The trace biogenic amine tyramine is present in the nervous systems of animals ranging in complexity from nematodes to mammals. Tyramine is synthesized from tyrosine by the enzyme tyrosine decarboxylase (TDC), a member of the aromatic amino acid family, but this enzyme has not been identified in Drosophila or in higher animals. To further clarify the roles of tyramine and its metabolite octopamine, we have cloned two TDC genes from Drosophila melanogaster, dTdc1 and dTdc2. Although both gene products have TDC activity in vivo, dTdc1 is expressed nonneurally, whereas dTdc2 is expressed neurally. Flies with a mutation in dTdc2 lack neural tyramine and octopamine and are female sterile due to egg retention. Although other Drosophila mutants that lack octopamine retain eggs completely within the ovaries, dTdc2 mutants release eggs into the oviducts but are unable to deposit them. This specific sterility phenotype can be partially rescued by driving the expression of dTdc2 in a dTdc2-specific pattern, whereas driving the expression of dTdc1 in the same pattern results in a complete rescue. The disparity in rescue efficiencies between the ectopically expressed Tdc genes may reflect the differential activities of these gene products. The egg retention phenotype of the dTdc2 mutant and the phenotypes associated with ectopic dTdc expression contribute to a model in which octopamine and tyramine have distinct and separable neural activities.Tyramine, octopamine, and other "trace" biogenic amines are found in most organisms, including bacteria, fungi, and plants, and in animals ranging in complexity from nematodes to mammals. Despite their wide distribution, the biological roles of trace amines are poorly understood. In vertebrates, trace amines are present in low levels and can displace classical biogenic amines from their stores and stimulate outward neurotransmitter efflux from biogenic amine transporters (1). Although there are currently no data to suggest that there are dedicated synapses for trace amines in the brain, the recent discovery of G-protein-coupled receptors that are selectively Additionally, tyramine affects chloride permeability in the Drosophila Malpighian tubule (7), relaxation of muscle tone in the locust oviduct (8), and behavioral responses to cocaine in Drosophila (9).Octopamine in invertebrates is often considered to be the functional homolog of vertebrate norepinephrine and is involved in a diverse range of physiological processes (reviewed in Ref. 10), including Drosophila female fertility. Flies that lack a functional octopamine receptor or cannot synthesize octopamine due to a null allele of tyramine ␤-hydroxylase (T␤h) 2 show a complete egg retention phenotype (11-13). The sterility of T␤h null females is due to a defect in ovulation, which can be rescued by octopamine feeding or by driving the ectopic expression of a T␤h transgene in several driver lines that show overlapping expression in the thoracic tip of the CNS (12, 13).The first step in octopamine biosynthesis is catalyzed by tyrosine...

BackgroundIn many taxa, males and females are very distinct phenotypically, and these differences often reflect divergent selective pressures acting on the sexes. Phenotypic sexual dimorphism almost certainly reflects differing patterns of gene expression between the sexes, and microarray studies have documented widespread sexually dimorphic gene expression. Although the evolutionary significance of sexual dimorphism in gene expression remains unresolved, these studies have led to the formulation of a hypothesis that male-driven evolution has resulted in the masculinization of animal transcriptomes. Here we use a microarray assessment of sex- and gonad-biased gene expression to test this hypothesis in zebrafish.ResultsBy using zebrafish Affymetrix microarrays to compare gene expression patterns in male and female somatic and gonadal tissues, we identified a large number of genes (5899) demonstrating differences in transcript abundance between male and female Danio rerio. Under conservative statistical significance criteria, all sex-biases in gene expression were due to differences between testes and ovaries. Male-enriched genes were more abundant than female-enriched genes, and expression bias for male-enriched genes was greater in magnitude than that for female-enriched genes. We also identified a large number of genes demonstrating elevated transcript abundance in testes and ovaries relative to male body and female body, respectively.ConclusionOverall our results support the hypothesis that male-biased evolutionary pressures have resulted in male-biased patterns of gene expression. Interestingly, our results seem to be at odds with a handful of other microarray-based studies of sex-specific gene expression patterns in zebrafish. However, ours was the only study designed to address this specific hypothesis, and major methodological differences among studies could explain the discrepancies. Regardless, all of these studies agree that transcriptomic sex differences in D. rerio are widespread despite the apparent absence of heterogamety. These differences likely make important contributions to phenotypic sexual dimorphism in adult zebrafish; thus, from an evolutionary standpoint, the precise roles of sex-specific selection and sexual conflict in the evolution of sexually dimorphic gene expression are very important. The results of our study and others like it set the stage for further work aimed at directly addressing this exciting issue in comparative genomics.

