Biology subjects

Buchon, N.

Publications and source records attributed to Buchon, N..

14 recordsLinked to original sources

bioRxiv2026

Engineering Upd-like to broadly restrict arbovirus infection and vector competence in mosquitoes

The global expansion of mosquito-borne viruses poses a growing threat to public health, yet the endogenous signals that activate antiviral immunity in mosquito vectors remain incompletely understood. Here, we identify Aedes aegypti Upd as an activator of JAK/STAT signaling that restricts arbovirus infection. Loss of Upd increased infection and dissemination of the flaviviruses ZIKV and DENV, as well as the alphavirus SINV, whereas blood meal inducible midgut overexpression reduced ZIKV and SINV infection. Mechanistically, Upd associated with the extracellular region of the Domeless (Dome) receptor, and Upd deficiency markedly reduced STAT phosphorylation and nuclear accumulation in the midgut. Upd expression was transiently induced in the midgut by an uninfected blood meal but remained elevated following ZIKV challenge, linking physiological responses to blood feeding with antiviral defense. In mammal mosquito transmission models, Upd overexpression reduced viral acquisition from infected hosts, whereas Upd deficiency enhanced viral dissemination and increased transmission following systemic infection. Together, these findings identify Upd as an endogenous regulator of mosquito JAK/STAT signaling and provide proof of principle that temporally targeted Upd expression can reduce arbovirus susceptibility and vector competence.

microbiology↗

bioRxiv2026

Shielded by the dead: how killed bacteria shape the dynamics and evolution of innate immunity

The outcome of an infection is determined by the dynamic interplay between microbial growth and host immunity. During a bacterial infection, bacteria killed by innate immune effectors can accumulate as corpses in the extracelluar space, where they can continue to bind (and thus sequester) immune effectors. The impacts on infection outcomes of continued biochemical activity ("sponginess") by the dead have been generally overlooked in theoretical and empirical studies of within-host disease dynamics. We develop a mechanism-based mathematical model of within-host dynamics that incorporates host microbial sensing, the production of immune effectors, the interaction of those effectors with microbes, and shutdown of the immune response after an infection has been controlled. Corpse sponginess impedes the hosts ability to control infection, but at the same time, the rapid mopping up of effectors by bacterial corpses also protects host tissue against autoimmune self-harm from immune effectors still circulating after the infection has been resolved. This dual impact of bacterial sponginess alters the trade-off between damage done by infecting bacteria versus autoimmune damage, consequently shifting the evolutionarily optimal immune activation and shutdown kinetics. Thus, the sponginess of bacterial corpses likely shapes both short-term infection dynamics and the long-term evolution of immune systems.

immunology↗

bioRxiv2025

UGT35B1 is the principal enzyme mediating nicotine glycosylation in Drosophila melanogaster

Nicotine is a plant-derived pyridine alkaloid with potent neurotoxic properties. A major pathway for detoxification of nicotine in mammals is via glucuronidation to produce nicotine N-glucuronide, but this process in insects remains poorly understood. Using mass spectrometry, we demonstrate that Drosophila melanogaster detoxifies nicotine through glycosylation, producing nicotine N-glycoside. Given that many new agrochemicals contain pyridine rings, we also investigated the metabolism of flonicamid and imidacloprid. We detected glycosylation of flonicamid, but not imidacloprid. A targeted RNAi screen across 21 UDP-glycosyltransferases (Ugts) identified Ugt35B1 as important for survival of nicotine exposure. CRISPR-based knockout of Ugt35B1 increases sensitivity to nicotine and flonicamid, but not to imidacloprid, nor to a structurally distinct neonicotinoid (thiamethoxam). Mass spectrometry of knockout and control flies confirms that Ugt35B1 glycosylates nicotine, its metabolite cotinine, and flonicamid. Together these findings establish Ugt35B1 as the principal UGT mediating nicotine detoxification in D. melanogaster, revealing a previously uncharacterized insect glycosylation pathway with potential implications for herbivory, insecticide detoxification and toxicology. Highlights- Drosophila detoxifies nicotine by glycosylation into nicotine N-glycoside. - A targeted RNAi screen identifies Ugt35B1 as critical for nicotine survival. - Ugt35B1 knockout sensitizes flies to nicotine and flonicamid, but not to imidacloprid or thiamethoxam. - First demonstration of an insect UGT mediating in vivo glycosylation of nicotine and cotinine.

