Toxicokinetics of MDMA and Its Metabolite MDA in Rats.

OBJECTIVES: To investigate the toxicokinetic differences of 3,4-methylenedioxy-N-methylamphetamine (MDMA) and its metabolite 4,5-methylene dioxy amphetamine (MDA) in rats after single and continuous administration of MDMA, providing reference data for the forensic identification of MDMA. METHODS: A total of 24 rats in the single administration group were randomly divided into 5, 10 and 20 mg/kg experimental groups and the control group, with 6 rats in each group. The experimental group was given intraperitoneal injection of MDMA, and the control group was given intraperitoneal injection of the same volume of normal saline as the experimental group. The amount of 0.5 mL blood was collected from the medial canthus 5 min, 30 min, 1 h, 1.5 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h after administration. In the continuous administration group, 24 rats were randomly divided into the experimental group (18 rats) and the control group (6 rats). The experimental group was given MDMA 7 d by continuous intraperitoneal injection in increments of 5, 7, 9, 11, 13, 15, 17 mg/kg per day, respectively, while the control group was given the same volume of normal saline as the experimental group by intraperitoneal injection. On the eighth day, the experimental rats were randomly divided into 5, 10 and 20 mg/kg dose groups, with 6 rats in each group. MDMA was injected intraperitoneally, and the control group was injected intraperitoneally with the same volume of normal saline as the experimental group. On the eighth day, 0.5 mL of blood was taken from the medial canthus 5 min, 30 min, 1 h, 1.5 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h after administration. Liquid chromatography-triple quadrupole tandem mass spectrometry was used to detect MDMA and MDA levels, and statistical software was employed for data analysis. RESULTS: In the single-administration group, peak concentrations of MDMA and MDA were reached at 5 min and 1 h after administration, respectively, with the largest detection time limit of 12 h. In the continuous administration group, peak concentrations were reached at 30 min and 1.5 h after administration, respectively, with the largest detection time limit of 10 h. Nonlinear fitting equations for the concentration ratio of MDMA and MDA in plasma and administration time in the single-administration group and continuous administration group were as follows: T=10.362C-1.183, R2=0.974 6; T=7.397 3C-0.694, R2=0.961 5 (T: injection time; C: concentration ratio of MDMA to MDA in plasma). CONCLUSIONS: The toxicokinetic data of MDMA and its metabolite MDA in rats, obtained through single and continuous administration, including peak concentration, peak time, detection time limit, and the relationship between concentration ratio and administration time, provide a theoretical and data foundation for relevant forensic identification.

Cucurbituril-protected dual-readout gold nanoclusters for sensitive fentanyl detection.

A large number of cases showed that fentanyl (FEN) has become the main cause of death from illegal drug overdose owing to its potent effect on respiratory depression, which has emerged as a grave threat to public health and safety. However, traditional analytical methods require cost-prohibitive equipment, complex pretreatment procedures, and technically trained experts, thus highlighting the urgent need to develop a cost-effective, straightforward, and highly sensitive method to detect FEN. This work demonstrated a dual-readout sensor FGGC-AuNCs@Q7 for FEN detection, which is based on the molecular recognition and self-assembly between the macrocycle cucurbit[7]uril (Q7) and FEN, accompanying spontaneous visual Tyndall effect and fluorescence optical responses of the gold nanoclusters within seconds. A detection limit of 1 ng mL-1 and a linear range of 9 to 148 000 ng mL-1 were achieved for fluorescence detection on FEN, with favorable selectivity in the presence of other illicit drugs or common interferents. The proposed method has been proved by its satisfactory application for the analysis of human urine.

Machine Learning-Assisted Rapid Screening of Four Types of New Psychoactive Substances in Drug Seizures.

