboratory stocks. High numbers of length variants coupled to the observation of a homogenized bipartite structure of the 240-bp subrepeat array suggest that the unit of turnover and homogenization is smaller than the IGS and might involve gene conversion. The use of PCR for the structural analysis of members of the rDNA gene family coupled to digital DNA typing provides powerful new inroads into the mechanisms of DNA turnover affecting the course of molecular evolution in this family.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163804
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  • 11
    Electronic Resource
    Electronic Resource
    Degenerating gypsy retrotransposons in a male fertility gene on the Y chromosome of Drosophila hydei (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 452-465 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; Y chromosome ; Male fertility genes ; Lampbrush loops ; Germ line ; Transposable elements ; Gypsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the evolution of the Y chromosome of Drosophila hydei, retrotransposons became incorporated into the lampbrush loop pairs formed by several of the male fertility genes on this chromosome. Although insertions of retrotransposons are involved in many spontaneous mutations, they do not affect the functions of these genes. We have sequenced gypsy elements that are expressed as constituents of male fertility gene Q in the lampbrush loop pair Nooses. We find that these gypsy elements are all truncated and specifically lost those sequences that may interfere with the continuity of lampbrush loop transcription. Only defective coding regions are found within the loop. Gypsy is not transcribed in loops of many other Drosophila species harboring the family. These results suggest that any contribution of gypsy to the function of male fertility gene Q does not depend on a conserved DNA sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173414
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  • 12
    Electronic Resource
    Electronic Resource
    Visual control of wing beat frequency in Drosophila (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 587-596 
    Details
    ISSN: 1432-1351
    Keywords: Wing beat frequency ; Optomotor responses ; Landing response ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The present study shows that the wing beat frequency of Drosophila is visually controlled and modulated in response to different optomotor stimuli. Whereas rotational large field stimuli do not appear to modulate wing beat frequency, single rotating vertical stripes increase or decrease wing beat frequency when moving back-to-front or front-to-back, respectively. Maximal modulations occur at lateral stripe positions. Expansion stimuli eliciting the landing response cause a marked increase in wing beat frequency. Parameters of this frequency response depend in a graded fashion on certain stimulus properties, and the frequency response co-habituates with the landing response. Several results indicate that the frequency response is an integral component of the landing response, although it can also occur when the characteristic front leg extension is not observed. The complex spatial input integration underlying the frequency response and other motor components of the landing response cannot easily be explained by a system of large field integration units, but might indicate the existence of local expansion detectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199480
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  • 13
    Electronic Resource
    Electronic Resource
    Improved stability of Drosophila larval neuromuscular preparations in haemolymph-like physiological solutions (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 179-191 
    Details
    ISSN: 1432-1351
    Keywords: Drosophila ; Neuromuscular ; Haemolymph ; Membrane potential ; Synaptic potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Neuromuscular preparations from third instar larvae of Drosophila are not well-maintained in commonly used physiological solutions: vacuoles form in the muscle fibers, and membrane potential declines. These problems may result from the Na∶K ratio and total divalent cation content of these physiological solutions being quite different from those of haemolymph. Accordingly haemolymph-like solutions, based upon ion measurements of major cations, were developed and tested. Haemolymph-like solutions maintained the membrane potential at a relatively constant level, and prolonged the physiological life of the preparations. Synaptic transmission was well-maintained in haemolymph-like solutions, but the excitatory synaptic potentials had a slower time course and summated more effectively with repetitive stimulation, than in standard Drosophila solutions. Voltage-clamp experiments suggest that these effects are linked to more pronounced activation of muscle fiber membrane conductances in standard solutions, rather than to differences in passive muscle membrane properties or changes in postsynaptic receptor channel kinetics. Calcium dependence of transmitter release was steep in both standard and haemolymph-like solutions, but higher external calcium concentrations were required for a given level of release in haemolymph-like solutions. Thus, haemolymph-like solutions allow for prolonged, stable recording of synaptic transmission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215114
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  • 14
    Electronic Resource
    Electronic Resource
    Altered mechanoreceptor response in Drosophila bang-sensitive mutants (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 267-278 
    Details
    ISSN: 1432-1351
    Keywords: Drosophila ; Bang sensitivity ; Mechanotransduction ; Adaptation ; Sensory coding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Bang-sensitive mutants of Drosophila melano gaster (bas 1, bssMW1, eas2, tko25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas 1 bssMW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas 1 and bss MW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors. Although this defect does not provide a straightforward explanation for bang sensitivity, the altered cellular process may lead to bang sensitivity through its action in different parts of the nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192986
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  • 15
    Electronic Resource
    Electronic Resource
    Speciation in the Artemia genus: Mitochondrial DNA analysis of bisexual and parthenogenetic brine shrimps (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 156-168 
    Details
    ISSN: 1432-1432
    Keywords: Artemia franciscana ; Artemia salina ; Artemia parthenogenetica ; Mitochondrial DNA evolution ; Cytochrome c oxidase I ; Cytochrome b ; Drosophila ; Arthropods ; Parthenogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From the cloned mitochondrial DNAs (mtDNAs) isolated from two bisexual species, one Mediterranean, Artemia salina, and one American, Artemia franciscana, and two parthenogenetic (diploid and tetraploid) strains of Artemia parthenogenetica collected in Spain, physical maps have been constructed and compared. They are extremely different among themselves, much more than the differences between Drosophila melanogaster and D. yakuba and in the same range of different mammalian species such as mouse/rat or man/cow. The nucleotide sequences of two regions of mtDNA encoding parts of the cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) genes have been determined in the two bisexual species and the two parthenogenetic strains. Comparisons of these sequences have revealed a high degree of divergence at the nucleotide level, averaging more than 15%, in agreement with the differences found in the physical maps. The majority of the nucleotide changes are silent and there is a strong bias toward transitions, with the C↔T substitutions being highly predominant. The evolutionary distance between the two Artemia parthenogenetica is high and there is no clear relationship with any of the bisexual species, including the one present nowadays in Spain. Using a combination of molecular (mtDNA) and morphological markers it is possible to conclude that all of these Artemia isolates should be actually considered as belonging to different species, even the two Artemia parthenogenetica diploidica and tetraploidica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166162
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  • 16
    Electronic Resource
    Electronic Resource
    Interspecific sequence comparison of the muscle-myosin heavy-chain genes from Drosophila hydei and Drosophila melanogaster (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 357-368 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; Muscle-myosin heavy-chain gene ; Alternative exons ; Synonymous substitutions ; Amino acid substitutions ; Evolution ; Testis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The muscle-myosin heavy-chain (mMHC) gene of Drosophila hydei has been sequenced completely (size 23.3 kb). The sequence comparison with the D. melanogaster mMHC gene revealed that the exonintron pattern is identical. The protein coding regions show a high degree of conservation (97%). The alternatively spliced exons (3a-b, 7a-d, 9a-c, 11a-e, and 15a-b) display more variations in the number of nonsynonymous and synonymous substitutions than the common exons (2, 4, 5, 6, 8, 10, 12, 13, 14, 16, 17, and 19). The base composition at synonymous sites of fourfold degenerate codons (third position) is not biased in the alternative exons. In the common exons there exists a bias for C and against A. These findings imply that the alternative exons of the Drosophila mMHC gene evolve at a different, in several cases higher, rate than the common ones. The 5′ splice junctions and 5′ and 3′ untranslated regions show a high level of similarity, indicating a functional constraint on these sequences. The intron regions vary considerably in length within one species, but the corresponding introns are very similar in length between the two species and all contain stretches of sequence similarity. A particular example is the first intron, which contains multiple regions of similarity. In the conserved regions of intron 12 (head-tail border) sequences were found which have the potential to direct another smaller mMHC transcript.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160268
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  • 17
    Electronic Resource
    Electronic Resource
    Nucleotide sequence of the genomic region encompassing Adh and Adh-Dup genes of D. lebanonensis (Scaptodrosophila): Gene expression and evolutionary relationships (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 455-467 
    Details
    ISSN: 1432-1432
    Keywords: Alcohol dehydrogenase ; Drosophila ; Drosophila lebanonensis ; Gene expression ; Codon usage ; Phylogenetic relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The region of the genome of D. lebanonensis that contains the Adh gene and the downstream Adh-dup gene was sequenced. The structure of the two genes is the same as has been described for D. melanogaster. Adh has two promoters and Adh-dup has only one putative promoter. The levels of expression of the two genes in this species are dramatically different. Hybridizing the same Northern blots with a specific probe for Adh-dup, we did not find transcripts for this gene in D. lebanonensis. The level of Adh distal transcript in adults of D. lebanonensis is five times greater than that of D. melanogaster adults. The maximum levels of proximal transcript are attained at different larval stages in the two species, being three times higher in D. melanogaster late-second-instar larvae than in D. lebanonensis first-instar larvae. The level of Adh transcripts allowed us to determine distal and proximal initiation transcription sites, the position of the first intron, the use of two polyadenylation signals, and the heterogeneity of polyadenylation sites. Temporal and spatial expression profiles of the Adh gene of D. lebanonensis show qualitative differences compared with D. melanogaster. Adh and Adh-dup evolve differently as shown by the synonymous and nonsynonymous substitution rates for the coding region of both genes when compared across two species of the melanogaster group, two of the obscura group of the subgenus Sophophora and D. lebanonensis of the victoria group of the subgenus Scaptodrsophila. Synonymous rates for Adh are approximately half those for Adh-dup, while nonsynonymous rates for Adh are generally higher than those for Adh-dup. Adh shows 76.8% identities at the protein level and 70.2% identities at the nucleotide level while Adh-dup shows 83.7% identities at the protein level and 67.5% identities at the nucleotide level. Codon usage for Adh-dup is shown to be less biased than for Adh, which could explain the higher synonymous rates and the generally lower nonsynonymous substitution rates in Adh-dup compared with Adh. Phylogenetic trees reconstructed by distance matrix and parsimony methods show that Sophophora and Scaptodrosophila subgenera diverged shortly after the separation from the Drosophila subgenus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178845
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  • 18
    Electronic Resource
    Electronic Resource
    Drive-selection equilibrium: Homopolymer evolution in the Drosophila gene mastermind (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 637-641 
    Details
    ISSN: 1432-1432
    Keywords: mastermind ; Drosophila ; Homopolymer ; Repeat length variation ; Molecular drive ; Natural selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interspecific sequence comparison of the highly repetitive Drosophila gene mastermind (mam) reveals extensive length variation in homopolymer domains. The length variation in homopolymers is due to nucleotide misalignment in the underlying triplet repeats, which can lead to slippage mutations during DNA replication or repair. In mam, the length variation in repetitive regions appears to be balanced by natural selection acting to maintain the distance between two highly conserved charge clusters. Here we report a statistical test of the null hypothesis that the similarity in the amino acid distance between the charge clusters of each species arose by chance. The results suggest that at mam there is a juxtaposition of length variability due to molecular drive and length conservation maintained by natural selection. The analysis of mam allows the extension of current theories of drive-selection interaction to encompass homopolymers. Our model of drive-selection equilibrium suggests that the physical flexibility, length variability, and abundance of homopolymer domains provide an important source of genetic variation for natural populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175884
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  • 19
    Electronic Resource
    Electronic Resource
    Olfactory physiology in the Drosophila maxillary palp requires the visual system gene rdgB (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 687-693 
    Details
    ISSN: 1432-1351
    Keywords: rdgB ; Maxillary palp ; Drosophila ; Electrophysiology ; Olfaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We describe the kinetics of odorant response in the maxillary palp of Drosophila, and show that the rate of recovery from odorant stimulation is affected by mutation of the rdgB (retinal degeneration B) gene. We use immunocytochemistry to confirm that the rdgB gene product is expressed in the maxillary palp. rdgB has recently been shown to encode a protein with Ca2+-binding sites and sequence similarity to rat brain phosphatidylinositol transfer protein; it is located near the rhabdomeric membranes in photoreceptor cells, where it has been suggested to play a role in membrane transport. The delay in recovery kinetics that we observe in olfactory tissue may reflect a defect in membrane restoration at the conclusion of the olfactory transduction cascade. The use of common molecules in the physiology of two olfactory organs, and in both visual and olfactory physiology, is discussed.
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    URL: http://dx.doi.org/10.1007/BF00191841
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    Quantifying relative importance of maxillary palp information on the olfactory behavior of Drosophila melanogaster (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 761-766 
    Details
    ISSN: 1432-1351
    Keywords: Olfactory behavior ; Antenna ; Maxillary palp ; Olfaction ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Maxillary palps have been proposed as secondary olfactory organs, after the antennae, in Drosophila melanogaster. Our study tries to establish the quantitative importance of both organs as olfactory information mediators. Dose-response curves for three odorants: ethyl acetate, propionaldehyde and benzaldehyde were carried out for comparing olfaction in either complete animals or flies surgically deprived of antennae. Antennaless flies tested in our behavioral assay showed indifferent, attractant and repellent responses depending on concentration, similarly as normal flies do. However, they clearly displayed less sensitivity than normal flies. The range of concentrations they were able to perceive was correlated to antennal sensitivity approximately by a factor 1∶10 for ethyl acetate and benzaldehyde, and between 1∶10 and 1∶100 at high concentrations of propionaldehyde. A complementary experiment was performed to test changes in olfactory behavior produced by removing maxillary palps in the presence of antennae. At high concentrations of odorant, responses to ethyl acetate and propionaldehyde experienced small changes when both palps were removed. Results are compatible with a summation model of all olfactory information reaching the brain either through antennae or palps.
