Mastodawn

📰 "The co-receptors Orco and Ir8a are required for coordinated expression of chemosensory genes in the antennae of the yellow fever mosquito, Aedes aegypti."
https://www.biorxiv.org/content/10.1101/2025.04.23.650034v1?rss=1
#DrosophilaMelanogaster
#Olfaction
#Drosophila #Sensory
#Adult

The co-receptors Orco and Ir8a are required for coordinated expression of chemosensory genes in the antennae of the yellow fever mosquito, Aedes aegypti.

Olfaction has been extensively studied in the yellow fever mosquito, Aedes aegypti. This species uses its sense of smell to find blood hosts and other resources, con-tributing to its impact as a vector for human pathogens. Two major families of pro-tein-coding genes, the odorant receptors (Ors) and the ionotropic receptors (Irs), provide the mosquito with sensitivities to distinct classes of volatile compounds in the antennae. Individual tuning receptors in both families require co-receptors for functionality, Orco for all Ors, and Ir8a for many Irs, especially ones that are involved in carboxylic acid de-tection. In Drosophila melanogaster, disruptions of Orco or Ir8a impair receptor function, tuning receptor expression, and membrane localization, leading to general anosmia. We reasoned that Orco and Ir8a might also be important for coordinated chemosensory re-ceptor expression in the antennal sensory neurons of Ae. aegypti. To test this, we performed RNAseq and differential expression analysis in wild type versus Orco-/- and Ir8a-/- mutant adult female antennae. Our analyses revealed Or and Ir tuning receptors are broadly under-expressed in Orco-/- mutants, while a subset of tuning Irs are under-expressed in Ir8a mutants. Other chemosensory and non-chemosensory genes are also dysregulated in these mutants. Further, we identify differentially expressed transcription factors in-cluding homologs of the Drosophila melanogaster Mip120 gene. These data suggest a previously unknown pleiotropic role for the Orco and Ir8a co-receptors in the coordination of expression of chemosensory receptors within the antennae of Ae. aegypti by partici-pating in a feedback loop involving amos and members of the MMB/dREAM complex. ### Competing Interest Statement The authors have declared no competing interest. National Institute of Allergy and Infectious Diseases, https://ror.org/043z4tv69, 1R01AI148300-01A1, 1R15AI156684-01

bioRxiv

flypapers 16h ago

📰 "Hangover regulates gene expression by limiting NSL-mediated H4K16 acetylation"
https://www.biorxiv.org/content/10.1101/2025.04.22.649938v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Genomics

Hangover regulates gene expression by limiting NSL-mediated H4K16 acetylation

The RNA-binding protein hangover is essential for several stress responses in Drosophila melanogaster. Here, we discover a novel function of hangover in the regulation of gene expression. Hangover binds to more than 2.000 genes in the Drosophila genome and modulates transcription. We identify a diverse set of chromatin regulators as hangover interactors, including NSL, dMec, Sin3A, dREAM and Ino80. Among these, the non-specific lethal complex (NSL) is the most prominent one. We show that hangover attenuates NSL-mediated H4K16 acetylation at transcriptional start sites to downregulate gene expression. Our work uncovers novel roles for hangover in epigenetic gene regulation and suggests that it coordinates the function of multiple chromatin regulators. ### Competing Interest Statement The authors have declared no competing interest. Deutsche Forschungsgemeinschaft, https://ror.org/018mejw64, TRR81 A01, BR2101/8

bioRxiv

flypapers 1d ago

📰 "Maturation of GABAergic signalling times the opening of a critical period in Drosophila melanogaster"
https://www.biorxiv.org/content/10.1101/2025.04.24.650400v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Sensory
#Embryo #Larva

Maturation of GABAergic signalling times the opening of a critical period in Drosophila melanogaster

The occurrence of critical periods during the development of neural networks is widely documented. Activity manipulation when these periods are open can lead to permanent, and often debilitating, effects to the mature neural network. Detailed understanding of the specific contribution of critical periods to network development, however, remains elusive. This is partly because identified critical periods in mammals are present in complex sensory networks (e.g., visual and auditory) that make focused experimental manipulation challenging. It is significant, therefore, that critical periods have been identified in simpler model systems. A critical period occurs during the development of the embryonic locomotor network in the fruit fly, Drosophila melanogaster. Perturbation of neuronal activity during this period is sufficient to permanently destabilise the mature larval locomotor network: leaving it prone to induced seizures. Given a clear role of γ-aminobutyric acid (GABA) in the timing of the mammalian critical period of ocular dominance, we sought to establish whether this neurotransmitter also regulates the opening of the Drosophila locomotor critical period. Utilising GABA agonists, antagonists, and genetics, we manipulated the embryonic GABAergic system and, at the end of larval life, measured an induced seizure phenotype in mature third-instar larvae. We found that potentiating GABAergic signalling, via embryonic exposure to diazepam or overexpression of the GABAA receptor rdl, induced precocious opening of the critical period. By contrast, exposure to the GABA antagonist gabazine, or knockdown of the GABA-synthetic enzyme Gad1, delayed opening. Thus, we show that critical period timing within the Drosophila CNS is dictated by GABAergic signalling, indicating a phylogenetically conserved role. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers 1d ago

