Fine genetic mapping of RXopJ4, a bacterial spot disease resistance locus from Solanum pennellii LA716

The RXopJ4 resistance locus from the wild accession Solanum pennellii (Sp) LA716 confers resistance to bacterial spot disease of tomato (S. lycopersicum, Sl) caused by Xanthomonas perforans (Xp). RXopJ4 resistance depends on recognition of the pathogen type III effector protein XopJ4. We used a collection of Sp introgression lines (ILs) to narrow the RXopJ4 locus to a 4.2-Mb segment on the long arm of chromosome 6, encompassed by the ILs 6-2 and 6-2-2. We then adapted or developed a collection of 14 molecular markers to map on a segregating F₂ population from a cross between the susceptible parent Sl FL8000 and the resistant parent RXopJ4 8000 OC₇. In the F₂ population, a 190-kb segment between the markers J350 and J352 cosegregated with resistance. This fine mapping will enable both the identification of candidate genes and the detection of resistant plants using cosegregating markers. The RXopJ4 resistance gene(s), in combination with other recently characterized genes and a quantitative trait locus (QTL) for bacterial spot disease resistance, will likely be an effective tool for the development of durable resistance in cultivated tomato.     

Trends in cation, nitrogen, sulfate and hydrogen ion concentrations in precipitation in the United States and Europe from 1978 to 2010: a new look at an old problem

Industrial emissions of SO₂ and NO_x, resulting in the formation and deposition of sulfuric and nitric acids, affect the health of both terrestrial and aquatic ecosystems. Since the mid-late 20th century, legislation to control acid rain precursors in both Europe and the US has led to significant declines in both SO₄–S and H⁺ in precipitation and streams. However, several authors noted that declines in streamwater SO₄–S did not result in stoichiometric reductions in stream H⁺, and suggested that observed reductions in base cation inputs in precipitation could lessen the effect of air pollution control on improving stream pH. We examined long-term precipitation chemistry (1978–2010) from nearly 30 sites in the US and Europe that are variably affected by acid deposition and that have a variety of industrial and land-use histories to (1) quantify trends in SO₄–S, H⁺, NH₄–N, Ca, and NO₃–N, (2) assess stoichiometry between H⁺ and SO₄–S before and after 1990, and (3) examine regional synchrony of trends. We expected that although the overall efforts of developed countries to reduce air pollution and acid rain by the mid-late 20th century would tend to synchronize precipitation chemistry among regions, geographically varied patterns of fossil fuel use and pollution control measures would produce important asynchronies among European countries and the United States. We also expected that control of particulate versus gaseous emission, along with trends in NH₃ emissions, would be the two most significant factors affecting the stoichiometry between SO₄–S and H⁺. Relationships among H⁺, SO₄–S, NH₄–N, and cations differed markedly between the US and Europe. Controlling for SO₄–S levels, H⁺ in precipitation was significantly lower in Europe than in the US, because (1) alkaline dust loading from the Sahara/Sahel was greater in Europe than the US, and (2) emission of NH₃, which neutralizes acidity upon conversion to NH₄ ⁺, is generally significantly higher in Europe than in the US. Trends in SO₄–S and H⁺ in precipitation were close to stoichometric in the US throughout the period of record, but not in Europe, especially eastern Europe. Ca in precipitation declined significantly before, but not after 1990 in most of the US, but Ca declined in eastern Europe even after 1990. SO₄–S in precipitation was only weakly related to fossil fuel consumption. The stoichiometry of SO₄–S and H⁺ may be explained in part by emission controls, which varied over time and among regions. Control of particulate emissions reduces alkaline particles that neutralize acid precursors as well as S-containing particulates, reducing SO₄–S and Ca more steeply than H⁺, consistent with trends in the northeastern US and Europe before 1990. In contrast, control of gaseous SO₂ emissions results in a stoichiometric relationship between SO₄–S and H⁺, consistent with trends in the US and many western European countries, especially after 1991. However, in many European countries, declining NH₃ emissions contributed to the lack of stoichiometry between SO₄–S and H⁺.Recent reductions in NO_x emissions have also contributed to declines in H⁺ in precipitation. Future changes in precipitation acidity are likely to depend on multiple factors including trends in NO_x and NH₃ emission controls, naturally occurring dust, and fossil fuel use, with significant implications for the health of both terrestrial and aquatic ecosystems.     

