570 Biowissenschaften; Biologie
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Parasites, such as bacterial viruses (phages), can have large effects on host populations both at the ecological and evolutionary levels. In the case of cyanobacteria, phages can reduce primary production and infected hosts release intracellular nutrients influencing planktonic food web structure, community dynamics, and biogeochemical cycles. Cyanophages may be of great importance in aquatic food webs during large cyanobacterial blooms unless the host population becomes resistant to phage infection. The consequences on plankton community dynamics of the evolution of phage resistance in bloom forming cyanobacterial populations are still poorly studied. Here, we examined the effect of different frequencies of a phage-resistant genotype within a filamentous nitrogen-fixing Nodularia spumigena population on an experimental plankton community. Three Nodularia populations with different initial frequencies (0%, 5%, and 50%) of phage-resistant genotypes were inoculated in separate treatments with the phage 2AV2, the green alga Chlorella vulgaris, and the rotifer Brachionus plicatilis, which formed the experimental plankton community subjected to either nitrogen-limited or nitrogen-rich conditions. We found that the frequency of the phage-resistant Nodularia genotype determined experimental community dynamics. Cyanobacterial populations with a high frequency (50%) of the phage-resistant genotype dominated the cultures despite the presence of phages, retaining most of the intracellular nitrogen in the plankton community. In contrast, populations with low frequencies (0% and 5%) of the phage-resistant genotype were lysed and reduced to extinction by the phage, transferring the intracellular nitrogen held by Nodularia to Chlorella and rotifers, and allowing Chlorella to dominate the communities and rotifers to survive. This study shows that even though phages represent minuscule biomass, they can have key effects on community composition and eco-evolutionary feedbacks in plankton communities.
The Caucasian lynx, Lynx lynx dinniki, has one of the southernmost distributions in the Eurasian lynx range, covering Anatolian Turkey, the Caucasus and Iran. Little is known about the biology and the genetic status of this subspecies. To collect baseline genetic, ecological and behavioural data and benefit future conservation of L. l. dinniki, we monitored 11 lynx territories (396 km(2)) in northwestern Anatolia. We assessed genetic diversity of this population by non-invasively collecting 171 faecal samples and trapped and sampled 12 lynx individuals using box traps. We observed high allelic variation at 11 nuclear microsatellite markers, and found no signs of inbreeding despite the potential isolation of this population. We obtained similar numbers of distinct genotypes from the two sampling sources. Our results indicated that first order female relatives occupy neighbouring territories (female philopatry) and that territorial male lynx were highly unrelated to each other and to female territorial lynx, suggesting long distance male dispersal. Particular male and female resident territorial lynx and their offspring (kittens and subadults) were more likely to be trapped than resident floaters or dispersing (unrelated) lynx. Conversely, we obtained more data for unrelated lynx and higher numbers of territorials using non-invasive sampling (faeces). When invasive and non-invasive samples were analysed separately, the spatial organisation of lynx (in terms of female philopatry and females and males occupying permanent ranges) affected measures of genetic diversity in such a way that estimates of genetic diversity were reduced if only invasive samples were considered. It appears that, at small spatial scales, invasive sampling using box traps may underestimate the genetic diversity in carnivores with permanent ranges and philopatry such as the Eurasian lynx. As non-invasive sampling can also provide additional data on diet and spatial organisation, we advocate the use of such samples for conservation genetic studies of vulnerable, endangered or data deficient territorial species.
Proteasomes are key proteases in regulating protein homeostasis. Their holo-enzymes are composed of 40 different subunits which are arranged in a proteolytic core (CP) flanked by one to two regulatory particles (RP). Proteasomal proteolysis is essential for the degradation of proteins which control time-sensitive processes like cell cycle progression and stress response. In dividing yeast and human cells, proteasomes are primarily nuclear suggesting that proteasomal proteolysis is mainly required in the nucleus during cell proliferation. In yeast, which have a closed mitosis, proteasomes are imported into the nucleus as immature precursors via the classical import pathway. During quiescence, the reversible absence of proliferation induced by nutrient depletion or growth factor deprivation, proteasomes move from the nucleus into the cytoplasm. In the cytoplasm of quiescent yeast, proteasomes are dissociated into CP and RP and stored in membrane-less cytoplasmic foci, named proteasome storage granules (PSGs). With the resumption of growth, PSGs clear and mature proteasomes are transported into the nucleus by Blm10, a conserved 240 kDa protein and proteasome-intrinsic import receptor. How proteasomes are exported from the nucleus into the cytoplasm is unknown.
Hantavirus assembly and budding are governed by the surface glycoproteins Gn and Gc. In this study, we investigated the glycoproteins of Puumala, the most abundant Hantavirus species in Europe, using fluorescently labeled wild-type constructs and cytoplasmic tail (CT) mutants. We analyzed their intracellular distribution, co-localization and oligomerization, applying comprehensive live, single-cell fluorescence techniques, including confocal microscopy, imaging flow cytometry, anisotropy imaging and Number&Brightness analysis. We demonstrate that Gc is significantly enriched in the Golgi apparatus in absence of other viral components, while Gn is mainly restricted to the endoplasmic reticulum (ER). Importantly, upon co-expression both glycoproteins were found in the Golgi apparatus. Furthermore, we show that an intact CT of Gc is necessary for efficient Golgi localization, while the CT of Gn influences protein stability. Finally, we found that Gn assembles into higher-order homo-oligomers, mainly dimers and tetramers, in the ER while Gc was present as mixture of monomers and dimers within the Golgi apparatus. Our findings suggest that PUUV Gc is the driving factor of the targeting of Gc and Gn to the Golgi region, while Gn possesses a significantly stronger self-association potential.
Questions Has plant species richness in semi-natural grasslands changed over recent decades? Do the temporal trends of habitat specialists differ from those of habitat generalists? Has there been a homogenization of the grassland vegetation? Location Different regions in Germany and the UK. Methods We conducted a formal meta-analysis of re-survey vegetation studies of semi-natural grasslands. In total, 23 data sets were compiled, spanning up to 75 years between the surveys, including 13 data sets from wet grasslands, six from dry grasslands and four from other grassland types. Edaphic conditions were assessed using mean Ellenberg indicator values for soil moisture, nitrogen and pH. Changes in species richness and environmental variables were evaluated using response ratios. Results In most wet grasslands, total species richness declined over time, while habitat specialists almost completely vanished. The number of species losses increased with increasing time between the surveys and were associated with a strong decrease in soil moisture and higher soil nutrient contents. Wet grasslands in nature reserves showed no such changes or even opposite trends. In dry grasslands and other grassland types, total species richness did not consistently change, but the number or proportions of habitat specialists declined. There were also considerable changes in species composition, especially in wet grasslands that often have been converted into intensively managed, highly productive meadows or pastures. We did not find a general homogenization of the vegetation in any of the grassland types. Conclusions The results document the widespread deterioration of semi-natural grasslands, especially of those types that can easily be transformed to high production grasslands. The main causes for the loss of grassland specialists are changed management in combination with increased fertilization and nitrogen deposition. Dry grasslands are most resistant to change, but also show a long-term trend towards an increase in more mesotrophic species.
