Forces driving transposable element load variation during Arabidopsis range expansion.

Genetic load refers to the accumulated and potentially life-threatening deleterious mutations in populations. Understanding the mechanisms underlying genetic load variation of transposable element (TE) insertion, a major large-effect mutation, during range expansion is an intriguing question in biology. Here, we used 1,115 global natural accessions of Arabidopsis (Arabidopsis thaliana) to study the driving forces of TE load variation during its range expansion. TE load increased with range expansion, especially in the recently established Yangtze River basin population. Effective population size, which explains 62.0% of the variance in TE load, high transposition rate, and selective sweeps contributed to TE accumulation in the expanded populations. We genetically mapped and identified multiple candidate causal genes and TEs, and revealed the genetic architecture of TE load variation. Overall, this study reveals the variation in TE genetic load during Arabidopsis expansion and highlights the causes of TE load variation from the perspectives of both population genetics and quantitative genetics.

Structural Engineering of BiVO4 /CoFe MOF Heterostructures Boosting Charge Transfer for Efficient Photoelectrochemical Water Splitting.

Boosting charge separation and transfer of photoanodes is crucial for providing high viability of photoelectrochemical hydrogen (H2 ) generation. Here, a structural engineering strategy is designed and synthesized for uniformly coating an ultrathin CoFe bimetal-organic framework (CoFe MOF) layer over a BiVO4 photoanode for boosted charge separation and transfer. The photocurrent density of the optimized BiVO4 /CoFe MOF(NA) photoanode reaches a value of 3.92 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE), up to 6.03 times that of pristine BiVO4 , due to the greatly increased efficiency of charge transfer and separation. In addition, this photoanode records one onset potential that is considerably shifted negatively when compared to BiVO4 . Transient absorption spectroscopy reveals that the CoFe MOF(NA) prolongs charge recombination lifetime by blocking the hole-transfer pathway from the BiVO4 to its surface trap states. This work sheds light on boosting charge separation and transfer through structural engineering to enhance the photocurrent of photoanodes for solar H2 production.

Weak transgenerational effects of ancestral nitrogen and phosphorus availabilities on offspring phenotypes in Arabidopsis thaliana.

Nutrient availability significantly regulates plant growth and metabolic functions, but whether and how the long-term exposure of ancestral plants to contrasting nutrient environments influences offspring phenotypic performance (i.e., transgenerational plasticity) remain poorly addressed. Here we conducted experimental manipulations using Arabidopsis thaliana with the ancestral plants grown in different nitrogen (N) and phosphorus (P) availabilities over eleven consecutive generations, and then examined the offspring phenotypic performance under the interactive effects of current and ancestral nutrient environments. We found that current rather than ancestral nutrient environments dominantly explained the variations in offspring plant traits (i.e., flowering time, aboveground biomass and biomass allocation fractions), suggesting the relatively weak transgenerational effects of ancestral N and P availabilities on offspring phenotypes. In contrast, increasing N and P availabilities in the offspring generation remarkably shortened the flowering time, increased the aboveground biomass, and altered biomass allocation fractions differentially among organs. Despite the overall weak transgenerational phenotypic plasticity, under the low nutrient environment, the offspring of ancestral plants from the low nutrient environment had a significantly higher fruit mass fraction than those from the suitable nutrient environment. Taken together, our findings suggest that A. thaliana exhibits a much stronger within- than trans-generational trait plasticity under contrasting nutrient availabilities, and may provide important insights into the understanding of plant adaptation and evolutionary processes under changing nutrient environments.

Transposable elements drive rapid phenotypic variation in Capsella rubella.

