Biology subjects

Wu, M.

Publications and source records attributed to Wu, M..

At least 163 records · Page 9Linked to original sources

bioRxiv2023

CodonBERT: Large Language Models for mRNA Design and Optimization

AO_SCPLOWBSTRACTC_SCPLOWmRNA based vaccines and therapeutics are gaining popularity and usage across a wide range of conditions. One of the critical issues when designing such mRNAs is sequence optimization. Even small proteins or peptides can be encoded by an enormously large number of mRNAs. The actual mRNA sequence can have a large impact on several properties including expression, stability, immunogenicity, and more. To enable the selection of an optimal sequence, we developed CodonBERT, a large language model (LLM) for mRNAs. Unlike prior models, CodonBERT uses codons as inputs which enables it to learn better representations. CodonBERT was trained using more than 10 million mRNA sequences from a diverse set of organisms. The resulting model captures important biological concepts. CodonBERT can also be extended to perform prediction tasks for various mRNA properties. CodonBERT outperforms previous mRNA prediction methods including on a new flu vaccine dataset.

bioinformatics↗

bioRxiv2023

Bacterial Sphingolipids Exacerbate Colitis by Inhibiting ILC3-derived IL-22 Production.

Commensal bacteria of the Bacteroidetes phylum are the primary producers of sphingolipids in the gut lumen. These lipids serve dual roles as bacterial virulence factors and regulators of the host mucosal immune system, including regulatory T cells and invariant natural killer T cells (iNKT). Sphingolipid composition is significantly altered in fecal samples of patients with inflammatory bowel disease (IBD). However, the specific mechanisms by which bacterial sphingolipids modulate mucosal homeostasis and regulate intestinal inflammation remain unclear. In this study, we investigated the impact of bacterial sphingolipids on intestinal inflammation by mono-colonizing mice with Bacteroides fragilis strains that either express or lack sphingolipids during DSS-induced colitis. We discovered that B. fragilis sphingolipids exacerbate intestinal inflammation. Mice mono-colonized with B. fragilis lacking sphingolipids exhibited less severe DSS-induced colitis. This amelioration of colitis was associated with increased production of interleukin-22 (IL-22) by innate lymphoid cell type 3 (ILC3). Consistent with the inhibitory effect of sphingolipids on IL-22 production, mice colonized with B. fragilis lacking sphingolipids showed enhanced epithelial STAT3 activity, intestinal cell proliferation, and antimicrobial peptide production following DSS treatment compared to those colonized with B. fragilis producing sphingolipids. Additionally, colitis severity in mice colonized with B. fragilis lacking sphingolipids was exacerbated upon IL-22 blockade. Furthermore, our study reveals that bacterial sphingolipids restrict epithelial IL-18 production following DSS treatment and interfere with IL-22 production by a subset of ILC3 cells expressing both the interleukin-18 receptor (IL-18R) and major histocompatibility complex class II (MHC II). These findings indicate that B. fragilis-derived sphingolipids exacerbate mucosal inflammation by impeding epithelial IL-18 expression, resulting in compromised production of IL-22 by ILC3 cells. HighlightsO_LIB. fragilis-derived sphingolipids exacerbate DSS-induced colitis in mono-colonized C57BL/6 mice. C_LIO_LIB. fragilis-derived sphingolipids constrain ILC3-derived IL-22, leading to reduced colonic epithelial cell proliferation and compromised barrier function. C_LIO_LIB. fragilis-derived sphingolipids restrict epithelial NLRC4 inflammasome activation and IL-18 secretion. C_LIO_LIB. fragilis-derived sphingolipids modulate IL-22 production by IL18R+ MHC II+ ILC3s. C_LI

immunology↗

bioRxiv2023

β1 integrins regulate cellular behaviors and cardiomyocyte organization during ventricular wall formation