Persulfide groups participate in a wide array of biochemical pathways and are chemically very versatile. The TusA protein has been identified as a central element supplying and transferring sulfur as persulfide to a number of important biosynthetic pathways, like molybdenum cofactor biosynthesis or thiomodifications in nucleosides of tRNAs. In recent years, it has furthermore become obvious that this protein is indispensable for the oxidation of sulfur compounds in the cytoplasm. Phylogenetic analyses revealed that different TusA protein variants exists in certain organisms, that have evolved to pursue specific roles in cellular pathways. The specific TusA-like proteins thereby cannot replace each other in their specific roles and are rather specific to one sulfur transfer pathway or shared between two pathways. While certain bacteria like Escherichia coli contain several copies of TusA-like proteins, in other bacteria like Allochromatium vinosum a single copy of TusA is present with an essential role for this organism. Here, we give an overview on the multiple roles of the various TusA-like proteins in sulfur transfer pathways in different organisms to shed light on the remaining mysteries of this versatile protein.
Estimating parameters from multiple time series of population dynamics using bayesian inference
(2019)
Empirical time series of interacting entities, e.g., species abundances, are highly useful to study ecological mechanisms. Mathematical models are valuable tools to further elucidate those mechanisms and underlying processes. However, obtaining an agreement between model predictions and experimental observations remains a demanding task. As models always abstract from reality one parameter often summarizes several properties. Parameter measurements are performed in additional experiments independent of the ones delivering the time series. Transferring these parameter values to different settings may result in incorrect parametrizations. On top of that, the properties of organisms and thus the respective parameter values may vary considerably. These issues limit the use of a priori model parametrizations. In this study, we present a method suited for a direct estimation of model parameters and their variability from experimental time series data. We combine numerical simulations of a continuous-time dynamical population model with Bayesian inference, using a hierarchical framework that allows for variability of individual parameters. The method is applied to a comprehensive set of time series from a laboratory predator-prey system that features both steady states and cyclic population dynamics. Our model predictions are able to reproduce both steady states and cyclic dynamics of the data. Additionally to the direct estimates of the parameter values, the Bayesian approach also provides their uncertainties. We found that fitting cyclic population dynamics, which contain more information on the process rates than steady states, yields more precise parameter estimates. We detected significant variability among parameters of different time series and identified the variation in the maximum growth rate of the prey as a source for the transition from steady states to cyclic dynamics. By lending more flexibility to the model, our approach facilitates parametrizations and shows more easily which patterns in time series can be explained also by simple models. Applying Bayesian inference and dynamical population models in conjunction may help to quantify the profound variability in organismal properties in nature.
Background: The polymorphism in FTO gene (rs9939609) is known to be associated with higher BMI and body fat mass content. However, environmental factors can modify this effect. The purpose of the present study was to investigate an association between sport specialization and the rs9939609 SNP in FTO gene in the cohort of professional and amateur young athletes. Methods: A total number of 250 young individuals 8-18 years old living in Moscow or Moscow district participated in the study. Individuals were divided into 3 groups in accordance with their physical activity level: control group (n = 49), amateurs (n = 67) and professionals (n = 137). Amateur and professional athletes were subdivided into groups according to their sport specialization. Quantile regression was used as a regression model, where the dependent (outcome) variable was BMI, along with percentage of body fat mass, and the independent variables (predictors) were the rs9939609 SNP in FTO gene, physical activity (active versus inactive), sport specialization (aerobic, intermittent sports and martial arts), nationality, level of sport experience (in years), gender and percentage of free fat mass content. Results: The regression analysis revealed that physical activity and sport specialization had greater impact compared to FTO allele in the group of physically active individuals. Physical activity, in particular aerobic, had negative associations with body fat mass and BMI. The rs9939609 SNP in FTO gene is associated with physical activity and aerobic activity. The magnitude of association becomes significantly larger at the upper quantiles of the body fat mass distribution. Conclusion: Physical activity and sport specialization explained more variance in body composition of physically active young individuals compared to the FTO polymorphism. Effect of interaction of physical activity, in particular aerobic, with the FTO polymorphism on body composition of young athletes was found.
Enzyme immobilization using nanomaterials offers new approaches to enhanced bioelectrochemical performance and is essential for the preparation of bioelectrodes with high reproducibility and low cost. In this report, we describe the development of new three-dimensional (3D) bioelectrodes by immobilizing a "bioink" of glucose oxidase (GOD) in a matrix of reduced graphene oxides (RGOs), polyethylenimine (PEI), and ferrocene carboxylic acid (FcCOOH) on carbon paper (CP). CP with 3D interwoven carbon fibers serves as a solid porous and electronically conducting skeleton, providing large surface areas and space for loading the bioink and diffusion of substrate molecules, respectively. RGO enhances contact between the GOD-matrix and CP, maintaining high conductivity. The composition of the bioink has been systematically optimized. The GOD bioelectrodes show linearly increasing electrocatalytic oxidation current toward glucose concentration up to 48 mM. A hybrid enzymatic biofuel cell equipped with the GOD bioelectrode as a bioanode and a platinum cathode furthermore registers a maximum power density of 5.1 mu W cm(-2) and an open circuit voltage of 0.40 V at 25 degrees C. The new method reported of preparing a bioelectrode by drop-casting the bioink onto the substrate electrode is facile and versatile, with the potential of application also for other enzymatic bioelectrodes.
The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.
NK cells have emerged as promising candidates for cancer immunotherapy, especially due to their ability to fight circulating tumor cells thereby preventing metastases formation. Hence several studies have been performed to generate and expand highly cytotoxic NK cells ex vivo, e.g., by using specific cytokines to upregulate both their proliferation and surface expression of distinct activating receptors. Apart from an enhanced activity, application of NK cells as immunotherapeutic agent further requires sufficient cell numbers and a high purity. All these parameters depend on a variety of different factors including the starting material, additives like cytokines as well as the culture system. Here we analyzed PBMC-derived NK cells of five anonymized healthy donors expanded under specific conditions in an innovative perfusion bioreactor system with respect to their phenotype, IFN gamma production, and cytotoxicity in vitro. Important features of the meander type bioreactors used here are a directed laminar flow of medium and control of relevant process parameters. Cells are cultivated under "steady state" conditions in perfusion mode. Our data demonstrate that expansion of CD3(+) T cell depleted PBMCs in our standardized system generates massive amounts of highly pure (>85%) and potent anticancer active NK cells. These cells express a variety of important receptors driving NK cell recruitment, adhesion as well as activation. More specifically, they express the chemokine receptors CXCR3, CXCR4, and CCR7, the adhesion molecules L-selectin, LFA-1, and VLA-4, the activating receptors NKp30, NKp44, NKp46, NKG2D, DNAM1, and CD16 as well as the death ligands TRAIL and Fas-L. Moreover, the generated NK cells show a strong IFN gamma expression upon cultivation with K562 tumor cells and demonstrate a high cytotoxicity toward leukemic as well as solid tumor cell lines in vitro. Altogether, these characteristics promise a high clinical potency of thus produced NK cells awaiting further evaluation.
