Native C3 Research Articles

Lectin pathway effector enzyme mannan-binding lectin-associated serine protease-2 can activate native complement C3 in absence of C4 and/or C2.

All 3 activation pathways of complement-the classic pathway (CP), the alternative pathway, and the lectin pathway (LP)- converge into a common central event: the cleavage and activation of the abundant third complement component, C3, via formation of C3-activating enzymes (C3 convertases). The fourth complement component, C4, and the second component, C2, are indispensable constituents of the C3 convertase complex, C4bC2a, which is formed by both the CP and the LP. Whereas in the absence of C4, CP can no longer activate C3, LP retains a residual but physiologically critical capacity to convert native C3 into its activation fragments, C3a and C3b. This residual C4 and/or C2 bypass route is dependent on LP-specific mannan-binding lectin-associated serine protease-2. By using various serum sources with defined complement deficiencies, we demonstrate that, under physiologic conditions LP-specific C4 and/or C2 bypass activation of C3 is mediated by direct cleavage of native C3 by mannan-binding lectin-associated serine protease-2 bound to LP-activation complexes captured on ligand-coated surfaces.-Yaseen, S., Demopulos, G., Dudler, T., Yabuki, M., Wood, C. L., Cummings, W. J., Tjoelker, L. W., Fujita, T., Sacks, S., Garred, P., Andrew, P., Sim, R. B., Lachmann, P. J., Wallis, R., Lynch, N., Schwaeble, W. J. Lectin pathway effector enzyme mannan-binding lectin-associated serine protease-2 can activate native complement C3 in absence of C4 and/or C2.

Differential elemental uptake in three pseudo-metallophyte C4 grasses in situ in the eastern USA.

Elemental uptake in serpentine floras in eastern North America is largely unknown. The objective of this study was to determine major and trace element concentrations in soil and leaves of three native pseudo-metallophyte C4 grasses in situ at five sites with three very different soil types, including three serpentine sites, in eastern USA. Pseudo-total and extractible concentrations of 15 elements were measured and correlated from the soils and leaves of three species at the five sites. Element concentrations in soils of pseudo-metallophytes varied up to five orders of magnitude. Soils from metalliferous sites exhibited higher concentrations of their characteristic elements than non-metalliferous. In metallicolous populations, elemental concentrations depended on the element. Concentrations of major elements (Ca, Mg, K) in leaves were lower than typical toxicity thresholds, whereas concentrations of Zn were higher. In grasses, species can maintain relatively low metal concentrations in their leaves even when soil concentrations are richer. However, in highly Zn-contaminated soil, we found evidence of a threshold concentration above which Zn uptake increases drastically. Finally, absence of main characteristics of serpentine soil at one site indicated the importance of soil survey and restoration to maintain serpentinophytes communities and avoid soil encroachment.

Functional and structural characterization of four mouse monoclonal antibodies to complement C3 with potential therapeutic and diagnostic applications.

C3 is the central component of the complement system. Upon activation, C3 sequentially generates various proteolytic fragments, C3a, C3b, iC3b, C3dg, each of them exposing novel surfaces, which are sites of interaction with other proteins. C3 and its fragments are therapeutic targets and markers of complement activation. We report the structural and functional characterization of four monoclonal antibodies (mAbs) generated by immunizing C3-deficient mice with a mixture of human C3b, iC3b and C3dg fragments, and discuss their potential applications. This collection includes three mAbs interacting with native C3 and inhibiting AP complement activation; two of them by blocking the cleavage of C3 by the AP C3-converase and one by impeding formation of the AP C3-convertase. The interaction sites of these mAbs in the target molecules were determined by resolving the structures of Fab fragments bound to C3b and/or iC3b using electron microscopy. A fourth mAb specifically recognizes the iC3b, C3dg, and C3d fragments. It binds to an evolutionary-conserved neoepitope generated after C3b cleavage by FI, detecting iC3b/C3dg deposition over opsonized surfaces by flow cytometry and immunohistochemistry in human and other species. Because well-characterized anti-complement mAbs are uncommon, the mAbs reported here may offer interesting therapeutic and diagnostic opportunities.

