Effects of waterlogging and drought on winter wheat and winter barley grown on a clay and a sandy loam soil

Summary The effects of winter waterlogging and a subsequent drought on the growth of winter barley and winter wheat have been examined. We used lysimeters containing soil monoliths with facilities to control the water table and a mobile shelter to control rainfall. Winter wheat was grown on a clay and on a sandy loam, but winter barley only on the clay soil. Lysimeters were either freely-drained during the winter or waterlogged with the water table 10 cm below the soil surface from 2 December until 31 March (that could occur by rainfall with a return period of 2 to 3 years). The lysimeters then were either irrigated so that the soil moisture deficit did not exceed 84 mm, or subjected to drought by limiting rainfall (equivalent to a 1 in 10 dry year in the driest area of England) so that the deficits reached maximum values of 150 mm in the clay and 159 mm in the sandy loam by harvest.Winter waterlogging restricted tillering and restricted the number of ears for all crops; grain yield of the winter barley was decreased by 219 g/m² (30%), and that of winter wheat by 170 g/m² (24%) and 153 g/m² (21% on the clay and sandy loam respectively.The drought treatment reduced the straw weight of winter barley by 75 g/m² (12%) but did not significantly depress the grain yield. For winter wheat on the clay, where the soil was freely-drained during the winter, drought depressed total shoot weight by 344 g/m² (17%) and grain weight by 137 g/m² (17%), but after winter waterlogging, drought did not further depress total or grain weight. In contrast, the winter wheat on the sandy loam was not significantly affected by drought.From these results, which are discussed in relation to other experiments in the United Kingdom, it seems that winter waterlogging is likely to cause more variation in the yield of winter barley and winter wheat than drought.     

The high-latitude terrestrial carbon sink: a model analysis

A dynamic, global vegetation model, hybrid v4.1 ( Friend et al. 1997 ), was driven by transient climate output from the UK Hadley Centre GCM (HadCM2) with the IS92a scenario of increasing atmospheric CO₂ equivalent, sulphate aerosols and predicted patterns of atmospheric N deposition. Changes in areas of vegetation types and carbon storage in biomass and soils were predicted for areas north of 50°N from 1860 to 2100. Hybrid is a combined biogeochemical, biophysical and biogeographical model of natural, potential ecosystems. The effect of periodic boreal forest fires was assessed by adding a simple stochastic fire model. Hybrid represents plant physiological and soil processes regulating the carbon, water and N cycles and competition between individuals of parameterized generalized plant types. The latter were combined to represent tundra, temperate grassland, temperate/mixed forest and coniferous forest. The model simulated the current areas and estimated carbon stocks in the four vegetation types. It was predicted that land areas above 50°N (about 23% of the vegetated global land area) are currently accumulating about 0.4 PgC y^?1 (about 30% of the estimated global terrestrial sink) and that this sink could grow to 0.8–1.0 PgC y^?1 by the second half of the next century and persist undiminished until 2100. This sink was due mainly to an increase in forest productivity and biomass in response to increasing atmospheric CO₂, temperature and N deposition, and includes an estimate of the effect of boreal forest fire, which was estimated to diminish the sink approximately by the amount of carbon emitted to the atmosphere during fires. Averaged over the region, N deposition contributed about 18% to the sink by the 2080 s. As expected, climate change (temperature, precipitation, solar radiation and saturation pressure deficit) and N deposition without increasing atmospheric CO₂ produced a carbon source. Forest areas expanded both south and north, halving the current tundra area by 2100. This expansion contributed about 30% to the sink by the 2090 s. Tundra areas which were not invaded by forest fluctuated from sink to source. It was concluded that a high latitude carbon sink exists at present and, even assuming little effect of N deposition, no forest expansion and continued boreal forest fires, the sink is likely to persist at its current level for a century.     

Liquid chromatographic analysis of prednisolone, prednisone and their 20-reduced metabolites in perfusion media

A reversed-phase liquid chromatographic assay was developed to quantitate prednisolone, prednisone and the 20α-dihydro and 20β-dihydro reduced metabolites of both parent compounds in tissue culture media from in vitro perfusions of the human placental lobule. Steroids were extracted from perfusate, using reversed-phase cartridges, with average recoveries of 95.2% or greater. The internal standard for the analyses was 6α-methylprednisolone. In this assay cortisol coelutes with prednisolone, however, no other significant interferences were found. Assay of each steroid was linear in the range 0–1 μg/ml. Intra-assay coefficients of variation were measured at 10 and 750 ng/ml with ranges of 3.4% (20α-dihydroprednisone) to 8.8% (20β-dihydroprednisolone) and 4.1% (20β-dihydroprednisone) to 8.8% (prednisone). The corresponding inter-assay coefficients of variation were 3.3% (20α-dihydroprednisone) to 9.1% (20β-dihydroprednisolone) and 1.9% (prednisolone) to 3.5% (prednisone). The analyses utilized two C₁₈ columns which were linked together and maintained at 40°C.     

Procedures allowing the transformation of a range of European elite wheat (Triticum aestivum L.) varieties via particle bombardment.

Ten current European wheat varieties were transformed at efficiencies ranging from 1-17% (mean 4% across varieties) following modifications in particle bombardment and tissue culture procedures. All plants surviving phosphinothricin selection were screened for uidA and bar gene activity, and for the presence of marker gene sequences by PCR analysis. A minimum of 35% plant 'escape' frequency was achieved with selection on 4 mg l(-1) gluphosinate ammonium after shoot initiation. Mean co-transformation frequency with various genes-of-interest was 66%. The estimated number of insertions of the uidA gene in 25 lines were; 1-2 in 32%, 3-5 in 52%, and 6-8 in 16% of lines. In T(1) progenies, marker genes segregated in a Mendelian fashion in 50% of 39 lines analysed, as determined by transgene activity assays. Based on PCR analysis, it appeared that in some lines the occurrence of distorted segregation was due to poor transmission of the transgenes.     

