Biology subjects

Tanimoto, H.

Publications and source records attributed to Tanimoto, H..

At least 19 recordsLinked to original sources

bioRxiv2026

Neuropeptide T2A-GAL4 knock-ins illustrate practical considerations for interpreting GAL4 reporter patterns in Drosophila

Transgenic GAL4 lines are widely used in Drosophila to label and manipulate specific cell types, but the resulting reporter expression patterns do not always represent ongoing driver activity. We generated a collection of neuropeptide T2A-GAL4 knock-ins and characterized their expression by native-fluorescence imaging using UAS-CD8::GFP and a Brp-miRFP680 knock-in, eliminating the need for immunostaining. During characterization of these lines, we observed cases in which adult GFP patterns did not match the on-going GAL4 activity, as well as cases in which GAL4 produced adverse cellular effects. Using temperature-sensitive GAL80, we found that adult GFP expression in certain neurons driven by CCHa2-T2A-GAL4 and Dsk-T2A-GAL4 depended on GAL4 activity before eclosion and was not reproduced by adult-only induction. Several GAL4 lines also showed dominant developmental phenotypes. Heterozygous Burs-T2A-GAL4 animals, for example, displayed wing-expansion defects that were fully suppressed by GAL80. Severe wing defects were not accompanied by a reduction in the number of reporter-labeled neurons before eclosion, but the morphology of these neurons were affected. These observations illustrate how developmental driver history and GAL4-associated cellular effects can influence reporter patterns in the adult nervous system.

genetics↗

bioRxiv2026

Activity-dependent synthesis of translational machinery through dynamic remodeling of ribonucleoprotein granules

Neuronal stimulation drives gene-expression programs supporting long-lasting changes, yet how depolarization reshapes post-transcriptional regulation remains poorly understood. Here, we combined optogenetic stimulation with neuron-specific Ribo-seq and RNA-seq in the Drosophila brain to resolve activity-evoked translational dynamics. Stimulation triggered two temporally ordered programs: a rapid wave to translate synapse remodeling factors and neuropeptides, followed by a dominant delayed program that selectively upregulated translation of protein synthesis machinery, including nearly all cytosolic ribosomal proteins (RPs). Transcripts in the late program are marked by 5 terminal oligopyrimidine (TOP) motifs. TOP mRNAs accumulated in ribonucleoprotein granules at the basal state but are released upon stimulation. We identified La-related protein as a key regulator of the activity-dependent translation of TOP mRNA and memory consolidation. Comparative genomics indicated that TOP enrichment in RP mRNAs is specific to metazoans. These findings suggest that animals acquired activity-dependent TOP-mRNA control to couple neuronal stimulation with adaptation of translational capacity.

neuroscience↗

bioRxiv2026

Developmentally programmed changes in cytoplasmic mechanics revealed by active microrheology in C. elegans embryos

Cytoplasmic mechanical properties are often treated as constant background parameters, yet whether they change systematically during development remains unclear. Here, we directly measured cytoplasmic mechanics during early embryogenesis of Caenorhabditis elegans by establishing active microrheology using micrometer-sized magnetic droplets. Active microrheology revealed a progressive decrease in creep compliance from the 1-cell to the 8-cell stage, indicating a progressive stiffening of the local cytoplasmic environment during development. This decrease persisted even when cytokinesis was inhibited, demonstrating that it cannot be explained solely by geometric changes associated with cell division. Passive microrheology using 40-nm fluorescent beads showed a consistent decrease in probe mobility over development. Together, these results demonstrate that cytoplasmic mechanical properties undergo a gradual, developmentally programmed change during embryogenesis that cannot be explained by cell division-associated geometry alone.

biophysics↗

bioRxiv2025

A dual-domain chitinase mechanism enables marine bacteria tosense and localize sparse crystalline chitin in the ocean