The pathophysiological influence of gene-lifestyle interactions on the risk to develop type 2 diabetes (T2D) is currently under intensive research. This systematic review summarizes the evidence for gene-lifestyle interactions regarding T2D incidence. MEDLINE, EMBASE, and Web of Science were systematically searched until 31 January 2019 to identify publication with (a) prospective study design; (b) T2D incidence; (c) gene-diet, gene-physical activity, and gene-weight loss intervention interaction; and (d) population who are healthy or prediabetic. Of 66 eligible publications, 28 reported significant interactions. A variety of different genetic variants and dietary factors were studied. Variants at TCF7L2 were most frequently investigated and showed interactions with fiber and whole grain on T2D incidence. Further gene-diet interactions were reported for, eg, a western dietary pattern with a T2D-GRS, fat and carbohydrate with IRS1 rs2943641, and heme iron with variants of HFE. Physical activity showed interaction with HNF1B, IRS1, PPAR gamma, ADRA2B, SLC2A2, and ABCC8 variants and weight loss interventions with ENPP1, PPAR gamma, ADIPOR2, ADRA2B, TNF alpha, and LIPC variants. However, most findings represent single study findings obtained in European ethnicities. Although some interactions have been reported, their conclusiveness is still low, as most findings were not yet replicated across multiple study populations.
Ecological communities are undeniably diverse, both in terms of the species that compose them as well as the type of interactions that link species to each other. Despite this long recognition of the coexistence of multiple interaction types in nature, little is known about the consequences of this diversity for community functioning. In the ongoing context of global change and increasing species extinction rates, it seems crucial to improve our understanding of the drivers of the relationship between species diversity and ecosystem functioning. Here, using a multispecies dynamical model of ecological communities including various interaction types (e.g. competition for space, predator interference, recruitment facilitation in addition to feeding), we studied the role of the presence and the intensity of these interactions for species diversity, community functioning (biomass and production) and the relationship between diversity and functioning. Taken jointly, the diverse interactions have significant effects on species diversity, whose amplitude and sign depend on the type of interactions involved and their relative abundance. They however consistently increase the slope of the relationship between diversity and functioning, suggesting that species losses might have stronger effects on community functioning than expected when ignoring the diversity of interaction types and focusing on feeding interactions only.
Zinc is an essential trace element, making it crucial to have a reliable biomarker for evaluating an individual’s zinc status. The total serum zinc concentration, which is presently the most commonly used biomarker, is not ideal for this purpose, but a superior alternative is still missing. The free zinc concentration, which describes the fraction of zinc that is only loosely bound and easily exchangeable, has been proposed for this purpose, as it reflects the highly bioavailable part of serum zinc. This report presents a fluorescence-based method for determining the free zinc concentration in human serum samples, using the fluorescent probe Zinpyr-1. The assay has been applied on 154 commercially obtained human serum samples. Measured free zinc concentrations ranged from 0.09 to 0.42 nM with a mean of 0.22 ± 0.05 nM. It did not correlate with age or the total serum concentrations of zinc, manganese, iron or selenium. A negative correlation between the concentration of free zinc and total copper has been seen for sera from females. In addition, the free zinc concentration in sera from females (0.21 ± 0.05 nM) was significantly lower than in males (0.23 ± 0.06 nM). The assay uses a sample volume of less than 10 µL, is rapid and cost-effective and allows us to address questions regarding factors influencing the free serum zinc concentration, its connection with the body’s zinc status, and its suitability as a future biomarker for an individual’s zinc status.
Domestic Bactrian camel (Camelus bactrianus) used to be one of the most important livestock species in Chinese history, as well as the major transport carrier on the ancient Silk Road. However, archeological studies on Chinese C. bactrianus are still limited, and molecular biology research on this species is mainly focused on modern specimens. In this study, we retrieved the complete mitochondrial genome from a C. bactrianus specimen, which was excavated from northwestern China and dated at 1290-1180 cal. Phylogenetic analyses using 18 mitochondrial genomes indicated that the C. bactrianus clade was divided into two maternal lineages. The majority of samples originating from Iran to Japan and Mongolia belong to subclade A1, while our sample together with two Mongolian individuals formed the much smaller subclade A2. Furthermore, the divergence time of these two maternal lineages was estimated as 165 Kya (95% credibility interval 117-222 Kya), this might indicate that several different evolutionary lineages were incorporated into the domestic gene pool during the initial domestication process. Bayesian skyline plot (BSP) analysis a slow increase in female effective population size of C. bactrianus from 5000 years ago, which to the beginning of domestication of C. bactrianus. The present study also revealed that there were extensive exchanges of genetic information among C. bactrianus populations in regions along the Silk Road.
Relationships between different measures of succulence and Crassulacean acid metabolism (CAM; defined here as nocturnal increases in tissue acidity) were investigated in leaves of ten species of Sansevieria under greenhouse conditions. CAM was found in seven of the ten species investigated, and CAM correlated negatively with leaf thickness and leaf hydrenchyma/chlorenchyma ratio. Similarly, CAM correlated negatively with leaf water content, but only when expressed on a fresh mass basis. CAM was not correlated with "mesophyll succulence", but weakly with leaf chlorophyll concentration. These results indicate that CAM is associated more with "all-cell succulence" and not with the amount of leaf hydrenchyma in the genus Sansevieria. The findings of this study emphasize the importance of defining the nature of "leaf succulence" in studies of photosynthetic pathways and leaf morphology. Evidence is also provided that CAM and succulence arose multiple times in the genus Sansevieria.
Distributions of mammals in Southeast Asia: The role of the legacy of climate and species body mass
(2019)
Aim Current species distributions are shaped by present and past biotic and abiotic factors. Here, we assessed whether abiotic factors (habitat availability) in combination with past connectivity and a biotic factor (body mass) can explain the unique distribution pattern of Southeast Asian mammals, which are separated by the enigmatic biogeographic transition zone, the Isthmus of Kra (IoK), for which no strong geophysical barrier exists. Location Southeast Asia. Taxon Mammals. Methods We projected habitat suitability for 125 mammal species using climate data for the present period and for two historic periods: mid-Holocene (6 ka) and last glacial maximum (LGM 21 ka). Next, we employed a phylogenetic linear model to assess how present species distributions were affected by the suitability of areas in these different periods, habitat connectivity during LGM and species body mass. Results Our results show that cooler climate during LGM provided suitable habitat south of IoK for species presently distributed north of IoK (in mainland Indochina). However, the potentially suitable habitat for these Indochinese species did not stretch very far southwards onto the exposed Sunda Shelf. Instead, we found that the emerged landmasses connecting Borneo and Sumatra provided suitable habitat for forest dependent Sundaic species. We show that for species whose current distribution ranges are mainly located in Indochina, the area of the distribution range that is located south of IoK is explained by the suitability of habitat in the past and present in combination with the species body mass. Main conclusions We demonstrate that a strong geophysical barrier may not be necessary for maintaining a biogeographic transition zone for mammals, but that instead a combination of abiotic and biotic factors may suffice.