Rapid phenotypic changes in traits of adaptive significance are crucial for organisms to thrive in changing environments. How such phenotypic variation is achieved rapidly, despite limited genetic variation in species that experience a genetic bottleneck is unknown. Capsella rubella, an annual and inbreeding forb (Brassicaceae), is a great system for studying this basic question. Its distribution is wider than those of its congeneric species, despite an extreme genetic bottleneck event that severely diminished its genetic variation. Here, we demonstrate that transposable elements (TEs) are an important source of genetic variation that could account for its high phenotypic diversity. TEs are (i) highly enriched in C. rubella compared with its outcrossing sister species Capsella grandiflora, and (ii) 4.2% of polymorphic TEs in C. rubella are associated with variation in the expression levels of their adjacent genes. Furthermore, we show that frequent TE insertions at FLOWERING LOCUS C (FLC) in natural populations of C. rubella could explain 12.5% of the natural variation in flowering time, a key life history trait correlated with fitness and adaptation. In particular, we show that a recent TE insertion at the 3' UTR of FLC affects mRNA stability, which results in reducing its steady-state expression levels, to promote the onset of flowering. Our results highlight that TE insertions can drive rapid phenotypic variation, which could potentially help with adaptation to changing environments in a species with limited standing genetic variation.

Parallel Evolution of Common Allelic Variants Confers Flowering Diversity in Capsella rubella.

Flowering time is an adaptive life history trait. Capsella rubella, a close relative of Arabidopsis thaliana and a young species, displays extensive variation for flowering time but low standing genetic variation due to an extreme bottleneck event, providing an excellent opportunity to understand how phenotypic diversity can occur with a limited initial gene pool. Here, we demonstrate that common allelic variation and parallel evolution at the FLC locus confer variation in flowering time in C. rubella. We show that two overlapping deletions in the 5' untranslated region (UTR) of C. rubella FLC, which are associated with local changes in chromatin conformation and histone modifications, reduce its expression levels and promote flowering. We further show that these two pervasive variants originated independently in natural C. rubella populations after speciation and spread to an intermediate frequency, suggesting a role of this parallel cis-regulatory change in adaptive evolution. Our results provide an example of how parallel mutations in the same 5' UTR region can shape phenotypic evolution in plants.

Microsized Red Luminescent MgAl2O4:Mn4+ Single-Crystal Phosphor Grown in Molten Salt for White LEDs.

A single-crystalline defect-less phosphor is desired for efficient luminescence of the therein doped optical activators. In this paper, microsized MgAl2O4:Mn4+ single-crystal phosphors with bright red luminescence were grown in molten LiCl salt at 950 °C, for application in blue LED pumped white lighting. By comparing the phosphor formation from various Mg2+- and Al3+-bearing sources, both the template-formation and the dissolution-diffusion processes were evidenced to account for the formation of the microsized MgAl2O4:Mn4+ crystallites. Using nano γ-Al2O3 as the Al3+-bearing precursor, the uniform MgAl2O4:Mn4+ microcrystallites with a {111} planes-exposed tetragonal bipyramid morphology were obtained. The photoluminescence property was studied at various temperatures, and Mg ↔ Al anti-site disorder induced luminescence broadening was discussed. The Mn4+ 2Eg → 4A2g transition in MgAl2O4 shows a quite short luminescence wavelength peaking at 651 nm and ultrabroadband emission extending to 850 nm. The luminescence is relatively robust against thermal effect with relatively high thermal quenching temperature of 400 K and activation energy of 0.23 eV. Employing the red-emitting MgAl2O4:Mn4+ crystallites, blue LED pumped white lighting prototypes were fabricated which simulate the solar-like spectrum and show neutral to warm white.

Effects of nitrogen and phosphorus supply on stoichiometry of six elements in leaves of Arabidopsis thaliana.