Chitin is one of the most abundant biopolymers in the ocean, and its remineralisation underpins major pathways of marine carbon cycling. A central challenge for chitinolytic bacteria is to locate and remain associated with sparsely distributed crystalline chitin particles. Here, we show that the GH18 chitinase VpChi1 from Vibrio parahaemolyticus possesses a dual-domain architecture that enhances particle encounter and retention. Full-length VpChi1 displayed much higher catalytic efficiency than a CBD-truncated mutant at low chitin concentrations, whereas substrate inhibition occurred at higher concentrations. Single-molecule fluorescence imaging demonstrated that the additional C-terminal chitin-binding domain (CBD) enables selective binding to the hydrophobic surface of crystalline chitin and substantially prolongs enzyme residence time. Kinetic simulations using experimentally determined dissociation rates showed that this extended residence arises from CBD-assisted rebinding of the catalytic domain. High-speed atomic force microscopy confirmed that the CBD does not alter stepping velocity or travel distance along individual crystals, indicating that substrate inhibition likely results from CBD engagement with neighbouring particles rather than impaired motility. Screening of seawater and marine sediments across multiple depths identified Vibrio and Pseudoalteromonas species as dominant chitin degraders, many encoding GH18 chitinases with dual CBDs, whereas terrestrial bacteria generally lacked this architecture. We propose that this two-domain configuration confers an ecological advantage by increasing enzyme retention on particulate chitin and enabling sustained production of chitobiose, a potent chemotactic signal for marine bacteria. These findings reveal a mechanistic basis for how bacteria sense and exploit particulate chitin and highlight an adaptive strategy for resource acquisition in the ocean.

molecular biology↗

bioRxiv2025

Neuropeptide signalling and perineurial barrier generate a persistent stress-induced internal state in Drosophila

Although fear conditioning has elucidated cue-evoked acute fear responses, the mechanisms by which stress experiences induce generalized internal states linked to anxiety are poorly understood. Here, we report that robust stress induces a persistent behavioral change characterized by avoidance of a confined space, claustrophobia-like behavior in Drosophila. Unlike aversive memory formation, the development of claustrophobia-like behavior does not require dopamine receptors. Our neuronal screening determined that neuropeptide signalling via Allatostatin-A inactivates the downstream neurons via its receptor AstA-R1, causally inducing claustrophobia-like behavior. Moreover, gene expression profiling of individual fly heads revealed that immune response activation in perineurial barrier is involved in claustrophobia-like behavior. Our data demonstrate that stress-induced persistent behavioral change would not be related to a canonical mechanism of aversive memory formation, rather involves neuropeptidergic signalling and perineurial barrier, providing the mechanism determining internal states which persistently change behavioral modes.

neuroscience↗

bioRxiv2025

Chameau (HBO1) regulates starvation in a temperature-dependent manner in Drosophila melanogaster

The body temperature of Drosophila melanogaster depends on the extrinsic temperature. Numerous studies in fruit flies have shown that environmental temperature has an effect on metabolism, lifespan and starvation resilience. We have previously shown that Chameau (Chm), a MYST-domain acetyltransferase, promotes aging but also increases starvation resilience. As starvation resilience is highly temperature dependent, we explored the effect of temperature on starvation resilience in fruit flies with reduced chm expression. Strikingly, we found that an increase of 2{degrees}C was sufficient to restore starvation resilience in chm mutants. The increase in temperature rescued the dampened expression of genes involved in insulin, hormone and starvation response as well as a reduced rate of weight loss and misregulation of trehalose, which we observed in chm mutants at 23{degrees}C. Our data show that whereas Chm has an important role in regulating starvation at 23{degrees}C and below, it becomes obsolete at higher temperatures. Our finding that a gene plays an important role only under specific environmental conditions has important implications in light of the recent global change of climate conditions.