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    URL: http://dx.doi.org/10.1007/BF00191847
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    BrdU incorporation reveals DNA replication in non dividing glial cells in the larval abdominal CNS ofDrosophila (1994)
    Springer
    Development genes and evolution 204 (1994), S. 54-61 
    Details
    ISSN: 1432-041X
    Keywords: CNS ; Glia ; Drosophila ; BrdU
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glial cells are of significant importance for central nervous system development and function. In insects, knowledge of the types and development of CNS glia is rather low. This is especially true for postembryonic glial development. Using bromodeoxyuridine incorporation and enhancer trap lines we identified a reproducible spatial and temporal pattern of DNA replicating cells in the abdominal larval CNS (A3-7 neuromeres) ofDrosophila melanogaster. These cells correspond to embryonically established glial cells in that region. Except for a specific subfraction, these cells apparently do not divide during larval life. Similar patterns were found in two otherDrosophila species,D. virilis andD. hydei.
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    Drosophila glial development is regulated by genes involved in the control of neuronal cell fate (1994)
    Springer
    Development genes and evolution 204 (1994), S. 118-125 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; glia ; Proneural ; Neurogenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Drosophila proneural genes specify neuronal determination among cells within the ectoderm. Here we address the question of whether proneural genes also affect the specification of glia, the most abundant cell type in the nervous system. We provide evidence that the proneural gene daughterless is essential for the formation of two major classes of PNS glia. In contrast, the proneural genes in the achaete-scute complex have no detectable effect on the specification and differentiation of these PNS glia and certain CNS glia. We also show that, as with neuronal development, glial determination is restricted by the neurogenic genes neuralized, Delta, and the genes of the Enhancer of split complex. Finally, we demonstrate that prospero, a gene involved in neuronal differentiation, also affects glial development. These results demonstrate extensive overlap in the genetic control of glial and neuronal development.
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    URL: http://dx.doi.org/10.1007/BF00361106
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    Embryonic origin and differentiation of the Drosophila heart (1994)
    Springer
    Development genes and evolution 203 (1994), S. 266-280 
    Details
    ISSN: 1432-041X
    Keywords: Heart ; Drosophila ; Morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have followed the normal development of the different cell types associated with the Drosophila dorsal vessel, i.e. cardioblasts, pericardial cells, alary muscles, lymph gland and ring gland, by using several tissue-specific markers and transmission electron microscopy. Precursors of pericardial cells and cardioblasts split as two longitudinal rows of cells from the lateral mesoderm of segments T2-A7 (“cardiogenic region”) during stage 12. The lymph gland and dorsal part of the ring gland (corpus allatum) originate from clusters of lateral mesodermal cells located in T3 and T1/dorsal ridge, respectively. Cardioblast precursors are strictly segmentally organized; each of T2-A6 gives rise to six cardioblasts. While moving dorsally during the stages leading up to dorsal closure, cardioblast precursors become flattened, polarized cells aligned in a regular longitudinal row. At dorsal closure, the leading edges of the cardioblast precursors meet their contralateral counterparts. The lumen of the dorsal vessel is formed when the trailing edges of the cardioblast precursors of either side bend around and contact each other. The amnioserosa invaginates during dorsal closure and is transiently attached to the cardioblasts; however, it does not contribute to the cells associated with the dorsal vessel and degenerates during late embryogenesis. We describe ultrastructural characteristics of cardioblast differentiation and discuss similarities between cardioblast development and capillary differentiation in vertebrates.
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    URL: http://dx.doi.org/10.1007/BF00360522
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    Novel tissue units of regional differentiation in the gut epithelium of Drosopbila, as revealed by P-element-mediated detection of enhancer (1994)
    Springer
    Development genes and evolution 203 (1994), S. 243-249 
    Details
    ISSN: 1432-041X
    Keywords: Gut ; Drosophila ; Compartment ; Regional differentiation ; P-element enhancer detectors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We analysed spatial patterns of expression of a lacZ reporter gene in the gut of Drosophila larvae that had been transformed with a P-element-lacZ vector to identify regional differences in gene expression. lacZ-positive epithelial cells formed distinct domains with discrete transverse and longitudinal boundaries along the gut tube. Boundaries were often found at sites at which morphological boundaries were not obvious. The gut epithelium was subdivided into 36 compartments by the boundaries. We refer to these novel compartments as “tissue compartments”. The lacZ-positive domain of each strain appeared as a single tissue compartment or as a combination of several tissue compartments. The tissue compartment is considered to be a unit of regional differentiation. The spatial organization of the tissue compartments may represent the “floor plan”, determined by genes that control the regional differentiation of this nonsegmental organ.
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    URL: http://dx.doi.org/10.1007/BF00360519
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    The function of the proneural genes achaete and scute in the spatio-temporal patterning of the adult labellar bristles of Drosophila melanogaster (1994)
    Springer
    Development genes and evolution 203 (1994), S. 340-350 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; achaete ; scute ; Taste bristles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sensory precursors for labellar taste bristles develop from the labial disc in three distinct temporal waves occurring at 0 h, 8 h and 14 h of pupal development. In each temporal wave, transcripts for the achaete (ac) and scute (sc) genes are expressed in overlapping patterns in cells of the disc epithelium prior to the appearance of sensory mother cells (SMCs). No bristles form in mutant flies in which the ac and sc genes are absent. When the sc gene alone is deleted, a set of seven bristles fail to form. Pulses of ubiquitous sc + expression during pupal development, in a strain mutant for both ac and sc, can result in flies with all the labellar bristles at their correct positions. sc + pulses at times corresponding to the initiation of each of the waves of SMC specification in the disc was sufficient to restore bristle pattern. Bristles were not induced at ectopic positions and times as a result of the ubiquitous expression of sc +. These results suggest that the proneural genes ac and sc do not themselves set the pattern of the labellar bristles. Instead, they are required for the elaboration of the pattern set by other gene products. We also show that the formation and positioning of the later waves of bristles can take place even in the absence of bristles normally specified earlier.
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    URL: http://dx.doi.org/10.1007/BF00457805
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    Fate-mapping in the procephalic region of the embryonic Drosopbila head (1994)
    Springer
    Development genes and evolution 203 (1994), S. 367-373 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Embryogenesis ; Morphogenetic movements ; Brain ; HRP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using intracellular horseradish peroxidase injection we traced the developmental fate of early gastrula cells of the procephalic region in the stage 16/17 embryo. Morphogenetic movements in the developing brain are described in three dimensions. The results are related to head segmentation, and an early gastrula fate map of pregnathal head segments is proposed.
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    URL: http://dx.doi.org/10.1007/BF00188684
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    BrdU incorporation reveals DNA replication in non dividing glial cells in the larval abdominal CNS of Drosophila (1994)
    Springer
    Development genes and evolution 204 (1994), S. 54-61 
    Details
    ISSN: 1432-041X
    Keywords: CNS ; Glia ; Drosophila ; BrdU
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glial cells are of significant importance for central nervous system development and function. In insects, knowledge of the types and development of CNS glia is rather low. This is especially true for postembryonic glial development. Using bromodeoxyuridine incorporation and enhancer trap lines we identified a reproducible spatial and temporal pattern of DNA replicating cells in the abdominal larval CNS (A3-7 neuromeres) of Drosophila melanogaster. These cells correspond to embryonically established glial cells in that region. Except for a specific subfraction, these cells apparently do not divide during larval life. Similar patterns were found in two other Drosophila species, D. virilis and D. hydei.
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    URL: http://dx.doi.org/10.1007/BF00189068
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    Effect of ultrafilterable fragments from chondroitinase and protease-treated aggrecan on calcium phosphate precipitation in liposomal suspensions (1994)
    Springer
    Calcified tissue international 55 (1994), S. 176-179 
    Details
    ISSN: 1432-0827
    Keywords: Calcification ; Calcium phosphates ; Liposomes ; Mineralization ; Proteoglycans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract A liposome-centered endogenous precipitation method was used to investigate the effect of ultrafilterable fragments from the enzymatic digestion of rat chondrosarcoma aggrecan on the formation of insoluble calcium phosphate salts in buffered solutions at pH 7.4 and 22°C. Unlike the intact aggrecan and its major chondroitin sulfate and core protein components, disaccharide units from chondroitinase degradation of the aggrecan and small (〈3kg/mol molecular weight) fragments from protease digestion of the core structure were found to be only weakly inhibitory toward mineral formation. Corresponding reductions in Ca2+-binding indicate that these fragments were unable to adsorb to active sites on the apatite surface for long enough periods to significantly hinder crystal growth. The data suggest that controlled enzymatic breakdown of aggrecan may be one possible mechanism by which the calcification of growth plate cartilage is allowed to advance in vivo.
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    Stimulation of human osteoblast differentiation and function by ipriflavone and its metabolites (1994)
    Springer
    Calcified tissue international 55 (1994), S. 356-362 
    Details
    ISSN: 1432-0827
    Keywords: Osteoblasts ; Matrix proteins ; Collagen ; Cell differentiation ; Calcification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Ipriflavone (IP), an isoflavone derivative, has been shown to interfere with bone remodeling by inhibiting bone resorption and perhaps stimulating bone formation. In this study, we have analyzed the effect of IP and its metabolites on the differentiation and function of human osteoblastic cells. Bone marrow stromal osteoprogenitor cells (BMC) and trabecular bone osteoblasts (HOB) were isolated from human donors. The former can be induced to differentiate by treatment with dexamethasone, whereas the latter represent a more differentiated osteoblast. Incubation of BMC with metabolite III (10-5 M) for 1 week induced modest but significant changes of alkaline phosphatase activity. Though both IP and metabolite III stimulated the expression of bone sialoprotein mRNA, a protein involved in cell attachment to the matrix, only metabolite III increased the steady-state level of decorin mRNA, a collagen fibrillogenesis-regulating proteoglycan. Metabolites III and V, but not the other isoflavones, increased the expression of type I collagen mRNA in HOB, whereas no detectable changes were observed in BMC cells with any of the experimental compounds. In HOB, an increased abundance of osteopontin and bone sialoprotein mRNA were also obtained after 1-week treatment with IP or metabolite V. No appreciable effects of IP or its metabolites were seen on osteocalcin expression and synthesis by either cell type. Finally, IP consistently increased the amount of 45Ca incorporated into the cell layer by BMC, and stimulated mineralization of both BMC and HOB, assessed by von Kossa staining. Thus, IP and its metabolites regulate the differentiation and biosynthetic properties of human bone-forming cells by enhancing the expression of some important matrix proteins and facilitating the mineralization process.
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    URL: http://dx.doi.org/10.1007/BF00299315
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    Heat shock changes the response of the pso3 mutant of Saccharomyces cerevisiae to 8-methoxypsoralen photoaddition (1994)
    Springer
    Current genetics 26 (1994), S. 100-104 
    Details
    ISSN: 1432-0983
    Keywords: DNA repair ; Heat shock ; Hyperthermia ; Mutagenesis ; pso3-1 mutant ; Psoralen ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A putative tolerance, induced by heat shock (HS), to the lethal and mutagenic effects of 8-methoxypsoralen (8-MOP) photoaddition and hyperthermia was analyzed in Saccharomyces cerevisiae using the wild-type strain N123 and the isogenic DNA repair-deficient mutant pso3-1. In wild-type cells, the HS (38°C for 1 h) did not modify either the survival or the mutation frequency observed after 8-MOP photoaddition, even though it conferred protection against the lethal effect of hyperthermia (50°C). In the pso3-1 mutant, HS induced an increase of the survival, and a decrease of the mutation frequency, after 8-MOP photoaddition and it also protected against the lethal effect of hyperthermia. The responses induced by HS were specific for 8-MOP photoaddition, since they were not observed after 254 nm ultraviolet-light damage. These results indicate that the protection conferred by HS depends of the type of lesion, and operates through the induction of different repair processes. In the pso3-1 mutant, HS could channel the repair intermediates to and error-free repair pathway.
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    URL: http://dx.doi.org/10.1007/BF00313795
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    Energy-dependent mitochondrial mutagenicity of antibacterial ofloxacin and its recombinogenic activity in yeast (1994)
    Springer
    Current genetics 26 (1994), S. 281-284 
    Details
    ISSN: 1432-0983
    Keywords: Ofloxacin ; Mitochondria ; Mutation ; Recombination ; Topoisomerase ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ofloxacin, a specific inhibitor of bacterial topoisomerase II, is known to inhibit the growth of yeast cells and to induce rho − mutants in the yeast S. cerevisiae. The frequency of ofloxacin-induced petite mutants under non-growth conditions was found to be strongly diminished when the cells were depleted in intramitochondrial ATP. Under optimal conditions of mitochondrial mutagenesis the drug induced mitotic recombination and reverse mutation in diploid strains but failed to cure either killer plasmids or the 2 μm DNA of dividing cells. The sensitivity to ofloxacin of the strains deficient in the DNA strandbreak repair pathway (rad52) was significantly higher then that of the wild-type strains and of the mutants deficient in excision or mutagenic DNA repair. The results are compatible with the idea that the cytotoxic and genetic activity of ofloxacin in yeast probably results from the inhibited DNA ligation function of topoisomerase II creating DNA breaks that are reparable through the recombination repair pathway.
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    The byp1-3 allele of the Saccharomyces cerevisiae GGS1/TPS1 gene and its multi-copy suppressor tRNAGLN (CAG): Ggs1/Tps1 protein levels restraining growth on fermentable sugars and trehalose accumulation (1994)
    Springer
    Current genetics 26 (1994), S. 295-301 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Trehalose synthase ; GGS1/TPS1 gene ; Glycolysis ; Fermentable sugars ; Suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Byp1-3 is an amber nonsense allele of the Sacchromyces cerevisiae GGS1/TPS1 gene which encodes the small subunit of the trehalose synthase complex. Mutations in this gene confer an inability to grow on glucose or fructose but the phenotype of byp1-3 mutants is leaky in a strain-dependent manner. Overexpression of the isolated byp1-3 allele suppressed the growth defect of a ggs1/tps1Δ mutant. Expression of an in-vitro-generated mutant allele of GGS1/TPS1 that lacks all the coding sequences downstream from the byp1-3 mutation led to the production of a shortened protein that did not complement the ggs1/tps1Δ mutant. We have isolated, as an allele-specific multi-copy suppressor of the growth defect of the byp1-3 mutant on fructose, the gene for tRNAGLN (CAG). Thus the leaky phenotype of byp1-3 mutants is due to a low level of read through of the internal nonsense codon by tRNAGLN (CAG). Using overexpression of the isolated byp1-3 allele, as well as of the tRNAGLN (CAG) gene, we were able to demonstrate that as little as about 10% of the normal Ggs1/Tps1 protein level is sufficient for slow growth on fructose. We also show a correlation between the level of Ggs1/Tps1, the ability to accumulate trehalose in stationary phase and the ability to grow on fermentable sugars. Sequence analysis of the cloned tRNAGLN (CAG) gene showed that it is located 700 bp upstream of URA10. However, we found considerable differences to the reported sequence of URA10, in particular in the non-coding region.
