RNAi-mediated suppression of isoprene emission in poplar transiently impacts phenolic metabolism under high temperature and high light intensities: a transcriptomic and metabolomic analysis

In plants, isoprene plays a dual role: (a) as thermo-protective agent proposed to prevent degradation of enzymes/membrane structures involved in photosynthesis, and (b) as reactive molecule reducing abiotic oxidative stress. The present work addresses the question whether suppression of isoprene emission interferes with genome wide transcription rates and metabolite fluxes in grey poplar (Populusxcanescens) throughout the growing season. Gene expression and metabolite profiles of isoprene emitting wild type plants and RNAi-mediated non-isoprene emitting poplars were compared by using poplar Affymetrix microarrays and non-targeted FT-ICR-MS (Fourier transform ion cyclotron resonance mass spectrometry). We observed a transcriptional down-regulation of genes encoding enzymes of phenylpropanoid regulatory and biosynthetic pathways, as well as distinct metabolic down-regulation of condensed tannins and anthocyanins, in non-isoprene emitting genotypes during July, when high temperature and light intensities possibly caused transient drought stress, as indicated by stomatal closure. Under these conditions leaves of non-isoprene emitting plants accumulated hydrogen peroxide (H2O2), a signaling molecule in stress response and negative regulator of anthocyanin biosynthesis. The absence of isoprene emission under high temperature and light stress resulted transiently in a new chemo(pheno)type with suppressed production of phenolic compounds. This may compromise inducible defenses and may render non-isoprene emitting poplars more susceptible to environmental stress

InterCarb: a community effort to improve interlaboratory standardization of the carbonate clumped isotope thermometer using carbonate standards

Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth-system processes. However, interlaboratory discrepancies in quantifying carbonate clumped isotope (Δ47) measurements persist, and their specific sources remain unclear. To address interlaboratory differences, we first provide consensus values from the clumped isotope community for four carbonate standards relative to heated and equilibrated gases with 1,819 individual analyses from 10 laboratories. Then we analyzed the four carbonate standards along with three additional standards, spanning a broad range of δ47 and Δ47 values, for a total of 5,329 analyses on 25 individual mass spectrometers from 22 different laboratories. Treating three of the materials as known standards and the other four as unknowns, we find that the use of carbonate reference materials is a robust method for standardization that yields interlaboratory discrepancies entirely consistent with intralaboratory analytical uncertainties. Carbonate reference materials, along with measurement and data processing practices described herein, provide the carbonate clumped isotope community with a robust approach to achieve interlaboratory agreement as we continue to use and improve this powerful geochemical tool. We propose that carbonate clumped isotope data normalized to the carbonate reference materials described in this publication should be reported as Δ47 (I-CDES) values for Intercarb-Carbon Dioxide Equilibrium Scale

Urban poverty, social exclusion and social housing finance: The case of PRODEL in Nicaragua

As Earth cooled through the eclogite transition thick-crust tectonics was replaced by delamination, plate tectonics and deep irreversible subduction. Oceanic crust (OC) is not a conveyor belt; it is replaced by material displaced out of the transition zone (TZ) by slabs. Delaminated crust is hotter and may be part of a short, shallow “subterranean” cycle (“eclogite engine"). Deep subduction is intermittent and started late in Earth history; the amount of subducted OC has therefore been overestimated. It can easily be stored in the TZ. MORB is colder and denser at depth than LCC eclogite. Today the mantle is digesting OC–irreversible plate tectonics–but is regurgitating former lower continental crust (LCC) and restites, which are buoyant at ambient temperatures

Absolute speleo-thermometry, using clumped isotope measurements to correct for kinetic isotope fractionations induced by CO_2 degassing

Assuming that a given speleothem precipitates near thermodynamic equilibrium, quantitative interpretation of its ^(18)O record in terms of physical parameters is generally hampered by the lack of robust methods for separating isotopic variations due to paleo-temperatures and those reflecting source water composition. Moreover, in many settings it appears likely that speleothems form out of equilibrium, due to kinetic isotopic fractionation caused by rapid CO_2 degassing, which further detracts from the reliability of paleo-environmental reconstructions

