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L J Zwiebel

Publications and source records attributed to L J Zwiebel.

At least 19 recordsLinked to original sources
PubMed2005

Molecular biology of insect olfaction: recent progress and conceptual models.

Insects have an enormous impact on global public health as disease vectors and as agricultural enablers as well as pests and olfaction is an important sensory input to their behavior. As such it is of great value to understand the interplay of the molecular components of the olfactory system which, in addition to fostering a better understanding of insect neurobiology, may ultimately aid in devising novel intervention strategies to reduce disease transmission or crop damage. Since the first discovery of odorant receptors in vertebrates over a decade ago, much of our view on how the insect olfactory system might work has been derived from observations made in vertebrates and other invertebrates, such as lobsters or nematodes. Together with the advantages of a wide range of genetic tools, the identification of the first insect odorant receptors in Drosophila melanogaster in 1999 paved the way for rapid progress in unraveling the question of how olfactory signal transduction and processing occurs in the fruitfly. This review intends to summarize much of this progress and to point out some areas where advances can be expected in the near future.

Animals↗
PubMed2005

Odorant-specific requirements for arrestin function in Drosophila olfaction.

The ability to modulate olfactory sensitivity is necessary to detect chemical gradients and discriminate among a multitude of odor stimuli. Desensitization of odorant receptors has been postulated to occur when arrestins prevent the activation of downstream second messengers. A paucity of in vivo data on olfactory desensitization prompts use of Drosophila melanogaster genetics to investigate arrestins' role in regulating olfactory signaling pathways. Physiological analysis of peripheral olfactory sensitivity reveals decreased responsiveness to a host of chemically distinct odorants in flies deficient for arrestin1 (arr1), arrestin2 (arr2), or both. These phenotypes are manifest in odorant- and dose- dependent fashions. Additionally, mutants display altered adaptive properties under a prolonged exposure paradigm. Behaviorally, arr1 mutants are impaired in olfactory-based orientation towards attractive odor sources. As the olfactory deficits vary according to chemical identity and concentration, they indicate that a spectrum of arrestin activity is essential for odor processing depending upon the particular olfactory pathway involved. Arrestin mutant phenotypes are hypothesized to be a consequence of down-regulation of olfactory signaling to avoid cellular excitotoxicity. Importantly, phenotypic rescue of olfactory defects in arr1(1) mutants is achieved through transgenic expression of wild-type arr1. Taken together, these data clearly indicate that arrestins are required in a stimulus-specific manner for wild type olfactory function and add another level of complexity to peripheral odor coding mechanisms that ultimately impact olfactory behavior.

Acetates↗
PubMed2004

Olfactory regulation of mosquito-host interactions.

Mosquitoes that act as disease vectors rely upon olfactory cues to direct several important behaviors that are fundamentally involved in establishing their overall vectorial capacity. Of these, the propensity to select humans for blood feeding is arguably the most important of these olfactory driven behaviors in so far as it significantly contributes to the ability of these mosquitoes to transmit pathogens that cause diseases such as dengue, yellow fever and most significantly human malaria. Here, we review significant advances in behavioral, physiological and molecular investigations into mosquito host preference, with a particular emphasis on studies that have emerged in the post-genomic era that seek to combine these approaches.

Animals↗
PubMed2003

Identification of a distinct family of genes encoding atypical odorant-binding proteins in the malaria vector mosquito, Anopheles gambiae.

We performed a genome-wide analysis for candidate odorant-binding protein (OBP) genes in the malaria vector Anopheles gambiae (Ag). We identified fifty-seven putative genes including sixteen genes predicted to encode distinct, higher molecular weight proteins that lack orthologues in Drosophila. Expression analysis indicates that several of these atypical AgOBPs are transcribed in chemosensory organs in adult and immature stages. Phylogenetic analysis of the Anopheles and Drosophila OBP families reveals these proteins fall into several clusters based on sequence similarity and suggests the atypical AgOBP genes arose in the mosquito lineage after the divergence of mosquitoes and flies. The identification of these AgOBP genes is the first step towards determining their biological roles in this economically and medically important insect.

Amino Acid Sequence↗
PubMed2003

Molecular characterization of arrestin family members in the malaria vector mosquito, Anopheles gambiae.