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    The yeast protein Mrs6p, a homologue of the rabGDI and human choroideraemia proteins, affects cytoplasmic and mitochondrial functions (1994)
    Springer
    Current genetics 26 (1994), S. 308-314 
    Details
    ISSN: 1432-0983
    Keywords: Small G proteins ; YPT1 ; Yeast ; abGDI ; Mitochondria ; MRS2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract MRS6 is a newly-identified gene in the yeast Saccharomyces cerevisiae. Its product Mrs6p shows significant homology to the mammalian GDP dissociation inhibitor (GDI) of Rab/Ypt-type small G proteins and to the human choroideraemia protein (CHM), the component A of Rab-specific GGTase II. The interaction of Mrs6p with G proteins is indicated by our observation that the MRS6 gene suppresses the effect of a temperature-sensitive ypt1 mutation. Disruption of the MRS6 gene is lethal to haploid yeast cells. This is consistent with the notion that Mrs6p is interacting with Rab/Ypt-type small G proteins, which are known to have essential functions in vesicular transport. Unexpeciedly, the MRS6 gene product also affects mitochondrial functions as revealed by the facts that highcopy numbers of MRS6 (1) suppress the pet - phenotype of mrs2-1 mutant strains and (2) cause a weak pet - phenotype in wild-type strains. We conclude from these results that the MRS6 gene product has a vital function in connection with Rab/Ypt-type proteins in the cytoplasm and, in addition, affects mitochondrial functions.
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    LYC1 is the structural gene for lysine N-6-acetyl transferase in yeast (1994)
    Springer
    Current genetics 25 (1994), S. 24-29 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Yarrowia lipolytica ; Lysine acetyl transferase ; Lysine catabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the yeastYarrowia lipolytica, theLYC1 locus controls the first step of the lysine degradation pathway which is catalyzed by lysine N-6-acetyl transferase (LAT). This gene was cloned by complementation of thelyc1-100 mutation. Its position in the cloned insert was determined by conversion mapping and by complementation. TheLYC1 gene encodes a 391 amino-acid polypeptide which has no homolog in protein databases. The required upstream region extends over 960 bp. When placed under the control of theGAL10 promoter inSaccharomyces cerevisiae, LYC1 drives the expression of lysine acetyl transferase activity, thus providing strong evidence that it is the structural gene encoding this enzyme.
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    Basidiomycetousras cDNA functionally replaces its homolog genes in yeast (1994)
    Springer
    Current genetics 25 (1994), S. 30-33 
    Details
    ISSN: 1432-0983
    Keywords: Plasmid exchange ; ras/Ras gene ; Basidiomycete ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was shown by a plasmid exchange procedure that the Ras-encoding cDNA of the basidiomyceteLentinus edodes (namedLeras cDNA) can functionally replace its homolog genes (ScRAS1 andScRAS2) in the yeastSaccharomyces cerevisiae to maintain the viability of an yeast strain containing genetic disruptions of bothRAS genes. The strain replaced by aLeras−cDNA-carrying plasmid, however, grew slower than the strains replaced by aScRAS1− or aScRAS2−carrying plasmid. The intracellular level of cAMP in the strain harboring theLeras−cDNA-carrying plasmid was clearly higher than that of a parental strain which maintains a plasmid carrying theS. cerevisiae cAMP-dependent protein kinase catalytic subunit C1 gene,TPK1, but was lower than that in a strain harboring anScRAS2−carrying plasmid. These results suggest that theLeras cDNA can complement theras1 − ras2− mutation of yeast by virture of the stimulation of adenylate cyclase activity, although the complementation is not as efficient as that obtained by expressing theScRAS2 gene.
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    Analysis of the role of the NUC1 endo/exonuclease in yeast mitochondrial DNA recombination (1994)
    Springer
    Current genetics 25 (1994), S. 142-149 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; DNA recombination ; 5′ exonuclease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial DNA recombination was reduced in an yeast mutant lacking the NUC1 endo/exonuclease. Between linked markers in either the ω or cob region the frequency of recombination decreased nearly 50% compared to wild-type. Gene conversion frequencies in the var1 gene and in the ω region were also lower in the mutant strain. In particular, the gradient of gene conversion at ω was most affected by the absence of the NUC1 nuclease. In crosses between nuclease-deficient and wild-type strains, gene conversion frequencies at ω were reduced only when the ω+ allele was contributed to the zygote by the nuclease-deficient parent. We propose that the 5′ exonuclease activity of the NUC1 nuclease functions during recombination to enlarge heteroduplex tracts following a double-strand break in DNA. In crosses between nuclease-deficient and wild-type strains, the anisotropy in gene conversion frequencies at ω is hypothesized to be due to the slow mixing of parental motochondrial membranes as they fuse in the zygote.
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    Distinct upstream activation regions for glucose-repressed and derepressed expression of the yeast citrate synthase gene CIT1 (1994)
    Springer
    Current genetics 25 (1994), S. 185-195 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Citrate synthase ; Transcriptional regulation ; HAP2,3,4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast CIT1 (mitochondrial citrate synthase) gene is subject to glucose repression and is further repressed by glucose plus glutamate. Based on deletion analysis of a CIT1-lacZ gene fusion, DNA sequences between -548 and -273 are required for full expression of CIT1. The region of transcription initiation and the putative TATA element are located at -150 to -100 and -195 respectively. A restriction fragment containing DNA sequences between -457 and -211 conferred activation and glucose-glutamate regulation when placed in either orientation upstream of a USA-less heterologous yeast gene. Deletion of DNA sequences between -291 and -273 specifically eliminated derepression of CIT1, and destroyed one of two closely-spaced, potential binding sites for the HAP2,3,4 transcriptional activator protein. Tenbase-pair block substitutions in the region -367 to -348 reduced glucose-repressed expression. Thus, it appears that distinct DNA sequences upstream of CIT1 activate expression in glucose-repressed and derepressed cells. Possible mechanisms of regulation by glutamate plus glucose, are discussed.
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    Cloning and analysis of a FLO5 flocculation gene from S. cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 196-201 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Flocculation ; Cloning ; Expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A yeast flocculation gene was isolated from a genomic library of an FLO5 strain of S. cerevisiae on the basis of its ability to trigger flocculation in a non-flocculent strain. Characterization of the cloned gene by restriction mapping, Southern analysis, and chromosome mapping have shown that it corresponds to a FLO5 gene previously located on chromosome I and that this gene is related to the already described. FLO1 gene. A study of gene expression in different yeast strains has indicated that, while this gene is dominant, its expression can be suppressed in some genetic backgrounds. A Northern-blot analysis has demonstrated that the same 5000-nt transcript was present in an FLO5 and an FLO1 strain. A gene disruption experiment has led to the conclusion that another flocculation gene is present and can be active in the FLO5 strain we used.
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    PET112, a Saccharomyces cerevisiae nuclear gene required to maintain rho + mitochondrial DNA (1994)
    Springer
    Current genetics 25 (1994), S. 299-304 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; PET111 ; Translation ; COX2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear gene PET112 was originally identified by a mutation (pet112-1) that specifically blocked accumulation of cytochrome c oxidase subunit II. The mutation causes a post-transcriptional defect since the level of COX2 mRNA in the mutant is the same as in the wildtype. However, PET112 does not have a function similar to that of PET111, a COX2 mRNA-specific translational activator: while pet111 mutations are suppressed by chimeric COX2 mRNAs bearing 5′ leaders of other mitochondrial mRNAs, pet112-1 is not. The PET112 gene was isolated and shown to code a protein of 541 residues (62 kDa) with no significant homology to known amino-acid sequences. By hybridization to defined genomic clones the gene was mapped to chromosome II between cdc25 and ilsl. Disruption of the PET112 open reading frame destabilized the mitochondrial genome, causing cells to become rho-. This finding suggests that PET112 has an important general function in mitochondrial gene expression, probably in translation.
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    Overexpression of the SNQ3/YAP1 gene confers hyper-resistance to nitrosoguanidine in Saccharomyces cerevisiae via a glutathione-independent mechanism (1994)
    Springer
    Current genetics 25 (1994), S. 469-471 
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    ISSN: 1432-0983
    Keywords: Yeast ; GSH ; DNA alkylation ; MNNG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The MNNG hyper-resistance of yeast transformants containing multiple copies of the SNQ3/YAP1 yeast gene is not caused by lowered MNNG activation due to depleted pools of glutathione. On the contrary, the SNQ3/YAP1-encoded protein stimulates production of GSH, apparently by promoter activation due to the AP-1 recognition element. Expression of at least one further gene, encoding a protein with a strong detoxifying activity, must also be stimulated to explain the MNNG hyper-resistance phenotype.
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    Comparative analysis of the region of the mitochondrial genome contaning the ATPase subunit 9 gene in the two related yeast species Saccharomyces douglasii and Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 504-507 
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    ISSN: 1432-0983
    Keywords: Yeast ; S. douglasii ; mtDNA evolution ; ATPase subunit 9
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the nucleotide sequence of a region of the mitochondrial genome of the yeast Saccharomyces douglasii which contains the ATPase subunit 9 gene and part of the intergenic sequences that surround it. The gene is 228 nucleotides long and encodes a polypeptide of 76 aa. A comparison of the coding sequence with that of S. cerevisiae reveals the presence of three silent transitions. A high level of similarity is also found between regions involved in the initiation of transcription and mRNA processing. More interestingly, a region of similarity situated outside the known regulatory regions has been identified. As the intergenic regions are generally highly divergent, the remarkable conservation of these non-coding sequences suggests that their structure may be relevant to the expression of this region of the mitochondrial DNA.
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    Isolation and characterization of sulfite mutants of Saccharomyces cerevisiae (1994)
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    Current genetics 25 (1994), S. 488-496 
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    ISSN: 1432-0983
    Keywords: Sulfite ; Yeast ; Drug resistance ; Thioredoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sulfite-resistant and sulfite-sensitive mutants of Saccharomyces cerevisiae were isolated and characterized. Genetic analysis indicated that one and four genes were responsible for the resistant and sensitive responses, respectively, and suggested that defects in methionine and cysteine metabolism were not involved. Some resistant alleles, all of which were dominant, conferred greater resistance than others. Mutations conferring sensitivity were recessive and one co-segregated with impaired respiration. Two of the sensitive mutants exhibited cross-sensitivity to other metabolic inhibitors: sulfometuron methyl, cycloheximide, oligomycin, and antimycin A. A 50% glutathione deficiency in one sensitive mutant was not sufficient in itself to account for its sensitivity. Screening of other relevant mutants revealed that relative to wild-type, met8 and a thioredoxin null mutant are sensitive, and met3 and met14 mutants are not. Reduced production of extracellular acetaldehyde, a compound that detoxifies sulfite, was observed in three of the four sensitive mutants. However, acetaldehyde was also underproduced in the resistant mutant. Because sulfite is a reducing agent, cells were tested for coincident sensitivity or resistance to ascorbate, selenite, dithiothreitol, nitrite, thiosulfate, reduced glutathione, and cysteine. No consistent pattern of responses to these agents emerged, suggesting that the response to sulfite is not a simple function of redox potential.
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    An analysis of the sequence of part of the right arm of chromosome II of S. cerevisiae reveals new genes encoding an amino-acid permease and a carboxypeptidase (1994)
    Springer
    Current genetics 26 (1994), S. 1-7 
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    ISSN: 1432-0983
    Keywords: Yeast ; Sequence ; Amino-Acid Permease ; Carboxypeptidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have analysed two new genes, YBR1007 and YBR1015, discovered during the systematic sequencing of chromosome II of S. cerevisiae. YBR1007 shows strong similarities to amino-acid permeases, in particular the high-affinity proline permeases of S. cerevisiae and A. nidulans. The number and position of the predicted membrane-spanning domains suggest a conserved structure for these proteins, with 12 trans-membrane domains. YBR1015 shows strong similarities to serine carboxypeptidases; all three residues of the “catalytic triad” typical of this family of enzymes are conserved in the YBR1015 protein. In a preliminary functional analysis we have created a null allele of the YBR1015 gene, and shown that it is not essential for cellular viability.
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    Analysis of meiotic recombination events near a recombination hotspot in the yeast Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 26 (1994), S. 21-30 
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    ISSN: 1432-0983
    Keywords: Recombination ; Yeast ; Cross-over ; Gene conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The region of yeast chromosome III between the HIS4 and LEU2 genes has an unusually high frequency of meiotic recombination. In order to determine the pattern of cross-over and gene conversion events, we constructed a strain with a number of heterozygous markers in this 25-kb interval. We found that very high levels of reombination are localized to regions of DNA near HIS4. In addition, analysis of the patterns of co-conversion of adjacent markers suggests that there is more than one initiation site contributing to recombination of HIS4.