A yeast expression plasmid was constructed containing a cardenolide biosynthetic module, referred to as CARD II, using the AssemblX toolkit, which enables the assembly of large DNA constructs. The genes cloned into the vector were (a) a Δ5‐3β‐hydroxysteroid dehydrogenase gene from Digitalis lanata, (b) a steroid Δ5‐isomerase gene from Comamonas testosteronii, (c) a mutated steroid‐5β‐reductase gene from Arabidopsis thaliana, and (d) a steroid 21‐hydroxylase gene from Mus musculus. A second plasmid bearing an ADR/ADX fusion gene from Bos taurus was also constructed. A Saccharomyces cerevisiae strain bearing these two plasmids was generated. This strain, termed “CARD II yeast”, was capable of producing 5β‐pregnane‐3β,21‐diol‐20‐one, a central intermediate in 5β‐cardenolide biosynthesis, starting from pregnenolone which was added to the culture medium. Using this approach, five consecutive steps in cardenolide biosynthesis were realized in baker's yeast.
Understanding the drivers underlying disease dynamics is still a major challenge in disease ecology, especially in the case of long-term disease persistence. Even though there is a strong consensus that density-dependent factors play an important role for the spread of diseases, the main drivers are still discussed and, more importantly, might differ between invasion and persistence periods. Here, we analysed long-term outbreak data of classical swine fever, an important disease in both wild boar and livestock, prevalent in the wild boar population from 1993 to 2000 in Mecklenburg-Vorpommern, Germany. We report outbreak characteristics and results from generalized linear mixed models to reveal what factors affected infection risk on both the landscape and the individual level. Spatiotemporal outbreak dynamics showed an initial wave-like spread with high incidence during the invasion period followed by a drop of incidence and an increase in seroprevalence during the persistence period. Velocity of spread increased with time during the first year of outbreak and decreased linearly afterwards, being on average 7.6 km per quarter. Landscape- and individual-level analyses of infection risk indicate contrasting seasonal patterns. During the persistence period, infection risk on the landscape level was highest during autumn and winter seasons, probably related to spatial behaviour such as increased long-distance movements and contacts induced by rutting and escaping movements. In contrast, individual-level infection risk peaked in spring, probably related to the concurrent birth season leading to higher densities, and was significantly higher in piglets than in reproductive animals. Our findings highlight that it is important to investigate both individual- and landscape-level patterns of infection risk to understand long-term persistence of wildlife diseases and to guide respective management actions. Furthermore, we highlight that exploring different temporal aggregation of the data helps to reveal important seasonal patterns, which might be masked otherwise.
Increasing air temperature and atmospheric CO2 levels may affect the distribution of invasive species. Whereas there is wide knowledge on the effect of global change on temperate species, responses of tropical invasive species to these two global change drivers are largely unknown. We conducted a greenhouse experiment on Terminalia catappa L. (Combretaceae), an invasive tree species on Brazilian coastal areas, to evaluate the effects of increased air temperature and CO2 concentration on seed germination and seedling growth on the island of Santa Catarina (Florianopolis, Brazil). Seeds of the invasive tree were subjected to two temperature levels (ambient and +1.6 degrees C) and two CO2 levels (ambient and 650 ppmv) with a factorial design. Increased temperature enhanced germination rate and shortened germination time of T. catappa seeds. It also increased plant height, number of leaves and above-ground biomass. By contrast, increased atmospheric CO2 concentration had no significant effects, and the interaction between temperature and CO2 concentration did not affect any of the measured traits. Terminalia catappa adapts to a relatively broad range of environmental conditions, being able to tolerate cooler temperatures in its invasive range. As T. catappa is native to tropical areas, global warming might favour its establishment along the coast of subtropical South America, while increased CO2 levels seem not to have significant effects on seed germination or seedling growth.
The effects of habitat fragmentation and isolation on plant species richness have been verified for a wide range of anthropogenically fragmented habitats, but there is currently little information about their effects in naturally small and isolated habitats. We tested whether habitat area, heterogeneity, and isolation affect the richness of wetland vascular plant species in kettle holes, i.e., small glacially created wetlands, in an agricultural landscape of 1 km(2) in NE Germany. We compared fragmentation effects with those of forest fragments in the same landscape window. Since wetland and forest species might differ in their tolerance to isolation, and because isolation effects on plant species may be trait dependent, we asked which key life history traits might foster differences in isolation tolerance between wetland and forest plants. We recorded the flora and vegetation types in 83 isolated sites that contained 81 kettle holes and 25 forest fragments. Overall, the number of wetland species increased with increasing area and heterogeneity, i.e., the number of vegetation types, while area was not a surrogate for heterogeneity in these naturally fragmented systems. Isolation did not influence the number of wetland species but decreased the number of forest species. We also found that seeds of wetland species were on average lighter, more persistent and better adapted to epizoochory, e.g., by waterfowl, than seeds of forest species. Therefore, we suggest that wetland species are more tolerant to isolation than forest species due to their higher dispersal potential in space and time, which may counterbalance the negative effects of isolation.
Molybdenum cofactor (Moco) biosynthesis is a complex process that involves the coordinated function of several proteins. In recent years it has become obvious that the availability of iron plays an important role in the biosynthesis of Moco. First, the MoaA protein binds two (4Fe-4S] clusters per monomer. Second, the expression of the moaABCDE and moeAB operons is regulated by FNR, which senses the availability of oxygen via a functional NFe-4S) cluster. Finally, the conversion of cyclic pyranopterin monophosphate to molybdopterin requires the availability of the L-cysteine desulfurase IscS, which is a shared protein with a main role in the assembly of Fe-S clusters. In this report, we investigated the transcriptional regulation of the moaABCDE operon by focusing on its dependence on cellular iron availability. While the abundance of selected molybdoenzymes is largely decreased under iron-limiting conditions, our data show that the regulation of the moaABCDE operon at the level of transcription is only marginally influenced by the availability of iron. Nevertheless, intracellular levels of Moco were decreased under iron-limiting conditions, likely based on an inactive MoaA protein in addition to lower levels of the L-cysteine desulfurase IscS, which simultaneously reduces the sulfur availability for Moco production. IMPORTANCE FNR is a very important transcriptional factor that represents the master switch for the expression of target genes in response to anaerobiosis. Among the FNR-regulated operons in Escherichia coli is the moaABCDE operon, involved in Moco biosynthesis. Molybdoenzymes have essential roles in eukaryotic and prokaryotic organisms. In bacteria, molybdoenzymes are crucial for anaerobic respiration using alternative electron acceptors. This work investigates the connection of iron availability to the biosynthesis of Moco and the production of active molybdoenzymes.
