Search

Abstract Changing climatic conditions threaten forest ecosystems. Drought, disease and infestation, are leading to forest die-offs which cause substantial economic and ecological losses. In central Europe, this is especially relevant for commercially important coniferous tree species. This study uses climate envelope exceedance (CEE) to approximate species risk under different future climate scenarios. To achieve this, we used current species presence-absence and historical climate data, coupled with future climate scenarios from various Earth System Models. Climate scenarios tended towards drier and warmer conditions, causing strong CEEs especially for spruce. However, we show that annual averages of temperature and precipitation obscure climate extremes. Including climate extremes reveals a broader increase in CEEs across all tree species. Our study shows that the consideration of climate extremes, which cannot be adequately reflected in annual averages, leads to a different assessment of the risk of forests and thus the options for adapting to climate change.

Climate change is a variation in temperature and precipitation for longer periods due to global warming. It has an impact on tree species distribution, composition and diversity of the forests. Our study aims to answer how future climate change is likely to have an impact on the vegetation shift of broad-leaved and coniferous forests. The study used forest resource assessment data (2010–2014) of Nepal to assess vegetation shift from the perspective of climate change scenario. We collected altogether 392 presence points (observations) for broad-leaved forests and 99 for coniferous forests. These occurrence points accompanied by bioclimatic variables and topographical variables (Elevation, Slope and Aspect) were used as input data in a MaxEnt model to predict the distribution of the coniferous and broad-leaved forests. We found a potential area of the near current (1970–2000) coniferous forest replaced by a broad-leaved forest under a climate change scenario (SSP2 4.5 for 2041–2060) and vice versa. The total projected vegetation shift area of Nepal was found to be approximately 1800 km2 (i.e. over 3 % of the total forest area). Out of the total vegetation shift area, almost 90 % percent of the area was found to be replaced by broad-leaved forest while the remaining 10 % area was found to be replaced by a coniferous forest. The climate change impact has been noticed in the vegetation shift, particularly the presence of broad-leaved forest is more dominant. The study provides better insights into the impact of climate change on the existing vegetation under the future climate change scenario.

IntroductionMany factors, such as climate, topography, forest management, or tree/forest attributes, influence soil organic carbon (SOC) and above-ground tree biomass (AGTB). This study focuses on assessing relationship between various predictor variables and response variables (SOC and AGTB) in the perspective of climate change scenario. The study was conducted throughout in Nepal using forest resource assessment data (2010–2014).MethodsOur study applied a random forest model to assess the status of SOC and AGTB under future climate change scenarios using 19 bioclimatic variables accompanied by other variables such as altitude, aspect, basal area, crown cover development status, distance to settlement forest types, number of trees, macro-topography, management regime, physiographic zones, slope, and soil depth. The study used 737 (70%) samples as a training data for model development while 312 (30%) samples as a testing data for model validation.Results and discussionThe respective RMSE, RMSE% and adjusted R2 of the Random Forest Model for SOC estimation were found to be 9.53 ton/ha, 15% and 0.746 while same for the AGTB were 37.55 ton/ha, 21.74% and 0.743. Particularly, changes in temperature and precipitation showed an effect on the amount of SOC and AGTB in the projected scenario i.e., CMIP6, SSP2 4.5 for 2040–2060. The study found the amount of SOC decreased by 3.85%, while AGTB increased by 2.96% in the projected scenario. The proposed approach which incorporates the effect of bioclimatic variables can be a better option for understanding the dynamics of SOC and AGTB in the future using climatic variables.

Abstract The development of efficient network nodes is a key element for the realization of quantum networks which promise great capabilities as distributed quantum computing or provable secure communication. We report the realization of a quantum network node using a trapped ion inside a fiber-based Fabry–Perot cavity. We show the generation of deterministic entanglement at a high fidelity of 90.1(17)% between a trapped Yb ion and a photon emitted into the resonator mode. We achieve a success probability for generation and detection of entanglement for a single shot of 2.5 × 10−3 resulting in 62 Hz entanglement rate.

