Antibiotic-induced DNA methylation changes in calluses of Arabidopsis thaliana

This study was carried out to determine the involvement of the antibiotic kanamycin, commonly used as a selective agent in transformation protocols, in the phenomenon of somaclonal variation. Both genetic and epigenetic events were looked for. Two complementary approaches were used to evaluate global methylation changes in the genome of callus derived from the leaves of Arabidopsis thaliana L.; immunolabelling using monoclonal-antibodies raised against 5-methylcytosine in order to define the relative abundance of methylated cytosine; the analysis of methylation-sensitive polymorphism technique (MSAP) to assess methylation changes at CCGG sequences. In addition, the same samples were analysed using AFLPs in order to determine the extent of genomic change with respect to callus grown in the absence of kanamycin and plants grown from seed. The use of kanamycin as a selective agent caused extensive methylation changes in the genome with both hyper- and hypomethylation events seen. However, the net result was genome-wide hypomethylation: this effect was dosage dependent; the higher the dose, the greater the effect. At the same time, sequence mutation was detected.     

A rainout shelter design for intercepting different amounts of rainfall

Field manipulative experiments represent a straightforward way to explore temporal relationships between annual precipitation and productivity. Water exclusion usually involves the use of rainout shelters, which are in general formed by a complete roof that intercepts 100% of the rainfall and require complicated mechanisms to move the shelter into place. The rainout-shelter design described here is a fixed-location shelter with a roof consisting of bands of transparent acrylic that blocks different amounts of rainfall while minimally affecting other environmental variables. We constructed thirty 3.76-m² shelters in an arid steppe near Río Mayo, Argentina (at 45°41'S, 70°16'W), to impose 30%, 55%, and 80% of rainfall interception. We tested the effectiveness of the design by collecting all the intercepted water in storage tanks and we evaluated changes in soil water content with the time domain reflectometry technique. We also measured soil water content in regular grids to assess the magnitude of the edge effect. We analysed the microclimate impact of the shelters by measuring photosynthetically active radiation and air and soil temperature inside and outside shelters. We did not detect significant differences between the observed and the expected rainfall interception for the 30% and 55% interception treatments but the 80% shelters intercepted 71% of incoming rainfall, which was significantly (P<0.05) lower than the expected value. Soil water content was significantly (P<0.05) higher in the control plots than in the plots with rainout shelter at all dates, except in January (summer). Radiation was not affected by the 30% interception treatment, but the roof with the largest number of acrylics bands (80% interception treatment) reduced incident radiation throughout the day by 10%. Air and soil temperatures were lower under than outside the shelters during the period of highest radiation but the opposite occurred with low radiation but with smaller differences. The two characteristics of the shelter, fixed design and low cost, allow for proper replication in space, which is required in ecological field experiments.     

Lethal Interpersonal Violence in the Middle Pleistocene

Evidence of interpersonal violence has been documented previously in Pleistocene members of the genus Homo, but only very rarely has this been posited as the possible manner of death. Here we report the earliest evidence of lethal interpersonal violence in the hominin fossil record. Cranium 17 recovered from the Sima de los Huesos Middle Pleistocene site shows two clear perimortem depression fractures on the frontal bone, interpreted as being produced by two episodes of localized blunt force trauma. The type of injuries, their location, the strong similarity of the fractures in shape and size, and the different orientations and implied trajectories of the two fractures suggest they were produced with the same object in face-to-face interpersonal conflict. Given that either of the two traumatic events was likely lethal, the presence of multiple blows implies an intention to kill. This finding shows that the lethal interpersonal violence is an ancient human behavior and has important implications for the accumulation of bodies at the site, supporting an anthropic origin.     

Social sustainability in trade and development policy

The International Journal of Life Cycle Assessment - Social sustainability may be assessed using a variety of methods and indicators, such as the social footprint, social impact assessment, or...     

