Future emergence of new ecosystems caused by glacial retreat

Glacier shrinkage and the development of post-glacial ecosystems related to anthropogenic climate change are some of the fastest ongoing ecosystem shifts, with marked ecological and societal cascading consequences1-6. Yet, no complete spatial analysis exists, to our knowledge, to quantify or anticipate this important changeover7,8. Here we show that by 2100, the decline of all glaciers outside the Antarctic and Greenland ice sheets may produce new terrestrial, marine and freshwater ecosystems over an area ranging from the size of Nepal (149,000 ± 55,000 km2) to that of Finland (339,000  ±  99,000  km2). Our analysis shows that the loss of glacier area will range from 22 ± 8% to 51 ± 15%, depending on the climate scenario. In deglaciated areas, the emerging ecosystems will be characterized by extreme to mild ecological conditions, offering refuge for cold-adapted species or favouring primary productivity and generalist species. Exploring the future of glacierized areas highlights the importance of glaciers and emerging post-glacial ecosystems in the face of climate change, biodiversity loss and freshwater scarcity. We find that less than half of glacial areas are located in protected areas. Echoing the recent United Nations resolution declaring 2025 as the International Year of Glaciers' Preservation9 and the Global Biodiversity Framework10, we emphasize the need to urgently and simultaneously enhance climate-change mitigation and the in situ protection of these ecosystems to secure their existence, functioning and values.

Water-soluble carbohydrates in Patzkea paniculata (L.): a plant strategy to tolerate snowpack reduction and spring drought in subalpine grasslands

In subalpine grasslands of the central French Alps, cessation of traditional mowing promotes dominance of Patzkea paniculata (L.) G.H.Loos (Poaceae) tussocks, with high biomass but low fodder quality. Mowing limits P. paniculata abundance through the depletion of its water-soluble carbohydrate (WSC) reserves, which sustain early spring growth initiation. However, the effectiveness of mowing effects is modulated by grassland functional composition, fertilization and climate change, as WSC compounds, and notably fructans, support plant physiological responses to climate stresses such as drought or frost. To characterize the mechanisms underpinning the control of P. paniculata under global change, we tested the effects of climate manipulation (combined snow removal and drought) and management (cutting and fertilization) alone or in combination on P. paniculata WSC storage in assembled grassland communities of varying functional composition. Management and climate treatments individually decreased seasonal fructan storage, with neither additive nor synergic effects between them, primarily due to the dominance of management over climate effects. Fructan amounts were higher in individuals growing in unmanaged exploitative communities compared to unmanaged conservative communities, regardless of climate treatments, but management overrode these differences. Our findings suggest that reduction by combined snow removal and drought of P. paniculata carbon allocation to WSC storage may similarly limit its dominance to that in current mowing practices.

Contribution of above- and below-ground plant traits to the structure and function of grassland soil microbial communities

BACKGROUND AND AIMS

Abiotic properties of soil are known to be major drivers of the microbial community within it. Our understanding of how soil microbial properties are related to the functional structure and diversity of plant communities, however, is limited and largely restricted to above-ground plant traits, with the role of below-ground traits being poorly understood. This study investigated the relative contributions of soil abiotic properties and plant traits, both above-ground and below-ground, to variations in microbial processes involved in grassland nitrogen turnover.

METHODS

In mountain grasslands distributed across three European sites, a correlative approach was used to examine the role of a large range of plant functional traits and soil abiotic factors on microbial variables, including gene abundance of nitrifiers and denitrifiers and their potential activities.

KEY RESULTS

Direct effects of soil abiotic parameters were found to have the most significant influence on the microbial groups investigated. Indirect pathways via plant functional traits contributed substantially to explaining the relative abundance of fungi and bacteria and gene abundances of the investigated microbial communities, while they explained little of the variance in microbial activities. Gene abundances of nitrifiers and denitrifiers were most strongly related to below-ground plant traits, suggesting that they were the most relevant traits for explaining variation in community structure and abundances of soil microbes involved in nitrification and denitrification.

CONCLUSIONS

The results suggest that consideration of plant traits, and especially below-ground traits, increases our ability to describe variation in the abundances and the functional characteristics of microbial communities in grassland soils.