pharmacology and toxicology↗

bioRxiv2025

Upd-like/JAK/STAT signaling promotes regeneration and tolerance to bacterial infection in the Aedes midgut

Aedes aegypti, a major vector of arboviruses, relies on its midgut as a key interface with microbial communities that influence vector competence. While ingestion of pathogenic bacteria is known to trigger both immune and regenerative responses in the mosquito gut, the signaling pathways that govern epithelial renewal remain poorly defined. Here, we address this gap by performing transcriptomic profiling of the Aedes aegypti midgut following oral infection with entomopathogenic bacteria. We uncover a broad transcriptional activation of immune pathways, including IMD, Toll, and notably, the JAK-STAT signaling cascade. Functional knockdown experiments reveal that JAK-STAT signaling is essential for infection-induced epithelial cell proliferation and survival, but dispensable for bacterial clearance, supporting a specialized role in tissue repair and infection tolerance. We further identify a previously uncharacterized cytokine-like gene, Upd-like, structurally related to Drosophila Unpaired proteins and mammalian cytokines, which is strongly induced upon bacterial challenge and activates JAK-STAT signaling in mosquito cells. Silencing Upd-like markedly impairs epithelial regeneration after infection, establishing it as a key regulator of gut homeostasis. Together, these findings demonstrate a conserved function for JAK-STAT signaling in midgut epithelial renewal and identify Upd-like as a novel cytokine mediating regenerative responses during bacterial infection.

immunology↗

bioRxiv2025

Microbes and diet reshape the intestine via distinct cellular dynamics

BackgroundThe intestine adapts to environmental stimuli by dynamically altering its size. Infections causes shrinkage and subsequent regrowth to original intestinal dimensions, suggesting homeostasis, whereas diet can induce adaptive changes. Whether diet and infection differ in the kinetics, magnitude, or cellular mechanisms that drive intestinal resizing, and whether intestines use a fixed size "memory" versus an adaption to nutrient availability, still remains unclear. ObjectiveTo determine whether intestinal regrowth after infection reflects a fixed "memory" of a target size (homeostasis) or an adaptation to the nutritional state during regrowth, and to identify the cellular modalities that drive infection- and diet-induced resizing. DesignUsing Drosophila melanogaster as a model, we quantified intestinal size, cell size, cell number, and epithelial turnover in response to dietary shifts and oral bacterial infections, both individually and in combination. ResultsInfection-induced atrophy occurred only when the intestine was initially large, and regrowth required nutrient availability. Distinct cellular mechanisms underpinned changes in intestinal size: diet-induced growth in unchallenged intestines was mediated by enterocyte hypertrophy, whereas post-infection regrowth required intestinal stem cell (ISC) proliferation. Consistently, ISC ablation impaired regrowth only after infection. Bacteria functioned both as pathogens and nutrients, triggering intestinal shrinkage when damaging a large organ, but promoting growth when consumed by nutrient-deprived flies. ConclusionIntestinal regrowth after infection reflects a context-dependent, diet-driven adaptation, not a fixed intestinal size memory. Diet and infection engage distinct, stimulus-specific cellular programs to reshape the midgut, revealing a modular logic of organ plasticity with implications for tissue repair and metabolic regulation. Summary boxO_ST_ABSWhat is already known on this topicC_ST_ABS- Intestinal size is regulated by epithelial turnover and responds dynamically to dietary and microbial stimuli. What this study adds- Post-infection intestinal regrowth is governed by dietary input rather than an intrinsic memory of pre-infection intestinal size. - Intestinal resizing is driven by distinct cellular programs: diet-induced intestinal growth occurs independently of stem cells, while post-infection intestinal regrowth requires stem cell proliferation. - Diet, rather than microbes, is the primary driver of intestinal size, while pathogens influence the mode of size change by increasing cellular turnover. - Pathogenic microbes act as both sources of damage and nutrients, influencing organ resizing. How this study might affect research, practice, or policy- Reframes intestinal regeneration as a flexible, context-dependent adaptation rather than a fixed homeostatic process. - Identifies nutritional status as a critical determinant of recovery following intestinal injury. - Offers a conceptual framework for understanding epithelial plasticity in health and disease, emphasizing how the balance of cell size and stem cell activity coordinates adult intestinal size.

