Drosophila taste gene Tre is located on the distal X chromosome and controls gustatory sensitivity to a subset of sugars [1, 2]. Two adjacent, seven-transmembrane domain genes near the Tre locus are candidate genes for Tre. One (CG3171) encodes a rhodopsin family G protein receptor [3, 4], and the other (Gr5a) is a member of a chemosensory gene family encoding a putative gustatory receptor [5-7]. We carried out molecular analyses of mutations in Tre to elucidate their involvement in the gustatory phenotype. Here, we show that Tre mutations induced by P element-mediated genomic deletions disrupt Gr5a gene organization and the expression of Gr5a mRNA, while disruption of the CG3171 gene or its expression was not always associated with mutations in Tre. In flies with the spontaneous mutation Tre(01), both CG3171 and Gr5a mRNAs are transcribed. Coding sequences of these two candidate genes were compared among various strains. A total of three polymorphic sites leading to amino acid changes in CG3171 were not correlated with the gustatory phenotype. Among four nonsynonymous sites in Gr5a, a single nucleotide polymorphism leading to an Ala218Thr substitution in the predicted second intracellular loop cosegregated with Tre(01). Taken together, the mutation analyses support that Gr5a is allelic to Tre.

Canonical aversive long-term memory (LTM) formation in Drosophila requires multiple spaced trainings, whereas appetitive LTM can be formed after a single training. Appetitive LTM requires fasting prior to training, which increases motivation for food intake. However, we found that fasting facilitated LTM formation in general; aversive LTM formation also occurred after single-cycle training when mild fasting was applied before training. Both fasting-dependent LTM (fLTM) and spaced training-dependent LTM (spLTM) required protein synthesis and cyclic adenosine monophosphate response element-binding protein (CREB) activity. However, spLTM required CREB activity in two neural populations--mushroom body and DAL neurons--whereas fLTM required CREB activity only in mushroom body neurons. fLTM uses the CREB coactivator CRTC, whereas spLTM uses the coactivator CBP. Thus, flies use distinct LTM machinery depending on their hunger state.

Key points• During olfactory aversive conditioning in Drosophila, odour and shock information are delivered to the mushroom bodies (MBs) through projection neurons in the antennal lobes (ALs) and ascending fibres of the ventral nerve cord (AFV), respectively.• Using an isolated cultured brain expressing a Ca 2+ indicator in the MBs, we demonstrated that the simultaneous stimulation of the ALs and AFV establishes long-term enhancement (LTE) in AL-induced Ca 2+ responses.• The physiological properties of LTE, including associativity, input specificity and persistence, are highly reminiscent of those of olfactory memory.• Similar to olfactory aversive memory, LTE requires the activation of nicotinic acetylcholine receptors that mediate the AL-evoked Ca 2+ response, NMDA receptors that mediate the AFV-induced Ca 2+ response, and D1 dopamine receptors during the simultaneous stimulation of the ALs and AFV.• Considering the physiological and genetic analogies, we propose that LTE at the AL-MB synapse can be a relevant cellular model for olfactory memory.Abstract In Drosophila, the mushroom body (MB) is a critical brain structure for olfactory associative learning. During aversive conditioning, the MBs are thought to associate odour signals, conveyed by projection neurons (PNs) from the antennal lobe (AL), with shock signals conveyed through ascending fibres of the ventral nerve cord (AFV). Although synaptic transmission between AL and MB might play a crucial role for olfactory associative learning, its physiological properties have not been examined directly. Using a cultured Drosophila brain expressing a Ca 2+ indicator in the MBs, we investigated synaptic transmission and plasticity at the AL-MB synapse.Following stimulation with a glass micro-electrode, AL-induced Ca 2+ responses in the MBs were mediated through Drosophila nicotinic acetylcholine receptors (dnAChRs), while AFV-induced Ca 2+ responses were mediated through Drosophila NMDA receptors (dNRs). AL-MB synaptic transmission was enhanced more than 2 h after the simultaneous 'associative-stimulation' of AL and AFV, and such long-term enhancement (LTE) was specifically formed at the AL-MB synapses but not at the AFV-MB synapses. AL-MB LTE was not induced by intense stimulation of the AL alone, and the LTE decays within 60 min after subsequent repetitive AL stimulation. These phenotypes of associativity, input specificity and persistence of AL-MB LTE are highly reminiscent of olfactory memory. Furthermore, similar to olfactory aversive memory, AL-MB LTE formation required activation of the Drosophila D1 dopamine receptor, DopR, along with dnAChR and dNR

Perlecan/Trol at the neuromuscular junction suppresses presynaptic canonical Wg signaling but enhances the postsynaptic Frizzled nuclear import pathway.

