Changes in carbohydrate composition in wheat and pea seedlings induced by calcium deficiency

Wheat (Triticum aestivum L. cv Jubilar) seedlings were grown for 10 days in hydroponics with or without calcium. In the leaves, Ca deficiency caused the level of ethanol soluble carbohydrate to increase between 2-and 10-fold, enhanced dark respiration and decreased CO₂ fixation capacity. Sucrose was the major carbohydrate to accumulate in wheat roots.     

Regulation of Carbon Partitioning in Source and Sink Leaf Parts in Sweet Pepper (Capsicum annuum L.) Plants : Role of Fructose 2,6-Bisphosphate

Area expansion rate, partitioning of photosynthetically fixed carbon, and levels of fructose 2,6-bisphosphate (fru-2,6-P₂) were determined in individual parts of developing leaves of sweet pepper (Capsicum annuum L.). The base was rapidly expanding and allocated less carbon to sucrose synthesis in comparison to the leaf tip, where expansion had almost stopped. The change in leaf expansion rate and carbon partitioning happened gradually. During day time levels of fru-2,6-P₂ were consistently higher in the leaf base than in the leaf tip. Leaf expansion rate and carbon partitioning were closely related to day time levels of fru-2,6-P₂, suggesting that fru-2,6-P₂ is an important factor in adjustment of metabolism during sink-to-source transition of leaf tissue. The levels of fru-2,6-P₂ changed markedly after a dark-to-light transition in the leaf base, but not in the leaf tip, suggesting that regulatory systems based on fru-2,6-P₂ are different in sink and source leaf tissue. During the period upon dark-to-light transition the variations in level of fru-2,6-P₂ did not show a close correlation to changes in the carbon partitioning, until the metabolism had reached a steady state.     

Dynamics of extractable carbohydrates in Pisum sativum. III. The effect of IAA and temperature on content and translocation of carbohydrates in pea cuttings during rooting

The number of roots formed in cuttings of pea ( Pisum sativum L. cv. Alaska) was regulated both by the temperature and by IAA, whereas the time to the appearance of the first roots was regulated only by the temperature. Cuttings treated with 10^-3 M IAA had a smaller content of extractable carbohydrates than the control ones irrespective of the temperature. In the bases of cuttings rooted at 25°C the content of extractable carbohydrates was lower than in those rooted at 15°C. Cuttings treated with IAA showed up to elevenfold increase of extractable carbohydrates in the bases at day 3. This increase of soluble sugars was not correlated with the number of roots formed or the speed of rooting. It is concluded that IAA affects the accumulation of carbohydrates, and this is not connected with the rooting ability of the cuttings.     

Comparison of three Listeria monocytogenes strains in a guinea-pig model simulating food-borne exposure

Three different Listeria monocytogenes strains, LO28 (a laboratory strain with truncated InlA), 4446 (a clinical isolate) and 7291 (a food isolate), were compared in a guinea-pig model designed to mimic food-borne exposure. The objectives were (1) to verify the applicability of the animal model for distinguishing between Listeria with different virulence properties and (2) to explore whether it was possible to reduce the required number of animals by dosing with mixed cultures instead of monocultures. Consistent with in vitro observations of infectivity in Caco-2 cells, faecal densities and presence in selected organs were considerably lower for LO28 than for the other two strains. Additionally, the animal study revealed a difference in prevalence in faeces as well as in internal organs between the clinical isolate and the food isolate, which was not reproduced in vitro . Dosage with monocultures of Listeria strains gave similar results as dosage with a mixture of the three strains; thus, the mixed infection approach was a feasible way to reduce the number of animals needed for determination of listerial virulence.     

VGLUT2-dependent sensory neurons in the TRPV1 population regulate pain and itch

The natural response to itch sensation is to scratch, which relieves the itch through an unknown mechanism. Interaction between pain and itch has been frequently demonstrated, and the selectivity hypothesis of itch, based on data from electrophysiological and behavioral experiments, postulates the existence of primary pain afferents capable of repressing itch. Here, we demonstrate that deletion of vesicular glutamate transporter (VGLUT) 2 in a subpopulation of neurons partly overlapping with the vanilloid receptor (TRPV1) primary afferents resulted in a dramatic increase in itch behavior accompanied by a reduced responsiveness to thermal pain. The increased itch behavior was reduced by administration of antihistaminergic drugs and by genetic deletion of the gastrin-releasing peptide receptor, demonstrating a dependence on VGLUT2 to maintain normal levels of both histaminergic and nonhistaminergic itch. This study establishes that VGLUT2 is a major player in TRPV1 thermal nociception and also serves to regulate a normal itch response.     

Detecting sample misidentifications in genetic association studies

Genetic association studies require that the genotype data from a given person can be correctly linked to the phenotype data from the same person. However, sample misidentification errors sometimes happen, whereby the link becomes invalid for some of the subjects in a study. This can have substantial consequences in terms of power to detect truly associated variants. In family-based studies, Mendelian inconsistencies can be used to detect sample misidentification. Genome-wide association studies (GWAS), however, typically use unrelated individuals, making error detection more problematic. Here we present a method for identifying potential sample misidentifications in GWAS and other genetic association studies building on ideas from forensic sciences. A widely used ad-hoc method for error detection is to check if the sex of an individual matches its X-linked genotype. We generalize this idea to less stringent associations between known genotypes and phenotypes, and show that if several known associations are combined, the power to detect misidentifications increases substantially. Individuals with an unlikely set of phenotypes given their genotypes are flagged as potential errors. We provide analytical and simulation results comparing the odds that the genotype and phenotype are both from the same individual for different numbers of available genotype-p henotype associations and for different information content of the associations. Our method has good sensitivity and specificity with as few as ten moderately informative genotype-phenotype associations. We apply the method to GWAS data from the Danish National Birth Cohort.     

Senescence in oat leaf segments under hypobaric conditions

The physiological effects of storing plants under hypobaric conditions were studied using oat ( Avena sativa L. cv. Victory) leaf segments as a test system. The segments from seven day old plants were floated on water and stored in darkness at 12°C, 1.6 kPa or at 25°C, 6 kPa. Low temperature or hypobaric conditions delayed senescence, whereas the combination arrested the syndrome at an early stage. One of the effects of low pressure was to force the stomata open. The hormones abscisic acid and kinetin, which affect the stomatal aperture and also senescence, did not show any effect in hypobarically stored plant material. The stomata were forced open in darkness when the pressure was lower than 77 kPa and opening time was 8 h. The senescence syndrome in hypobarically stored segments developed similar to those treated with kinetin at 101 kPa.