Over the past few years, new psychoactive substances (NPS) have become a global health and social problem because of their wide variety, constant structural renewal, vague legal definitions, and rapid adaptation to legal restrictions. The rapid structural modifications of NPS have posed significant challenges for the screening and identification of these new substances using traditional mass spectrometric techniques based on reference substances or a mass spectral database. Here, we propose supervised machine learning (ML) classification models such as k-nearest neighbors, support vector machine, random forest, and multigrained cascade forest for the rapid screening of NPS using mass spectrometric data. This approach utilizes ML methods to learn the statistical probability distributions of mass spectral data for NPS and non-NPS. Four classification ML models were generated and evaluated using a data set comprising 567 LC-MS and 732 GC-MS spectra. Through cross validation, we achieved an F1 score of 0.35-0.97. These algorithms were applied in conjunction with mass spectrometry techniques for the detection of six seizures including electronic cigarette oil and suspected powdered substances netted in drug trafficking cases. The models provided warning signals for synthetic cannabinoids, synthetic cathinones, and fentanyl. Thus, an early warning system was successfully established, which provided a useful method for reliable and effective identifications of unknown NPS.

Teaching PCR for Simultaneous Sensing of Gene Transcription and Downstream Metabolites by Cucurbit[8]uril-Mediated Intervention of Polymerase Activity.

The target of typical PCR analysis is restricted to nucleic acids. To this end, we report here a novel strategy to simultaneously detect genetic and metabolic markers using commercial PCR kits with cucurbit[8]urils (CB[8]) implemented to manipulate the activity of Taq DNA polymerase. CB[8] binds with the nonionic surfactants and displaces them from the polymerase surface, resulting in decreased enzyme activity. Meanwhile, the inhibited enzyme can be reversibly activated when spermine, the downstream metabolite of ornithine decarboxylase (ODC), is present in the sample, which competitively binds to CB[8] and recovers polymerase activity. CB[8] was implemented in conventional PCR kits not only to reduce false-positive results but also to extend the detection range of PCR technology. With this novel method to detect ODC in cell lysates containing both the nucleotides and intracellular metabolites, positive results were only observed in highly active HEK 293T cells, whereas silent cells treated with ODC inhibitor showed negative readouts, therefore providing a simple but elegant dual-modality PCR method for precision diagnosis.

Incomplete genome doubling enables to consistently enhance plant growth for maximum biomass production by altering multiple transcript co-expression networks in potato.

KEY MESSAGE: Cytochimera potato plants, which mixed with diploid and tetraploid cells, could cause the highest and significantly increased biomass yield than the polyploid and diploid potato plants. Polyploidization is an important approach in crop breeding for agronomic trait improvement, especially for biomass production. Cytochimera contains two or more mixed cells with different levels of ploidy, which is considered a failure in whole genome duplication. Using colchicine treatment with diploid (Dip) potato (Solanum chacoense) plantlets, this study generated tetraploid (Tet) and cytochimera (Cyt) lines, which, respectively, contained complete and partial cells with genome duplication. Compared to the Dip potato, we observed remarkably enhanced plant growth and biomass yields in Tet and Cyt lines. Notably, the Cyt potato straw, which was generated from incomplete genome doubling, was of significantly higher biomass yield than that of the Tet with a distinctively altered cell wall composition. Meanwhile, we observed that one layer of the tetraploid cells (about 30%) in Cyt plants was sufficient to trigger a gene expression pattern similar to that of Tet, suggesting that the biomass dominance of Cyt may be related to the proportion of different ploidy cells. Further genome-wide analyses of co-expression networks indicated that down-regulation (against Dip) of spliceosomal-related transcripts might lead to differential alternative splicing for specifically improved agronomic traits such as plant growth, biomass yield, and lignocellulose composition in Tet and Cyt plants. In addition, this work examined that the genome of Cyt line was relatively stable after years of asexual reproduction. Hence, this study has demonstrated that incomplete genome doubling is a promising strategy to maximize biomass production in potatoes and beyond.

2-Fluorodeschloroketamine has similar abuse potential as ketamine.

