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bioRxiv2026

Elucidating the functional domain architecture of ArCS1, a biomineralizing myosin chitin synthase: I. The role of lipids

In molluscs, chitin synthases are essential for biologically controlled biomineralization, with some variants possessing a myosin motor domain that may link polymer synthesis to the cytoskeleton. Experimentally, we established a reliable workflow for expressing ArCS1_E22TM in Dictyostelium discoideum and developed effective purification methods to reconstitute ArCS1_E22TM in nanodiscs using MSPs and specific lipid composition. MSP1D1deltaH5 proved optimal for nanodisc formation, yielding homogeneous, monodisperse discs (~8.2 nm). Lipids were refined to POPC:POPE:POPG (3:1:1) with 20% cholesterol, improving nanodisc quality and uniformity as observed by negative-stain EM. The full-length ArCS1 and its subdomains were modeled using AlphaFold3; the myosin motor, glycosyltransferase, and transmembrane regions are well-defined internally but loosely constrained relative to one another, suggesting flexible linking and conformational coupling. Modelling with Mg2+ and oleic acid as ligands and comparative analyses with bacterial cellulose synthase and yeast chitin synthase 1 provided insights into substrate binding and a potential mechanism for chitin polymerization and translocation. This research establishes a standard procedure for comprehensive structural analyses of recombinant molluscan chitin synthase in near-native or biomimetic membranes. This sets the stage for high-resolution cryo-electron microscopy to determine the first experimentally resolved structure of a molluscan chitin synthase and to provide insight into the enzyme's architecture and the regulatory mechanisms of biomineralization.

molecular biology↗

bioRxiv2026

DIFFERENTIAL PHOTOSYNTHETIC RESPONSES TO GLUFOSINATE AMMONIUM IN TWO GRASS WEEDS: Lolium multiflorum AND Echinochloa crus-galli.

Background: Weed control is one of the main challenges in agriculture today, particularly due to the increasing occurrence of herbicide-resistant populations. Among the most problematic species are Lolium multiflorum (L.) and Echinochloa crus-galli (L.) Beauv., for which glyphosate-resistant populations have been reported. In this context, glufosinate ammonium has emerged as an alternative for their control; however, its efficacy may vary depending on species and photosynthetic metabolism. Objective: The objective of this study was to evaluate the differential sensitivity of ryegrass (C3) and barnyardgrass (C4) to ammonium glufosinate by analyzing physiological responses associated with leaf senescence and photosystem II activity. Methods: Visual injury, chlorophyll fluorescence, and ammonium accumulation were assessed. Results: Results revealed a differential response between species. Barnyardgrass exhibited earlier symptom onset and a greater reduction in the quantum yield of photosystem II ({Phi}PSII), whereas ryegrass showed a slower senescence process. These differences indicate a higher sensitivity of barnyardgrass to glufosinate ammonium, possibly associated with its C4 photosynthetic metabolism. Conclusions: It is concluded that the effectiveness of glufosinate ammonium depends on the type of photosynthetic metabolism and on the ability of each species to cope with herbicide-induced oxidative stress. This information contributes to optimizing glufosinate ammonium use and to the development of management strategies aimed at delaying the evolution of herbicide resistance.

plant biology↗

bioRxiv2026

Dynamic microtubules drive yolk-cytoplasm segregation in the syncytial Drosophila embryo

Yolk-cytoplasm segregation is among the earliest spatial organization events in the developing embryo of many oviparous animals. The segregation process is intimately linked to early embryonic cleavage and pattern formation, and exhibits a wide range of spatial and temporal diversity. However, the underlying cytoskeletal mechanism remains largely unknown, except for a small number of species. Using quantitative live imaging, we investigated yolk segregation in the Drosophila embryo during the syncytial nuclear cycles 11-14. We find that the yolk vesicles move progressively inward in spatial and temporal coordination with the inward expanding microtubule networks that are nucleated from centrosomes positioned at the cortex, whereas cortical actin meshwork remains spatially restricted. Using the gnu RNAi embryo to decouple nuclear migration and division from cytoskeletal dynamics, we establish causality with targeted pharmacological disruption and find that microtubule dynamics is required for yolk segregation, while depolymerization of actin has no discernible effect. In support of a mechanism of growth-propelled passive displacement, microtubule plus end comets come in apparent contact with yolk vesicles, and injected, inert microbeads are displaced towards the embryo center presumably by the same pushing force. These findings identify microtubule polymerization as a predominant driver of yolk-cytoplasm segregation in Drosophila and suggest that diverse cytoskeletal mechanisms evolved to accomplish this crucial reorganization process

developmental biology↗

bioRxiv2026

Cross-Kingdom Control: Yeast Prion Protein Modulates Host Physiology in Drosophila