The end-Permian mass extinction: A rapid volcanic CO2 and CH4 – climatic catastrophe

The end of the Permian was a time of crisis that culminated in the Earth's greatest mass extinction. There is much speculation as to the cause for this catastrophe. Here we provide a full suite of high-resolution and coeval geochemical results (trace and rare earth elements, carbon, oxygen, strontium and clumped isotopes) reflecting ambient seawater chemistry and water quality parameters leading up to the end-Permian crisis. Preserved brachiopod low-Mg calcite-based seawater chemistry, supplemented by data from various localities, documents a sequence of interrelated primary events such as coeval flows of Siberian Trap continental flood basalts and emission of carbon dioxide leading to warm and extreme Greenhouse conditions with sea surface temperatures (SST) of ~36 °C for the Late Permian. Although anoxia has been advanced as a cause for the mass extinction, most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling, but not a general cause. Instead, we suggest that renewed and increased end-Permian Siberian Trap volcanic activity, about 2000 years prior to the extinction event, released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extremeglobal warming and increased continentalweathering. Eventually, these rapidly discharged greenhouse gas emissions, less than 1000 years before the event, ushered in a global Hothouse period leading to extreme tropical SSTs of ~39 °C and higher. Based on these sea surface temperatures, atmospheric CO2 concentrations were about 1400 ppmv and 3000 ppmv for the Late and end-Permian, respectively. Leading up to the mass extinction, there was a brief interruption of the global warming trend when SST dropped, concurrent with a slight, but significant recovery in biodiversity in thewestern Tethys. It is possible that emission of volcanic sulphate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the Permian. After aerosol deposition, global warming resumed and the biotic decline proceeded, and was accompanied by suboxia, in places of the surface ocean which culminated in the greatest mass extinction in Earth histor

The end-Permian mass extinction : a rapid volcanic CO2 and CH4 – climatic catastrophe

The end of the Permian was a time of crisis that culminated in the Earth\u2019s greatest mass extinction. There is much speculation as to the cause for this catastrophe. We provide a full suite of high-resolution and coeval chemical results (trace and rare earth elements, carbon, oxygen, strontium and clumped isotopes) reflecting ambient seawater chemistry and water quality parameters leading up to the end \u2013 Permian crisis. Preserved brachiopod low-Mg calcite-based seawater chemistry, supplemented by data from various localities, documents a sequence of interrelated primary events such as coeval flows of Siberian Trap continental flood basalts and emission of carbon dioxide leading to warm and extreme Greenhouse conditions with sea surface temperatures (SST) of ~ 36\ub0C for the Late Permian, and followed by increased continental weathering. Although anoxia has been touted as a cause for the mass extinction, most biotic and geochemical evidence suggests that it was briefly relevant during the early phase of the event and in areas of upwelling, but not a cause of it. Instead, renewed and increased end of the Permian Siberian Trap volcanic activity, about 2,000 years prior to the event, released massive amounts of carbon dioxide and aided by methane emissions triggered extreme global warming and continental acid precipitation. Eventually, these rapidly discharged greenhouse gas emissions, less than 1,000 years before the event, ushered in a global Hothouse period leading to extreme tropical SSTs of ~ 39\ub0C and higher. Based on actual sea surface temperatures, atmospheric CO2 concentrations were about 1400 ppmv and 3000 ppmv for the Late and end \u2013 Permian, respectively. The most elevated atmospheric CO2 level, about 1,500 years before the end \u2013 Permian event, lead to increased acid precipitation and triggered massive continental weathering and soil erosion. Leading up to the mass extinction, there was a brief interruption of the global warming trend when SST dropped by about 5\ub0C concurrent with a slight but significant recovery in biodiversity in the western Tethys. It is postulated that emission of volcanic sulphate aerosols brought about the brief cooling just after the onset of intensified warming during the end of the Permian. With aerosol deposition, global warming resumed and the biotic decline proceeded, and was accompanied by collapse of the thermohaline circulation and suboxia, in places, of the surface ocean, destabilization of marine and terrestrial foodchains, in part through enhanced acid precipitation and continental weathering-erosion, and eventual ecosystem collapse accelerated by hypercapnia during the end of the Permian, culminating in the greatest mass extinction in Earth history

