RESUMEN
Barrier epithelial organs face the constant challenge of sealing the interior body from the external environment while simultaneously replacing the cells that contact this environment. New replacement cells-the progeny of basal stem cells-are born without barrier-forming structures such as a specialized apical membrane and occluding junctions. Here, we investigate how new progeny acquire barrier structures as they integrate into the intestinal epithelium of adult Drosophila. We find they gestate their future apical membrane in a sublumenal niche created by a transitional occluding junction that envelops the differentiating cell and enables it to form a deep, microvilli-lined apical pit. The transitional junction seals the pit from the intestinal lumen until differentiation-driven, basal-to-apical remodelling of the niche opens the pit and integrates the now-mature cell into the barrier. By coordinating junctional remodelling with terminal differentiation, stem cell progeny integrate into a functional, adult epithelium without jeopardizing barrier integrity.
Asunto(s)
Mucosa Intestinal , Intestinos , Epitelio , Membrana Celular , Mucosa Intestinal/metabolismo , Células Madre/metabolismoRESUMEN
Genetically wired neural mechanisms inhibit mating between species because even naive animals rarely mate with other species. These mechanisms can evolve through changes in expression or function of key genes in sensory pathways or central circuits. Gr32a is a gustatory chemoreceptor that, in D. melanogaster, is essential to inhibit interspecies courtship and sense quinine. Similar to D. melanogaster, we find that D. simulans Gr32a is expressed in foreleg tarsi, sensorimotor appendages that inhibit interspecies courtship, and it is required to sense quinine. Nevertheless, Gr32a is not required to inhibit interspecies mating by D. simulans males. However, and similar to its function in D. melanogaster, Ppk25, a member of the Pickpocket family, promotes conspecific courtship in D. simulans. Together, we have identified distinct evolutionary mechanisms underlying chemosensory control of taste and courtship in closely related Drosophila species.
Asunto(s)
Evolución Biológica , Cortejo/psicología , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/fisiología , Drosophila simulans/fisiología , Receptores de Superficie Celular/metabolismo , Conducta Sexual Animal , Gusto/fisiología , Animales , Comunicación Celular , Células Quimiorreceptoras , Proteínas de Drosophila/genética , Femenino , Masculino , Feromonas , Receptores de Superficie Celular/genética , ReproducciónRESUMEN
Living in a social environment requires the ability to respond to specific social stimuli and to incorporate information obtained from prior interactions into future ones. One of the mechanisms that facilitates social interaction is pheromone-based communication. In Drosophila melanogaster, the male-specific pheromone cis-vaccenyl acetate (cVA) elicits different responses in male and female flies, and functions to modulate behavior in a context and experience-dependent manner. Although it is the most studied pheromone in flies, the mechanisms that determine the complexity of the response, its intensity and final output with respect to social context, sex and prior interaction, are still not well understood. Here we explored the functional link between social interaction and pheromone-based communication and discovered an odorant binding protein that links social interaction to sex specific changes in cVA related responses. Odorant binding protein 69a (Obp69a) is expressed in auxiliary cells and secreted into the olfactory sensilla. Its expression is inversely regulated in male and female flies by social interactions: cVA exposure reduces its levels in male flies and increases its levels in female flies. Increasing or decreasing Obp69a levels by genetic means establishes a functional link between Obp69a levels and the extent of male aggression and female receptivity. We show that activation of cVA-sensing neurons is sufficeint to regulate Obp69a levels in the absence of cVA, and requires active neurotransmission between the sensory neuron to the second order olfactory neuron. The cross-talk between sensory neurons and non-neuronal auxiliary cells at the olfactory sensilla, represents an additional component in the machinery that promotes behavioral plasticity to the same sensory stimuli in male and female flies.
Asunto(s)
Acetatos/farmacología , Proteínas de Drosophila/metabolismo , Ácidos Oléicos/farmacología , Feromonas/farmacología , Receptores Odorantes/metabolismo , Conducta Sexual Animal/efectos de los fármacos , Medio Social , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Drosophila melanogaster/fisiología , Femenino , Regulación de la Expresión Génica , Masculino , Receptores Odorantes/genética , Sensilos/metabolismo , Sensilos/fisiología , Células Receptoras Sensoriales/metabolismo , Células Receptoras Sensoriales/fisiología , Factores Sexuales , OlfatoRESUMEN
Hunger is a complex motivational state that drives multiple behaviors. The sensation of hunger is caused by an imbalance between energy intake and expenditure. One immediate response to hunger is increased food consumption. Hunger also modulates behaviors related to food seeking such as increased locomotion and enhanced sensory sensitivity in both insects and vertebrates. In addition, hunger can promote the expression of food-associated memory. Although progress is being made, how hunger is represented in the brain and how it coordinates these behavioral responses is not fully understood in any system. Here, we use Drosophila melanogaster to identify neurons encoding hunger. We found a small group of neurons that, when activated, induced a fed fly to eat as though it were starved, suggesting that these neurons are downstream of the metabolic regulation of hunger. Artificially activating these neurons also promotes appetitive memory performance in sated flies, indicating that these neurons are not simply feeding command neurons but likely play a more general role in encoding hunger. We determined that the neurons relevant for the feeding effect are serotonergic and project broadly within the brain, suggesting a possible mechanism for how various responses to hunger are coordinated. These findings extend our understanding of the neural circuitry that drives feeding and enable future exploration of how state influences neural activity within this circuit.