Prions, once mainly studied for their pathogenic roles, are now gaining recognition as adaptive elements in microbial physiology. Over one-third of wild yeast isolates harbor prion proteins, yet their impact on host-microbe interactions remains poorly characterized. Given the ecological dominance of yeasts in the Drosophila mycobiome, we leveraged the Drosophila melanogaster-Saccharomyces cerevisiae system to investigate how the mycobiome-derived prion, [MRPL10+], modulates host physiology. We show that flies exposed to [MRPL10+] yeast exhibit significantly enhanced cold tolerance and increased locomotor activity. This effect persists with heat-killed yeast and diluted culture, suggesting a stable, potent bioactive factor. Using the genetically diverse Drosophila Global Diversity Lines (GDL), we identified natural variation in responsiveness to [MRPL10+] yeast. Genome-wide association and functional RNAi screening revealed a gut-brain signaling axis involving genes critical for digestion, intercellular communication, transcription regulation, and neural transmission. Notably, serotonin and octopamine pathways were essential for [MRPL10+]-induced changes in cold tolerance and locomotion, implicating neuromodulatory circuits in prion-mediated microbial signaling. Our findings establish a mechanistic link between a fungal prion and host metabolic and neural adaptation. This work provides the first genetic dissection of a prion-mediated host-microbe interaction, laying the groundwork for investigating beneficial prions in complex microbial communities and highlighting a new dimension of the mycobiomes influence on animal physiology.

evolutionary biology↗

bioRxiv2026

Evolutionary replay of duplicate-gene retention across independent whole-genome duplications

Whole-genome duplications repeatedly expose ancestral gene lineages to the same broad evolutionary outcome-retention or loss of duplicated copies-but it remains unclear whether this history replays similarly across evolutionary scales. We placed duplicate retention in shared hierarchical orthologous-group coordinates and compared percentile ranks defined within each event-wide mapped universe. Three independent angiosperm whole-genome duplications showed reproducible replay (global rank effect T-replay = 0.210, bootstrap 95% confidence interval 0.172-0.248; permutation P = 1/100,001). A plant reference-panel score specified before target outcomes were examined predicted retention after the Apple/Pear duplication ({rho} = 0.169, n = 373). Deep transfer was heterogeneous: the teleost-genome-duplication estimate was positive but unresolved ({rho} = 0.107, n = 151, 95% confidence interval -0.050 to 0.260), whereas transfer to the ancient budding-yeast whole-genome duplication (yeast WGD) was supported ({rho} = 0.280, n = 186). Independently reconstructed animal outcomes also replayed between teleost and Stylommatophora duplications (r = 0.226, n = 146, P = 0.00326), although the effect remained below a prespecified strong-effect threshold. A strict plant-animal comparison was limited to 25 deeply one-to-one lineages and was unresolved (r = 0.033, 95% confidence interval -0.303 to 0.340). Thus, ancestral gene-lineage identity contributes reproducibly to duplicate retention after independent whole-genome duplications, but replay is structured by evolutionary lineage and modified by event-specific history rather than governed by one universal gene-fate ranking.

