Plant Performance in a Warmer World: General Responses of Plants from Cold, Northern Biomes and the Importance of Winter and Spring Events

During the past three decades the Earth has warmed with a rate unprecedented during the past 1000 years. There is already ample evidence that this fast climate warming has affected a broad range of organisms, including plants. Plants from high-latitude and high-altitude sites (‘cold biomes’) are especially sensitive to climate warming. In this paper we (1) review the response in the phenology of plants, changes in their range and distribution, soil nutrient availability, and the effects on the structure and dynamics of plant communities for cold, northern biomes; and (2) we show, by using data from an ongoing snow and temperature manipulation experiment in northern Sweden, that also winter and spring events have a profound influence on plant performance. Both long-term phenological data sets, experimental warming studies (performed in summer or year-round), natural gradient studies and satellite images show that key phenological events are responsive to temperature increases and that recent climate warming does indeed lead to changes in plant phenology. However, data from a warming and snow manipulation study that we are conducting in northern Sweden show that plants respond differently to the various climatic scenarios that we had imposed on these species and that especially winter and spring events have a profound impact. This indicates that it is necessary to include several scenarios of both summer and winter climate change in experimental climate change studies, and that we need detailed projections of future climate at a regional scale to be able to assess their impacts on natural ecosystems. There is also ample evidence that the range shift of herbs and shrubs to more northern regions is for the vast majority of species mainly caused by changes in the climate. This is in line with the observed ‘up-greening’ of northern tundra sites. These rapid northern shifts in distribution of plants as a result of climate warming may have substantial consequences for the structure and dynamics of high-latitude ecosystems. An analysis of warming studies at 9 tundra sites shows that heating during at least 3 years increased net N-mineralization from 0.32±0.31 (SE) g N m⁻² yr⁻¹ in the controls to 0.53±0.31 (SE) g N m⁻² yr⁻¹ in the heated plots (p<0.05), an increase of about 70%. Thus, warming leads to higher N availability in high-latitude northern tundra sites, but the variability is substantial. Higher nutrient availability affects in turn the species composition of high-latitude sites, which has important consequences for the carbon and water balance of these systems.     

Moss Responses to Elevated CO2 and Variation in Hydrology in a Temperate Lowland Peatland

We studied the effects of elevated CO₂ (180–200 ppmv above ambient) on growth and chemistry of three moss species (Sphagnum palustre, S. recurvum and Polytrichum commune) in a lowland peatland in the Netherlands. Thereto, we conducted both a greenhouse experiment with both Sphagnum species and a field experiment with all three species using MiniFACE (Free Air CO₂ Enrichment) technology during 3 years. The greenhouse experiment showed that Sphagnum growth was stimulated by elevated CO₂ in the short term, but that in the longer term (≥1 year) growth was probably inhibited by low water tables and/or down-regulation of photosynthesis. In the field experiment, we did not find significant changes in moss abundance in response to elevated CO₂, although CO₂ enrichment appeared to reduce S. recurvum abundance. Both Sphagnum species showed stronger responses to spatial variation in hydrology than to increased atmospheric CO₂ concentrations. Polytrichum was insensitive to changes in hydrology. Apart from the confounding effects of hydrology, the relative lack of growth response of the moss species may also have been due to the relatively small increase in assimilated CO₂ as achieved by the experimentally added CO₂. We calculated that the added CO₂ contributed at most 32% to the carbon assimilation of the mosses, while our estimates based on stable C isotope data even suggest lower contributions for Sphagnum (24–27%). Chemical analyses of the mosses showed only small elevated CO₂ effects on living tissue N concentration and C/N ratio of the mosses, but the C/N ratio of Polytrichum was substantially lower than those of the Sphagnum species. Continuing expansion of Polytrichum at the expense of Sphagnum could reduce the C sink function of this lowland Sphagnum peatland, and similar ones elsewhere, as litter decomposition rates would probably be enhanced. Such a reduction in sink function would be driven mostly by increased atmospheric N deposition, water table regulation for agricultural purposes and land management to preserve the early successional stage (mowing, tree and shrub removal), since these anthropogenic factors will probably exert a greater control on competition between Polytrichum and Sphagnum than increased atmospheric CO₂ concentrations.     