Asunto(s)
Drosophila melanogaster/fisiología , Hambre , Animales , Proteínas de Drosophila/metabolismo , Conducta Alimentaria , Femenino , Privación de Alimentos , Canales Iónicos , Masculino , Memoria , Motivación , Neuronas Serotoninérgicas/fisiología , Canal Catiónico TRPA1 , Canales Catiónicos TRPC/metabolismoRESUMEN
Transgenesis in numerous eukaryotes has been facilitated by the use of site-specific integrases to stably insert transgenes at predefined genomic positions (landing sites). However, the utility of integrase-mediated transgenesis in any system is constrained by the limited number and variable expression properties of available landing sites. By exploiting the nonstandard recombination activity exhibited by a phiC31 integrase mutant, we developed a rapid and inexpensive method for isolating landing sites that exhibit desired expression properties. Additionally, we devised a simple technique for constructing arrays of transgenes at a single landing site, thereby extending the utility of previously characterized landing sites. Using the fruit fly Drosophila melanogaster, we demonstrate the feasibility of these approaches by isolating new landing sites optimized to express transgenes in the nervous system and by building fluorescent reporter arrays at several landing sites. Because these strategies require the activity of only a single exogenous protein, we anticipate that they will be portable to species such as nonmodel organisms, in which genetic manipulation is more challenging, expediting the development of genetic resources in these systems.
Asunto(s)
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Marcación de Gen/métodos , Integrasas/genética , Transgenes , Animales , Proteínas de Drosophila/metabolismo , Integrasas/metabolismoRESUMEN
The male-specific Fruitless proteins (FruM) act to establish the potential for male courtship behavior in Drosophila melanogaster and are expressed in small groups of neurons throughout the nervous system. We screened â¼1000 GAL4 lines, using assays for general courtship, male-male interactions, and male fertility to determine the phenotypes resulting from the GAL4-driven inhibition of FruM expression in subsets of these neurons. A battery of secondary assays showed that the phenotypic classes of GAL4 lines could be divided into subgroups on the basis of additional neurobiological and behavioral criteria. For example, in some lines, restoration of FruM expression in cholinergic neurons restores fertility or reduces male-male courtship. Persistent chains of males courting each other in some lines results from males courting both sexes indiscriminately, whereas in other lines this phenotype results from apparent habituation deficits. Inhibition of ectopic FruM expression in females, in populations of neurons where FruM is necessary for male fertility, can rescue female infertility. To identify the neurons responsible for some of the observed behavioral alterations, we determined the overlap between the identified GAL4 lines and endogenous FruM expression in lines with fertility defects. The GAL4 lines causing fertility defects generally had widespread overlap with FruM expression in many regions of the nervous system, suggesting likely redundant FruM-expressing neuronal pathways capable of conferring male fertility. From associations between the screened behaviors, we propose a functional model for courtship initiation.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Conducta Sexual Animal , Factores de Transcripción/metabolismo , Animales , Neuronas Colinérgicas/metabolismo , Cortejo , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Femenino , Fertilidad/genética , Regulación de la Expresión Génica , Ensayos Analíticos de Alto Rendimiento , Masculino , Proteínas del Tejido Nervioso/genética , Fenotipo , Factores de Transcripción/genéticaRESUMEN
The Drosophila melanogaster sex hierarchy controls sexual differentiation of somatic cells via the activities of the terminal genes in the hierarchy, doublesex (dsx) and fruitless (fru). We have targeted an insertion of GAL4 into the dsx gene, allowing us to visualize dsx-expressing cells in both sexes. Developmentally and as adults, we find that both XX and XY individuals are fine mosaics of cells and tissues that express dsx and/or fruitless (fru(M)), and hence have the potential to sexually differentiate, and those that don't. Evolutionary considerations suggest such a mosaic expression of sexuality is likely to be a property of other animal species having two sexes. These results have also led to a major revision of our view of how sex-specific functions are regulated by the sex hierarchy in flies. Rather than there being a single regulatory event that governs the activities of all downstream sex determination regulatory genes-turning on Sex lethal (Sxl) RNA splicing activity in females while leaving it turned off in males-there are, in addition, elaborate temporal and spatial transcriptional controls on the expression of the terminal regulatory genes, dsx and fru. Thus tissue-specific aspects of sexual development are jointly specified by post-transcriptional control by Sxl and by the transcriptional controls of dsx and fru expression.
Asunto(s)
Proteínas de Unión al ADN , Proteínas de Drosophila , Drosophila melanogaster/fisiología , Regulación del Desarrollo de la Expresión Génica , Proteínas del Tejido Nervioso , Proteínas de Unión al ARN , Diferenciación Sexual , Factores de Transcripción , Animales , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Drosophila melanogaster/metabolismo , Femenino , Masculino , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Especificidad de Órganos , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Caracteres Sexuales , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Although nervous system sexual dimorphisms are known in many species, relatively little is understood about the molecular mechanisms generating these dimorphisms. Recent findings in Drosophila provide the tools for dissecting how neurogenesis and neuronal differentiation are modulated by the Drosophila sex-determination regulatory genes to produce nervous system sexual dimorphisms. Here we report studies aimed at illuminating the basis of the sexual dimorphic axonal projection patterns of foreleg gustatory receptor neurons (GRNs): only in males do GRN axons project across the midline of the ventral nerve cord. We show that the sex determination genes fruitless (fru) and doublesex (dsx) both contribute to establishing this sexual dimorphism. Male-specific Fru (Fru(M)) acts in foreleg GRNs to promote midline crossing by their axons, whereas midline crossing is repressed in females by female-specific Dsx (Dsx(F)). In addition, midline crossing by these neurons might be promoted in males by male-specific Dsx (Dsx(M)). Finally, we (1) demonstrate that the roundabout (robo) paralogs also regulate midline crossing by these neurons, and (2) provide evidence that Fru(M) exerts its effect on midline crossing by directly or indirectly regulating Robo signaling.