BACKGROUND AND AIMS: Plant elemental composition is of fundamental importance for plant growth and metabolic functions. However, knowledge of how multi-elemental stoichiometry responds to varying nitrogen (N) and phosphorus (P) availabilities remains limited. METHODS: We conducted experimental manipulations with nine repeat experiments to investigate the effects of N and P supply on the concentrations and variability of six elements, carbon (C), N, P, potassium (K), calcium (Ca) and magnesium (Mg), in leaves of Arabidopsis thaliana. KEY RESULTS: N supply increased the concentrations of N, K and Mg, decreased the concentration of P, but exerted little influence on the concentrations of C and Ca in green leaves. P supply increased the concentrations of P and Ca, decreased the concentration of C, initially increased and then decreased the concentration of K, but showed little influence on the concentrations of N and Mg in green leaves. Multivariate patterns among the concentrations of these six elements in green leaves was influenced by the type of nutrient supply (i.e. N or P). Elemental variability decreased with increasing elemental concentrations in green leaves at the intraspecific level, supporting the Stability of Limiting Elements Hypothesis that was originally proposed from a meta-analysis of pooled data across species or communities. Compared with green leaves, the senesced leaves showed greater variability in C, N, P, K and Mg concentrations but lower variability in Ca concentration. CONCLUSIONS: N and P supplies exerted differential influences on the concentrations of C, N, P, K, Ca and Mg in green leaves. The specific C content should be considered when assessing C cycling under global nutrient changes. Stage-dependent patterns of leaf stoichiometric homeostasis differed among elements with various chemical characteristics. These findings can help to improve our understanding of plant eco-physiological responses and acclimation under global nutrient changes from the stoichiometric perspective of multiple elements.

The influencing mechanism of phosphorus component on network structure and bioactivity of bioactive glass.

(64-x)SiO2-36CaO-xP2O5 (x = 0, 2, 4, 6, 8 mol%) bioactive glasses are successfully prepared by sol-gel method, and the effect of phosphorus (P) content on the network structure, phase composition and in vitro mineralization performance of bioactive glasses is investigated by the various characterization techniques. Results show that the as-prepared bioactive glass has the amorphous structure. With the increase of P content, it can be found in FT-IR spectra that the characteristic peaks of bending vibration corresponding to the P-O bond in PO43- gradually appear. Among, the typical 60S4P has the highest percentage (73.81%) of bridging oxygen (BO), indicating its highest aggregation degree of silicate network. Besides, the introduction of P2O5 results in the formation of monophosphate, which enable the bioactive glasses to dissolve rapidly in water or simulate body fluids (SBF) and crystallize to form hydroxyapatite (HA), thereby enhancing its biological activity. After soaking in SBF for 3 days, the irregular cauliflower-like HA particles appear on the surface of bioactive glass, and the appropriate amount of P addition in glass could result in its high bioactivity. Therefore, this study could provide a theoretical reference for the relationship between the network structure and bioactivity of bioactive glass.

A highly sensitive TiO2-based molecularly imprinted photoelectrochemical sensor with regulation of imprinted sites by Photo-deposition.

Molecularly imprinted photoelectrochemical sensors (MIPES) have gained significant attention in the detection field due to their high selectivity and accuracy. However, their sensitivity still needs improvement. Here we developed a TiO2-based MIPES (TiO2 NRs/NiOOH/rMIP) to detect ciprofloxacin (CIP). We identified the photoactive sites of TiO2 by NiOOH photo-deposition and anchored the imprinted sites on the photoactive sites by complexation between CIP and NiOOH. By regulating the imprinted sites, the photocurrent difference before and after the addition of CIP increases and the detection sensitivity of CIP is improved. Moreover, a PN heterojunction is formed between TiO2 and NiOOH, which enables rapid transfer of photoexcited holes and electrons to different semiconductors under the built-in electric field. This leads to improved photoactivity of TiO2 and further increases the sensitivity of MIPES. Compared with sensors prepared by the traditional electro-polymerization CIP and Molecularly imprinted polymers (TiO2 NRs/NiOOH/eMIP), TiO2 NRs/NiOOH/rMIP as constructed in this work displays higher sensitivity, wider linear detection range, and lower limit of detection (LOD). Additionally, TiO2 NRs/NiOOH/rMIP shows good selectivity, stability, and recovery rate, and has a promising application prospect in the actual detection of antibiotics.

Highly stable lithium sulfur batteries enhanced by flocculation and solidification of soluble polysulfides in routine ether electrolyte.