developmental biology↗

bioRxiv2024

Variations in polarized trafficking of viral envelope proteins from insect-specific and insect-vectored viruses in insect midgut and salivary gland cells

Systemic viral infection of insects typically begins with primary infection of midgut epithelial cells (enterocytes) and subsequent transit of virus in an apical-to-basal orientation through the polarized enterocytes into the hemocoel. In the case of insect-vectored viruses, a similar yet oppositely oriented process (basal-to-apical virus transit) occurs upon secondary infection of salivary glands, and is necessary for virus transmission to non-insect hosts. To examine this inversely oriented virus transit in these polarized tissues, we assessed the intracellular trafficking of two model viral envelope proteins (baculovirus GP64 and vesicular stomatitis virus glycoprotein, VSV G) in the midgut and salivary gland cells of the model insect, Drosophila melanogaster. Using transgenic Drosophila fly lines that inducibly express either GP64 or VSV G, we found that both proteins were trafficked basally in midgut enterocytes. In salivary gland cells, VSV G was trafficked to apical membranes in most but not all cells, whereas GP64 was trafficked consistently to basal membranes. We further examined the mechanism of polarized trafficking in midgut and salivary gland epithelia and found that a cytoplasmic YxxO motif in both VSV G and GP64 proteins is critical for basal trafficking of each envelope protein in midgut enterocytes, but dispensable for their trafficking in salivary gland epithelial cells. Using RNAi, we found that clathrin adapter protein complexes AP1 and AP3, as well as several Rab GTPases (Rab1, 4, 8, 10, 23, 30, and - 35), were involved in polarized VSV G trafficking in midgut enterocytes. Our results indicate that these viral envelope proteins encode the requisite information and require no other viral factors for appropriately polarized trafficking. In addition, they exploit tissue-specific differences in protein trafficking pathways to facilitate virus egress in the appropriate orientation for establishing systemic infections and vectoring infection to other hosts. Author SummaryViruses that use insects as hosts must navigate specific routes through the insects tissues to complete their life cycles. The routes may differ substantially depending on the life cycle of the virus. Some insect pathogenic viruses, such as baculoviruses, establish a systemic infection and this represents an endpoint in the infection cycle in the insect. In contrast, many insect-vectored viruses establish a systemic infection in the insect, but must also deliver infectious virus to the insects non-insect host. In both cases, the virus must first navigate through the midgut epithelium to establish a systemic infection, but insect-vectored viruses must also navigate through the salivary gland epithelium. Both midgut and salivary gland cells are polarized, and insect-vectored viruses appear to traffic in opposite directions in these two tissues. In this study, we asked whether two viral envelope proteins alone encode the signals necessary for polarized trafficking associated with their respective life cycles. Using two representative viral envelope proteins (VSV G and baculovirus GP64) and Drosophila as a model insect to examine tissue-specific polarized trafficking of viral envelope proteins, we identified one of the virus-encoded signals and several host proteins associated with regulating the polarized trafficking in the midgut epithelium.

microbiology↗

bioRxiv2023

The transcriptional response in mosquitoes distinguishes between fungi and bacteria but not Gram types

