Biodiversity loss is, at present, one of the most severe global environmental issues. However, more demanding species are put at greater risk than generalists. Knowledge of the habitat requirements ...of threatened species is essential for defining the levels at which nature conservation efforts should prospectively operate. This study describes the habitat niche of the macrophyte species Myriophyllum alterniflorum DC., based on its occurrence along environmental gradients of sediments, flow velocity, turbidity, depth and shade on five brooks of the Upper Palatinate Forest, Bavaria. To examine the transregional validity of our results, we first carried out an analysis on the Pfreimd River and defined the outcomes as a reference. We then defined a transfer system for the other four brooks with M. alterniflorum occurrences, repeated the analysis and compared the results. We found a general pattern of preferred habitat conditions in combination with a regional aspect influencing the species distribution in each brook. We, suggest a broader formulation of habitat characteristics when aiming to describe a transregional pattern. Instead of preferences, we defined local extinction criteria for this species, namely: i) sediment with saprobic fraction, ii) stagnation of flow velocity, iii) strong turbidity iv) shading > 75% and v) water depth > 100 cm. Furthermore, we found that eutrophication is less effective under high-flow conditions. With its high demands on water quality, M. alterniflorum overlaps with the requirements of other endangered species. Therefore, conservation efforts should focus on promoting high-quality habitats, which include sustainable land management approaches at the catchment level.
•Despite improvements in water quality, biodiversity of vulnerable species remains at risk.•Sediment load, flow velocity, water depth, turbidity and shading concur for local extinction of M. alterniflorum.•Impacts of eutrophication on M. alterniflorum habitat are antagonised by flow velocity.•Increased nitrate concentrations may increase M. alterniflorum cover under high flow conditions.
Apicomplexan parasites, such as the malaria-causing
Plasmodium
, utilize an actin-based motor for motility and host cell invasion. The actin filaments of these parasites are unusually short, and ...actin polymerization is under strict control of a small set of regulatory proteins, which are poorly conserved with their mammalian orthologs. Actin depolymerization factors (ADFs) are among the most important actin regulators, affecting the rates of filament turnover in a multifaceted manner.
Plasmodium
has two ADFs that display low sequence homology with each other and with the higher eukaryotic family members. Here, we show that ADF2, like canonical ADF proteins but unlike ADF1, binds to both globular and filamentous actin, severing filaments and inducing nucleotide exchange on the actin monomer. The crystal structure of
Plasmodium
ADF1 shows major differences from the ADF consensus, explaining the lack of F-actin binding.
Plasmodium
ADF2 structurally resembles the canonical members of the ADF/cofilin family.
Cerebral malaria is one of the most severe complications of malaria disease, attributed to a complicated series of immune reactions in the host. The syndrome is marked by inflammatory immune ...responses, margination of leukocytes, and parasitized erythrocytes in cerebral vessels leading to breakdown of the blood-brain barrier. We show that chemical attenuation of the parasite at the very early, clinically silent liver stage suppresses parasite development, delays the time until parasites establish blood-stage infection, and provokes an altered host immune response, modifying immunopathogenesis and protecting from cerebral disease. The early response is proinflammatory and cell mediated, with increased T cell activation in the liver and spleen, and greater numbers of effector T cells, cytokine-secreting T cells, and proliferating, proinflammatory cytokine-producing T cells. Dendritic cell numbers, T cell activation, and infiltration of CD8(+) T cells to the brain are decreased later in infection, possibly mediated by the anti-inflammatory cytokine IL-10. Strikingly, protection can be transferred to naive animals by adoptive transfer of lymphocytes from the spleen at very early times of infection. Our data suggest that a subpopulation belonging to CD8(+) T cells as early as day 2 postinfection is responsible for protection. These data indicate that liver stage-directed early immune responses can moderate the overall downstream host immune response and modulate severe malaria outcome.
