bluuebunny/crossref_metadata_2025_split huggingface dataset:
Substrate induction of siderophore transport in Bacillus subtilis mediated by a novel one‐component regulator
Authors: Gaballa Ahmed , Helmann John D. 
Published: September 2007

SummaryWhen iron is scarce, Bacillus subtilis expresses genes involved in the synthesis and uptake of the siderophore bacillibactin (BB) and uptake systems to pirate other microbial siderophores. Here, we demonstrate that transcriptional induction of the feuABCybbA operon, encoding the Fe–BB uptake system, is mediated by Btr (formerly YbbB), which is encoded by the immediately upstream gene. Btr contains an AraC‐type DNA binding domain fused to a substrate binding protein (SBP) domain related to FeuA, the SBP for Fe–BB uptake. When cells are iron‐limited, the Fur‐mediated repression of btr is relieved and Btr binds to a conserved direct repeat sequence adjacent to feuA to activate transcription. If BB is present, Btr further activates feuA expression. Btr binds with high affinity to both apo–BB and Fe–BB, and the resulting complex displays a significantly increased efficacy as a transcriptional activator relative to Btr alone. Btr can also activate transcription in response to the structurally similar siderophore enterobactin, although genetic analyses indicate that the two siderophores make distinct interactions with the Btr substrate binding domain. Thus, the FeuABC transporter is optimally expressed under conditions of iron starvation, when Fur‐mediated repression is relieved, and in the presence of its cognate substrate.
Developmentally regulated membrane glycoproteins sharing antigenicity with rhamnogalacturonan II are not detected in nodulated boron deficient Pisum sativum
Authors: REDONDO‐NIETO MIGUEL , PULIDO LUIS , REGUERA MARÍA , BONILLA ILDEFONSO , BOLAÑOS LUIS 
Published: September 2007

ABSTRACTThe peribacteroid membrane (PBM) of symbiosomes from pea root nodules developed in the presence of boron (+B) was labelled by anti‐rhamnogalacturonan II (RGII) (anti‐rhamnogalacturonan II pectin polysaccharide) antiserum. However, in nodules from plants grown at low boron (−B), anti‐RGII pectin polysaccharide did not stain PBMs. Given that RGII pectin binds to borate, and that symbiosomes differentiate aberrantly in −B nodules because of abnormal vesicle traffic, anti‐RGII pectin polysaccharide antigens were further analysed. Following electrophoresis and electroblotting, anti‐RGII pectin polysaccharide immunostained three bands in +B but not in −B nodule‐derived PBMs. A similar banding pattern was observed after the immunostaining of membrane fractions from uninfected roots, indicating that anti‐RGII pectin polysaccharide antigens are common to both peribacteroid and plasma membranes. Protease treatment of samples led to disappearance of anti‐RGII pectin polysaccharide labelling, indicating that the three immunostained bands correspond to proteins or glycoproteins. The immunochemical study of RGII antigen distribution during nodule development showed that it is strongly present on the PBM of dividing (undifferentiated) symbiosomes but progressively disappeared during symbiosome maturation. In B‐deficient nodules, PBMs were never decorated with RGII antigens, and there was an abnormal targeting of vesicles containing pectic polysaccharide (homogalacturanan) to cell membranes. Overall, these results indicate that RGII, boron and certain membrane (glyco)‐proteins may interact closely and function cooperatively in membrane processes associated with symbiosome division and general cell growth.
Molecular phenotyping of lignin‐modified tobacco reveals associated changes in cell‐wall metabolism, primary metabolism, stress metabolism and photorespiration
Authors: Dauwe Rebecca , Morreel Kris , Goeminne Geert , Gielen Birgit , Rohde Antje , Van Beeumen Jos , Ralph John , Boudet Alain‐Michel , Kopka Joachim , Rochange Soizic F. , Halpin Claire , Messens Eric , Boerjan Wout 
Published: September 2007

