High-sorgoleone producing sorghum genetic stocks suppress soil nitrification and N2O emissions better than low-sorgoleone producing genetic stocks

Plant and Soil - Rapid nitrification leads to loss of nitrogen (N) fertilizer in agricultural systems. Plant produced/derived biological nitrification inhibitors (BNIs) are an effective...     

Active aggregation among sexes in bean flower thrips (Megalurothrips sjostedti) on cowpea (Vigna unguiculata)

Male sexual aggregations are a common territorial, mating‐related or resource‐based, behaviour observed in diverse organisms, including insects such as thrips. The influence of factors such as plant substrate, time of day, and geographic location on aggregation of thrips is uncertain, therefore we monitored the dispersion of male and female bean flower thrips (BFT), Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), on cowpea, Vigna unguiculata (L.) Walp. (Fabaceae), over three cowpea growth stages and across three cowpea‐growing areas of Kenya. Our results indicated that for all the crop growth stages, the density of BFTs varied over the time of day, with higher densities at 10:00, 13:00, and 16:00 hours than at 07:00 hours. Thrips densities did not differ among blocks at the budding stage, but they did at peak flowering and podding stages. Dispersion indices suggested that both male and female BFTs were aggregated. Active male aggregation occurred only on green plant parts and it varied across blocks, crop stages, and locations. Similarly, active female aggregation was observed in peak flowering and podding stages. Such active aggregation indicates a semiochemical or behaviour‐mediated aggregation. Identification of such a semiochemical may offer new opportunities for refining monitoring and management strategies for BFT on cowpea, the most important grain legume in sub‐Saharan Africa.     

Bioactive ellagitannins from Cunonia macrophylla, an endemic Cunoniaceae from New Caledonia

Chemical study of Cunonia macrophylla, a New Caledonian Cunoniaceae, based on bioactive effects of a crude methanol extract of the leaves, detected bioactive tannins for the first time in this plant family. These ellagitannins have been identified as ellagic acid-4-O-beta-D-xylopyranoside (6), mallorepanin (3), mallotinic acid (1) along with corilagin (2), chebulagic acid (4), ellagic acid (5) and gallic acid (7) and have been shown to possess antimicrobial activity and to inhibit xanthine oxidase. Antimicrobial effects on bacterial human pathogens (Staphylococcus aureus, Corynebacterium accolans) and on a plant pathogen (Erwinia carotovora) as well as on a human pathogenic yeast (Candida albicans) were investigated. Activity is reported here for the first time for compounds 1, 3, 4 and 6. The inhibitory effects of all molecules against xanthine oxidase in relation to their structure was evaluated and compared. Compound 6 presented the best activity and seems to be of considerable interest for further studies.     

Evidence for the High Importance of Co-Morbid Factors in HFE C282Y/H63D Patients Cared by Phlebotomies: Results from an Observational Prospective Study

Despite type I haemochromatosis (HC) is mainly associated with the HFE C282Y/C282Y genotype, a second genotype -C282Y/H63D- has mostly been described in other patients. Its association with HC, apart from any associated co-morbid factors, remains unclear and complex to interpret for physicians. This study assesses the weight of this genotype and the role of co-morbid factors in the occurrence of iron overload. This prospective study included the C282Y/C282Y (n = 172) and C282Y/H63D (n = 58) patients enrolled in a phlebotomy program between 2004 and 2007 in a blood centre of western Brittany (Brest, France), where HC is frequent. We compared prevalence of these two genotypes, as well as patients’ profile regarding degree of iron overload and prevalence of co-morbid factors. First, we confirmed the obvious deficit of C282Y/H63D compound heterozygotes among patients cared by phlebotomies. This genotype was 3.0 times less frequent than the C282Y/C282Y genotype among those patients (18.9% vs. 56.0%) whereas it was 4.9 times more frequent in the general population (4.3% vs. 0.9%; p<0.0001). Despite a similar level of hyperferritinaemia, the C282Y/H63D patients who came to medical attention had a milder plasma iron overload, reflected by a lower transferrin saturation median (52.0% vs. 84.0%; p<0.0001). They also exhibited more frequently co-morbid factors, as heavy drinking (26.0% vs. 13.9%; p = 0.0454), overweight (66.7% vs. 39.4%; p = 0.0005) or both (21.3% vs. 2.6%; p<0.0001). Ultimately, they required a lower amount of iron removed to reach depletion (2.1 vs. 3.4 g; p<0.0001), clearly reflecting their lower tissue iron. This study confirms that H63D is a discrete genetic susceptibility factor whose expression is most visible in association with other co-factors. It highlights the importance of searching for co-morbidities in these diagnostic situations and of providing lifestyle and dietary advice.     