AimsThe mechanisms regulating the cellular behavior and cardiomyocyte organization during ventricular wall morphogenesis are poorly understood. Cardiomyocytes are surrounded by extracellular matrix (ECM) and interact with ECM via integrins. This study aims to determine whether and how {beta}1 integrins regulate cardiomyocyte behavior and organization during ventricular wall morphogenesis in the mouse. Methods and ResultsWe applied mRNA deep sequencing and immunostaining to determine the expression repertoires of /{beta} integrins and their ligands in the embryonic heart. Integrin {beta}1 subunit ({beta}1) and some of its ECM ligands are asymmetrically distributed and enriched in the luminal side of cardiomyocytes, while fibronectin surrounds cardiomyocytes, creating a network for them. Itgb1, which encodes the {beta}1 integrin subunit, was deleted via Nkx2.5Cre/+ to generate myocardial-specific Itgb1 knockout (B1KO) mice. B1KO hearts display an absence of trabecular zone but a thicker compact zone. The abundances of hyaluronic acid and versican are not significantly different. Instead, fibronectin, a ligand of {beta}1, was absent in B1KO. We examined cellular behaviors and organization via various tools. B1KO cardiomyocytes display a random cellular orientation and fail to undergo perpendicular cell division, be organized properly, and establish the proper tissue architecture to form trabeculae. The reduction of Notch1 activation was not the cause of the abnormal cellular organization in B1KO hearts. Mosaic clonal lineage tracing shows that Itgb1 regulates cardiomyocyte transmural migration and proliferation autonomously. Conclusions{beta}1 is asymmetrically localized in the cardiomyocytes, and its ECM ligands are enriched in the luminal side of the myocardium and surrounding cardiomyocytes. {beta}1 integrins are required for cardiomyocytes to attach to the ECM network. This engagement provides structural support for cardiomyocytes to maintain shape, undergo perpendicular division, and establish cellular organization. Deletion of Itgb1, leading to ablation of {beta}1 integrins, causes the dissociation of cardiomyocytes from the ECM network and failure to establish tissue architecture to form trabeculae.

developmental biology↗

bioRxiv2023

Nitrate-driven anaerobic oxidation of ethane and butane by bacteria

The short-chain gaseous alkanes (ethane, propane and butane; SCGAs) are important components of natural gas, yet our understanding of their fate in environmental systems is poorly understood. Microbially mediated anaerobic oxidation of SCGAs coupled to nitrate reduction has been demonstrated for propane, but is yet to be shown for ethane or butane - despite being energetically feasible. Here we report two independent bacterial enrichments performing anaerobic ethane and butane oxidation, respectively, coupled to nitrate reduction to dinitrogen gas and ammonium. Isotopic 13C-and 15N-labelling experiments, mass and electron balance tests, and metabolite and meta-omics analyses collectively reveal that the recently described propane-oxidising Candidatus Alkanivorans nitratireducens was also responsible for nitrate-dependent anaerobic oxidation of the SCGAs in both these enrichments. The complete genome of this species encodes alkylsuccinate synthase genes for the activation of ethane/butane via fumarate addition. Further substrate range tests confirm Ca. A. nitratireducens is metabolically versatile, being able to degrade ethane, propane and butane under anaerobic conditions. Moreover, our study proves nitrate as an additional electron sink for ethane and butane in anaerobic environments, and for the first time demonstrates the use of the fumarate addition pathway in anaerobic ethane oxidation. These findings significantly contribute to our understanding of microbial metabolism of SCGAs in anaerobic environments.

microbiology↗

bioRxiv2023

Search and Match across Spatial Omics Samples at Single-cell Resolution

Spatial omics technologies characterize tissue molecular properties with spatial information, but integrating and comparing spatial data across different technologies and modalities is challenging. A comparative analysis tool that can search, match, and visualize both similarities and differences of molecular features in space across multiple samples is lacking. To address this, we introduce CAST (Cross-sample Alignment of SpaTial omics), a deep graph neural network (GNN)-based method enabling spatial-to-spatial searching and matching at the single-cell level. CAST aligns tissues based on intrinsic similarities of spatial molecular features and reconstructs spatially resolved single-cell multi-omic profiles. CAST enables spatially resolved differential analysis ({Delta}Analysis) to pinpoint and visualize disease-associated molecular pathways and cell-cell interactions, and single-cell relative translational efficiency (scRTE) profiling to reveal variations in translational control across cell types and regions. CAST serves as an integrative framework for seamless single-cell spatial data searching and matching across technologies, modalities, and disease conditions, analogous to BLAST in sequence alignment.