Regional grassland productivity responses to precipitation during multiyear above‐ and below‐average rainfall periods

There is considerable uncertainty in the magnitude and direction of changes in precipitation associated with climate change, and ecosystem responses are also uncertain. Multiyear periods of above‐ and below‐average rainfall may foretell consequences of changes in rainfall regime. We compiled long‐term aboveground net primary productivity (ANPP) and precipitation (PPT) data for eight North American grasslands, and quantified relationships between ANPP and PPT at each site, and in 1–3 year periods of above‐ and below‐average rainfall for mesic, semiarid cool, and semiarid warm grassland types. Our objective was to improve understanding of ANPP dynamics associated with changing climatic conditions by contrasting PPT–ANPP relationships in above‐ and below‐average PPT years to those that occurred during sequences of multiple above‐ and below‐average years. We found differences in PPT–ANPP relationships in above‐ and below‐average years compared to long‐term site averages, and variation in ANPP not explained by PPT totals that likely are attributed to legacy effects. The correlation between ANPP and current‐ and prior‐year conditions changed from year to year throughout multiyear periods, with some legacy effects declining, and new responses emerging. Thus, ANPP in a given year was influenced by sequences of conditions that varied across grassland types and climates. Most importantly, the influence of prior‐year ANPP often increased with the length of multiyear periods, whereas the influence of the amount of current‐year PPT declined. Although the mechanisms by which a directional change in the frequency of above‐ and below‐average years imposes a persistent change in grassland ANPP require further investigation, our results emphasize the importance of legacy effects on productivity for sequences of above‐ vs. below‐average years, and illustrate the utility of long‐term data to examine these patterns.     

Ecosystem state shifts during long‐term development of an Amazonian peatland

The most carbon (C)‐dense ecosystems of Amazonia are areas characterized by the presence of peatlands. However, Amazonian peatland ecosystems are poorly understood and are threatened by human activities. Here, we present an investigation into long‐term ecohydrological controls on C accumulation in an Amazonian peat dome. This site is the oldest peatland yet discovered in Amazonia (peat initiation ca. 8.9 ka BP), and developed in three stages: (i) peat initiated in an abandoned river channel with open water and aquatic plants; (ii) inundated forest swamp; and (iii) raised peat dome (since ca. 3.9 ka BP). Local burning occurred at least three times in the past 4,500 years. Two phases of particularly rapid C accumulation (ca. 6.6–6.1 and ca. 4.9–3.9 ka BP), potentially resulting from increased net primary productivity, were seemingly driven by drier conditions associated with widespread drought events. The association of drought phases with major ecosystem state shifts (open water wetland–forest swamp–peat dome) suggests a potential climatic control on the developmental trajectory of this tropical peatland. A third drought phase centred on ca. 1.8–1.1 ka BP led to markedly reduced C accumulation and potentially a hiatus during the peat dome stage. Our results suggest that future droughts may lead to phases of rapid C accumulation in some inundated tropical peat swamps, although this can lead ultimately to a shift to ombrotrophy and a subsequent return to slower C accumulation. Conversely, in ombrotrophic peat domes, droughts may lead to reduced C accumulation or even net loss of peat. Increased surface wetness at our site in recent decades may reflect a shift towards a wetter climate in western Amazonia. Amazonian peatlands represent important carbon stores and habitats, and are important archives of past climatic and ecological information. They should form key foci for conservation efforts.     

Effects of several factors on the heat-shock-induced thermotolerance of Listeria monocytogenes.

The influence of the temperature at which Listeria monocytogenes had been grown (4 or 37 degrees C) on the response to heat shocks of different durations at different temperatures was investigated. For cells grown at 4 degrees C, the effect of storage, prior to and after heat shock, on the induced thermotolerance was also studied. Death kinetics of heat-shocked cells is also discussed. For L. monocytogenes grown at 37 degrees C, the greatest response to heat shock was a fourfold increase in thermotolerance. For L. monocytogenes grown at 4 degrees C, the greatest response to heat shock was a sevenfold increase in thermotolerance. The only survival curves of cells to have shoulders were those for cells that had been heat shocked. A 3% concentration of sodium chloride added to the recovery medium made these shoulders disappear and decreased decimal reduction times. The percentage of cells for which thermotolerance increased after a heat shock was smaller the milder the heat shock and the longer the prior storage.