2-Fluorodeschloroketamine (2-FDCK) as a substitute for ketamine has emerged among drug abusers in recent years. However, 2-FDCK has not been controlled or regulated in many countries, which may be partly related to the lack of evidence on its abuse potential. In this study, we evaluated the abuse potential of 2-FDCK via the tests of the conditioned place preference (CPP), locomotor sensitization, drug self-administration and drug discrimination using ketamine as a reference. 2-FDCK induced significant CPP at a minimum dose of 3 mg/kg in mice, an effect comparable with that of ketamine (3 mg/kg). Acute injections of 2-FDCK or ketamine at 30 mg/kg enhanced locomotor activity. Repeated treatments with this dose of 2-FDCK and ketamine induced locomotor sensitization after withdrawal. 2-FDCK readily induced self-administration with 0.5 mg/kg/infusion, the same dose for ketamine, and induced the highest seeking response at 1 mg/kg. Drug discrimination test showed that 2-FDCK dose-dependently substitute for ketamine with comparable ED50 to ketamine in substitution testing. Taken together, these results strongly suggested that 2-FDCK has an abuse potential comparable with ketamine.

Quantifying the relationship between dapagliflozin and loss of weight in type 1 diabetes mellitus patients.

WHAT IS KNOWN AND OBJECTIVES: Dapagliflozin was the first oral treatment approved in type 1 diabetes mellitus (T1DM) patients, simultaneously improving body weight. However, the time course and dose effect of dapagliflozin on loss of weight in T1DM patients was still unknown. The present study aimed to investigate quantitative relationship between dapagliflozin and loss of weight in T1DM patients based on Model-based Meta-analysis. METHODS: Five dapagliflozin dosage groups, two of them were 5 mg/day and three of them were 10 mg/day, 1612 T1DM patients were analysed with maximal effect (Emax ) model, and evaluation index was change rate of body weight from baseline value. RESULTS: In these T1DM patients, dosages were not incorporated into model, indicating no significant dose-response relationship between 5 and 10 mg/day affecting loss of weight. Emax and the treatment duration to reach half of the maximal effects (ET50 ) of dapagliflozin influencing loss of weight in T1DM patients were -4.9% and 10.4 weeks, and the duration to achieve 25%, 50%, 75%, and 80% (plateau) of Emax were 3.5, 10.4, 31.2, and 41.6 weeks. WHAT IS NEW AND CONCLUSIONS: It was the first time to explore quantitative relationship between dapagliflozin and loss of weight in T1DM patients. To achieve the plateau period in loss of weight, 5 mg/day dapagliflozin was required for at least 41.6 weeks.

Diverse Banana Pseudostems and Rachis Are Distinctive for Edible Carbohydrates and Lignocellulose Saccharification towards High Bioethanol Production under Chemical and Liquid Hot Water Pretreatments.

Banana is a major fruit crop throughout the world with abundant lignocellulose in the pseudostem and rachis residues for biofuel production. In this study, we collected a total of 11 pseudostems and rachis samples that were originally derived from different genetic types and ecological locations of banana crops and then examined largely varied edible carbohydrates (soluble sugars, starch) and lignocellulose compositions. By performing chemical (H2SO4, NaOH) and liquid hot water (LHW) pretreatments, we also found a remarkable variation in biomass enzymatic saccharification and bioethanol production among all banana samples examined. Consequently, this study identified a desirable banana (Refen1, subgroup Pisang Awak) crop containing large amounts of edible carbohydrates and completely digestible lignocellulose, which could be combined to achieve the highest bioethanol yields of 31-38% (% dry matter), compared with previously reported ones in other bioenergy crops. Chemical analysis further indicated that the cellulose CrI and lignin G-monomer should be two major recalcitrant factors affecting biomass enzymatic saccharification in banana pseudostems and rachis. Therefore, this study not only examined rich edible carbohydrates for food in the banana pseudostems but also detected digestible lignocellulose for bioethanol production in rachis tissue, providing a strategy applicable for genetic breeding and biomass processing in banana crops.