molecular biology↗

bioRxiv2024

Synapse profiling of identified neurons in the Drosophila brain

Characterization of intracellular synapse heterogeneity aides to understand the intricate computational logic of neuronal circuits. Despite recent advances in connectomics, the spatial patterns of synapses and their inter-individual variability remain largely unknown. Using directed split-GFP reconstitution, we achieved visualization of endogenous Bruchpilot (Brp), a presynaptic active zone (AZ) scaffold protein, in a cell-type-specific manner. By developing a high-throughput quantification pipeline, we profiled AZ structures in identified neurons of the mushroom body circuit, where intracellular synaptic patterns are crucial due to compartmentalized connectivity. Quantitative characterization of the pattern of Brp clusters across multiple individuals revealed cell-type-dependent synapse heterogeneity and stereotypy. Furthermore, we discovered previously unidentified sub-compartmental synapse configuration and its transient structural plasticity triggered by associative learning. These profiles thus uncovered multi-layered spatial configurations of AZs, from stereotyped overall AZ distribution patterns, to local arrangements of neighboring synapses.

neuroscience↗

bioRxiv2024

Octopamine signals coordinate the spatial pattern of presynaptic machineries in the Drosophila mushroom bodies

Neurons need to adjust synaptic output according to the targets. However, the target-specific synaptic structures within individual neurons in the central nervous system remains unresolved. Applying the CRISPR/Cas9-mediated split-GFP tagging, we visualized the endogenous active zone scaffold protein, Bruchpilot (Brp), in specific cells. This technology enabled the spatial characterization of presynaptic machineries only within the Kenyon cells (KCs) of the Drosophila mushroom bodies. We found the patterned accumulation of Brp among the compartments of axon terminals, where a KC synapses onto different postsynaptic neurons. Mechanistically, the localized octopaminergic modulation along {gamma} KC terminals regulate this compartmental Brp heterogeneity via Oct{beta}2R and cAMP signaling. We further found that acute food deprivation reorganizes this spatial pattern in an octopamine-dependent manner. Such coordinated regulation of local synaptic machineries thus explains how the mushroom bodies integrate changing physiological states. This subcellular information processing represents an elegant solution to expand computational capacity of the circuit.

neuroscience↗

bioRxiv2024

A Bidirectional Brain-Fat Body Axis for Pathogen Avoidance

Ingesting pathogens through spoiled food can cause serious harm, including infections, tissue damage, and even death. To prevent these outcomes, many animals have evolved behaviors to avoid consuming harmful pathogens. While pathogen avoidance behavior is conserved across species, the mechanisms linking immune responses of the body with neuron-controlled behavior remain unclear. Building on our previous findings, we here present a new bidirectional body-brain communication between the fat body and the nervous system that drives immune receptor-induced avoidance behavior. We show that immune receptor signaling and a specific antimicrobial peptide (AMP) are essential in both octopaminergic neuromodulatory neurons and the fat body for rapidly reducing pathogen intake after initial ingestion. Mechanistically, the octopaminergic neurons innervate the flys fat body where they trigger a calcium response through a specific octopamine receptor. This octopaminergic signal prompts the fat body to release dopamine. In turn, Dop1R1 signaling in output neurons of the mushroom body, the insect higher brain center, drives pathogen avoidance. Together, our data suggest that ingested pathogens are detected by immune receptors in neurons, which, through synaptic connections, trigger the release of dopamine and AMPs from fat cells. While AMPs combat the pathogens, dopamine reduces further ingestion by inducing behavioral changes. This mechanism demonstrates efficient communication between the body and brain, coordinating survival behaviors through systemic dopamine signaling from the fat body to the brain.

neuroscience↗

bioRxiv2024

Blue light toxicity drives the gut microbiota-mediated lipid accumulation in Drosophila

