Precipitation minus evaporation over continents is the freshwater flux which can be sustainably exploited by mankind. Over a catchment and longer time periods, this flux is also the amount of water ...which flows into the ocean. An essential question for semi-arid areas of the world is how well this freshwater flux can be estimated and predicted to evolve under climate change and human water use. Knowing this flux is thus an essential element in regional water resources management. Here we examine this question over the catchment of the Mediterranean Sea. Using a novel data assimilation methodology that incorporates observed discharges of rivers in a land surface model, new estimates of the freshwater flux to the Mediterranean Sea for the period 1980-2013 are proposed. We find that more freshwater (40-60%) flows into the sea than previously estimated. The hypothesis we advance is that previous estimates have underestimated the discharges of the large number of unmonitored coastal basins and neglected submarine ground water flows. The proposed error bars on the estimate indicate that the degrading river gauging station network limits our ability to monitor this branch of the water cycle reliably. Nevertheless, the uncertainty is small enough to allow the identification of regions in which non-climatic decreases in the freshwater flows exist over the period.
Steroid hormones are essential in stress response, immune system regulation, and reproduction in mammals. Steroids with 3-oxo-Δ
structure, such as testosterone or progesterone, are catalyzed by ...steroid 5α-reductases (SRD5As) to generate their corresponding 3-oxo-5α steroids, which are essential for multiple physiological and pathological processes. SRD5A2 is already a target of clinically relevant drugs. However, the detailed mechanism of SRD5A-mediated reduction remains elusive. Here we report the crystal structure of PbSRD5A from Proteobacteria bacterium, a homolog of both SRD5A1 and SRD5A2, in complex with the cofactor NADPH at 2.0 Å resolution. PbSRD5A exists as a monomer comprised of seven transmembrane segments (TMs). The TM1-4 enclose a hydrophobic substrate binding cavity, whereas TM5-7 coordinate cofactor NADPH through extensive hydrogen bonds network. Homology-based structural models of HsSRD5A1 and -2, together with biochemical characterization, define the substrate binding pocket of SRD5As, explain the properties of disease-related mutants and provide an important framework for further understanding of the mechanism of NADPH mediated steroids 3-oxo-Δ
reduction. Based on these analyses, the design of therapeutic molecules targeting SRD5As with improved specificity and therapeutic efficacy would be possible.
Terrestrial plants must cope with drought stress to survive. Under drought stress, plants accumulate the phytohormone abscisic acid (ABA) by increasing its biosynthesis and decreasing its catabolism. ...However, the regulatory pathways controlling ABA catabolism in response to drought remain largely unclear. Here, we report that the flowering repressor SHORT VEGETATIVE PHASE (SVP) is induced by drought stress and associates with the promoter regions of the ABA catabolism pathway genes CYP707A1, CYP707A3 and AtBG1, causing decreased expression of CYP707A1 and CYP707A3 but enhanced expression of AtBG1 in Arabidopsis leaves. Loss-of-function mutations in CYP707A1 and CYP707A3 or overexpression of AtBG1 could rescue the drought-hypersensitive phenotype of svp mutant plants by increasing cellular ABA levels. Collectively, our results suggest that SVP is a central regulator of ABA catabolism and that a regulatory pathway involving SVP, CYP707A1/3, and AtBG1 plays a critical role in plant response to water deficit and plant drought resistance.
This study reports that the flowering repressor SVP is a central regulator of ABA catabolism by regulating the expression of the ABA catabolism pathway genes CYP707A1, CYP707A3 and AtBG1. Loss-of-function mutations in CYP707A1 and CYP707A3 or overexpression of AtBG1 can rescue the drought-hypersensitive phenotype of svp mutant plants by increasing cellular ABA levels. The results suggest that a regulatory pathway involving SVP, CYP707A1/3, and AtBG1 plays a critical role in plant response to water deficit and plant drought resistance.
In this study, a novel three-dimensional DEM-CFD numerical method was used to simulate the void fraction, pressure drop, velocity, and local flow in the packed bed under the small ...column-to-particle-diameter (
D
/
d
) ratios. The pseudo-continuum model method is used in the interior of particles, and for the simulation of the fluid outside the particles, the models are established based on DEM to avoid the wall effect. The simulation results of void fraction and pressure drop show that the void fractions generated by the DEM method are consistent with the ones calculated from the empirical correlations; and the empirical correlations used for pressure drop in this work are basically consistent with the results of the pressure drop predicted by DEM-CFD method. The simulation results of velocity and local flow show that velocity distribution is related to the void fraction distribution; the radial velocity distribution depends mainly on the structure of the packed bed and is independent of the inlet velocity; and the velocity uniformities of fluid flow are improved with the increasing of
D
/
d
ratio.