Carbon Sequestration in Response to Grassland–Shrubland–Turfgrass Conversions and a Test for Carbonate Biomineralization in Desert Soils, New Mexico, USA

Core Ideas Soil carbonate is typically viewed as a soil mineral that requires centuries to accumulate; our study indicates that it can be generated in months to years. If the source of Ca is directly from silicate minerals, soil carbonate could be managed to sequester atmospheric CO2. Carbon‐13 values can change in less than a decade for both soil organic and inorganic C. This study uses an experimental pedology approach using controls, treatments, and replications. This study uses an experimental pedology approach to examine (i) how the conversion of native C4 grassland to C3 woody shrubs then to irrigated C4 turfgrass affects both soil organic C (SOC) and soil inorganic C (SIC) and (ii) whether SIC can be enhanced by microbial biomineralization. Three sites were studied in the Chihuahuan Desert of New Mexico. At each site, SOC, SIC, and their δ13C values were measured on control soil samples and compared to samples treated with liquid growth medium and Ca(OH)2 at 10 and 40 cm. The treated samples were left to react for 1 mo in February, May, and August of 2014. Using a space‐for‐time substitution, soil organic C decreased when native grasslands converted to desert shrubs, then sharply increased after desert shrubs were converted to irrigated turfgrass. Most surprising, however, was the increase of SIC in the turfgrass site, which doubled in 6 yr. The δ13C values of both SOC and SIC reflected the change from C4 to C3 then back to C4 vegetation and showed how rapidly SOC and SIC can change their isotopic signatures. Soil inorganic C formation was slightly higher for the liquid growth medium, but no statistically significant differences were observed between the treatments and control samples. In addition, no biomineralization was observed with microscopy, perhaps because the 1‐mo reaction time was too short and the amount applied was too small. Although SIC is typically viewed as a soil mineral that requires centuries to accumulate, our study indicate that SIC can be generated in months to years if the soil environment is suitable.

Biochar and plant growth promoting rhizobacteria effects on switchgrass (Panicum virgatum cv. Cave-in-Rock) for biomass production in southern Québec depend on soil type and location

Switchgrass (Panicum virgatum L.) is a fast growing native C4 perennial and a lignocellulosic biomass crop for North America. In combination with biochar, an active plant growth promoting rhizobacterial (PGPR) community can contribute to the long-term sequestration of carbon in soil, fix nitrogen, and enhance the availability of other nutrients to plants. Biochar and PGPR have the potential to improve grass biomass production, but they have not been tested together under high-latitude temperate zone field conditions. Therefore, the objective of this three-year field study was to determine whether there were effects on biomass yield and yield components of switchgrass (cv. Cave-in-Rock) due to a rhizobacterium that was able to mobilize soil phosphorus (Pseudomonas rhodesiae), a bacterial consortium that was able to supply nitrogen (Paenibacillus polymyxa, Rahnella sp., and Serrati sp.), and pine wood chip biochar applied as a soil amendment at 20 Mg ha−1. The incorporation of biochar, or inoculation with the N-fixing consortium, and the combined inoculation of the experimental bacteria had positive effects on switchgrass height. At a loam soil site in Sainte-Anne-de-Bellevue, Québec, when nitrogen fertilizer was not applied, the addition of biochar had a positive effect on stand count (tillers m−1 row). On the sandy soil in Sainte-Anne-de-Bellevue, when biochar was applied with 100 kg N ha−1, biomass yield increased over the control but did not provide additional benefits over plots receiving only 50 kg N ha−1. It remains unclear whether or not the increased C sequestration of this management system justifies increased N fertilizer usage.

Simulating diverse native C4 perennial grasses with varying rainfall

Rainfall is recognized as a major factor affecting the rate of plant growth development. The impact of changes in amount and variability of rainfall on growth and production of different forage grasses needs to be quantified to determine how climate change can impact rangelands. Comparative studies to evaluate the growth of several perennial forage species at different rainfall rates will provide useful information by identifying forage management strategies under various rainfall scenarios. In this study, the combination of rainfall changes and soil types on the plant growth of 10 perennial forage species was investigated with both the experimental methods, using rainout shelters, and with the numerical methods using the plant growth simulation model, ALMANAC. Overall, most species significantly increased basal diameter and height as rainfall increased. Like measured volume, simulated yields for all species generally increased as rainfall increased. But, large volume and yield increases were only observed between 350 and 850 mm/yr. Simulating all species growing together competing agrees relatively well with observed plant volumes at low rainfall treatment, while simulating all species growing separately was slightly biased towards overestimation on low rainfall effect. Both simulations agree relatively well with observed plant volume at high rainfall treatment.