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    Formation of a minichromosome in Cryptococcus neoformans as a result of electroporative transformation (1994)
    Springer
    Current genetics 26 (1994), S. 54-61 
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    ISSN: 1432-0983
    Keywords: Transformation ; Minichromosome ; Yeast ; Cryptococcus neoformans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A minichromosome of approximately 270 kilobases was generated following complementation of a ura5 mutant strain of C. neoformans with the plasmid pURA5g2. This is the first report of the in-vivo generation of a minichromosome by the method of electroporative transformation. The minichromosome occurred at a relatively high (〉20%) frequency in transformants that were stable for uracil protoprophy. The minichromosome was maintained in linear form as a large extrachromosomal element of the normal karyotype. Gel-purified DNA from the minichromosome readily transformed the ura5 mutant of C. neoformans. Southern-blot analysis of the minichromosome revealed the presence of multiple copies of the URA5 gene and ribosomal DNA sequences in addition to containing telomere-like sequence repeats. The minichromosome was transmitted through mitosis and meiosis with extremely-high fidelity.
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    Mapping of additional markers in fission yeast, especially fus1 and three mfm genes (1994)
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    Current genetics 26 (1994), S. 187-189 
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    ISSN: 1432-0983
    Keywords: Mapping ; Yeast ; Schizosaccharomyces pombe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The following genes of the fission yeast Schizosaccharomyces pombe have been mapped by tetrad analysis — chromosome arm I-L: mfm2, rad24, rad25; I-R: abc1, fus1, mfm1; II-L: mfm3; II-R: mam1, rad13. A hotspot of meiotic recombination although not quite so active as suggested by previous maps, may be located between rad25 and aro5 on I-L.
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    Evidence for a nucleotide-dependent topoisomerase activity from yeast mitochondria (1994)
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    Current genetics 27 (1994), S. 31-37 
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    ISSN: 1432-0983
    Keywords: Topoisomerase ; Mitochondria ; Nucleotides ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Yeast mitochondria were found to contain a novel topoisomerase-like activity which required nucleoside di- or tri-phosphates as a cofactor. ADP supported activity as effectively as ATP and the optimal concentration for each was approximately 20 μM. None of the other standard ribo- or deoxyrib-onucleotides could fully substitute for either ADP or ATP. The non-hydrolyzable ATP analogs, adenosine-5′-0-(3-thiotriphosphate) (ATP-γ-S), adenylyl (β, γ-methylene) (AMP-PCP), and andenyl-imidodiphosphate (AMP-PNP) also supported activity suggesting that the nucleotide cofactor regulated topoisomerase activity rather than serving as an energy donor in the reaction. The mitochondrial topoisomerase activity relaxed both positively and negatively supercoiled DNA. It was not inhibited by concentrations of ethidium bromide up to 2 μg/ml nor by either nalidixic or oxolinic acids; novobiocin, coumermycin, and berenil inhibited the activity. Genetic and biochemical analysis of the mitochondrial topoisomerase activity indicated that it was not encoded by the nuclear TOP1, TOP2, and TOP3 genes.
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    Approaching the function of new genes by detection of their potential upstream activation sequences in Saccharomyces cerevisiae: application to chromosome III (1994)
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    Current genetics 25 (1994), S. 396-406 
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    ISSN: 1432-0983
    Keywords: Yeast ; Regulation ; UAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The systematic sequencing of the yeast genome reveals the presence of many potential genes of unknown function. One way to approach their function is to define which regulatory system controls their transcription. This can also be accomplished by the detection of an upstream activation sequence (UAS). Such a detection can be done by computer, provided that the definition of a UAS includes sufficient and precise rules. We have established such rules for the UASs of the GAL4, RAP1 (RPG box), GCN4, and the HAP2/HAP3/HAP4 regulatory proteins, as well as for a motif (PAC) frequently found upstream of the genes of the RNA polymerase A and C subunits. These rules were applied to the chromosome III DNA sequence, and gave precise predictions.
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    A 61-kb ring chromosome shows an ARS-dependent increase in its mitotic stability in the mcm2 mutant of yeast (1994)
    Springer
    Current genetics 26 (1994), S. 403-409 
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    ISSN: 1432-0983
    Keywords: Yeast ; DNA replication ; mcm ; Chromosome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have studied the effects of ARS addition and deletion on the maintenance of a 61-kb ring derivative of chromosome III in a minichromosome maintenance mutant of yeast carrying the mcm2-1 mutation. When this ring chromosome, CIIIR, had either of its two strong origins deleted, the resultant chromosome showed a much greater instability in the mutant as compared to that of the wild-type strain. Integration of more ARSs improved the maintenance of CIIIR in the mutant but not in the wild-type strain. Increase in the size of CIIIR, without any ARS addition, did not improve the stability in either strain. A spontaneous revertant for improved growth at 35°C also co-reverted for minichromosome and CIIIR maintenance. The results suggest that ARS malfunctioning leads to minichromosome and chromosome loss from mutant cells, affecting their growth at higher temperatures.
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    Molecular characterisation of GTP1, a Saccharomyces cerevisiae gene encoding a small GTP-binding protein (1994)
    Springer
    Current genetics 26 (1994), S. 564-566 
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    ISSN: 1432-0983
    Keywords: Small GTP-binding proteins ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA sequence analysis upstream of the yeast DNA repair gene SNM1 revealed gene GTP1 with an ORF of 573 bp on chromosome XIII. The putative amino-acid sequence of the encoded protein shows homology to proteins of the ARF-class of small GTP-binding proteins. Homology within GTP-binding motifs is highly conserved. Gene disruption showed that GTP1 is not an essential gene and that it has no influence on the expression of the DNA repair gene SNM1 with which it shares a 191-bp promoter region.
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    Identification of extragenic suppressors of the cif1 mutation in Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 89-94 
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    ISSN: 1432-0983
    Keywords: cif1 ; Suppressor ; Trehalose ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cif1 mutation of Saccharomyces cerevisiae causes inability to grow on glucose and related fermentable carbon sources. We have isolated two different suppressor mutations that allow growth on glucose of yeasts carrying the cif1 mutation. One of them, sci1-1, is recessive and caused inability to grow on non-fermentable carbon sources and to de-repress fructose-1,6-bisphosphatase. The other suppressor mutation, SCI2-1, is dominant and diminished the capacity to phosphorylate glucose or fructose. The SCI2-1 mutation decreased sporulation efficiency by 70% in heterozygosis and by more than 90% in homozygosis. In a CIF1 background, cells carrying the mutation SCI2-1 accumulated trehalose during the logarithmic phase of growth and hyperaccumulated it during the stationary phase. Genetic tests showed that SCI2 was either allelic, or else closely linked, to HXK2. The concentrations of the glycolytic metabolites measured during growth on glucose in cells carrying the cif1 mutation and any of the suppressor mutations were similar to those of a wild-type. Both types of suppressor mutations restored the transient cAMP response to glucose to cif1 mutants.
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    Identification of the yeast ACC1 gene product (acetyl-CoA carboxylase) as the target of the polyketide fungicide soraphen A (1994)
    Springer
    Current genetics 25 (1994), S. 95-100 
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    ISSN: 1432-0983
    Keywords: Acetyl-CoA carboxylase ; Polyketide antibiotic ; Soraphen A ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Soraphen A, a polyketide isolated from the myxobacterium Sorangium cellulosum, is a potent inhibitor of fungal growth. We have used a genetic approach to localize the target of this drug, employing Saccharomyces cerevisiae as a model organism. We have isolated soraphen A-resistant mutants and found that all of them map at the same genetic locus and exhibit a broad range of semidominant phenotypes. Data from genetic crosses of soraphen A-resistant clones with an acc1 mutant revealed that ACC1, coding for acetyl-CoA carboxylase (E.C. 6.4.1.2), is tightly linked to soraphen A resistance. Partially-purified enzyme extracts containing acetyl-CoA carboxylase were prepared and assayed for their soraphen A sensitivity. Our experiments showed that the catalytic activity of the wild-type enzyme is inhibited in vitro by soraphen A while the mutant enzyme remains catalytically active. Taken together these data strongly suggest that the ACC1 gene product is the primary target for soraphen A in vivo.
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    Yeast ts secretory mutation rgs1 is suppressed by the SEC4 gene of Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 178-179 
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    ISSN: 1432-0983
    Keywords: Yeast ; Secretion ; Vesicle fusion ; Rabproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Yeast rgs1 cells accumulate secretory vesicles in the cytoplasm and stop the secretion of proteins at the restrictive temperature. The ts mutation rgs1 may be suppressed by several different genes; the S. cerevisiae SEC4 gene, encoding the small G-protein involved in the late secretory stage, is one of them. Synthetic lethality of the double rgs1 sec4 mutant is demonstrated.
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    Effect of the new fluorescent brightener Rylux BSU on morphology and biosynthesis of cell walls in Saccharomyces cerevisiae (1994)
    Springer
    Archives of microbiology 161 (1994), S. 340-344 
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    ISSN: 1432-072X
    Keywords: Rylux BSU ; Fluorescent brightener ; Cell walls ; Chitin synthase ; Glucan synthase ; Yeast ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rylux BSU, a new fluorescent brightener from the family of 4,4′-diaminostilbene-2,2′disulfonic acid derivatives, inhibited growth and cytokinesis of the yeast Saccharomyces cerevisiae. In the presence of 0.1–1 mg/ml Rylux BSU the cells grew in clumps, had irregular shape and were larger than controls. They formed apparently normal primary septa but their secondary septa and lateral cell walls, especially those in older cells, were abnormally thick with large deposits of amorphous wall material in the periplasmic spaces all over the cell surface. Chitin content in the cell walls of cells grown in the presence of Rylux BSU was increased 2 to 5 times in comparison to that of the controls and glucan content was reduced by up to 30%. In the in vitro assays with particulate membrane fractions, Rylux BSU acted as a non-competitive inhibitor of β-1,3-glucan synthase with inhibitory constant K i=1.75 mg/ml whereas the chitin synthase was inhibited to a much lesser extent. From the difference of the effects of Rylux BSU on the synthesis of chitin in vivo and in vitro it is concluded that the brightener interacts with chitin synthase only indirectly, possibly by influencing the properties of integral plasma membrane.
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    Glycerol production from sugars with phosphoglycerate mutasedeficientSaccharomyces cerevisiae partially resistant to glucose repression (1994)
    Springer
    Journal of industrial microbiology and biotechnology 13 (1994), S. 17-23 
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    ISSN: 1476-5535
    Keywords: Yeast ; Glycerol production ; Low alcohol content wine ; Enology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Mutants partially resistant to the repressive effect of glucose have been isolated from aSaccharomyces cerevisiae strain totally deficient in phosphoglycerate mutase activity (EC 5.4.2.1) by a selection procedure involving the catabolite-repressive effect of 5-thio-d-glucose (5TG). These mutants are able to resist glucose concentrations up to 15 g L−1 and exhibit several non-repressed metabolic pathways such as gluconeogenesis, glyoxylic shunt or mitochondrial respiratory chain. Moreover, when these mutants are grown in aerobiosis on ethanol and glucose as sole substrates, glucose is mainly converted into glycerol in order to maintain a normal redox balance. Optimal glucose and oxygen concentrations have been defined for resting cells in order to obtain a glycerol yield from glucose close to 100%. The physiological characteristics of one of these mutants led us to consider an application of this yeast strain in reducing the ethanol content of wines previously lowered in ethanol content by physical processes.
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    Effect of the support matrix on biotransformation of benzaldehyde to benzyl alcohol by yeast cells in aqueous and aqueous-organic two phase systems (1994)
    Springer
    Journal of industrial microbiology and biotechnology 13 (1994), S. 172-176 
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    ISSN: 1476-5535
    Keywords: Immobilization ; Hydrophobic ; Hydrophilic ; Polymers ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Biotransformation of benzaldehyde to benzyl alcohol bySaccharomyces cerevisiae immobilized in different support matrices was investigated. Polymers with intrinsic hydrophobic and/or hydrophilic nature as well as mixed hydrophobic and hydrophilic supports were examined both in aqueous and bisphasic aqueous-organic systems. The hydrophobic support material ENTP-2000 or mixed silicone:alginate (50-25∶50-75) proved to be most suitable not only for nonconventional media but also for conventional aqueous media for production of benzyl alcohol. With ENTP-2000, catalytic activity and maximum yield were 159 μmol h−1 g−1 dry weight catalyst and 0.89 mM, respectively, in hexane containing 2% moisture. Corresponding values in aqueous media were 246 μmol h−1 g−1 dry weight catalyst and 1.53 mM. With 50∶50 silicone:alginate, catalytic activity and maximum yield were 177 μmol h−1 g−1 dry weight catalyst and 1.18 mM, respectively, in hexane containing 2% moisture. Corresponding values in aqueous media were 192 μmol h−1 g−1 dry weight catalyst and 0.8 mM.
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    Comparison of larval and adult P-450 activity levels for alkaloid metabolism in desertDrosophila (1994)
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    Journal of chemical ecology 20 (1994), S. 1893-1906 
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    ISSN: 1573-1561
    Keywords: Drosophila ; Diptera ; Drosophilidae ; cytochrome P-450 ; poly-substrate monooxygenase ; cactus ; alkaloids ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The cytochrome P-450 monooxygenase system has been implicated in plant utilization by at least three species ofDrosophila (D. nigrospiracula, D. mettleri, andD. mojavensis) that are endemic to the Sonoran Desert of the southwestern United States and northwestern Mexico. Basal and induced levels of total cytochrome P-450 were determined for third-instar and decapitated 2- to 5-day post eclosion adults of the three desert species. Total P-450 levels, both basal and induced for all species assayed, were significantly higher for adults than for larvae by up to 20-fold. On a per organism basis, the levels of in vitro metabolism of the cactus alkaloid, carnegine, and patterns of response to induction by cactus tissue for adult desertDrosophila approximated those of larvae. Induction by phenobarbital, however, resulted in levels of in vitro carnegine metabolism that were up to 5.6-fold higher in adults than in larvae.