Human agriculture has always raced against insect adaptation, requiring updated pest control methods and knowledge of evolutionary processes. Excessive exposure to blue light (BL) kills a wide range of insect species and has attracted attention as an alternative to chemical pesticides. Here, to understand how insects adapt to BL toxicity, we investigated evolutionary responses to BL toxicity in Drosophila melanogaster over 70 generations using laboratory selection experiments. The selected line exhibited an obese phenotype accompanied by midgut elongation, with BL tolerance dependent on gut microbiota- mediated lipid accumulation. Whole-genome and transcriptome analyses consistently highlighted interactions between the microbiota and host lipid metabolism-related genes. Remarkably, manipulating genes associated with lipid accumulation conferred BL tolerance even in the absence of selection. We suggest that the acquisition of BL tolerance occurs through adaptive obesity. Our study introduces a mechanism of evolutionary adaptation of insects against BL-based selective pressure by maximising the benefits from the gut microbiota via midgut elongation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/608892v5_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@111c9d5org.highwire.dtl.DTLVardef@d9bf7forg.highwire.dtl.DTLVardef@1ab46fborg.highwire.dtl.DTLVardef@1c111cd_HPS_FORMAT_FIGEXP M_FIG C_FIG Brief summaryLaboratory selection for tolerance to blue light toxicity in Drosophila revealed that gut microbiota-mediated obesity, marked by midgut elongation and increased beneficial bacteria, is a key evolutionary adaptation.

evolutionary biology↗

bioRxiv2024

Cell-type-specific fluorescent tagging of endogenous target proteins reveals synaptic enrichment and dynamic regulations of dopamine receptors

Dopamine can play opposing physiological roles depending on the receptor subtype. In the fruit fly Drosophila melanogaster, Dop1R1 and Dop2R encode the D1- and D2-like receptors, respectively, and are reported to oppositely regulate intracellular cAMP levels. Here, we profiled the expression and subcellular localization of endogenous Dop1R1 and Dop2R in specific cell types in the mushroom body circuit. For cell-type-specific visualization of endogenous proteins, we employed reconstitution of split-GFP tagged to the receptor proteins. We detected dopamine receptors at both presynaptic and postsynaptic sites in multiple cell types. Quantitative analysis revealed enrichment of both receptors at the presynaptic sites, with Dop2R showing a greater degree of localization than Dop1R1. The presynaptic localization of Dop1R1 and Dop2R in dopamine neurons suggests dual feedback regulation as autoreceptors. Furthermore, we discovered a starvation-dependent, bidirectional modulation of the presynaptic receptor expression in the PAM and PPL1 clusters, two distinct subsets of dopamine neurons, suggesting regulation of appetitive behaviors. Our results highlight the significance of the co-expression of the two opposing dopamine receptors in the spatial and conditional regulation of dopamine responses in neurons.

neuroscience↗

bioRxiv2023

Translational regulation enhances distinction of cell types in the nervous system

Multicellular organisms are composed of specialized cell types with distinct proteomes. While recent advances in single-cell transcriptome analyses have revealed differential expression of mRNAs, cellular diversity in translational profiles remains underinvestigated. By performing RNA-seq and Ribo-seq in genetically-defined cells in the Drosophila brain, we here revealed substantial posttranscriptional regulations that augment the cell-type distinctions at the level of protein expression. Specifically, we found that translational efficiency of proteins fundamental to neuronal functions, such as ion channels and neurotransmitter receptors, was maintained low in glia, leading to their preferential translation in neurons. Notably, distribution of ribosome footprints on these mRNAs exhibited a remarkable bias towards the 5' leaders in glia. Using transgenic reporter strains, we provide evidence that the small upstream open reading frames (uORFs) in the 5 leader confer selective translational suppression in glia. Overall, these findings underscore the profound impact of translational regulation in shaping the proteomics for cell-type distinction and provide new insights into the molecular mechanisms driving cell-type diversity.

neuroscience↗

bioRxiv2022

Female reproductive dormancy in Drosophila melanogaster is regulated by DH31-producing neurons projecting into the corpus allatum