Abstract Background The knowledge gap regarding post-logging carbon recovery by increased growth is becoming more crucial to understand the significant contribution of forest to climate change mitigation. We assessed the ability of tropical forests in Indonesia to recover carbon following conventional logging. We evaluated carbon re-growth of 10,415 trees in permanent sample plots (PSPs) in East Kalimantan. Four different post-harvesting silvicultural treatments including liberation, refining, thinning, and control were applied in the PSPs. We estimated the carbon recovery period using three different scenarios of total carbon losses due to logging. In the first scenario, we used an existing factor of logging damage and increased it for assuming the range of carbon losses due to different logging practices. Results Under the existing conventional logging practice, the concession annually emits 51.18 tC∙ha− 1, of which 16.8% are extracted from the forest as raw timber, 38% are logging losses, and 45.2% are emissions due to infrastructure development for logging operation. Increasing the logging damage factor two and three times led to an increase in carbon emission to 70.76 and 90.34 tC∙ha− 1, respectively. The recovery time of the aboveground carbon is 26 years in Scenario 1, 36 years in Scenario 2, and 46 years in Scenario 3. We found no significant effect of the silvicultural treatment type on carbon recovery, but significant effect of the sites was observed. Conclusions We found that the time taken to restore the carbon to the level found in undisturbed forests is considerably longer than the current intervention cycles. The time needed to recover biomass and carbon-stock noticeably depends on the intensity of logging interventions, demonstrating the benefits of using improved harvesting e.g., reduced impact logging to reduce emissions. The study found that site variability has a significant effect on the carbon recovery time. Different silvicultural treatments, on the other hand, have no effect on the recovery time. The study suggests that it is not appropriate to establish an intervention cycle based on arbitrary choice; the time between interventions must be based on logging losses and site specific growth potential to ensure sustainable management of forests.

In this study, we used retrospective dendroclimatological analyses to explore whether El Niño Southern Oscillation (ENSO) and local precipitation patterns have an influence on tree growth in Suriname, a country located on the Guiana Shield, as annual precipitation patterns on the Guiana Shield are related to ENSO. Discs were taken from 20 trees of Cedrela odorata, whose stem forms very distinct annual growth rings, for tree ring analyses. The trees grew in unmanaged tropical wet forests of Suriname. The tree-ring series of individual trees started between 1836 and 1931 and extended over a period of 84–180 years. The 20 dated series were utilized for constructing a tree-ring chronology. Unlike many other studies that used local anomalies such as flood pulse, precipitation, and drought events to describe the influence of El Niño on tree growth, we used monthly precipitation and ENSO indices as predictors of tree growth to calculate response and correlation functions. The study observed that tree ring growth of Cedrela odorata is influenced by precipitation in August and June of the current year and in August of the previous year, as well as by the ENSO indices SSTA, TSA, TNA, and NAO. Systematic increases in the strength of the El Niño southern oscillation (ENSO) teleconnection due to climate change could affect the growth of trees on the Guiana Shield.

Enforcement of the ban on trade in protected tree species is often hampered by insufficient knowledge of species identification by the authorities responsible for control. We present a new method based on a deep learning approach that facilitates the separation of protected and non protected tree species. The classification system used here is based on the image classification model Inception-v3, a so-called transfer learning tool provided by Google. Inceptionv3 uses a convolutional neural network (CNN) for feature extraction and classification and has been pre-trained with 1.2 million images. Input and bottleneck layers of the pre-trained CNN are used to generate new CNNs to which images are passed and classified. As an example of a protected tree species, we have chosen Cedrella odorata, which we compare with 13 other tropical tree species. In a first step, the data set of C. odorata and five other unprotected tree species was partitioned into five groups using a bootstrap algorithm. Then the images of each group were passed to an image classification system and used to generate five CNNs independently. Each CNN assigns image data to the two classes of protected tree species, i.e. C. odorata, or unprotected tree species.The five CNNs were first verified with images of the same six tree species that were used for training. For this purpose, images were taken that were not used for CNN training. 98 percent of the image scans were correctly classified into the two classes of protected and non-protected species. In a second verification step, additional tree species not used for training were presented to the image classification system. Here the correct allocation was reduced to 87 percent. Both the tree species and the CNNs used influence the accuracy of the correct class assignment. Against the background that only a few samples were used to train the CNNs, the accuracy achieved is convincing and shows the potential of simple applicable pre trained deep learning for the operational field inspection of timber loads as a first step to enforce legal timber trade regulations.

We study experimentally and theoretically the response of a two-component Fermi condensate in the strongly interacting regime to a quench of the interaction strength. The quench is realized using a radiofrequency π-pulse to a third internal level with a different interaction strength. We find that the quench excites the monopole mode of the trap in the hydrodynamic regime, and that an initial change of the condensate properties takes place on a timescale comparable or even larger than the quasiparticle relaxation time.