With the onset of the global food crisis, the discussion about the use and misuse of agricultural market interventions regained academic attention. As a result of economies of scale, centralized policy implementation at the regional level has the potential to reduce the budgetary costs of policies. Borrowing from the literature on international unions and international policy coordination, we develop a conceptual framework to analyze when regional policy implementation makes sense. This is the case whenever spill-overs from centralization are large and policy preferences, driven by country-specific characteristics, are homogeneous. Subsequently, we examine the advantageousness of centralized policy implementation for the West African region regarding the most common food security policies. We show that centralization of trade policies and emergency food reserves is beneficial, while buffer stocks, safety net policies, and producer support policies should be implemented at the national level.
A Metabarcoding Analysis of the Mycobiome of Wheat Ears Across a Topographically Heterogeneous Field
(2019)
Aims/hypothesis This study aimed to evaluate associations of height as well as components of height (sitting height and leg length) with risk of type 2 diabetes and to explore to what extent associations are explainable by liver fat and cardiometabolic risk markers. Methods A case-cohort study within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study comprising 26,437 participants who provided blood samples was designed. We randomly selected a subcohort of 2500 individuals (2029 diabetes-free at baseline and with anamnestic, anthropometrical and metabolic data for analysis). Of the 820 incident diabetes cases identified in the full cohort during 7 years of follow-up, 698 remained for analyses after similar exclusions. Results After adjustment for age, potential lifestyle confounders, education and waist circumference, greater height was related to lower diabetes risk (HR per 10 cm, men 0.59 [95% CI 0.47, 0.75] and women 0.67 [0.51, 0.88], respectively). Leg length was related to lower risk among men and women, but only among men if adjusted for total height. Adjustment for liver fat and triacylglycerols, adiponectin and C-reactive protein substantially attenuated associations between height and diabetes risk, particularly among women. Conclusions/interpretation We observed inverse associations between height and risk of type 2 diabetes, which was largely related to leg length among men. The inverse associations may be partly driven by lower liver fat content and a more favourable cardiometabolic profile.
Recent research has shown that many cold-adapted species survived the last glacial maximum (LGM) in northern refugia. Whether this evolutionary history has had consequences for their genetic diversity and adaptive potential remains unknown. We sampled 14 populations of Carex limosa, a sedge specialized to bog ecosystems, along a latitudinal gradient from its Scandinavian core to the southern lowland range-margin in Germany. Using microsatellite and experimental common-garden data, we evaluated the impacts of global climate change along this gradient and assessed the conservation status of the southern marginal populations. Microsatellite data revealed two highly distinct genetic groups and hybrid individuals. In our common-garden experiment, the two groups showed divergent responses to increased nitrogen/phosphorus (N/P) availability, suggesting ecotypic differentiation. Each group formed genetically uniform populations at both northern and southern sampling areas. Mixed populations occurred throughout our sampling area, an area that was entirely glaciated during the LGM. The fragmented distribution implies allopatric divergence at geographically separated refugia that putatively differed in N/P availability. Molecular data and an observed low hybrid fecundity indicate the importance of clonal reproduction for hybrid populations. At the southern range-margin, however, all populations showed effects of clonality, lowered fecundity and low competitiveness, suggesting abiotic and biotic constraints to population persistence.
The genus Shewanella is well known for its genetic diversity, its outstanding respiratory capacity, and its high potential for bioremediation. Here, a novel strain isolated from sediments of the Indian Ocean was characterized. A 16S rRNA analysis indicated that it belongs to the species Shewanella decolorationis. It was named Shewanella decolorationis LDS1. This strain presented an unusual ability to grow efficiently at temperatures from 24 degrees C to 40 degrees C without apparent modifications of its metabolism, as shown by testing respiratory activities or carbon assimilation, and in a wide range of salt concentrations. Moreover, S. decolorationis LDS1 tolerates high chromate concentrations. Indeed, it was able to grow in the presence of 4 mM chromate at 28 degrees C and 3 mM chromate at 40 degrees C. Interestingly, whatever the temperature, when the culture reached the stationary phase, the strain reduced the chromate present in the growth medium. In addition, S. decolorationis LDS1 degrades different toxic dyes, including anthraquinone, triarylmethane, and azo dyes. Thus, compared to Shewanella oneidensis, this strain presented better capacity to cope with various abiotic stresses, particularly at high temperatures. The analysis of genome sequence preliminary data indicated that, in contrast to S. oneidensis and S. decolorationis S12, S. decolorationis LDS1 possesses the phosphorothioate modification machinery that has been described as participating in survival against various abiotic stresses by protecting DNA. We demonstrate that its heterologous production in S. oneidensis allows it to resist higher concentrations of chromate. IMPORTANCE Shewanella species have long been described as interesting microorganisms in regard to their ability to reduce many organic and inorganic compounds, including metals. However, members of the Shewanella genus are often depicted as cold-water microorganisms, although their optimal growth temperature usually ranges from 25 to 28 degrees C under laboratory growth conditions. Shewanella decolorationis LDS1 is highly attractive, since its metabolism allows it to develop efficiently at temperatures from 24 to 40 degrees C, conserving its ability to respire alternative substrates and to reduce toxic compounds such as chromate or toxic dyes. Our results clearly indicate that this novel strain has the potential to be a powerful tool for bioremediation and unveil one of the mechanisms involved in its chromate resistance.
The plasma membrane (PM) is at the interface of plant-pathogen interactions and, thus, many bacterial type-III effector (T3E) proteins target membrane-associated processes to interfere with immunity. The Pseudomonas syringae T3E HopZ1a is a host cell PM-localized effector protein that has several immunity-associated host targets but also activates effector-triggered immunity in resistant backgrounds. Although HopZ1a has been shown to interfere with early defense signaling at the PM, no dedicated PM-associated HopZ1a target protein has been identified until now. Here, we show that HopZ1a interacts with the PM-associated remorin protein NbREM4 from Nicotiana benthamiana in several independent assays. NbREM4 relocalizes to membrane nanodomains after treatment with the bacterial elicitor flg22 and transient overexpression of NbREM4 in N. benthamiana induces the expression of a subset of defense-related genes. We can further show that NbREM4 interacts with the immune-related receptor-like cytoplasmic kinase avrPphB-susceptible 1 (PBS1) and is phosphorylated by PBS1 on several residues in vitro. Thus, we conclude that NbREM4 is associated with early defense signaling at the PM. The possible relevance of the HopZ1a-NbREM4 interaction for HopZ1a virulence and avirulence functions is discussed.
Molecularly imprinted polymers (MIPs) mimic the binding sites of antibodies by substituting the amino acid-scaffold of proteins by synthetic polymers. In this work, the first MIP for the recognition of the diagnostically relevant enzyme butyrylcholinesterase (BuChE) is presented. The MIP was prepared using electropolymerization of the functional monomer o-phenylenediamine and was deposited as a thin film on a glassy carbon electrode by oxidative potentiodynamic polymerization. Rebinding and removal of the template were detected by cyclic voltammetry using ferricyanide as a redox marker. Furthermore, the enzymatic activity of BuChE rebound to the MIP was measured via the anodic oxidation of thiocholine, the reaction product of butyrylthiocholine. The response was linear between 50 pM and 2 nM concentrations of BuChE with a detection limit of 14.7 pM. In addition to the high sensitivity for BuChE, the sensor responded towards pseudo-irreversible inhibitors in the lower mM range.