Cyclase-associated proteins (CAPs) are evolutionary conserved G-actin-binding proteins that regulate microfilament turnover. CAPs have a modular structure consisting of an N-terminal adenylate ...cyclase binding domain, a central proline-rich segment, and a C-terminal actin binding domain. Protozoan parasites of the phylum Apicomplexa, such as Cryptosporidium and the malaria parasite Plasmodium, express small CAP orthologs with homology to the C-terminal actin binding domain (C-CAP). Here, we demonstrate by reverse genetics that C-CAP is dispensable for the pathogenic Plasmodium blood stages. However, c-cap(-) parasites display a complete defect in oocyst development in the insect vector. By trans-species complementation we show that the Cryptosporidium parvum ortholog complements the Plasmodium gene functions. Purified recombinant C. parvum C-CAP protein binds actin monomers and prevents actin polymerization. The crystal structure of C. parvum C-CAP shows two monomers with a right-handed β-helical fold intercalated at their C termini to form the putative physiological dimer. Our results reveal a specific vital role for an apicomplexan G-actin-binding protein during sporogony, the parasite replication phase that precedes formation of malaria transmission stages. This study also exemplifies how Plasmodium reverse genetics combined with biochemical and structural analyses of orthologous proteins can offer a fast track toward systematic gene characterization in apicomplexan parasites.
wALADin1 benzimidazoles are specific inhibitors of δ-aminolevulinic acid dehydratase from Wolbachia endobacteria of filarial nematodes. We report that wALADin1 and two derivatives killed blood stage ...Plasmodium falciparum in vitro (50% inhibitory concentrations, 39, 7.7, and 12.8 μM, respectively). One of these derivatives inhibited gliding motility of Plasmodium berghei ANKA infectious sporozoites with nanomolar affinity and blocked invasion into hepatocytes but did not affect intrahepatocytic replication. Hence, wALADin1 benzimidazoles are tools to study gliding motility and potential antiplasmodial drug candidates.
The biological function of the post‐translational modification hypusine in the eukaryotic initiation factor 5A (EIF‐5A) in eukaryotes is still not understood. Hypusine is formed by two sequential ...enzymatic steps at a specific lysine residue in the precursor protein EIF‐5A. One important biological function of EIF‐5A which was recently identified is the translation of polyproline‐rich mRNA, suggesting its biological relevance in a variety of biological processes. Hypusinated eIF‐5A controls the proliferation of cancer cells and inflammatory processes in malaria. It was shown that pharmacological inhibition of the enzymes involved in this pathway, deoxyhypusine synthase (DHS) and the deoxyhypusine hydroxylase (DOHH), arrested the growth of malaria parasites. Down‐regulation of both the malarial eIF‐5A and dhs genes by in vitro and in vivo silencing led to decreased transcript levels and protein expression and, in turn, to low parasitemia, confirming a critical role of hypusination in eIF‐5A for proliferation in Plasmodium. To further investigate whether eIF‐5A and the activating enzyme DHS are essential for Plasmodium erythrocytic stages, targeted gene disruption was performed in the rodent malaria parasite Plasmodium berghei. Full disruption of both genes was not successful; instead parasites harboring the episome for eIF‐5A and dhs genes were obtained, suggesting that these genes may perform vital functions during the pathogenic blood cell stage. Next, a knock‐in strategy was pursued for both endogenous genes eIF‐5A and dhs from P. berghei. The latter resulted in viable recombinant parasites, strengthening the observation that they might be essential for proliferation during asexual development of the malaria parasite.
The malaria parasite has to adapt to different environments in the mammalian host. Sporozoites which are transferred by a bite of a mosquito develop to merozoites in the liver before they invade erythrocytes. Disruption of genes involved in the hypusine pathway, a post‐translational modification of eukaryotic initiation factor 5A, suggests an essential function for the parasite in the erythrocytic stages.
Rhizobial symbiosis is known to increase the nitrogen availability in the rhizosphere of legumes. Therefore, it has been hypothesized that other plants’ roots should forage towards legume neighbours, ...but avoid non-legume neighbours. Yet, root distribution responding to legume plants as opposed to non-legumes has not yet been rigorously tested and might well be subject to integration of multiple environmental cues.
In this study, wedevised an outdoor mesocosm experiment to examine root distributions of the two plant species Pilosella officinarum and Arenaria serpyllifolia in a two-factorial design. While one factor was ‘neighbour identity’, where plants were exposed to different legume or non-legume neighbours, the other factor was ‘nitrogen supply’. In the latter the nutrient-poor soil was supplemented with either nitrogen-free or with nitrogen-containing fertilizer.