Defining an absolute reference frame for ‘clumped’ isotope studies of CO_2

We present a revised approach for standardizing and reporting analyses of multiply substituted isotopologues of CO_2 (i.e., ‘clumped’ isotopic species, especially the mass-47 isotopologues). Our approach standardizes such data to an absolute reference frame based on theoretical predictions of the abundances of multiply-substituted isotopologues in gaseous CO_2 at thermodynamic equilibrium. This reference frame is preferred over an inter-laboratory calibration of carbonates because it enables all laboratories measuring mass 47 CO_2 to use a common scale that is tied directly to theoretical predictions of clumping in CO_2, regardless of the laboratory’s primary research field (carbonate thermometry or CO_2 biogeochemistry); it explicitly accounts for mass spectrometric artifacts rather than convolving (and potentially confusing) them with chemical fractionations associated with sample preparation; and it is based on a thermodynamic equilibrium that can be experimentally established in any suitably equipped laboratory using commonly available materials. By analyzing CO_2 gases that have been subjected to established laboratory procedures known to promote isotopic equilibrium (i.e., heated gases and water-equilibrated CO_2), and by reference to thermodynamic predictions of equilibrium isotopic distributions, it is possible to construct an empirical transfer function that is applicable to data with unknown clumped isotope signatures. This transfer function empirically accounts for the fragmentation and recombination reactions that occur in electron impact ionization sources and other mass spectrometric artifacts. We describe the protocol necessary to construct such a reference frame, the method for converting gases with unknown clumped isotope compositions to this reference frame, and suggest a protocol for ensuring that all reported isotopic compositions (e.g., Δ_(47) values; Eiler and Schauble, 2004 Eiler, 2007) can be compared among different laboratories and instruments, independent of laboratory-specific analytical or methodological differences. We then discuss the use of intra-laboratory secondary reference frames (e.g., based on carbonate standards) that can be more easily used to track the evolution of each laboratory’s empirical transfer function. Finally, we show inter-laboratory reproducibility on the order of ±0.010 (1σ) for four carbonate standards, and present revised paleotemperature scales that should be used to convert carbonate clumped isotope signatures to temperature when using the absolute reference frame described here. Even when using the reference frame, small discrepancies remain between two previously published synthetic carbonate calibrations. We discuss possible reasons for these discrepancies, and highlight the need for additional low temperature (<15 °C) synthetic carbonate experiments

The end‐Permian mass extinction: A rapid volcanic CO2 and CH4‐climatic catastrophe

The end of the Permian was a time of crisis that culminated in the Earth's greatest mass extinction. There is much speculation as to the cause for this catastrophe. Here we provide a full suite of high-resolution and coeval geochemical results (trace and rare earth elements, carbon, oxygen, strontium and clumped isotopes) reflecting ambient seawater chemistry and water quality parameters leading up to the end‐Permian crisis. Preserved brachiopod low-Mg calcite-based seawater chemistry, supplemented by data from various localities, documents a sequence of interrelated primary events such as coeval flows of Siberian Trap continental flood basalts and emission of carbon dioxide leading to warm and extreme Greenhouse conditions with sea surface temperatures (SST) of ~36 °C for the Late Permian. Although anoxia has been advanced as a cause for the mass extinction, most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling, but not a general cause. Instead, we suggest that renewed and increased end‐Permian Siberian Trap volcanic activity, about 2000 years prior to the extinction event, released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extremeglobal warming and increased continentalweathering. Eventually, these rapidly discharged greenhouse gas emissions, less than 1000 years before the event, ushered in a global Hothouse period leading to extreme tropical SSTs of ~39 °C and higher. Based on these sea surface temperatures, atmospheric CO2 concentrations were about 1400 ppmv and 3000 ppmv for the Late and end‐Permian, respectively. Leading up to the mass extinction, there was a brief interruption of the global warming trend when SST dropped, concurrent with a slight, but significant recovery in biodiversity in the western Tethys. It is possible that emission of volcanic sulfate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the Permian. After aerosol deposition, global warming resumed and the biotic decline proceeded, and was accompanied by suboxia, in places of the surface ocean which culminated in the greatest mass extinction in Earth history