Microbes on the cliff: alpine cushion plants structure bacterial and fungal communities

Plants affect the spatial distribution of soil microorganisms, but the influence of the local abiotic context is poorly documented. We investigated the effect of a single plant species, the cushion plant Silene acaulis, on habitat conditions, and microbial community. We collected soil from inside (In) and outside (Out) of the cushions on calcareous and siliceous cliffs in the French Alps along an elevation gradient (2,000–3,000 masl). The composition of the microbial communities was assessed by Capillary-Electrophoresis Single Strand Conformation Polymorphism (CE-SSCP). Univariate and multivariate analyses were conducted to characterize the response of the microbial beta-diversity to soil parameters (total C, total N, soil water content, N-NH4+,N-NO3-, and pH). Cushions affected the microbial communities, modifying soil properties. The fungal and bacterial communities did not respond to the same abiotic factors. Outside the cushions, the bacterial communities were strongly influenced by bedrock. Inside the cushions, the bacterial communities from both types of bedrock were highly similar, due to the smaller pH differences than in open areas. By contrast, the fungal communities were equally variable inside and outside of the cushions. Outside the cushions, the fungal communities responded weakly to soil pH. Inside the cushions, the fungal communities varied strongly with bedrock and elevation as well as increases in soil nutrients and water content. Furthermore, the dissimilarities in the microbial communities between the In and Out habitats increased with increasing habitat modification and environmental stress. Our results indicate that cushions act as a selective force that counteracts the influence of the bedrock and the resource limitations on the bacterial and fungal communities by buffering soil pH and enhancing soil nutrients. Cushion plants structure microbial communities, and this effect increases in stressful, acidic and nutrient-limited environments.

15N-Nitrate signature in low-order streams: effects of land cover and agricultural practices

Many studies have shown that intensive agricultural practices significantly increase the nitrogen concentration of stream surface waters, but it remains difficult to identify, quantify, and differentiate between terrestrial and in-stream sources or sinks of nitrogen, and rates of transformation. In this study we used the delta15N-NO3 signature in a watershed dominated by agriculture as an integrating marker to trace (1) the effects of the land cover and agricultural practices on stream-water N concentration in the upstream area of the hydrographic network, (2) influence of the in-stream processes on the NO3-N loads at the reach scale (100 m and 1000 m long), and (3) changes in delta15N-NO3 signature with increasing stream order (from first to third order). This study suggests that land cover and fertilization practices were the major determinants of delta15N-NO3 signature in first-order streams. NO3-N loads and delta15N-NO3 signature increased with fertilization intensity. Small changes in delta15N-NO3 signature and minor inputs of groundwater were observed along both types of reaches, suggesting the NO3-N load was slightly influenced by in-stream processes. The variability of NO3-N concentrations and delta15N signature decreased with increasing stream order, and the delta15N signature was positively correlated with watershed areas devoted to crops, supporting a dominant effect of agriculture compared to the effect of in-stream N processing. Consequently, land cover and fertilization practices are integrated in the natural isotopic signal at the third-order stream scale. The GIS analysis of the land cover coupled with natural-abundance isotope signature (delta15N) represents a potential tool to evaluate the effects of agricultural practices in rural catchments and the consequences of future changes in management policies at the regional scale.

KLN-5: a safe monocationic lipophosphoramide to transfect efficiently haematopoietic cell lines and human CD34+ cells

The safe and efficient delivery of nucleic acids into haematopoietic stem cells (HSCs) has a wide range of therapeutic applications. Although viruses are being used in most clinical trials owing to their high transfection efficacy, recent results highlight many concerns about their use. Synthetic transfection reagents, in contrast, have the advantage of being safe and easy to manage while their low transfection efficiency remains a hurdle that needs to be addressed before they can be widely used. Using information on transfection mechanisms, a new family of monocationic lipids called lipophosphoramides was synthesized. Their efficiency to transfer genes into haematopoietic cell lines (K562, Jurkat and Daudi) and CD34+ cells was assessed. In this study, we report that one of these new compounds, KLN-5, leads to more efficient transfection activity than one of our previously most efficient reagents (EG-308) and the commercially available monocationic lipids (DC-CHOL and DOTAP/DOPE) (P<0.05). In addition, only a slight toxicity related to the chemical structure of the new compounds is observed. Moreover, we show that KLN-5 can successfully carry the transgene into haematopoietic progenitor cells (CD34+). These results demonstrate that synthetic transfection reagents represent a viable alternative to viruses and could have potential practical utility in a number of applications.

