Journal of Invertebrate Pathology

BACKGROUNDThe soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a pest of soybean in North America that can cause significant yield loss when outbreaks are not managed. Current management tactics primarily rely on inexpensive pyrethroids, but the sustainability of this option is threatened by insecticide-resistance in A. glycines populations across the Upper-Midwest United States. Field-evolved resistance is associated with mutations in the voltage-gated sodium channel subunit h1 (vgsc-h1) gene. RESULTSFour double-stranded RNA (dsRNA) molecules, each matching the sequence of a vgsc-h1 transcript variant ("Specific dsRNAs"), were topically applied to aphids with a genotype carrying the corresponding allele. The mortality of pyrethroid resistant aphids exposed to a Specific dsRNA increased in a dose-dependent manner when applied alone or with a constant concentration of lambda-cyhalothrin, plateauing at 1000 ng ul-1. Synergism was detected between two of four combinations of the Specific dsRNAs and lambda-cyhalothrin. These results were mirrored by the topical application of a single dsRNA with the consensus sequence of all vgsc-h1 variants ("Combined dsRNA"). Mortality was consistently higher in aphids treated with either Specific dsRNA or the Combined dsRNA, alone or with lambda-cyhalothrin, compared to insecticide alone. The number of nymphs produced per female treated with the Specific or Combined dsRNA alone decreased significantly compared to untreated controls. CONCLUSIONThis study demonstrates that the topical application of dsRNAs targeting vgsc-h1 increases the susceptibility and reduces the reproductive capacity of pyrethroid resistant soybean aphids, potentially providing a novel tool for the management of insecticide-resistant aphid populations.

Wolbachia is an incredibly widespread maternally transmitted bacterium in arthropods that can alter host physiology, nutrition, reproduction, and immunity. In some cases, multiple Wolbachia strains infect the same host and are stably transmitted alongside each other. This raises the question of how multiple intracellular symbionts interact with each another and with the host to ensure stable transmission. Here, we use fluorescence in situ hybridizations and confocal microscopy to investigate co-transmission in a naturally occurring co-infection of two Wolbachia strains in Drosophila simulans: wHa and wNo. We find significant differences in spatial occupancy and abundance between the co-transmitted strains across stages of oogenesis and embryogenesis. We show that wHa and wNo have biases for different niches during oogenesis, and their strain-specific abundance is driven by egg chamber development, mating status, and their interaction. After differential curing of the co-infection, we find that wNo is dependent on wHa for vertical transmission, but not vice versa. Additionally, while wHa localization patterns are unchanged by loss of co-infection, abundance of wHa in the ovaries increases when wNo is removed. Understanding how symbiont co-infections achieve stability has important implications for the ongoing use of Wolbachia as a tool for insect management programs, but also for our understanding of the ecology of intracellular communities more broadly.

The vine mealybug, Planococcus ficus, is a globally invasive pest of grapevine and a vector of leafroll viruses. Like other mealybugs, it reproduces through paternal genome elimination, a sex-determination system that operates without sex chromosomes and is associated with extreme sexual dimorphism. To characterize genome organization and sex-biased expression in this species, we generated a long-read reference genome spanning 369 Mb with 23,489 annotated genes and macrosynteny conserved with the citrus mealybug, Planococcus citri. Resequencing of four California field individuals yielded a first whole-genome estimate of nucleotide diversity and 132 microsatellite markers for population monitoring. Among 2,129 candidate secreted proteins, a conserved core is shared with P. citri, but each species carries a distinct set of lineage-specific effectors. Comparing adult male and female transcriptomes, we found sex-biased expression to be pervasive and skewed toward females: 41% of tested genes differed between the sexes, with female-biased genes both more numerous and showing larger fold changes. These female-biased genes were not randomly distributed but concentrated in discrete blocks of coordinately expressed, tandemly duplicated gene families, a pattern not previously described in a mealybug. Male- and female-biased secreted proteins also differed in origin, with male-biased proteins drawn from a conserved repertoire shared with P. citri and female-biased proteins spanning a more lineage-specific pool. Together, these results reveal a female-skewed, spatially clustered architecture of sex-biased expression in a mealybug that lacks sex chromosomes, and provide genomic resources for managing an invasive vineyard pest.

