Nitrogen inputs accelerate phosphorus cycling rates across a wide variety of terrestrial ecosystems

? Biologically essential elements--especially nitrogen (N) and phosphorus (P)--constrain plant growth and microbial functioning; however, human activities are drastically altering the magnitude and pattern of such nutrient limitations on land. Here we examine interactions between N and P cycles of P mineralizing enzyme activities (phosphatase enzymes) across a wide variety of terrestrial biomes. ? We synthesized results from 34 separate studies and used meta-analysis to evaluate phosphatase activity with N, P, or N×P fertilization. ? Our results show that N fertilization enhances phosphatase activity, from the tropics to the extra-tropics, both on plant roots and in bulk soils. By contrast, P fertilization strongly suppresses rates of phosphatase activity. ? These results imply that phosphatase enzymes are strongly responsive to changes in local nutrient cycle conditions. We also show that plant phosphatases respond more strongly to fertilization than soil phosphatases. The tight coupling between N and P provides a mechanism for recent observations of N and P co-limitation on land. Moreover, our results suggest that terrestrial plants and microbes can allocate excess N to phosphatase enzymes, thus delaying the onset of single P limitation to plant productivity as can occur via human modifications to the global N cycle.     

Stomatal and photosynthetic responses to shade in sorghum, soybean and eastern gamagrass

We studied photosynthetic and stomatal responses of grain sorghum ( Sorghum bicolor [L.] Moench cv. Pioneer 8500), soybean ( Glycine max L. cv. Flyer) and eastern gamagrass ( Tripsacum dactyloides L.) during experimental sun and shade periods simulating summer cloud cover. Leaf gas exchange measurements of field plants showed that short-term (5 min) shading of leaves to 300–400 μmol m⁻² s⁻¹ photosynthetic photon flux density reduced photosynthesis, leaf temperature, stomatal conductance, transpiration and water use efficiency and increased intercellular CO₂ partial pressure. In all species, photosynthetic recovery was delayed when leaves were reilluminated, apparently by stomatal closure. The strongest stomatal response was in soybean. Photosynthetic recovery was studied further with soybeans grown indoors (maximum photosynthetic photon flux density 1 200 μmol m⁻² s⁻¹). Plants grown indoors had responses to shade similar to those of field plants, except for brief nonstomatal limitation immediately after reillumination. These responses indicated the importance of the light environment during leaf development on assimilation responses to variable light, and suggested different limitations on carbon assimilation in different parts of the soybean canopy. Photosynthetic oxygen evolution recovered immediately upon reillumination, indicating that the light reactions did not limit soybean photosynthetic recovery. While shade periods caused stomatal closure and reduced carbon gain and water loss in all species, the consequences for carbon gain/water loss were greatest in soybean. The occurrence of stomatal closure in all three species may arise from their shared phenologies and herbaceous growth forms.     

Stability across environments of the coffee variety near infrared spectral signature

Previous study on food plants has shown that near infrared (NIR) spectral methods seem effective for authenticating coffee varieties. We confirm that result, but also show that inter-variety differences are not stable from one harvest to the next. We put forward the hypothesis that the spectral signature is affected by environmental factors. The purpose of this study was to find a way of reducing this environmental variance to increase the method's reliability and to enable practical application in breeding. Spectral collections were obtained from ground green coffee samples from multilocation trials. Two harvests of bean samples from 11 homozygous introgressed lines, and the cv 'Caturra' as the control, supplied from three different sites, were compared. For each site, squared Euclidean distances among the 12 varieties were estimated from the NIR spectra. Matrix correlation coefficients were assessed by the Mantel test. We obtained very good stability (high correlations) for inter-variety differences across the sites when using the two harvests data. If only the most heritable zones of the spectrum were used, there was a marked improvement in the efficiency of the method. This improvement was achieved by treating the spectrum as succession of phenotypic variables, each resulting from an environmental and genetic effect. Heritabilities were calculated with confidence intervals. A near infrared spectroscopy signature, acquired over a set of harvests, can therefore effectively characterize a coffee variety. We indicated how this typical signature can be used in breeding to assist in selection.     