Complement C3 is expressed by mast cells in cutaneous vasculitis and is degraded by chymase.

The complement factor C3 and chymase released from tryptase(+), chymase(+) mast cells may be involved in the pathogenesis of cutaneous leukocytoclastic vasculitis. To study whether mast cells contain C3 in vasculitis and whether chymase interacts with C3, cryosections from vasculitis biopsies were double-stained histochemically for C3c in tryptase(+) mast cells, as well as for chymase and vessel wall C3c, or they were treated with 5µg/ml rh-chymase for 24h followed by immunofluorescence (IF) analysis of C3c, IgG, IgM and IgA. The effect of rh-chymase on purified human C3, C3a and IgG was studied using SDS-PAGE electrophoresis and LAD2 mast cell cultures. The results show that 34.2±17.9, 37.4±15.5 and 43.4±18.6% (mean±SD) of the mast cells express C3c immunoreactivity in the healthy skin, initial petechial (IP) and palpable purpura (PP) lesions, respectively. About 9.4-12.1% of the chymase(+) mast cells were in apparent contact with C3c(+) vessels in IP and PP. The treatment of cryosections with rh-chymase decreased the IF staining of C3c, but not that of immunoglobulins. In SDS-PAGE, 1-10µg/ml rh-chymase degraded the alpha- and beta-chains of C3, but did not degrade IgG. Unexpectedly, the rh-chymase treatment of C3 produced fragments that resulted in the release of tryptase and histamine from LAD2 cells. However, rh-chymase degraded C3a and consequently inhibited C3a activity on LAD2. In conclusion, mast cells can be one source for C3 in the early and late phases of vasculitis pathogenesis. However, rh-chymase degraded native C3, vessel wall C3c, and biologically active C3a. Therefore, chymase may control C3-related pathology.

Site Preparation Drives Long-Term Plant Community Dynamics in Restored Tallgrass Prairie: A Case Study in Southeastern South Dakota

Most tallgrass prairies have been destroyed or altered, making restoration an important component to their conservation. Our goal was to evaluate progress 12-years post-restoration at Spirit Mound Historic Prairie and determine whether the outcomes varied based on different land use and restoration histories across the site. We examined changes in plant diversity, richness, evenness, non-native species relative abundance, and community composition from 2004 to 2013. Areas with different restoration treatments and land-use histories showed divergent results. Seventy percent of the site, previously annual row crop, was reconstructed using herbicide application followed by native seeding (hereafter reconstruction). Areas that were previously grazed, 15% of the site, were restored with only partial seeding and no herbicide treatment (hereafter rehabilitation). Species richness and diversity increased over 40% in the reconstruction since 2004 and remained over 1.9 times higher in the reconstructed areas than rehabilitated areas. Diversity did not change in the rehabilitation, but richness increased 47% since 2004. Evenness decreased 11-26% over time in both areas. Non-native species relative abundance did not change from 2004 to 2013, and remained five times higher in the rehabilitation than the reconstruction. Native C4 grass and forb abundance increased over time in the reconstruction, whereas non-native C3 grasses remained dominant in the rehabilitation. These results showed that restoration outcomes were radically different 12-years post-restoration among areas with different prior land uses that were subjected to different restoration practices. Long-term assessments are important to accurately determine restoration progress and inform management decisions.

Effects of elevated CO2 on photosynthetic traits of native and invasive C3 and C4 grasses.