SummaryLignin is an important component of secondarily thickened cell walls. Cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) are two key enzymes that catalyse the penultimate and last steps in the biosynthesis of the monolignols. Downregulation of CCR in tobacco (Nicotiana tabacum) has been shown to reduce lignin content, whereas lignin in tobacco downregulated for CAD incorporates more aldehydes. We show that altering the expression of either or both genes in tobacco has far‐reaching consequences on the transcriptome and metabolome. cDNA‐amplified fragment length polymorphism‐based transcript profiling, combined with HPLC and GC–MS‐based metabolite profiling, revealed differential transcripts and metabolites within monolignol biosynthesis, as well as a substantial network of interactions between monolignol and other metabolic pathways. In general, in all transgenic lines, the phenylpropanoid biosynthetic pathway was downregulated, whereas starch mobilization was upregulated. CCR‐downregulated lines were characterized by changes at the level of detoxification and carbohydrate metabolism, whereas the molecular phenotype of CAD‐downregulated tobacco was enriched in transcript of light‐ and cell‐wall‐related genes. In addition, the transcript and metabolite data suggested photo‐oxidative stress and increased photorespiration, mainly in the CCR‐downregulated lines. These predicted effects on the photosynthetic apparatus were subsequently confirmed physiologically by fluorescence and gas‐exchange measurements. Our data provide a molecular picture of a plant’s response to altered monolignol biosynthesis.
Feasibility and cost–benefit of implementing pooled screening for HCVAg in small blood bank settings
Authors: Sarov B. , Novack L. , Beer N. , Safi J. , Soliman H. , Pliskin J. S. , Litvak E. , Yaari A. , Shinar E. 
Published: September 2007

summary To examine the accuracy, feasibility and benefits of screening for hepatitis C virus core antigen (HCVAg) using enzyme‐linked immunosorbent assay (ELISA) test in pools. Many countries cannot afford to test blood donations for hepatitis C using molecular methods. Screening individual units using the ELISA HCVAg test is an acceptable, yet still expensive, alternative, especially for small blood bank settings. This study evaluated the option of screening for HCVAg in pools. The sensitivity (Se) and specificity (Sp) of HCVAg in pools of three and six antibody‐negative samples were estimated and compared with polymerase chain reaction (PCR). The feasibility and cost–benefit of the assay was assessed on 960 routine samples collected at a hospital blood bank in Gaza.Based on results for 50 PCR‐positive pools and 50 and 110 PCR‐negative pools of three and six, the Se of testing in pools of three and six samples is 80–82% [95% confidence interval (CI): 66·3–91·4] and Sp ≥98% (95% CI: 89·4–100·0) compared with PCR. The incidence of antigen in donors in Gaza was 0·1% (95% CI: 0–0·56). Cost analyses suggested significant benefits from implementing screening blood donations for HCVAg when the incidence rate is >4·2/10 000, leading to reduction in the expenditures needed to treat patients infected with HCV.The risk of transfusion‐transmitted hepatitis C in resource‐deprived developing countries can be efficiently reduced by additional screening of antibody‐negative blood donations for HCVAg in pools of six.
Comparing after‐ripening response and germination requirements of Conyza canadensis and C. bonariensis (Asteraceae) through logistic functions
Authors: KARLSSON L M , MILBERG P 
Published: September 2007

SummaryGermination requirements and after‐ripening effects during one year of dry storage at 15/5 and 25/15°C (day/night) were compared for Conyza bonariensis and C. canadensis (Asteraceae). A logistic function was fitted to the results from tests over time in various incubation conditions, using three populations of each species as replicates. Time required for response to dry storage was measured by using a new method, the third derivative of the logistic function. Therefore, a point when major germination was achieved could be detected, without having to rely on maximum germination (which is uncertain), individual data points or any subjectively chosen limit. Fresh seeds of both species were dependent on light for germination and after‐ripening was mainly manifested by increasing germination in darkness. Low dormancy status and light requirement might indicate that soil cultivations should rapidly reduce the seedbanks of these species, although fecundity and wind dispersal will affect population levels. The species differed in their germination response, with C. bonariensis germinating at lower temperatures than C. canadensis. This seemingly counter‐intuitive result may explain the prevention of fatal germination of C. canadensis in cold conditions and its behaviour as a summer annual in northern climates, while C. bonariensis is restricted to warmer parts of the world.
Tumbleweeds in the Western Australian cropping system: seed dispersal characteristics of Salsola australis
Authors: BORGER C P D , WALSH M , SCOTT J K , POWLES S B 
Published: September 2007