Evaluation of eastern gamagrass as dual-purpose complementary bioenergy and forage feedstock to switchgrass

Switchgrass (SG) is considered a model bioenergy crop and a warm-season perennial grass (WSPG) that traditionally served as forage feedstock in the United States. To avoid the sole dependence on SG for bioenergy production, evaluation of other crops to diversify the pool of feedstock is needed. We conducted a 3-year field experiment evaluating eastern gamagrass (GG), another WSPG, as complementary feedstock to SG in one- and two-cut systems, with or without intercropping with crimson clover or hairy vetch, and under different nitrogen (N) application rates. Our results showed that GG generally produced lower biomass (by 29.5%), theoretical ethanol potential (TEP, by 2.8%), and theoretical ethanol yield (TEY, by 32.9%) than corresponding SG under the same conditions. However, forage quality measures, namely acid detergent fiber (ADF), crude protein (CP), and elements P, K, Ca, and Mg were significantly higher in GG than those in SG. Nitrogen fertilizer significantly enhanced biomass (by 1.54 Mg ha⁻¹), lignin content (by 2.10 g kg⁻¹), and TEY (787.12 L ha⁻¹) in the WSPGs compared to unfertilized treatments. Intercropping with crimson clover or hairy vetch did not significantly increase biomass of the WSPGs, or TEP and TEY in unfertilized plots. This study demonstrated that GG can serve as a complementary crop to SG and could be used as a dual-purpose crop for bioenergy and forage feedstock in farmers' rotations.     

Serum-free freezing media support high cell quality and excellent ELISPOT assay performance across a wide variety of different assay protocols

Robust and sensitive ELISPOT protocols are commonly applied concomitant with the development of new immunotherapeutics. Despite the knowledge that individual serum batches differ in their composition and may change properties over time, serum is still commonly used in immunologic assays. Commercially available serum batches are expensive, limited in quantity and need to be pretested for suitability in immunologic assays, which is a laborious process. The aim of this study was to test whether serum-free freezing media can lead to high cell viability and favorable performance across multiple ELISPOT assay protocols. Thirty-one laboratories from ten countries participated in a proficiency panel organized by the Cancer Immunotherapy Immunoguiding Program to test the influence of different freezing media on cell quality and immunologic function. Each center received peripheral blood mononuclear cells which were frozen in three different media. The participants were asked to quantify antigen-specific CD8+ T-cell responses against model antigens using their locally established IFN-gamma ELISPOT protocols. Self-made and commercially available serum-free freezing media led to higher cell viability and similar cell recovery after thawing and resting compared to freezing media supplemented with human serum. Furthermore, the test performance as determined by (1) background spot production, (2) replicate variation, (3) frequency of detected antigen-specific spots and (4) response detection rate was similar for serum and serum-free conditions. We conclude that defined and accessible serum-free freezing media should be recommended for freezing cells stored for subsequent ELISPOT analysis.     

Comparative isozyme polymorphisms of north American eastern gamagrass,Tripsacum dactyloides var.dactyloides and maize,Zea mays L.

Random samples, consisting of at least 100 individual seedlings, were taken from the diploid (2n=2x=36) eastern gamagrass (Tripsacum dactyloides var.dactyloides) and assayed to determine which of 12 enzyme marker loci and isozyme systems would be most informative in providing satisfactory resolution of both maize andTripsacum isozyme systems. For comparison, eight maize inbreds were included in the study to aid evaluation and comparison of the various isozyme systems. In addition, evaluations were conducted to identify if the identified optimum isozyme system could be used to detectTripsacum introgression in maize following a maize ×Tripsacum backcrossing scheme. Using the established isozyme techniques for maize (Zea mays L.), theAdh, Pgd, Cat, Est, B-Glu, Got, Idh, Tpi isozyme systems detected no polymorphism among theTripsacum individuals assayed. TheEst andB-Glu systems forTripsacum were unscorable due to poor staining and resolution. TheAcp, Mdh, Pgm, andPhi isozyme systems were found to be satisfactory markers for differentiating between eastern gamagrass individuals as well as detectingTripsacum introgression in maize. The availability of useful isozyme systems which can simultaneously provide significant isozyme resolution of maize,Tripsacum and maize-Tripsacum backcross hybrids, on a single gel system, will be useful for the detection of marker assistedTripsacum introgression into maize. In addition, the identification of a set of variable biochemical markers should also assist breeding, selection and genetic manipulations in eastern gamagrass.The use of company names in this publication does not imply endorsement by the USDA-ARS, or the product names of criticism of similar ones not mentioned. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.     