BackgroundRising CO2 is expected to result in changes in plant traits that will increase plant productivity for some functional groups. Differential plant responses to elevated CO2 are likely to drive changes in competitive outcomes, with consequences for community structure and plant diversity. Many of the traits that are enhanced under elevated CO2 also confer competitive success to invasive species, and it is widely believed that invasive species will be more successful in high CO2. However, this is likely to depend on plant functional group, and evidence suggests that C3 plants tend to respond more strongly to CO2.ResultsWe tested the hypothesis that invasive species would be more productive than noninvasive species under elevated CO2 and that stronger responses would be seen in C3 than C4 plants. We examined responses of 15 grass species (eight C3, seven C4), classified as noninvasive or invasive, to three levels of CO2 (390, 700 and 1000 ppm) in a closed chamber experiment. Elevated CO2 decreased conductance and %N and increased shoot biomass and C/N ratio across all species. Differences between invasive and noninvasive species depended on photosynthetic mechanism, with more differences for traits of C3 than C4 plants. Differences in trait means between invasive and noninvasive species tended to be similar across CO2 levels for many of the measured responses. However, noninvasive C3 grasses were more responsive than invasive C3 grasses in increasing tiller number and root biomass with elevated CO2, whereas noninvasive C4 grasses were more responsive than invasive C4 grasses in increasing shoot and root biomass with elevated CO2. For C3 grasses, these differences could be disadvantageous for noninvasive species under light competition, whereas for C4 grasses, noninvasive species may become better competitors with invasive species under increasing CO2.ConclusionsThe ecophysiological mechanisms underlying invasion success of C3 and C4 grasses may differ. However, given that the direction of trait differences between invasive and noninvasive grasses remained consistent under ambient and elevated CO2, our results provide evidence that increases in CO2 are unlikely to change dramatically the competitive hierarchy of grasses in these functional groups.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-016-0082-z) contains supplementary material, which is available to authorized users.

Nitrous oxide and methane fluxes from cattle excrement on C3 pasture and C4-dominated shortgrass steppe

Cattle play a major role in nutrient cycling of grassland ecosystems through biomass removal and excrement deposition (urine and feces). We studied the effects of cattle excrement patches (urine at 430 and feces at 940kgNha−1) on nitrous oxide (N2O) and methane (CH4) fluxes using semi-static chambers on cool-season (C3), Bozoisky-select (Psathyrostachys juncea) pasture, and warm-season (C4)-dominated native rangeland of the shortgrass steppe (SGS) in northeastern Colorado. Nitrous oxide emission factors (EF; i.e., percent of added N emitted as N2ON) did not differ between urine and feces on the C4-dominated native rangeland (0.11 and 0.10%) and C3 pasture (0.13 and 0.10%). These EFs are substantially less than the Intergovernmental Panel on Climate Change (IPCC) Tier 1 Default EF (2%) for manure deposited on pasture, indicating that during dry years the IPCC Tier 1 Default EF would result in a significant overestimation of emissions from excrement patches deposited on SGS C4-dominated native rangeland and C3 pasture. Over the first year of the study (19 June 2012–18 June 2013), cumulative CH4 uptake was 38% greater for urine (−1.49 vs. −1.08kg CH4C ha−1) and 28% greater for control plots (−2.09 vs. −1.63kg CH4C ha−1) on C4-dominated native rangeland compared to C3 pasture. In contrast, feces patches were net sources of CH4 with emissions from the C3 pasture (0.64kg CH4C ha−1) 113% greater than the C4-dominated native rangeland (0.30kg CH4C ha−1). Conversion of C4-dominated native rangeland to C3 pasture can have long term effects on CH4 uptake; therefore consideration should be taken before implementing this management practice.

Reducing rainfall amount has a greater negative effect on the productivity of grassland plant species than reducing rainfall frequency.

The productivity of semiarid Australian grassland ecosystems is currently limited by water availability and may be impacted further by predicted changes in rainfall regimes associated with climate change. In this study, we established a rainfall manipulation experiment to determine the effects of reduced frequency (RF; 8 days between water events) and reduced magnitude (RM; 50% reduction in amount) of rainfall events on the physiology and above- and below-ground growth of five grassland plant species with differing traits. Native C4 grasses exhibited the highest productivity in well watered, control (Cont) conditions, as well as in RF and RM treatments. The RF treatment generally had little effect on total biomass, rooting distributions or photosynthesis, suggesting species were relatively tolerant of reduction in the frequency of rainfall events. However, the RM treatment had a negative effect on total biomass and physiology, and generally resulted in a shift towards shallower rooting profiles. Overall, the reduction in biomass was greater in RM than RF, suggesting that rainfall magnitude may be a more important determinant of grassland productivity and composition than the frequency of rainfall events under future climates.

