Biology subjects

Jansen, S.

Publications and source records attributed to Jansen, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Invasive mosquito species Aedes aegypti and Aedes albopictus are competent vectors for Barmah Forest Virus

Barmah Forest Virus (BFV), an arthropod-born virus transmitted by mosquitoes, is of significant public health concern in Australia and regions in the Pacific. Recent climate change and globalization raise the potential for BFV to extend its geographic distribution. Despite the rising importance of BFV, its vector dynamics remain poorly understood, particularly concerning the vector competence of different mosquito species. This study aims to investigate the vector competence of BFV across various mosquito species, beyond those endemic to the Australasian region, especially focusing on global relevant vector species. No transmission was observed for Culex quinquefasciatus and Cx. torrentium as well as Anopheles stephensi. In contrast, both investigated Aedes species, Ae. aegypti as well as Ae. albopictus, exhibited BFV-positive saliva across all four temperature profiles (18{degrees}C, 21{degrees}C, 24{degrees}C or 27{degrees}C) examined. These two invasive mosquito species must therefore be classified as potential vectors for BFV, indicating the potential risk of BFV transmission outside of Australia.

molecular biology↗

bioRxiv2026

Adaptive variation in drought-related traits across southern and central European white oak (Quercus sect. Quercus) populations

European white oaks grow from the Mediterranean coast to Southern Scandinavia, a huge environmental gradient that has likely fostered environmental adaptation. In the face of climate change, leveraging adaptations through assisted gene flow could help improve drought tolerance and maintain forest health, but requires an understanding of the species-specific patterns of adaptation to be successful at the target location. In this study, three common gardens were established in Switzerland, Tuerkiye, and Austria for two European white oak species (Quercus robur, and Q. pubescens) using provenances from Central and Southern Europe. Almost 900 oak seedlings were measured at key water-use efficiency and life history traits for their first two year of life and genotyped with low coverage whole-genome sequencing. Trait heritability and environmental adaptation were then explored through pedigree-free animal models, while the genomic architecture of traits was mapped using a genome wide association study ("GWAS"). Across the species, the heritability of measured traits was moderate to high, but common garden had a strong impact, signalling an environmental effect on the phenotype. Adaptation to precipitation seasonality was detected in key productivity and growth traits for both species, but had a small effect on absolute trait values. The GWAS identified a striking 150 kbp association in the Cyclic Nucleotide-Gated Ion Channel gene family with leaf d13C values. This gene family is involved in stomata opening and likely impacts the intrinsic water use efficiency under stress. Together, the strong signals of phenotypic plasticity and rather weak signals of climatic adaptation in seedlings suggest that assisted gene flow in these two white oaks is relevant only for highly drought-sensitive populations, if conducted managers should focus on seeds sources with high precipitation seasonality and smaller leaf sizes.

evolutionary biology↗

bioRxiv2026

Beyond air-seeding: Dynamic, multiphase interactionsreveal a two-step mechanism of embolism propagation inangiosperm xylem

BackgroundThe mechanism underlying drought-induced embolism in angiosperm xylem has been attributed to air-seeding. This concept describes the bulk flow of gas from embolised to neighbouring conduits through the penetration of gas-liquid menisci across pores in interconduit pit membranes. While there is compelling evidence for the spatial propagation of embolism, air-seeding rests on various simplifying assumptions. Among others, air-seeding presumes that xylem sap has physical properties comparable to pure water, that pit membranes can be approximated as structures with simple pores, and that embolism occurs whenever a gas-liquid interface crosses a pit membrane. ScopeRecent experimental and theoretical work demonstrates that the biophysical conditions and processes governing gas-liquid interactions at interconduit pit membranes are fundamentally more dynamic and complex than assumed by air-seeding. These phenomena include: (1) gas movement through constriction pore networks, (2) insoluble, polar lipids at conduit surfaces and interfaces, (3) dynamic surface tension of xylem sap that depends on the local packing density of interfacial lipids, (4) bubble snap-off dynamics within pit membranes, (5) surfactant-stabilized nanobubbles in sap that is oversaturated with dissolved gas, and (6) electrostatic interactions between charged interfaces. Importantly, embolism propagation involves bubble generation and embolism formation as distinct, temporarily and spatially separated processes. Embolism formation occurs when nanobubbles become unstable, whereas nanobubbles below critical stability thresholds can remain stable in sap-filled conduits. ConclusionsTogether, these findings reconfirm that pit membranes function as safety valves enabling water transport according to the cohesion-tension theory, and provide mechanistic insights into embolism propagation. They address the question why plants do not suffer constant embolism formation despite negative xylem pressures. We conclude that a revised framework explicitly accounting for the 3D structure of pit membranes, and multiphase, dynamic processes operating within them are required to explain the biophysics underlying water transport and embolism resistance in angiosperm xylem.