The earliest records of Trichinellosis might be found in bibles that recommend against pork consumption due to the spread of a disease that resembles what is now identified as Trichinellosis. Parasitic nematodes (round worms) of the genus Trichinella form a complex of at least 13 species with a broad geographic range. Herein, through data mining of transcriptomic data, and re-sequencing of the transcriptome of representative isolates, we demonstrate the presence of viruses within 10 recognized Trichinella species. We provide genome sequences of 4 viral species of negative sense RNA viruses that belong the Family Lispiviridae, Order Mononegavirales and of 8 novel viruses of double-stranded RNA viruses that belong to a novel sub-order within the order Ghabrivirales. The integration of viral genome fragments within encapsulated Trichinella genomes demonstrate that these parasite-virus associations are ancient. Overall, viruses show co-diversification with their parasitic hosts. Yet the phylogenetic position of viruses revealed past host jump from an ancestral encapsulated Trichinella species to the ancestral T. pseudospiralis, and challenges previous dogma on the phylogeny and biogeography of Trichinella species in North America.

While emerging diseases pose a global threat to amphibians, the dynamics of understudied vector-borne blood pathogens remain poorly understood. Pathogen occurrence is driven by a combination of environmental, ecological, and phylogenetic factors, yet how these drivers shape blood pathogen communities in tropical amphibians is largely unknown. In this study, we used molecular screening and phylogenetic linear models (PGLMMs) to evaluate how climate and ecomorphology influence the incidence of three blood pathogen groups (Trypanosomatidae, Hepatozoon, and Rickettsia) in wild anurans from a protected area in the Brazilian Atlantic Forest. Among 93 individuals sampled, over 93% were infected with at least one pathogen. Trypanosomatidae was the most common (76.3%), followed by Rickettsia (69.9%) and Hepatozoon (16.1%). Pathogen responses to temperature were contrasting: Hepatozoon occurrence increased in warmer periods, while Trypanosomatidae declined. Furthermore, rheophilic species showed a lower probability of Rickettsia infection, providing the first evidence that microhabitat use influences blood pathogen dynamics in amphibians. Our findings demonstrate that hemoparasites prevalence is driven by a multifaceted interplay of variables, highlighting that conservation strategies must account for these pathogen-specific responses to habitat use and environmental change, even within protected areas.

A parasitic mite of honey bee brood (Tropilaelaps mercedesae), is spreading through populations of Apis mellifera honey bees in new regions and poses a major threat to honey bee health. Despite its clear threat, the biology of this mite is poorly understood, with gaps on such fundamental issues as how fast its populations can grow. This leaves the beekeeping world underprepared to plan for its arrival and management. In this study, we documented the growth of T. mercedesae populations in untreated A. mellifera colonies in Thailand and South Korea, and did the same for another parasitic mite (Varroa destructor) when possible. We found that the population growth of T. mercedesae was variable but could reach high levels (daily r of 0.010, 0.036, and 0.057), while the population growth of V. destructor (r = 0.021) matched previous estimates. Our results indicate that T. mercedesae populations can grow rapidly but they do not always attain this potential. Based on our results, humidity should be studied as a potential driver of population growth. If future work can reveal key drivers of T. mercedesae population growth, this would help predict infestations and help design management strategies that exploit the pest's biological vulnerabilities.

Predators are often considered regulators of disease in prey populations, a concept central to the "healthy herd hypothesis". This hypothesis suggests that by preferentially removing infected individuals, predators can reduce parasite prevalence. However, predators may also act as disease vectors, facilitating the spread of parasites. We investigated whether stickleback fish (Gasterosteus aculeatus) can act as vectors for the transmission of the obligate bacterial parasite Pasteuria ramosa to its Daphnia host, a widespread freshwater zooplanktor. We fed infected D. magna to sticklebacks, and subsequently analysed faecal samples for the presence, viability, and infectivity of parasite transmission stages (= spores). We recovered approximately 60% of the consumed spores from fish faeces and these spores did not suffer from reduced infectivity to D. magna. Additionally, spores associated with sloppy feeding did not reduce infection rates. Thus, consumption of infected hosts by fish does not eliminate the parasite, but in contrary, may contribute to the spread and persistence of P. ramosa in natural populations, potentially influencing parasite dynamics in natural freshwater ecosystems.