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    Alterations in flightin phosphorylation inDrosophila flight muscles are associated with myofibrillar defects engendered by actin and myosin heavy-chain mutant alleles (1994)
    Springer
    Biochemical genetics 32 (1994), S. 301-314 
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    ISSN: 1573-4927
    Keywords: flightin ; Drosophila ; insect flight muscle ; phosphoprotein ; actin ; myosin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Flightin is a 20-kD myofibrillar protein found in the stretch-activated flight muscles ofDrosophila melanogaster. Nine of the eleven isoelectric variants of flightin are generatedin vivo by multiple phosphorylations. The accumulation of these isoelectric variants is affected differently by mutations that eliminate thick filaments or thin filaments. Mutations in the myosin heavy-chain gene that prevent thick filament assembly block accumulation of all flightin variants except N1, the unphosphorylated precursor, which is present at much reduced levels. Mutations in the flight muscle-specific actin gene that block actin synthesis and prevent thin filament assembly disrupt the temporal regulation of flightin phosphorylation, resulting in premature phosphorylation and premature accumulation of flightin phosphovariants. Cellular fractionation of fibers that are devoid of thin filaments show that flightin remains associated with the thick filamentrich cytomatrix. These results suggest that flightin is a structural component of the thick filaments whose regulated phosphorylation is dependent upon the presence of thin filaments.
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    Translational regulation of the heat shock response (1994)
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    Molecular biology reports 19 (1994), S. 211-220 
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    ISSN: 1573-4978
    Keywords: Drosophila ; eIF-2 ; eIF-4F ; heat shock ; mRNA translation regulation ; phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract All organisms from bacteria to man respond to an exposure to higher than physiological temperatures by reprogramming their gene expression, leading to the increased synthesis of a unique set of proteins termed heat shock proteins (hsps). The hsps function as molecular chaperones in both normal and stressed cells. The rapid and efficient synthesis of hsps is achieved as a result of changes occurring at gene transcription, RNA processing and degradation, and mRNA translation. With regard to the translational regulation, the emerging picture is that the two key steps of polypeptide chain initiation, namely mRNA binding and Met-tRNA i binding to ribosomes, are regulated in heat-shocked mammalian cells. InDrosophila, mRNA binding is regulated by a structural feature of the leader of heat shock mRNAs and by the inactivation of eukaryotic initiation factor- (eIF-) 4F. No clear evidence for changes in Met-tRNA i binding has been obtained yet.
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    Dependence of the kinetics of secondary active transports in yeast on H+-ATPase acidification (1994)
    Springer
    The journal of membrane biology 138 (1994), S. 29-35 
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    ISSN: 1432-1424
    Keywords: H+ symports ; Plasma membrane ATPase ; Local vs. delocalized protons ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Acidification of the external medium of the yeast Saccharomyces cerevisiae, mainly caused by proton extrusion by plasma membrane H+-ATPase, was inhibited to different degrees by D2O, diethylstilbestrol, suloctidil, vanadate, erythrosin B, cupric sulfate and dicyclohexylcarbodiimide. The same pattern of inhibition was found with the uptake of amino acids, adenine, uracil, and phosphate and sulfate anions. An increase of the acidification rate by dioctanoylglycerol also increased the rates of uptake of adenine and of glutamic acid. In contrast, a decrease of the membrane potential at pH 4.5 from a mean of -40 to -20 mV caused by 20 mm KC1 had no effect on the transport rates. The ATPase-deficient mutant S. cerevisiae pmal-105 showed a markedly lower uptake of all the above solutes as compared with the wild type, while its membrane potential and ΔpH were unchanged. Other types of acidification (spontaneous upon suspension; K+ stimulated) did not affect the secondary uptake systems. A partially competitive inhibition between some individual transport systems was observed, most pronouncedly with adenine as the most avidly transported solute. These observations, together with the earlier results that inhibition of H+-ATPase activity affects more the acidic than the basic amino acids and that it is more pronounced at higher pH values and at greater solute concentrations, support the view that it is the protons in or at the membrane, as they are extruded by the ATPase, that govern the rates of uptake by secondary active transport systems in yeast.
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    Cytokeratin 18 is an M-cell marker in porcine Peyer's patches (1994)
    Springer
    Cell & tissue research 276 (1994), S. 213-221 
    Details
    ISSN: 1432-0878
    Keywords: Gut-associated lymphoid tissue (GALT) ; M(membranous)-cells ; Immunohistochemistry ; Cytokeratins ; Yeast ; Pig (Minipig, Göttingen)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The intermediate filaments of the dome epithelium of porcine Peyer's patches were studied by immunohistochemistry. The labelling patterns of monospecific antibodies directed against cytokeratins 8, 18 and 19 differed considerably. About 40% of the dome epithelial cells were intensely labelled by three different anti-cytokeratin 18 antibodies, indicating that large amounts of cytokeratin 18 are present in these cells. In order to verify that these cytokeratin-18-immunoreactive cells were M-cells, uptake studies using fluorescein-labelled yeast particles were performed. Numerous yeast particles were found exclusively in dome epithelial cells that were highly positive for cytokeratin 18, thus representing M-cells. In contrast, the content of cytokeratin 19 in M-cells was lower than that in neighbouring enterocytes. The labelling intensity of cytokeratin 8 did not differ between M-cells and enterocytes. In addition, the absence of vimentin and desmin from the dome epithelium of porcine Peyer's patches was demonstrated. The results show (1) that porcine M-cells differ from enterocytes in the composition of their cytoskeleton, (2) that cytokeratin 18 is a useful marker for detecting porcine M-cells and (3) that this marker directly correlas with M-cell function.
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    URL: http://dx.doi.org/10.1007/BF00306106
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    Occurrence of osteoblast necroses during ossification of long bone cortices in mouse fetuses (1994)
    Springer
    Cell & tissue research 275 (1994), S. 345-353 
    Details
    ISSN: 1432-0878
    Keywords: Osteogenesis ; Ossification ; Mineralization ; Calcification ; Cell necroses ; Mouse (NMRI)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Previous investigations concerned with in vitro osteogenesis and mineralization have revealed some indication of a participation of cell necroses in the course of calcification. These observations were confirmed by in vivo investigations on desmoid ossification in fetal mouse calvariae, where abundant necrotic osteoblasts were found at the mineralization border and in the osteoid. In the present study, ossification of long bone cortices from fetal mice was investigated by use of electron microscopy. Specimens obtained from the collection of the Institute of Anatomy, Free University of Berlin (mouse fetuses, forearm; rat fetuses, forearm) were reinvestigated for control purposes. In all cases, mineralization of osteoid was accompanied by cell necroses. Cell degeneration was characterized by swelling of the endoplasmic reticulum and loss of the plasma membrane resulting in freely distributed vesicular structures. Cell debris was incorporated within the mineral. Initially, cell necroses in the perichondrium occurred in the region surrounding the hypertrophic cartilage and the matrix of which showed spots of endochondral mineralization. Necrotic osteoblasts occurred simultaneously with mineralization of the osteoid. During further ossification of the long bone cortices, the number of necrotic cells increased markedly. In addition to necrotic cells, healthy osteoblasts, osteocytes and perichondral tissue were present, indicating that an artifact can be excluded. The importance of cell necroses in the process of mineralization is as yet unclear. Possibly, the cells act as calcium and/or phosphate stores, which are liberated by cell death to increase the amount of mineral constituents at sites of mineralization.
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    Increase in incidence of chromosome instability and non-conservative recombination between repeats in Saccharomyces cerevisiae hpr1Δ strains (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 224-236 
    Details
    ISSN: 1617-4623
    Keywords: DNA deletions ; Reciprocal exchange ; Non-conservative recombination ; Yeast ; hpr1 Δ mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Null hprl Δ strains show a large increase (up to 2000-fold) over wild type in the frequency of occurrence of deletions between direct repeats on three different chromosomes. However, we show that hprl Δ mutations have little or no effect on reciprocal exchange, gene conversion or unequal sister chromatid exchange, as determined using intrachromosomal, interchromosomal and plasmid-chromosome assay systems. A novel intrachromosomal recombination system has allowed us to determine that over 95% of deletions in hpr1 Δ strains do not occur by reciprocal exchange. On the other hand, hpr1 Δ strains show chromosome loss frequencies of up to 100 times the wild-type level. Our results suggest that yeast cells have a very efficient non-conservative recombination mechanism, dependent on RADI and RAD52, that causes deletions between direct DNA repeats, and this mechanism is strongly stimulated in hpr1 Δ strains. The results indicate that the Hpr1 protein is required for stability of DNA repeats and chromosomes. We propose that in the absence of the Hprl protein the cell destabilizes the genome by allowing the initiation of events that lead to deletions of sequences between repeats, and to chromosome instability. We discuss the roles that proteins such as Hprl have in maintaining direct repeats and in preventing non-conservative recombination and consider the importance of these functions for chromosome stability.
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    Mating type regulates the radiation-associated stimulation of reciprocal translocation events in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 63-70 
    Details
    ISSN: 1617-4623
    Keywords: Radiation ; Reciprocal translocations ; MAT ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both ultraviolet (UV) and ionizing radiation were observed to stimulate mitotic, ectopic recombination between his3 recombinational substrates, generating reciprocal translocations in Saccharomyces cervisiae (yeast). The stimulation was greatest in diploid strains competent for sporulation and depends upon both the ploidy of the strain and heterozygosity at the MAT locus. The difference in levels of stimulation between MATa/MATα diploid and MATα haploid strains increases when cells are exposed to higher levels of UV radiation (sevenfold at 150 J/m2), whereas when cells are exposed to higher levels of ionizing radiation (23.4 krad), only a twofold difference is observed. When the MATα gene was introduced by DNA transformation into a MATa/matα::LEU2 + diploid, the levels of radiation-induced ectopic recombination approach those obtained in a strain that is heterozygous at MAT. Conversely, when the MATA gene was introduced by DNA transformation into a MATα haploid, no enhanced stimulation of ectopic recombination was observed when cells were irradiated with ionizing radiation but a threefold enhancement was observed when cells were irradiated with UV The increase in radiation-stimulated ectopic recombination resulting from heterozygosity at MAT correlated with greater spontaneous ectopic recombination and higher levels of viability after irradiation. We suggest that MAT functions that have been previously shown to control the level of mitotic, allelic recombination (homolog recombination) also control the level of mitotic, radiation-stimulated ectopic recombination between short dispersed repetitive sequences on non-homologous chromosomes.
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    Increases in cell size at START caused by hyperactivation of the cAMP pathway in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 158-165 
    Details
    ISSN: 1617-4623
    Keywords: Yeast ; Cell cycle ; Size control ; cAMP G1 cyclin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the budding yeast Saccharomyces cerevisiae, passage through START, which commits cells to a new round of cell division, requires growth to a critical size. To examine the effect of hyperactivation of the cAMP pathway on cell size at START, a strain was constructed that is able to respond to exogenously added cAMP. In the presence of cAMP, this strain showed increased cell volume at bud emergence, suggesting that the critical cell size necessary for START is increased. In addition, a mutation that results in unregulated cAMP-dependent protein kinase (bcy1) caused increased cell size at START. These results indicate that hyperactivation of the cAMP pathway causes increases in cell size through cAMP-dependent protein kinase. Cells carrying a hyperactive allele of CLN3 (CLN3-2) also showed increased size at START in the presence of cAMP. These cells retained resistance to α factor, however, suggesting that increases in cell size by cAMP are not due to a reduction of Cln3 activity. The observed increases in cell size due to hyperactivation of the cAMP pathway suggest that cell size modulation by nutrient conditions may be associated with a change of the activity of the cAMP pathway.
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    Prevalence and distribution of introns in non-ribosomal protein genes of yeast (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 532-539 
    Details
    ISSN: 1617-4623
    Keywords: Yeast ; prp2 ; Intron ; Genome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Relatively few genes in the yeast Saccharornyces cerevisiae are known to contain intervening sequences. As a group, yeast ribosomal protein genes exhibit a higher prevalence of introns when compared to non-ribosomal protein genes. In an effort to quantify this bias we have estimated the prevalence of intron sequences among non-ribosomal protein genes by assessing the number of prp2-sensitive mRNAs in an in vitro translation assay. These results, combined with an updated survey of the GenBank DNA database, support an estimate of 2.5% for intron-containing non-ribosomal protein genes. Furthermore, our observations reveal an intriguing distinction between the distributions of ribosomal protein and non-ribosomal protein intron lengths, suggestive of distinct, gene class-specific evolutionary pressures.
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    Calcified structures and calcification in protists (1994)
    Springer
    Protoplasma 181 (1994), S. 78-105 
    Details
    ISSN: 1615-6102
    Keywords: Calcification ; Coccolithophorids ; Coccolithogenesis ; Foraminifera ; Protists ; Taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The diversity of calcified structures found in protists, the mechanisms utilized to form these structures, and the role these structures play in the taxonomy and systematics of the protists are presented. The two most frequently studied orders of protists which produce calcified structures, the coccolithophorids and foraminifera, are featured. However, consideration is given to the less known and least studied organisms.
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    Recombinant protein expression in aDrosophila cell line: comparison with the baculovirus system (1994)
    Springer
    Cytotechnology 15 (1994), S. 139-144 
    Details
    ISSN: 1573-0778
    Keywords: Baculovirus ; cell culture ; Drosophila ; gene expression ; insect cell ; metallothionein promoter ; recombinant protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this report, we compare two different expression systems: baculovirus/Sf9 and stable recombinantDrosophila Schneider 2 (S2) cell lines. The construction of a recombinant S2 cell line is simple and quick, and in batch fermentations the cells have a doubling time of 20 hours until reaching a plateau density of 20 million cells/ml. Protein expression is driven by theDrosophila Metallothionein promoter which is tightly regulated. When expressed in S2 cells, the extracellular domain of human VCAM, an adhesion molecule, is indistinguishable from the same protein produced by baculovirus-infected Sf9 cells. Additionally, we present data on the expression of a seven trans-membrane protein, the dopamine D4 receptor, which has been successfully expressed in both systems. The receptor integrates correctly in the S2 membrane, binds [3H]spiperone with high affinity and exhibits pharmacological characteristics identical to that of the receptor expressed in Sf9 and mammalian cells. The general implications for large scale production of recombinant proteins are discussed.