evolutionary biology↗

bioRxiv2026

Unbiased and scalable reduction of diverse bacterial genomes

The genome is a complex, integrated system where the functions and regulatory interactions of its many components remain poorly understood. Genome minimization aims to reduce genomic complexity by removing non-essential elements to reveal the fundamental building blocks of cellular life. However, current minimization strategies are often slow and species-specific due to a reliance on prior information, and limited to producing single, isolated strains, which obscures the diverse ways a genome can adapt to large-scale DNA removal. Here we show the development and application of Stochastic Lineage-based Iterative Minimization (SLIM) a modular, high-throughput platform for unbiased genome reduction across phylogenetically diverse bacteria. We apply SLIM to generate a library of genome-reduced Escherichia coli lineages. We then interrogate the lineages, identifying both universal and lineage-specific transcriptional and translational reprogramming in response to deletions. We demonstrate that these expression dynamics drive environment-dependent fitness, allowing us to pinpoint a single gene deletion in one genome-reduced lineage as the driver of a measurable environmental growth defect. Beyond E. coli, we successfully deploy SLIM in phylogenetically distinct bacterial taxa to rapidly reduce the genomes of Shigella flexneri and Pseudomonas putida, distinct genus and order respectively from E. coli, without species-specific optimization. Our results establish a scalable, generalizable framework for navigating the vast landscape of minimized genomes, providing a powerful new tool for functional discovery and the rational design of synthetic genomic chassis.

synthetic biology↗

bioRxiv2026

Structural mechanism of nuclear membrane sealing by LEM2-ESCRT-III

In open mitosis, re-establishing nucleocytoplasmic compartmentalization requires the LEM2-ESCRT machinery to coordinate spindle clearance with sealing of the remaining nuclear envelope pores. The structural basis of this topologically unique and fundamental membrane-remodeling process is poorly understood. Here, we combine biochemical reconstitution, cryo-electron tomography, subtomogram averaging and large-scale molecular dynamics simulations to define the structural mechanism of nuclear membrane sealing. We structurally resolve that LEM2s winged-helix domain (WH) co-polymerizes with the ESCRT-II/III protein CHMP7 to form a membrane-bound scaffold whose geometry is progressively remodeled by downstream ESCRT-III proteins as it transitions from the flat membrane surrounding the pore towards the negatively curved membrane neck. In parallel, LEM2 positions its intrinsically disordered low-complexity domain within the pore, where condensation around spindle microtubules mechanically couples the membrane-ESCRT-LEM2 scaffold to the spindle and narrows the remaining diffusion path, restoring compartmentalization before membrane closure is complete. Remarkably, the LEM2-WH domain alone forms tightly constricted membrane tubes, coating the negatively curved inner surface, revealing an intrinsic membrane-remodeling activity of the receptor itself. Together, our work establishes a structural framework for how receptor-ESCRT co-polymerization, low complexity domain-mediated sealing and receptor-driven membrane remodeling guide nuclear-envelope pores from spindle-containing openings to terminal constriction and fusion.

molecular biology↗

bioRxiv2026

miR-34/449 miRNAs regulate choroid plexus ciliogenesis to control cerebrospinal fluid production

A developmental increase in cerebrospinal fluid (CSF) production during development is essential for neuronal growth and ventricular expansion. A key regulator of CSF production is the specialized sensory multicilia of the choroid plexus (ChP), which mediate non-canonical Sonic hedgehog (Shh) signaling to suppress water channel and ion transporter expression, thereby limiting CSF production. ChP multicilia progressively shortens during development, attenuating Shh signaling and promoting CSF production. Here, we identify miR-34/449 miRNAs as essential regulators of ChP multiciliogenesis. Whereas mutations in canonical ciliogenesis genes elevate CSF production and contribute to hydrocephaly, deletion of miR-34/449 reduces CSF volume and causes microcephaly. Loss of miR-34/449 miRNAs causes excessive basal body amplification, defective basal body docking, and failure of developmental multiciliary shortening. Consequently, miR-34/449-deficient ChP cilia remain abnormally long and fail to attenuate Shh signaling, resulting in sustained repression of water channel and ion transporter expression and reduced CSF production. Mechanistically, miR-34/449 miRNAs directly target Gmnc, a master transcriptional regulator of multiciliogenesis, to restrain basal body amplification and promote basal body docking. Together, our findings identify miR-34/449 miRNAs as critical regulators of ChP multiciliogenesis and establish the developmental remodeling of ChP multicilia as a mechanism to couple Shh signaling dynamics to developmental control of CSF production.