Conserved sequence pattern in a wide variety of phosphoesterases.

A unique sequence pattern, designated the GD/GNH signature, was shown to be conserved in a wide variety of phosphoesterases. The enzymes containing this signature cleave phosphoester bonds in such different substrates as (1) phosphoserine and phosphothreonine in polypeptides; (2) bis(5'-nucleosidyl)-tetraphosphates; (3) nucleoside 5' phosphates; (4) 2',3'-cyclic nucleotide phosphates; (5) polynucleotides; (6) 2'-5' phosphodiesters in RNA (intron) lariats; (7) sphingomyelin; and (7) various phosphomonoesters. Two conserved acidic amino acid residues and a conserved histidine residue may be directly involved in phosphoester bond cleavage.     

Syk expression and novel function in a wide variety of tissues.

Syk protein-tyrosine kinase has been implicated in a variety of hematopoietic cell responses, in particular immunoreceptor signaling events that mediate diverse cellular responses including proliferation, differentiation, and phagocytosis. On the other hand, Syk exhibits a more widespread expression pattern in nonhematopoietic cells like fibroblasts, epithelial cells, breast tissue, hepatocytes, neuronal cells, and vascular endothelial cells and has been shown to be functionally important on these cell types. Thus, Syk appears to play a general physiological function in a wide variety of cells. In this article, we briefly review the current literature regarding the expression and novel function of Syk in various cells and tissues.     

Chromosome doubling and mode of reproduction of induced tetraploids of eastern gamagrass (Tripsacum dactyloides L.)

Eastern gamagrass, (Tripsacum dactyloides L.) is a perennial, warm-season grass that is being developed as a forage plant. Shoots were derived from callus initiated from immature embryos and immature inflorescences of diploid (2n=2x=36) gynomonoecious eastern gamagrass. These shoots were induced to microtiller in the presence of 3 mg/l benzyladenine. Amiprophosmethyl (10, 15, or 20 μm) was applied to 27 microtillers for 3–5 days to induce chromosome doubling. All 14 surviving plants were tetraploid, (2n=4x=72), as determined by flow cytometry or chromosome counts. These plants were morphologically normal and produced seed. Test crosses were made with a known diploid. Flow cytometry and chromosome counts showed that the progeny were triploid, proving that the induced tetraploids reproduce sexually. Received: 12 February 1997 / Revision received: 18 February 1998 / Accepted: 13 March 1998     

Biomass and seed yields of big bluestem, switchgrass, and intermediate wheatgrass in response to manure and harvest timing at two topographic positions