Aedes albopictus is a major arboviral vector whose global expansion, driven by human activities and climate change, poses a growing public health concern for a number of neglected tropical diseases in both tropical and temperate regions. As a poikilotherm, its biology and population dynamics are strongly influenced by temperature, thereby shaping disease transmission. To thwart and control its geographic expansion, effective vector control strategies are increasingly critical. Densoviruses (DVs), such as AalDV2, are being explored as mosquito viral biocontrol agents due to their restricted host range and ability to disseminate through oviposition sites. However, the influence of environmental parameters on the interactions between Ae. albopictus and AalDV2 remains poorly understood. This makes their performance under realistic, fluctuating thermal regimes difficult to estimate. In this study, we investigated the combined effects of temperature and AalDV2 exposure on Ae. albopictus survival and development across its full life cycle. Mosquitoes were reared under fluctuating temperature regimes (26-28 {degrees}C and 32-34 {degrees}C, 12:12 day[ndash]night cycles) and exposed to AalDV2 or a control treatment. Chronic exposure to 32-34 {degrees}C significantly reduced overall survival, decreasing median lifespan by approximately 10 days (HR=2.21, p=0.0018), with a deleterious effect increasing over time. It extended aquatic lifespan and increased pupal mortality. It also reduced adult lifespan in both sexes with a stronger effect in females. AalDV2 exposure had no significant effect on overall survival, stage-specific mortality, or adult lifespan. However, a significant interaction between viral exposure and thermal stress was detected on aquatic lifespan: AalDV2-exposed females showed further extended larval and pupal development specifically under the 32-34 {degrees}C regime, without any effect on survival. These results indicate that the biocontrol potential of AalDV2 cannot be assessed independently of thermal context: while lethal effects were absent under both fluctuating regimes, the prolongation of aquatic development by the virus under thermal stress may have indirect consequences for mosquito population dynamics that warrant further investigation.

The potato leafhopper, Empoasca fabae (Harris, 1841), is a highly polyphagous, migratory insect pest of eastern North America that feeds on more than 200 herbaceous and woody plant species, causing substantial losses to forage and field crops. Despite its agricultural and ecological importance, no genome has been available for this species. Here, we present the first chromosome-level genome assembly of E. fabae, generated from Oxford Nanopore long reads, Illumina short reads, and Omni-C proximity-ligation data. The final assembly spans 908 Mb across 132 scaffolds, with 99.8% of the assembly captured in ten chromosome-length scaffolds (nine autosomes and an X chromosome) with a scaffold N50 of 96.2 Mb. The assembly is highly complete, recovering 92.4% of conserved hemipteran single-copy orthologs, and is composed of 47.6% repetitive sequence, dominated by long terminal repeat retrotransposons and unclassified elements. Read-depth comparison between male and female individuals supports assignment of a single sex-linked chromosome, consistent with an XO sex-determination system. BRAKER3 gene annotation predicted 31,406 protein-coding genes after retaining the longest isoform per locus. Comparative genome analysis against the two closest related Typhlocybinae species with genomes available, Matsumurasca onukii and Hebata decipiens, revealed extensive chromosome-scale collinearity, while defining a shared core gene repertoire. This reference genome provides a foundation for comparative and population genomic studies and for investigating genetic traits in this economically important crop pest species.

