neuronal Glucose-6-Phosphatase is a modulator of neuropeptide release that regulates muscle glycogen stores via FMRFamide signaling.

Neuropeptides (NPs) and their cognate receptors are critical effectors of diverse physiological processes and behaviors. We recently reported of a noncanonical function of the () gene in a subset of neurosecretory cells in the central nervous system that governs systemic glucose homeostasis in food-deprived flies. Here, we show that expressing neurons define six groups of NP-secreting cells, four in the brain and two in the thoracic ganglion.

Neuronal Glucose 6 Phosphatase is a Modulator of Neuropeptide Release that Regulates Muscle Glycogen Stores via FMRFamide Signaling.

Unlabelled: Neuropeptides (NPs) and their cognate receptors are critical effectors of diverse physiological processes and behaviors. We recently reported of a non-canonical function of the ( ) gene in a subset of neurosecretory cells in the CNS that governs systemic glucose homeostasis in food deprived flies. Here, we show that expressing neurons define 6 groups of neuropeptide secreting cells, 4 in the brain and 2 in the thoracic ganglion.

Opposing chemosensory functions of closely related gustatory receptors.

In the fruit fly , gustatory sensory neurons express taste receptors that are tuned to distinct groups of chemicals, thereby activating neural ensembles that elicit either feeding or avoidance behavior. Members of a family of ligand -gated receptor channels, the Gustatory receptors (Grs), play a central role in these behaviors. In general, closely related, evolutionarily conserved Gr proteins are co-expressed in the same type of taste neurons, tuned to chemically related compounds, and therefore triggering the same behavioral response.

Opposing chemosensory functions of closely related gustatory receptors.

Most animals have functionally distinct populations of taste cells, expressing receptors that are tuned to compounds of different valence. This organizational feature allows for discrimination between chemicals associated with specific taste modalities and facilitates differentiating between unadulterated foods and foods contaminated with toxic substances. In the fruit fly , primary sensory neurons express taste receptors that are tuned to distinct groups of chemicals, thereby activating neural ensembles that elicit either feeding or avoidance behavior.

RNA Taste Is Conserved in Dipteran Insects.

Background: Ribonucleosides and RNA are an underappreciated nutrient group essential during Drosophila larval development and growth. Detection of these nutrients requires at least one of the 6 closely related taste receptors encoded by the Gr28 genes, one of the most conserved insect taste receptor subfamilies.

Objectives: We investigated whether blow fly larvae and mosquito larvae, which shared the last ancestor with Drosophila about 65 and 260 million years ago, respectively, can taste RNA and ribose.

Sensory biology: Thirsty glia motivate water consumption.

Regulation of water intake is governed by numerous motivated behaviors that are critical for the survival of nearly all animals. A recent study identifies a critical role for glia-neuron communication in the detection of water shortage and the initiation of thirst-associated behaviors.

Neuronal Gluconeogenesis Regulates Systemic Glucose Homeostasis in Drosophila melanogaster.

Gluconeogenesis is a well-established metabolic process whereby glucose is generated from small carbon molecules in the liver and kidney to maintain blood glucose levels. Expression of gluconeogenic genes has been reported in other organs of mammals and insects, where their function is not yet known. In the fruit fly, one of the gluconeogenic genes, glucose-6-phosphatase (G6P) is exclusively expressed in the CNS.

The taste of ribonucleosides: Novel macronutrients essential for larval growth are sensed by Drosophila gustatory receptor proteins.

Animals employ various types of taste receptors to identify and discriminate between different nutritious food chemicals. These macronutrients are thought to fall into 3 major groups: carbohydrates/sugars, proteins/amino acids, and fats. Here, we report that Drosophila larvae exhibit a novel appetitive feeding behavior towards ribose, ribonucleosides, and RNA.

Molecular basis of fatty acid taste in .

Behavioral studies have established that appetitive taste responses towards fatty acids are mediated by sweet sensing Gustatory Receptor Neurons (GRNs). Here we show that sweet GRN activation requires the function of the genes , and . The former two genes are expressed in several neurons per sensillum, while expression is restricted to sweet GRNs.

Ionotropic Receptors Mediate Drosophila Oviposition Preference through Sour Gustatory Receptor Neurons.

Carboxylic acids are present in many foods, being especially abundant in fruits. Yet, relatively little is known about how acids are detected by gustatory systems and whether they have a potential role in nutrition or provide other health benefits. Here we identify sour gustatory receptor neurons (GRNs) in tarsal taste sensilla of Drosophila melanogaster.

SIK3-HDAC4 signaling regulates circadian male sex drive rhythm via modulating the DN1 clock neurons.

The physiology and behavior of many organisms are subject to daily cycles. In the daily locomotion patterns of single flies are characterized by bursts of activity at dawn and dusk. Two distinct clusters of clock neurons-morning oscillators (M cells) and evening oscillators (E cells)-are largely responsible for these activity bursts.

Gluconeogenesis: An ancient biochemical pathway with a new twist.

Synthesis of sugars from simple carbon sources is critical for survival of animals under limited nutrient availability. Thus, sugar-synthesizing enzymes should be present across the entire metazoan spectrum. Here, we explore the evolution of glucose and trehalose synthesis using a phylogenetic analysis of enzymes specific for the two pathways.

A genetic tool kit for cellular and behavioral analyses of insect sugar receptors.

Arthropods employ a large family of up to 100 putative taste or gustatory receptors (Grs) for the recognition of a wide range of non-volatile chemicals. In Drosophila melanogaster, a small subfamily of 8 Gr genes is thought to mediate the detection of sugars, the fly's major nutritional source. However, the specific roles for most sugar Gr genes are not known.