Abstract TP278: Complement Cascade Inhibition Abrogates tPA-mediated Hemorrhage and Brain Edema Following Ischemic Stroke

Introduction: Tissue plasminogen activator (tPA) remains the only approved pharmacologic treatment for patients with ischemic stroke. Although intravenous thrombolysis improves outcome in a subset of patients, tPA also increases symptomatic hemorrhage and worsens brain edema, thus limiting its clinical applicability. Among several putative mechanisms, plasmin-meditated complement cascade activation likely plays a critical role in the deleterious effects of tPA. Hypothesis: tPA administration promotes C3 cleavage and complement activation in ischemic brain, and pharmacologic inhibition of the C3a receptor abrogates tPA-mediated hemorrhage and brain edema following reperfused stroke. Methods: C3a concentrations were assessed using ELISA. Transient focal cerebral ischemia was induced in mice by 60 minutes of middle cerebral artery occlusion (MCAO), with tPA (10mg/kg) or saline injected intravenously at reperfusion. C3a receptor antagonist (1mg/kg) or vehicle was administered 45 minutes prior to MCAO. Infarct volume was determined at 24 hours by TTC staining, neurological function was assessed on a 5-point scale, and brain hemorrhage was quantified using a spectrophotometric assay. Cerebral edema was determined by calculating the difference in volume between ischemic and non-ischemic hemispheres and normalized to infarct volume. Results: The incubation of tPA with native C3 as well as plasma promotes the generation of C3a. Similarly, intravenous tPA administration dramatically increases cerebral C3a levels in the ischemic hemisphere following MCAO. Intravenous tPA significantly reduces infarct volume (p<0.05) and improves neurological function (p<0.05) in our stroke model. However, tPA also dramatically increases cerebral hemorrhage (p<0.05) and relative cerebral edema (p<0.05). Administration of a C3a receptor antagonist abrogates this hemorrhagic conversion (p<0.05) and brain edema (p<0.05). Conclusions: Intravenous tPA administration promotes complement activation through C3 cleavage in ischemic brain. Pharmacologic inhibition of the C3a receptor protects against the deleterious side effects of tPA and represents a promising therapeutic strategy for stroke patients.

Reducing rainfall amount has a greater negative effect on the productivity of grassland plant species than reducing rainfall frequency.

The productivity of semiarid Australian grassland ecosystems is currently limited by water availability and may be impacted further by predicted changes in rainfall regimes associated with climate change. In this study, we established a rainfall manipulation experiment to determine the effects of reduced frequency (RF; 8 days between water events) and reduced magnitude (RM; 50% reduction in amount) of rainfall events on the physiology and above- and below-ground growth of five grassland plant species with differing traits. Native C4 grasses exhibited the highest productivity in well watered, control (Cont) conditions, as well as in RF and RM treatments. The RF treatment generally had little effect on total biomass, rooting distributions or photosynthesis, suggesting species were relatively tolerant of reduction in the frequency of rainfall events. However, the RM treatment had a negative effect on total biomass and physiology, and generally resulted in a shift towards shallower rooting profiles. Overall, the reduction in biomass was greater in RM than RF, suggesting that rainfall magnitude may be a more important determinant of grassland productivity and composition than the frequency of rainfall events under future climates.

Spatiotemporal patterns of the gross primary production in the salt marshes with rapid community change: A coupled modeling approach

Coastal salt marshes are among the most productive ecosystems in the world. However, rapid changes in the vegetation communities of salt marshes caused by exotic species invasion and plant propagation requires a better understanding of how these shifts affect the landscape-scale variations of gross primary production (GPP). In the Yangtze Estuary of eastern China, we firstly compared 2-years GPP values obtained through eddy covariance measurements, satellite-based estimations and model simulations in two vegetation mixtures consisting of exotic Spartina alterniflora (C4 plant) and dominant native Phragmites australis and Scirpus spp. (C3 plants) The results indicated that the low-resolution remote sensing data with light-use efficiency method did not represent well the seasonal course of GPP relative to flux measurements and underestimated the annual amount GPP by 25–32%. In contrast, a detailed process-based vegetation model with species-specific parameterizations could identify the proportions of GPP from exotic C4 and native C3 vegetation and accurately reproduce the seasonal course and annual amount of GPP in the mixtures. The slopes of the linear regressions between the measured and modeled GPP were close (1.09 and 0.89 for the two mixtures, respectively) to the 1:1 line. To further evaluate the variations in GPP throughout the salt marshes, we coupled high-resolution remote sensing data to the vegetation model by transforming the vegetation index into the leaf area index (LAI) for different species. The coupled model reproduced the spatiotemporal dynamics of GPP in the salt marshes with rapid community change during the period of 2000–2008 and identified the variations of GPP from different species. The simulations indicated that the contribution rate of exotic S. alterniflora to GPP has been greater than that of native species since 2003–2004. Therefore, we suggest that this method is useful for high-resolution estimations of regional GPP in other coastal marshes with invasive S. alterniflora in China.