Unexpectedly, of all treatments that included a legume neighbour (eight different species or factor combinations), we found merely one case of root aggregation towards a legume neighbour (P. officinarum towards Medicago minima under nitrogen-fertilized conditions). In this very treatment, also P. officinarum root–shoot allocation was strongly increased, indicating that neighbour recognition is coupled with a contesting strategy.
Considering the various response modes of the tested species towards the different legume and non-legume neighbours, we can conclude that roots integrate information on neighbour identity and resource availability in a complex manner. Especially the integration of neighbour identity in root decisions must be a vital aptitude for plants to cope with their complex biotic and abiotic environment in the field.
During the clinically silent liver stage of a Plasmodium infection the parasite replicates from a single sporozoite into thousands of merozoites. Infection of humans and rodents with large numbers of ...sporozoites that arrest their development within the liver can cause sterile protection from subsequent infections. Disruption of genes essential for liver stage development of rodent malaria parasites has yielded a number of attenuated parasite strains. A key question to this end is how increased attenuation relates to vaccine efficacy. Here, we generated rodent malaria parasite lines that arrest during liver stage development and probed the impact of multiple gene deletions on attenuation and protective efficacy. In contrast to P. berghei strain ANKA LISP2(-) or uis3(-) single knockout parasites, which occasionally caused breakthrough infections, the double mutant lacking both genes was completely attenuated even when high numbers of sporozoites were administered. However, different vaccination protocols showed that LISP2(-) parasites protected better than uis3(-) and double mutants. Hence, deletion of several genes can yield increased safety but might come at the cost of protective efficacy.
This study investigated how structural changes of a historical traditionally used forest landscape in Central Europe have affected traits of vegetation and wild bee communities. We compared the ...extent of gaps in the forest using aerial photographs between 1945 and 2020. And we found historic vegetation and bee surveys from 1975 and 1990, which we repeated in 2010 and 2020. We characterised the vegetation of the closed forest, the forest gaps and the small-scale meadows adjacent to the forest as well as the wild bee community by traits and investigated trait changes with Kruskal-Wallis tests. By NMDS we characterised sample plots and transect walks of timepoints with traits and species. Area of forest gaps decreased by 88% from 1945 to 2020 and by 74% from 1975 to 2020. In the traits of vegetation, Ellenberg Indicator Values (EIV) for moisture and soil nutrients significantly increased in closed forest, forest gaps and meadows adjacent to forest. The EIVs for light and temperature, and the number of red list species decreased. The number of wild bee species that specialise in visiting flowers with long tubes and hylophilic species declined. The number of eremophilic species, species with longer phenologies, and recently Red list species increased. In the NMDS figure of forest gaps and of adjacent meadows, different species and traits characterised more recent and older sample plots of vegetation and confirm the results of the Kruskal Wallis tests. Wild bee communities of 2010 and 2020 were characterised by frequent species, while those of 1975 and 1990 were not characterised by any species. The traits characterised the wild bee communities of the older and younger transect walks in accordance with the results of the Kruskal Wallis tests. In addition, oligolectic bees characterised the older transect walks. The loss of forest gaps represents a direct loss of habitat for many plant and wild bee species. In addition, the qualitative changes in vegetation indicate a deterioration in habitat quality for plants of open forests and wild bees. Among wild bees, specialists were negatively affected by the changes described. These developments were reflected in the initial downward trend in Red List bee species. The increase in bee species with longer phenology, in eremophilic species, the decrease in hylophilic species, and the recent increase in red-listed species can indicate climate change. Therefore, this study underlines the importance of the preservation and development of ecologically valuable forest gaps, particularly in historical traditionally used forests with a typical species composition.
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•loss of 88% in forest gaps from 1945 to 2020.•increase in EIV for nitrogen and moisture of vegetation from 1975 to 2020.•decrease in EIV for light, for temperature and Red List species of vegetation.•decline in specialised and hylophilic wild bee species from 1975 to 2020.•increase in eremophilic wild bee species and species with a longer phenology.
How did American cities change throughout the 20th and early 21st century? This timely publication integrates research from American Literary and Cultural Studies, Urban Studies and History. The ...essays range from negotiations of the »ethnic city« in US literature and media, to studies of recent urban phenomena and their representations: gentrification, re- appropriation and conversion of urban spaces in the USA.These interdisciplinary and intercultural perspectives on American cities provide unique points of access for studying the complex narratives of urban transformation.
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