developmental biology↗

bioRxiv2026

DNA Damage and Repair Mechanisms in Duckweed (Spirodela polyrhiza) Under Ultraviolet-B (UV-B) Light Stress

Exposure to Ultraviolet-B (UV-B) light can adversely affect plant growth and cellular integrity by inducing oxidative stress and DNA damage. In this study, we investigated UV-B-induced DNA damage and repair responses in the aquatic monocotyledonous plant species Spirodela polyrhiza (duckweed). We exposed 13-day-old duckweed plantlets to broadband UV-B light for 1-10 min, followed by recovery periods of up to 24 h under normal growth conditions. We observed progressive chlorosis, wilting, and diminished plant vigor with longer durations of UV-B light exposure. Agarose gel electrophoresis demonstrated compromised genomic DNA integrity immediately after UV-B light treatment, with partial restoration of DNA quality during recovery. Immuno-slot blot assays established the accumulation of two major UV light-induced photoproducts, cyclobutane pyrimidine dimers (CPDs) and 6-4 pyrimidine-pyrimidone photoproducts [(6-4)PPs], in a dose-dependent manner following UV-B light exposure. Notably, the abundance of these DNA lesions declined substantially after recovery, indicating activation of endogenous DNA repair mechanisms. Staining with 3,3-diaminobenzidine revealed elevated accumulation of hydrogen peroxide immediately following UV-B exposure, suggesting enhanced oxidative stress. Collectively, these findings demonstrate that S. polyrhiza possesses efficient mechanisms for sensing, repairing, and mitigating DNA damage induced by oxidative stress resulting from UV-B light exposure. This study highlights the potential of duckweed as an effective model system for investigating DNA damage and repair pathways under UV-B light stress in plants.

plant biology↗

bioRxiv2026

A single dsRNA spray silences VAMT and shifts habanero pepper fruit metabolism towards capsinoids

Capsaicinoids are synthesized in the placenta of Capsicum fruit, where vanillylamine aminotransferase (VAMT) catalyzes the formation of vanillylamine, the precursor of the pathway. The modulation of pungency has relied on genetic breeding and transgenic approaches, and this pathway has not been addressed by spray-induced gene silencing. The aim of this study was to evaluate whether a single non-invasive spray of double-stranded RNA (dsRNA) targeting VAMT allows the gene to be silenced and capsaicinoid accumulation to be modified in Capsicum chinense fruit. The molecule was designed in silico and applied at 10 days post-anthesis. Pedicel injection reduced the VAMT transcript in a dose-dependent manner, with three levels of inhibition distinguishable from one another. Spraying with surfactant reduced it by 86.2 %, a magnitude statistically indistinguishable from the 90.6 % obtained by injection, and also reduced the Pun1 transcript, a co-regulation previously described only as a difference between cultivars. Analysis by gas chromatography coupled to mass spectrometry showed reductions of 84.4 % in capsaicin and 68.5 % in dihydrocapsaicin, the loss of nonivamide and one further vanillylamine-derived compound, and the detection of capsiate and a second capsinoid, absent in control fruits. The siRNA was detected in non-treated tissues, and a single topical application is therefore sufficient to silence an endogenous biosynthetic gene and shift the metabolic profile of the fruit without genetic modification.

plant biology↗

bioRxiv2026

A Hymenoptera-restricted gene mediating ant castes co-opts deeply conserved machinery to control organ size

Lineage-specific genes are widespread and have been implicated as phenotypic innovation inducers, but how they acquire complex developmental functions remains poorly understood. Ant queens and workers develop dramatically different organ sizes from identical genomes under juvenile hormone (JH) control, yet the molecular effectors translating JH signalling into caste-specific organ growth remain unknown. Here we identify torch, a Hymenoptera-restricted gene, as the most consistently gyne-biased and JH-responsive gene across 68 ant species. Knockdown of torch in virgin queens of Monomorium pharaonis produces a worker-like, multi-organ growth-restricted phenotype. Mechanistically, torch harbours an E-box-like motif activated by the JH receptor Gce-Tai and acts as a GA-repeat-binding transcription factor that regulates Hippo signalling, the deeply conserved organ-size control pathway in animals. Expressing torch heterologously in mice and a growth-restricted Drosophila background shows that the gene retained its general growth-promoting activity across more than 700 million years of animal evolution in lineages that lack the gene, establishing that its function is mediated through conserved rather than ant-specific machinery. A lineage-specific gene can therefore acquire complex morphogenetic function by co-opting ancient organ-size circuitry, providing a general route by which novel genes can drive phenotypic innovation.

