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Root-to-shoot translocation and shoot homeostasis of potassium(K) determine nutrient balance, growth, and stress tolerance of vascular plants. To maintain the cation-anion balance, xylem loading of K⁺ in the roots relies on the concomitant loading of counteranions, like nitrate (NO₃⁻). However, the coregulation of these loading steps is unclear. Here, we show that the bidirectional, low-affinity Nitrate Transporter1 (NRT1)/Peptide Transporter (PTR) family member NPF7.3/NRT1.5 is important for the NO₃⁻-dependent K⁺ translocation in Arabidopsis (Arabidopsis thaliana). Lack of NPF7.3/NRT1.5 resulted in K deficiency in shoots under low NO₃⁻ nutrition, whereas the root elemental composition was unchanged. Gene expression data corroborated K deficiency in thenrt1.5-5shoot, whereas the root responded with a differential expression of genes involved in cation-anion balance. A grafting experiment confirmed that the presence of NPF7.3/NRT1.5 in the root is a prerequisite for proper root-to-shoot translocation of K⁺ under low NO₃⁻ supply. Because the depolarization-activated Stelar K⁺ Outward Rectifier (SKOR) has previously been described as a major contributor for root-to-shoot translocation of K⁺ in Arabidopsis, we addressed the hypothesis that NPF7.3/NRT1.5-mediated NO₃⁻ translocation might affect xylem loading and root-to-shoot K⁺ translocation through SKOR. Indeed, growth ofnrt1.5-5andskor-2single and double mutants under different K/NO₃⁻ regimes revealed that both proteins contribute to K⁺ translocation from root to shoot. SKOR activity dominates under high NO₃⁻ and low K⁺ supply, whereas NPF7.3/NRT1.5 is required under low NO₃⁻ availability. This study unravels nutritional conditions as a critical factor for the joint activity of SKOR and NPF7.3/NRT1.5 for shoot K homeostasis.

The acquisition of nutrients requires tight regulation to ensure optimal supply while preventing accumulation to toxic levels. Ammonium transporter/methylamine permease/rhesus (AMT/Mep/Rh) transporters are responsible for ammonium acquisition in bacteria, fungi, and plants. The ammonium transporter AMT1;1 from Arabidopsis thaliana uses a novel regulatory mechanism requiring the productive interaction between a trimer of subunits for function. Allosteric regulation is mediated by a cytosolic C-terminal trans-activation domain, which carries a conserved Thr (T460) in a critical position in the hinge region of the C terminus. When expressed in yeast, mutation of T460 leads to inactivation of the trimeric complex. This study shows that phosphorylation of T460 is triggered by ammonium in a time- and concentration-dependent manner. Neither Gln nor L-methionine sulfoximine-induced ammonium accumulation were effective in inducing phosphorylation, suggesting that roots use either the ammonium transporter itself or another extracellular sensor to measure ammonium concentrations in the rhizosphere. Phosphorylation of T460 in response to an increase in external ammonium correlates with inhibition of ammonium uptake into Arabidopsis roots. Thus, phosphorylation appears to function in a feedback loop restricting ammonium uptake. This novel autoregulatory mechanism is capable of tuning uptake capacity over a wide range of supply levels using an extracellular sensory system, potentially mediated by a transceptor (i.e., transporter and receptor).

Non-muscle-invasive bladder cancer (NMIBC) is a highly recurrent tumor despite intravesical immunotherapy instillation with the bacillus Calmette-Guérin (BCG) vaccine. In a prospective longitudinal study, we took advantage of BCG instillations, which increase local immune infiltration, to characterize immune cell populations in the urine of patients with NMIBC as a surrogate for the bladder tumor microenvironment. We observed an infiltration of neutrophils, T cells, monocytic myeloid-derived suppressor cells (M-MDSCs), and group 2 innate lymphoid cells (ILC2). Notably, patients with a T cell-to-MDSC ratio of less than 1 showed dramatically lower recurrence-free survival than did patients with a ratio of greater than 1. Analysis of early and later time points indicated that this patient dichotomy existed prior to BCG treatment. ILC2 frequency was associated with detectable IL-13 in the urine and correlated with the level of recruited M-MDSCs, which highly expressed IL-13 receptor α1. In vitro, ILC2 were increased and potently expressed IL-13 in the presence of BCG or tumor cells. IL-13 induced the preferential recruitment and suppressive function of monocytes. Thus, the T cell-to-MDSC balance, associated with a skewing toward type 2 immunity, may predict bladder tumor recurrence and influence the mortality of patients with muscle-invasive cancer. Moreover, these results underline the ILC2/IL-13 axis as a targetable pathway to curtail the M-MDSC compartment and improve bladder cancer treatment.