Factors influencing university teachers' use of a mobile technology-enhanced teaching (MTT) platform.

The main purpose of this study was to examine the critical factors influencing university teachers' use of a mobile technology-enhanced teaching (MTT) platform during the new coronavirus (COVID-19) epidemic. An integrated model with multiple factors drawing from the theoretical models and learning theories was proposed in this study to examine university teachers' intentions to use an MTT platform. The multiple factors included the individual factor (e.g., growth mindset, help seeking, and self-efficacy), the social factor (e.g., social norms), and the technological acceptance factor (e.g., perceived usefulness and perceived ease of use). The survey method was used to collect data on university teachers' perceptions of the MTT platform use, and a two-step structural equation modeling approach was used for the data analysis. Based on the path analysis of a total of 214 valid responses, the results identified that growth mindset, help seeking, and self-efficacy from the individual factor, as well as perceived usefulness from the technology acceptance factor were the significant determinants of university teachers' intentions to adopt the MTT. The contributions of this study are twofold. First, the proposed model was derived from multiple literature sources, providing a sound theoretical foundation to understand MTT platform use from an academic angle. Second, university teachers' viewpoints are a unique observation of their actual platform use, providing practical insights into the improvement and maintenance of MTT-related platforms for all educators. The findings are especially valuable during the post-COVID-19 era.

A novel rice fragile culm 24 mutant encodes a UDP-glucose epimerase that affects cell wall properties and photosynthesis.

UDP-glucose epimerases (UGEs) are essential enzymes for catalysing the conversion of UDP-glucose (UDP-Glc) into UDP-galactose (UDP-Gal). Although UDP-Gal has been well studied as the substrate for the biosynthesis of carbohydrates, glycolipids, and glycoproteins, much remains unknown about the biological function of UGEs in plants. In this study, we selected a novel rice fragile culm 24 (Osfc24) mutant and identified it as a nonsense mutation of the FC24/OsUGE2 gene. The Osfc24 mutant shows a brittleness phenotype with significantly altered cell wall composition and disrupted orientation of the cellulose microfibrils. We found significantly reduced accumulation of arabinogalactan proteins in the cell walls of the mutant, which may consequently affect plant growth and cell wall deposition, and be responsible for the altered cellulose microfibril orientation. The mutant exhibits dwarfism and paler leaves with significantly decreased contents of galactolipids and chlorophyll, resulting in defects in plant photosynthesis. Based on our results, we propose a model for how OsUGE2 participates in two distinct metabolic pathways to co-modulate cellulose biosynthesis and cell wall assembly by dynamically providing UDP-Gal and UDP-Glc substrates.

Synthesis of MoS2/TiO2 Nanophotocatalyst and Its Enhanced Visible Light Driven Photocatalytic Performance.

Molybdenum disulfide (MoS2), as a typical layered transition metal sulfide, has been widely used in photocatalysis. Here, we report layered MoS2 nanosheet-coated TiO2 heterostructures that were prepared using a simple photo-assisted deposition method. The as-prepared samples were investigated in detail by using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Results demonstrated that the MoS2 nanosheets uniformly covered the outer surface of TiO2. The visible light-sensitive photocatalytic activity was evaluated by the removal of methylene blue (MB) and 2-chlorophenol (2-CP) in aqueous solution. Thus, the MoS2/TiO2 heterostructures exhibited improved photocatalytic degradation activity under visible light compared with the pure TiO2. Under visible light irradiation for 90 min, the degradation efficiencies of MB and 2-CP over the MoS2/TiO2 sample (sunlight irradiation time: 30 min) are as high as 93.6% and 70.6%, respectively. Furthermore, the corresponding mechanism of enhanced photocatalytic activity is proposed on the basis of the comprehensively investigated results from the radical trapping experiments, photoluminescence spectroscopy, and electron spin resonance analysis. The hole oxidation, hydroxyl radicals, and superoxide anion radicals act as the active species simultaneously in the photodegradation of the dye molecules. However, of these species, hole oxidation played the most important roles in the photocatalytic reaction.