Long-distance movement in insects has crucial impacts on agriculture, human health, and biodiversity. Although it was long assumed that only large, specialist insects had the navigation capacity to support long-distance dispersal, recent studies have demonstrated that smaller insects, such as the tiny fruit fly Drosophila melanogaster, can maintain extended, straight paths while flying or walking. This raises the question of whether other Drosophila species possess the navigation capacity to support extended dispersal. Resolving this question is particularly important for Drosophila suzukii(spotted-wing drosophila), a potent pest species that causes enormous damage worldwide to ripe fruit and berries. Spotted-wing drosophila has been thought to lack a capacity for long-distance dispersal, as prior studies have estimated maximal daily dispersal distances of less than 90 m. We developed a system to continuously track the flight trajectories of magnetically tethered D. suzukii relative to a discrete, overhead LED that mimicked the sun. We found that flies maintained remarkably straight flight headings that varied unpredictably across individuals. Male and female D. suzukii exhibited a similar navigation capacity; both sexes responded to rotation of a discrete sun stimulus with compensatory turns to maintain a stable relative heading. Our results suggest that D. suzukiihas an underappreciated capacity for rapid, radial dispersal, which could exceed 250 m in 15 min. This capacity may contribute to the pest species' invasiveness and its reliable, annual re-establishment in seasonally intolerable climates. Our findings highlight the importance of developing area-wide, regional strategies to manage the impacts of D. suzukii.

High Pathogenicity Avian Influenza (HPAI) H5N1 clade 2.3.4.4b has spread beyond birds to affect seals across the Southern Ocean and sub-Antarctic region, with southern elephant seals (Mirounga leonina) particularly devastated. The virus, likely introduced via spillover from infected migratory birds, has killed tens of thousands of adult seals and pups throughout most of their range, though Macquarie Island remains unaffected so far. We used twenty years of elephant seal movement data from the southern Indian and Pacific oceans to assess whether seal-to-seal transmission could spread HPAI H5N1 between breeding colonies, despite the vast distances separating them (Marion Island, Iles Crozet, Iles Kerguelen, and Macquarie Island). There was substantial overlap in seals' at-sea distributions during their winter post-moult trips, when seals travel for weeks at average speeds of 3.5 km/h. Two transmission pathways were examined: (1) terrestrial "stepping stone" routes, where infected seals could pass the virus between colonies during short intervals to remain infectious were feasible from Marion Island to Kerguelen but not from Kerguelen to Macquarie Island; and (2) at-sea encounters between seals, which occurred frequently enough to enable transmission. The findings suggest that once established at Macquarie Island, the virus could potentially spread further to New Zealand's sub-Antarctic islands and mainland New Zealand. While seal-to-seal transmission appears possible, we conclude this is unlikely. Nonetheless, understanding at-sea contact rates enhances knowledge of H5N1 epidemiology and demonstrates the value of combining long-term population monitoring with movement data to understand wildlife disease dynamics.

Lone star virus (LSV) is a bandavirus first isolated from Amblyomma americanum ticks in the United States (U.S.) and is phylogenetically related to severe fever with thrombocytopenia syndrome virus (SFTSV), Heartland virus (HRTV), and Bhanja virus, each of which has been associated with severe human disease. In contrast to these better-characterized bandaviruses, LSV remains poorly studied, and its pathogenic potential is not well defined. Recent detection of LSV RNA in cerebrospinal fluid from an immunocompromised patient in Idaho, U.S., with fatal meningoencephalitis further highlights the need for experimental systems to investigate LSV biology. Here, we rescued recombinant (r) LSV from cloned cDNA and used it to characterize LSV. rLSV replicated similarly to the parental isolate in mammalian cells and caused rapid, systemic, and lethal disease in IFNAR-/- mice, with widespread detection of viral (v) RNA across multiple tissues, hepatic and splenic pathology, and induction of inflammatory cytokines. In contrast, C57BL/6J mice controlled infection and exhibited no clinical disease. To place LSV within a broader comparative framework, we generated rSFTSV from cloned cDNA and compared rLSV, rSFTSV, and HRTV in cell culture and IFNAR-/- mice. Our studies revealed distinct disease kinetics among these related tick-borne bandaviruses and showed that HRTV-induced immunity protected against homologous HRTV rechallenge and heterologous rSFTSV challenge, but not rLSV challenge. Together, these findings establish reverse-genetics platforms and small-animal models for comparative bandavirus studies, define key features of LSV pathogenesis, and place this neglected virus within a framework of related bandaviruses that differ in virulence and immunological overlap.