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Background: The actions and reactions integral to mate recognition and reproduction are examples of multifaceted behaviors for which we are only beginning to comprehend the underlying genetic and molecular complexity. I hypothesized that social interactions, such as those involved in reproductive behaviors, would lead to immediate and assayable changes in gene expression. Such changes may have important effects on individual reproductive success and fitness through alterations in physiology or via short-term or long-term changes in nervous system function.

The p24 transmembrane proteins, also known as EMP24/GP25 (endomembrane protein precursor of 24kD (Schimmoller et al., 1995)) proteins, are components of coat protein (COP)-coated vesicles and are present in species as diverse as fungi, plants, flies, worms, and mammals, indicating that they have important conserved functions. Genetic, molecular, and biochemical characterization of these proteins and the loci that encode them has provided insights into their potential cellular roles, including postulated functions in vesicle cargo protein selection and sorting, COPI and COPII vesicle formation and budding, and quality control of proteins that mature through the secretory pathway. Recently, the first mutations in a Drosophila melanogaster p24 gene have been isolated and characterized. These alleles produce an interesting behavioral phenotype in females, affecting their ability to oviposit. This identification and mutant characterization of a p24 locus in Drosophila will pave the way for a better understanding of cell-type-specific functions and interactions among p24 proteins.

The steroid hormone ecdysone triggers transitions between developmental stages in Drosophila by acting through a heterodimer consisting of the EcR and USP nuclear receptors. The EcR gene encodes three protein isoforms (EcR-A, EcR-B1, and EcR-B2) that have unique amino termini but that contain a common carboxy-terminal region including DNA-binding and ligand-binding domains. EcR-A and EcR-B1 are expressed in a spatially complementary pattern at the onset of metamorphosis, suggesting that specific responses to ecdysone involve distinct EcR isoforms. Here, we describe phenotypes of EcR-A specific deletion mutants isolated using transposon mutagenesis. Western blot analysis shows that each of these mutants completely lacks EcR-A protein, while the EcR-B1 protein is still present. The EcR(112) strain has a deletion of EcR-A specific non-coding and regulatory sequences but retains the coding exons, while the EcR(139) strain has a deletion of EcR-A specific protein coding exons but retains the regulatory region. In these mutants, the developmental progression of most internal tissues that normally express EcR-B1 is unaffected by the lack of EcR-A. Surprisingly, however, we found that one larval tissue, the salivary gland, fails to degenerate even though EcR-B1 is the predominant isoform. This result may indicate that the low levels of EcR-A in this tissue are in fact required. We identified yet another type of mutation, the EcR(94) deletion, that removes the EcR-A specific protein coding exons as well as the introns between the EcR-A and EcR-B transcription start sites. This deletion places the EcR-A regulatory region adjacent to the EcR-B transcription start site. While EcR(112) and EcR(139) mutant animals die during mid and late pupal development, respectively, EcR(94) mutants arrest prior to pupariation. EcR-A mutant phenotypes and lethal phases differ from those of EcR-B mutants, suggesting that the EcR isoforms have distinct developmental functions.

Genes encoding members of the p24 family of intracellular trafficking proteins are present throughout animal and plant lineages. However, very little is known about p24 developmental, spatial, or sex-specific expression patterns or how localized expression affects function. We investigated these problems in Drosophila melanogaster, which contains nine genes encoding p24 proteins. One of these genes, logjam (loj), is expressed in the adult female nervous system and ovaries and is essential for oviposition. Nervous system-specific expression of loj, but not ovary-specific expression, rescues the behavioral defect of mutants. The Loj protein localizes to punctate structures in the cellular cytoplasm. These structures colocalize with a marker specific to the intermediate compartment and cis-Golgi, consistent with experimental evidence from other systems suggesting that p24 proteins function in intracellular transport between the endoplasmic reticulum and Golgi. Our findings reveal that Drosophila p24 transcripts are developmentally and tissue-specifically expressed. CG31787 is male-specifically expressed gene that is present during the larval, pupal, and adult stages. Female CG9053 mRNA is limited to the head, whereas males express this gene widely. Together, our studies provide experimental evidence indicating that some p24 genes have sex-specific expression patterns and tissue-and sex-limited functions. Developmental Dynamics 236:544 -555, 2007.

Response to the steroid hormone ecdysone in Drosophila is controlled by genetic regulatory hierarchies that include eight members of the nuclear receptor protein family. The DHR3 gene, located within the 46F early-late ecdysoneinducible chromosome puff, encodes an orphan nuclear receptor that recently has been shown to exert both positive and negative regulatory effects in the ecdysone-induced genetic hierarchies at metamorphosis. We used a reverse genetics approach to identify 11 DHR3 mutants from a pool of lethal mutations in the 46F region on the second chromosome. Two DHR3 mutations result in amino acid substitutions within the conserved DNA binding domain. Analysis of DHR3 mutants reveals that DHR3 function is required to complete embryogenesis. All DHR3 alleles examined result in nervous system defects in the embryo.