An expression system for Gustatory receptors - and why it failed.

A recent paper by the Dahankuar laboratory suggested that single Drosophila sugar receptors proteins accurately mediate sugar detection when ectopically expressed in olfactory neurons of the antenna. These findings contra-dict numerous previously published electrophysiological and behavioral investigations, which all point towards heteromultimeric sugar taste receptors. Here, I provide some explanation why this "pseudo-heterologous" expression system may have led to this misleading conclusion.

Drosophila sugar receptors in sweet taste perception, olfaction, and internal nutrient sensing.

Identification of nutritious compounds is dependent on expression of specific taste receptors in appropriate taste-cell types [1]. In contrast to mammals, which rely on a single, broadly tuned heterodimeric sugar receptor [2], the Drosophila genome harbors a small subfamily of eight, closely related gustatory receptor (Gr) genes, Gr5a, Gr61a, and Gr64a-Gr64f, of which three have been proposed to mediate sweet taste [3-6]. However, expression and function of several of these putative sugar Gr genes are not known.

Enhancing perception of contaminated food through acid-mediated modulation of taste neuron responses.

Background: Natural foods contain not only nutrients, but also nonnutritious and potentially harmful chemicals. Thus, animals need to evaluate food content in order to make adequate feeding decisions.

Results: Here, we investigate the effects of acids on the taste neuron responses and on taste behavior of desirable, nutritious sugars and sugar/bitter compound mixtures in Drosophila melanogaster.

Diverse roles for the Drosophila fructose sensor Gr43a.

The detection of nutrients, both in food and within the body, is crucial for the regulation of feeding behavior, growth, and metabolism. While the molecular basis for sensing food chemicals by the taste system has been firmly linked to specific taste receptors, relatively little is known about the molecular nature of the sensors that monitor nutrients internally. Recent reports of taste receptors expressed in other organ systems, foremost in the gastrointestinal tract of mammals and insects, has led to the proposition that some taste receptors may also be used as sensors of internal nutrients.

The molecular basis of sugar sensing in Drosophila larvae.

Evaluation of food chemicals is essential to make appropriate feeding decisions. The molecular genetic analysis of Gustatory receptor (Gr) genes and the characterization of the neural circuits that they engage has led to a broad understanding of taste perception in adult Drosophila [1, 2]. For example, eight relatively highly conserved members of the Gr gene family (Gr5a, Gr61a, and Gr64a-f), referred to as sugar Gr genes, are thought to be involved in sugar taste in adult flies [3-8], while the majority of the remaining Gr genes are likely to encode bitter taste receptors [9-11], albeit some function as pheromone [12-14] and carbon dioxide [15, 16] receptors.

Identification of a Drosophila glucose receptor using Ca2+ imaging of single chemosensory neurons.

Evaluation of food compounds by chemosensory cells is essential for animals to make appropriate feeding decisions. In the fruit fly Drosophila melanogaster, structurally diverse chemicals are detected by multimeric receptors composed of members of a large family of Gustatory receptor (Gr) proteins. Putative sugar and bitter receptors are expressed in distinct subsets of Gustatory Receptor Neurons (GRN) of taste sensilla, thereby assigning distinct taste qualities to sugars and bitter tasting compounds, respectively.

A fructose receptor functions as a nutrient sensor in the Drosophila brain.

Internal nutrient sensors play important roles in feeding behavior, yet their molecular structure and mechanism of action are poorly understood. Using Ca(2+) imaging and behavioral assays, we show that the gustatory receptor 43a (Gr43a) functions as a narrowly tuned fructose receptor in taste neurons. Remarkably, Gr43a also functions as a fructose receptor in the brain.

Hierarchical chemosensory regulation of male-male social interactions in Drosophila.

Pheromones regulate male social behaviors in Drosophila, but the identities and behavioral role(s) of these chemosensory signals, and how they interact, are incompletely understood. We found that (z)-7-tricosene, a male-enriched cuticular hydrocarbon that was previously shown to inhibit male-male courtship, was essential for normal levels of aggression. The mechanisms by which (z)-7-tricosene induced aggression and suppressed courtship were independent, but both required the gustatory receptor Gr32a.

Ventral lateral and DN1 clock neurons mediate distinct properties of male sex drive rhythm in Drosophila.

Male sex drive rhythm (MSDR) in Drosophila is a circadian behavior only observed in the social context of male-female pairs. In the presence of a female, males exhibit long periods of courtship activity with a pronounced rest phase at dusk, although isolated males exhibit an activity peak at dusk. The molecular mechanisms regulating the switch between these activity patterns are unknown.

A male-specific fatty acid omega-hydroxylase, SXE1, is necessary for efficient male mating in Drosophila melanogaster.

In Drosophila, sexual differentiation, physiology, and behavior are thought to be mediated by numerous male- and female-specific effector genes whose expression is controlled by sex-specifically expressed transcriptional regulators. One such downstream effector gene, sex-specific enzyme 1 (sxe1, cyp4d21), has been identified in a screen for genes with sex-biased expression in the head. Sxe1 was also identified in another screen as a circadian regulated gene.

Suppression of male courtship by a Drosophila pheromone receptor.

In male Drosophila, chemosensory cues control many aspects of social behavior. We found that males with a mutated Gustatory receptor 32a gene (Gr32a) show high courtship toward males and mated females, indicating that GR32a functions as a pheromone receptor for a male inhibitory pheromone. Notably, we discovered that tarsal Gr32a-expressing neurons were essential for courtship suppression and projected to the ventrolateral protocerebrum, implying direct communication of chemosensory neurons with a higher-order brain structure.