Accessory genes are thought to contribute to fungal adaptation and pathogenicity by modulating host immunity, while core genes play crucial roles in maintaining fundamental biological processes. Rust fungi (order Pucciniales) are obligate biotrophic plant-pathogens and infect economically relevant crops. Here, we characterize core and accessory gene repertoires across rust fungi, with a particular focus on Phakopsora pachyrhizi, the causal agent of Asian soybean rust. Across Pucciniales genomes, accessory genes represented the largest fraction of gene content (~44.6% on average), whereas core genes accounted for a smaller proportion (~18-35%). Notably, variations in accessory gene content among rust fungi are perhaps attributed to lineage-specific gene expansions and losses. Core gene content was positively correlated with total gene number across Pucciniales genomes, suggesting retention after gene duplication events, consistent with their essential biological functions. Among P. pachyrhizi genes expressed during soybean infection, core effectors were associated with cysteine-rich proteins, pectin-degrading enzymes, and SPFH/Band 7 family, while accessory effectors included phosphatidylethanolamine-binding proteins, trehalose phosphatases, and CFEM domain-containing proteins. The in-plant induced core and accessory genes in P. pachyrhizi also comprised multiple families of CAZymes (GH5/GH7 cellulases, CE5 cutinases, CE8 pectinesterases, CE4/GH18 chitin-modifying enzymes); proteases (aspartyl proteases, serine carboxypeptidases, alpha/beta hydrolases); transporters (amino acid permeases, ferric reductase-like transmembrane proteins, and OPT oligopeptide transporter), and transcription factors (bZIP, GATA zinc finger, STE-like, and homeobox KN). Our study highlights that core and accessory gene families have shaped P. pachyrhizi-soybean interactions, identifying promising targets for functional studies aimed at elucidating host-adaptation mechanisms in rust fungi.

The global invasion of the Asian tiger mosquito Aedes albopictus has led to an increase in arboviral disease, including within Mesoamerica. Understanding vector invasion routes is important for public health because it directs biosecurity and identifies sources of adaptive allele spread. Panama is an important hub of global trade with opportunities for Aedes introduction through both maritime and overland routes but dispersal into the Isthmus has not yet been investigated. We therefore sought to investigate the population structure and invasion history of Ae. albopictus into Panama, targeting both its mitogenome and associated Wolbachia. Historical demographic analysis with Bayesian phylogeographic diffusion models and estimates of divergence revealed that Panamanian Ae. albopictus and its associated Wolbachia have a convergent evolutionary history resulting from multiple introductions. Both could be traced to Asian-derived lineages introduced via the Americas, with invasion primarily through the maritime trade of the Panama Canal rather than overland dispersal from neighboring Costa Rica. An investigation of the relative density of Wolbachia in Panama revealed that both the strains wAlbB and wAlbA were at a notably lower density compared to other worldwide locations. This finding has implications for arbovirus transmission and raises important questions about how Wolbachia density is impacted by the environment and impacts on population control. Overall, the Panama Canal is a key route for vector introductions into Mesoamerica.

O-Acetylation is the most abundant xylan decoration in eudicot plants and plays a critical role in determining xylan conformation and its interactions with cellulose and lignin, thereby contributing to secondary cell wall (SCW) integrity. In Arabidopsis, loss of the xylan O-acetyltransferase TBL29/ESK1 causes collapsed xylem and growth defects that can be suppressed by mutations in strigolactone (SL) biosynthesis genes such as MAX3. However, the molecular basis of this suppression remains unknown. Hypoacetylated xylan in tbl29 has a higher frequency of methyl glucuronic acid (MeGlcA) substituents, while the ratio of GlcA/MeGlcA is recovered in tbl29 max3. Furthermore, gene expression analyses reveal that the three xylan glucuronoxylan methyltransferases (GXM1/2/3) involved in xylan MeGlcA modification are upregulated in tbl29 SCWs but downregulated in tbl29 max3. Genetic analysis shows that the transcription factor MYC2 is required for max3-mediated suppression: the loss of MYC2 in tbl29 max3 prevents growth recovery and reverts GXM genes expression and xylan MeGlcA substitution levels. We propose a model where SL deficiency enhances MYC2 transcription, which in turn represses GXMs, thereby fine-tuning xylan methylation and re-establishing the MeGlcA/GlcA substitution balance under conditions of reduced O-acetylation. Our findings identify a MYC2-dependent regulatory module linking SL signalling to xylan methylation and reveal a genetically encoded compensatory mechanism that mitigates the consequences of defective xylan O-acetylation. More broadly, this work demonstrates that plants can preserve SCW function through adaptive remodelling of polysaccharide substitution patterns, highlighting an unexpected plasticity in SCW biosynthesis. Significance StatementSecondary cell wall integrity depends on the coordinated modification of xylan. We show that defects caused by reduced xylan O-acetylation can be alleviated through a strigolactone- and MYC2-dependent pathway that alters xylan methylglucuronidation. Rather than restoring the original wall composition, this mechanism appears to compensate for the loss of O-acetyl groups by remodelling polysaccharide substitution patterns to maintain cell wall function, revealing a new layer of plasticity in secondary wall biosynthesis.