plant biology↗

bioRxiv2026

Interconduit pit membranes of temperate angiosperms undergo changes in pit membrane thickness and electron density within the final growth ring

O_LIPit membranes play a crucial role in water transport between neighbouring xylem conduits by providing hydraulic safety and flow resistance. While effects of pit membranes thickness on embolism resistance and temporal changes in the ultrastructure of pit membranes have been documented between sapwood and heartwood, these changes are largely unknown within conduits of the current-year. C_LIO_LIWe studied interconduit pit membranes of branches of eight angiosperm species by sampling wood from a temperate forest over four consecutive seasons, focusing on the latest growth ring. We quantified the pit membrane thickness and greyscale intensity (as a proxy for electron density) using transmission electron microscopy and image analysis. C_LIO_LIOur observations showed considerable interspecific variation in changes to pit membrane thickness and electron density. Several species exhibited the thinnest pit membranes and highest electron density at the end of a growing season, while others showed minimal variation over time. Intra-tree variation showed that changes in pit membrane shrinkage and electron density were associated with conduit diameter: pit membranes in wide conduits showed larger modification over time than narrow ones. C_LIO_LIOur results indicate seasonal changes in the structure and chemistry of angiosperm pit membranes, even within the latest growth ring. While their shrinkage might increase resistance to flow, the occurrence of darker pit membranes indicates coating and penetration by polar lipids, affecting the behaviour of gas-liquid interfaces. We speculate that the degree of modification that pit membranes undergo is mechanistically driven by the sap flow rate, and possibly conduit dimensions. C_LI

plant biology↗

bioRxiv2026

Continuous monitoring of plant transpiration dynamics with a leaf-mounted sensor across environmental conditions

O_LITranspiration plays a central role in plant water relations and strongly influences plant growth. Continuous monitoring is essential for understanding responses to environmental conditions and improving water management in both natural and agricultural systems. Gas-exchange techniques such as infrared gas analysers (IRGAs) and porometers are widely used but are challenging for long-term or large-scale monitoring. On the other hand, the FylloClip is a low-cost, leaf-mounted capacitance sensor developed previously to monitor transpiration by detecting condensation of water vapour near the leaf surface. Here, we evaluated the potential of the FylloClip for monitoring transpiration dynamics and assessed environmental conditions that may affect its performance. C_LIO_LIThe FylloClip was tested under growth chamber, greenhouse, and tropical field conditions. We evaluated how its capacitance measurements respond to rainfall, temperature and humidity, and compared FylloClip measurements with transpiration measured with an IRGA. C_LIO_LIThere was a strong correlation (r = 0.85) between FylloClip and IRGA data. Both systems captured similar diurnal transpiration patterns, with transpiration declining simultaneously under water deficit. Rainfall and very high relative humidity produced FylloClip signals that could be misinterpreted as high transpiration, although transpiration is negligible under these conditions. C_LIO_LIOur results revealed that FylloClips capture temporal patterns of transpiration with high accuracy and resolution, providing a reliable tool for long-term, large-scale monitoring of transpiration dynamics in ecophysiological studies and precision agriculture. C_LI

Plant Biology↗

bioRxiv2026

Not all West Nile virus lineages behave alike: vector competence and minimum infectious dose differences between lineages 1 and 2