Sucrose Synthase Enhances Hull Size and Grain Weight by Regulating Cell Division and Starch Accumulation in Transgenic Rice.

Grain size and weight are two important determinants of grain yield in rice. Although overexpression of sucrose synthase (SUS) genes has led to several improvements on cellulose and starch-based traits in transgenic crops, little is reported about SUS enhancement of hull size and grain weight in rice. In this study, we selected transgenic rice plants that overexpressed OsSUS1-6 genes driven with the maize Ubi promoter. Compared to the controls (wild type and empty vector line), all independent OsSUS homozygous transgenic lines exhibited considerably increased grain yield and grain weights. Using the representative OsSUS3 overexpressed transgenic plants, four independent homozygous lines showed much raised cell numbers for larger hull sizes, consistent with their enhanced primary cell wall cellulose biosynthesis and postponed secondary wall synthesis. Accordingly, the OsSUS3 transgenic lines contained much larger endosperm volume and higher starch levels than those of the controls in the mature grains, leading to increased brown grain weights by 15-19%. Hence, the results have demonstrated that OsSUS overexpression could significantly improve hull size and grain weight by dynamically regulating cell division and starch accumulation in the transgenic rice.

Correction to: Identification of tRNA nucleoside modification genes critical for stress response and development in rice and Arabidopsis.

CORRECTION: Following publication of the original article [1], the authors reported that there was a mistake in the presentation of their funding information. The sentence "This study was supported by the National Natural Science Foundation of China (31,100,268 to Peng Chen, 31,270,658 to Bo Zheng);" should instead read "This study was supported by the National Natural Science Foundation of China (31100268 to Peng Chen, 31370604 to Bo Zheng);".

Three AtCesA6-like members enhance biomass production by distinctively promoting cell growth in Arabidopsis.

Cellulose is an abundant biopolymer and a prominent constituent of plant cell walls. Cellulose is also a central component to plant morphogenesis and contributes the bulk of a plant's biomass. While cellulose synthase (CesA) genes were identified over two decades ago, genetic manipulation of this family to enhance cellulose production has remained difficult. In this study, we show that increasing the expression levels of the three primary cell wall AtCesA6-like genes (AtCesA2, AtCesA5, AtCesA6), but not AtCesA3, AtCesA9 or secondary cell wall AtCesA7, can promote the expression of major primary wall CesA genes to accelerate primary wall CesA complex (cellulose synthase complexes, CSCs) particle movement for acquiring long microfibrils and consequently increasing cellulose production in Arabidopsis transgenic lines, as compared with wild-type. The overexpression transgenic lines displayed changes in expression of genes related to cell growth and proliferation, perhaps explaining the enhanced growth of the transgenic seedlings. Notably, overexpression of the three AtCesA6-like genes also enhanced secondary cell wall deposition that led to improved mechanical strength and higher biomass production in transgenic mature plants. Hence, we propose that overexpression of certain AtCesA genes can provide a biotechnological approach to increase cellulose synthesis and biomass accumulation in transgenic plants.

Ectopic expression of a novel OsExtensin-like gene consistently enhances plant lodging resistance by regulating cell elongation and cell wall thickening in rice.

Plant lodging resistance is an important integrative agronomic trait of grain yield and quality in crops. Although extensin proteins are tightly associated with plant cell growth and cell wall construction, little has yet been reported about their impacts on plant lodging resistance. In this study, we isolated a novel extensin-like (OsEXTL) gene in rice, and selected transgenic rice plants that expressed OsEXTL under driven with two distinct promoters. Despite different OsEXTL expression levels, two-promoter-driven OsEXTL-transgenic plants, compared to a rice cultivar and an empty vector, exhibited significantly reduced cell elongation in stem internodes, leading to relatively shorter plant heights by 7%-10%. Meanwhile, the OsEXTL-transgenic plants showed remarkably thickened secondary cell walls with higher cellulose levels in the mature plants, resulting in significantly increased detectable mechanical strength (extension and pushing forces) in the mature transgenic plants. Due to reduced plant height and increased plant mechanical strength, the OsEXTL-transgenic plants were detected with largely enhanced lodging resistances in 3 years field experiments, compared to those of the rice cultivar ZH11. In addition, despite relatively short plant heights, the OsEXTL-transgenic plants maintain normal grain yields and biomass production, owing to their increased cellulose levels and thickened cell walls. Hence, this study demonstrates a largely improved lodging resistance in the OsEXTL-transgenic rice plants, and provides insights into novel extensin functions in plant cell growth and development, cell wall network construction and wall structural remodelling.