Fission is essential for proper mitochondrial function and for cellular homeostasis. Dysfunction in mitochondrial fission is associated with several neurological disorders, including the rare and lethal encephalopathy EMPF1, which is caused by de novo heterozygous DNM1L variants. DNM1L encodes the mitochondrial fission mechanoenzyme DRP1, which can intrinsically self-assemble and induce membrane scission. Wild-type DRP1 puncta that appear throughout the cytoplasm are thought to be pre-scission complexes of well-ordered oligomeric assemblies. Immunofluorescence imaging of patient-derived EMPF1 fibroblasts carrying assembly-deficient DNM1L variants reveals elongated mitochondrial networks consistent with impaired fission. Despite this loss-of-function phenotype, these cells retain essentially wild-type numbers of DRP1 puncta. We confirmed the previously reported inability of purified pathogenic DRP1 variants p.Gly363Asp and p.Gly401Ser to assemble under conditions in which WT DRP1 forms helical polymers. Under macromolecular crowding conditions, however, both wild-type and mutant DRP1 access condensed states whose formation depends on protein concentration and solution conditions. Acute treatment of EMPF1 fibroblasts with 1,6-hexanediol preferentially alters DRP1 puncta fluorescence intensity and distribution in mutant cells relative to wild type, indicating genotype-dependent differences in puncta material properties. Together, these findings support a model in which DRP1 puncta occupy a continuum of condensed states, only a subset of which mature into fission-competent assemblies, revealing biomolecular condensation as a previously unrecognized layer of DRP1 regulation. Biasing DRP1 along this continuum may provide a mechanistic basis for impaired fission in EMPF1 and suggest opportunities to restore productive assembly in select pathogenic contexts.

Extrahepatic delivery of lipid nanoparticles (LNPs) to non-phagocytic cells is a major challenge, with the leading strategy involving surface functionalization with target-specific monoclonal antibody (mAb) ligands. We investigate the stability of mAb-conjugated LNPs using two anchoring systems: the commonly used DSPE-PEG2kDa-maleimide and a block copolymer, PCL5kDa-b-PEG2kDa -maleimide, with the hypothesis that conjugation to a 150,000 Da antibody could overwhelm the relatively small ~600 Da aliphatic anchor on the PEG-lipid in vivo. Shedding of the mAB would compromise targeting. Conjugation integrity following IV injection was assessed by tagging LNPs and mAbs with metal ion tracers that could be quantified by ICP-MS. Results show that DSPE-PEG-mAb rapidly (within 1h) dissociates from LNPs in blood, leading to accelerated LNP clearance. In contrast, mAbs conjugated using PCL-b-PEG remained stably associated with the LNP over the 24h circulation and clearance of the construct. Results are connected to a thermodynamic model that reproduces experimental findings for PEG-anchor(-mAb) shedding in vitro and in vivo. This study identifies anchoring strength as a critical, unconsidered parameter for in vivo performance when conjugating mAbs to LNPs for extrahepatic delivery.