Summary Salsola australis, like other agricultural weed species of the Salsola genus, produces a mobile seedbank. Aspects of this mobile seedbank were investigated in three field trials, including total seed production, rate of seed shedding, rate at which seeds lose germinability and the distance and directionality of plant movement. Total seed production was highly variable (ranging from 138 to 7734 seeds per plant), but was directly related to aboveground plant biomass at maturity. Following senescence, mature plants broke free of their root system and the wind driven plants moved considerable distances (1.6–1247.2 m). Half of the mobile plants moved <100 m, as they became entangled with other S. australis plants within the stand. Seed shedding commenced before the plants became mobile and increased with movement, but was also related to the aging and weathering processes experienced by stationary or mobile plants. All plants retained a proportion of their seed in spite of movement, weathering and ageing of the plants, although germinability of retained seed dropped to <2% after 2 months. Salsola australis engages in broad scale seed dispersal similar to that observed in other species of the Salsola genus, allowing this species to maintain a high rate of invasion and range expansion.
A review of non‐chemical weed control on hard surfaces
Authors: RASK A M , KRISTOFFERSEN P 
Published: September 2007

SummaryWeed control research to date has mainly focused on arable land, especially regarding herbicides, but also regarding non‐chemical methods. Some of these experiences can be applied to hard surface areas. However, weeds on hard surface areas cause problems that are different from those on arable land. Additionally, crop tolerance does not need to be considered when choosing an appropriate weed control method on these areas. The aim of this review is to describe current knowledge of weeds and weed control methods on hard surface areas and reveal potential ways of advancement. One of the shortcomings of non‐chemical weed control on hard surfaces thus far, is a lack of proper definition of efficiency of the weed control methods. To obtain effective control, more frequently repeated treatments are required than chemical weed management, thereby increasing the costs of labour and fuel. One way to reduce costs can be by adjusting the level of control to the required visual street quality. Weeds are adapted to the hard surface environment and may be less susceptible to certain control methods. This review indicates that for efficient weed control on hard surfaces there is a need for combining weed control techniques, applying sensors for detecting weeds, adapting the energy dose to type of weed flora and prevention of weeds by improved construction of new surfaces.
Are weed patches stable in location? Application of an explicitly two‐dimensional methodology
Authors: HEIJTING S , VAN DER WERF W , STEIN A , KROPFF M J 
Published: September 2007

SummaryField observations were made in three years continuous maize cultivation in the Netherlands to study the spatial pattern and stability of spatial pattern over time in agricultural weeds. Two‐dimensional correlograms were made, using data from single years, to characterise spatial correlation and pattern, while data from two different years were used to calculate correlation over space and time, to characterise the stability of pattern. Weeds that were able to attain high recruitment also exhibited the strongest spatial correlations. These weeds were Echinochloa crus‐galli, Chenopodium album, Chenopodium polyspermum and Solanum nigrum. Weeds that were less successful in attaining high densities in the maize rotation, also showed less spatial correlation. Wind dispersing Compositae, e.g. Taraxacum officinale, had spatially uncorrelated patterns. All weeds that showed spatial correlation also showed stability in space, except E. crus‐galli. The latter species showed marked population increase and the locations and extent of its patches changed over the years. Statistical interpretation of the data is discussed, as are potential consequences for site‐specific management and optimal sampling of weeds.
Challenges for herbicide resistance evolution and management: 50 years after Harper
Authors: NEVE P 
Published: September 2007