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    Molecular heterogeneity of naturally occurringsn-glycerol-3-phosphate dehydrogenase low-activity variants inDrosophila melanogaster (1994)
    Springer
    Biochemical genetics 32 (1994), S. 161-179 
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    ISSN: 1573-4927
    Keywords: Drosophila ; glycerol-3-phosphate ; dehydrogenase ; low activity ; DNA sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Northern analyses of two low-activitysn-glycerol-3-phosphate dehydrogenase(Gpdh) alleles extracted from natural populations ofDrosophila melanogaster showed that one of them,Gpdh ACyg22 , produced wild-type levels of a normal sized (1.7-kb) mRNA but the other,Gpdh AMB5 , had very low levels of a 1.7-kb mRNA together with low levels of a transcript 200 bp larger. The two variant genes were cloned and sequenced. Compared with normal activity alleles, there were two nucleotide differences in the DNA sequence ofGpdh ACyg22 which were in first-codon positions and would be expected to give rise to Asn-13 → Tyr and Arg-272 → Cys substitutions. The second of these changes is most likely to account for the altered properties of the enzyme. In contrast, none of the nucleotide differences inGpdh AMB5 would give rise to amino acid substitutions, but a 76-bp deletion in the 5′ region removed the normal TATA box and there was a 20-bp insertion in the same region. One of the two transcripts was derived from the use of a substitute TATA box sequence in the insertion, but the 1.9-kb transcript had heterogeneous 5′ ends that were not associated with substitute TATA box sequences. The two transcripts either are produced at a lower rate or are less stable than the normal mRNA.
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    Histone H4 acetylated at lysine 16 and proteins of theDrosophila dosage compensation pathway co-localize on the male X chromosome through mitosis (1994)
    Springer
    Chromosome research 2 (1994), S. 398-404 
    Details
    ISSN: 1573-6849
    Keywords: dosage compensation ; Drosophila ; histone acetylation ; nuclear domains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the fruit flyDrosophila, dosage compensation involves several proteins acting in concert to double the transcriptional activity of genes on the single male X chromosome. Three of these proteins, MLE, MSL-1 and histone H4 acetylated at lysine 16 (H4Ac16), have recently been shown to be located almost exclusively on the male X chromosome in interphase (polytene) cells. We show here that in neuroblasts from third instarDrosophila larvae antisera to H4Ac16, MLE and MSL-1 uniquely label the distal, euchromatic region of the male X chromosome through mitosis. The centromere-proximal, heterochromatic region of the male X is not labelled with these antisera, nor are male autosomes or any chromosomes in female cells. That the association of H4Ac16 with the male X chromosome persists, even when the chromosome is maximally compacted and transcriptionally quiescent, argues that this modified histone is an integral component of the dosage compensation pathway. In the nuclei of interphase neuroblasts from male (but never female) larvae, antibodies to H4Ac16 revealed a small, brightly labelled patch against a background of generally weak nuclear staining. In double-labelling experiments, this patch was also labelled, albeit comparatively weakly, with antibodies to MSL-1. These results strongly suggest that the distal, euchromatic region of the X chromosome in male cells occupies a limited and relatively compact nuclear domain.
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    Interactions between gene products involved in divalent cation transport in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 303-311 
    Details
    ISSN: 1617-4623
    Keywords: Metal homeostasis ; Metal resistance ; Transport ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The COT1 and ZRC1 genes of Saccharomyces cerevisiae are structurally related dosage-dependent suppressors of metal toxicity. COT1 confers increased tolerance to high levels of cobalt; ZRC1 confers increased tolerance to high levels of zinc. The two genes are not linked and have been mapped; COT1 to chromosome XV and ZRC1 to chromosome XIII. Phenotypes related to metal homeostasis have been examined in strains with varied COT1 and ZRC1 gene doses. Overexpression of COT1 confers tolerance to moderately toxic levels of zinc and ZRC1 confers tolerance to moderately toxic levels of cobalt. Strains that carry null alleles at both loci are viable. The metal-hypersensitive phenotypes of mutations in either gene are largely unaffected by changes in dosage of the other. COT1 and ZRCI function independently in conferring tolerance to their respective metals, yet the uptake of cobalt ions by yeast cells is dependent on the gene dosage of ZRC1 as well as of COT1 Strains that overexpress ZRC1 have increased uptake of cobalt ions, while ZRCI null mutants exhibit decreased cobalt uptake. The defects in cobalt uptake due to mutations at COT1 and ZRC1 are additive, suggesting that the two genes are responsible for the majority of cobalt and zinc uptake in yeast cells. The function of either gene product seems to be more important in metal homeostasis than is the GRR1 gene product, which is also involved in metal metabolism. Mutations in the GRR1 gene have no effect on the cobalt-related phenotypes of strains that have altered gene dosage of either COT1 or ZRC1.
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    bHLH proteins encoded by theEnhancer of split complex ofDrosophila negatively interfere with transcriptional activation mediated by proneural genes (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 465-473 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Enhancer of split ; Helix-loop-helix protein ; Neurogenesis ; Transcriptional repressors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract TheEnhancer of split complex [E(SPL)-C] ofDrosophila participates in the control of cell fate choice by uncommitted neuroectodermal cells in the embryo. It encodes seven proteins that belong to the basic helix-loop-helix (bHLH) family, six of which are expressed in very similar patterns in the neuroectoderm. Here we describe experiments aimed at unravelling the molecular basis of their function. We found that two products of the complex, HLH-M5 andEnhancer of split, are capable of binding as homo-and heterodimers to a sequence in the promoters of theEnhancer of split andachaete genes, called the N-box, which differs slightly from the consensus binding site (the E-box) for other bHLH proteins. In transient expression assays in cell culture, both proteins were found to attenuate the transcriptional activation mediated by the proneural bHLH proteinslethal of scute anddaughterless at theEnhancer of split promoter.
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    Reduced but accurate translation from a mutant AUA initiation codon in the mitochondrial COX2 mRNA of Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 383-390 
    Details
    ISSN: 1617-4623
    Keywords: Mitochondria ; Translation ; Yeast ; PET111 ; PET2858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have changed the translation initiation codon of the COX2 mRNA of Saccharomyces cerevisiae from AUG to AUA, generating a mutation termed cox2-10. This mutation reduced translation of the COX2 mRNA at least five-fold without affecting the steady-state level of the mRNA, and produced a leaky nonrespiratory growth phenotype. To address the question of whether residual translation of the cox2-10 mRNA was initiating at the altered initiation codon or at the next AUG codon downstream (at position 14), we took advantage of the fact that the mature coxll protein is generated from the electrophoretically distinguishable coxII precursor by removal of the amino-terminal 15 residues, and that this processing can be blocked by a mutation in the nuclear gene PET2858. We constructed a pet2858, cox2-10 double mutant strain using a pet2858 allele from our mutant collection. The double mutant accumulated low levels of a polypeptide which comigrated with the coxII precursor protein, not the mature species, providing strong evidence that residual initiation was occurring at the mutant AUA codon. Residual translation of the mutant mRNA required the COX2 mRNA-specific activator PET111. Furthermore, growth of cox2-10 mutant strains was sensitive to alterations in PET111 gene dosage: the respiratory-defective growth phenotype was partially suppressed in haploid strains containing PET111 on a high-copy-number vector, but became more severe in diploid strains containing only one functional copy of PET111.
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    ACR1, a gene encoding a protein related to mitochondrial carriers, is essential for acetyl-CoA synthetase activity in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 727-735 
    Details
    ISSN: 1617-4623
    Keywords: Acetyl-CoA synthetase ; Mitochondrial carriers ; Sequence ; Disruption ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The utilization of ethanol via acetate by the yeast Saccharomyces cerevisiae requires the presence of the enzyme acetyl-coenzyme A synthetase (acetyl-CoA synthetase), which catalyzes the activation of acetate to acetyl-coenzyme A (acetyl-CoA). We have isolated a mutant, termed acr1, defective for this activity by screening for mutants unable to utilize ethanol as a sole carbon source. Genetic and biochemical characterization show that, in this mutant, the structural gene for acetyl-CoA synthetase is not affected. Cloning and sequencing demonstrated that the ACR1 gene encodes a protein of 321 amino acids with a molecular mass of 35 370 Da. Computer analysis suggested that the ACR1 gene product (ACR1) is an integral membrane protein related to the family of mitochondrial carriers. The expression of the gene is induced by growing yeast cells in media containing ethanol or acetate as sole carbon sources and is repressed by glucose. ACR1 is essential for the utilization of ethanol and acetate since a mutant carrying a disruption in this gene is unable to grow on these compounds.
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    Discrimination of related transcribed and non-transcribed repetitive DNA sequences from the Y chromosomes of Drosophila hydei and Drosophila eohydei (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 54-62 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Y chromosome ; Fertility genes Lampbrush loops ; Repetitive DNA sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The short arm of the Y chromosome of Drosophila hydei carries a single male fertility gene, gene Q, which forms the lampbrush loop pair Nooses. Conflicting observations have been reported concerning the identity of the repetitive DNA sequences that are transcribed in this loop pair. It has been claimed by other investigators that the loop transcripts contain repeats of two distinct, but related families of Y-specific repetitive DNA sequences, ayl and YsI. We reinvestigated this issue, using as probes single ayl and YsI repeats which, under stringent conditions, hybridize only to members of their own family. Under non-stringent conditions, both repeats hybridize in situ to Nooses transcripts. However, if hybridization conditions are stringent, only the ayl probe hybridizes to loop transcripts. Hybridizations to Northern blots of testis RNA confirm these results. Further, YsI repeats are not found the closely related species D. eohydei. We conclude that the YsI repeats are not relevant for the function of fertility gene Q.
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    Drosophila GABAergic systems II. Mutational analysis of chromosomal segment 64AB, a region containing the glutamic acid decarboxylase gene (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 555-564 
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    ISSN: 1617-4623
    Keywords: Drosophila ; Glutamic acid decarboxylase ; GAD ; GABA ; Lethal mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Drosophila melanogaster Gad gene maps to region 64A3-5 of chromosome 3L and encodes glutamic acid decarboxylase (GAD), the rate-limiting enzyme for the synthesis of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Because this neurotransmitter has been implicated in developmental functions, we have begun to study the role of GABA synthesis during Drosophila embryogenesis. We show that Gad mRNA is expressed in a widespread pattern within the embryonic nervous system. Similarly, GAD-immunoreactive protein is present during embryogenesis. These results prompted us to screen for embryonic lethal mutations that affect GAD activity. The chromosomal region to which Gad maps, however, has not been subjected to an extensive mutational analysis, even though it contains several genes encoding important neurobiological, developmental, or cellular functions. Therefore, we have initially generated both chromosomal rearangements and point mutations that map to the Drosophila 64AB interval. Altogether, a total of 33 rearrangements and putative point mutations were identified within region 64A3-5 to 64B12. Genetic complementation analysis suggests that this cytogenetic interval contains a minimum of 19 essential genes. Within our collection of lethal mutations are several chromosomal rearrangements, two of which are in the vicinity of the Gad locus. One of these rearrangements, Df(3L)C175, is a small deletion that removes the Gad locus and at least two essential genes; the second, T(2;3)F10, is a reciprocal translocation involving the second and third chromosomes with a break within region 64A3-5. Both of these rearrangements are associated with embryonic lethality and decreased GAD enzymatic activity.
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    Transcription of repetitive DNA sequences in the lampbrush loop pair Nooses formed by sterile alleles of fertility gene Q on the Y chromosome of Drosophila hydei (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 653-660 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Fertility genes ; Y chromosome Lampbrush loops ; Repetitive DNA sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Y chromosomal lampbrush loop-forming male fertility genes of Drosophila consist mainly of repetitive DNA sequences that do not code for proteins. We investigated whether differences in the transcription of these sequences can be detected in male-sterile alleles of male fertility gene Q, which forms the loop pair Nooses. The loop consists, for approximately two-thirds, of repeats of the Y-specific ay1 family of repetitive DNA sequences. Of the remaining one-third, at least one-half is represented by defective retrotransposons of the gypsy family. Both sequence types are interspersed throughout the loop. Using both ay1 and gypsy sequences as probes for transcript in situ hybridization, we show that, at the level of the light microscope, transcription of neither sequence is detectably affected in the loops formed by a male-sterile allele of gene Q. We conclude that the transcription of ay1 and gypsy is required, but not sufficient for the function of gene Q.
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    In vivo analysis of chromatin following nystatin-mediated import of active enzymes into Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 100-104 
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    ISSN: 1617-4623
    Keywords: Chromatin ; Nystatin ; DNA topoisomerase I ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vivo DNA-protein interactions are usually studied at the molecular level using DNA-degrading agents of low molecular weight. In order to be useful, macromolecular probes of chromatin structure, such as enzymes must first cross the cell membrane. In this paper we describe the introduction and evaluation of macromolecules with enzymatic activity into yeast spheroplasts treated with the polyene antibiotic nystatin. We report the low resolution analysis of chromatin structure in the promoter region of the Saccharomyces cerevisiae gene encoding DNA topoisomerase I by this technique using micrococcal nuclease and restriction enzymes.
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    The lysozyme locus in Drosophila melanogaster: an expanded gene family adapted for expression in the digestive tract (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 152-162 
    Details
    ISSN: 1617-4623
    Keywords: Antibacterial ; Digestive tract ; Drosophila ; Gene family ; Lysozyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lysozyme has been studied in insects as part of the system of inducible antibacterial defence in the haemolymph. We recently found two Drosophila lysozyme genes that are constitutively expressed in the digestive tract, and are probably involved in the digestion of bacteria in the food. To obtain an overview of the lysozyme genes in this species and their possible roles in immunity and digestion, we have now characterized all six lysozyme genes in the cloned part of the lysozyme locus at 61F, and a seventh gene that maps to the same chromosomal location. The expression of the genes follows four different patterns: firstly, four closely related genes, LysB, C, D and E, are all strongly expressed in the midgut of larvae and adults; secondly, LysP is expressed in the adult salivary gland; thirdly, LysS is expressed mainly in the gastric caecae of larvae; and finally, LysX is primarily expressed in the metamorphosing midgut of late larvae and early pupae. The LysD-like genes and LysS are strongly repressed in artificially infected animals, possibly reflecting a malaise reaction in the digestive tract. None of the genes is expressed in the fat body or haemocytes. Thus rather than being a component of the haemolymph, the Drosophila lysozymes are found mainly in the digestive tract where they are expressed at a high level. Furthermore all genes, except LysP, encode acidic proteins, in contrast to the strongly basic “typical” lysozymes. This is highly reminiscent of the situation in ruminants, where the lysozymes have been recruited for the digestion of symbiotic bacteria in the stomach.