Blockade by sedimentary particles, such as mineral crystals, is a continuous risk the kidney tubule faces. To prevent that, kidney resident macrophages form transepithelial protrusions and remove intratubular sedimentary particles, a behavior particularly prevailing in the medulla over the cortex. However, the molecular mechanisms underlying this characteristic behavior of medulla macrophages are incompletely understood. In this study, we identified that the medulla had higher mechanical stiffness than the cortex in steady state, which was further elevated when kidney stone formed. Increased tissue rigidity was sensed by medulla macrophages via mechanoreceptor Piezo1, which promoted macrophage protrusion formation and their ability to clean the tubules. Loss of Piezo1 expression in kidney macrophages predisposed mice to intratubular accumulation of mineral crystal in steady state and accelerated kidney stone formation during oxalate intake challenge. Signaling via Piezo1 mobilized molecules involved in cell adhesion and protrusion assembly, including Talin2 and focal adhesion kinase (FAK). Finally, we developed a first-of-its-kind cell-based therapy for the treatment of experimental nephrolithiasis by exploiting macrophage Piezo1 activity, and this strategy shows great promise for future translational research.

Single-nucleus transcriptomic atlases offer an unprecedented opportunity to connect cellular molecular states with Alzheimer's disease (AD) neuropathology, but whether these profiles encode reproducible, predictive information about pathological burden remains unclear. We present the SEA-AD DREAM Challenge, an open, international, model-to-data competition built on the Seattle Alzheimer's Disease Brain Cell Atlas to predict Alzheimer's disease neuropathological severity from single-nucleus RNA-sequencing data. Participants developed containerized models to predict categorical neuropathological staging, including overall Alzheimer's disease neuropathologic change, Braak stage, Thal phase, and CERAD score, as well as quantitative amyloid-{beta} and phospho-tau burden measured by 6E10 and AT8 immunohistochemistry. Across 17 eligible teams from 15 countries, the crowdsourcing framework enabled systematic comparison of diverse computational approaches and surfaced a broad landscape of modeling strategies and candidate predictive features. Top-performing methods achieved near-perfect prediction of categorical staging, with the best submission reaching a quadratic weighted kappa of 1.0 for the Overall AD Neuropathological Change score (ADNC), and competitive prediction of quantitative pathological burden in held-out data, with a best concordance correlation coefficient of 0.48. Post hoc perturbation analyses revealed that top categorical-stage predictions relied heavily on donor-level metadata-driven signals rather than transcriptomic features, whereas quantitative pathology prediction was more robust and supported by transcriptomic and cell-type-associated features with potential biological relevance to AD progression. The challenge also introduced the first AI Agent Track in a DREAM Challenge, providing an early benchmark for autonomous and human-guided agentic model development in single-cell neuroscience. This work demonstrates that single-nucleus transcriptomes encode substantial information about Alzheimer's disease pathology, establishes a reproducible benchmark for molecular neuropathology prediction, and highlights critical principles for designing privacy-preserving, leakage-aware community challenges using deeply phenotyped human brain data.

Temporal niche partitioning is a strategy for reducing interspecies competition and strengthening reproductive isolation. It relies on animals confining their daily activity to distinct diurnal, crepuscular, or nocturnal windows. However, a hardwired temporal niche is only advantageous under stable, predictable ecological regimes; surviving dynamic environments demands behavioral flexibility. Yet, it remains unclear how animals override rigid biological constraints to rapidly exploit transiently available fitness-critical time windows. To address this, we leveraged the twilight-active, species-rich Drosophila genus and monitored their daily activity under naturalistic conditions. Here, we show that intense sociosexual interactions rapidly drive a species-specific reformatting of their canonical crepuscular niche. The dominant sensory modality used for sexual communication predicts niche shift direction: reliance on chemosensation for courtship redirects behavioral activity into the night, while visual reliance shifts it into the day. This temporal plasticity bypasses the circadian clock, instead operating via a conserved dopaminergic pathway. Dopamine operates a dual-output brain circuit that simultaneously inhibits sleep and sustains sexual motivation. Our results reveal how mating imperatives decouple behavioral timing from circadian command, enabling conditional colonization of otherwise restricted temporal windows. Ultimately, by driving the divergence of previously overlapping niches, sociosexually induced temporal plasticity provides a powerful mechanism for sympatric coexistence in crowded environments.