Abstract Background The focus of REDD+ is sensu stricto on maintaining forest carbon stocks. We extend the scope of sustainable management of forest from forests to timber utilization, and study carbon offsets resulting from the utilization of harvested timber for bio energy or harvested wood products (HWPs). The emission budget of harvesting operations depends on the loss of standing biomass by timber extracted from the forest site and logging losses on the one side, and on the other on the wood end use and the utilization of processing residues. We develop two scenarios to quantify the magnitude of CO2 emissions by (1) energetic utilization, and (2) energetic and material utilization of harvested timber and compare the substitution effects for different fossil energy sources. Results The direct energetic use of harvested timber does not compensate for the losses of forest carbon stock. Logging residuals and displacement factors reflecting different wood use constitute by far the most important factor in potential emission reductions. Substitution effects resulting from energetic use of mill residuals and from HWPs have only a subordinated contribution to the total emissions as well as the type of fossil fuel utilized to quantify substitution effects. Material substitution effects associated with harvested wood products show a high potential to increase the climate change benefits. Conclusions The observation and perception of REDD+ should not be restricted to sustainable management and reduced impact logging practices in the forest domain but should be extended to the utilization of extracted timber. Substitution effects from material and energetic utilization of harvested timber result in considerable emission reductions, which can compensate for the loss of forest carbon, and eventually contribute to the overall climate change mitigation benefits from forestry sector.

Sustainable forest management activities, such as future crop tree (FCT) release treatments, became part of the REDD+ strategy to avoid carbon emissions from forests. FCT release treatments are intended to achieve increased growth of FCTs by removing competitor trees. This initially leads to a reduction of the forest carbon pool and represents a carbon debt. We estimated that the time it takes for FCTs to offset the carbon debt through increased growth on experimental sites of 10 km² in Belize, Guyana, Suriname, and Trinidad and Tobago. We further investigated whether the costs of treatment can be compensated by the generated financial carbon benefits. An average of 2.3 FCT per hectare were released through the removal of an average of 3.3 competitors per hectare. This corresponds to an average above ground biomass (AGB) deficit of 2.3 Mg FCT−1. Assuming a 30% increase in growth, the FCT would need on average 130 years to offset the carbon loss. For carbon prices from US$ 5 to 100 Mg CO2e−1 an additional increment between 0.6 and 22.7 Mg tree−1 would be required to cover the treatment costs of US$ 4.2 to 8.4 FCT−1. Assuming a carbon price of US$ 10 Mg CO2e−1, the additional increment required would be between 5.8 and 11.4 Mg tree−1, thus exceeding the biological growth potential of most individual trees. The release of FCTs does not ensure an increase in forest carbon stocks, and refinancing of treatment costs is problematic.

The world's forests play a pivotal role in the mitigation of global climate change. By photosynthesis they remove CO2 from the atmosphere and store carbon in their biomass. While old trees are generally acknowledged for a long carbon residence time, there is no consensus on their contribution to carbon accumulation due to a lack of long-term individual tree data. Tree ring analyses, which use anatomical differences in the annual formation of wood for dating growth zones, are a retrospective approach that provides growth patterns of individual trees over their entire lifetime. We developed time series of diameter growth and related annual carbon accumulation for 61 trees of the species Cedrela odorata L. (Meliacea), Hymenaea courbaril L. (Fabacea) and Goupia glabra Aubl. (Goupiacea). The trees grew in unmanaged tropical wet-forests of Suriname and reached ages from 84 to 255 years. Most of the trees show positive trends of diameter growth and carbon accumulation over time. For some trees we observed fluctuating growth-periods of lower growth alternate with periods of increased growth. In the last quarter of their lifetime trees accumulate on average between 39 percent (C. odorata) and 50 percent (G. glabra) of their final carbon stock. This suggests that old-growth trees in tropical forests do not only contribute to carbon stocks by long carbon resistance times, but maintain high rates of carbon accumulation at later stages of their life time.

We report on the realization of a liquid-filled optical microcavity and demonstrate photon-pair generation by spontaneous four-wave mixing. Our source has a spectral brightness of 45 ± 7 mW ^−2 s ^−1 MHz ^−1 and the bandwidth of the emitted photons is ∼300 MHz. We demonstrate tuning of the emission wavelength between 770 and 800 nm. Moreover, by employing a liquid as the nonlinear optical medium completely filling the microcavity, we observe more than a factor 10 ^3 increase of the pair correlation rate per unit pump power and a factor of 1.7 improvement in the coincidence/accidental ratio as compared to our previous measurements.