bioinformatics↗

bioRxiv2023

The essential genome of Xanthomonas citri

Citrus canker, caused by the bacterium Xanthomonas citri subsp. citri, is a devastating disease with significant economic implications for the citrus industry worldwide. Understanding the molecular basis of Xanthomonas cell cycle and identifying therapeutic targets is crucial for effective disease management. In this study, we employed hyper-saturated transposon mutagenesis combined with high-throughput sequencing to determine the essential features of the Xanthomonas citri genome at [~]7-bp resolution. Our analysis revealed 525 essential genes, 181 high fitness cost genes, 7 small non-coding RNAs, 25 transfer RNAs, 4 ribosomal RNAs, and the origin of replication. Notably, the use of a newly designed Tn5 transposon with an outward pointing lac promoter significantly reduced false positives caused by polar effects associated with conventional transposons. Functional enrichment analysis showed that essential genes were significantly enriched in processes related to ribosome biogenesis, energy production and conversion, and membrane metabolism. Interestingly, the distribution of essential genes in X. citri showed similarities to that of the model organism E. coli, suggesting a conserved mode of genome organization that influences transposon accessibility. Our comprehensive analysis provides valuable target genes for potential therapeutic interventions against citrus canker and other related plant diseases.

microbiology↗

bioRxiv2023

Collective dynamics of formin and microtubule and its crosstalk mediated by FHDC1

The coordination between actin and microtubule network is crucial, yet our understanding of the underlying mechanisms remains limited. In this study, we used travelling waves in the cell cortex to characterize the collective dynamics of cytoskeletal networks. Our findings show that Cdc42 and F-BAR-dependent actin waves in mast cells are mainly driven by formin-mediated actin polymerization, with the microtubule-binding formin FH2 domain-containing protein 1 (FHDC1) identified as an early regulator. The depolymerization of microtubules coincides with the nucleation of actin waves, and the concurrent release of FHDC1 from microtubule is required for actin waves. Lastly, we show the importance of the actin-microtubule linkage mediated by FHDC1 in crucial cellular processes such as cell division and migration. Our data provided molecular insights into the nucleation mechanisms of actin waves and uncover an antagonistic interplay between microtubule and actin polymerization in their collective dynamics.

cell biology↗

bioRxiv2023

Mitigating autocorrelation during spatially resolved transcriptomics data analysis

Several computational methods have recently been developed for characterizing molecular tissue regions in spatially resolved transcriptomics (SRT) data. However, each method fundamentally relies on spatially smoothing transcriptomic features across neighboring cells. Here, we demonstrate that smoothing increases autocorrelation between neighboring cells, causing latent space to encode physical adjacency rather than spatial transcriptomic patterns. We find that randomly sub-sampling neighbors before smoothing mitigates autocorrelation, improving the performance of existing methods and further enabling a simpler, more efficient approach that we call spatial integration (SPIN). SPIN leverages the conventional single-cell toolkit, yielding spatial analogies to each tool: clustering identifies molecular tissue regions; differentially expressed gene analysis calculates region marker genes; trajectory inference reveals continuous, molecularly defined ana tomical axes; and integration allows joint analysis across multiple SRT datasets, regardless of tissue morphology, spatial resolution, or experimental technology. We apply SPIN to SRT datasets from mouse and marmoset brains to calculate shared and species-specific region marker genes as well as a molecularly defined neocortical depth axis along which several genes and cell types differ across species.

bioinformatics↗

bioRxiv2023

The universal suppressor mutation in the HSV-1 nuclear egress complex restores membrane budding defects by stabilizing the oligomeric lattice

Nuclear egress is an essential process in herpesviral replication whereby nascent capsids translocate from the nucleus to the cytoplasm. This initial step of nuclear egress - budding at the inner nuclear membrane - is coordinated by the nuclear egress complex (NEC). Composed of the viral proteins UL31 and UL34, NEC deforms the membrane around the capsid as the latter buds into the perinuclear space. NEC oligomerization into a hexagonal membrane-bound lattice is essential for budding because mutations designed to perturb lattice interfaces reduce its budding ability. Previously, we identified an NEC suppressor mutation capable of restoring budding to a mutant with a weakened hexagonal lattice. Here, we show that the suppressor mutation can restore budding to a broad range of budding-deficient NEC mutants thereby acting as a universal suppressor. We demonstrate that the suppressor mutation indirectly promotes the formation of new contacts between the NEC hexamers that, ostensibly, stabilize the hexagonal lattice. This stabilization strategy is powerful enough to override the otherwise deleterious effects of mutations that destabilize the NEC lattice by different mechanisms, resulting in a functional NEC hexagonal lattice and restoration of membrane budding.

biophysics↗

bioRxiv2023

Polarized Mechanosensitive Signaling Domains Protect Arterial Endothelial Cells Against Inflammation