evolutionary biology↗

bioRxiv2026

A century of soybean breeding increased photosynthetic capacity but not NPQ relaxation

Accelerating photoprotective regulation to improve carbon assimilation is a promising strategy to increase crop productivity. Although rapid non-photochemical quenching (NPQ) relaxation has been validated as a target through metabolic engineering, it remains unclear whether conventional breeding has improved this trait. Here, we investigated whether more than a century of soybean breeding enhanced NPQ relaxation alongside light-saturated carbon assimilation and seed traits. We evaluated a historical panel of 24 soybean genotypes across vegetative and reproductive developmental stages by integrating NPQ relaxation, gas exchange parameters, xanthophyll-cycle pigment profiles, expression of key photoprotective genes (VDE, PsbS, and ZEP), seed number and seed weight. NPQ relaxation parameters were not consistently associated with genotype release year, seed number, or seed weight at either developmental stage. The only exception was the amplitude of the rapidly relaxing NPQ component (AqE), which was negatively correlated with all three variables during the reproductive stage. In contrast, genotype release year was positively associated with maximum net CO2 assimilation rate (Amax), maximum carboxylation rate of Rubisco (Vcmax), maximum electron transport rate (Jmax), seed number, and seed weight, while Amax and Vcmax were positively correlated with seed number and seed weight. These findings indicate that the greater photosynthetic capacity of modern genotypes was not accompanied by faster photoprotective response. Thus, photoprotective regulation has not kept pace with gains in photosynthetic capacity under field conditions. We conclude that rapid NPQ relaxation remains an important target for synchronizing photoprotection with the high photosynthetic capacity of modern soybean lines.

plant biology↗

bioRxiv2026

Impact of Water Deficit on Growth, Biochemical, and Physiological Traits in Eggplant MAGIC Lines

Climate change exacerbates agricultural water scarcity, necessitating the development of drought-tolerant crop varieties. This study evaluates 12 eggplant lines from a MAGIC (Multi-parent Advanced Generation Intercross) population, previously selected for contrasting responses to water deficit during the vegetative stage. To validate tolerance under adult production conditions, plants underwent five irrigation-withholding cycles over a 170-day greenhouse growing period. Yield components, the Stress Tolerance Index (STI), and physiological parameters (water status and stomatal conductance) were evaluated. Additionally, photosynthetic pigments, oxidative stress markers, antioxidant compounds, and osmolytes were quantified to characterize the biochemical basis of tolerance alongside final biomass production. The results showed that four of the five lines that were previously classified as tolerant in the vegetative stage remained among the most tolerant at the reproductive stage. Specifically, lines L13, L78 and L179 were the most productive under water-limited conditions. While L13 and L179 exhibited stable tolerance throughout all developmental stages, L78 displayed stage-specific tolerance, manifested only during the reproductive growth phase. These findings emphasise the importance of integrating early-stage screening with adult-stage validation in order to capture the full spectrum of genetic drought tolerance. The most productive lines were characterised by moderate aboveground biomass, high leaf hydration and maintained stomatal conductance. However, the strategies employed differed: while L179 exhibited high photosynthetic pigment content, L13 was characterised by high total sugar accumulation. Overall, these results provide a multi-trait roadmap and identify elite MAGIC parental lines for breeding climate-resilient eggplant cultivars.

plant biology↗

bioRxiv2026

Systems genetics identifies ETS1 as a stress-dependent regulator of adipocyte insulin action and heme-iron homeostasis