Injury and death from wildlife attacks often result in people feeling violent resentment and hostility against the wildlife involved and, therefore, may undermine public support for conservation. Although Nepal, with rich biodiversity, is doing well in its conservation efforts, human-wildlife conflicts have been a major challenge in recent years. The lack of detailed information on the spatial and temporal patterns of human-wildlife conflicts at the national level impedes the development of effective conflict mitigation plans. We examined patterns of human injury and death caused by large mammals using data from attack events and their spatiotemporal dimensions collected from a national survey of data available in Nepal over five years (2010-2014). Data were analyzed using logistic regression and chi-square or Fisher's exact tests. The results show that Asiatic elephants and common leopards are most commonly involved in attacks on people in terms of attack frequency and fatalities. Although one-horned rhinoceros and bears had a higher frequency of attacks than Bengal tigers, tigers caused more fatalities than each of these two species. Attacks by elephants peaked in winter and most frequently occurred outside protected areas in human settlements. Leopard attacks occurred almost entirely outside protected areas, and a significantly greater number of attacks occurred in human settlements. Attacks by one-horned rhinoceros and tigers were higher in the winter, mainly in forests inside protected areas; similarly, attacks by bears occurred mostly within protected areas. We found that human settlements are increasingly becoming conflict hotspots, with burgeoning incidents involving elephants and leopards. We conclude that species-specific conservation strategies are urgently needed, particularly for leopards and elephants. The implications of our findings for minimizing conflicts and conserving these imperiled species are discussed.

The effects of elevated CO2 and interaction effects between elevated CO2 and nutrient supplies on growth and the C/N ratio of European beech (Fagus sylvatica L.) saplings were studied. One-year-old beech saplings were grown in a greenhouse at ambient (385 ppm) and elevated CO2 (770 ppm/950 ppm), with or without fertilization for two growing seasons. In this study, emphasis is placed on the combined fertilization including phosphorus, potassium and nitrogen with two level of elevated CO2. The fertilized plants grown under elevated CO2 had the highest net leaf photosynthesis rate (Ac). The saplings grown under elevated CO2 had a significantly lower stomatal conductance (gs) than saplings grown under ambient air. No interaction effect was found between elevated CO2 and fertilization on Ac. A interaction effect between CO2 and fertilization, as well as between date and fertilization and between date and CO2 was detected on gs. Leaf chlorophyll content index (CCI) and leaf nitrogen content were strongly positively correlated to each other and both of them decreased under elevated CO2. At the end of both growing seasons, stem dry weight was greater under elevated CO2 and root dry weight was not affected by different treatments. No interaction effect was detected between elevated CO2 and nutrient supplies on the dry weight of different plant tissues (stems and roots). However, elevated CO2 caused a significant decrease in the nitrogen content of plant tissues. Nitrogen reduction in the leaves under elevated CO2 was about 10% and distinctly higher than in the stem and root. The interaction effect of elevated CO2 and fertilization on C/N ratio in plants tissues was significant. The results led to the conclusion that photosynthesis and the C/N ratio increased while stomatal conductance and leaf nitrogen content decreased under elevated CO2 and nutrient-limited conditions. In general, under nutrient-limited conditions, the plant responses to elevated CO2 were decreased.