The globally distributed arbovirus West Nile virus (WNV) continues to expand across Europe, with rising numbers of human cases and an increasingly broad geographic distribution. WNV is primarily transmitted by mosquitoes of the genus Culex. Out of nine WNV lineages, human pathogenicity has been clearly established for lineages 1 and 2, but differences in their transmission dynamics, such as minimal infectious dose and transmission efficiency, remain poorly understood. In this study, we investigated how viral lineage, mosquito species, and blood meal titer influence the vector competence of two primary WNV vectors from Europe, Cx. pipiens biotype pipiens and Cx. torrentium, as well as the invasive mosquito species Aedes albopictus. Female mosquitoes were fed with increasing blood meal titers containing either of the WNV lineages. After an incubation period of 14 days at a mean temperature of 24{degrees}C, mosquito body titers were quantified, and the presence of infectious viral particles in the saliva was assessed. Our results revealed clear differences between the two lineages. Lineage 2 resulted in higher transmission efficiencies across all three species and required lower infectious doses to cause transmission. Among the tested species, Cx. torrentium proved to be a highly competent vector (max. transmission efficiency = 30%, minimum infectious dose = 105 TCID50/mL), despite its underrepresentation in research. These findings provide detailed insights into how viral lineage, mosquito species, and blood meal titer might shape WNV transmission, informing future risk assessments and efforts to mitigate WNV transmission in Europe.

microbiology↗

bioRxiv2026

Selective class IIa HDAC inhibition reverses diastolic dysfunction in cardiometabolic HFpEF

Heart failure with preserved ejection fraction (HFpEF) is a highly prevalent cardiometabolic syndrome with yet no effective therapies. Here, we report that selectively class IIa histone deacetylases (HDACs) but no other classes of HDACs are enzymatically activated in hearts from HFpEF patients and cardiometabolic HFpEF animal models. Cell type-specific and enzymatic activity-specific genetic loss-of-function models of the cardiomyocyte-enriched class IIa HDAC family member HDAC4 and the pharmacological class IIa HDAC-selective inhibitor TMP195 prevent and reverse diastolic dysfunction and exercise intolerance in cardiometabolic HFpEF in vivo. In contrast to pan-HDAC inhibition no adverse effects are observed. Despite its well-known non-enzymatic role as transcriptional repressor, we found that specifically enzymatic activation of HDAC4 has little direct effects on cardiomyocyte-intrinsic gene expression. Instead, non-epigenetic actions lead to endothelial activation via altered cardiocrine signaling. We discovered that selective enzymatic class IIa HDAC inhibition is a new therapeutic concept to combat cardiac HFpEF.

molecular biology↗

bioRxiv2025

DISCO-seq: 3D single-cell transcriptomics of intact biological systems

Single-cell transcriptomics has transformed tissue analysis, yet current methods struggle to integrate whole-tissue 3D architecture. Conventional techniques restrict molecular profiling to pre-selected 2D sections, losing systemic context and introducing anatomical bias by sampling less than 0.001% of a whole organism. To overcome these challenges, we developed DISCO-seq, a tissue-clearing chemistry that enables superior RNA accessibility compared to fresh or fixed tissues. DISCO-seq integrates whole-organ or organism 3D imaging with both untargeted and targeted transcriptomics, yielding high-quality RNA from cleared tissues comparable to standard samples. We demonstrate its versatility by investigating tumor heterogeneity in a syngeneic glioblastoma mouse model, using 3D imaging to identify spatially distinct microenvironments and characterize their unique transcriptomic signatures. Moreover, DISCO-seq enabled unbiased, whole-body mapping of SARS-CoV-2 S1 protein deposition in mice, followed by transcriptomic profiling of spatially defined niches. By bridgingmesoscale 3D imaging with single-cell transcriptomics, DISCO-seq establishes a paradigm for anatomically contextualized, hypothesis-free tissue interrogation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/693352v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@758ee5org.highwire.dtl.DTLVardef@1f862c6org.highwire.dtl.DTLVardef@1cf3b9org.highwire.dtl.DTLVardef@c5082e_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIDISCO-seq integrates RNA-preserving tissue-clearing chemistry with whole-organ or organism 3D imaging, enabling anatomically unbiased single-cell transcriptomics. C_LIO_LIDISCO-seq yields RNA quality and transcriptome profiles equivalent to those obtained from matched fresh or fixed tissues. C_LIO_LIDISCO-seq identifies discrete glioblastoma microenvironments and defines their transcriptomic states within the intact brain. C_LIO_LIDISCO-seq enables whole-body mapping of SARS-CoV-2 S1 and uncovers region-specific immune and metabolic responses across anatomical niches. C_LI Supplementary movies can be seen at: http://discotechnologies.org/DISCO-seq/