Endothelial cells (ECs) in the descending aorta are exposed to high laminar shear stress, which supports an anti-inflammatory phenotype that protects them from atherosclerosis. High laminar shear stress also supports flow-aligned cell elongation and front-rear polarity, but whether this is required for athero-protective signaling is unclear. Here, we show that Caveolin-1-rich microdomains become polarized at the downstream end of ECs exposed to continuous high laminar flow. These microdomains are characterized by higher membrane rigidity, filamentous actin (F-actin) and lipid accumulation. Transient receptor potential vanilloid-type 4 (Trpv4) ion channels, while ubiquitously expressed, mediate localized Ca2+ entry at these microdomains where they physically interact with clustered Caveolin-1. The resultant focal bursts in Ca2+ activate the anti-inflammatory factor endothelial nitric oxide synthase (eNOS) within the confines of these domains. Importantly, we find that signaling at these domains requires both cell body elongation and sustained flow. Finally, Trpv4 signaling at these domains is necessary and sufficient to suppress inflammatory gene expression. Our work reveals a novel polarized mechanosensitive signaling hub that induces an anti-inflammatory response in arterial ECs exposed to high laminar shear stress.

cell biology↗

bioRxiv2023

TPR domain assigns versatility of BcTir/Tpr system against viral infection

NAD+-derived signal produced by TIR domain triggered the host immune responses. The ubiquitous TPR domain involved in signal recognition and effector activation were found widely assembled with the TIR domain. However, the immune roles of these assemblies remain elusive. Here, a two-gene operon, one containing a TIR domain, designated as BcTir, and the other, BcTpr, from Bacillus cereus, exhibited anti-phage immunity. BcTpr, but not BcTir, exhibited NADase activity to produce the cyclic ADPR (cADPR) isomer and mediate NAD+ depletion. Noticeably, the truncated N terminus of BcTpr only depleted NAD+ unless at the presence of TPR domain to generate cADPR isomer unveiling its role played for glycosite selection. In addition, the BcTir/Tpr system significantly repressed viral proliferation and increased oxidation resistance by scavenging excessive reactive oxygen species (ROS) upon phage infection. These findings unraveled a multifunctional role of the BcTir/Tpr system during immune responses. In BriefThe bacterial BcTir/Tpr system was identified with the ability to protect against phage infection via NAD+ depletion, viral replication repression, and ROS homeostasis, in which BcTpr played a dual role in NAD+-derived signal production and NAD+ depletion. HighlightsO_LIThe BcTir/Tpr system works as a BcTir-BcTpr complex against phage infection. C_LIO_LIBcTpr, instead of BcTir, generates the NAD+-derived cADPR isomer through its glycosidase domain at N terminus. C_LIO_LIThe amount of cADPR isomer production is regulated by the helix numbers of the TPR domain at C terminus of BcTpr. C_LIO_LIThe BcTir/Tpr system can depress phage proliferation and decrease ROS production upon phage infection. C_LI

microbiology↗

bioRxiv2023

Functional and metagenomic level diversities of human gut symbiont-derived glycolipids

Bioactive metabolites produced by symbiotic microbiota causally impact host health and disease, nonetheless, incomplete functional annotation of genes as well as complexities and dynamic nature of microbiota make understanding species-level contribution in production and actions difficult. Alpha-galactosylceramides produced by Bacteroides fragilis (BfaGC) are one of the first modulators of colonic immune development, but biosynthetic pathways and the significance of the single species in the symbiont community still remained elusive. To address these questions at the microbiota level, we have investigated the lipidomic profiles of prominent gut symbionts and the metagenome-level landscape of responsible gene signatures in the human gut. We first elucidated the chemical diversity of sphingolipid biosynthesis pathways of major bacterial species. In addition to commonly shared ceramide backbone synthases showing two distinct intermediates, alpha-galactosyltransferase (agcT), the necessary and sufficient component for BfaGC production and host colonic type I natural killer T (NKT) cell regulation by B. fragilis, was characterized by forward-genetics based targeted metabolomic screenings. Phylogenetic analysis of agcT in human gut symbionts revealed that only a few ceramide producers have agcT and hence can produce aGCs, on the other hand, structurally conserved homologues of agcT are widely distributed among species lacking ceramides. Among them, alpha-glucosyl-diacylglycerol(aGlcDAG)-producing glycosyltransferases with conserved GT4-GT1 domains are one of the most prominent homologs in gut microbiota, represented by Enterococcus bgsB. Of interest, aGlcDAGs produced by bgsB can antagonize BfaGC-mediated activation of NKT cells, showing the opposite, lipid structure-specific actions to regulate host immune responses. Further metagenomic analysis of multiple human cohorts uncovered that the agcT gene signature is almost exclusively contributed by B. fragilis, regardless of age, geographical and health status, where the bgsB signature is contributed by >100 species, of which abundance of individual microbes is highly variable. Our results collectively showcase the diversities of gut microbiota producing biologically relevant metabolites in multiple layers-biosynthetic pathways, host immunomodulatory functions and microbiome-level landscapes in the host.