📰 "Drosophila SA1 expression prevents brain tumorigenesis and PARP-mediated cell elimination"
https://www.biorxiv.org/content/10.1101/2025.04.18.649500v1?rss=1
#DrosophilaMelanogaster
#Drosophila

Drosophila SA1 expression prevents brain tumorigenesis and PARP-mediated cell elimination

The cohesin complex performs essential cellular functions including regulation of chromosome cohesion, chromatin organization and DNA repair. Somatic pathogenetic variants in cohesin genes, such as STAG2, have been associated with cancer, but their contribution to brain tumorigenesis is unclear. Here, we report the presence of STAG2 variants in glioblastoma and medulloblastoma patients and determine that loss of STAG2 in human cells leads to DNA damage and apoptosis. Treatment with inhibitors of the Poly ADP-ribose polymerase (PARP), which are used to treat forms of cancer with defects in DNA repair, increased the amount of apoptosis, confirming that synthetic lethality between reduced cohesin and PARP activity could be observed in vitro. Similar results were obtained in vivo by reducing expression of SA1, the Drosophila melanogaster homolog of STAG1/2. Cohesin gene silencing during fly brain development leads to defects in neural stem cells differentiation and tumorigenesis both in the presence of oncogenic activity and per se. Our in vivo and in vitro data suggests that impairment of PARP activity might induce synthetic lethality in cohesin-dependent tumors, highlighting a vulnerability that can be pharmacologically exploited. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers 2d ago

📰 "Bigger is not always better: size-dependent fitness effects of adult crowding in Drosophila melanogaster"
https://www.biorxiv.org/content/10.1101/2025.04.21.649761v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Evolution
#Adult
#Larva

Bigger is not always better: size-dependent fitness effects of adult crowding in Drosophila melanogaster

Density-dependent selection is an important factor shaping the evolution of life histories. In holometabolous insects, crowding in the larval and adult stages can have very different effects on key fitness components. While the nuanced effects of density-dependent selection through larval crowding in Drosophila melanogaster have been extensively studied for various life history traits, very few studies have investigated the effects of adult crowding in Drosophila. Moreover, these few studies were mostly conducted on large flies, derived from low larval density cultures, and typically treated the overall density of flies per culture container as an index of the strength of adult crowding. We hypothesized that the size of the adults should shape the impact of adult crowding, with small individuals experiencing less stress than large individuals when crowded. Consequently, the adverse fitness effects usually associated with adult crowding may not be observed for small individuals. We tested this hypothesis by subjecting flies of different sizes, regular-sized flies, and small flies derived via larval crowding or selection for rapid development to adulthood, to an episode of adult crowding and examining their mortality and fecundity. Thus, we explored the interactive effects between larval and adult crowding on key fitness components. Small body size enabled flies to handle adult crowding better, with significantly lower mortality under crowded conditions when compared to flies of large body size. Moreover, small flies showed a consistent pattern of increased fecundity upon adult crowding. This positive impact on fecundity was not observed when larger flies were crowded. It is clear from our study that the effects of adult crowding can be very nuanced and body size-specific, even to the extent of having a net beneficial effect on fitness components, contrary to previous belief. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers 3d ago

📰 "A conserved, immune-regulated peritrophin promotes Vibrio cholerae colonization of the arthropod intestine"
https://www.biorxiv.org/content/10.1101/2025.04.21.649765v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Immunity

A conserved, immune-regulated peritrophin promotes Vibrio cholerae colonization of the arthropod intestine