Effect of weight loss and exercise on angiogenic factors in the circulation and in adipose tissue in obese subjects

Background:

Vascular growth is a prerequisite for adipose tissue (AT) development and expansion. Some AT cytokines and hormones have effects on vascular development, like vascular endothelial growth factor (VEGF‐A), angiopoietin (ANG‐1), ANG‐2 and angiopoietin‐like protein‐4 (ANGPTL‐4).

Methods:

In this study, the independent and combined effects of diet‐induced weight loss and exercise on AT gene expression and proteins levels of those angiogenic factors were investigated. Seventy‐nine obese males and females were randomized to: 1. Exercise‐only (EXO; 12‐weeks exercise without diet‐restriction), 2. Hypocaloric diet (DIO; 8‐weeks very low energy diet (VLED) + 4‐weeks weight maintenance diet) and 3. Hypocaloric diet and exercise (DEX; 8‐weeks VLED + 4‐weeks weight maintenance diet combined with exercise throughout the 12 weeks). Blood samples and fat biopsies were taken before and after the intervention.

Results:

Weight loss was 3.5 kg in the EXO group and 12.3 kg in the DIO and DEX groups. VEGF‐A protein was non‐significantly reduced in the weight loss groups. ANG‐1 protein levels were significantly reduced 22‐25% after all three interventions (P < 0.01). The ANG‐1/ANG‐2 ratio was also decreased in all three groups (P < 0.05) by 27‐38%. ANGPTL‐4 was increased in the EXO group (15%, P < 0.05) and 9% (P < 0.05) in the DIO group. VEGF‐A, ANG‐1, and ANGPTL‐4 were all expressed in human AT, but only ANGPTL‐4 was influenced by the interventions.

Conclusions:

Our data show that serum VEGF‐A, ANG‐1, ANG‐2, and ANGPTL‐4 levels are influenced by weight changes, indicating the involvement of these factors in the obese state. Moreover, it was found that weight loss generally was associated with a reduced angiogenic activity in the circulation.     

Sensitive fluorescence in situ hybridization signal detection in maize using directly labeled probes produced by high concentration DNA polymerase nick translation

The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30?kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected.     

Modulation of Protease Activated Receptor 1 Influences Human Metapneumovirus Disease Severity in a Mouse Model

Human metapneumovirus (hMPV) infection causes acute respiratory tract infections (RTI) which can result in hospitalization of both children and adults. To date, no antiviral or vaccine is available for this common viral infection. Immunomodulators could represent an interesting strategy for the treatment of severe viral infection. Recently, the role of protease-activated receptors (PAR) in inflammation, coagulation and infection processes has been of growing interest. Herein, the effects of a PAR1 agonist and a PAR1 antagonist on hMPV infection were investigated in BALB/c mice. Intranasal administration of the PAR1 agonist resulted in increased weight loss and mortality of infected mice. Conversely, the PAR1 antagonist was beneficial to hMPV infection by decreasing weight loss and clinical signs and by significantly reducing pulmonary inflammation, pro-inflammatory cytokine levels (including IL-6, KC and MCP-1) and recruitment of immune cells to the lungs. In addition, a significant reduction in pulmonary viral titers was also observed in the lungs of PAR1 antagonist-treated mice. Despite no apparent direct effect on virus replication during in vitro experiments, an important role for PAR1 in the regulation of furin expression in the lungs was shown for the first time. Further experiments indicated that the hMPV fusion protein can be cleaved by furin thus suggesting that PAR1 could have an effect on viral infectivity in addition to its immunomodulatory properties. Thus, inhibition of PAR1 by selected antagonists could represent an interesting strategy for decreasing the severity of paramyxovirus infections.     