Native and alien herbaceous plants in the Brazilian Cerrado are (co-)limited by different nutrients

The diverse flora of the Brazilian Cerrado is threatened by agricultural expansion, nutrient enrichment and invasion of alien plants. We performed a fertilization experiment to investigate the nature of nutrient limitation in Cerrado vegetation, and evaluate whether native and alien invasive species are limited by the same or different nutrients. We applied various combinations of nutrients (phosphorus (P), nitrogen (N), and a mixture of other macro- and micro-nutrients (‘cations treatment’)) to six types of Cerrado vegetation. We then studied over a 3-year period how these treatments affected the aboveground biomass of native forbs, native C3 and C4 grasses, and invasive C4 grasses. The full nutrient treatment (N + P+ ‘cations’) significantly increased total community biomass across our sites, but P alone had no effect. The nutrient treatments also affected the relative abundance of functional plant groups in the six vegetation types. P addition, either alone or in combination with other nutrients, increased the biomass of alien C4 grasses, where present, whereas the cations treatment stimulated growth of the native C4 grasses. Addition of N + P reduced the biomass of native C3 grasses. Our results indicate co-limitation by several nutrients, including P, perhaps N, and at least one other nutrient. Further research is needed to determine what the other nutrient (or nutrients) may be. Native and invasive species appear to be limited by different nutrients, with P alone stimulating growth of African C4 grasses. This should be considered in managing both natural and invaded communities.

Molecular insights into the surface-specific arrangement of complement C5 convertase enzymes

BackgroundComplement is a large protein network in plasma that is crucial for human immune defenses and a major cause of aberrant inflammatory reactions. The C5 convertase is a multi-molecular protease complex that catalyses the cleavage of native C5 into its biologically important products. So far, it has been difficult to study the exact molecular arrangement of C5 convertases, because their non-catalytic subunits (C3b) are covalently linked to biological surfaces through a reactive thioester. Through development of a highly purified model system for C5 convertases, we here aim to provide insights into the surface-specific nature of these important protease complexes.ResultsAlternative pathway (AP) C5 convertases were generated on small streptavidin beads that were coated with purified C3b molecules. Site-specific biotinylation of C3b via the thioester allowed binding of C3b in the natural orientation on the surface. In the presence of factor B and factor D, these C3b beads could effectively convert C5. Conversion rates of surface-bound C3b were more than 100-fold higher than fluid-phase C3b, confirming the requirement of a surface. We determine that high surface densities of C3b, and its attachment via the thioester, are essential for C5 convertase formation. Combining our results with molecular modeling explains how high C3b densities may facilitate intermolecular interactions that only occur on target surfaces. Finally, we define two interfaces on C5 important for its recognition by surface-bound C5 convertases.ConclusionsWe establish a highly purified model that mimics the natural arrangement of C5 convertases on a surface. The developed model and molecular insights are essential to understand the molecular basis of deregulated complement activity in human disease and will facilitate future design of therapeutic interventions against these critical enzymes in inflammation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0203-8) contains supplementary material, which is available to authorized users.

Resource-use efficiency explains grassy weed invasion in a low-resource savanna in north Australia.

Comparative studies of plant resource use and ecophysiological traits of invasive and native resident plant species can elucidate mechanisms of invasion success and ecosystem impacts. In the seasonal tropics of north Australia, the alien C4 perennial grass Andropogon gayanus (gamba grass) has transformed diverse, mixed tree-grass savanna ecosystems into dense monocultures. To better understand the mechanisms of invasion, we compared resource acquisition and usage efficiency using leaf-scale ecophysiological and stand-scale growth traits of A. gayanus with a co-habiting native C4 perennial grass Alloteropsis semialata. Under wet season conditions, A. gayanus had higher rates of stomatal conductance, assimilation, and water use, plus a longer daily assimilation period than the native species A. semialata. Growing season length was also ~2 months longer for the invader. Wet season measures of leaf scale water use efficiency (WUE) and light use efficiency (LUE) did not differ between the two species, although photosynthetic nitrogen use efficiency (PNUE) was significantly higher in A. gayanus. By May (dry season) the drought avoiding native species A. semialata had senesced. In contrast, rates of A. gayanus gas exchange was maintained into the dry season, albeit at lower rates that the wet season, but at higher WUE and PNUE, evidence of significant physiological plasticity. High PNUE and leaf 15N isotope values suggested that A. gayanus was also capable of preferential uptake of soil ammonium, with utilization occurring into the dry season. High PNUE and fire tolerance in an N-limited and highly flammable ecosystem confers a significant competitive advantage over native grass species and a broader niche width. As a result A. gayanus is rapidly spreading across north Australia with significant consequences for biodiversity and carbon and retention.