Several aging phenotypes, including age-related memory impairment (AMI), are thought to be caused by cumulative oxidative damage. In Drosophila, age-related impairments in 1 hr memory can be suppressed by reducing activity of protein kinase A (PKA). However, the mechanism for this effect has been unclear. Here we show that decreasing PKA suppresses AMI by reducing activity of pyruvate carboxylase (PC), a glial metabolic enzyme whose amounts increase upon aging. Increased PC activity causes AMI through a mechanism independent of oxidative damage. Instead, increased PC activity is associated with decreases in D-serine, a glia-derived neuromodulator that regulates NMDA receptor activity. D-serine feeding suppresses both AMI and memory impairment caused by glial overexpression of dPC, indicating that an oxidative stress-independent dysregulation of glial modulation of neuronal activity contributes to AMI in Drosophila.

Simultaneous stimulation of the antennal lobes (ALs) and the ascending fibers of the ventral nerve cord (AFV), two sensory inputs to the mushroom bodies (MBs), induces long-term enhancement (LTE) of subsequent AL-evoked MB responses. LTE induction requires activation of at least three signaling pathways to the MBs, mediated by nicotinic acetylcholine receptors (nAChRs), NMDA receptors (NRs), and D1 dopamine receptors (D1Rs). Here, we demonstrate that inputs from the AL are transmitted to the MBs through nAChRs, and inputs from the AFV are transmitted by NRs. Dopamine signaling occurs downstream of both nAChR and NR activation, and requires simultaneous stimulation of both pathways. Dopamine release requires the activity of the rutabaga adenylyl cyclase in postsynaptic MB neurons, and release is restricted to MB neurons that receive coincident stimulation. Our results indicate that postsynaptic activity can gate presynaptic dopamine release to regulate plasticity.DOI: http://dx.doi.org/10.7554/eLife.21076.001

In Drosophila melanogaster, gustatory receptor genes (Grs) encode G-protein-coupled receptors (GPCRs) in gustatory receptor neurons (GRNs) and some olfactory receptor neurons. One of the Gr genes, Gr5a, encodes a sugar receptor that is expressed in a subset of GRNs and has been most extensively studied both molecularly and physiologically, but the G-protein ␣ subunit (G␣) that is coupled to this sugar receptor remains unknown. Here, we propose that Gs is the G␣ that is responsible for Gr5a-mediated sugar-taste transduction, based on the following findings: First, immunoreactivities against Gs were detected in a subset of GRNs including all Gr5a-expressing neurons. Second, trehalose-intake is reduced in flies heterozygous for null mutations in DGs␣, a homolog of mammalian Gs, and trehalose-induced electrical activities in sugar-sensitive GRNs were depressed in those flies. Furthermore, expression of wild-type DGs␣ in sugar-sensitive GRNs in heterozygotic DGs␣ mutant flies rescued those impairments. Third, expression of double-stranded RNA for DGs␣ in sugarsensitive GRNs depressed both behavioral and electrophysiological responses to trehalose. Together, these findings indicate that DGs␣ is involved in trehalose perception. We suggest that sugar-taste signals are processed through the Gs␣-mediating signal transduction pathway in sugar-sensitive GRNs in Drosophila.

Carbon monoxide (CO) is an emerging gasotransmitter and reactive carbon species with broad anti-inflammatory, cytoprotective, and neurotransmitter functions along with therapeutic potential for the treatment of cardiovascular diseases. The study of CO chemistry in biology and medicine relative to other prominent gasotransmitters such as NO and H2S remains challenging, in large part due to limitations in available tools for the direct visualization of this transient and freely diffusing small molecule in complex living systems. Here we report a ligand-directed activity-based sensing (ABS) approach to CO detection through palladium-mediated carbonylation chemistry. Specifically, the design and synthesis of a series of ABS probes with systematic alterations in the palladium-ligand environment (e.g., sp3-S, sp3-N, sp2-N) establish structureactivity relationships for palladacycles to confer selective reactivity with CO under physiological conditions. These fundamental studies led to the development of an optimized probe, termed Carbon Monoxide Probe-3 Ester Pyridine (COP3E-Py), which enables imaging of CO release in live cell and brain settings, including monitoring of endogenous CO production that triggers presynaptic dopamine release in fly brains. This work provides a unique tool for studying CO in living systems and establishes the utility of a synthetic methods approach to activity-based sensing using principles of organometallic chemistry File list (5) download file view on ChemRxiv CJC COP CO Probes Main Text.pdf (5.60 MiB) download file view on ChemRxiv CJC COP CO Probes SI.pdf (2.77 MiB) download file view on ChemRxiv COP-1-PY.cif (26.99 KiB) download file view on ChemRxiv COP-1.cif (25.25 KiB) download file view on ChemRxiv COP-1'.cif (23.98 KiB)