The carboxy-terminal C2-like domain of the α-toxin from Clostridium perfringens mediates calcium-dependent membrane recognition

The lethal, cytolytic α-toxin (phospholipase C) of Clostridium perfringens consists of two distinct modules: the larger N-terminal domain catalyses phospholipid hydrolysis, and its activity is potentiated by a smaller C-terminal domain. Calcium ions are essential for the binding of α-toxin to lipid films. Sixteen α-toxin variants with single amino acid substitutions in the C-terminal region were obtained using site-directed mutagenesis and T7 expression technology. Five of these variants showed reduced phospholipase C activity and were considerably less active than native α-toxin under calcium-limiting conditions. Replacement of Thr-272 by Pro diminished phospholipase C activity, severely affected haemolysis and platelet aggregation and perturbed a surface-exposed conformational epitope. The results of sequence comparisons and molecular modelling indicate that the C-terminal region probably belongs to the growing family of C₂β-barrel domains, which are often involved in membrane interactions, and that the functionally important substitutions are clustered at one extremity of the domain. The combined findings suggest that the C-terminal region of α-toxin mediates interactions with membrane phospholipids in a calcium-dependent manner. Mutations to this domain may account for the natural lack of toxicity of the α-toxin homologue, phospholipase C of Clostridium bifermentans .     

Liver stiffness measurement and biochemical markers in Senegalese chronic hepatitis B patients with normal ALT and high viral load

Background and Aims

Despite the high prevalence of chronic hepatitis B (CHB) in Africa, few studies have been performed among African patients. We sought to evaluate liver stiffness measurement by FibroScan® (LSM) and two biochemical scores (FibroTest®, Fibrometer®) to diagnose liver fibrosis in Senegalese CHB patients with HBV plasma DNA load ≥3.2 log₁₀ IU/mL and normal alanine aminotransferase (ALT) values.

Methods

LSM and liver fibrosis biochemical markers were performed on 225 consecutive HBV infected Senegalese patients with high viral load. Patients with an LSM range between 7 and 13 kPa underwent liver biopsy (LB). Two experienced liver pathologists performed histological grading using Metavir and Ishak scoring.

Results

225 patients were evaluated (84% male) and LB was performed in 69 patients, showing F2 and F3 fibrosis in 17% and 10% respectively. In these patients with a 7–13 kPa range of LSM, accuracy for diagnosis of significant fibrosis according to LB was unsatisfactory for all non-invasive markers with AUROCs below 0.70. For patients with LSM values below 7 kPa, FibroTest® (FT), and Fibrometer® (FM) using the cut-offs recommended by the test promoters suggested a fibrosis in 18% of cases for FT (8% severe fibrosis) and 8% for FM. For patients with LSM values greater than 13 kPa, FT, FM suggested a possible fibrosis in 73% and 70%, respectively.

Conclusion

In highly replicative HBV-infected African patients with normal ALT and LSM value below 13 kPa, FibroScan®, FibroTest® or Fibrometer® were unsuitable to predict the histological liver status of fibrosis.     

Natural transformation in the Ralstonia solanacearum species complex: number and size of DNA that can be transferred

Ralstonia solanacearum is a widely distributed phytopathogenic bacterium that is known to invade more than 200 host species, mainly in tropical areas. Reference strain GMI1000 is naturally transformable at in vitro and also in planta conditions and thus has the ability to acquire free exogenous DNA. We tested the ubiquity and variability of natural transformation in the four phylotypes of this species complex using 55 strains isolated from different hosts and geographical regions. Eighty per cent of strains distributed in all the phylotypes were naturally transformable by plasmids and/or genomic DNA. Transformability can be considered as a ubiquitous physiological trait in the R. solanacearum species complex. Transformation performed with two independent DNA donors showed that multiple integration events occurred simultaneously in two distant genomic regions. We also engineered a fourfold-resistant R. solanacearum GMI1000 mutant RS28 to evaluate the size of DNA exchanged during natural transformation. The results demonstrated that this bacterium was able to exchange large DNA fragments ranging from 30 to 90 kb by DNA replacement. The combination of these findings indicated that the natural transformation mechanism could be the main driving force of genetic diversification of the R. solanacearum species complex.     

Effects of three nickel salts on germinating seeds of Grevillea exul var. rubiginosa, an endemic serpentine Proteaceae

BACKGROUND AND AIMS: Serpentine soils are usually quite infertile, arid and toxic, mainly because they contain high levels of heavy metals such as Ni. The aim of the present work was to assess the effects of Ni on the germinating seeds of Grevillea exul var. rubiginosa, an endemic serpentine Proteaceae of New Caledonia. In addition, the distribution of macronutrients and the Ni levels in germinating seeds were examined. METHODS: Seeds were sown in glass Petri dishes and exposed to increasing concentrations of Ni (5 to 500 mg Ni L(-1)) using Ni chloride, Ni sulphate and Ni acetate. The germination percentage and root length were measured after 40 d. Longitudinal frozen sections of germinating seeds growing in the presence of Ni (500 mg L(-1) for all three salts) were used for X-ray microanalysis and X-ray elemental mapping using scanning electron microscopy (SEM). KEY RESULTS: Ni chloride resulted in the greatest reductions in germination and root growth, particularly at 500 mg L(-1), followed by Ni sulphate and Ni acetate. SEM images revealed Ca crystalline structures in the seed coat for all the samples. S/Ca and Mg/P/K/Mn were found to be distributed differently in Ni-treated samples, whereas they all followed the same pattern in the controls. For all three salts, the Ni added to the medium had accumulated in the seed coat, whereas the endosperm seemed to be devoid of Ni. CONCLUSIONS: It is assumed that the seed coat is able to reduce the amount of Ni entering the seed, and that a high level of Ni induced the mobilization of macronutrients.