Metabolic control of tobacco pollination by sugars and invertases

Pollination in flowering plants is initiated by germination of pollen grains on stigmas followed by fast growth of pollen tubes representing highly energy-consuming processes. The symplastic isolation of pollen grains and tubes requires import of Suc available in the apoplast. We show that the functional coupling of Suc cleavage by invertases and uptake of the released hexoses by monosaccharide transporters are critical for pollination in tobacco (Nicotiana tabacum). Transcript profiling, in situ hybridization, and immunolocalization of extracellular invertases and two monosaccharide transporters in vitro and in vivo support the functional coupling in supplying carbohydrates for pollen germination and tube growth evidenced by spatiotemporally coordinated expression. Detection of vacuolar invertases in maternal tissues by these approaches revealed metabolic cross talk between male and female tissues and supported the requirement for carbohydrate supply in transmitting tissue during pollination. Tissue-specific expression of an invertase inhibitor and addition of the chemical invertase inhibitor miglitol strongly reduced extracellular invertase activity and impaired pollen germination. Measurements of (competitive) uptake of labeled sugars identified two import pathways for exogenously available Suc into the germinating pollen operating in parallel: direct Suc uptake and via the hexoses after cleavage by extracellular invertase. Reduction of extracellular invertase activity in pollen decreases Suc uptake and severely compromises pollen germination. We further demonstrate that Glc as sole carbon source is sufficient for pollen germination, whereas Suc is supporting tube growth, revealing an important regulatory role of both the invertase substrate and products contributing to a potential metabolic and signaling-based multilayer regulation of pollination by carbohydrates.Peer Reviewe

Geochemical detection of carbon dioxide in dilute aquifers

<p>Abstract</p> <p>Background</p> <p>Carbon storage in deep saline reservoirs has the potential to lower the amount of CO₂emitted to the atmosphere and to mitigate global warming. Leakage back to the atmosphere through abandoned wells and along faults would reduce the efficiency of carbon storage, possibly leading to health and ecological hazards at the ground surface, and possibly impacting water quality of near-surface dilute aquifers. We use static equilibrium and reactive transport simulations to test the hypothesis that perturbations in water chemistry associated with a CO₂gas leak into dilute groundwater are important measures for the potential release of CO₂to the atmosphere. Simulation parameters are constrained by groundwater chemistry, flow, and lithology from the High Plains aquifer. The High Plains aquifer is used to represent a typical sedimentary aquifer overlying a deep CO₂storage reservoir. Specifically, we address the relationships between CO₂flux, groundwater flow, detection time and distance. The CO₂flux ranges from 10³to 2 × 10⁶t/yr (0.63 to 1250 t/m²/yr) to assess chemical perturbations resulting from relatively small leaks that may compromise long-term storage, water quality, and surface ecology, and larger leaks characteristic of short-term well failure.</p> <p>Results</p> <p>For the scenarios we studied, our simulations show pH and carbonate chemistry are good indicators for leakage of stored CO₂into an overlying aquifer because elevated CO₂yields a more acid pH than the ambient groundwater. CO₂leakage into a dilute groundwater creates a slightly acid plume that can be detected at some distance from the leak source due to groundwater flow and CO₂buoyancy. pH breakthrough curves demonstrate that CO₂leaks can be easily detected for CO₂flux ≥ 10⁴t/yr within a 15-month time period at a monitoring well screened within a permeable layer 500 m downstream from the vertical gas trace. At lower flux rates, the CO₂dissolves in the aqueous phase in the lower most permeable unit and does not reach the monitoring well. Sustained pumping in a developed aquifer mixes the CO₂-affected water with the ambient water and enhances pH signal for small leaks (10³t/yr) and reduces pH signal for larger leaks (≥ 10⁴t/yr).</p> <p>Conclusion</p> <p>The ability to detect CO₂leakage from a storage reservoir to overlying dilute groundwater is dependent on CO₂solubility, leak flux, CO₂buoyancy, and groundwater flow. Our simulations show that the most likely places to detect CO₂are at the base of the confining layer near the water table where CO₂gas accumulates and is transported laterally in all directions, and downstream of the vertical gas trace where groundwater flow is great enough to transport dissolved CO₂laterally. Our simulations show that CO₂may not rise high enough in the aquifer to be detected because aqueous solubility and lateral groundwater transport within the lower aquifer unit exceeds gas pressure build-up and buoyancy needed to drive the CO₂gas upwards.</p

Development and psychometric evaluation of a new patient -reported outcome measure for stroke self -management: The Southampton Stroke Self - Management Questionnaire (SSSMQ).