Heathlands are extensive systems often dominated by slow-growing and long-lived woody plants. These systems require longer-term studies to capture if and how they are changing over time. In 2020, we resurveyed species richness and cover of vascular plant communities in 139 heathlands along the coastline of northern Fennoscandia, first surveyed during 1965–1975. The first survey included six heathland types, each with dominance – a cover of 25% or more – of the dwarf shrubs Calluna vulgaris, Kalmia procumbens, Betula nana, Vaccinium myrtillus and Empetrum nigrum. The two latter heathland types made up 29% and 48%, respectively, of all heathlands. In addition to the dominant dwarf shrubs giving their names to the heathland types, a few other species qualified as dominant. In the resurvey, all the heathland types had E. nigrum as the single dominant species, except for the heathland formerly dominated by B. nana. Most other species had low cover both at the time of the original survey and the resurvey. Also, the heathland types were species poor at the time of the original survey, with an average of eight vascular plant species per 4 m2 and were found equally species poor in the resurvey. Species richness differed between heathland types only at the time of the original survey, and the ratio of species exchange between the two surveys was negatively related to the original cover of E. nigrum. Here we provide a half-century perspective on vegetation change, during which several heathland types in northern Fennoscandia have changed to Empetrum heathlands, reducing the diversity of heathland types across the Boreal to Arctic landscape. As a native plant, E. nigrum cannot be considered invasive, but its allelopathic capacity has likely already modified these heathland ecosystems and will continue to do so, reducing ecosystem multifunctionality across the region.

BackgroundThe primary goal of the CLARYS study is to assess the protection against rebleeding when treating ruptured bifurcation aneurysms with the Woven EndoBridge (WEB) device.MethodsThe CLARYS study is a prospective, multicenter study conducted in 13 European centers. Patients with ruptured bifurcation aneurysms were consecutively included between February 2016 and September 2017. The primary endpoint was defined as the rebleeding rate of the target aneurysm treated with the WEB within 30 days postprocedure. Secondary endpoints included periprocedural and postprocedural adverse events, total procedure and fluoroscopy times, and modified Rankin Scale score at 1 month and 1 year.ResultsSixty patients with 60 ruptured bifurcation aneurysms to be treated with the WEB were included. A WEB device was successfully implanted in 93.3%. The rebleeding rate at 1 month and 1 year was 0%. The mean fluoroscopy time was 27.0 min. Twenty-three periprocedural complications were observed in 18 patients and resolved without sequelae in 16 patients. Two of these complications were attributed to the procedure and/or the use of the WEB, leading to a procedure/device-related intraoperative complication rate of 3.3%. Overall mortality at 1 month and 1 year was 1.7% and 3.8%, respectively and overall morbidity at 1 month and 1 year was 15% and 9.6%, respectively. WEB-related 1-month and 1-year morbidity and mortality was 0%.ConclusionsThe interim results of CLARYS show that the endovascular treatment of ruptured bifurcation aneurysms with the WEB is safe and effective and, in particular, provides effective protection against rebleeding. It may induce profound change in the endovascular management of ruptured bifurcation aneurysms.

Near-infrared spectroscopy (NIRS) is a high-throughput technology with potential to infer nitrogen (N), phosphorus (P) and carbon (C) content of all vascular plants based on empirical calibrations with chemical analysis, but is currently limited to the sample populations upon which it is based. Here we provide a first step towards a global arctic-alpine NIRS model of foliar N, P and C content. We found calibration models to perform well (R 2 validation  = 0.94 and RMSEP = 0.20% for N, R 2 validation  = 0.76 and RMSEP = 0.05% for P and R 2 validation  = 0.82 and RMSEP = 1.16% for C), integrating 97 species, nine functional groups, three levels of phenology, a range of habitats and two biogeographic regions (the Alps and Fennoscandia). Furthermore, when applied for predicting foliar N, P and C content in samples from a new biogeographic region (Svalbard), our arctic-alpine NIRS model performed well. The precision of the resulting NIRS method meet international requirements, indicating one NIRS measurement scan of a foliar sample will predict its N, P and C content with precision according to standard method performance. The modelling scripts for the prediction of foliar N, P and C content using NIRS along with the calibration models upon which the predictions are based are provided. The modelling scripts can be applied in other labs, and can easily be expanded with data from new biogeographic regions of interest, building the global arctic-alpine model.