Abstract Background Pseudomonas putida KT2440 has emerged as a promising host for industrial bioproduction. However, its strictly aerobic nature limits the scope of applications. Remarkably, this microbe exhibits high bioconversion efficiency when cultured in an anoxic bio-electrochemical system (BES), where the anode serves as the terminal electron acceptor instead of oxygen. This environment facilitates the synthesis of commercially attractive chemicals, including 2-ketogluconate (2KG). To better understand this interesting electrogenic phenotype, we studied the BES-cultured strain on a systems level through multi-omics analysis. Inspired by our findings, we constructed novel mutants aimed at improving 2KG production. Results When incubated on glucose, P. putida KT2440 did not grow but produced significant amounts of 2KG, along with minor amounts of gluconate, acetate, pyruvate, succinate, and lactate. 13C tracer studies demonstrated that these products are partially derived from biomass carbon, involving proteins and lipids. Over time, the cells exhibited global changes on both the transcriptomic and proteomic levels, including the shutdown of translation and cell motility, likely to conserve energy. These adaptations enabled the cells to maintain significant metabolic activity for several weeks. Acetate formation was shown to contribute to energy supply. Mutants deficient in acetate production demonstrated superior 2KG production in terms of titer, yield, and productivity. The ∆aldBI ∆aldBII double deletion mutant performed best, accumulating 2KG at twice the rate of the wild type and with an increased yield (0.96 mol/mol). Conclusions By integrating transcriptomic, proteomic, and metabolomic analyses, this work provides the first systems biology insight into the electrogenic phenotype of P. putida KT2440. Adaptation to anoxic-electrogenic conditions involved coordinated changes in energy metabolism, enabling cells to sustain metabolic activity for extended periods. The metabolically engineered mutants are promising for enhanced 2KG production under these conditions. The attenuation of acetate synthesis represents the first systems biology-informed metabolic engineering strategy for enhanced 2KG production in P. putida. This non-growth anoxic-electrogenic mode expands our understanding of the interplay between growth, glucose phosphorylation, and glucose oxidation into gluconate and 2KG in P. putida.

Abstract While excessive production of reactive oxygen species (ROS) is a characteristic hallmark of numerous diseases, clinical approaches that ameliorate oxidative stress have been unsuccessful. Here, utilizing multi-omics, we demonstrate that in cardiomyocytes, mitochondrial isocitrate dehydrogenase (IDH2) constitutes a major antioxidative defense mechanism. Paradoxically reduced expression of IDH2 associated with ventricular eccentric hypertrophy is counterbalanced by an increase in the enzyme activity. We unveil redox-dependent sex dimorphism, and extensive mutual regulation of the antioxidative activities of IDH2 and NRF2 by a feedforward network that involves 2-oxoglutarate and L-2-hydroxyglutarate and mediated in part through unconventional hydroxy-methylation of cytosine residues present in introns. Consequently, conditional targeting of ROS in a murine model of heart failure improves cardiac function in sex- and phenotype-dependent manners. Together, these insights may explain why previous attempts to treat heart failure with antioxidants have been unsuccessful and open new approaches to personalizing and, thereby, improving such treatment.

Objective: Combination therapies with gut hormone analogs represent promising treatment strategies for obesity. This pilot study investigates the therapeutic potential of modulators of the glucagon-like peptide 1 (GLP-1) and neuropeptide Y (NPY) system using GLP-1 receptor agonists (semaglutide) and antagonists (exendin 9-39), as well as non-selective and NPY-Y2-receptor selective peptide tyrosine tyrosine (PYY) analogs (PYY3-36/NNC0165-0020 and NNC0165-1273) and an NPY-Y2 receptor antagonist (JNJ31020028). Methods: High-fat diet (HFD)-induced obese rats were randomized into following treatment groups: group 1, nonselective PYY analog + semaglutide (n = 4); group 2, non-selective and NPY-Y2 receptor selective PYY analog + semaglutide (n = 2); group 3, GLP-1 receptor antagonist + NPY-Y2 receptor antagonist (n = 3); group 4, semaglutide (n = 5); and group 5, control (n = 5). Animals had free access to HFD and low-fat diet. Food intake, HFD preference and body weight were measured daily. Results: A combinatory treatment with a non-selective PYY analog and semaglutide led to a maximum body weight loss of 14.0 ± 4.9% vs 9.9 ± 1.5% with semaglutide alone. Group 2 showed a maximum weight loss of 20.5 ± 2.4%. While HFD preference was decreased in group 2, a strong increase in HFD preference was detected in group 3. Conclusions: PYY analogs (especially NPY-Y2 selective receptor agonists) could represent a promising therapeutic approach for obesity in combination with GLP-1 receptor agonists. Additionally, combined GLP-1 and PYY3-36 receptor agonists might have beneficial effects on food preference.