Identification of tRNA nucleoside modification genes critical for stress response and development in rice and Arabidopsis.

BACKGROUND: Modification of nucleosides on transfer RNA (tRNA) is important either for correct mRNA decoding process or for tRNA structural stabilization. Nucleoside methylations catalyzed by MTase (methyltransferase) are the most common type among all tRNA nucleoside modifications. Although tRNA modified nucleosides and modification enzymes have been extensively studied in prokaryotic systems, similar research remains preliminary in higher plants, especially in crop species, such as rice (Oryza sativa). Rice is a monocot model plant as well as an important cereal crop, and stress tolerance and yield are of great importance for rice breeding. RESULTS: In this study, we investigated how the composition and abundance of tRNA modified nucleosides could change in response to drought, salt and cold stress, as well as in different tissues during the whole growth season in two model plants-O. sativa and Arabidopsis thaliana. Twenty two and 20 MTase candidate genes were identified in rice and Arabidopsis, respectively, by protein sequence homology and conserved domain analysis. Four methylated nucleosides, Am, Cm, m1A and m7G, were found to be very important in stress response both in rice and Arabidopsis. Additionally, three nucleosides,Gm, m5U and m5C, were involved in plant development. Hierarchical clustering analysis revealed consistency on Am, Cm, m1A and m7G MTase candidate genes, and the abundance of the corresponding nucleoside under stress conditions. The same is true for Gm, m5U and m5C modifications and corresponding methylation genes in different tissues during different developmental stages. CONCLUSIONS: We identified candidate genes for various tRNA modified nucleosides in rice and Arabidopsis, especially on MTases for methylated nucleosides. Based on bioinformatics analysis, nucleoside abundance assessments and gene expression profiling, we propose four methylated nucleosides (Am, Cm, m1A and m7G) that are critical for stress response in rice and Arabidopsis, and three methylated nucleosides (Gm, m5U and m5C) that might be important during development.

The 2'-O-methyladenosine nucleoside modification gene OsTRM13 positively regulates salt stress tolerance in rice.

Stress induces changes of modified nucleosides in tRNA, and these changes can influence codon-anticodon interaction and therefore the translation of target proteins. Certain nucleoside modification genes are associated with regulation of stress tolerance and immune response in plants. In this study, we found a dramatic increase of 2'-O-methyladenosine (Am) nucleoside in rice seedlings subjected to salt stress and abscisic acid (ABA) treatment. We identified LOC_Os03g61750 (OsTRM13) as a rice candidate methyltransferase for the Am modification. OsTRM13 transcript levels increased significantly upon salt stress and ABA treatment, and the OsTrm13 protein was found to be located primarily to the nucleus. More importantly, OsTRM13 overexpression plants displayed improved salt stress tolerance, and vice versa, OsTRM13 RNA interference (RNAi) plants showed reduced tolerance. Furthermore, OsTRM13 complemented a yeast trm13Δ mutant, deficient in Am synthesis, and the purified OsTrm13 protein catalysed Am nucleoside formation on tRNA-Gly-GCC in vitro. Our results show that OsTRM13, encoding a rice tRNA nucleoside methyltransferase, is an important regulator of salt stress tolerance in rice.

