The genetic basis for indole-diterpene chemical diversity in filamentous fungi

Indole-diterpenes are a structurally diverse group of secondary metabolites with a common cyclic diterpene backbone derived from geranylgeranyl diphosphate and an indole group derived from indole-3-glycerol phosphate. Different types and patterns of ring substitutions and ring stereochemistry generate this structural diversity. This group of compounds is best known for their neurotoxic effects in mammals, causing syndromes such as ‘ryegrass staggers’ in sheep and cattle. Because many of the fungi that synthesise these compounds form symbiotic relationships with plants, insects, and other fungi, the synthesis of these compounds may confer an ecological advantage to these associations. Considerable recent progress has been made on understanding indole-diterpene biosynthesis in filamentous fungi, principally through the cloning and characterisation of the genes and gene products for paxilline biosynthesis in Penicillium paxilli. Important insights into how the indole-diterpene backbone is synthesised and decorated have been obtained using P. paxilli mutants in this pathway. This review provides an overview of these recent developments.     

Genetic differentiation and the evolution of cooperation in chimpanzees and humans

It has been proposed that human cooperation is unique among animals for its scale and complexity, its altruistic nature and its occurrence among large groups of individuals that are not closely related or are even strangers. One potential solution to this puzzle is that the unique aspects of human cooperation evolved as a result of high levels of lethal competition (i.e. warfare) between genetically differentiated groups. Although between-group migration would seem to make this scenario unlikely, the plausibility of the between-group competition model has recently been supported by analyses using estimates of genetic differentiation derived from contemporary human groups hypothesized to be representative of those that existed during the time period when human cooperation evolved. Here, we examine levels of between-group genetic differentiation in a large sample of contemporary human groups selected to overcome some of the problems with earlier estimates, and compare them with those of chimpanzees. We find that our estimates of between-group genetic differentiation in contemporary humans are lower than those used in previous tests, and not higher than those of chimpanzees. Because levels of between-group competition in contemporary humans and chimpanzees are also similar, these findings suggest that the identification of other factors that differ between chimpanzees and humans may be needed to provide a compelling explanation of why humans, but not chimpanzees, display the unique features of human cooperation.     

Symptoms of nitrogen saturation in an aggrading forested watershed in western Maryland

The objective of this study was to evaluate the nitrogen (N) biogeochemistry of an 18–22 year old forested watershed in western Maryland. We hypothesized that this watershed should not exhibit symptoms of N saturation. This watershed was a strong source of nitrate (NO₃ ⁻) to the stream in all years, with a mean annual export of 9.5 kg N ha⁻¹ year⁻¹ and a range of 4.4–18.4 kg N ha⁻¹ year⁻¹. During the 2001 and 2002 water years, wet deposition of inorganic N was 9.0 kg N ha⁻¹ year⁻¹ and 6.3 kg N ha⁻¹ year⁻¹, respectively. Watershed N export rates in 2001 and 2002 water years were 4.2 kg N ha⁻¹ year⁻¹ and 5.3 kg N ha⁻¹ year⁻¹, respectively. During the wetter water years of 2003 and 2004, the watershed exported 15.0 kg N ha⁻¹ year⁻¹ and 18.4 kg N ha⁻¹ year⁻¹, rates that exceeded annual wet deposition of N by a factor of two (7.5 kg N ha⁻¹ year⁻¹ in 2003) and three (5.5 kg N ha⁻¹ year⁻¹ in 2004). Consistent with the high rates of N export, were high concentrations (2.1–3.3%) of N in foliage, wood (0.3%) and fine roots, low C:N ratios in the forest floor (17–24) and mineral soil (14), high percentages (83–96%) of the amount of mineralized N that was nitrified and elevated N concentrations (up to 3 mg N l⁻¹) in soil solution. Although this watershed contained a young aggrading forest, it exhibited several symptoms of N saturation commonly observed in more mature forests.     