Abstract Background Burn injuries can be associated with prolonged healing, infection, a substantial inflammatory response, extensive scarring, and eventually death. In recent decades, both the mortality rates and long-term survival of severe burn victims have improved significantly, and burn care research has increasingly focused on a better quality of life post-trauma. However, delayed healing, infection, pain and extensive scar formation remain a major challenge in the treatment of burns. ADSCs, a distinct type of mesenchymal stem cells, have been shown to improve the healing process. The aim of this review is to evaluate the efficacy of ADSCs in the treatment of burn injuries. Methods A systematic review of the literature was conducted using the electronic databases PubMed, Web of Science and Embase. The basic research question was formulated with the PICO framework, whereby the usage of ADSCs in the treatment of burns in vivo was determined as the fundamental inclusion criterion. Additionally, pertinent journals focusing on burns and their treatment were screened manually for eligible studies. The review was registered in PROSPERO and reported according to the PRISMA statement. Results Of the 599 publications screened, 21 were considered relevant to the key question and were included in the present review. The included studies were almost all conducted on rodents, with one exception, where pigs were investigated. 13 of the studies examined the treatment of full-thickness and eight of deep partial-thickness burn injuries. 57,1 percent of the relevant studies have demonstrated that ADSCs exhibit immunomodulatory effects during the inflammatory response. 16 studies have shown improved neovascularisation with the use of ADSCs. 14 studies report positive influences of ADSCs on granulation tissue formation, while 11 studies highlight their efficacy in promoting re-epithelialisation. 11 trials demonstrated an improvement in outcomes during the remodelling phase. Conclusion In conclusion, it appears that adipose-derived stem cells demonstrate remarkable efficacy in the field of regenerative medicine. However, the usage of ADSCs in the treatment of burns is still at an early experimental stage, and further investigations are required in order to examine the potential usage of ADSCs in future clinical burn care.

Abstract Cardiac myocyte sodium (Na+) homoeostasis is pivotal in cardiac diseases and heart failure. Intracellular Na+ ([Na+]i) is an important regulator of excitation–contraction coupling and mitochondrial energetics. In addition, extracellular Na+ ([Na+]e) and its water-free storage trigger collagen cross-linking, myocardial stiffening and impaired cardiac function. Therefore, understanding the allocation of tissue Na+ to intra- and extracellular compartments is crucial in comprehending the pathophysiological processes in cardiac diseases. We extrapolated [Na+]e using a three-compartment model, with tissue Na+ concentration (TSC) measured by in vivo 23Na-MRI, extracellular volume (ECV) data calculated from T1 maps, and [Na+]i measured by in vitro fluorescence microscopy using Na+ binding benzofuran isophthalate (SBFI). To investigate dynamic changes in Na+ compartments, we induced pressure overload (TAC) or myocardial infarction (MI) via LAD ligation in mice. Compared to SHAM mice, TSC was similar after TAC but increased after MI. Both TAC and MI showed significantly higher [Na+]i compared to SHAM (around 130% compared to SHAM). Calculated [Na+]e increased after MI, but not after TAC. Increased TSC after TAC was primarily driven by increased [Na+]i, but the increase after MI by elevations in both [Na+]i and [Na+]e.

Transfection of mammalian and human cell lines in medical research both are key technologies in molecular biology and genetic engineering. A vast variety of techniques to facilitate transfection exists including different chemical and nanoparticle-based agents as mediators of nucleic acid uptake, with nanoparticles composed of the lipids DOSPA/DOPE belonging to the established type of agents. We show that inverse-nanoemulsion-derived protein nanohydrogels (NanoTrans-gels), prepared by a simple synthesis protocol, are suited to transfect two model cancer cell lines (MCF7 and A549) with high efficiency. The transfection efficiency was analyzed in comparison to the DOSPA/DOPE-dependent protocols as a reference method. Since nanogel-based transfection outperformed the Lipofectamine-dependent technique in our experiments, we believe that the NanoTrans-gels loaded with plasmid DNA may open new avenues for simple and efficient transfection for humans and probably also other mammalian cell lines and may develop into a general tool for standard transfection procedures in cell biology laboratories.