Olfaction influences many insect behaviours including mate seeking and host selection. The molecular machinery underlying insect olfactory systems is a G protein-coupled receptor pathway that, in addition to activation, requires adaptation for olfactory sensitivity and discrimination. We have previously identified ARR1 (henceforth AgARR1), a sensory arrestin from the malaria vector mosquito Anopheles gambiae that has been postulated to modulate olfactory adaptation. This report describes three additional arrestin family members including ARR2 (henceforth AgARR2), which is similar to previously characterized insect sensory arrestins and is expressed at significantly higher levels in the antennae of male vs. female A. gambiae mosquitoes. This finding is consistent with the hypothesis that AgARR2 may be important for the regulation of olfactory-driven behaviours particular to male mosquitoes.

Amino Acid Sequence↗
PubMed2002

Visual arrestins in olfactory pathways of Drosophila and the malaria vector mosquito Anopheles gambiae.

Arrestins are important components for desensitization of G protein-coupled receptor cascades that mediate neurotransmission as well as olfactory and visual sensory reception. We have isolated AgArr1, an arrestin-encoding cDNA from the malaria vector mosquito, Anopheles gambiae, where olfaction is critical for vectorial capacity. Analysis of AgArr1 expression revealed an overlap between chemosensory and photoreceptor neurons. Furthermore, an examination of previously identified arrestins from Drosophila melanogaster exposed similar bimodal expression, and Drosophila arrestin mutants demonstrate impaired electrophysiological responses to olfactory stimuli. Thus, we show that arrestins in Drosophila are required for normal olfactory physiology in addition to their previously described role in visual signaling. These findings suggest that individual arrestins function in both olfactory and visual pathways in Dipteran insects; these genes may prove useful in the design of control strategies that target olfactory-dependent behaviors of insect disease vectors.

Amino Acid Sequence↗
PubMed2002

A cluster of candidate odorant receptors from the malaria vector mosquito, Anopheles gambiae.

Olfaction is critical to the host preference selection behavior of many disease-transmitting insects, including the mosquito Anopheles gambiae sensu stricto (hereafter A. gambiae), one of the major vectors for human malaria. In order to more fully understand the molecular biology of olfaction in this insect, we have previously identified several members member of a family of candidate odorant receptor proteins from A. gambiae (AgORs). Here we report the cloning and characterization of an additional AgOR gene, denoted as AgOr5, which shows significant similarity to putative odorant receptors in A. gambiae and Drosophila melanogaster and which is selectively expressed in olfactory organs. AgOr5 is tightly clustered within the A. gambiae genome to two other highly homologous candidate odorant receptors, suggesting that these genes are derived from a common ancestor. Analysis of the developmental expression within members of this AgOR gene cluster reveals considerable variation between these AgORs as compared to candidate odorant receptors from D. melanogaster.

Amino Acid Sequence↗
PubMed2001

Candidate odorant receptors from the malaria vector mosquito Anopheles gambiae and evidence of down-regulation in response to blood feeding.

Olfaction plays a major role in host preference and blood feeding, integral behaviors for disease transmission by the malaria vector mosquito Anopheles gambiae sensu stricto (henceforth A. gambiae). We have identified four genes encoding candidate odorant receptors from A. gambiae that are selectively expressed in olfactory organs, contain approximately seven transmembrane domains, and show significant similarity to several putative odorant receptors in Drosophila melanogaster. Furthermore, one of the putative A. gambiae odorant receptors exhibits female-specific antennal expression and is down-regulated 12 h after blood feeding, a period during which substantial reduction in olfactory responses to human odorants has been observed. Taken together, these data suggest these genes encode a family of odorant receptors in A. gambiae, whose further study may aid in the design of novel antimalarial programs.

Amino Acid Sequence↗
PubMed2001

Genomic organization and characterization of the white locus of the Mediterranean fruitfly, Ceratitis capitata.

