Reciprocal conversion between annual and polycarpic perennial flowering behavior in the Brassicaceae.

The development of perennial crops holds great promise for sustainable agriculture and food security. However, the evolution of the transition between perenniality and annuality is poorly understood. Here, using two Brassicaceae species, Crucihimalaya himalaica and Erysimum nevadense, as polycarpic perennial models, we reveal that the transition from polycarpic perennial to biennial and annual flowering behavior is a continuum determined by the dosage of three closely related MADS-box genes. Diversification of the expression patterns, functional strengths, and combinations of these genes endows species with the potential to adopt various life-history strategies. Remarkably, we find that a single gene among these three is sufficient to convert winter-annual or annual Brassicaceae plants into polycarpic perennial flowering plants. Our work delineates a genetic basis for the evolution of diverse life-history strategies in plants and lays the groundwork for the generation of diverse perennial Brassicaceae crops in the future.

Imaging surface structure and premelting of ice Ih with atomic resolution.

Ice surfaces are closely relevant to many physical and chemical properties, such as melting, freezing, friction, gas uptake and atmospheric reaction1-8. Despite extensive experimental and theoretical investigations9-17, the exact atomic structures of ice interfaces remain elusive owing to the vulnerable hydrogen-bonding network and the complicated premelting process. Here we realize atomic-resolution imaging of the basal (0001) surface structure of hexagonal water ice (ice Ih) by using qPlus-based cryogenic atomic force microscopy with a carbon monoxide-functionalized tip. We find that the crystalline ice-Ih surface consists of mixed Ih- and cubic (Ic)-stacking nanodomains, forming 19 × 19 periodic superstructures. Density functional theory reveals that this reconstructed surface is stabilized over the ideal ice surface mainly by minimizing the electrostatic repulsion between dangling OH bonds. Moreover, we observe that the ice surface gradually becomes disordered with increasing temperature (above 120 Kelvin), indicating the onset of the premelting process. The surface premelting occurs from the defective boundaries between the Ih and Ic domains and can be promoted by the formation of a planar local structure. These results put an end to the longstanding debate on ice surface structures and shed light on the molecular origin of ice premelting, which may lead to a paradigm shift in the understanding of ice physics and chemistry.

Anisotropic cell growth at the leaf base promotes age-related changes in leaf shape in Arabidopsis thaliana.

Plants undergo extended morphogenesis. The shoot apical meristem (SAM) allows for reiterative development and the formation of new structures throughout the life of the plant. Intriguingly, the SAM produces morphologically different leaves in an age-dependent manner, a phenomenon known as heteroblasty. In Arabidopsis thaliana, the SAM produces small orbicular leaves in the juvenile phase, but gives rise to large elliptical leaves in the adult phase. Previous studies have established that a developmental decline of microRNA156 (miR156) is necessary and sufficient to trigger this leaf shape switch, although the underlying mechanism is poorly understood. Here we show that the gradual increase in miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE transcription factors with age promotes cell growth anisotropy in the abaxial epidermis at the base of the leaf blade, evident by the formation of elongated giant cells. Time-lapse imaging and developmental genetics further revealed that the establishment of adult leaf shape is tightly associated with the longitudinal cell expansion of giant cells, accompanied by a prolonged cell proliferation phase in their vicinity. Our results thus provide a plausible cellular mechanism for heteroblasty in Arabidopsis, and contribute to our understanding of anisotropic growth in plants.

The effect of surface hydrophobicity and hydrophilicity on ion-ion interactions at water-solid interfaces.

Condensation and arrangement of ions at water-solid interfaces are of great importance in the formation of electrical double layers (EDL) and the transport of ions under a confined geometry. So far, the microscopic understanding of interfacial ion configurations is still far from complete, especially when the local ion concentration is high and ion-ion interactions become prominent. In this study, we directly visualized alkali metal cations within the hydrogen-bonding network of water on graphite and Cu(111)-supported graphene surfaces, using qPlus-based noncontact atomic force microscopy (NC-AFM). We found that the codeposition of the alkali cations and water molecules on the hydrophobic graphite surface leads to the formation of an ion-doped bilayer hexagonal ice (BHI) structure, where the ions are repelled from each other and scattered in a disordered distribution. In contrast, the hydrated alkali cations aggregate in one dimension on the more hydrophilic graphene/Cu(111) surface, forming a nematic state with a long-range order. Such a nematic state arises from the delicate interplay between water-ion and water-water interactions under surface confinement. These results reveal the high sensitivity of ion-ion interactions and ionic ordering to the surface hydrophobicity and hydrophilicity.