Mechanisms leading to sympatric speciation are diverse and may build up reproductive isolation. Reproductive isolation among differentiated clades may exist due to genetic incompatibilities, sexual selection, differences in parity mode, reduced post-zygotic survival or reproductive success of hybrids. Here, we test whether differences in parity mode lead to reproductive isolation by investigating introgression in Zootoca vivipara, a lizard species exhibiting oviparous and viviparous reproduction. We measured introgression in transects spanning different viviparous clades, different oviparous subclades, transects containing oviparous and viviparous clades, and transects within the same subclade (control transects). Introgression in transects spanning oviparous and viviparous clades was one order of magnitude smaller than transects spanning the same reproductive mode and no statistical differences existed between transects spanning the same reproductive mode and control transects. Among types of transects, no significant differences existed in genetic and geographic distances, nor number of detected alleles. Moreover, hybrids were detected in all types of transects, showing that parity mode alone does not necessarily lead to complete reproductive isolation, which suggests that reinforcement may play an important role. The evolution of different parity modes together with reinforcement may thus promote reproductive isolation and rapid speciation, potentially explaining why only six of the almost 40,000 vertebrates belonging to groups consisting of viviparous and oviparous species exhibit bimodal reproduction.
The phytohormone auxin influences virtually all aspects of plant growth and development. Auxin transport across membranes is facilitated by, among other proteins, members of the PIN-FORMED (PIN) and the structurally similar PIN-LIKES (PILS) families, which together govern directional cell-to-cell transport and intracellular accumulation of auxin. Canonical PIN proteins, which exhibit a polar localization in the plasma membrane, determine many patterning and directional growth responses. Conversely, the less-studied noncanonical PINs and PILS proteins, which mostly localize to the endoplasmic reticulum, attenuate cellular auxin responses. Here, and in the accompanying poster, we provide a brief summary of current knowledge of the structure, evolution, function and regulation of these auxin transport facilitators.
The movement of microswimmers is often described by active Brownian particle models. Here we introduce a variant of these models with several internal states of the swimmer to describe stochastic strategies for directional swimming such as run and tumble or run and reverse that are used by microorganisms for chemotaxis. The model includes a mechanism to generate a directional bias for chemotaxis and interactions with external fields (e.g., gravity, magnetic field, fluid flow) that impose forces or torques on the swimmer. We show how this modified model can be applied to various scenarios: First, the run and tumble motion of E. coli is used to establish a paradigm for chemotaxis and investigate how it is affected by external forces. Then, we study magneto-aerotaxis in magnetotactic bacteria, which is biased not only by an oxygen gradient towards a preferred concentration, but also by magnetic fields, which exert a torque on an intracellular chain of magnets. We study the competition of magnetic alignment with active reorientation and show that the magnetic orientation can improve chemotaxis and thereby provide an advantage to the bacteria, even at rather large inclination angles of the magnetic field relative to the oxygen gradient, a case reminiscent of what is expected for the bacteria at or close to the equator. The highest gain in chemotactic velocity is obtained for run and tumble with a magnetic field parallel to the gradient, but in general a mechanism for reverse motion is necessary to swim against the magnetic field and a run and reverse strategy is more advantageous in the presence of a magnetic torque. This finding is consistent with observations that the dominant mode of directional changes in magnetotactic bacteria is reversal rather than tumbles. Moreover, it provides guidance for the design of future magnetic biohybrid swimmers. Author summary In this paper, we propose a modified Active Brownian particle model to describe bacterial swimming behavior under the influence of external forces and torques, in particular of a magnetic torque. This type of interaction is particularly important for magnetic biohybrids (i.e. motile bacteria coupled to a synthetic magnetic component) and for magnetotactic bacteria (i.e. bacteria with a natural intracellular magnetic chain), which perform chemotaxis to swim along chemical gradients, but are also directed by an external magnetic field. The model allows us to investigate the benefits and disadvantages of such coupling between two different directionality mechanisms. In particular we show that the magnetic torque can speed chemotaxis up in some conditions, while it can hinder it in other cases. In addition to an understanding of the swimming strategies of naturally magnetotactic organisms, the results may guide the design of future biomedical devices.
Biofilms are complex mixtures of proteins, DNA, and polysaccharides surrounding bacterial communities as protective barriers that can be biochemically modified during the bacterial life cycle. However, their compositional heterogeneity impedes a precise analysis of the contributions of individual matrix components to the biofilm structural organization. To investigate the structural properties of glycan-based biofilms, we analyzed the diffusion dynamics of nanometer-sized objects in matrices of the megadalton-sized anionic polysaccharide, stewartan, the major biofilm component of the plant pathogen, Pantoea stewartii. Fluorescence correlation spectroscopy and single-particle tracking of nanobeads and bacteriophages indicated notable subdiffusive dynamics dependent on probe size and stewartan concentration, in contrast to free diffusion of small molecules. Stewartan enzymatic depolymerization by bacteriophage tailspike proteins rapidly restored unhindered diffusion. We, thus, hypothesize that the glycan polymer stewartan determines the major physicochemical properties of the biofilm, which acts as a selective diffusion barrier for nanometer-sized objects and can be controlled by enzymes.
Bacterial molybdoenzymes are key enzymes involved in the global sulphur, nitrogen and carbon cycles. These enzymes require the insertion of the molybdenum cofactor (Moco) into their active sites and are able to catalyse a large range of redox-reactions. Escherichia coli harbours nineteen different molybdoenzymes that require a tight regulation of their synthesis according to substrate availability, oxygen availability and the cellular concentration of molybdenum and iron. The synthesis and assembly of active molybdoenzymes are regulated at the level of transcription of the structural genes and of translation in addition to the genes involved in Moco biosynthesis. The action of global transcriptional regulators like FNR, NarXL/QP, Fur and ArcA and their roles on the expression of these genes is described in detail. In this review we focus on what is known about the molybdenum- and iron-dependent regulation of molybdoenzyme and Moco biosynthesis genes in the model organism E. coli. The gene regulation in E. coli is compared to two other well studied model organisms Rhodobacter capsulatus and Shewanella oneidensis.
Immunological responses of hibernating mammals are suppressed at low body temperatures, a possible explanation for the devastating effect of the white-nose syndrome on hibernating North American bats. However, European bats seem to cope well with the fungal causative agent of the disease. To better understand the immune response of hibernating bats, especially against fungal pathogens, we challenged European greater mouse-eared bats (Myotis myotis) by inoculating the fungal antigen zymosan. We monitored torpor patterns, immune gene expressions, different aspects of the acute phase response and plasma oxidative status markers, and compared them with sham-injected control animals at 30 min, 48 h and 96 h after inoculation. Torpor patterns, body temperatures, body masses, white blood cell counts, expression of immune genes, reactive oxygen metabolites and non-enzymatic antioxidant capacity did not differ between groups during the experiment. However, zymosan injected bats had significantly higher levels of haptoglobin than the control animals. Our results indicate that hibernating greater mouse-eared bats mount an inflammatory response to a fungal challenge, with only mild to negligible consequences for the energy budget of hibernation. Our study gives a first hint that hibernating European bats may have evolved a hibernation-adjusted immune response in order to balance the trade-off between competent pathogen elimination and a prudent energy-saving regime.