BACKGROUND: Self-management is important to the recovery and quality of life of people following stroke. Many interventions to support self-management following stroke have been developed, however to date no reliable and valid outcome measure exists to support their evaluation. This study outlines the development and preliminary investigation of the psychometric performance of a newly developed patient-reported outcome measure (PROM) of self-management competency following stroke; the Southampton Stroke Self-Management Questionnaire (SSSMQ). METHODS: A convenience sample of 87 people who had had a stroke completed responses to the SSSMQ, the Stroke Self-Efficacy Questionnaire and the Stroke Impact Scale. Scaling properties were assessed using Mokken Scale Analysis. Reliability and construct validity were assessed using intra-class correlation coefficient (ICC), Mokken and Cronbach's reliability coefficients and Spearman rank order correlations with relevant measures. RESULTS: Mokken scaling refined the SSSMQ to 28 scalable items. Internal consistency reliability (Mokken r = 0.89) and test-retest reliability (ICC = 0.928) were excellent. Hypotheses of expected correlations with additional measures held, demonstrating good evidence for construct validity. CONCLUSIONS: Early findings suggest the Southampton Stroke Self-Management Questionnaire is a reliable and valid scale of self-management competency. The SSSMQ represents a potentially valid PROM for the evaluation of self-management following stroke

Differential effects of carbohydrates on arabidopsis pollen germination

Pollen germination as a crucial process in plant development strongly depends on the accessibility of carbon as energy source. Carbohydrates, however, function not only as a primary energy source, but also as important signaling components. In a comprehensive study, we analyzed various aspects of the impact of 32 different sugars on in vitro germination of Arabidopsis pollen comprising about 150 variations of individual sugars and combinations. Twenty-six structurally different mono-, di- and oligosaccharides, and sugar analogs were initially tested for their ability to support pollen germination. Whereas several di- and oligosaccharides supported pollen germination, hexoses such as glucose, fructose and mannose did not support and even considerably inhibited pollen germination when added to germination-supporting medium. Complementary experiments using glucose analogs with varying functional features, the hexokinase inhibitor mannoheptulose and the glucose-insensitive hexokinase-deficient Arabidopsis mutant gin2-1 suggested that mannose- and glucose-mediated inhibition of sucrose-supported pollen germination depends partially on hexokinase signaling. The results suggest that, in addition to their role as energy source, sugars act as signaling molecules differentially regulating the complex process of pollen germination depending on their structural properties. Thus, a sugar-dependent multilayer regulation of Arabidopsis pollen germination is supported, which makes this approach a valuable experimental system for future studies addressing sugar sensing and signaling.This study was supported by the Bayerisches Staatsministerium für Umwelt, Gesundheit und Verbraucherschutz, the SFB 56 and the DFG Graduiertenkolleg 1342 [to T.R.]; MINECO [contract No. CTQ2015-64425-C2-1-R to J.M.G.F]; the Junta de Andalucía [contract No. FQM2012-1467 to J.M.G.F]; the European Regional Development Funds (FEDER) [to J.M.G.F.]; the Ministry of Education, Youth and Sports of CR within the National Sustainability Program I (NPU I) [grant No. LO1415 to T.R.]; and by the Danish Council for Independent Research, Danish Ministry of Higher Education and Science to [Individual Postdoctoral Grant No. 4093-00255 to D.K.G.].Peer reviewe

A study of the mineralogical, hydrological and biogeochemical controls on drainage from waste rock at the Antamina Mine, Peru : an overview

A multi-scale study of solute release, transport, and attenuation mechanisms in waste rock under neutral drainage conditions is underway at the open-pit Cu-Zn-Mo Antamina mine in the Peruvian Andes. The objectives of the project are to better understand the mechanisms that control the fate of elements of concern, principally Zn, Mo, Cu, and As, and to develop field- and laboratory-derived scale-up relationships that provide a framework for prediction of waste-rock drainage quality at field scales and over long times. Five 36 m x 36 m x 11 m high instrumented experimental waste-rock piles have been constructed on site to provide insight into the hydrological and geochemical behavior of distinct combinations of waste rock under field conditions. Field cells constructed from 60 L barrels provide data on leaching behavior of the distinct rock types. Our results allow us to constrain the water balance, demonstrate that mixing of distinct waste-rock types may enhance attenuation of Zn and Mo in drainage and suggest that sulfide mineral oxidation may become O₂-limited in fine-grained reactive material.[All papers were considered for technical and language appropriateness by the organizing committee.]Non UBCUnreviewedOthe