Biodistribution study of phosphonolipids: a class of non-viral vectors efficient in mice lung-directed gene transfer

BACKGROUND

A multitude of cationic lipids have been synthesized since they were first proposed for use in gene therapy. Cationic lipids are able to efficiently transfect cells both in vitro and in vivo. Whereas most research groups have focused their investigations on the toxicity of these molecules, and on the location of expression of the DNA transferred by these vectors, little has been done to determine their biodistribution and elimination pathways. Our group has developed a family of cationic lipids termed phosphonolipids. Following a large in vitro screening experiment, we have selected several molecules for in vivo testing, with some of these phosphonolipids forming lipoplexes efficient in transfecting mouse lungs. It was thus of interest to study their fate after intravenous injection.

METHODS

The respective biodistributions of both the GLB43 phosphonolipid and plasmid DNA were investigated and compared with DNA expression sites. Using the optimal conditions determined for phosphonolipids, we followed the gene transfer agent and plasmid DNA distributions versus time by radiolabeling them with (14)C and (32)P, respectively. Otherwise, we performed imaging by radiolabeling plasmid DNA with (99m)Tc.

RESULTS

The lipoplexes appear to be directly located in the lung after administration. Secondly, the plasmid is released mainly into the lungs and the phosphonolipid vector is rapidly degraded. The hydrophilic moiety of the phosphonolipid is eliminated in the urine, as is the free plasmid.

CONCLUSIONS

This study reveals that there are slight differences in the observed results depending on the technique used to label the DNA; secondly, results show that the residence time of phosphonolipids in the mouse body is related to the DNA binding time.

Cationic phosphonolipids as nonviral gene transfer agents in the lungs of mice

With the aim of developing new gene transfer tools for treating CF with gene therapy, we have synthesized a novel family of molecules named cationic phosphonolipids. The most efficient among them were selected by in vitro screening to compare their activities in vivo in mouse lungs. We used a reporter gene whose activity was measured cytofluorimetrically (FACS-Gal assay) and by means of a chemiluminescence technique. These tests allowed us to identify the percentage of transfected cells and to quantify total beta-galactosidase in the lungs. This enabled us to identify two molecules, significantly efficient in comparison with DNA alone: GLB73 (p = 0.0015) and GLB253 (p = 0.007). Their use resulted in a time lag between transfection and maximum efficiency: maximum efficiency was observed 4 days after transfection with GLB73, whereas it was noticeable only on day 7 with GLB253. Moreover, from toxicity studies carried out in vivo, GLB73 seems to be nontoxic. In vivo results were correlated with in vitro results obtained with CF epithelial cell lines. Consequently, GLB73 is a potential candidate for phase I clinical trials in humans.

Cationic phosphonolipids as non viral vectors for DNA transfection in hematopoietic cell lines and CD34+ cells

The ability to transfer genes into a hematopoietic stem cell and to achieve regulation of their expression in lymphoid or myeloid lineages should open many new therapeutic opportunities. Besides gene transfer mediated by virus vectors like retrovirus or adenovirus, non viral systems have the theoretical advantage of being safe and easy to manage. We developed a new family of cationic lipids called phosphonolipids, synthesized 24 new molecules, and then in a first step we tested their potential to transfer genes in human hematopoietic cell lines (K562 and TF1). A LacZ plasmid under the control of a strong viral promoter was used as a reporter gene and a FACS-Gal assay and a quantitative test CPRG assay evaluated the beta gal expression. The targeted cells were analyzed 48 hours after transfection. The present work shows that seven novel molecules display a high transfer efficiency. One of them is nine-fold more efficient than the commercially available cationic lipids. The results obtained ex vivo on CD34 cells with the FACS-Gal assay show that at day 10 after transfection, 45 percent of cells are expressing gal.