Development of photochemical method for meniscal repair: a preliminary study

Visible light combined with naphthalimides has previously been shown to catalyze formation of physical bonds in avascular meniscal tissue. The first objective was to modify the existing in vitro testing method (i.e., adhesion testing using lap-jointed slices) to gain more sensitivity in detecting relative bonding strengths among candidate bonding agents. A repeated measures experimental design (RMED) was used to account for variability in properties among bovine menisci and was achieved by testing all treatments/controls on slices from each meniscus. Additionally, to make the method more clinically relevant in modeling a bucket-handle tear, the bovine meniscal slices were cut with collagen fibers parallel to the test slice's length. Peak stress was greater for the complete treatment group (light plus naphthalimide) than for the control or incomplete treatment groups (light only or napthalimide only). The second objective was to perform concentration and photoactivation time dose-response studies. In the concentration dose-response study, peak stress was greater for all treatments when compared with the control but not different among treatment groups; however, there was a trend of increased bonding strength with increased concentration. In the photoactivation time dose-response study, peak stress was greater for all treatments when compared with the control and greater for the 3-min treatment vs. the 6- and 9-min treatments. Peak stress was not different between the longer treatments. The RMED provided increased reproducibility and statistical sensitivity for detecting differences among treatments and will be used to test candidate bonding agents prior to in vivo testing.     

Market Perceptions and Opportunities for Native Plant Production on the Southern Colorado Plateau

Increases in revegetation activities have created a large demand for locally adapted native plant materials (NPM) in the southwestern United States. Currently, there is a minimal supply of local genotypes to meet this demand. We investigated the potential for the initiation of a native plant market in the southern Colorado Plateau. Through a literature search, interviews, and site visits, we identified existing native plant markets outside of the region as useful models to help initiate a regional market. We used web‐based surveys to identify and analyze current and future NPM needs and concerns. Survey results indicate that management policy strongly drives decisions regarding the use and purchase of NPM. From a demand perspective , lack of availability and cost of NPM has kept purchasing minimal, despite policy changes favoring the use of natives. For suppliers, further development of NPM is limited by inconsistent and unreliable demand and lack of production knowledge. The knowledge and tools necessary to initiate an NPM market are available, but inadequate funding sources and insufficient information sharing hinder its development. Communication among producers, land managers, buyers, and researchers, as well as partnerships with local growers, appear to be vital to initiating a functional market.     

Phylogenetics and taxonomy of the New World leafy spurges,Euphorbia section Tithymalus (Euphorbiaceae)

The 480 species of leafy spurges, Euphorbia subgenus Esula, represent the main temperate radiation in the large genus Euphorbia. This group is distributed primarily in temperate Eurasia, but with smaller, disjunct centres of diversity in the mountains of the Old World tropics, in temperate southern Africa and in the New World. The majority of New World diversity (32 species) occurs in a single section, section Tithymalus. We analysed sequences of the nrITS and plastid ndhF, trnH‐psbA, trnS‐trnG and trnD‐trnT regions to reconstruct the phylogeny of section Tithymalus and to examine the origins and diversification of the species native to the New World. Our results indicate that the New World species of section Tithymalus form a clade that is sister to the widespread, weedy E. peplus. The New World species fall into two primary groups: a ‘northern annual clade’ from eastern North America and a diverse clade of both annual and perennial species that is divided into three subgroups. Within the second group, there is a small ‘southern annual clade’ from Texas and northern Mexico, a perennial ‘Brachycera clade’ from the western United States and northern Mexico, and a perennial ‘Esuliformis clade’ from montane areas of Mexico, Guatemala, Honduras and the Caribbean island of Hispaniola. Ancestral state reconstructions indicate that the annual habit probably evolved in the ancestor of E. peplus and the New World clade, with a subsequent reversal to the perennial habit. In conjunction with this phylogenetic framework, the New World species of section Tithymalus are comprehensively reviewed. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 191–228.     

Conformational changes of yeast plasma membrane H(+)-ATPase during activation by glucose: role of threonine-912 in the carboxy-terminal tail

Yeast Pma1 H(+)-ATPase, which belongs to the P-type family of cation-transporting ATPases, is activated up to 10-fold by growth on glucose, and indirect evidence has linked the activation to Ser/Thr phosphorylation within the C-terminal tail. We have now used limited trypsinolysis to map glucose-induced conformational changes throughout the 100 kDa ATPase. In the wild-type enzyme, trypsin cleaves first at Lys-28 and Arg-73 in the extended N-terminal segment (sites T1 and T2); subsequent cleavages occur at Arg-271 between the A domain and M3 (site T3) and at Lys-749 or Lys-754 in the M6-M7 cytoplasmic loop (site T4). Activation by glucose leads to a striking increase in trypsin sensitivity. At the C-terminal end of the protein, the Arg- and Lys-rich tail is shielded from trypsin in membranes from glucose-starved cells (GS) but becomes accessible in membranes from glucose-metabolizing cells (GM). In the presence of orthovanadate, Lys-174 at the boundary between M2 and the A domain also becomes open to cleavage in GM but not GS samples (site T5). Significantly, this global conformational change can be suppressed by mutations at Thr-912, a consensus phosphorylation site near the C-terminus. Substitution by Ala at position 912 leads to a GS-like (trypsin-resistant) state, while substitution by Asp leads to a GM-like (trypsin-sensitive) state. Thus, the present results help to dissect the intramolecular movements that result in glucose activation.     