The chemical balance between essential nutrients and defense compounds in plants determines the quality of the forage available to herbivores and can be modified by both environmental conditions and herbivores themselves. We investigated whether climate and herbivory affect nutrient and defense compound concentrations across plant functional groups. Concentrations of nutrients—nitrogen (N) and phosphorus (P)—and defense compounds—silicon (Si) and phenolics (Ph)—were measured in plant samples from the locally most abundant species, collected in northern Norway across a gradient in summer temperature and different reindeer grazing regimes. Nutrient and defense compound concentrations varied substantially across species and plant functional groups. In addition, nutrients (N, P) declined over the summer, while defense compounds (Si, Ph) accumulated. Sites with a warmer climate had a stronger decrease in nutrient concentrations over the season. We found no evidence that long‐term contrasts in reindeer herbivory intensity affected the average nutritional quality within plant species. Overall, our results suggest that spatial variation in the nutritional quality in Arctic tundra vegetation is mainly determined by the species composition and by consistent changes over the summer season. In comparison, reindeer herbivory and local climate seem to have relatively little impact on the average nutrient and defense compound concentrations of the plant species, suggesting they mainly alter forage quality through effects on the functional and taxonomic composition of the vegetation.

BackgroundThe CLinical Assessment of WEB device in Ruptured aneurYSms (CLARYS) study has shown that the endovascular treatment of ruptured bifurcation aneurysms with the Woven EndoBridge (WEB) is safe and effective and provides protection against rebleeding at 1 month and 1 year. The 12-month angiographic follow-up is an important endpoint of the study.MethodsThe CLARYS study is a prospective multicenter study conducted in 13 European centers. The study enrolled 60 patients with 60 ruptured aneurysms of the anterior and posterior circulation. The study was conducted with an independent assessment of safety outcomes and imaging.ResultsSixty patients with 60 ruptured bifurcation aneurysms to be treated with the WEB were included. Fifty-three aneurysms (88.3%) had a broad base with a dome to neck ratio <2 (mean 1.6). Of these, 46 patients were evaluated by an independent core laboratory with follow-up imaging performed at 12 months or before eventual retreatment. At 1 year, 19/46 aneurysms (41.3%) were completely occluded (Raymond–Roy grade I), 21/46 (45.7%) had a residual neck and 6/46 (13.0%) had residual aneurysm filling. Adequate occlusion was reported in 40/46 (87%) aneurysms. Six patients underwent target aneurysm retreatment.ConclusionsThe CLARYS study has previously shown that the use of the WEB in the endovascular treatment of ruptured bifurcation aneurysms provides effective protection against rebleeding with a good safety profile. The angiographic occlusion rates at 1 year reported here are comparable to those already seen in previous multicenter studies which primarily included unruptured aneurysms.

Chemical responses of tundra vegetation and tundra soil to environmental changes are likely to differ, with implications for ecosystem functioning, yet they are rarely compared. Here, we aimed at comparing sensitivity and magnitude of short-term carbon and nitrogen responses of three main tundra ecosystem compartments: vascular plants, mosses, and soil, to two environmental perturbations: herbivore disturbance and warming. In a full-factorial field experiment in the high-Arctic Svalbard, we simulated herbivore disturbance as spring grubbing activity by pink-footed geese (Anser brachyrhynchus) and passively increased summer temperatures using open-top chambers. Manipulations were set up within three habitats that differ in soil moisture and carried out for two consecutive growing seasons. Overall, we found small and few significant responses to herbivore disturbance and warming, suggesting that carbon and nitrogen contents of high-Arctic ecosystems are relatively resistant to these perturbations, at least in the short term. However, the three ecosystem compartments still differed in their sensitivity to perturbations (vascular plants > soil > mosses), and this was exacerbated by their differential sensitivity across habitats (mesic > moist > wet). Also, while vascular plants responded to herbivore disturbance in mesic and wet habitats and to warming in mesic and moist habitats, soil and mosses only responded to herbivore disturbance in mesic and wet habitats, respectively. Responses to treatments were generally consistent across the two growing seasons, despite great differences in temperature conditions and large between-year variations in the chemical composition of the three ecosystem compartments. These findings highlight the potential for environmental perturbations to have small, yet differential short-term impacts on the carbon and nitrogen contents of vascular plants, mosses, and soil, both within and between tundra habitats. Our results imply that assessments of a single ecosystem compartment in a given context cannot be extrapolated to the whole ecosystem, thus stressing the importance of considering both vegetation and soil carbon and nitrogen responses, and how they display across habitats, in order to better understand how environmental changes might affect biogeochemical processes in the tundra. Longer-term studies should dig deeper into the relative role of (simulated) global change drivers vs. natural inter-annual climatic fluctuations for tundra ecosystem carbon and nitrogen dynamics.