Ochratoxin A displaces claudins from detergent resistant membrane microdomains

Ochratoxin A (OchA) is a food-borne mycotoxin with multiple effects in vivo. Previously, we have demonstrated that the toxin can significantly impair the barrier function of the gut epithelial cell line, Caco-2. Barrier disruption involved loss of claudins 3 and 4, but not claudin 1 from the tight junction complex. In this study, we demonstrate for the first time, that OchA is able to remove claudins 3 and 4 from the detergent insoluble membrane microdomains associated with the tight junctions. However, cholesterol distribution within the microdomain was unaffected by the toxin. In addition, the thiol antioxidant, N-acetyl cysteine, preserved the microdomain localisation of claudins and also the barrier function of Caco-2 cells. This work suggests that OchA-mediated barrier toxicity is due to removal of claudins from detergent insoluble membrane microdomains. Moreover, loss of microdomain association may be due to oxidative events.     

Programming of adipose tissue miR-483-3p and GDF-3 expression by maternal diet in type 2 diabetes

Nutrition during early mammalian development permanently influences health of the adult, including increasing the risk of type 2 diabetes and coronary heart disease. However, the molecular mechanisms underlying such programming are poorly defined. Here we demonstrate that programmed changes in miRNA expression link early-life nutrition to long-term health. Specifically, we show that miR-483-3p is upregulated in adipose tissue from low-birth-weight adult humans and prediabetic adult rats exposed to suboptimal nutrition in early life. We demonstrate that manipulation of miR-483-3p levels in vitro substantially modulates the capacity of adipocytes to differentiate and store lipids. We show that some of these effects are mediated by translational repression of growth/differentiation factor-3, a target of miR-483-3p. We propose that increased miR-483-3p expression in vivo, programmed by early-life nutrition, limits storage of lipids in adipose tissue, causing lipotoxicity and insulin resistance and thus increasing susceptibility to metabolic disease.     

CO2 stabilization,climate change and the terrestrial carbon sink

A nonequilibrium, dynamic, global vegetation model, Hybrid v4.1, with a subdaily timestep, was driven by increasing CO₂ and transient climate output from the UK Hadley Centre GCM (HadCM2) with simulated daily and interannual variability. Three IPCC emission scenarios were used: (i) IS92a, giving 790 ppm CO₂ by 2100, (ii) CO₂ stabilization at 750 ppm by 2225, and (iii) CO₂ stabilization at 550 ppm by 2150. Land use and future N deposition were not included. In the IS92a scenario, boreal and tropical lands warmed 4.5 °C by 2100 with rainfall decreased in parts of the tropics, where temperatures increased over 6 °C in some years and vapour pressure deficits (VPD) doubled. Stabilization at 750 ppm CO₂ delayed these changes by about 100 years while stabilization at 550 ppm limited the rise in global land surface temperature to 2.5 °C and lessened the appearance of relatively hot, dry areas in the tropics. Present‐day global predictions were 645 PgC in vegetation, 1190 PgC in soils, a mean carbon residence time of 40 years, NPP 47 PgC y^?1 and NEP (the terrestrial sink) about 1 PgC y^?1, distributed at both high and tropical latitudes. With IS92a emissions, the high latitude sink increased to the year 2100, as forest NPP accelerated and forest vegetation carbon stocks increased. The tropics became a source of CO₂ as forest dieback occurred in relatively hot, dry areas in 2060–2080. High VPDs and temperatures reduced NPP in tropical forests, primarily by reducing stomatal conductance and increasing maintenance respiration. Global NEP peaked at 3–4 PgC y^?1 in 2020–2050 and then decreased abruptly to near zero by 2100 as the tropical source offset the high‐latitude sink. The pattern of change in NEP was similar with CO₂ stabilization at 750 ppm, but was delayed by about 100 years and with a less abrupt collapse in global NEP. CO₂ stabilization at 550 ppm prevented sustained tropical forest dieback and enabled recovery to occur in favourable years, while maintaining a similar time course of global NEP as occurred with 750 ppm stabilization. By lessening dieback, stabilization increased the fraction of carbon emissions taken up by the land. Comparable studies and other evidence are discussed: climate‐induced tropical forest dieback is considered a plausible risk of following an unmitigated emissions scenario.     

Cytochrome P450105D1 (CYP105D1) from Streptomyces griseus: heterologous expression, activity, and activation effects of multiple xenobiotics.

The open reading frame of CYP105D1, a soluble cytochrome P450 from Streptomyces griseus, was cloned behind the tac promoter of the bacterial expression vector pSPg1910L and expressed in Escherichia coli. The recombinant protein retained normal spectral characteristics having a Soret peak at 448 nm in the reduced carbon monoxide difference spectrum. CYP105D1 was active, obtaining reducing equivalents from endogenous E. coli ferredoxin and ferredoxin reductase redox partners present in E. coli. In vitro activity studies revealed CYP105D1 to catalyse the NADH- and NADPH-dependent oxidation of the xenobiotic substrates benzo[a]pyrene, erythromycin, warfarin, and testosterone. Furthermore, this activity could be stimulated in the presence of either alpha-benzoflavone or beta-benzoflavone in an analogous manner to that reported for mammalian P450 forms including human liver cytochrome P4503A4 (CYP3A4). The system produces an alternative to whole-cell biotransformation of xenobiotic for the production of drug metabolites and an experimental system for probing the structural features of a cytochrome P450 with a broad substrate range.