SummaryEvolved resistance to herbicides is a classic example of ‘evolution in action’. This paper calls for a greater integration of ‘evolutionary‐thinking’ into herbicide resistance research. This integration, it is argued, should lead weed scientists to become less focused on simply describing resistance and more driven towards a deeper understanding of the evolutionary forces that underpin resistance evolution. I have attempted in this short paper to initiate a debate into how this might be done. In the first instance, I have highlighted the widespread misunderstanding and mis‐measurement by weed scientists of fitness and fitness costs. I have also speculated on the potential for herbicide rotations to exacerbate resistance problems by selecting for generalist (metabolic) resistance. Finally, I have discussed in greater detail the contribution of herbicide rates to resistance evolution and have reported work conducted in Australia which has shown the potential for low herbicide doses to rapidly select for very high levels of resistance in Lolium rigidum. The controversial hypotheses and suggestions put forward need to be tested by field experimentation. They may prove to be unfounded or incorrect, but if they cause us to question and expand the current resistance paradigm they will have been useful.
Effects of three management strategies on the seedbank, emergence and the need for hand weeding in an organic arable cropping system
Authors: RIEMENS M M , GROENEVELD R M W , LOTZ L A P , KROPFF M J 
Published: September 2007

SummaryThe effects of three different weed management strategies on the required input of hand weeding in an arable organic farming system, the weed seedbank in the soil and the emerging weed seedling emergence were studied from 1996 to 2003. Strategies were based on population dynamic models and aimed for (1) control of weeds as carried out in standard organic farming practice, (2) control of all residual weeds that grow above the crop and (3) prevention of all weed seed return to the soil. Under all strategies, the size of the seedbank increased during the conversion from conventional to organic farming systems. The increase under strategy 3 was significantly smaller than the increase under the other strategies. From 1999 onwards, the weed densities in plots treated with strategy 3 became significantly lower than the weed densities in plots treated with the other strategies. The time needed for hand‐weeding required to prevent weed seed return, in addition to the time needed in standard organic farming practices, reduced during the course of the study. A management strategy aimed at the prevention of seed return (strategy 3) can reduce the size of the increase of the seedbank, which is usually observed after transition from conventional to organic farming. This study provides unique real‐world data that are essential for evaluating population dynamic models. The results may contribute to the development of weed management systems based on ‘no seed’ threshold strategies and to a further decrease in the dependence on herbicides.
Molecular and biochemical mechanisms of defence induced in pea by Rhizobium leguminosarum against Orobanche crenata
Authors: MABROUK Y , SIMIER P , DELAVAULT P , DELGRANGE S , SIFI B , ZOURGUI L , BELHADJ O 
Published: September 2007

Summary Orobanche species (broomrapes) are parasitic weeds which dramatically decrease the yields of many economically important dicotyledonous crops, including pea (Pisum sativum), in Mediterranean areas. Previously, we identified some Rhizobium leguminosarum strains, including P.SOM, which could both promote pea development and significantly reduce infection by Orobanche crenata, notably through induction of necrosis of attached parasites. In the present study, induced resistance against broomrape in the nodulated pea was shown to be associated with significant changes in rates of oxidative lipoxygenase (Lox) and phenylpropanoid/isoflavonoid pathways and in accumulation of derived toxins, including phenolics and pisatin (pea phytoalexin). Changes were followed for 5 weeks after inoculation and attack by Orobanche. In contrast to non‐inoculated plants or Orobanche only infected plants, polyphenoloxidase (PPO) activity and hydrogen peroxide content increased in response to bacteria inoculation indicating the involvement of oxidative processes. In parallel, the nodulated roots displayed high Lox activity related to the overexpression of the lox1 gene. Similarly, the expression of phenylalanine ammonia lyase (PAL) and 6a‐hydroxymaackiain 3‐O‐methyltransferase (Hmm6a) genes were induced early during nodule development, suggesting the central role of the phenylpropanoid/isoflavonoid pathways in the elicited defence. As a consequence, the derived products, phenolics and pisatin, accumulated in response to rhizobacteria and conferred mechanical and chemical barriers to the invading parasite. These results highlight the likely role of signalling pathways in induced resistance and suggest these mechanisms should be enhanced through integrated Orobanche management practices.
Are pre‐spraying growing conditions a major determinant of herbicide efficacy?
Authors: RIETHMULLER‐HAAGE I , BASTIAANS L , KEMPENAAR C , SMUTNY V , KROPFF MJ 
Published: September 2007