microbiology↗

bioRxiv2023

Single Cell RNA Sequencing Reveals Emergent Notochord-Derived Cell Subpopulations in the Postnatal Nucleus Pulposus

Intervertebral disc degeneration is a leading cause of chronic low back pain. Cell-based strategies that seek to treat disc degeneration by regenerating the central nucleus pulposus hold significant promise, but key challenges remain. One of these is the inability of therapeutic cells to effectively mimic the performance of native nucleus pulposus cells, which are unique amongst skeletal cell types in that they arise from the embryonic notochord. In this study we use single cell RNA sequencing to demonstrate emergent heterogeneity amongst notochord-derived nucleus pulposus cells in the postnatal mouse disc. Specifically, we established the existence of early and late stage nucleus pulposus cells, corresponding to notochordal progenitor and mature cells, respectively. Late stage cells exhibited significantly higher expression levels of extracellular matrix genes including aggrecan, and collagens II and VI, along with elevated TGF-{beta} and PI3K-Akt signaling. Additionally, we identified Cd9 as a novel surface marker of late stage nucleus pulposus cells, and demonstrated that these cells were localized to the nucleus pulposus periphery, increased in numbers with increasing postnatal age, and co-localized with emerging glycosaminoglycan-rich matrix. Finally, we used a goat model to show the Cd9+ nucleus pulposus cell numbers decrease with moderate severity disc degeneration, suggesting that these cells are associated with maintenance of the healthy nucleus pulposus extracellular matrix. Improved understanding of the developmental mechanisms underlying regulation of ECM deposition in the postnatal NP may inform improved regenerative strategies for disc degeneration and associated low back pain.

cell biology↗

bioRxiv2023

Periodicity, Mixed-Mode Oscillations, and Multiple Timescale in a Phosphoinositide-Rho GTPase Network

While rhythmic contractile behavior is prevalent on the cortex of living cells, current experimental observation and mechanistic understanding primarily tackle a small subset of dynamical behavior including excitable or periodic events that can be described by simple activator-delayed inhibitor mechanisms. In this work we found that the oscillatory activation of Rho GTPase in nocodazole-treated mitotic rat basophilic leukemia (RBL) cells exhibited both simple and complex mixed-mode oscillations, with periodicity ranging from 30 sec to 5 min. Complex mixed-mode oscillations require at least two instability-generating mechanisms. We show that Rho oscillations at the fast timescale (20-30 sec) is regulated by phosphatidylinositol (3,4,5)-trisphosphate (PIP3) via an activator-delayed inhibitor mechanism, while the period of the slow reaction (minutes) is regulated by phosphatidylinositol 4-phosphate (PI(4)P) via an activator-substrate depletion mechanism where replenishment of phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) is rate-limiting. Conversion from simple to complex oscillations could be induced by modulating PIP3 metabolism or membrane contact site dynamics. In particular, a period-doubling intermediate can be captured by PTEN depletion. Both period doubling and mixed-mode oscillations are intermediate states towards chaos. Collectively, these results suggest that phosphoinositide-Rho GTPase signaling network is poised at the edge of chaos and small parameter changes in the phosphoinositide metabolism network could confer cells the flexibility to rapidly transit into a number of ordered states with different periodicities.

cell biology↗

bioRxiv2023

Brain-wide Correspondence Between Neuronal Epigenomics and Long-Distance Projections

Single-cell genetic and epigenetic analyses parse the brains billions of neurons into thousands of "cell-type" clusters, each residing in different brain structures. Many of these cell types mediate their unique functions by virtue of targeted long-distance axonal projections to allow interactions between specific cell types. Here we have used Epi-Retro-Seq to link single cell epigenomes and associated cell types to their long-distance projections for 33,034 neurons dissected from 32 different source regions projecting to 24 different targets (225 source [->]target combinations) across the whole mouse brain. We highlight uses of this large data set for interrogating both overarching principles relating projection cell types to their transcriptomic and epigenomic properties and for addressing and developing specific hypotheses about cell types and connections as they relate to genetics. We provide an overall synthesis of the data set with 926 statistical comparisons of the discriminability of neurons projecting to each target for every dissected source region. We integrate this dataset into the larger, annotated BICCN cell type atlas composed of millions of neurons to link projection cell types to consensus clusters. Integration with spatial transcriptomic data further assigns projection-enriched clusters to much smaller source regions than afforded by the original dissections. We exemplify these capabilities by presenting in-depth analyses of neurons with identified projections from the hypothalamus, thalamus, hindbrain, amygdala, and midbrain to provide new insights into the properties of those cell types, including differentially expressed genes, their associated cis-regulatory elements and transcription factor binding motifs, and neurotransmitter usage.