Insectivorous bats consume a large variety of food items. Previous observations of feathers found in feces led to the hypothesis that the birdlike noctule (Nyctalus aviator, Vespertilionidae) could prey on birds. To test the hypothesis, we analyzed fecal samples from six species (Barbastella pacifica, Murina hilgendorfi, Myotis frater, N. aviator, Plecotus sacrimontis, and Vespertilio sinensis) collected from central Hokkaido, Japan, via DNA barcoding. We identified the presence of the Middendorff’s grasshopper warbler (Locustella ochotensis) in the diet of a pregnant individual of N. aviator. All the other samples proved negative regarding bird prey DNA. This is the first time that the consumption of a bird by N. aviator is confirmed with molecular evidence. Our findings add invaluable insight into the diet of this bat and its potentially opportunistic foraging behavior.
In ecological communities, especially the pelagic zones of aquatic ecosystems, certain bodysize ranges are often over-represented compared to others. Community size spectra, the distributions of community biomass over the logarithmic body-mass axis, tend to exhibit regularly spaced local maxima, called "domes", separated by steep troughs. Contrasting established theory, we explain these dome patterns as manifestations of top-down trophic cascades along aquatic food chains. Compiling high quality size-spectrum data and comparing these with a size-spectrum model introduced in this study, we test this theory and develop a detailed picture of the mechanisms by which bottom-up and top-down effects interact to generate dome patterns. Results imply that strong top-down trophic cascades are common in freshwater communities, much more than hitherto demonstrated, and may arise in nutrient rich marine systems as well. Transferring insights from the general theory of nonlinear pattern formation to domes patterns, we provide new interpretations of past lake-manipulation experiments.
Canavanine (CAN) is a nonproteinogenic amino acid synthesized in legumes. In mammalians, as arginine analogue, it is an inhibitor of nitric oxide synthase (NOS) activity. The aim of this study was to investigate the impact of CAN-induced nitric oxide level limitation on the antioxidant system and S-nitrosoglutathione (GSNO) metabolism in roots of tomato seedlings. Treatment with CAN (10 or 50 mu M) for 24-72 h led to restriction in root growth. Arginine-dependent NOS-like activity was almost completely inhibited, demonstrating direct effect of CAN action. CAN increased total antioxidant capacity and the level of sulphydryl groups. Catalase (CAT) and superoxide dismutase (SOD) activity decreased in CAN exposed roots. CAN supplementation resulted in the decrease of transcript levels of genes coding CAT (with the exception of CAT1). Genes coding SOD (except MnSOD and CuSOD) were upregulated by CAN short treatment; prolonged exposition to 50-mu M CAN resulted in downregulation of FeSOD, CuSOD, and SODP-2. Activity of glutathione reductase dropped down after short-term (10-mu M CAN) supplementation, while glutathione peroxidase activity was not affected. Transcript levels of glutathione reductase genes declined in response to CAN. Genes coding glutathione peroxidase were upregulated by 50-mu M CAN, while 10-mu M CAN downregulated GSHPx1. Inhibition of NOS-like activity by CAN resulted in lower GSNO accumulation in root tips. Activity of GSNO reductase was decreased by short-term supplementation with CAN. In contrast, GSNO reductase protein abundance was higher, while transcript levels were slightly altered in roots exposed to CAN. This is the first report on identification of differentially nitrated proteins in response to supplementation with nonproteinogenic amino acid. Among nitrated proteins differentially modified by CAN, seed storage proteins (after short-term CAN treatment) and components of the cellular redox system (after prolonged CAN supplementation) were identified. The findings demonstrate that due to inhibition of NOS-like activity, CAN leads to modification in antioxidant system. Limitation in GSNO level is due to lower nitric oxide formation, while GSNO catabolism is less affected. We demonstrated that monodehydroascorbate reductase, activity of which is inhibited in roots of CAN-treated plants, is the protein preferentially modified by tyrosine nitration.
Sex determination has evolved in a variety of ways and can depend on environmental and genetic signals. A widespread form of genetic sex determination is haplodiploidy, where unfertilized, haploid eggs develop into males and fertilized diploid eggs into females. One of the molecular mechanisms underlying haplodiploidy in Hymenoptera, the large insect order comprising ants, bees, and wasps, is complementary sex determination (CSD). In species with CSD, heterozygosity at one or several loci induces female development. Here, we identify the genomic regions putatively underlying multilocus CSD in the parasitoid wasp Lysiphlebus fabarum using restriction -site associated DNA sequencing. By analyzing segregation patterns at polymorphic sites among 331 diploid males and females, we identify up to four CSD candidate regions, all on different chromosomes. None of the candidate regions feature evidence for homology with the csd gene from the honey bee, the only species in which CSD has been characterized, suggesting that CSD in L. fabarum is regulated via a novel molecular mechanism. Moreover, no homology is shared between the candidate loci, in contrast to the idea that multilocus CSD should emerge from duplications of an ancestral single -locus system. Taken together, our results suggest that the molecular mechanisms underlying CSD in Hymenoptera are not conserved between species, raising the question as to whether CSD may have evolved multiple times independently in the group.
Microorganisms are used for the production of foodstuffs since thousands of years. By now, these biotechnological processes are not restricted to some of the known microorganisms. The possibility to produce enzymes independently from their host organisms extended their range of application. Since then, exploration of new bioresources leads to novel enzymes and peptides applicable for a diverse set of food production processes: peptidases of grain pest beetles are able to hydrolyse gluten and antimicrobial active peptides of insects maybe of use for preservation of food. Examples of our own work depict strategies to identify novel biocatalysts for food biotechnology.
Bacterial pathogens are influenced by signaling molecules including the catecholamines adrenaline and noradrenaline which are host-derived hormones and neurotransmitters. Adrenaline and noradrenaline modulate growth, motility and virulence of bacteria. We show that adrenaline is converted by the pathogen Vibrio cholerae to adrenochrome in the course of respiration, and demonstrate that superoxide produced by the respiratory, Na+ - translocating NADH:quinone oxidoreductase (NQR) acts as electron acceptor in the oxidative conversion of adrenaline to adrenochrome. Adrenochrome stimulates growth of V. cholerae, and triggers specific responses in V. cholerae and in immune cells. We performed a quantitative proteome analysis of V. cholerae grown in minimal medium with glucose as carbon source without catecholamines, or with adrenaline, noradrenaline or adrenochrome. Significant regulation of proteins participating in iron transport and iron homeostasis, in energy metabolism, and in signaling was observed upon exposure to adrenaline, noradrenaline or adrenochrome. On the host side, adrenochrome inhibited lipopolysaccharide-triggered formation of TNF-alpha by THP-1 monocytes, though to a lesser extent than adrenaline. It is proposed that adrenochrome produced from adrenaline by respiring V. cholerae functions as effector molecule in pathogen-host interaction.