The effect of extended exposure to hypersaline conditions on the germination of five inland halophyte species

In order to determine how salinity and exposure time affect seed viability and germination, seeds of five halophytes, Atriplex prostrata, Hordeum jubatum, Salicornia europaea, Spergularia marina, and Suaeda calceoliformis were exposed to 3.0, 5.0, and 10.0% NaCl solutions for 30, 60, 90, 365, and 730 d. Recovery experiments in distilled water indicated significantly different species responses to salinity over time. Percentage germination and rate of germination in H. jubatum were dramatically reduced following extended exposure and all seeds exposed to 10% NaCl for > 1 yr failed to germinate. Spergularia marina seeds were stimulated following short-term exposure to 3% NaCl; however, germination was delayed and overall germination was significantly reduced with exposure time in the two higher salinity levels. Percentage germination in A. prostrata decreased over time, but salinity level was not related to this reduction. Germination of S. europaea and S. calceoliformis, the most salt-tolerant species being tested, was stimulated by exposure to high salinity. Both species had a significant increase in percentage germination and in the germination rate when compared to seeds germinated in distilled water. Baseline germination data from seeds placed in 0, 1, 2, and 3% NaCl solutions indicated that S. europaea and S. calceoliformis were the only species to germinate in the 3% NaCl solution. Spergularia marina failed to germinate in the 2% NaCl treatment, and germination of A. prostrata and H. jubatum was significantly reduced at this salinity level. It is concluded that prolonged exposure to saline solutions can inhibit or stimulate germination in certain species, and the resulting germination and recovery responses are related to the duration and intensity of their exposure to salt in their natural habitats.     

The use of soil extractants to estimate plant-available molybdenum and selenium in potentially toxic soils

Summary Uptake of Mo and Se by plants growing on soils with larger than normal concentrations of these elements cannot be predicted from soil content alone.Results of the chemical extraction of Mo and Se from soils in the laboratory have been compared with plant uptake of Mo and Se from the same soils in greenhouse experiments. Plant uptake of Mo and Se is correlated with the EDTA-extractable Mo and Se in the soil and uptake of Mo with the ammonium acetate-extractable soil.The role of pH, organic matter, and other soil properties are discussed with regard to Mo and Se availability and to the interpretation of results obtained by laboratory extractions.     

S100A8 and S100A9 in human arterial wall. Implications for atherogenesis

Atherogenesis is a complex process involving inflammation. S100A8 and S100A9, the Ca2+-binding neutrophil cytosolic proteins, are associated with innate immunity and regulate processes leading to leukocyte adhesion and transmigration. In neutrophils and monocytes the S100A8-S100A9 complex regulates phosphorylation, NADPH-oxidase activity, and fatty acid transport. The proteins have anti-microbial properties, and S100A8 may play a role in oxidant defense in inflammation. Murine S100A8 is regulated by inflammatory mediators and recruits macrophages with a proatherogenic phenotype. S100A9 but not S100A8 was found in macrophages in ApoE-/- murine atherosclerotic lesions, whereas both proteins are expressed in human giant cell arteritis. Here we demonstrate S100A8 and S100A9 protein and mRNA in macrophages, foam cells, and neovessels in human atheroma. Monomeric and complexed forms were detected in plaque extracts. S100A9 was strongly expressed in calcifying areas and the surrounding extracellular matrix. Vascular matrix vesicles contain high levels of Ca2+-binding proteins and phospholipids that regulate calcification. Matrix vesicles characterized by electron microscopy, x-ray microanalysis, nucleoside triphosphate pyrophosphohydrolase assay and cholesterol/phospholipid analysis contained predominantly S100A9. We propose that S100A9 associated with lipid structures in matrix vesicles may influence phospholipid-Ca2+ binding properties to promote dystrophic calcification. S100A8 and S100A9 were more sensitive to hypochlorite oxidation than albumin or low density lipoprotein and immunoaffinity confirmed S100A8-S100A9 complexes; some were resistant to reduction, suggesting that hypochlorite may contribute to protein cross-linking. S100A8 and S100A9 in atherosclerotic plaque and calcifying matrix vesicles may significantly influence redox- and Ca2+-dependent processes during atherogenesis and its chronic complications, particularly dystrophic calcification.