Reactive oxygen species generated in the presence of fine pyrite particles and its implication in thermophilic mineral bioleaching

In the tank bioleaching process, maximising solid loading and mineral availability, the latter through decreasing particle size, are key to maximising metal extraction. In this study, the effect of particle size distribution on bioleaching performance and microbial growth was studied through applying knowledge based on medical geology research to understand the adverse effects of suspended fine pyrite particles. Small-scale leaching studies, using pyrite concentrate fractions (106–75, 75–25, ?25 μm fines), were used to confirm decreasing performance with decreasing particle size (D ₅₀ <40 μm). Under equivalent experimental conditions, the generation of the reactive oxygen species (ROS), hydrogen peroxide and hydroxyl radicals from pyrite was illustrated. ROS generation measured from the different pyrite fractions was found to increase with increasing pyrite surface area loading (1.79–74.01 m² L^?1) and Fe²⁺ concentration (0.1–2.8 g?L^?1) in solution. The highest concentration of ROS was measured from the finest fraction of pyrite (0.85 mM) and from the largest concentration of Fe²⁺ (0.78 mM). No ROS was detected from solutions containing only Fe³⁺ under the same conditions tested. The potential of ROS to inhibit microbial performance under bioleaching conditions was demonstrated. Pyrite-free Sulfolobus metallicus cultures challenged with hydrogen peroxide (0.5–2.5 mM) showed significant decrease in both cell growth and Fe²⁺ oxidation rates within the concentration range 1.5–2.5 mM. In combination, the results from this study suggest that conditions of large pyrite surface area loading, coupled with high concentrations of dissolved Fe²⁺, can lead to the generation of ROS, resulting in oxidative stress of the microorganisms.     

From Dust to Ashes: The Challenges of Difference

By attending to ways in which middle-class wives in Yogyakarta, Java, describe negotiating sentiments among family members (including children, maids and husbands), this article argues that domestic relations in middle-class homes in Java have been importantly inflected by state rhetoric on gender propriety and market ideas of work. As a result, both middle-class women and maids have come to conceive of emotion work as part of an array of domestic obligations central to social reproduction.     

Early Bacteriopheophytin Reduction in Charge Separation in Reaction Centers of Rhodobacter sphaeroides

A question at the forefront of biophysical sciences is, to what extent do quantum effects and protein conformational changes play a role in processes such as biological sensing and energy conversion? At the heart of photosynthetic energy transduction lie processes involving ultrafast energy and electron transfers among a small number of tetrapyrrole pigments embedded in the interior of a protein. In the purple bacterial reaction center (RC), a highly efficient ultrafast charge separation takes place between a pair of bacteriochlorophylls: an accessory bacteriochlorophyll (B) and bacteriopheophytin (H). In this work, we applied ultrafast spectroscopy in the visible and near-infrared spectral region to Rhodobacter sphaeroides RCs to accurately track the timing of the electron on B_A and H_A via the appearance of the B_A and H_A anion bands. We observed an unexpectedly early rise of the H_A⁻ band that challenges the accepted simple picture of stepwise electron transfer with 3 ps and 1 ps time constants. The implications for the mechanism of initial charge separation in bacterial RCs are discussed in terms of a possible adiabatic electron transfer step between B_A and H_A, and the effect of protein conformation on the electron transfer rate.     

Foliar nutrients explain goldspotted oak borer,Agrilus auroguttatus,adult feeding preference among four California oak species

