Forest bioenergy climate impact can be improved by allocating forest residue removal

Bioenergy from forest residues can be used to avoid fossil carbon emissions, but removing biomass from forests reduces carbon stock sizes and carbon input to litter and soil. The magnitude and longevity of these carbon stock changes determine how effective measures to utilize bioenergy from forest residues are to reduce greenhouse gas (GHG) emissions from the energy sector and to mitigate climate change. In this study, we estimate the variability of GHG emissions and consequent climate impacts resulting from producing bioenergy from stumps, branches and residual biomass of forest thinning operations in Finland, and the contribution of the variability in key factors, i.e. forest residue diameter, tree species, geographical location of the forest biomass removal site and harvesting method, to the emissions and their climate impact. The GHG emissions and the consequent climate impacts estimated as changes in radiative forcing were comparable to fossil fuels when bioenergy production from forest residues was initiated. The emissions and climate impacts decreased over time because forest residues were predicted to decompose releasing CO₂ even if left in the forest. Both were mainly affected by forest residue diameter and climatic conditions of the forest residue collection site. Tree species and the harvest method of thinning wood (whole tree or stem‐only) had a smaller effect on the magnitude of emissions. The largest reduction in the energy production climate impacts after 20 years, up to 62%, was achieved when coal was replaced by the branches collected from Southern Finland, whereas the smallest reduction 7% was gained by using stumps from Northern Finland instead of natural gas. After 100 years the corresponding values were 77% and 21%. The choice of forest residue biomass collected affects significantly the emissions and climate impacts of forest bioenergy.     

Improved sulfur nutrition provides the basis for enhanced production of sulfur-containing defense compounds in Arabidopsis thaliana upon inoculation with Alternaria brassicicola

The antifungal activities of many sulfur-containing defense compounds suggest a connection between pathogen infection, primary sulfur metabolism and sulfate nutritional status of plants. This relationship was investigated using Arabidopsis thaliana plants that were cultivated under different sulfur regimes and challenged by Alternaria brassicicola. Plants grown with 500 μM sulfate were significantly less infected compared to plants grown on 50 μM sulfate. Upon infection, the formation of the sulfur-containing defense compound camalexin and the gene expression of the sulfur-rich defense peptide defensin were clearly enhanced in plants grown with an optimal compared to a sufficient sulfate supply in the growth medium. Elevated levels of sulfite and O-acetylserine and cysteine biosynthetic enzymes after infection indicated a stimulation of sulfur metabolism under the higher sulfate supply. The results suggest that, in addition to pathogen-triggered activation of sulfur metabolism and sulfur-containing defense compound formation, the sulfate nutritional status is sensed to contribute to plant defense.     

The effect of pectin, corn and wheat starch, inulin and pH on in vitro production of methane, short chain fatty acids and on the microbial community composition in rumen fluid

Methane emission from livestock, ruminants in particular, contributes to the build up of greenhouse gases in the atmosphere. Therefore the focus on methane emission from ruminants has increased. The objective of this study was to investigate mechanisms for methanogenesis in a rumen fluid-based in vitro fermentation system as a consequence of carbohydrate source (pectin, wheat and corn starch and inulin) and pH (ranging from 5.5 to 7.0). Effects were evaluated with respect to methane and short chain fatty acid (SCFA) production, and changes in the microbial community in the ruminal fluid as assessed by terminal-restriction fragment length polymorphism (T-RFLP) analysis. Fermentation of pectin resulted in significantly lower methane production rates during the first 10 h of fermentation compared to the other substrates (P = 0.001), although total methane production was unaffected by carbohydrate source (P = 0.531). Total acetic acid production was highest for pectin and lowest for inulin (P < 0.001) and vice versa for butyric acid production from pectin and inulin (P < 0.001). Total propionic acid production was unaffected by the carbohydrate source (P = 0.791). Methane production rates were significantly lower for fermentations at pH 5.5 and 7.0 (P = 0.005), sustained as a trend after 48 h (P = 0.059), indicating that there was a general optimum for methanogenic activity in the pH range from 6.0 to 6.5. Decreasing pH from 7.0 to 5.5 significantly favored total butyric acid production (P < 0.001). Principle component analysis of T-RFLP patterns revealed that both pectin and pH 5.5 resulted in pronounced changes in the microbial community composition. This study demonstrates that both carbohydrate source and pH affect methane and SCFA production patterns, and the microbial community composition in rumen fluid.     

Changes in specific protein degradation rates in Arabidopsis thaliana reveal multiple roles of Lon1 in mitochondrial protein homeostasis

Mitochondrial Lon1 loss impairs oxidative phosphorylation complexes and TCA enzymes and causes accumulation of specific mitochondrial proteins. Analysis of over 400 mitochondrial protein degradation rates using ¹⁵N labelling showed that 205 were significantly different between wild type (WT) and lon1‐1. Those proteins included ribosomal proteins, electron transport chain subunits and TCA enzymes. For respiratory complexes I and V, decreased protein abundance correlated with higher degradation rate of subunits in total mitochondrial extracts. After blue native separation, however, the assembled complexes had slow degradation, while smaller subcomplexes displayed rapid degradation in lon1‐1. In insoluble fractions, a number of TCA enzymes were more abundant but the proteins degraded slowly in lon1‐1. In soluble protein fractions, TCA enzymes were less abundant but degraded more rapidly. These observations are consistent with the reported roles of Lon1 as a chaperone aiding the proper folding of newly synthesized/imported proteins to stabilise them and as a protease to degrade mitochondrial protein aggregates. HSP70, prohibitin and enzymes of photorespiration accumulated in lon1‐1 and degraded slowly in all fractions, indicating an important role of Lon1 in their clearance from the proteome.     