A principle attribute of perennial grasses for biomass energy is the potential for high yields on marginal lands. Objectives of this study were to compare biomass and seed production of intermediate wheatgrass ( Thinopyrum intermedium [Host] Barkworth and D.R. Dewey), big bluestem ( Andropogon gerardii Vitman), and switchgrass ( Panicum virgatum L.) as affected by harvest timing and manure application on two topographic positions (footslope and backslope). Footslope is the hillslope position that forms the inclined surface at the base of a slope and backslope forms the steepest, middle position of the hillslope. Grasses were harvested for biomass at anthesis (summer), after a killing frost (autumn), or the following spring after overwintering in the field. Seed was harvested at maturity during 2003 and 2004. Two rates of beef cattle ( Bos taurus L.) manure (target rates of 0 and 150 kg total-N ha⁻¹) were surface applied annually. Maximum annual biomass yield ranged from 4.4 to 5.2, 2.7 to 4.2, and 3.7 to 5.6 Mg ha⁻¹ for intermediate wheatgrass, big bluestem, and switchgrass, respectively. Biomass yields were not different between fall and spring harvest treatments. Biomass yields of big bluestem and switchgrass at the backslope position were 86% and 96% of biomass yields at the footslope position with normal precipitation, respectively. Manure application increased biomass yield approximately 30% during the second year on both topographic positions. The highest seed yield was obtained from intermediate wheatgrass, followed by switchgrass and big bluestem. Utilizing these management practices in our environment, it appears that switchgrass and big bluestem could be allowed to overwinter in the field without suffering appreciable loss of biomass.     

Sensing and modulation of invadopodia across a wide range of rigidities

Recent studies have suggested that extracellular matrix rigidity regulates cancer invasiveness, including the formation of cellular invadopodial protrusions; however, the relevant mechanical range is unclear. Here, we used a combined analysis of tissue-derived model basement membrane (BM) and stromal matrices and synthetic materials to understand how substrate rigidity regulates invadopodia. Urinary bladder matrix-BM (UBM-BM) was found to be a rigid material with elastic moduli of 3-8 MPa, as measured by atomic force microscopy and low-strain tensile testing. Stromal elastic moduli were ∼6-fold lower, indicating a more compliant material. Using synthetic substrates that span kPa–GPa moduli, we found a peak of invadopodia-associated extracellular matrix degradation centered around 30 kPa, which also corresponded to a peak in invadopodia/cell. Surprisingly, we observed another peak in invadopodia numbers at 2 GPa as well as gene expression changes that indicate cellular sensing of very high moduli. Based on the measured elastic moduli of model stroma and BM, we expected to find more invadopodia formation on the stroma, and this was verified on the stromal versus BM side of UBM-BM. These data suggest that cells can sense a wide range of rigidities, up into the GPa range. Furthermore, there is an optimal rigidity range for invadopodia activity that may be limited by BM rigidity.     

Effects of the pelleting conditions on chemical composition and sugar yield of corn stover,big bluestem,wheat straw,and sorghum stalk pellets

Pelleting of biomass can increase their bulk density and thus improve storability and reduce transportation costs. The objective of this research was to determine the effects of the pelleting conditions on chemical composition and fermentable sugar yield of the biomass. Corn stover, wheat straw, big bluestem, and sorghum stalks were used for this study. Dilute sulfuric acid was used for biomass pretreatment. Accellerase 1500™ was used for cellulose hydrolysis. Effects of mill screen size, die thickness, and L/D ratio of die on chemical compositions and sugar yield were determined. Glucan content of the biomass was positively affected by die thickness and negatively affected by mill screen size. Opposite trend was observed for xylan content. Wheat straw pellets had the highest sugar yield (92.5–94.1%) and big bluestem pellets had the lowest sugar yield (83.6–91.1%). Optimum pelleting condition is 6.5 mm screen size and 44.5 mm die thickness.     

Measurement of vitellogenin,a biomarker for exposure to oestrogenic chemicals,in a wide variety of cyprinid fish