An approximately 14-kb region of genomic DNA encoding the wild-type white eye (w+) color gene from the medfly, Ceratitis capitata has been cloned and characterized at the molecular level. Comparison of the intron-exon organization of this locus among several dipteran insects reveals distinct organizational patterns that are consistent with the phylogenetic relationships of these flies and the dendrogram of the predicted primary amino acid sequence of the white loci. An examination of w+ expression during medfly development has been carried out, displaying overall similarity to corresponding studies for white gene homologues in Drosophila melanogaster and other insects. Interestingly, we have detected two phenotypically neutral allelic forms of the locus that have arisen as the result of an apparently novel insertion or deletion event located in the large first intron of the medfly white locus. Cloning and sequencing of two mutant white alleles, w1 and w2, from the we,wp and M245 strains, respectively, indicate that the mutant conditions in these strains are the result of independent events--a frameshift mutation in exon 6 for w1 and a deletion including a large part of exon 2 in the case of w2.

Alleles↗
PubMed2001

Isolation and characterization of the Xanthine dehydrogenase gene of the Mediterranean fruit fly, Ceratitis capitata.

Xanthine dehydrogenase (XDH) is a member of the molybdenum hydroxylase family of enzymes catalyzing the oxidation of hypoxanthine and xanthine to uric acid. The enzyme is also required for the production of one of the major Drosophila eye pigments, drosopterin. The XDH gene has been isolated in many species representing a broad cross section of the major groups of living organisms, including the cDNA encoding XDH from the Mediterranean fruit fly Ceratitis capitata (CcXDH) described here. CcXDH is closely related to other insect XDHs and is able to rescue the phenotype of the Drosophila melanogaster XDH mutant, rosy, in germline transformation experiments. A previously identified medfly mutant, termed rosy, whose phenotype is suggestive of a disruption in XDH function, has been examined for possible mutations in the XDH gene. However, we find no direct evidence that a mutation in the CcXDH gene or that a reduction in the CcXDH enzyme activity is present in rosy medflies. Conclusive studies of the nature of the medfly rosy mutant will require rescue by germline transformation of mutant medflies.

Amino Acid Sequence↗
PubMed1995

The white gene of Ceratitis capitata: a phenotypic marker for germline transformation.

Reliable germline transformation is required for molecular studies and ultimately for genetic control of economically important insects, such as the Mediterranean fruit fly (medfly) Ceratitis capitata. A prerequisite for the establishment and maintenance of transformant lines is selectable or phenotypically dominant markers. To this end, a complementary DNA clone derived from the medfly white gene was isolated, which showed substantial similarity to white genes in Drosophila melanogaster and other Diptera. It is correlated with a spontaneous mutation causing white eyes in the medfly and can be used to restore partial eye color in transgenic Drosophila carrying a null mutation in the endogenous white gene.

ATP-Binding Cassette Transporters↗
PubMed1994

Temporal phosphorylation of the Drosophila period protein.

The period gene (per) is required for Drosophila melanogaster to manifest circadian (congruent to 24 hr) rhythms. We report here that per protein (PER) undergoes daily oscillations in apparent molecular mass as well as abundance. The mobility changes are largely or exclusively due to multiple phosphorylation events. The temporal profile of the classic short-period form of PER (PERS) is altered in a manner consistent with the mutant strain's behavioral phenotype. As changes in abundance and phosphorylation persist under constant environmental conditions, they reflect or contribute to a free-running rhythm. We suggest that the phosphorylation status of PER is an important determinant in the Drosophila clock's time-keeping mechanism.

Animals↗
PubMed1992

The period gene encodes a predominantly nuclear protein in adult Drosophila.

The period gene of Drosophila melanogaster (per) is important for the generation and maintenance of biological rhythms. Previous light microscopic observations indicated that per is expressed in a variety of tissues and cell types and suggested that the per protein (PER) may be present in different subcellular compartments. To understand how PER influences circadian rhythms, it is important to define its subcellular location, especially in adult flies where inducible promoter experiments suggested that it is most relevant to circadian locomotor activity rhythms. To this end, we report the results of an immunoelectron microscopic analysis of wild-type flies and per-beta-galactosidase (beta-gal) fusion gene transgenics using a polyclonal anti-PER antibody or an anti-beta-gal antibody, respectively. Most of the PER antigen and the fusion gene product were located within nuclei, suggesting that PER acts in that subcellular compartment to affect circadian rhythms. The results are discussed in terms of per's possible biochemical functions.

Animals↗
PubMed1991

A post-transcriptional mechanism contributes to circadian cycling of a per-beta-galactosidase fusion protein.