systems biology↗

bioRxiv2025

The SI compartment model describes embolism spreading in networks of vessels and bordered pits in angiosperm xylem

Plant xylem consists of a network of interconnected vessels, through which water is transported under negative pressure. Filling of vessels with air, or embolism, disturbs this transport process and, in extreme cases, leads to tree mortality. Despite this significance, embolism propagation dynamics are still poorly understood, primarily because xylem is opaque to direct observation. Furthermore, existing models of embolism spreading build excessively on physiological and anatomical parameters, and many misrepresent the inter-vessel pit membrane as a 2D surface. Here, we first extend these physiological models by implementing the pit membrane as a 3D object. Then, we introduce a susceptible-infected (SI) model, a simple stochastic model for tracking spreading through a population, for embolism propagation. After correctly fitting the spreading probability, our SI model reproduces vulnerability curves produced by both the physiological model and empirical data, highlighting that the SI model can address embolism spreading dynamics in plant species, for which detailed physiological data are not available. Furthermore, relating the SI model to the physiological one allows interpreting embolism spreading as a directed percolation process. Elucidating the exact mapping between directed percolation and embolism spreading will likely yield new fundamental insights into the relationships between xylem network architecture and embolism dynamics.

plant biology↗

bioRxiv2025

Dengue virus harnesses mosquito Syntenin to load and secrete viral RNA into salivary exosomes

Viruses exploit extracellular vesicles (EVs) to transfer infection-enhancing viral RNAs. However, mechanisms underlying viral RNA loading remain elusive. We leveraged our previous discovery that dengue virus secretes transmission-enhancing subgenomic flaviviral RNA (sfRNA) into mosquito salivary EVs to investigate viral RNA loading mechanism. We demonstrate that sfRNA alone promotes the secretion of sfRNA-containing EVs marked by the mosquito EV biogenesis protein AeSyntenin, by applying microscopy and viral genetic editing in in vitro and in vivo models. SfRNA via its stem loop structures interacts intracellularly with mosquito AeSyntenin and this interaction is selectively maintained within EVs as shown by complementary RNA-affinity chromatography and RNA immunoprecipitation, and AI-based prediction. Finally, we used systemic and salivary gland-specific protein depletion to establish a functional role for mosquito AeSyntenin in exosome production and salivary secretion of sfRNA. We propose that sfRNA binds AeSyntenin to drive its selective packaging and release into exosomes, elucidating a mechanism for viral RNA incorporation into EVs. Significance statementViruses hijack extracellular vesicles (EVs) to enhance viral dissemination, but the mechanisms enabling selective viral RNA packaging into EVs remain unclear. Specifically, dengue virus transmission by mosquitoes relies on EV-based delivery of an immune-inhibitory subgenomic flaviviral RNA (sfRNA). Here, we uncover how dengue virus sfRNA is actively sorted into EVs from mosquito saliva. We show that sfRNA alone induces its secretion via EVs. We discover that sfRNA directly interacts with AeSyntenin intracellularly, and that this interaction persists in secreted EVs. Functional depletion studies reveal AeSyntenins role in salivary EV formation and sfRNA secretion. These findings establish a novel paradigm by which viral RNAs exploit vector EV pathways for dissemination.

microbiology↗

bioRxiv2025

Domain-specific folding of the tandem β-propeller protein Coronin 7 (Coro7) by CCT/TRiC