Female reproductive dormancy in insects is a process that drastically suppresses oogenesis to conserve energy under adverse environments. In many insects, including the fruit fly, Drosophila melanogaster, reproductive dormancy is induced under low-temperature and short-day conditions by the downregulation of juvenile hormone (JH) biosynthesis by the corpus allatum (CA). Previous studies have suggested that brain neurons that project directly to the CA are important for the regulation of reproductive dormancy. However, the role of CA-projecting neurons in JH-mediated reproductive dormancy has not yet been confirmed by molecular genetic studies. In this study, we report that, in adult D. melanogaster, the neuropeptide diuretic hormone 31 (DH31) is produced by brain neurons that project into the CA. DH31-producing-CA-projecting neurons are connected downstream with a subset of circadian clock neurons, such as s-LNvs, which are known to be involved in reproductive dormancy regulation. The CA expresses the gene encoding the DH31 receptor, which is required for DH31-triggered elevation of intracellular cAMP in the CA. Knocking down Dh31 in these CA-projecting neurons or DH31 receptor in the CA leads to a failure in the decrease of the JH titer, normally observed under dormancy-inducing conditions, leading to abnormal yolk accumulation in the ovaries. Our findings provide the first molecular genetic evidence demonstrating that CA-projecting peptidergic neurons play an essential role in regulating reproductive dormancy by suppressing JH biosynthesis. Significance StatementDormancy is an adaptive physiological response to environmental changes that are unsuitable for survival. Adult females of many insect species undergo reproductive dormancy in which oogenesis is drastically arrested; it is induced by a decrease in juvenile hormone (JH) titers. However, we are yet to fully understand the molecular mechanisms underlying the control of JH biosynthesis under dormancy-inducing conditions. In this study using the fruit fly, we demonstrated that brain neurons projecting directly to the JH-producing organ, corpus allatum, play an essential role in regulating reproductive dormancy via the neuropeptide DH31. As the morphologically-similar neurons have previously been suggested to be involved in reproductive dormancy regulation, this study provides a fundamental molecular and neuronal basis for reproductive dormancy in insects.

physiology↗

bioRxiv2022

A descending inhibitory mechanism of nociception mediated by an evolutionarily conserved neuropeptide system in Drosophila

Nociception is a neural process that animals have developed to avoid potentially tissue-damaging stimuli. While nociception is triggered in the peripheral nervous system, its modulation by the central nervous system is a critical process in mammals, whose dysfunction has been extensively implicated in chronic pain pathogenesis. The peripheral mechanisms of nociception are largely conserved across the animal kingdom. However, it is unclear whether the brain-mediated modulation is also conserved in non-mammalian species. Here, we show that Drosophila has a descending inhibitory mechanism of nociception from the brain, mediated by the neuropeptide Drosulfakinin (DSK), a homolog of cholecystokinin (CCK) that plays an important role in the descending control of nociception in mammals. We found that mutants lacking dsk or its receptors are hypersensitive to noxious heat. Through a combination of genetic, behavioral, histological, and Ca2+ imaging analyses, we subsequently revealed neurons involved in DSK-mediated nociceptive regulation at a single-cell resolution and identified a DSKergic descending neuronal pathway that inhibits nociception. This study provides the first evidence for a descending modulatory mechanism of nociception from the brain in a non-mammalian species that is mediated by the evolutionarily conserved CCK system, raising the possibility that the descending inhibition is an ancient mechanism to regulate nociception.

neuroscience↗

bioRxiv2021

The sugar-responsive enteroendocrine neuropeptide F regulates lipid metabolism through glucagon-like and insulin-like hormones in Drosophila melanogaster