Mosquitoes are prolific vectors of human pathogens; a clear and accurate understanding of the organization of their antimicrobial defenses is crucial for informing the development of transmission control strategies. The canonical infection response in insects, as described in the insect model Drosophila melanogaster, is pathogen type-dependent, with distinct stereotypical responses to Gram-negative bacteria and Gram-positive bacteria/fungi mediated by the activation of the Imd and Toll pathways, respectively. To determine whether this pathogen-specific discrimination is shared by mosquitoes, we used RNAseq to capture the genome-wide transcriptional response of Aedes aegypti and Anopheles gambiae (s.l.) to systemic infection with Gram-negative bacteria, Gram-positive bacteria, yeasts, and filamentous fungi, as well as challenge with heat-killed Gram-negative, Gram-positive, and fungal pathogens. From the resulting data, we found that Ae. aegypti and An. gambiae both mount a core response to all categories of infection, and this response is highly conserved between the two species with respect to both function and orthology. When we compared the transcriptomes of mosquitoes infected with different types of bacteria, we observed that the intensity of the transcriptional response was correlated with both the virulence and growth rate of the infecting pathogen. Exhaustive comparisons of the transcriptomes of Gram-negative-challenged versus Gram-positive-challenged mosquitoes yielded no difference in either species. In Ae. aegypti, however, we identified transcriptional signatures specific to bacterial infection and to fungal infection. The bacterial infection response was dominated by the expression of defensins and cecropins, while the fungal infection response included the disproportionate upregulation of an uncharacterized family of glycine-rich proteins. These signatures were also observed in Ae. aegypti challenged with heat-killed bacteria and fungi, indicating that this species can discriminate between molecular patterns that are specific to bacteria and to fungi.

immunology↗

bioRxiv2023

Wnt/β-catenin signaling within multiple cell types dependent upon kramer regulates Drosophila intestinal stem cell proliferation

The gut epithelium is subject to constant renewal, a process reliant upon intestinal stem cell (ISC) proliferation that is driven by Wnt/{beta}-catenin signaling. Despite the importance of Wnt signaling within ISCs, the relevance of Wnt signaling within other gut cell types and the underlying mechanisms that modulate Wnt signaling in these contexts remain incompletely understood. Using challenge of the Drosophila midgut with a non-lethal enteric pathogen, we examine the cellular determinants of ISC proliferation, harnessing kramer, a recently identified regulator of Wnt signaling pathways, as a mechanistic tool. We find that Wnt signaling within Prospero-positive cells supports ISC proliferation and that kramer regulates Wnt signaling in this context by antagonizing kelch, a Cullin-3 E3 ligase adaptor that mediates Dishevelled polyubiquitination. This work establishes kramer as a physiological regulator of Wnt/{beta}-catenin signaling in vivo and suggests enteroendocrine cells as a new cell type that regulates ISC proliferation via Wnt/{beta}-catenin signaling.

cell biology↗

bioRxiv2022

A global Anopheles gambiae gene co-expression network constructed from hundreds of experimental conditions with missing values

Gene co-expression networks can be used to determine gene regulation and attribute gene function to biological processes. Different high throughput technologies, including one and two-channel microarrays and RNA-sequencing, allow evaluating thousands of gene expression data simultaneously, but these methodologies provide results that cannot be directly compared. Thus, it is complex to analyze coexpression relations between genes, especially when there are missing values arising for experimental reasons. Networks are a helpful tool for studying gene co-expression, where nodes represent genes and edges represent co-expression of pairs of genes. In this paper, we propose a method for constructing a gene co-expression network for the Anopheles gambiae transcriptome from 257 unique studies obtained with different methodologies and experimental designs. We introduce the sliding threshold approach to select node pairs with high Pearson correlation coefficients. The robustness of the method was verified by comparing edge weight distributions under random removal of conditions. The properties of the constructed network are studied in this paper, including node degree distribution, coreness, and community structure. The network core is largely comprised of genes that encode components of the mitochondrial respiratory chain and the ribosome, while different communities are enriched for genes involved in distinct biological processes. This suggests that the overall network structure is driven to maximize the integration of essential cellular functions, possibly allowing the flexibility to add novel functions.

bioinformatics↗

bioRxiv2021

A transcriptomic atlas of Aedes aegypti reveals detailed functional organization of major body parts and gut regional specializations in sugar-fed and blood-fed adult females