The Chaperonin containing tailless complex polypeptide 1 (CCT) or TCP-1 ring complex (TRiC) plays a central role in maintaining cellular homeostasis by supporting protein folding and damping protein aggregation. Besides the abundant cytoskeletal proteins, actin and tubulin, CCT/TRiC is emerging as an obligate chaperone for WD40 proteins, which are comprised of one or multiple {beta}-propeller domains. To date, only WD40 proteins consisting of a single {beta}-propeller domain have been described as CCT/TRiC substrates. Using a combination of biotin proximity ligation, mass spec analysis and co-immunoprecipitation, we here identify the tandem {beta}-propeller protein, Coronin 7 (Coro7), as a novel CCT/TRiC interactor. Transient knockdown of CCT/TRiC further severely diminished expression of Coro7, suggesting that Coro7 is a bona fide CCT/TRiC substrate. Interestingly, co-immunoprecipitation of truncated Coro7 proteins demonstrated that CCT/TRiC only interacts with the first {beta}-propeller domain of Coro7. In line with this, fusion of a miniTurboID tag to the N- or C-terminus of Coro7 showed significant enrichment of all CCT/TRiC subunits for the first, but not the second {beta}-propeller domain. Similarly, co-immunoprecipitation with individual Coro7 {beta}-propeller domains generated by introduction of a protease cleavage site in full length Coro7, confirmed that CCT/TRiC only binds to the first {beta}-propeller domain. Altogether, our study shows that CCT/TRiC can also function as a chaperone for multi-{beta}-propeller domain proteins, likely by initiating the folding of the first {beta}-propeller domain, which can then help template autonomous folding of consecutive {beta}-propeller domains.

biochemistry↗

bioRxiv2025

Human colon stem cells are the principal epithelial responders to bacterial antigens

Intestinal epithelial cells (IECs) are capable of mounting an adequate antimicrobial inflammatory response to pathogens while tolerating commensals. The underlying regulatory mechanisms of immune sensitivity remain incompletely understood, particularly in the context of human IECs. To enhance our understanding of the immune response of IECs to bacterial epithelial barrier breach, we investigated whether epithelial responsiveness is contingent on cell identity and cell polarization. We exposed human intestinal organoids to bacterial antigens to study their immune responses. Notable discrepancies were observed in the specific reactions exhibited by intestinal stem cells (ISCs) and enterocytes. It was determined that basolateral exposure of IECs to bacterial antigens resulted in a robust response, whereas apical exposure elicited a significantly more modest response. We identified ISCs as the responders, while the reaction of enterocytes was found to be attenuated. The regulation of bacterial responsiveness in enterocytes occurs at multiple levels, including the modulation of NF{kappa}B activation and post-transcriptional control of mRNA stability. Our findings demonstrate that differentiated non-responsive enterocytes can be sensitized to bacterial antigens through the activation of the WNT pathway. These findings extend the crucial role of WNT signaling for intestinal epithelial homeostasis and regulation of stem cell maintenance, proliferation, differentiation, and tissue architecture in the gut. Additionally, they reveal a new function of WNT signaling in regulating microbial responses within the intestinal environment.

immunology↗

bioRxiv2024

Mosquito Wing Image Repository for Advancing Research on Geometric Morphometric- and AI-Based Identification

Accurate identification of mosquito species is essential for effective vector control and mitigation of mosquito-borne disease outbreaks. Traditional morphological identification requires highly specialized personnel and is time-consuming, while molecular techniques can be cost-effective and dependent on comprehensive genetic information. Wing geometric morphometry has emerged as a promising alternative, leveraging detailed geometric measurements of wing shapes and vein patterns to distinguish between species and detect intraspecies variations. This paper presents a curated dataset of 18,104 mosquito wing images, collected from 10,500 mosquito specimens, annotated with extensive meta-information, designed to support research in wing geometric morphometry and the development of machine learning models, ultimately supporting efforts in vector surveillance and research.

ecology↗

bioRxiv2024

Thymidine kinase-expressing yellow fever 17D reporter virus facilitates prodrug activation and bioorthogonal labelling of infected cells