neuroscience↗

bioRxiv2023

Multimodal acoustic-electric trigeminal nerve stimulation modulates conscious perception

Multimodal stimulation has the potential to reverse pathological neural activity and alleviate symptoms in neuropsychiatric diseases. However, the reliability of this approach and the mechanisms through which it improves consciousness remain largely unknown. We investigated the effects of multimodal stimulation combining music stimulation with electrical trigeminal nerve stimulation in healthy human participants. We assessed conscious perception before and after acoustic-electric stimulation and investigated the mechanisms underlying the putative stimulation effects. Our results show that (1) acoustic-electric stimulation improves conscious tactile perception in healthy human participants without a concomitant change in auditory perception, (2) this improvement is caused by the interplay of the acoustic and electric stimulation rather than any of the unimodal stimulation alone, and (3) the effect of acoustic-electric stimulation on conscious perception correlates with inter-regional connection changes in a recurrent neural processing model. These findings provide evidence that multimodal acoustic-electric stimulation can promote conscious perception and offer insights into its underlying mechanisms.

neuroscience↗

bioRxiv2023

Optical coherence tomography of human fetal membrane sub-layers during dynamic loading

Fetal membranes have important mechanical and antimicrobial roles in maintaining pregnancy. However, the small thickness (<800 m) of fetal membranes places them outside the resolution limits of most ultrasound and magnetic resonance systems. Optical imaging methods like optical coherence tomography (OCT) have the potential to fill this resolution gap. Here, OCT and machine learning methods were developed to characterize the ex vivo properties of human fetal membranes under dynamic loading. A saline inflation test was incorporated into an OCT system, and tests were performed on n=33 and n=32 human samples obtained from labored and C-section donors, respectively. Fetal membranes were collected in near-cervical and near-placental locations. Histology, endogenous two photon fluorescence microscopy, and second harmonic generation microscopy were used to identify sources of contrast in OCT images of fetal membranes. A convolutional neural network was trained to automatically segment fetal membrane sub-layers with high accuracy (Dice coefficients >0.8). Intact amniochorion bilayer and separated amnion and chorion were individually loaded, and the amnion layer was identified as the load-bearing layer within intact fetal membranes for both labored and C-section samples, consistent with prior work. Additionally, the rupture pressure and thickness of the amniochorion bilayer from the near-placental region were greater than those of the near-cervical region for labored samples. This location-dependent change in fetal membrane thickness was not attributable to the load-bearing amnion layer. Finally, the initial phase of the loading curve indicates that amniochorion bilayer from the near-cervical region is strain-hardened compared to the near-placental region in labored samples. Overall, these studies fill a gap in our understanding of the structural and mechanical properties of human fetal membranes at high resolution under dynamic loading events.

biophysics↗

bioRxiv2023

The path to "femmes fatales": the evolution of toxin resistance in predatory fireflies.

Toxic cardiotonic steroids (CTS) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na+,K+-ATPase (NKA). While most fireflies produce these toxins internally, species of the genus Photuris acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between Photuris and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication. Our study demonstrates that both Photuris and their firefly prey have evolved highly-resistant NKAs. Using an evolutionary analysis of the specific target of CTS (ATP) in fireflies, and gene-editing in Drosophila, we find that the initial steps towards resistance were shared among Photuris and other firefly lineages. However, the Photuris lineage subsequently underwent multiple rounds of gene duplication and neofunctionalization, resulting in the development of ATP paralogs that are differentially expressed and exhibit increasing resistance to CTS. In contrast, other firefly species have maintained a single copy. Our results implicate gene duplication as a facilitator in the transition of Photuris to its distinct ecological role as predator of toxic firefly prey. One-Sentence SummaryGene duplication and neofunctionalization distinguish firefly predators from their toxic firefly prey.

evolutionary biology↗