Expression of subregion and haplotype preference for H-2Kk restricted cytotoxic T-cell responses in vivo and at the level of the precursor frequencies

Several strains of mice bearing the H-2K^k allele were found to generate in vivo strong CTL responses against TNP-haptenated syngeneic cells, while several other strains of mice were found to generate comparably weak or no responses. C3H × DBA/2)F1 mice (H-2^k × H-2^d) and A/J mice with the recombinant haplotype $\text{H-2}{}^{\mathrm{<mtext>k</mtext><mtext>d</mtext>}}$ generated CTL responses in vivo that were completely restricted toward the H-2^k haplotype or the K end of the $\text{H-2}{}^{\mathrm{<mtext>k</mtext><mtext>d</mtext>}}$ haplotype, respectively. The CTL activity of C3H × DBA/2)F1 and A/J mice against haptenated H-2^k targets was found to be more than 25-fold higher than the CTL activity on H-2^d targets. The CTL responses in vitro under macroculture conditions showed, on the other hand, only a 3- to 6-fold higher cytotoxic activity against the haptenated H-2^k targets as compared with haptenated allogeneic or H-2^d targets; and limiting dilution experiments in microcultures revealed that the CTL precursor frequencies were only 2- to 3-fold smaller for TNP-haptenated H-2^d or haptenated allogeneic targets than for haptenated H-2^k target cells. This indicated that sufficient numbers of H-2^d-restricted and allorestricted CTL precursors were actually present in these strains, but did not develop detectable cytotoxic activity in vivo. The exceptional property of the H-2^k haplotype is, therefore, only partly determined by a difference in the CTL precursor frequencies, and to the larger extent determined at the level of the activation of the CTL response.     

Salmonella typhimurium mutants with reduced levels of transfer ribonucleic acid-inhibitable endodeoxyribonucleolytic activity.

Two methods of mutagenesis, chemical alkylation and insertion of the tetracycline resistance transposon Tn10, were used to generate mutants of Salmonella typhimurium which had reduced levels of endodeoxyribonucleolytic activity. The chemically induced mutations defined a locus, endA, which was cotransduced with serA at a low frequency and with metK at a high frequency. Three-factor crosses revealed that metK was between serA and endA. The major endodeoxyribonucleolytic activity in crude extracts of s. typhimurium was similar to the activity of Escherichia coli endonuclease I. A Tn10 insertion mutation of endA resulted in the most severe loss of endodeoxyribonucleolytic activity among the endA alleles studied. Two of the chemically induced mutations resulted in activities which were more thermolabile than the wild-type activity.     

Process‐based functions for seed retention on animals: a test of improved descriptions of dispersal using multiple data sets

Studies of external seed transport on animals usually assume that the probability of detachment is constant, so that seed retention should show a simple exponential relationship with time. This assumption has not been tested explicitly, and may lead to inaccurate representation of long distance seed dispersal by animals. We test the assumption by comparing the fit to empirical data of simple, two‐parameter functions. Fifty‐two data sets were obtained from five published studies, describing seed retention of 32 plant species on sheep, cattle, deer, goats and mice. Model selection suggested a simple exponential function was adequate for data sets in which seed retention was followed for short periods ( <48 h). The data gathered over longer periods (49–219 days) were best described by the power exponential function, a form of the stretched exponential which allows a changing dropping rate. In these cases the power exponential showed that seed dropping rate decreased with time, suggesting that seeds vary in attachment, with some seeds becoming deeply buried or wound up in the animal's coat. Comparison of fitted parameters across all the data sets also confirmed that seeds with adhesive structures have lower dropping rates than those without. We conclude that the seed dropping rate often changes with time during external transport on animals and that the power exponential is an effective function to describe this change. We advise that, to analyse seed dropping rates adequately, retention should be measured over reasonable time periods – until most seeds are dropped – and both the simple and power exponential functions should be fitted to the resulting data. To increase its utility, we provide functions describing the seed dropping rate and the dispersal kernel resulting from the power exponential relationship.     

Growth and resilience responses of Scots pine to extreme droughts across Europe depend on predrought growth conditions

Global climate change is expected to further raise the frequency and severity of extreme events, such as droughts. The effects of extreme droughts on trees are difficult to disentangle given the inherent complexity of drought events (frequency, severity, duration, and timing during the growing season). Besides, drought effects might be modulated by trees’ phenotypic variability, which is, in turn, affected by long‐term local selective pressures and management legacies. Here we investigated the magnitude and the temporal changes of tree‐level resilience (i.e., resistance, recovery, and resilience) to extreme droughts. Moreover, we assessed the tree‐, site‐, and drought‐related factors and their interactions driving the tree‐level resilience to extreme droughts. We used a tree‐ring network of the widely distributed Scots pine (Pinus sylvestris) along a 2,800 km latitudinal gradient from southern Spain to northern Germany. We found that the resilience to extreme drought decreased in mid‐elevation and low productivity sites from 1980–1999 to 2000–2011 likely due to more frequent and severe droughts in the later period. Our study showed that the impact of drought on tree‐level resilience was not dependent on its latitudinal location, but rather on the type of sites trees were growing at and on their growth performances (i.e., magnitude and variability of growth) during the predrought period. We found significant interactive effects between drought duration and tree growth prior to drought, suggesting that Scots pine trees with higher magnitude and variability of growth in the long term are more vulnerable to long and severe droughts. Moreover, our results indicate that Scots pine trees that experienced more frequent droughts over the long‐term were less resistant to extreme droughts. We, therefore, conclude that the physiological resilience to extreme droughts might be constrained by their growth prior to drought, and that more frequent and longer drought periods may overstrain their potential for acclimation.     

The effectiveness of flower strips and hedgerows on pest control,pollination services and crop yield: a quantitative synthesis

Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.     

How to measure,report and verify soil carbon change to realize the potential of soil carbon sequestration for atmospheric greenhouse gas removal

There is growing international interest in better managing soils to increase soil organic carbon (SOC) content to contribute to climate change mitigation, to enhance resilience to climate change and to underpin food security, through initiatives such as international ‘4p1000’ initiative and the FAO's Global assessment of SOC sequestration potential (GSOCseq) programme. Since SOC content of soils cannot be easily measured, a key barrier to implementing programmes to increase SOC at large scale, is the need for credible and reliable measurement/monitoring, reporting and verification (MRV) platforms, both for national reporting and for emissions trading. Without such platforms, investments could be considered risky. In this paper, we review methods and challenges of measuring SOC change directly in soils, before examining some recent novel developments that show promise for quantifying SOC. We describe how repeat soil surveys are used to estimate changes in SOC over time, and how long‐term experiments and space‐for‐time substitution sites can serve as sources of knowledge and can be used to test models, and as potential benchmark sites in global frameworks to estimate SOC change. We briefly consider models that can be used to simulate and project change in SOC and examine the MRV platforms for SOC change already in use in various countries/regions. In the final section, we bring together the various components described in this review, to describe a new vision for a global framework for MRV of SOC change, to support national and international initiatives seeking to effect change in the way we manage our soils.     

Comment to “Marginal and non-marginal approaches in characterization: how context and scale affect the selection of an adequate characterization factor. The AWARE model example”

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