Mosquito vectors transmit numerous pathogens, but large gaps remain in our understanding of their physiology. To facilitate future explorations of mosquito biology, with specific attention to the major vector Aedes aegypti, we have created Aegypti-Atlas (http://aegyptiatlas.buchonlab.com/), an online resource hosting RNAseq profiles of Ae. Aegypti body parts (head, thorax, abdomen, gut, Malpighian tubules, and ovaries), gut regions (crop, proventriculus, anterior and posterior midgut, and hindgut), and a time course of blood meal digestion in the gut. Using Aegypti-Atlas, we provide new insights into the regionalization of gut function, blood feeding response, and immune defenses. We find that the anterior and posterior regions of the mosquito midgut possess clearly delineated digestive specializations which are preserved in the blood-fed state. Blood feeding initiates the sequential transcriptional induction and repression/depletion of multiple cohorts of peptidases throughout blood meal digestion. With respect to defense, immune signaling components, but not recognition or effector molecules, show enrichment in ovaries. Basal expression of antimicrobial peptides is dominated by two genes, holotricin and gambicin, that are expressed in the carcass and the digestive tissues, respectively, in a near mutually exclusive manner. In the midgut, gambicin and other immune effector genes are almost exclusively expressed in the anterior regions, while the posterior midgut exhibits the hallmarks of immune tolerance. Finally, in a cross-species comparison between the midguts of Ae. aegypti and Anopheles gambiae, we observe that regional digestive and immune specializations are closely conserved, indicating that our data may yield inferences that are broadly relevant to multiple mosquito vector species. We further demonstrate that the expression of orthologous genes is highly correlated, with the exception of a species signature comprising a small number of highly/disparately expressed genes. With this work, we show the potential of Aegypti-Atlas to unlock a more complete understanding of mosquito biology.

physiology↗

bioRxiv2021

Host-pathogen Immune Feedbacks Can Explain Widely Divergent Outcomes from Similar Infections

A longstanding question in infection biology is why two very similar individuals, with very similar pathogen exposures, may have very different outcomes. Recent experiments have found that even isogenic Drosophila melanogaster hosts, given identical inoculations of some bacterial pathogens at suitable doses, can experience very similar initial bacteria proliferation but then diverge to either a lethal infection or a sustained chronic infection with much lower pathogen load. We hypothesized that divergent infection outcomes are a natural result of mutual negative feedbacks between pathogens and the host immune response. Here we test this hypothesis in silico by constructing process-based dynamic models for bacterial population growth, host immune induction, and the feedbacks between them, based on common mechanisms of immune system response. Mathematical analysis of a minimal conceptual model confirms our qualitative hypothesis that mutual negative feedbacks can magnify small differences among hosts into life-or-death differences in outcome. However, explaining observed features of chronic infections requires an extension of the model to include induced pathogen modifications that shield themselves from host immune responses at the cost of reduced proliferation rate. Our analysis thus generates new, testable predictions about the mechanisms underlying bimodal infection outcomes.

systems biology↗

bioRxiv2020

Single Cell Analysis Reveals Multi-faceted miR-375 Regulation of the Intestinal Crypt

The role of individual miRNAs in small intestinal (SI) epithelial homeostasis is under-explored. In this study, we discovered that miR-375 is among the most enriched miRNAs in intestinal crypts and stem cells (ISCs), especially facultative ISCs. We then showed by multiple manipulations, including CRISPR/Cas9 editing, that miR-375 is strongly suppressed by Wnt-signaling. Single-cell RNA-seq analysis of SI crypt-enriched cells from miR-375 knockout (375-KO) mice revealed elevated numbers of tuft cells and increased expression of pro-proliferative genes in ISCs. Accordingly, the genetic loss of miR-375 promoted resistance to helminth infection and enhanced the regenerative response to irradiation. The conserved effects of miR-375 were confirmed by gain-of-function studies in Drosophila midgut stem cells in vivo. Moreover, functional experiments in enteroids uncovered a regulatory relationship between miR-375 and Yap1 that controls cell survival. Finally, analysis of mouse model and clinical data revealed an inverse association between miR-375 levels and intestinal tumor development. HighlightsO_LImiR-375 is one of the most enriched miRNAs in ISCs, especially facultative ISCs. C_LIO_LImiR-375 modifies tuft cell abundance and pro-proliferative gene expression in ISCs. C_LIO_LILoss of miR-375 in mice enhances the host response to helminth infection and crypt regeneration. C_LIO_LIMouse and human intestinal cancer are associated with reduced miR-375 expression. C_LI eTOC BlurbSethupathy and colleagues show that miR-375 is a Wnt-responsive, ISC-enriched miRNA that serves as a break on intestinal crypt proliferation. They also show that miR-375 modulates tuft cell abundance and pro-proliferative gene expression in ISCs, that miR-375 loss enhances the host response to helminth infection as well as crypt regeneration post-irradiation, and its reduced expression is associated with intestinal cancer.