Analysis of the Arabidopsis O-acetylserine(thiol)lyase gene family demonstrates compartment-specific differences in the regulation of cysteine synthesis

Cys synthesis in plants takes place in plastids, cytosol, and mitochondria. Why Cys synthesis is required in all compartments with autonomous protein biosynthesis and whether Cys is exchanged between them has remained enigmatic. This question was addressed using Arabidopsis thaliana T-DNA insertion lines deficient in the final step of Cys biosynthesis catalyzed by the enzyme O-acetylserine(thiol)lyase (OAS-TL). Null alleles of oastlA or oastlB alone showed that cytosolic OAS-TL A and plastid OAS-TL B were completely dispensable, although together they contributed 95% of total OAS-TL activity. An oastlAB double mutant, relying solely on mitochondrial OAS-TL C for Cys synthesis, showed 25% growth retardation. Although OAS-TL C alone was sufficient for full development, oastlC plants also showed retarded growth. Targeted affinity purification identified the major OAS-TL-like proteins. Two-dimensional gel electrophoresis and mass spectrometry showed no compensatory changes of OAS-TL isoforms in the four mutants. Steady state concentrations of Cys and glutathione and pulse-chase labeling with [35S]sulfate indicated strong perturbation of primary sulfur metabolism. These data demonstrate that Cys and also sulfide must be sufficiently exchangeable between cytosol and organelles. Despite partial redundancy, the mitochondria and not the plastids play the most important role for Cys synthesis in Arabidopsis.     

Effects of Propagule Density and Survival Strategies on Establishment and Growth: Further Investigations in the Phylloplane Fungal Model System

This work builds on an earlier culture study where we determined that species diversity of competing saprotrophic phyllpolane fungi had only a negligible effect on the establishment and coexistence of a target fungus, Pestalotia vaccinii. Here, we explore preliminary evidence suggesting that spore density is a more important contributing factor to colonization and coexistence. We examine the influence of propagule density in vitro on establishment and growth of select members of the phylloplane of Vaccinium macrocarpon (American cranberry). To evaluate the response of the weak pathogen P. vaccinii to changes in competitors spore density, we chose saprotrophs from the previous investigation that had the greatest inhibitory effect on the establishment of P. vaccinii (Curvularia lunata), an intermediate inhibitory effect (Alternaria alternata) and the least inhibitory effect (Penicillium sp.). A constant target spore concentration of 50 viable spores of P. vaccinii was pit against densities of the three individual competitors ranging between 12 and 200 spores. As viable propagule density increased, establishment and coexistence of P. vaccinii significantly decreased, with C. lunata and A. alternata decreasing the growth of P. vaccinii more than Penicillium sp. Concomitantly, both C. lunata and Penicillium sp. were not significantly affected by overall spore density but were significantly affected by the presence of P. vaccinii. A. alternata, on the other hand, was not significantly influenced by the presence of P. vaccinii but was significantly affected by overall spore density. An in vitro investigation into the effect of interspecific competition on mycelial growth suggests how different survival strategies and community assembly rules might influence both growth and development. Growth of P. vaccinii was significantly less when interacting with C. lunata than when interacting with either A. alternata or Penicillium sp. Conversely, P. vaccinii had the greatest effect on the growth of C. lunata, less of an effect on the growth of A. alternata, and the least effect on Penicillium sp.     

P80, the HinT interacting membrane protein,is a secreted antigen of <Emphasis Type="Italic">Mycoplasma hominis</Emphasis>

Background  

Mycoplasmas are cell wall-less bacteria which encode a minimal set of proteins. In Mycoplasma hominis, the genes encoding the surface-localized membrane complex P60/P80 are in an operon with a gene encoding a cytoplasmic, nucleotide-binding protein with a characteristic Histidine triad motif (HinT). HinT is found in both procaryotes and eukaryotes and known to hydrolyze adenosine nucleotides in eukaryotes. Immuno-precipitation and BIACore analysis revealed an interaction between HinT and the P80 domain of the membrane complex. As the membrane anchored P80 carries an N-terminal uncleaved signal peptide we have proposed that the N-terminus extends into the cytoplasm and interacts with the cytosolic HinT.     

The progesterone derivative dydrogesterone abrogates murine stress-triggered abortion by inducing a Th2 biased local immune response

Stress is known to induce abortions in mice and humans, putatively via increased levels of abortogenic Th1 cytokines and a decrease of progesterone. Adequate levels of progesterone exert an antiabortive response through binding to the progesterone-receptor, which induces the release of progesterone-induced blocking factor (PIBF) from lymphocytes. PIBF is highly pregnancy-protective by induction of a Th2 biased immune activity. The aim of this study was to investigate the effect of the progesterone derivative dydrogesterone (6-dehydro-retroprogesterone) in stress-triggered murine abortion. DBA/2J-mated CBA/J female mice were randomized in different groups: two groups were treated with different dydrogesterone dosages in a single injection before exposure to sound stress on Day 5 of pregnancy, one group was exposed to stress without dydrogesterone treatment, the fourth group received no stress and no dydrogesterone. On gestation Day 13, a highly elevated abortion rate was detected in stressed mice compared to control mice. Stressed animals presented lower levels of progesterone and PIBF in plasma and a reduced staining intensity of progesterone receptor at the feto-maternal interface. Injection of dydrogesterone abrogated the effect of stress on the abortion rate. Further, dydrogesterone increased levels of plasma PIBF in stressed mice, but did not affect progesterone levels. Interestingly, dydrogesterone dramatically increased the percentage of IL-4 positive decidual immune cells in stressed mice. Our data suggest that dydrogesterone abrogates stress-triggered abortion by inducing a Th2 biased local immune response.