Tracking of viral replication and tissue tropism by in vivo imaging can help to unveil how live-attenuated vaccines such as the yellow fever 17D (17D) work, and likewise, to understand how adverse effects develop. Here we validate 17D-TK, a reporter virus derived from 17D that expresses herpes virus thymidine kinase (TK) that specifically converts nucleoside analogues such as Ganciclovir (GCV) to induce cell death, or difluoro-EdU (dF-EdU) for bioorthogonal labelling of infected cells by Click chemistry. 17D-TK induces a cytopathic effect in infected cell cultures, as well as mortality in intracranially inoculated mouse pups in a GCV dependent manner. Preferential phosphorylation of difluoro-EdU (dF-EdU) in 17D-TK infected cells allows to selectively stain cells that support 17D replication. Prospectively, 17D-TK can be used in combination with radiolabeled tracers for real-time detection and localization of sites of active viral replication in living animals using positron emission tomography (PET).

microbiology↗

bioRxiv2024

Time-based shifts in xylem vulnerability curves of angiosperms based on the flow-centrifuge method

Centrifuges provide a fast and standard approach to quantify embolism resistance of xylem in vulnerability curves (VCs). Traditionally, embolism formation in centrifuge experiments is assumingly driven by centrifuge speed, and thus pressure, but unaffected by spin time. Here, we explore to what extent embolism resistance is not only pressure but also spin time dependent, and hypothesise that time-stable hydraulic conductivity (Kh) values could shift VCs. We quantified time-based shifts in flow- centrifuge VCs and their parameter estimations for six angiosperm species by measuring Kh at regular intervals over 15 minutes of spinning at a particular speed before a higher speed was applied to the same sample. We compared various VCs per sample based on cumulative spin time, and modelled the relationship between Kh, xylem water potential ({Psi}), and spin time. Time-based changes of Kh showed considerable increases and decreases at low and high centrifuge speeds, respectively, which generally shifted VCs towards more positive {Psi} values. Values corresponding to 50% loss of hydraulic conductivity (P50) increased up to 0.72 MPa in Acer pseudoplatanus, and on average by 8.5% for all six species compared to VCs that did not consider spin time. By employing an asymptotic exponential model, we estimated time-stable Kh, which improved the statistical significance of VCs in 5 of the 6 species studied. This model also revealed the instability of VCs at short spin times, and showed that embolism formation in flow-centrifuges followed a saturating exponential growth curve. Although pressure remains the major determinant of embolism formation, spin time should be considered in flow- centrifuge VCs to avoid overestimation of embolism resistance. This spin-time artefact is species- specific, and likely based on relatively slow gas diffusion associated with embolism spreading. It can be minimized by determining time-stable Kh values for each centrifuge speed, without considerably extending the experimental time to construct VCs.

plant biology↗

bioRxiv2024

Dilated cardiomyopathy-associated skeletal muscle actin (ACTA1) mutation R256H disrupts actin structure and function and causes cardiomyocyte hypocontractility