Lessons from Anti-Amyloid-ß Immunotherapies in Alzheimer Disease: Aiming at a Moving Target.

BACKGROUND: Available drugs for the global Alzheimer disease (AD) epidemic only treat the symptoms without modifying disease progression. Accumulating evidence supports amyloid-ß42 (Aß42)as the key triggering agent in AD, making it the ideal target for disease-modifying therapies. Preclinical studies provided extensive support for passive Aß42 immunotherapy, leading to human clinical trials with different antibodies. OBJECTIVE: Examine the status of clinical trials for passive immunotherapy against Aß42. METHODS: We performed a thorough literature review of passive Aß42 immunotherapy. RESULTS: Ten anti-Aß42 antibodies targeting lineal or conformational epitopes have been tested in clinical trials. Antibody engineering and appropriate dosing have overcome undesired side effects, leading to increased safety profiles. Unfortunately, few trials have shown cognitive protection, leading to legitimate questions about the utility of Aß42 as an AD target. There is still hope that solanezumab, aducanumab, and other ongoing trials will identify antibodies, patient subpopulations, and administration protocols, with consistent clinical benefits. CONCLUSIONS: Despite the overall disappointing results, there is still hope that Aß immunotherapy in presymptomatic patients will prevent neuronal loss and provide significant clinical benefits that can be applied to larger populations as preventive therapies. Advances with other targets may soon provide additional therapeutic options for AD with increased efficacy.

A pqr2 mutant encodes a defective polyamine transporter and is negatively affected by ABA for paraquat resistance in Arabidopsis thaliana.

Despite the paraquat-resistant mutants that have been reported in plants, this study identified a novel A. thaliana mutant (pqr2) from an XVE inducible activation library based on its resistance to 2 µM paraquat. The pqr2 mutant exhibited a termination mutation in the exon of AT1G31830/PAR1/PQR2, encoded a polyamine uptake transporter AtPUT2/PAR1/PQR2. The PQR2 mutation could largely reduce superoxide accumulation and cell death in the pqr2 plants under paraquat treatment. Moreover, compared with wild type, the pqr2 mutant exhibited much reduced tolerance to putrescine, a classic polyamine compound, which confirmed that PQR2 encoded a defective polyamine transporter. Notably, co-treated with ABA and paraquat, both pqr2 mutant and wild type exhibited a lethal phenotype from seed germination, but the wild type like pqr2 mutant, could remain paraquat-resistance while co-treated with high dosage of Na2WO4, an ABA synthesis inhibitor. Gene expression analysis suggested that ABA signaling should widely regulate paraquat-responsive genes distinctively in wild type and pqr2 mutant. Hence, this study has for the first time reported about ABA negative effect on paraquat-resistance in A. thaliana, providing insight into the ABA signaling involved in the oxidative stress responses induced by paraquat in plants.

Efficient enrichment and sensitive detection of polychlorinated biphenyls using nanoflower MIL-on-UiO as solid-phase microextraction fiber coating.

The sensitive detection of polychlorinated biphenyls (PCBs) is crucial for protecting the environment and human health. Herein, we constructed a Materials Institute Lavoisier 88B (MIL-88B)-on-University of Oslo 66 (UiO-66) composite (MIL-on-UiO) with a unique nanoflower morphology, in which highly stable UiO-66 is the precursor, with MIL-88B grown on its surface. MIL-on-UiO was used as a fiber coating for headspace solid-phase microextraction to enrich PCBs. Experimental results demonstrated that MIL-on-UiO provided better enrichment performance for PCBs than single components due to multiple interactions, including π-π stacking, halogen bonding, pore-filling, and steric hindrance effects. The method established using the MIL-on-UiO-based SPME fiber coating provided a good linear relationship in the range of 0.001-50 ng·mL-1, with limits of detection ranging from 0.0002 to 0.002 ng·mL-1 and enrichment factors between 3530 and 7420. In addition, the method was used to detect trace PCBs in water and orange juice achieving satisfactory recoveries (81%-111%).