Convection-permitting climate models have shown superior performance in simulating important aspects of the precipitation climate including extremes and also to give partly different climate change ...signals compared to coarser-scale models. Here, we present the first long-term (1998–2018) simulation with a regional convection-permitting climate model for Fenno-Scandinavia. We use the HARMONIE-Climate (HCLIM) model on two nested grids; one covering Europe at 12 km resolution (HCLIM12) using parameterized convection, and one covering Fenno-Scandinavia with 3 km resolution (HCLIM3) with explicit deep convection. HCLIM12 uses lateral boundaries from ERA-Interim reanalysis. Model results are evaluated against reanalysis and various observational data sets, some at high resolutions. HCLIM3 strongly improves the representation of precipitation compared to HCLIM12, most evident through reduced “drizzle” and increased occurrence of higher intensity events as well as improved timing and amplitude of the diurnal cycle. This is the case even though the model exhibits a cold bias in near-surface temperature, particularly for daily maximum temperatures in summer. Simulated winter precipitation is biased high, primarily over complex terrain. Considerable undercatchment in observations may partly explain the wet bias. Examining instead the relative occurrence of snowfall versus rain, which is sensitive to variance in topographic heights it is shown that HCLIM3 provides added value compared to HCLIM12 also for winter precipitation. These results, indicating clear benefits of convection-permitting models, are encouraging motivating further exploration of added value in this region, and provide a valuable basis for impact studies.
ABSTRACT
The diurnal temperature range (DTR) is an important indicator of climate change, and it has decreased worldwide since the 1950s, particularly over arid and semiarid regions. This study ...analyses the effect of meteorological and anthropogenic factors on DTR variation to investigate the possible causes of DTR decreases in semiarid climates. The study region is located in northeast China, and the study period is from 1957 to 2006. There are three main results. First, the rate of decrease in the DTR is −1.24 K per 50 years. This decrease is mainly attributed to the increasing daily minimum temperature rate (Tmin, 2.24 K per 50 years), which is greater than the change in the daily maximum temperature (Tmax, 1.00 K per 50 years). Second, sunshine duration (SD) appears to be the most significant meteorological factor that determines the DTR through downward shortwave radiation (Rsw,d) and surface soil moisture (SM). The effect of Rsw,d is larger for Tmax than for Tmin; therefore, the decrease in Rsw,d results in a smaller increase in Tmax than in Tmin. On the other hand, the increase in SM can strengthen daytime latent heat release, and the increase in Tmax is then slowed because of the cooling effect of evaporation. The precipitation values and the leaf area index show a negative correlation with the DTR, whereas the cloud amount and the relative humidity appear not to be main causes of the DTR decrease in this region. Finally, atmospheric aerosols can reduce the SD by 0.27 h year–1 by decreasing atmospheric transparency, as indicated by an analysis of the Total Ozone Mapping Spectrometer Aerosol Index from 1979 to 2005. The decrease in direct solar radiation is the main cause of decreases in Rsw,d. These findings will provide references for DTR variation studies in similar climates.
Cueing facilitates retention and transfer of multimedia learning. From the perspective of cognitive load theory (CLT), cueing has a positive effect on learning outcomes because of the reduction in ...total cognitive load and avoidance of cognitive overload. However, this has not been systematically evaluated. Moreover, what remains ambiguous is the direct relationship between the cue-related cognitive load and learning outcomes. A meta-analysis and two subsequent meta-regression analyses were conducted to explore these issues. Subjective total cognitive load (SCL) and scores on a retention test and transfer test were selected as dependent variables. Through a systematic literature search, 32 eligible articles encompassing 3,597 participants were included in the SCL-related meta-analysis. Among them, 25 articles containing 2,910 participants were included in the retention-related meta-analysis and the following retention-related meta-regression, while there were 29 articles containing 3,204 participants included in the transfer-related meta-analysis and the transfer-related meta-regression. The meta-analysis revealed a statistically significant cueing effect on subjective ratings of cognitive load (d = -0.11, 95% CI = -0.19, -0.02, p < 0.05), retention performance (d = 0.27, 95% CI = 0.08, 0.46, p < 0.01), and transfer performance (d = 0.34, 95% CI = 0.12, 0.56, p < 0.01). The subsequent meta-regression analyses showed that dSCL for cueing significantly predicted dretention for cueing (β = -0.70, 95% CI = -1.02, -0.38, p < 0.001), as well as dtransfer for cueing (β = -0.60, 95% CI = -0.92, -0.28, p < 0.001). Thus in line with CLT, adding cues in multimedia materials can indeed reduce SCL and promote learning outcomes, and the more SCL is reduced by cues, the better retention and transfer of multimedia learning.