Lithium-sulfur batteries (LSBs) are among the most promising next-generation high energy density energy-storage systems. However, practical application has been hindered by fundamental problems, especially shuttling by the higher-order polysulfides (PSs) and slow redox kinetics. Herein, a novel electrolyte-based strategy is proposed by adding an ultrasmall amount of the low-cost and commercially available cationic antistatic agent octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate (SN) into a routine ether electrolyte. Due to the strong cation-anion interaction and bridge-bonding with SN, rapid flocculation of the soluble polysulfide intermediates into solid-state polysulfide-SN sediments is found, which significantly inhibited the adverse shuttling effect. Moreover, a catalytic effect was also demonstrated for conversion of the polysulfide-SN intermediates, which enhanced the redox kinetics of Li-S batteries. Encouragingly, for cells with only 0.1 % added SN, an initial specific capacity of 783.6 mAh/g and a retained specific capacity of 565.7 mAh/g were found at 2C after 200 cycles, which corresponded to an ultralow capacity decay rate of only 0.014 % per cycle. This work may provide a simple and promising regulation strategy for preparing highly stable Li-S batteries.

Flame Characteristics of Gasoline and a Water-in-Gasoline Mixture under a Controllable High-Temperature Thermal Atmosphere.

This study explores the flame characteristics of gasoline and a water-in-gasoline mixture and provides some optimization suggestions for the control strategy of water-in-gasoline mixture injection in the internal combustion Rankine cycle engines. The influences of co-flow temperature, injection pressure condition, and water content on the flame characteristics were investigated under a controllable high-temperature thermal atmosphere, including flame pattern, liftoff height, brightness, and local peak temperature distribution. Results obtained show that the water content has the most significant effect on the flame characteristics. The flame pattern gradually changes from slender to lumpy as the water content rises, while the high-temperature zone increases and becomes uniform. There is an appropriate water content range of 10-20% in which the flame characteristics are generally better. Furthermore, as the water content increases from 20 to 30%, the flame characteristics deteriorate, with a sharp decrease in the maximum flame temperature and brightness.

Preparation of the bioglass/chitosan-alginate composite scaffolds with high bioactivity and mechanical properties as bone graft materials.

Bioglass/chitosan-alginate (BCA) composite scaffolds with remarkable performance for bone tissue engineering are successfully prepared by freeze-drying method. The influence of the addition amount of sodium alginate (SA) on the microstructure, porosity, pore size, swelling ratio, degradation ratio, mechanical properties and mineralization ability of BCA composite scaffolds is studied and characterized by various techniques of the scanning electron microscopy, X-ray diffraction, infrared absorption spectrometer and so on. The results show that the BCA composite scaffolds have the three-dimensional interconnected network structure with the high porosity of 82%-87% and a suitable average pore size of 140-200 µm. With the increase of SA addition, the porosity and pore size of BCA gradually reduced and the thickness of pore wall increased. The swelling and degradation ratios decreased gradually with the raising SA and increased with the prolongation of soaking time in PBS. The mechanical strength of BCA was also significantly enhanced, and the mineralization ability of bioglass was effectively deployed with the adding SA of BCA. The improved performance of BCA may be attributed to the formed 3D network structure, activated bioavailability and crosslinking ability between chitosan and SA. It indicates that BCA composite scaffolds have potential applications in bone issues engineering.

Enhanced triethylamine-sensing properties of hierarchical molybdenum trioxide nanostructures derived by oxidizing molybdenum disulfide nanosheets.

A 3D α-MoO3 nanostructure for high-performance triethylamine (TEA) detection was synthesized via the facial oxidation of MoS2 nanoflowers (NFs) obtained by a hydrothermal process. The influence of the time of hydrothermal process in growing MoS2 on the morphologies of the final MoO3 obtained after calcination was investigated. As-obtained MoO3 and their precursors were systematically characterized by various techniques, such as X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption-desorption isotherms. Results showed that MoO3 with a hierarchical layered nanostructure was successfully obtained. After hydrothermal treatment of the MoS2 precursor for 20 h, the typical MoO3-based sensor (called M20) exhibited a high response of 2.42 at a very low TEA concentration of only 0.1 ppm at 240 °C. The M20 sensor response to 50 ppm TEA was as high as 125 with a fast response/recovery time of 14/22 s. Moreover, the sensor had a high stability and reproducibility as well as a high selectivity against other interfering VOCs or gases. Due to the tendency of TEA to adsorb to active oxygen sites of MoO3, the enhanced sensing properties of MoO3 can be ascribed to the remarkable hierarchical structure and large surface area. MoO3 obtained after calcination of hydrothermally grown MoS2 is thus a promising sensing material for enhanced TEA gas detection.