Negative phototactic response to UVR in three cosmopolitan rotifers: a video analysis approach
(2019)
Background
Organisms are expected to respond to changing environmental conditions through local adaptation, range shift or local extinction. The process of local adaptation can occur by genetic changes or phenotypic plasticity, and becomes especially relevant when dispersal abilities or possibilities are somehow constrained. For genetic changes to occur, mutations are the ultimate source of variation and the mutation rate in terms of a mutator locus can be subject to evolutionary change. Recent findings suggest that the evolution of the mutation rate in a sexual species can advance invasion speed and promote adaptation to novel environmental conditions. Following this idea, this work uses an individual-based model approach to investigate if the mutation rate can also evolve in a sexual species experiencing different conditions of directional climate change, under different scenarios of colored stochastic environmental noise, probability of recombination and of beneficial mutations. The color of the noise mimicked investigating the evolutionary dynamics of the mutation rate in different habitats.
Results
The results suggest that the mutation rate in a sexual species experiencing directional climate change scenarios can evolve and reach relatively high values mainly under conditions of complete linkage of the mutator locus and the adaptation locus. In contrast, when they are unlinked, the mutation rate can slightly increase only under scenarios where at least 50% of arising mutations are beneficial and the rate of environmental change is relatively fast. This result is robust under different scenarios of stochastic environmental noise, which supports the observation of no systematic variation in the mutation rate among organisms experiencing different habitats.
Conclusions
Given that 50% beneficial mutations may be an unrealistic assumption, and that recombination is ubiquitous in sexual species, the evolution of an elevated mutation rate in a sexual species experiencing directional climate change might be rather unlikely. Furthermore, when the percentage of beneficial mutations and the population size are small, sexual species (especially multicellular ones) producing few offspring may be expected to react to changing environments not by adaptive genetic change, but mainly through plasticity. Without the ability for a plastic response, such species may become – at least locally – extinct.
The complete mitochondrial genome of a European fire-bellied toad (Bombina bombina) from Germany
(2019)
The European fire-bellied toad, Bombina bombina, is a small aquatic toad belonging to the family Bombinatoridae. The species is native to the lowlands of Central and Eastern Europe, where population numbers have been in decline in recent past decades. Here, we present the first complete mitochondrial genome of the endangered European fire-bellied toad from Northern Germany recovered using iterative mapping. Phylogenetic analyses including other representatives of the Bombinatoridae placed our German specimen as sister to a Polish B. bombina sequence with high support. This finding is congruent with the postulated Pleistocene history of the species. Our complete mitochondrial genome represents an important resource for further population analysis of the European fire-bellied toad, especially those found within Germany.
The importance of cryptic diversity in rotifers is well understood regarding its ecological consequences, but there remains an in depth comprehension of the underlying molecular mechanisms and forces driving speciation. Temperature has been found several times to affect species spatio-temporal distribution and organisms’ performance, but we lack information on the mechanisms that provide thermal tolerance to rotifers. High cryptic diversity was found recently in the freshwater rotifer “Brachionus calyciflorus”, showing that the complex comprises at least four species: B. calyciflorus sensu stricto (s.s.), B. fernandoi, B. dorcas, and B. elevatus. The temporal succession among species which have been observed in sympatry led to the idea that temperature might play a crucial role in species differentiation.
The central aim of this study was to unravel differences in thermal tolerance between species of the former B. calyciflorus species complex by comparing phenotypic and gene expression responses. More specifically, I used the critical maximum temperature as a proxy for inter-species differences in heat-tolerance; this was modeled as a bi-dimensional phenotypic trait taking into consideration the intention and the duration of heat stress. Significant differences on heat-tolerance between species were detected, with B. calyciflorus s.s. being able to tolerate higher temperatures than B. fernandoi.
Based on evidence of within species neutral genetic variation, I further examined adaptive genetic variability within two different mtDNA lineages of the heat tolerant B. calyciflorus s.s. to identify SNPs and genes under selection that might reflect their adaptive history. These analyses did not reveal adaptive genetic variation related to heat, however, they show putatively adaptive genetic variation which may reflect local adaptation. Functional enrichment of putatively positively selected genes revealed signals of adaptation in genes related to “lipid metabolism”, “xenobiotics biodegradation and metabolism” and “sensory system”, comprising candidate genes which can be utilized in studies on local adaptation. An absence of genetically-based differences in thermal adaptation between the two mtDNA lineages, together with our knowledge that B. calyciflorus s.s. can withstand a broad range of temperatures, led to the idea to further investigate shared transcriptomic responses to long-term exposure to high and low temperatures regimes. With this, I identified candidate genes that are involved in the response to temperature imposed stress. Lastly, I used comparative transcriptomics to examine responses to imposed heat-stress in heat-tolerant and heat-sensitive Brachionus species. I found considerably different patterns of gene expression in the two species. Most striking are patterns of expression regarding the heat shock proteins (hsps) between the two species. In the heat-tolerant, B. calyciflorus s.s., significant up-regulation of hsps at low temperatures was indicative of a stress response at the cooler end of the temperature regimes tested here. In contrast, in the heat-sensitive B. fernandoi, hsps generally exhibited up-regulation of these genes along with rising temperatures. Overall, identification of differences in expression of genes suggests suppression of protein biosynthesis to be a mechanism to increase thermal tolerance. Observed patterns in population growth are correlated with the hsp gene expression differences, indicating that this physiological stress response is indeed related to phenotypic life history performance.
Global warming has profound effects on plant growth and fitness. Plants have evolved sophisticated epigenetic machinery to respond quickly to heat, and exhibit transgenerational memory of the heat-induced release of post-transcriptional gene silencing (PTGS). However, how thermomemory is transmitted to progeny and the physiological relevance are elusive. Here we show that heat-induced HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2) directly activates the H3K27me3 demethylase RELATIVE OF EARLY FLOWERING 6 (REF6), which in turn derepresses HSFA2. REF6 and HSFA2 establish a heritable feedback loop, and activate an E3 ubiquitin ligase, SUPPRESSOR OF GENE SILENCING 3 (SGS3)-INTERACTING PROTEIN 1 (SGIP1). SGIP1-mediated SGS3 degradation leads to inhibited biosynthesis of trans-acting siRNA (tasiRNA). The REF6-HSFA2 loop and reduced tasiRNA converge to release HEAT-INDUCED TAS1 TARGET 5 (HTT5), which drives early flowering but attenuates immunity. Thus, heat induces transmitted phenotypes via a coordinated epigenetic network involving histone demethylases, transcription factors, and tasiRNAs, ensuring reproductive success and transgenerational stress adaptation.