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    URL: http://dx.doi.org/10.1007/BF00391008
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    Meiosis-dependent tyrosine phosphorylation of a yeast protein related to the mouse p51ferT (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 160-167 
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    ISSN: 1617-4623
    Keywords: p51ferT ; Yeast ; Meiosis ; Phosphotyrosine Kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The FER locus of the mouse encodes two mRNA species: one is constitutively transcribed, giving rise to a 94 kDa tyrosine kinase (p94ferT); the second is a meiosis-specific RNA that gives rise to a 51 kDa tyrosine kinase (p51ferT). The p51ferT RNA and protein accumulate in primary spermatocytes that are in prophase of the first meiotic division. By using polyclonal antibodies directed against synthetic peptides derived from the unique amino-terminus of the mouse p51ferT, a 51 kDa phosphotyrosyl protein — p51y — was identified in Saccharomyces cerevisiae. The p51y protein is constitutively expressed in yeast, but in meiotic cells, concomitantly with commitment to meiotic recombination, its level of phosphorylation on tyrosine residues is increased. A different pattern of phosphorylation is observed on serine residues: at early meiotic times the level is decreased, while in later meiotic time the level increases, reaching the vegetative level. When p51ferT is ectopically expressed in yeast, it is active, leading to preferential phosphorylation of an approx. 65 kDa protein. A similar pattern of phosphorylation by p51ferT is seen in mammalian cells.
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    URL: http://dx.doi.org/10.1007/BF00283517
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    The archaebacterial membrane protein bacterio-opsin is expressed and N-terminally processed in the yeast Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 183-188 
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    ISSN: 1617-4623
    Keywords: Bacterio-opsin ; Expression ; Yeast ; Saccharomyces cerevisiae ; Membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bop gene codes for the membrane protein bacterio-opsin (BO), which on binding all-trans-retinal, constitutes the light-driven proton pump bacteriorhodopsin (BR) in the archaebacterium Halobacterium salinarium The designation H. salinarium instead of the former designation H. halobium is used throughout this paper following the classification of Tindall (1992) . This gene was cloned in a yeast multi-copy vector and expressed in Saccharomyces cerevisiae under the control of the constitutive ADH1 promoter. Both the authentic gene and a modified form lacking the precursor sequence were expressed in yeast. Both proteins are incorporated into the membrane in S. cerevisiae. The presequence is thus not required for membrane targeting and insertion of the archaebacterial protein in budding yeast, or in the fission yeast Schizosaccharomyces pombe, as has been shown previously. However, in contrast to S. pombe transformants, which take on a reddish colour when all-trans-retinal is added to the culture medium as a result of the in vivo regeneration of the pigment, S. cerevisiae cells expressing BO do not take on a red colour. The precursor of BO is processed to a protein identical in size to the mature BO found in the purple membrane of Halobacterium. The efficiency of processing in S. cerevisiae is dependent on growth phase, as well as on the composition of the medium and on the strain used. The efficiency of processing of BR is reduced in S. pombe and in a retinal-deficient strain of H. salinarium, when retinal is present in the medium.
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    Functional relationships between genes of the Shaker gene complex of Drosophila (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 197-204 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Shaker gene complex Dominant lethality ; K+ channel ; Troponin I
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Different mutations belonging to the HLI and HLII complementation groups of the haplolethal (HL) region of the Shaker complex (ShC) are described. The HLI complementation group includes viable (hdp), recessive lethals [l(1)1614], semidominant lethals [l(1)8384] and dominant lethals [l(1)5051,l(1)9916, l(1)13193], lack-of-function alleles that affect nervous system, cuticle and muscle development. The HLI complementation group encodes troponin I. HLII lack-of-function mutations [l(1)174 and l(l)4058] affect nervous system development. The semidominant lethal HLI mutation 1(1)8384 shows differential complementation with other mutations in the ME and HL regions of ShC. Thus, heterozygous combinations of l(1)8384 with ME mutations l(1)162 and l(1)387 are poorly viable. The same phenomenon is observed for heterozygotes of l(1)8384 with HL mutations l(1)1199, l(1)2288 and l(1)3014. These specific interactions indicate the existence of functional relationships among the genetic elements of ShC. The implications for the understanding of the functional organization of ShC are discussed.
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    URL: http://dx.doi.org/10.1007/BF00283523
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    Functional interactions between the gene tetanic and the Shaker gene complex of Drosophila (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 205-215 
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    ISSN: 1617-4623
    Keywords: Drosophila ; tetanic ; Shaker gene complex ; Maternal effect ; K+ channel modulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Different phenotypes associated with the tetanic (tta) mutation such as appendage contraction, maternal effect and low viability and fertility are enhanced by one extra dose of the Shaker gene complex (ShC). The tta mutation is lethal with two extra doses of ShC. In addition, tta embryos have a defective nervous system. In this paper, I analyse the interaction between tta and ShC to gain insight into their relationship. Aneuploid analysis suggests that the lethality is due to an interaction of the tta mutation with the maternal effect (ME) region of this gene complex. Mutations in the ME region of ShC partially suppress this interaction. Trans-heterozygous combinations of MEI[l(1)305] and MEIII [l(1)459] mutations causes dominant lethality in a tta background. Trans-heterozygous combinations of an MEII [l(1)1359] mutation with the cited MEI and MEIII mutations are lethal in a tta background. Double mutant combinations and gene dosage experiments, suggest that tta also interacts with the viable (V) region of ShC. These specific genetic interactions indicate that tta and the ME and V regions of ShC are functionally related. These results, together with the previous electrophysiological, molecular and biochemical studies on these mutants suggest an interaction at the protein level. Thus, in the case of the V region, the tta gene product may modulate the activity of the K+ channels encoded in this region. Furthermore, the extreme dosage sensitivity of the interaction between tta and ShC suggests a stoichiometric requirement for the different gene products involved, which might be physically associated and form heteromultimers.
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    URL: http://dx.doi.org/10.1007/BF00283524
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    Drosophila melanogaster acetylcholinesterase: Identification and expression of two mutations responsible for cold- and heat-sensitive phenotypes (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 699-705 
    Details
    ISSN: 1617-4623
    Keywords: Acetylcholinesterase ; Drosophila ; Thermosensitive mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ace IJ29 and Ac IJ40 are cold- and heat-sensitive variants of the gene coding for acetylcholinesterase in Drosophila melanogaster. In the homozygous condition, these mutations are lethal when animals are raised at restrictive temperatures, i.e., below 23° C for Ace IJ29 or above 25° C for Ace IJ40. The coding regions of the gene in these mutants were sequenced and mutations changing Ser374 to Phe in Ace IJ29 and Pro75 to Leu in Ace IJ40 were found. Acetylcholinesterases bearing these mutations were expressed in Xenopus oocytes and we found that these mutations decrease the secretion rate of the protein most probably by affecting its folding. This phenomenon is exacerbated at restrictive temperatures decreasing the amount of secreted acetylcholinesterase below the lethality threshold. In parallel, the substitution of the conserved Asp248 by an Asn residue completely inhibits the activity of the enzyme and its secretion, preventing the correct folding of the protein in a non-conditional manner.
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    URL: http://dx.doi.org/10.1007/BF00279580
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    DPhK-γ, a putative Drosophila kinase with homology to vertebrate phosphorylase kinase γ subunits: molecular characterisation of the gene and phenotypic analysis of loss of function mutants (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 588-597 
    Details
    ISSN: 1617-4623
    Keywords: Phosphorylase kinase γ gene ; Kinase ; Drosophila ; Maternal effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Partial and total loss of function mutant alleles of a putative Drosophila homologue (DPhK-γ) of the vertebrate phosphorylase kinase γ-subunit gene have been isolated. DPhK-γ is required in early embryonic processes, such as gastrulation and mesoderm formation; however, defects in these processes are seen only when both the maternal and zygotic components of DPhK-γ expression are eliminated. Loss of zygotic expression alone does not appear to affect normal embryonic and larval development; some pupal lethality is observed but the majority of mutant animals eclose as adults. Many of these adults show defects in their leg musculature (e.g. missing and degenerating muscles), in addition to exhibiting melanised “tumours” on their leg joints. Loss of only the maternal component has no obvious phenotypic consequences. The DPhKγ gene has been cloned and sequenced. It has an open reading frame (ORF) of 1680 by encoding a 560 amino acid protein. The predicted amino acid sequence of DPhK-γ has two conserved domains, the catalytic kinase and calmodulin-binding domains, separated by a linker sequence. The amino acid sequence of DPhK-γ is homologous to that of mammalian PhK-γ proteins but differs in the length and amino acid composition of its linker sequence. The expression of DPhK-γ mRNA is developmentally regulated. We discuss the implications of these observations.
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    Expression of human poly(ADP-ribose) polymerase in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 686-693 
    Details
    ISSN: 1617-4623
    Keywords: Yeast ; Saccharomyces cerevisiae ; Poly(ADP-ribose) polymerase ; DNA repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The coding sequence for human poly(ADP-ribose) polymerase was expressed inducibly in Saccharomyces cerevisiae from a low-copy-number plasmid vector. Cell free extracts of induced cells had poly(ADPribose) polymerase activity when assayed under standard conditions; activity could not be detected in non-induced cell extracts. Induced cells formed poly(ADP-ribose) in vivo, and levels of these polymers increased when cells were treated with the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). The cytotoxicity of this agent was increased in induced cells, and in vivo labelling with [3H]adenine further decreased their viability. Increased levels of poly(ADP-ribose) found in cells treated with the alkylating agent were not accompanied by lowering of the NAD concentration.
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    Genetic interactions between SIN3 mutations and the Saccharomyces cerevisiae transcriptional activators encoded by MCM1, STE12, and SWI1 (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 675-685 
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    ISSN: 1617-4623
    Keywords: Yeast ; Transcriptional regulation ; SIN3 STE12 ; SWI1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract SIN3 was first identified by a mutation which suppresses the effects of an swi5 mutation on expression of the HO gene in Saccharomyces cerevisiae. We now show that a sin3 mutation also partially suppresses the effects of swi1 on HO transcription, and partially suppresses the growth defect and inositol requirement observed in swi1 mutants. This suggests that SIN3 and SWI1 may play opposite regulatory roles in controlling expression of many yeast genes. Yeast SIN3 has been shown to function as a negative transcriptional regulator of a number of yeast genes. However, expression of the yeast STE6 gene is reduced in a sin3 mutant strain. This suggests that SIN3 functions as a positive regulator for STE6 transcription, although this apparent activation function could be indirect. In order to understand how SIN3 functions in STE6 regulation, we have performed a genetic analysis. It has been previously demonstrated that MCM1 and STE12 are transcriptional activators of a-specific genes such as STE6, and we now show that SWI1 is also required for STE6 expression. Our data suggest that STE12 and SWI1 function in different pathways of activation, and that STE12 is epistatic to SIN3 and SWI1. We show that the activities of the Mcmlp and Stel2p activators are modestly reduced in a sin3 mutant strain, and that phosphorylation of the Stel2p activator is decreased in a sin3 mutant. Thus, it is possible that the decreased transcription of STE6 in sin3 mutants is due to the combined effect of the diminished activities of Mcmlp and Stel2p.
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    Pleiotropic function of ArgRIIIp (Arg82p), one of the regulators of arginine metabolism in Saccharomyces cerevisiae. Role in expression of cell-type-specific genes (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 315-324 
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    ISSN: 1617-4623
    Keywords: Yeast ; Arginine ; Cell-type regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract ArgRIIIp (Arg82p), together with ArgRIp (Arg80p), ArgRIIp (Arg81p) and Mcmlp, regulates the expression of arginine anabolic and catabolic genes. An argRIII mutant constitutively expresses five anabolic enzymes and is impaired in the induction of the synthesis of two catabolic enzymes. A genomic disruption of the ARGRIII gene not only leads to an argR phenotype, but also prevents cell growth at 37°C. The disrupted strain is sterile especially in an α background and transcription of α- and a-specific genes (MFα1 and STE2) is strongly reduced. By gel retardation assays we show that the binding of the Mcmlp present in a crude protein extract from an argRIII mutant strain to the P(PAL) sequence is impaired. Sporulation of α/a argRIII:: URA3 homozygous diploids is also affected. Overexpression of Mcm1p in an argRIII-disrupted strain restores the mating competence of the strain, the ability to form a protein complex with P(PAL) DNA in vitro, and the regulation of arginine metabolism. However, overexpression of Mcm1p does not complement the sporulation deficiency of the argRIII-disrupted strain, nor does it complement its growth defect at 37°C. Western blot analysis indicates that Mcm1p is less abundant in a strain devoid of ArgRIIIp than in wild type.