Statistically, the accessions in Hap 1 showed significantly lower root Na+/K+ ratios than those in the larger group Hap2 (P = 1.78 × 10−10). Since root Na+/K+ ratio is negatively correlated with salt ...resistance in tomato, Hap1 and Hap2 were defined as the tolerant and sensitive alleles of SlSOS1, respectively (Figure 1b). To assess whether the variations in this cis‐element contribute to SlSOS1 expression, we analysed the binding capacity of the CRT/DRE variants with SlDREB2, a known salt‐inducible DREB transcription factor in tomato recognizing CRT/DRE motif and inducing the expression of target genes (Hichri et al., 2016). Furthermore, phenotype analysis showed that slsos1‐1 and slsos1‐2 mutants were clearly more sensitive to salt stress than wild type plants (Figure 1n and o), which indicates that, like the Arabidopsis SOS1 (Shi et al., 2003), SlSOS1 also plays a crucial role in salt tolerance in tomato. Overall, our findings indicate that natural variations in the promoter of SlSOS1 disrupting the SlDREB2‐binding cis‐element result in reduced expression of SlSOS1 and increased salt sensitivity in the cultivated tomato due to selection during domestication.
The high-latitude regions of the Northern Hemisphere are a nexus for the interaction between land surface physical properties and their exchange of carbon and energy with the atmosphere. At these ...latitudes, two carbon pools of planetary significance – those of the permanently frozen soils (permafrost), and of the great expanse of boreal forest – are vulnerable to destabilization in the face of currently observed climatic warming, the speed and intensity of which are expected to increase with time. Improved projections of future Arctic and boreal ecosystem transformation require improved land surface models that integrate processes specific to these cold biomes. To this end, this study lays out relevant new parameterizations in the ORCHIDEE-MICT land surface model. These describe the interactions between soil carbon, soil temperature and hydrology, and their resulting feedbacks on water and CO2 fluxes, in addition to a recently developed fire module. Outputs from ORCHIDEE-MICT, when forced by two climate input datasets, are extensively evaluated against (i) temperature gradients between the atmosphere and deep soils, (ii) the hydrological components comprising the water balance of the largest high-latitude basins, and (iii) CO2 flux and carbon stock observations. The model performance is good with respect to empirical data, despite a simulated excessive plant water stress and a positive land surface temperature bias. In addition, acute model sensitivity to the choice of input forcing data suggests that the calibration of model parameters is strongly forcing-dependent. Overall, we suggest that this new model design is at the forefront of current efforts to reliably estimate future perturbations to the high-latitude terrestrial environment.
Nicotinamide adenine dinucleotide (NAD) is an essential coenzyme that has emerged as a central hub linking redox equilibrium and signal transduction in living organisms. The homeostasis of NAD is ...required for plant growth, development, and adaption to environmental cues. In this study, we isolated a chilling hypersensitive Arabidopsis thaliana mutant named qs-2 and identified the causal mutation in the gene encoding quinolinate synthase (QS) critical for NAD biosynthesis. The qs-2 mutant is also hypersensitive to salt stress and abscisic acid (ABA) but resistant to drought stress. The qs-2 mutant accumulates a reduced level of NAD and over-accumulates reactive oxygen species (ROS). The ABA-hypersensitivity of qs-2 can be rescued by supplementation of NAD precursors and by mutations in the ABA signaling components SnRK2s or RBOHF. Furthermore, ABA-induced over-accumulation of ROS in the qs-2 mutant is dependent on the SnRK2s and RBOHF. The expression of QS gene is repressed directly by ABI4, a transcription factor in the ABA response pathway. Together, our findings reveal an unexpected interplay between NAD biosynthesis and ABA and stress signaling, which is critical for our understanding of the regulation of plant growth and stress responses.
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