The enteroendocrine cell (EEC)-derived incretins play a pivotal role in regulating the secretion of glucagon and insulins in mammals. Although glucagon-like and insulin-like hormones have been found across animal phyla, incretin-like EEC-derived hormones have not yet been characterised in invertebrates. Here, we show that the midgut-derived hormone, Neuropeptide F (NPF), acts as the sugar-responsive, incretin-like hormone in the fruit fly, Drosophila melanogaster. Secreted NPF is received by NPF receptor in the corpora cardiaca and in insulin-producing cells. NPF-NPFR signalling resulted in the suppression of the glucagon-like hormone production and the enhancement of the insulin-like peptide secretion, eventually promoting lipid anabolism. Similar to the loss of incretin function in mammals, loss of midgut NPF led to significant metabolic dysfunction, accompanied by lipodystrophy, hyperphagia, and hypoglycaemia. These results suggest that enteroendocrine hormones regulate sugar-dependent metabolism through glucagon-like and insulin-like hormones not only in mammals but also in insects.

physiology↗

bioRxiv2021

A population of neurons that produce hugin and express the diuretic hormone 44 receptor gene projects to the corpora allata in Drosophila melanogaster

The corpora allata (CA) are essential endocrine organs that biosynthesize and secrete the sesquiterpenoid hormone, namely juvenile hormone (JH), to regulate a wide variety of developmental and physiological events in insects. Previous studies had demonstrated that the CA are directly innervated with neurons in many insect species, implying the innervations to be important for regulating JH biosynthesis in response to internal physiology and external environments. While this is also true for the model organism, Drosophila melanogaster, which neurotransmitters are produced in the CA-projecting neurons are yet to be clarified. In this study on D. melanogaster, we aimed to demonstrate that a subset of neurons producing the neuropeptide hugin, the invertebrate counterpart of the vertebrate neuromedin U, directly projects to the adult CA. A synaptic vesicle marker in the hugin neurons was observed at their axon termini located on the CA, which were immunolabeled with a newly-generated antibody to the JH biosynthesis enzyme JH acid O-methyltransferase (JHAMT). We also found the CA-projecting hugin neurons to likely express a gene encoding the specific receptor for diuretic hormone 44 (Dh44). Moreover, our data suggested that the CA-projecting hugin neurons have synaptic connections with the upstream neurons producing Dh44. To the best of our knowledge, this is the first study to identify a specific neurotransmitter of the CA-projecting neurons in D. melanogaster, and to anatomically characterize a neuronal pathway of the CA-projecting neurons and their upstream neurons.

zoology↗

bioRxiv2020

Rhythmic temperature control in a homeothermic plant: A field study of thermogenic Japanese skunk cabbage, Symplocarpus renifolius

The spadices of skunk cabbage (Symplocarpus renifolius) can generate heat and maintain an internal temperature of about 23{degrees}C, even when the ambient air temperature drops below freezing. In this study, we continuously measured the spadix temperatures of skunk cabbage together with ambient air temperatures during March 2019 in their natural habitat in northern Honshu on Japans main island. Using Fourier transform we showed that the temperature of the thermogenic spadix oscillates over a period of approximately 60 min. Our data suggest that Japanese skunk cabbage possesses a novel timekeeping mechanism that may be associated with a homeothermic control of this plant.

plant biology↗

bioRxiv2020

Neuronal octopamine signaling regulates mating-induced germline stem cell proliferation in female Drosophila melanogaster

Stem cells fuel the development and maintenance of tissues. Many studies have addressed how local signals from neighboring niche cells regulate stem cell identity and their proliferative potential. However, the regulation of stem cells by tissue-extrinsic signals in response to external cues remains poorly understood. Here we report that efferent octopaminergic neurons projecting to the ovary are essential for germline stem cell (GSC) proliferation in response to mating in female Drosophila. The neuronal activity of the octopaminergic neurons is required for mating-induced GSC proliferation as they relay the mating signal from Sex peptide receptor-positive cholinergic neurons. Octopamine and its receptor Oamb are also required for mating-induced GSC proliferation via intracellular Ca2+ signaling. Moreover, we identified Matrix metalloproteinase-2 as a downstream component of the octopamine-Ca2+ signaling to induce GSC proliferation. Our study provides a mechanism describing how neuronal system couples stem cell behavior to external cues through stem cell niche signaling.

developmental biology↗