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    DrosophilaP element: Transposition, regulation and evolution (1994)
    Springer
    Genetica 93 (1994), S. 61-78 
    Details
    ISSN: 1573-6857
    Keywords: Drosophila ; transposable elements ; hybrid dysgenesis ; transcriptional regulation ; horizontal transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    URL: http://dx.doi.org/10.1007/BF01435240
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    Genome and stresses: Reactions against aggressions, behavior of transposable elements (1994)
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    Genetica 93 (1994), S. 149-160 
    Details
    ISSN: 1573-6857
    Keywords: environment ; genome ; stress ; transposable elements ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The action of stresses on the genome can be considered as responses of cells or organisms to external aggressions. Stress factors are of environmental origin (climatic or trophic) or of genomic nature (introduction of foreign genetic material, for example). In both cases, important perturbations can occur and modify hereditary potentialities, creating new combinations compatible with survival; such a situation may increase the variability of the genome, and allow evolutive processes to take place. The behavior of transposable elements under stress conditions is thus of particular interest, since these sequences are sources of mutations and therefore of genetic variability; they may play an important role in population adaptation. The survey of the available experimental results suggests that, although some examples of mutations and transposable elements movements induced by external factors are clearly described, environmental injuries or introduction of foreign material into a genome are not systematically followed by drastic genomic changes.
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    Analysis of nucleotide substitutions and amino acid conservation in theDrosophila Adh genomic region (1994)
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    Genetica 94 (1994), S. 27-36 
    Details
    ISSN: 1573-6857
    Keywords: Adh ; Adh-dup ; Drosophila ; molecular clock ; nucleotide substitution rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The homologous genomic region that contains two paralogous genes,Adh andAdh-dup, was compared in severalDrosophila species. Sequences were analyzed as follows: a) At the nucleotide level, Ka and Ks values were determined for each pair of species. Ka-Adh and Ka-Adh-dup are not significantly different. However, Ks-Adh values are significantly lower than Ks-Adh-dup, which are more variable. In agreement with other reports, lower Ks values forAdh correlate with a high level of gene expression and relatively high percentage of G+C content in the third codon position, while the opposite applies toAdh-dup. b) At the protein level, amino acid comparisons reveal conserved regions shared by ADH and ADH-DUP, which have been assigned to known functional domains. Key residues for dehydrogenasic function are also found in ADH-DUP, thus pointing to a dehydrogenase activity for ADH-DUP, albeit very different from that of ADH.
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    Associations of esterase 6 allozyme and activity variation with reproductive fitness inDrosophila melanogaster (1994)
    Springer
    Genetica 94 (1994), S. 43-56 
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    ISSN: 1573-6857
    Keywords: Drosophila ; esterase 6 ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have shown that the esterase 6 (EST6) enzyme ofD. melanogaster is mainly produced in the sperm ejaculatory duct of the adult male and comparisons of wild-type males with laboratory null mutants have suggested that the enzyme plays a role in reproductive fitness. In this study we have compared 18 field-derived lines each isoallelic forEst6 for differences in five components of male reproductive fitness. No consistent fitness differences were found among lines differing in respect of the two major allozyme classes EST6-F and EST6-S, despite other evidence that these two classes are not selectively equivalent in the field. However, differences in reproductive fitness were found among lines differing in the minor mobility variants that segregate within EST6-F and EST6-S. A failure to distinguish among these minor forms may explain the discrepancies in previous studies on the effects of the major EST6 allozymes on reproductive fitness. The most significant associations we have found between EST6 and reproductive fitness were due to variation in EST6 activity levels. Male EST6 activity levels were found to be positively correlated with their time to first mating, negatively correlated with the numbers of eggs laid and progeny produced by their mates, and negatively correlated with the frequency with which their mates remate. We conclude that some EST6 variants differ in components of male reproductive fitness operative in laboratory cultures. However, the evidence for fitness differences is stronger for variants affecting the amount, rather than the structure of the enzyme, and the direction of the differences varies between some of the fitness components tested.
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    Genetic, molecular and developmental analysis of the glutamine synthetase isozymes ofDrosophila melanogaster (1994)
    Springer
    Genetica 94 (1994), S. 275-281 
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    ISSN: 1573-6857
    Keywords: Drosophila ; glutamine synthetase ; isozyme functional specialization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The glutamine synthetase isozymes ofDrosophila melanogaster offer an attractive model for the study of the molecular genetics and evolution of a small gene family encoding enzymatic isoforms that evolved to assume a variety of specific and sometimes essential biological functions. InDrosophila melanogaster two GS. isozymes have been described which exhibit different cellular localisation and are coded by a two-member gene family. The mitochondrial GS structural gene resides at the 21B region of the second chromosome, the structural gene for the cytosolic isoform at the 10B region of the X chromosome. cDNA clones corresponding to the two genes have been isolated and sequenced. Evolutionary analysis data are in accord with the hypothesis that the twoDrosophila glutamine synthetase genes are derived from a duplication event that occurred near the time of divergence between Insecta and Vertebrata. Both isoforms catalyse all reactions catalysed by other glutamine synthetases, but the different kinetic parameters and the different cellular compartmentalisation suggest strong functional specialisation. In fact, mutations of the mitochondrial GS gene produce embryo-lethal female sterility, defining a function of the gene product essential for the early stages of embryonic development. Preliminary results show strikingly distinct spatial and temporal patterns of expression of the two isoforms at later stages of development.
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    Studies on the activity ofKluyveromyces lactis S-adenosylmethionine: Δ 24-sterol methyltransferase in presence of polyenic antifungal agents (1994)
    Springer
    Mycopathologia 126 (1994), S. 75-83 
    Details
    ISSN: 1573-0832
    Keywords: Ergosterol synthesis ; Polyenic antifungal agents ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The S-adenosylmethionine: Δ 24-sterol methyltransferase (24 SMT) primarily considered as a mitochondrial enzyme, was recently mainly detected in lipid particles of yeasts. It catalyses the methylation of zymosterol which is an essential reaction for the synthesis of ergosterol. We have investigated in cellular extracts of twoKluyveromyces lactis strains the action of polyenic antifungal agents on the activity of this enzyme. Low concentrations of amphotericin B, candicidin and pimaricin strongly stimulate this activity, while high concentrations inhibit it or have no effect. Whatever the doses used, nystatin and filipin had no significant influence on this activity. According to the molar ratio amphotericin B/total sterols of the enzyme preparation, the interference of amphotericin B on the 24 SMT activity may result of two mechanisms.
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    Conserving genetic variability of a wild insect population under laboratory conditions (1993)
    Springer
    Entomologia experimentalis et applicata 67 (1993), S. 233-239 
    Details
    ISSN: 1570-7458
    Keywords: inbreeding ; colonization ; isofemale line ; Drosophila ; Diptera ; Leptopilina boulardi ; Cynipidae ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé D. melanogaster (Meigen) a été utilisé pour tester la capacité des lignées isofemelles à conserver la variabilité génétique d'une population naturelle. Deux types d'expériences ont été réalisées. L'une a consisté à déterminer la variabilité génétique de 3 locus enzymatiques pour 32 lignées isofemelles à la première et à la 23ème génération d'élevage au laboratoire. L'autre a consisté à tester la capacité des larves à éliminer un parasitoïde par le processus d'encapsulation après 8 années d'élevage au laboratoire. D'une façon générale, certaines lignées isofemelles perdent de la variabilité durant les 23 générations de l'étude. Mais la fréquence globale des allèles reste inchangée si l'on considère l'ensemble des 32 lignées. Le seul allèle rare observé a également été conservé. Les modifications des fréquences allèliques à chacun des locus ont lieu de façon indépendante les unes des autres. La variabilité génétique d'un caractère biologique, la capacité des larves à encapsuler le parasitoïde, a également varié, mais elle a pu être restaurée à un niveau proche de la population initiale en rassemblant plusieurs individus de chacune des lignées.
    Notes: Abstract Drosophila melanogaster (Meigen) was used to test the power of isofemale lines in preserving genetic variability. We performed experiments in two ways. One series consisted of measuring the genetic variability for three enzymatic loci in 32 isofemale lines, in the first and 23rd generations of culture. In the second series, we tested the capacity of the larvae to eliminate a parasitoid by encapsulation after eight years of laboratory breeding. In general, individual isofemale lines appeared to change during the 23 generations of the study, but the global frequency of these alleles among the 32 isofemale lines stayed relatively unchanged. The only rare allele observed was also conserved. Changes in allozyme frequencies at any one locus were independent of those at other loci. Genetic variation of a biological trait, the capacity of the larvae to encapsulate a parasitoid, also changed, but it could be restored to a level close to that of the starting population by mass hybridizing together individuals of each line.
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    Responses of a generalist and a specialist parasitoid (Hymenoptera: Eucoilidae) to Drosophilid larval kairomones (1993)
    Springer
    Journal of insect behavior 6 (1993), S. 615-624 
    Details
    ISSN: 1572-8889
    Keywords: Hymenoptera ; Leptopilina ; Drosophila ; semiochemicals ; kairomones ; parasitoid ; generalist ; specialist ; foraging behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Foraging parasitoids are thought to need more specific information than generalists on the presence, identity, availability, and suitability of their insect host species. In the present paper, we compare responses to host kairomones by two phylogenetically related parasitoid species that attack Drosophilidae and that differ in the width of their host range. As predicted, the behavioral response of the parasitoids to host kairomones reflected their difference in host range. The response of the specialist parasitoid Leptopilina boulardiwas restricted to contact kairomones from its natural hosts and one closely related species. In contrast, the generalist parasitoid Leptopilina heterotomaresponded to contact kairomones of a variety of Drosophilidae species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048127
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  • 97
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    Sexual isolation betweenDrosophila melanogaster females andD. simulans males. Male mating propensities versus success in hybridization (1993)
    Springer
    Cellular and molecular life sciences 49 (1993), S. 596-598 
    Details
    ISSN: 1420-9071
    Keywords: Drosophila ; hybridization ; male vigour ; male mating speed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Genetic variation has been found in males of aD. simulans population for their eagerness to hybridize withD. melanogaster females. In a search for traits involved in this hybridization, males ofD. simulans were tested for mating speed and sexual vigour. Between-male differences were detected in both sexual traits, but no relationship was noticed between them, nor with the frequency of hybridization. Thus male mating propensities appear to be unrelated to the breakdown of sexual isolation between these sibling species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01955171
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  • 98
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    Colocalization of cholesterol and hydroxyapatite in human atherosclerotic lesions (1993)
    Springer
    Calcified tissue international 52 (1993), S. 94-98 
    Details
    ISSN: 1432-0827
    Keywords: Atherosclerosis ; Calcification ; Hydroxyapatite ; Cholesterol ; Filipin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cholesterol and calcium phosphate, the latter in the form of hydroxyapatite, accumulate in atherosclerotic lesions. In this report, we demonstrate that these organic and inorganic constitutents of lesions can accumulate together, closely associated in crystal agglomerates. Using the fluorescent cholesterol probe, filipin, we identified unesterified cholesterol that was associated with calcium granules in tissue sections of lesions. We also have shown that small crystallites of cholesterol can associate with preformed hydroxyapatite crystals in vitro. Scanning electron microscopy couple with energy-dispersive X-ray analysis demonstrated the physical association of many small crystallites of cholesterol with larger crystals of hydroxyapatite. These small crystallites of cholesterol associated with hydroxyapatite stained with filipin. This contrasted with the lack of filipin staining of unassociated larger cholesterol crystals or hydroxyapatite alone. How cholesterol and calcium come to be closely associated in crystal agglomerates within atherosclerotic lesions remains to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308315
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  • 99
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    Homopolymer length variation in the Drosophila gene mastermind (1993)
    Springer
    Journal of molecular evolution 37 (1993), S. 483-495 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; mastermind ; Gene comparison ; Triplet repeat ; Homopolymer ; Protein evolution ; Repeat length variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Runs of identical amino acids encoded by triplet repeats (homopolymers) are components of numerous proteins, yet their role is poorly understood. Large numbers of homopolymers are present in the Drosophila melanogaster mastermind (mam) protein surrounding several unique charged amino acid clusters. Comparison of mam sequences from D. virilis and D. melanogaster reveals a high level of amino acid conservation in the charged clusters. In contrast, significant divergence is found in repetitive regions resulting from numerous amino acid replacements and large insertions and deletions. It appears that repetitive regions are under less selective pressure than unique regions, consistent with the idea that homopolymers act as flexible spacers separating functional domains in proteins. Notwithstanding extensive length variation in intervening homopolymers, there is extreme conservation of the amino acid spacing of specific charge clusters. The results support a model where homopolymer length variability is constrained by natural selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160429
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  • 100
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    Molecular phylogeny of Drosophila based on ribosomal RNA sequences (1993)
    Springer
    Journal of molecular evolution 37 (1993), S. 525-543 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; Zaprionus ; Phylogeny ; Ribosomal RNA sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nucleotide sequences of 72 species of Drosophilidae were determined for divergent D1 and D2 domains (representing 200 and 341 nucleotides respectively in D. melanogaster) of large ribosomal RNA, using the rRNA direct sequencing method. Molecular phylogenetic trees were reconstructed using both distance and parsimony methods and the robustness of the nodes was evaluated by the bootstrap procedure. The trees obtained by these methods revealed four main lineages or clades which do not correspond to the taxonomical hierarchy. In our results, the genus Chymomyza is associated with the subgenus Scaptodrosophila of the genus Drosophila and their cluster constitutes the most ancient clade. The two other clades are constituted of groups belonging to the subgenus Sophophora of the genus Drosophila: the so-called Neotropical clade including the willistoni and saltans groups and the obscura-melanogaster clade itself split into three lineages: (1) obscura group + ananassae subgroup, (2) montium subgroup, and (3) melanogaster + Oriental subgroups. The fourth clade, the Drosophila one, contains three lineages. D. polychaeta, D. iri, and D. fraburu are branched together and constitute the most ancient lineage; the second lineage includes the annulimana, bromeliae, dreyfusi, melanica, mesophragmatica, repleta, robusta, and virilis groups. The third lineage is composed of the immigrans and the cardini, funebris, guaramunu, guarani, histrio, pallidipennis, quinaria, and tripunctata groups. The genera Samoaia, Scaptomyza, and Zaprionus are branched within the Drosophila clade. Although these four clades appear regularly in almost all tree calculations, additional sequencing will be necessary to determine their precise relationships.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160433
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