Abstract Background Long-chain polyunsaturated fatty acids (LC-PUFAs), such as docosahexaenoic acid (DHA), are essential for human health and have been widely used in the food and pharmaceutical industries. However, the limited availability of natural sources, such as oily fish, has led to the pursuit of microbial production as a promising alternative. Yarrowia lipolytica can produce various PUFAs via genetic modification. A recent study upgraded Y. lipolytica for DHA production by expressing a four-gene cluster encoding a myxobacterial PKS-like PUFA synthase, reducing the demand for redox power. However, the genetic architecture of gene expression in Y. lipolytica is complex and involves various control elements, offering space for additional improvement of DHA production. This study was designed to optimize the expression of the PUFA cluster using a modular cloning approach. Results Expression of the monocistronic cluster with each gene under the control of the constitutive TEF promoter led to low-level DHA production. By using the minLEU2 promoter instead and incorporating additional upstream activating UAS1B4 sequences, 5' promoter introns, and intergenic spacers, DHA production was increased by 16-fold. The producers remained stable over 185 h of cultivation. Beneficially, the different genetic control elements acted synergistically: UAS1B elements generally increased expression, while the intron caused gene-specific effects. Mutants with UAS1B16 sequences within 2–8 kb distance, however, were found to be genetically unstable, which limited production performance over time, suggesting the avoidance of long repetitive sequence blocks in synthetic multigene clusters and careful monitoring of genetic stability in producing strains. Conclusions Overall, the results demonstrate the effectiveness of synthetic heterologous gene clusters to drive DHA production in Y. lipolytica. The combinatorial exploration of different genetic control elements allowed the optimization of DHA production. These findings have important implications for developing Y. lipolytica strains for the industrial-scale production of valuable polyunsaturated fatty acids.

Abstract Background Long-chain acyl-carnitines (ACs) are potential arrhythmogenic metabolites. Their role in atrial fibrillation (AF) remains incompletely understood. Using a systems medicine approach, we assessed the contribution of C18:1AC to AF by analysing its in vitro effects on cardiac electrophysiology and metabolism, and translated our findings into the human setting. Methods and results Human iPSC-derived engineered heart tissue was exposed to C18:1AC. A biphasic effect on contractile force was observed: short exposure enhanced contractile force, but elicited spontaneous contractions and impaired Ca2+ handling. Continuous exposure provoked an impairment of contractile force. In human atrial mitochondria from AF individuals, C18:1AC inhibited respiration. In a population-based cohort as well as a cohort of patients, high C18:1AC serum concentrations were associated with the incidence and prevalence of AF. Conclusion Our data provide evidence for an arrhythmogenic potential of the metabolite C18:1AC. The metabolite interferes with mitochondrial metabolism, thereby contributing to contractile dysfunction and shows predictive potential as novel circulating biomarker for risk of AF.

Barth Syndrome (BTHS) is a rare X-linked disease, characterized clinically by cardiomyopathy, skeletal myopathy, neutropenia, and growth retardation. BTHS is caused by mutations in the phospholipid acyltransferase tafazzin (Gene: TAFAZZIN, TAZ). Tafazzin catalyzes the final step in the remodeling of cardiolipin (CL), a glycerophospholipid located in the inner mitochondrial membrane. As the phospholipid composition strongly determines membrane properties, correct biosynthesis of CL and other membrane lipids is essential for mitochondrial function. Mitochondria provide 95% of the energy demand in the heart, particularly due to their role in fatty acid oxidation. Alterations in lipid homeostasis in BTHS have an impact on mitochondrial membrane proteins and thereby contribute to cardiomyopathy. We analyzed a transgenic TAFAZZIN-knockdown (TAZ-KD) BTHS mouse model and determined the distribution of 193 individual lipid species in TAZ-KD and WT hearts at 10 and 50 weeks of age, using electrospray ionization tandem mass spectrometry (ESI-MS/MS). Our results revealed significant lipid composition differences between the TAZ-KD and WT groups, indicating genotype-dependent alterations in most analyzed lipid species. Significant changes in the myocardial lipidome were identified in both young animals without cardiomyopathy and older animals with heart failure. Notable alterations were found in phosphatidylcholine (PC), phosphatidylethanolamine (PE), lysophosphatidylethanolamine (LPE), lysophosphatidylcholine (LPC) and plasmalogen species. PC species with 2–4 double bonds were significantly increased, while polyunsaturated PC species showed a significant decrease in TAZ-KD mice. Furthermore, Linoleic acid (LA, 18:2) containing PC and PE species, as well as arachidonic acid (AA, 20:4) containing PE 38:4 species are increased in TAZ-KD. We found higher levels of AA containing LPE and PE-based plasmalogens (PE P-). Furthermore, we are the first to show significant changes in sphingomyelin (SM) and ceramide (Cer) lipid species Very long-chained SM species are accumulating in TAZ-KD hearts, whereas long-chained Cer and several hexosyl ceramides (HexCer) species accumulate only in 50-week-old TAZ-KD hearts These findings offer potential avenues for the diagnosis and treatment of BTHS, presenting new possibilities for therapeutic approaches.