SummaryTo evaluate the effect of pre‐spraying growing conditions on herbicide efficacy, two years of experimentation were conducted in which Persicaria maculosa plants were exposed to different light intensities for 1–4 days before metribuzin treatment. Specific leaf area, rather than plant growth rate or plant size, was the only parameter that correlated well with herbicide efficacy in both years of experimentation. The negative relationship between the ED50 and the specific leaf area indicates that leaf characteristics might be an important determinant of herbicide efficacy, for instance through an effect on herbicide uptake. In the third year of experimentation this hypothesis was further investigated by raising six cohorts of weed plants at a 1‐week interval and thus exposing them to a range of weather conditions. Clear relationships between uptake and herbicide efficacy were found for a combination of four plant species (Solanum nigrum, Senecio vulgaris, Chenopodium album and Brassica napus) and two herbicides (phenmedipham and bentazone). For phenmedipham, uptake was negatively correlated with global radiation and positively correlated with relative humidity. For the herbicide bentazone the opposite was found. These results were not species‐specific. This study shows the importance of the sensitivity of herbicide × species combinations and indicates that pre‐spraying weather information is relevant for the development of reduced dose rate recommendations.
Suppression of Digitaria sanguinalis and Amaranthus palmeri using autumn‐sown glucosinolate‐producing cover crops in organically grown bell pepper
Authors: NORSWORTHY J K , MALIK M S , JHA P , RILEY M B 
Published: September 2007

SummaryExperiments were conducted to compare growth characteristics, biomass production and glucosinolate content of seven autumn‐planted glucosinolate‐producing cover crops that were terminated the following spring. The control of Digitaria sanguinalis and Amaranthus palmeri following cover crop incorporation into soil was characterised and fruit yields of bell pepper transplanted into cover crop‐amended soil were determined. Differences in glucosinolate concentration and composition were noted between cover crop roots and shoots and among cover crops. Total biomass production by cover crops ranged from 103 g m−2 for garden cress to 894 g m−2 for Indian mustard (F‐E75), but cover crop biomass was not correlated with D. sanguinalis and A. palmeri control. D. sanguinalis and A. palmeri control in bell pepper varied by cover crop. D. sanguinalis control by cover crops ranged from 38% to 79%, and A. palmeri control was 23% to 48% at 4 weeks after transplanting (WATP) bell pepper in 2004. D. sanguinalis control was positively correlated with total glucosinolate production, but A. palmeri control was not. D. sanguinalis control in 2005 ranged from 0% to 38% at 2 WATP. In the absence of weeds, cover crops did not negatively affect fruit yields which were often higher than in the absence of a cover crop. Glucosinolate‐producing cover crops are not a stand‐alone weed management strategy, but some will provide early season control of D. sanguinalis and A. palmeri without having a negative effect on transplanted bell pepper.
‘Balance’ is in the eye of the beholder: providing information to support informed choices in antenatal screening via Antenatal Screening Web Resource
Authors: Ahmed Shenaz , Bryant Louise , Hewison Jenny 
Published: September 2007

AbstractObjectives  The Antenatal Screening Web Resource (AnSWeR) was designed to support informed prenatal testing choices by providing balanced information about disability, based on the testimonies of disabled people and their families. We were commissioned by the developers to independently evaluate the website. This paper focused on how participants evaluated AnSWeR in terms of providing balanced information.Setting  West Yorkshire.Participants  A total of 69 people were drawn from three groups: health professionals, people with personal experience of tested‐for conditions (Down’s syndrome, cystic fibrosis and spina bifida) and people representing potential users of the resource.Method  Data were collected via focus groups and electronic questionnaires.Results  Participants believed that information about the experience of living with the tested‐for conditions and terminating a pregnancy for the conditions were important to support informed antenatal testing and termination decisions. However, there were differences in opinion about whether the information about the tested‐for conditions was balanced or not. Some people felt that the inclusion of photographs of people with the tested‐for conditions introduced biases (both positive and negative). Many participants were also of the opinion that AnSWeR presented insufficient information on termination of an affected pregnancy to support informed choice.Conclusion  This study highlighted the difficulty of designing ‘balanced’ information about tested‐for conditions and a lack of methodology for doing so. It is suggested that AnSWeR currently provides a counterbalance to other websites that focus on the medical aspects of disability. Its aim to provide ‘balanced’ information would be aided by increasing the number and range of case studies available on the website.