Abstract Vibrio cholerae is a human diarrheal pathogen and an estuarine organism that associates with both terrestrial and aquatic arthropods. Using the model terrestrial arthropod Drosophila melanogaster, we previously showed that V. cholerae forms a multi-layered bacterial structure called a biofilm in the arthropod intestine and activates the arthropod intestinal innate immune response. Here we show that activation of the immune response in enterocytes decreases V. cholerae colonization of the arthropod intestine, while activation of the immune response in enteroendocrine cells that express the enteroendocrine peptide tachykinin (Tk) promotes V. cholerae colonization. To uncover the basis of this observation, we measured the impact of TkRNAi on intestinal gene expression by RNA-seq analysis. In addition to increasing expression of antimicrobial peptides and lipases, Tk activated the expression of chitinases and chitin-binding proteins. These proteins interact with chitin fibrils in the peritrophic matrix (PM), a protective coating that overlies the arthropod intestinal epithelium. One of these Tk-activated PM components, the small, secreted chitin-binding protein Peritrophin 15a (Peri-15a), is essential for robust V. cholerae colonization of the gut. Homologs of Peri-15a are widespread in both terrestrial and aquatic organisms including marine non-biting midges, marine copepods, rotifers, and cyanobacteria. We propose that Peri-15a and its homologs, found in the intestines of diverse arthropods, either serves as a receptor or reveals a PM epitope that promotes V. cholerae attachment to the intestinal surface. Therefore, activation of the enteroendocrine cell intestinal innate immune response by V. cholerae may, in fact, represent a colonization strategy. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers 5d ago

📰 "Before the Black Box"
https://www.biorxiv.org/content/10.1101/2025.04.14.648839v1?rss=1
#DrosophilaMelanogaster
#Drosophila

Before the Black Box

Ecdysteroid hormones are responsible for regulating arthropod moulting, but unlike other taxa which used sterol-derived hormones (e.g. vertebrate sex-determining hormones), arthropods cannot synthesis sterols de novo. Ecdysteroid synthesis is thus dependent on funnelling diverse dietary sterols into the conserved reactions of ecdysteroidogenesis. While the later steps of ecdysteroid synthesis are dominated by cytochrome P450s, earlier stages of this pathway (i.e. those acting in or before the Black Box in which 7-dehydrocholesterol is converted to 5,22,25-trideoxyecdysone) involve more diverse enzymes. While numerous comparative analysis of arthropod cytochrome P450s have been conducted, little comparable work has been done on the pre-Black Box FAD-dependent oxidoreductase DHCR24 and the Rieske domain oxygenase Neverland and the Black Box short-chain dehydrogenase/reductase Shroud. However, there is some evidence for evolutionary shifts among these enzymes across arthropods, e.g. the absence of DHCR24 from Drosophila melanogaster. We have sought to systematically identify such changes in copy number in DHCR24, Neverland and Shroud across arthropods, as well as to identify correlations between these changes and dietary factors with reference to the literature. Among other results, we find that Neverland is absent from all beetles (providing support for mycophagy as an important element of the beetle ancestral diet) and that losses of DHCR24 correlate with production of alkylated ecdysteroids. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers Apr 16

📰 "Intestinal Tissue Mechanics Regulate Angiogenesis and Stem Cell Proliferation via Vascular Piezo"
https://www.biorxiv.org/content/10.1101/2025.04.16.649133v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Adult

Intestinal Tissue Mechanics Regulate Angiogenesis and Stem Cell Proliferation via Vascular Piezo

The vasculature is a prominent component of developmental and adult tissue microenvironments. How, tissue specific characteristics and environmental states influence vascular biology and function, remains largely understudied. Previously, we discovered crosstalk between the adult intestinal epithelium and the vasculature-like tracheal system of the fruit fly Drosophila melanogaster, which is driven by reactive oxygen species (ROS) during pathogen induced-intestinal regeneration. However, chemical stress signals alone are insufficient to explain the rich diversity of vasculature/tissue interactions in living systems and justify the widely observed adaptation of the vascular network in physiology and disease. Here, we uncover reciprocal, mechanochemical interorgan communication between the adult intestine and its vascular niche, which shapes vascular and epithelial tissue adaptations and drives stem cell proliferation during intestinal regeneration and tumour growth. Mechanistically, apoptotic epithelial cells within the regenerating intestine induce local and global mechanical changes in the gut, which results in activation and upregulation of the mechanosensitive ion channel Piezo in a subset of gut-associated trachea. Piezo drives a specific molecular program within the trachea through activation of the mechanosensitive transcription factor Yorkie/YAP, leading to tracheal remodelling and intestinal stem cell proliferation. Furthermore, we identify a non-redundant role of vascular Piezo1 driving remodelling of the intestinal crypt vasculature and inducing crypt growth, WNT signalling activity, and stem cell proliferation in the regenerating mouse small intestine. Our cross-species in vivo study reveals previously unrecognised mechanosensory regulation of intestinal regeneration and tumourigenesis through the vascular-stem cell niche and highlights the importance of studying tissue and context specific vascular cell biology to understand intestinal plasticity and the complexity of tissue/vasculature interactions within a living organ. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers Apr 16