The period gene (per) of Drosophila melanogaster affects circadian rhythms. Circadian fluctuations in per mRNA levels are thought to contribute to circadian fluctuations in per protein levels in the heads of adult flies. To address the mechanisms underlying these oscillatory phenomena, we have analyzed RNA and protein cycling from two per-beta-galactosidase fusion genes. These studies demonstrate that 5' noncoding sequences from per are sufficient to cause the fusion mRNA levels to cycle in a wild-type (rhythmic) background. Protein cycling requires additional sequences derived from the per coding region. The data suggest that there is a per-dependent posttranscriptional mechanism that is under circadian clock control required for per protein levels to fluctuate in a rhythmic fashion.

Animals↗
PubMed1991

The strength and periodicity of D. melanogaster circadian rhythms are differentially affected by alterations in period gene expression.

The per gene of D. melanogaster influences or participates in the generation of biological rhythms. Previous experiments have identified the head as the location from which per exerts its effect on circadian rhythms. To localize further this region and to examine the effects of altered levels and altered spatial expression patterns of the per gene on circadian rhythms of locomotor activity, we have characterized transformed lines containing per gene constructs missing substantial cis-acting regulatory information. The data suggest that wild-type levels of per gene expression are necessary in only a small fraction of the nervous system for near wild-type periods, whereas a larger fraction of per-expressing cells in the brain contributes to the strength of the circadian rhythms.

Animals↗
PubMed1989

A new mutation at the period locus of Drosophila melanogaster with some novel effects on circadian rhythms.

A new period mutation has been induced and characterized in D. melanogaster. It causes flies to be apparently arrhythmic in tests of locomotor activity and thus is superficially similar to the original per01 mutant. Yet, the new "zero" allele, per04, has some novel properties and effects: Behaviorally, per04 adults often exhibit weak, long-period rhythms of locomotor activity in constant darkness; this low-frequency rhythmicity usually was not obvious in the analog behavioral records but was readily revealed by spectral analyses. These treatments of the data also extracted hidden high-frequency (ultradian) rhythms in many of the behavioral records, of the type associated with per01 and other per-nulls. The wide range of periodicities exhibited by different per04-expressing flies implies the expression of multiple oscillatory modes by this mutant. The new mutation also leads to a tendency for flies to be hyperactive during activity monitoring and is thus dissimilar to the other arrhythmic variants in the per gene but similar to the effects of a deletion of the locus. During light:dark cycling, per04 adults once more behave differently from other per0's and in fact tend to resemble wild-type flies in these conditions. The new mutation is not caused by the same nucleotide substitution that created a stop codon in the original arrhythmic per mutant and, as it turns out, per02 and per03 as well. per04 is also not a null variant at the transcriptional level; but it leads to an anomalous form of per mRNA, which is smaller than the normal 4.5 kb species encoded by this clock gene.

Alleles↗
PubMed1986

Germ-line transformation involving DNA from the period locus in Drosophila melanogaster: overlapping genomic fragments that restore circadian and ultradian rhythmicity to per0 and per- mutants.

P-element-mediated transformations involving DNA fragments from the period (per) clock gene of Drosophila melanogaster have shown that several subsegments of the locus restore rhythmicity to per0 or per- mutants. Such fragments overlap in a genomic region complementary to one transcript, a 4.5-kb RNA which is probably the per message, in that it is necessary and (in terms of expression from this X-chromosomal locus) sufficient for the fly's circadian rhythms. It is also at least necessary for the high-frequency oscillations normally produced by courting males as they vibrate their wings. The entirety of the 4.5-kb transcript is not necessary for rather strong rhythmicity; nor does it seem to be sufficient, in transformants, for wild-type behavioral phenotypes. A 0.9-kb RNA, homologous to genomic region immediately adjacent to the source of the 4.5-kb species, oscillates in its abundance over the course of a day; but coverage of this transcript source in several transformants carrying a per0 mutation--which eliminates the 0.9-kb RNA's oscillation--does not restore rhythmicity. All of the independently isolated arrhythmic mutations tested were covered by the same array of overlapping per+-derived DNA fragments, implying that the only portion of the locus which has mutated to arrhythmicity is complementary to the 4.5-kb transcript.

Animals↗