There is increasing concern about man-made chemicals in the aquatic environment that mimic oestrogens because they may disrupt reproductive function. Vitellogenin, a precursor of egg-yolk in fish and other oviparous animals, may be used as a biomarker for “oestrogen” exposure. This study investigated the use of a radioimmunoassay developed to carp (Cyprinus carpio) vitellogenin to measure vitellogenin in other species of fish, especially cyprinids that would be of value for field and laboratory studies on oestrogenic xenobiotics. Of the nine families of fish studied, only vitellogenin from cyprinids (to which the carp belongs) showed good cross-reactivity in the carp vitellogenin radioimmunoassay. Vitellogenin from cyprinids native to Europe that cross reacted in the carp vitellogenin radioimmunoassay included: bream (Abramis brama), roach (Rutilus rutilus), rudd (Scardinius erythropthalmus), gudgeon (Gobio gobio) and minnow (Phoxinus phoxinus). Vitellogenin from cyprinids used widely in ecotoxicology that cross reacted in the carp vitellogenin radioimmunoassay included: fathead minnow (Pimephales promelas), zebrafish (Brachydanio rerio) and goldfish (Carassius auratus). In the cyprinids studies, the concentrations of vitellogenin in mature females were between a few hundred and a thousand microgram per millilitre. Concentrations of plasma vitellogenin in immature females were always greater than 200 ng·m^-1, whereas in males (with the exception of the fathead minnow) plasma vitellogenin concentrations were less than 20 ng·ml^-1 (and generally, much lower). The results suggest that the structure of vitellogenin is highly conserved within the cyprinid family and that the carp vitellogenin radioimmunoassay may be used to measure the concentrations of vitellogenin in plasma from a wide variety of cyprinids.     

Fitness effects of a photosynthetic mutation across contrasting environments

To test the hypothesis that variation in photosynthesis can cause differences in fitness, we compared wild‐type (WT) Amaranthus hybridus genotypes to those having a single‐gene mutation (R) that affects photosynthetic rate. By using light and water treatments, we generated a range of differences between WT and R genotypes in photosynthetic rate, growth and reproduction at three developmental stages. In two cases photosynthetic differences were in the expected direction (WT > R), they did not differ in others, and in one case the R genotype had a higher rate than the WT. Across light and water treatments, higher rates of photosynthesis were related to increases in specific leaf area, leaf nitrogen content and stomatal conductance relative to the other genotype. Differences between genotypes in growth and allocation paralleled those in photosynthesis; in treatments where photosynthetic rate differed between the genotypes (high light), growth and reproduction did as well. In high light, the effects of genotype on fitness were indirect with high‐water availability, but were direct with low‐water availability. When photosynthetic rate did not differ between genotypes (low light), neither did growth and reproduction. These results demonstrate that variation in photosynthesis can cause differences in growth and reproduction. Furthermore, resource availability can moderate the ways in which selection operates on photosynthetic traits.     

Genetic characterization of a reciprocal translocation present in a widely grown barley variety

Artificially induced translocation stocks have been used to physically map the barley genome; however, natural translocations are extremely uncommon in cultivated genotypes. Albacete is a barley variety widely grown in recent decades in Spain and carrying a reciprocal translocation which obviously does not affect its agronomical fitness. This translocation has been characterized by a combination of cytological and molecular genetic approaches. Firstly, recombination frequencies between markers on chromosomes 1H and 3H were estimated to determine the boundaries of the reciprocal interchange. Secondly, 1H-3H wheat barley telosome addition lines were used to assign selected markers to chromosome arms. Thirdly, fluorescence in situ hybridization (FISH) with rDNA probes (5S and 18S-5.8S-26S) and microsatellite probes [(ACT)(5), (AAG)(5) and (CAG)(5)] was used to determine the locations of the translocation breakpoints more precisely. Fourthly, fine-mapping of the regions around the translocation breakpoints was used to increase the marker density for comparative genomics. The results obtained in this study indicate that the translocation is quite large with breakpoints located on the long arms of chromosomes 1H and 3H, between the pericentromeric (AAG)(5) bands and above the (ACT)(5) interstitial distal bands, resulting in the reciprocal translocation 1HS.1HL-3HL and 3HS.3HL-1HL. The gene content around the translocation breakpoints could be inferred from syntenic relationships observed among different species from the grass family Poaceae (rice, Sorghum and Brachypodium) and was estimated at approximately 1,100 and 710 gene models for 1H and 3H, respectively. Duplicated segments between chromosomes Os01 and Os05 in rice derived from ancestral duplications within the grass family overlap with the translocation breakpoints on chromosomes 1H and 3H in the barley variety Albacete.