📰 "IbinA and IbinB regulate the Toll pathway-mediated immune response in Drosophila melanogaster"
https://www.biorxiv.org/content/10.1101/2025.04.10.648149v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Immunity #Toll
#Pupa

IbinA and IbinB regulate the Toll pathway-mediated immune response in Drosophila melanogaster

To combat infection, an immune system needs to be promptly activated but tightly controlled to avoid destructive effects on host tissues. IbinA and IbinB are related short peptides with robust expression upon microbial challenge in Drosophila melanogaster . Here, we show that Ibin genes are ubiquitously present in flies of the Drosophila subgenus Sophophora , where they replace a different but probably related gene, Mibin , which is found across a much wider range of cyclorrhaphan flies. Using synthetic peptides, we did not observe any direct bactericidal or bacteriostatic activity for either IbinA or IbinB in vitro. Using mutant Drosophila lines lacking the IbinA gene, IbinB gene, or both, we examined their roles in development and during microbial infections. IbinA is expressed in early pupae, and a lack of IbinA and IbinB leads to temperature-dependent formation of melanized tissue during metamorphosis, frequently around the trachea. IbinA and IbinB have distinct effects on susceptibility to microbial infection. For example, IbinB mutant flies, as well as flies lacking both IbinA and IbinB , had improved survival when challenged with Listeria monocytogenes, an intracellular pathogen, whereas a lack of IbinA alone had no effect. RNA sequencing of wildtype and mutant flies infected with L. monocytogenes showed enhanced Toll target gene expression in flies lacking IbinB , suggesting that IbinB acts as a negative regulator of the Toll pathway. In contrast, IbinA mutants had decreased Toll target gene expression in this context. Correspondingly, IbinB mutant flies had improved and IbinA compromised survival in septic fungal infection, where the Toll pathway has a major role. Our study provides insight into the roles of IbinA and IbinB in regulation of the immune response in Drosophila. ### Competing Interest Statement The authors have declared no competing interest.

bioRxiv

flypapers Apr 16

📰 "Super Recombinator (SuRe): An in vivo recombination system for scalable and efficient transgene assembly at a single genomic locus"
https://www.biorxiv.org/content/10.1101/2025.04.15.646138v1?rss=1
#DrosophilaMelanogaster
#Drosophila #Genomics

Super Recombinator (SuRe): An in vivo recombination system for scalable and efficient transgene assembly at a single genomic locus

The capacity to engineer organisms with multiple transgenic components is crucial to synthetic biology and basic biology research. For the former field, transgenic organisms allow the creation of novel biological functions; for the latter, such organisms provide potent means of dissecting complex biological pathways. However, the size limitations of a single transgenesis event and challenges associated with the assembly of multiple DNA fragments hinder the efficient integration of multiple transgenes. To overcome these hurdles, here we introduce a building block for synthetic design termed an integrated genetic array (IGA), which incorporates all genetic components into a single locus to prevent their separation during genetic manipulations. Since the natural recombination rate for genes located in the same locus is near zero, to construct IGAs we developed the Super Recombinator (SuRe) system, which uses CRISPR/Cas9, alone or in combination with site-specific serine recombinases, for in vivo transgene recombination at a single genomic locus. SuRe effectively doubles the number of elements assembled in each recombination round, exponentially accelerating IGA construction. By preventing the separation of transgenic elements, SuRe greatly reduces screening burdens, as validated here through studies of Drosophila melanogaster and Caenorhabditis elegans. To optimize SuRe, we compared CRISPR/Cas9-induced homology-directed recombination to site-specific recombination using various serine recombinases. Optimized versions of SuRe achieved efficiency and fidelity values near their theoretical maxima and allowed the generation of recombinant products up to 4.2 Mbp in size in Drosophila. Using SuRe, we created fruit flies with 12 transgenic elements for fluorescence voltage imaging of neural activity in precisely defined cell types. Mathematical modeling of the scalability of SuRe to large transgene assemblies showed that integration times and gene assembly workloads respectively scale logarithmically and linearly with the number of transgenes, both major improvements over conventional approaches. Overall, SuRe enables the efficient integration of multiple genes at individual loci, up to the chromosomal scale. ### Competing Interest Statement The authors of this manuscript (J Luo, MJ Schnitzer, C Huang) are also inventors on the related patent application "Genetic tools for recombining transgenes at the same locus" (US Patent App. 18/248,978, 2023).

bioRxiv