Microwave-assisted synthesis of hierarchically porous Co3O4/rGO nanocomposite for low-temperature acetone detection.

Acetone sensors with high response and excellent selectivity are of enormous demand for monitoring the diabetes. This paper has reported a novel porous 3D hierarchical Co3O4/rGO nanocomposite synthesized by a microwave-assisted method, by which Co3O4 nanoparticles are rapidly and uniformly anchored on rGO nanosheets. The phase composition, surface morphology of the Co3O4/rGO composites and the effect of rGO on their acetone-sensing performance were systematically investigated. The results show that the sample with an optimized content of rGO (Co3O4/rGO-1) achieves the highest stability and response to acetone (0.5 ~ 200 ppm) at a relatively low temperature (~160 °C). Also, the Co3O4/rGO-1 exhibits a high acetone-sensing selectivity against the gases (or vapors) of H2S, H2, CH4, HCHO, CH3OH, C3H8O and C2H5OH. The enhanced acetone-sensing performance of the Co3O4/rGO composite can be attributed to the Co3O4/rGO p-p heterojunction and the Co3+-C coupling effect between Co3O4 and rGO, improving transport of carriers. In addition, the unique 3D hierarchically porous structure and large surface areas are favorable to adsorption and desorption of gas molecules. This facile microwave-assisted method provides a charming strategy to develop smart rGO-based nanomaterials for real-time detection of harmful gases and rapid medical diagnosis.

High temperature induced S vacancies in natural molybdenite for robust electrocatalytic nitrogen reduction.

Defect engineering is an important strategy to regulate electronic structure of electrocatalysts for electrochemical N2 fixation, aiming at improving the electron state density and enhancing the adsorption and activation of inert N2. In this paper, a high-temperature strategy to anneal the natural molybdenite under Ar atmosphere was developed, and the as-obtained molybdenite with S vacancies boosted a high activity for N2 reduction reaction. In 0.1 M HCl, the catalyst annealed at 800 °C exhibits a high Faradic efficiency of 17.9% and a NH3 yield of 23.38 µg h-1 mg-1cat. at -0.35 V versus reversible hydrogen electrode, two times higher than that of the pristine molybdenite. The facile one-step annealing method introduces the defects (e.g., S vacancies) in the surface of the natural molybdenite particles to prepare catalysts for generating ammonia by reducing nitrogen at room temperature under ordinary pressure, promoting the development of low-carbon economic prospect.

Ultrabroadband red luminescence of Mn4+ in MgAl2O4 peaking at 651 nm.

Blue light pumped red luminescence with broadband and high photon-energy emission is highly desired for phosphor-converted white light-emitting diodes (pc-wLEDs), to achieve a high color rendering index and high luminous efficacy. Mn4+-doped red-emitting phosphors generally exhibit sharp vibronic emissions associated with the parity- and spin-forbidden 2Eg→4A2g transitions. In this paper, two abnormal luminescence behaviors were observed for Mn4+ in the MgAl2O4:Mn4+ spinel phosphor with a short wavelength emission band peaking at 651 nm. Firstly, the Mn4+ 2Eg→4A2g transition exhibits ultrabroadband luminescence in MgAl2O4 and the large full-width at half-maximum (FWHM) is dependent both on the calcination temperature and on the partial substitution of Al3+ with Ga3+. Secondly, the thermal quenching behavior of the Mn4+ 2Eg→4A2g luminescence in MgAl2O4 shows a dependence on its thermal treatment and preparation method. The Rietveld refinement and Raman results demonstrate that the variation in the FWHM of the luminescence spectra is a sum effect of structural ordering (i.e., isotropic displacement decrease of constituent atoms) and the Mg ↔ Al anti-site disorder. A model for the observed varying thermal quenching of luminescence was tentatively proposed. The intrinsic thermal quenching temperature of Mn4+ luminescence in MgAl2O4 was found to be 390-400 K using the samples prepared by the co-precipitation and molten salt methods. The present work gives a novel perspective to understand the luminescence spectra of Mn4+ 2Eg→4A2g transition.