White adipose tissue plays a central role in systemic energy homeostasis by buffering nutrient excess through insulin-stimulated glucose uptake and triglyceride storage. Despite its importance, the genetic and molecular mechanisms governing adipose tissue insulin action remain poorly defined because tissue-specific insulin responsiveness has been difficult to quantify at the scale required for genetic discovery. Here, we developed the first scalable platform for high-throughput genetic mapping of tissue-specific insulin action in adipose tissue, enabling systems genetic analysis across 559 genetically diverse Diversity Outbred Australia (DOz) mice. Genetic analysis accounting for adiposity identified 39 loci associated with adipose tissue insulin action, demonstrating that adipose insulin responsiveness is a genetically encoded trait that captures a dimension of metabolic health beyond adiposity. Among these, a strong diet-dependent locus on chromosome 9 encompassed the transcription factor Ets1. Functional studies demonstrated that Ets1 silencing selectively restored insulin-stimulated glucose uptake in insulin-resistant adipocytes. Proteomic profiling revealed that ETS1 orchestrates a stress-responsive program involving heme metabolism, iron handling and redox homeostasis. Consistent with this, ETS1 knockdown reduced cellular heme and labile iron levels and attenuated oxidative stress under insulin-resistant conditions. Collectively, these findings demonstrate the power of systems genetics to identify previously unrecognised regulators of adipose insulin action and establish the heme-iron axis as a critical determinant of adipocyte insulin responsiveness.

systems biology↗

bioRxiv2026

Timing of transient darkness shapes carbon-nitrogen metabolism and sugar signaling in sugarcane

Fluctuating light is common in field environments. Yet, the mechanisms by which C4 crops coordinate carbon and nitrogen metabolism during short-term carbon deprivation remain poorly understood. Here, we imposed transient darkness at different phases of the diel cycle to assess how the timing of light loss affects photosynthesis, carbohydrate turnover, amino acid dynamics, and sugar-sensing pathways in commercial sugarcane leaves. Early-day darkness significantly impaired photosynthetic induction and revealed a temporal disconnect between stomatal and metabolic limitations, whereas midday and late-day treatments caused temporary, time-specific disruptions in carbon assimilation. These shifts altered the balance between sucrose preservation and catabolic mobilization, leading to treatment-dependent changes in starch reserves and free amino acids. Core circadian components largely maintained their phase relationships, but their amplitudes varied across treatments, consistent with partial decoupling from carbon status. Darkness also reorganized energy signaling, with SnRK1 and DIN6 responses associated with greater declines in sucrose. Notably, trehalose-pathway transcripts showed marked changes in network connectivity, with ScTPSIIG consistently emerging as a highly connected candidate associated with photosynthetic performance, water-use traits, sugar sensing, and amino acid metabolism. Overall, these results indicate that the timing of carbon limitation and residual sucrose availability shape distinct metabolic responses, while trehalose metabolism provides a candidate regulatory layer coordinating carbon-nitrogen adjustment during the diel cycle, highlighting class II TPS proteins as targets for functional investigation of metabolic resilience in sugarcane.

plant biology↗

bioRxiv2026

Loss of ELM1B impairs mitochondrial fission, matrix redox state and stress tolerance in Physcomitrium patens

Mitochondria are endosymbiont-derived organelles that play a central role in cellular metabolism, energy production and stress responses. While single mitochondria represent functional units, they continuously exchange their contents through fusion and fission, facing stress conditions as a dynamic population. To date, it remains largely unknown how stress alters mitochondrial dynamics in plants and how altered dynamics affect mitochondrial properties and plant stress resilience. Here, we investigate mitochondrial dynamics in response to oxidative stress in the non vascular model plant Physcomitrium patens. By creating mutants with impaired mitochondrial fission in different reporter lines for mitochondrial parameters, we additionally analyse effects of chronic changes to mitochondrial population dynamics. We found that Mito-Paraquat (MtPQ) treatment increased the glutathione redox potential EGSH in mitochondria, the cytosol and chloroplasts, as monitored via roGFP2-based genetically encoded biosensors. Mitochondria elongated within hours and showed a concomitant and heterogenous increase of matrix EOSred, that we propose as a marker for matrix protein damage. Mitochondrial fission mutants lacking PpELM1B (ELONGATED MITOCHONDRIA) displayed distinct changes of mitochondrial morphology parameters as determined by automated 3D-segmentation and feature mapping (MorphoMapper) of confocal z-stacks. Elongated mitochondria in Ppelm1bge lines showed an oxidative matrix EGSH shift and increased matrix EOSred while matrix mixing still occurred, albeit at the same slow rate as in wildtype, within days. Macroscopically, Ppelm1bge lines displayed reduced growth, decreased respiration, and a higher sensitivity to oxidative stress. Our results show that plant mitochondrial morphology and physiological parameters specifically shift in response to stress and impaired fission. Mitochondrial fission is vital to maintain a healthy mitochondrial population that sustains plant oxidative stress tolerance.