Adults of the invasive goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), consumed foliar weight in no‐choice feeding tests of, in descending order, California black oak Quercus kelloggii Newb., Engelmann oak, Quercus engelmannii Greene, coast live oak, Quercus agrifolia Née, and canyon live oak, Quercus chrysolepis Liebm. (Fagaceae). Furthermore, significantly more foliar area was consumed of Q. kelloggii than of Q. chrysolepis. In dual‐choice feeding tests with isolated leaf disks, A. auroguttatus consumed significantly more foliar weight and area of Q. kelloggii relative to the other three oak species, and more foliar weight of Q. agrifolia than of Q. chrysolepis. In dual‐choice feeding tests with leaves on small branches, A. auroguttatus consumed more foliar weight of Q. kelloggii than of Q. engelmannii and Q. agrifolia. Thus, multiple experiments suggested that adults of A. auroguttatus preferred the foliage of Q. kelloggii over that of the other three oak species, and among the other three species they did not appear to have a strong feeding preference. Factor analysis reduced the quantities of 13 foliar nutrients into two new variables (factor 1 and factor 2). Factor 1 was weighted heavily on the quantities of nitrogen, sulfur, phosphorus, potassium, zinc, and copper, whereas factor 2 was weighted heavily on the quantities of zinc, iron, and aluminum. Factor 1 varied by oak species, with Q. kelloggii having a higher factor 1 nutrient content than the other three species. Factor 2 response was higher in Q. kelloggii, Q. agrifolia, and Q. engelmannii than in Q. chrysolepis. The collective effects of four macronutrients (nitrogen, sulfur, phosphorus, and potassium) and two micronutrients (zinc and copper) suggest that these might be the nutrients directing preferential feeding of A. auroguttatus adults on the foliage of Q. kelloggii. Leaf toughness might also play an important role in feeding preference. Female A. auroguttatus did not show an ovipositional preference among the four oak species.     

Proposal to replace the illegitimate genus name Prescottia Jones et al. 2013 with the genus name Prescottella gen. nov. and to replace the illegitimate combination Prescottia equi Jones et al. 2013 with Prescottella equi comb. nov

Recently we proposed that Rhodococcus equi (Magnusson 1923) Goodfellow and Alderson 1977 be transferred to a novel genus, Prescottia, as Prescottia equi comb. nov. However, in accordance with Principle 2 and Rule 51b(4) of the Bacteriological Code (1990 Revision), the bacterial genus name Prescottia Jones et al. 2013 is deemed illegitimate as this name has been used previously for a plant genus within the family Orchidaceae. Consequently, a new genus name, Prescottella gen. nov. is proposed for the bacterial taxon and a new combination Prescottella equi comb. nov. is proposed for the type species.     

A spectrophotometric coupled enzyme assay to measure the activity of succinate dehydrogenase

Respiratory complex II (succinate:ubiquinone oxidoreductase) connects the tricarboxylic acid cycle to the electron transport chain in mitochondria and many prokaryotes. Complex II mutations have been linked to neurodegenerative diseases and metabolic defects in cancer. However, there is no convenient stoichiometric assay for the catalytic activity of complex II. Here, we present a simple, quantitative, real-time method to detect the production of fumarate from succinate by complex II that is easy to implement and applicable to the isolated enzyme, membrane preparations, and tissue homogenates. Our assay uses fumarate hydratase to convert fumarate to malate and uses oxaloacetate decarboxylating malic dehydrogenase to convert malate to pyruvate and to convert NADP⁺ to NADPH; the NADPH is detected spectrometrically. Simple protocols for the high-yield production of the two enzymes required are described; oxaloacetate decarboxylating malic dehydrogenase is also suitable for accurate determination of the activity of fumarate hydratase. Unlike existing spectrometric assay methods for complex II that rely on artificial electron acceptors (e.g., 2,6-dichlorophenolindophenol), our coupled assay is specific and stoichiometric (1:1 for succinate oxidation to NADPH formation), so it is suitable for comprehensive analyses of the catalysis and inhibition of succinate dehydrogenase activities in samples with both simple and complex compositions.     

Aberrant,ectopic expression of VEGF and VEGF receptors 1 and 2 in malignant colonic epithelial cells. Implications for these cells growth via an autocrine mechanism

Vascular endothelial growth factor A (referred to as VEGF) is implicated in colon cancer growth. Currently, the main accepted mechanism by which VEGF promotes colon cancer growth is via the stimulation of angiogenesis, which was originally postulated by late Judah Folkman. However, the cellular source of VEGF in colon cancer tissue; and, the expression of VEGF and its receptors VEGF-R1 and VEGF-R2 in colon cancer cells are not fully known and are subjects of controversy.