Biomass Allocation in Response to Nitrogen and Phosphorus Availability: Insight From Experimental Manipulations of Arabidopsis thaliana.

Allocation of biomass to different organs is a fundamental aspect of plant responses and adaptations to changing environmental conditions, but how it responds to nitrogen (N) and phosphorus (P) availability remains poorly addressed. Here we conducted greenhouse fertilization experiments using Arabidopsis thaliana, with five levels of N and P additions and eight repeat experiments, to ascertain the effects of N and P availability on biomass allocation patterns. N addition increased leaf and stem allocation, but decreased root and fruit allocation. P addition increased stem and fruit allocation, but decreased root and leaf allocation. Pooled data of the five levels of N addition relative to P addition resulted in lower scaling exponents of stem mass against leaf mass (0.983 vs. 1.226; p = 0.000), fruit mass against vegetative mass (0.875 vs. 1.028; p = 0.000), and shoot mass against root mass (1.069 vs. 1.324; p = 0.001). This suggested that N addition relative to P addition induced slower increase in stem mass with increasing leaf mass, slower increase in reproductive mass with increasing vegetative mass, and slower increase in shoot mass with increasing root mass. Further, the levels of N or P addition did not significantly affect the allometric relationships of stem mass vs. leaf mass, and fruit mass vs. vegetative mass. In contrast, increasing levels of N addition increased the scaling exponent of shoot to root mass, whereas increasing levels of P addition exerted the opposite influence on the scaling exponent. This result suggests that increasing levels of N addition promote allocation to shoot mass, whereas the increasing levels of P addition promote allocation to root mass. Our findings highlight that biomass allocation of A. thaliana exhibits a contrasting response to N and P availability, which has profound implications for forecasting the biomass allocation strategies in plants to human-induced nutrient enrichment.

Transposable Elements Contribute to the Adaptation of Arabidopsis thaliana.

Transposable elements (TEs) are mobile genetic elements with very high mutation rates that play important roles in shaping genome architecture and regulating phenotypic variation. However, the extent to which TEs influence the adaptation of organisms in their natural habitats is largely unknown. Here, we scanned 201 representative resequenced genomes from the model plant Arabidopsis thaliana and identified 2,311 polymorphic TEs from noncentromeric regions. We found expansion and contraction of different types of TEs in different A. thaliana populations. More importantly, we identified two TE insertions that are likely candidates to play a role in adaptive evolution. Our results highlight the importance of variations in TEs for the adaptation of plants in general in the context of rapid global climate change.

Adaptation of Arabidopsis thaliana to the Yangtze River basin.

BACKGROUND: Organisms need to adapt to keep pace with a changing environment. Examining recent range expansion aids our understanding of how organisms evolve to overcome environmental constraints. However, how organisms adapt to climate changes is a crucial biological question that is still largely unanswered. The plant Arabidopsis thaliana is an excellent system to study this fundamental question. Its origin is in the Iberian Peninsula and North Africa, but it has spread to the Far East, including the most south-eastern edge of its native habitats, the Yangtze River basin, where the climate is very different. RESULTS: We sequenced 118 A. thaliana strains from the region surrounding the Yangtze River basin. We found that the Yangtze River basin population is a unique population and diverged about 61,409 years ago, with gene flows occurring at two different time points, followed by a population dispersion into the Yangtze River basin in the last few thousands of years. Positive selection analyses revealed that biological regulation processes, such as flowering time, immune and defense response processes could be correlated with the adaptation event. In particular, we found that the flowering time gene SVP has contributed to A. thaliana adaptation to the Yangtze River basin based on genetic mapping. CONCLUSIONS: A. thaliana adapted to the Yangtze River basin habitat by promoting the onset of flowering, a finding that sheds light on how a species can adapt to locales with very different climates.