molecular biology↗

bioRxiv2020

Gut cancer increases the risk for Drosophila to be preyed upon by hunting spiders in the laboratory

Predators are thought to prey on individuals that are in poor physical condition, although the evidence supporting this is ambiguous. We tested if sick individuals where more predated using Drosophila melanogaster flies as manipulable preys. We asked whether hunting spiders, trapped from the wild, would selectively prey upon flies with compromised health (i.e. chronically infected or cancerous) versus healthy flies under laboratory conditions. Flies chronically infected with the bacterium Providencia rettgeri, a natural Drosophila pathogen, were not selectively preyed upon by jumping spiders. We strengthened and confirmed our finding with another hunting spider species, small wolf spiders. We discuss that this result supports the hypothesis that chronic infection is associated with reduced symptoms notably to avoid the potentially deadly consequences of host predation on pathogens. We then induced colon cancer in some of the flies and asked whether the presence of cancer led to selective predation; there is little evidence for this, even in vertebrates. As the cancer developed, the incidence of predation by jumping spiders on the afflicted flies increased. We conclude that disease can have different lethal consequences through predation, even in invertebrate species, and that cancer is a factor in selective predation. Our results may explain why early tumours, but not metastasized cancers, are commonly detected in organisms in the wild, as cancer bearing individuals are rapidly eliminated due to the strong selective pressure against them.

ecology↗

bioRxiv2018

Signatures of insecticide selection in the genome of Drosophila melanogaster.

Resistance to insecticides has evolved in multiple insect species, leading to increased application rates and even control failures. Understanding the genetic basis of insecticide resistance is fundamental for mitigating its impact on crop production and disease control. We performed a GWAS approach with the Drosophila Genetic Reference Panel (DGRP) to identify the mutations involved in resistance to two widely used classes of insecticides: organophosphates (OPs, parathion) and pyrethroids (deltamethrin). Most variation in parathion resistance was associated with mutations in the target gene Ace, while most variation in deltamethrin resistance was associated with mutations in Cyp6a23, a gene encoding a detoxification enzyme never previously associated with resistance. A \"nested GWAS\" further revealed the contribution of other loci: Dscam1 and trpl were implicated in resistance to parathion, but only in lines lacking Wolbachia. Cyp6a17, the paralogous gene of Cyp6a23, and CG7627, an ATP-binding cassette transporter, were implicated in deltamethrin resistance. We observed signatures of recent selective sweeps at all of these resistance loci and confirmed that the soft sweep at Ace is indeed driven by the identified resistance mutations. Analysis of allele frequencies in additional population samples revealed that most resistance mutations are segregating across the globe, but that frequencies can vary substantially among populations. Altogether, our data reveal that the widely used OP and pyrethroid insecticides imposed a strong selection pressure on natural insect populations. However, it remains unclear why, in Drosophila, resistance evolved due to changes in the target site for OPs, but due to a detoxification enzyme for pyrethroids.\n\nArticle summaryInsecticides are widely used to control pests and insect vectors of disease. In response to the strong selection pressure exerted by insecticides, resistance has evolved in most insect species. We identified few genes present in several Drosophila melanogaster natural populations implicated in the evolution of resistance against two insecticides widely used today. We identified primary and secondary genes involved in the resistance. Surprisingly, resistance evolved in the target site for one insecticide, but was associated to changes in a novel detoxification enzyme for the other insecticide.

evolutionary biology↗