plant biology↗

bioRxiv2026

Stomatal and xylem plasticity, not growth rate, determines white spruce resilience to warmer and drier climates

In a warmer and drier climate, forest productivity will depend on trees' ability to maintain carbon uptake and hydraulic function. Whether fast-growing genotypes of boreal conifers are more vulnerable to combined climatic stress remains uncertain. Using a full-factorial field experiment, we investigated how progressive soil drying combined with extended warming affects growth, xylem development, and photosynthesis in two Picea glauca families with contrasting growth strategies. Rainout structures first reduced soil moisture from 25% to 18%, followed by a +5{degrees}C warming treatment applied using infrared heaters. During the warmest and driest period in August, air temperature reached 34.5{degrees}C in the warmed plots, while soil moisture declined to a low of 15% in the combined rainout and warming treatment. Contrary to expectations, both fast- and slow-growing white spruce families exhibited similar resilience to concurrent warming and soil drying. This finding challenges the prevailing theory that faster growth increases vulnerability to climatic stress. Despite an approximately 50% reduction in rainfall, pre-dawn water potential remained above -0.5 MPa across treatments, reflecting that seedlings were able to avoid hydraulic stress. Although the fast-growing family maintained greater height and diameter growth compared to the slow-growing family, both exhibited similar physiological and anatomical responses to warming. Warming decreased stomatal conductance, which increased intrinsic water-use efficiency. Latewood xylem traits related to hydraulic efficiency were also reduced under warming. Together, these coordinated stomatal and xylem adjustments decreased water loss and protected hydraulic function, enabling both families to maintain high photosynthesis and growth under simulated climate conditions. Overall, white spruce exhibits strong phenotypic plasticity, supporting intraspecific resilience to moderate warming and soil drying representative of projected 21st-century summer conditions for central and eastern Canada.

plant biology↗

bioRxiv2026

Stop codon readthrough in Trichomonas is a mechanism for gene expression regulation and expanding protein function

Trichomonas vaginalis is the causative agent of trichomoniasis, a common sexually transmitted infection among women of reproductive and peri-menopausal age. The parasite has an unusually large genome, rich in complex repeats, including a vast repertoire of transposable elements and multi-copy gene families. Since very few T. vaginalis genes have introns, gene expression is usually straightforward, with ribosomal translational machinery proceeding from a start codon to the next in-frame stop codon of an unspliced poly(A)denylated mRNA. However, our previous studies raised the possibility of T. vaginalis gene expression involving stop codon readthrough (SCR), where transcription through in-frame stop codons produces longer-than-predicted mRNAs that translate to fully functional proteins. Here, we leverage long-read RNA-seq and new chromosome-scale assemblies of two T. vaginalis strains and two avian sister species to investigate and characterize ~1,400 long, mature mRNAs that contain more than one predicted protein-coding gene transcribed from what we call '' RT genes '', composites of adjacent predicted genes. We first identify RT genes in a second T. vaginalis strain and in close relatives T. vaginalis-like and T. stableri, indicating that this phenomenon is conserved among Trichomonas species and strains. Second, we find transcripts of RT genes to be more abundant by many orders of magnitude than monocistronic genes. Third, we found the distance between predicted genes within RT genes to be significantly shorter than between adjacent independent predicted genes. Fourth, functional annotation revealed that RT genes encode at least 50 distinct protein functions, suggesting that this unusual transcriptional mechanism has a role in an array of biological processes in Trichomonas. Our results from two Trichomonas species suggest that SCR is an important mechanism controlling gene expression and the diversity of protein function in this parasite.

molecular biology↗