Meander: visually exploring the structural variome using space-filling curves

The introduction of next generation sequencing methods in genome studies has made it possible to shift research from a gene-centric approach to a genome wide view. Although methods and tools to detect single nucleotide polymorphisms are becoming more mature, methods to identify and visualize structural variation (SV) are still in their infancy. Most genome browsers can only compare a given sequence to a reference genome; therefore, direct comparison of multiple individuals still remains a challenge. Therefore, the implementation of efficient approaches to explore and visualize SVs and directly compare two or more individuals is desirable. In this article, we present a visualization approach that uses space-filling Hilbert curves to explore SVs based on both read-depth and pair-end information. An interactive open-source Java application, called Meander, implements the proposed methodology, and its functionality is demonstrated using two cases. With Meander, users can explore variations at different levels of resolution and simultaneously compare up to four different individuals against a common reference. The application was developed using Java version 1.6 and Processing.org and can be run on any platform. It can be found at http://homes.esat.kuleuven.be/~bioiuser/meander.     

Atomistic details of effect of disulfide bond reduction on active site of Phytase B from Aspergillus niger: A MD Study

The molecular integrity of the active site of phytases from fungi is critical for maintaining phytase function as efficient catalytic machines. In this study, the molecular dynamics (MD) of two monomers of phytase B from Aspergillus niger, the disulfide intact monomer (NAP) and a monomer with broken disulfide bonds (RAP), were simulated to explore the conformational basis of the loss of catalytic activity when disulfide bonds are broken. The simulations indicated that the overall secondary and tertiary structures of the two monomers were nearly identical but differed in some crucial secondary–structural elements in the vicinity of the disulfide bonds and catalytic site. Disulfide bonds stabilize the β-sheet that contains residue Arg66 of the active site and destabilize the α-helix that contains the catalytic residue Asp319. This stabilization and destabilization lead to changes in the shape of the active–site pocket. Functionally important hydrogen bonds and atomic fluctuations in the catalytic pocket change during the RAP simulation. None of the disulfide bonds are in or near the catalytic pocket but are most likely essential for maintaining the native conformation of the catalytic site.

Abbreviations

PhyB - 2.5 pH acid phophatese from Aspergillus niger, NAP - disulphide intact monomer of Phytase B, RAP - disulphide reduced monomer of Phytase B, Rg - radius of gyration, RMSD - root mean square deviation, MD - molecular dynamics.     

Restoration of Dry Afromontane Forest Using Pioneer Shrubs as Nurse-Plants for Olea europaea ssp. cuspidata

Shrubs are often considered competitive barriers for seedlings planted in reforestation programs, although they can facilitate tree recruitment, especially in ecosystems under high abiotic stress. An alternative reforestation technique using pioneer shrubs as nurse‐plants for Olea europaea ssp. cuspidata was tested in exclosures in northern Ethiopia. Seedlings were planted in three different microhabitats, and their survival was monitored. The microhabitats were bare soil patches between shrubs, patches under the dominant shrub Acacia etbaica, and patches under Euclea racemosa, an evergreen shrub, which supports the majority of naturally established Olea recruits. The ability of shrubs to offer protection against browsing goats was tested experimentally. Controlled shading was used to determine whether solar irradiation causes seedling mortality in environments without water stress. Data were analyzed using Kaplan–Meier survival analysis, Kruskal–Wallis analysis of variance (ANOVA), and one‐way ANOVA. Olea survival was significantly higher and shoot damage by goats was lower when planted under shrub cover compared to bare soil patches, particularly under Euclea canopies, although high shade levels reduced seedling performance. Reduction of solar radiation by shrub canopies and thus control of soil–water evaporation and seedling transpiration most likely controlled the observed facilitation. Planting under shrubs may increase seedling survival and assist regeneration of dry Afromontane vegetation. Preserving pioneers also reduces soil erosion and conserves biodiversity. Excluding livestock is essential for Olea woodland restoration and allows persistent but morphologically modified Olea shrubs to develop vigorous regrowth. Facilitative processes are guiding principles for assisted forest restoration, but above‐average rains may be critical to restore higher biomass levels in semiarid areas.