Skeletal muscle actin (ACTA1) mutations are a prevalent cause of skeletal myopathies consistent with ACTA1s high expression in skeletal muscle. Rare de novo mutations in ACTA1 associated with combined cardiac and skeletal myopathies have been reported, but ACTA1 represents only [~]20% of the total actin pool in cardiomyocytes, making its role in cardiomyopathy controversial. Here we demonstrate how a mutation in an actin isoform expressed at low levels in cardiomyocytes can cause cardiomyopathy by focusing on a unique ACTA1 mutation, R256H. We previously identified this mutation in multiple family members with dilated cardiomyopathy (DCM), who had reduced systolic function without clinical skeletal myopathy. Using a battery of multiscale biophysical tools, we show that R256H has potent functional effects on ACTA1 function at the molecular scale and in human cardiomyocytes. Importantly, we demonstrate that R256H acts in a dominant manner, where the incorporation of small amounts of mutant protein into thin filaments is sufficient to disrupt molecular contractility, and that this effect is dependent on the presence of troponin and tropomyosin. To understand the structural basis of this change in regulation, we resolved a structure of R256H filaments using Cryo-EM, and we see alterations in actins structure that have the potential to disrupt interactions with tropomyosin. Finally, we show that ACTA1R256H/+ human induced pluripotent stem cell cardiomyocytes demonstrate reduced contractility and sarcomeric disorganization. Taken together, we demonstrate that R256H has multiple effects on ACTA1 function that are sufficient to cause reduced contractility and establish a likely causative relationship between ACTA1 R256H and clinical cardiomyopathy. Significance StatementSkeletal muscle actin mutations are well-known to cause skeletal myopathies, but their role in cardiomyopathies have been controversial as skeletal muscle actin is only expressed at modest levels in the heart. Here, we demonstrate that a skeletal muscle actin mutation potently causes multiple defects in actin function at the atomic and molecular scales, and it functions in a dominant fashion, leading to cardiomyocyte contractile defects. Our results establish how skeletal muscle actin mutations may cause cardiomyocyte dysfunction and lay the foundation for future studies of the role of skeletal muscle actin in cardiomyopathy.

biophysics↗

bioRxiv2024

Thermal acclimation of stem respiration reduces global carbon burden

Stem respiration is a key driver of carbon flux from ecosystems to the atmosphere, yet its response to global warming remains poorly constrained. In particular it has been proposed that stem respiration acclimates to changing temperatures, which could have large implications for carbon cycling under climate change, but no theory exists to predict acclimated respiration rates. Here, we hypothesized that stem respiration is physiologically linked to transpiration in order to maintain hydraulic continuity. We then use that linkage, combined with Eco-evolutionary optimality theory, to develop a theoretical prediction of the temperature sensitivity of both acclimated and instantaneous stem respiration. Leveraging an extensive global dataset, we observe temperature sensitivities of stem respiration across geographical and seasonal variations that are consistent with this prediction. Our findings reveal that stem respiration contributes approximately a quarter of the global above-ground auto-trophic respiration, with an estimated annual emission of around 11.20 {+/-} 5.88 Pg C--comparable to total anthropogenic emissions. Importantly, incorporating thermal acclimation of stem respiration into projections significantly reduces predicted land ecosystem carbon emissions by 4.41 and 9.56 Pg C under the SSP126 and SSP585 scenarios, respectively, for the 21st century.

ecology↗

bioRxiv2023

PCID2 dysregulates transcription and viral RNA processing to promote HIV-1 latency

HIV-1 latency results from tightly regulated molecular processes that act at distinct steps of HIV-1 gene expression. To elucidate the molecular players that govern latency, we previously performed a dCas9-chromatin immunoprecipitation coupled with mass spectrometry (Catchet-MS) and identified the interactome of the latent HIV-1 LTR. Here we characterize the Catchet-MS-identified PCI domain-containing 2 (PCID2) protein, a component of the TREX2 complex, to play a dual role in promoting HIV-1 latency by enforcing both transcriptional repression and post-transcriptional blocks to HIV-1 gene expression. PCID2 bound the latent HIV-1 LTR and repressed transcription initiation during latency. Depletion of PCID2 remodelled the chromatin landscape at the HIV-1 promoter and resulted in transcriptional activation and reversal of latency. Immunoprecipitation coupled to Mass Spectrometry identified PCID2-interacting proteins to include members of the spliceosome, including negative viral RNA (vRNA) alternative splicing regulators, and PCID2 depletion resulted in over-splicing of intron-containing vRNA and misregulated expression of vRNA splice variants. We demonstrate that MCM3AP and DSS1, two other RNA-binding TREX2 complex subunits that comprise the dock of the complex also inhibit transcription initiation and viral RNA alternative splicing during latency and similarly to PCID2 function as prominent latency associated repressors of HIV-1 gene expression. Thus, PCID2 is a novel HIV-1 latency-promoting factor, which in context of the TREX2 sub-complex PCID2-DSS1-MCM3AP blocks transcription and dysregulates vRNA processing.

microbiology↗