Evaluation of biological pretreatments to increase the efficiency of the saccharification process using Spartina argentinensis as a biomass resource

Second generation bioethanol obtained from native perennial grasses offers a promising alternative for biofuel production, avoiding land use competition for crops production. Spartina argentinensis is a native perennial C4 grass with high photosynthetic rates, well adapted to halo-hydromorphic soils, though its forage quality (palatability and digestibility) for livestock is quite low due to its high lignin content. Hence, cattle raisers burn these grasslands frequently in order to stimulate the emergence of new leaves with higher digestibility for cattle feeding. Lignin is the main barrier to overcome in order to efficiently hydrolyze the cellulose for bioethanol production. In this work, we evaluate different pretreatments (phosphoric acid, ligninolytic enzymes and fungal supernatants) aimed to remove lignin and improving cellulose hydrolysis efficiency. Results show that pretreatment with Pycnoporus sanguineus supernatant improves fermentable carbohydrates availability, compared with a conventional chemical pretreatment, and that 56.84% of cellulose can be hydrolyzed using this pretreatment.

Stability and genetic control of morphological, biomass and biofuel traits under temperate maritime and continental conditions in sweet sorghum (Sorghum bicolour).

Eight morphological, biomass and biofuel traits were found with high broad-sense heritability and 18 significant QTLs discovered including one locus controlling the stem juice trait for sorghum grown in Denmark and China. Sweet sorghum with tall plant, fast maturation and high stem Brix content can be bred as a biofuel crop for Northern Europe. Sweet sorghum (Sorghum bicolour), a native tropical C4 crop, has attracted interest as a bioenergy crop in northern countries due to its juice-rich stem and high biomass production. Little is known about the traits important for its adaptation to high altitude climatic conditions and their genetic controls. Recombinant inbred lines derived from a cross between a sweet and a grain kaoliang sorghum were used in five field trials in Denmark and in China to identify the stability and genetic controls of morphological, biomass and biofuel traits during three consecutive summers with short duration, cool temperatures and long days. Eight out of 15 traits were found with high broad-sense heritability. Strong positive correlations between plant height and biomass traits were observed, while Brix and juice content were under different genetic controls. Using newly developed PAV (presence and absence variant) markers, 53 QTLs were detected, of which 18 were common for both countries, including a locus controlling stem juice (LOD score=20.5, r (2)=37.5%). In Denmark, the heading stage correlated significantly with biomass and morphology traits, and two significant maturity QTLs detected on chromosomes SBI01 and SBI02 co-localised with QTLs previously associated with early-stage chilling tolerance, suggesting that accelerating maturation might be a means of coping with low-temperature stress. Our results suggest that selection for tall and fast maturating sorghum plants combined with high Brix content represents a high potential for breeding bioenergy crop for Northern Europe.

Long-term decline in grassland productivity driven by increasing dryness.

Increasing aridity and drought severity forecast for many land areas could reduce the land carbon (C) sink. However, with limited long-term direct measures, it is difficult to distinguish direct drying effects from counter effects of CO2 enrichment and nitrogen (N) deposition. Here, we document a >50% decline in production of a native C3 grassland over four decades and assign the forcing and timing to increasing aridity and specifically to declining late-summer rainfall. Analysis of C and N stable isotopes in biomass suggests that enhanced water use efficiency via CO2 enrichment may have slightly ameliorated the productivity decline but that changes in N had no effects. Identical declines in a long-term snow-addition experiment definitively identified increasing late-summer dryness as the cause. Our results demonstrate lasting consequences of recent climate change on grassland production and underscore the importance of understanding past climate–ecosystem coupling to predicting future responses to changing climate.