Arsenic-Hyperaccumulator Pteris vittata Effectively Uses Sparingly-Soluble Phosphate Rock: Rhizosphere Solubilization, Nutrient Improvement, and Arsenic Accumulation.

Sparingly-soluble phosphate rock (PR), a raw material for P-fertilizer production, can be effectively utilized by the As-hyperaccumulator Pteris vittata but not most plants. In this study, we investigated the associated mechanisms by measuring dissolved organic carbon (DOC) and acid phosphatase in the rhizosphere, and nutrient uptake and gene expression related to the As metabolism in P. vittata. The plants were grown in a soil containing 200 mg kg-1 As and/or 1.5% PR for 30 days. Compared to the As treatment, the P. vittata biomass was increased by 33% to 4.6 g plant-1 in the As+PR treatment, corresponding to 27% decrease in its frond oxidative stress as measured by malondialdehyde. Due to PR-enhanced DOC production in the rhizosphere, the Ca, P, and As contents in P. vittata fronds were increased by 17% to 9.7 g kg-1, 29% to 5.0 g kg-1, and 57% to 1045 mg kg-1 in the As+PR treatment, thereby supporting its better growth. Besides, PR-induced rhizosphere pH increase from 5.0 to 6.9 promoted greater P uptake by P. vittata probably via upregulating low-affinity P transporters PvPTB1;1/1;2 by 3.7-4.1 folds. Consequently, 29% lower available-P induced the 3.3-fold upregulation of high-affinity P transporter PvPht1;3 in the As+PR treatment, which was probably responsible for the 58% decrease in available-As content in the rhizosphere. Consistent with the enhanced As translocation and sequestration, arsenite antiporters PvACR3/3;3 were upregulated by 1.8-4.4 folds in the As+PR than As treatment. In short, sparingly-soluble PR enhanced the Ca, P, and As availability in P. vittata rhizosphere and improved their uptake via upregulating genes related to As metabolism, suggesting its potential application for improving phytoremediation in As-contaminated soils.

Dual inhibition of oxidative phosphorylation and glycolysis to enhance cancer therapy.

Dual suppression of oxidative phosphorylation (OXPHOS) and glycolysis can disrupt metabolic adaption of cancer cells, inhibiting energy supply and leading to successful cancer therapy. Herein, we have developed an α-tocopheryl succinate (α-TOS)-functionalized iridium(III) complex Ir2, a highly lipophilic mitochondria targeting anticancer molecule, could inhibit both oxidative phosphorylation (OXPHOS) and glycolysis, resulting in the energy blockage and cancer growth suppression. Mechanistic studies reveal that complex Ir2 induces reactive oxygen species (ROS) elevation and mitochondrial depolarization, and triggers DNA oxidative damage. These damages could evoke the cancer cell death with the mitochondrial-relevant apoptosis and autophagy. 3D tumor spheroids experiment demonstrates that Ir2 owned superior antiproliferation performance, as the potent anticancer agent in vivo. This study not only provided a new path for dual inhibition of both mitochondrial OXPHOS and glycolytic metabolisms with a novel α-TOS-functionalized metallodrug, but also further demonstrated that the mitochondrial-relevant therapy could be effective in enhancing the anticancer performance.

Total contents, fractionation and bioaccessibility of nine heavy metals in household dust from 14 cities in China.

The potential health risk caused by long-term exposure to heavy metals in household dust is not only depended on their total content, but also bioaccessibility. In this study, twenty-one dust samples were collected from residential buildings, schools, and laboratories in 14 provincial-capital/industrial cities of China, aiming to evaluate the total contents, fractionation, bioaccessibility and health risks of nine heavy metals (As, Cd, Cr, Ni, Pb, Mn, Zn, Fe, and Cu). Results showed that the highest levels of Cd, Cr, Ni and Zn were found in laboratory dust, As, Pb and Mn in school dust, and Fe and Cu in residential dust, indicating different source profiles of the heavy metals. The mean bioaccessibility of the heavy metals across all samples as evaluated using SBRC (Solubility Bioavailability Research Consortium), IVG (In Vitro Gastrointestinal), and PBET (Physiologically Based Extraction Test) assays was 58.4%, 32.4% and 17.2% in gastric phase (GP), and 24.9%, 21.9% and 9.39% in intestinal phase (IP), respectively. Cadmium had the highest content in the fractions of E1+C2 (43.7%), as determined by sequential extraction, and Pb, Mn, and Zn had a higher content in E1+C2+F3 (64.2%, 67.2%, 78.8%), resulting in a higher bioaccessibility of these heavy metals than others. Moreover, the bioaccessibility of most heavy metals was inversely related to dust pH (R = -0.18 in GP; -0.18 in IP; P < 0.01) and particle size, while a positive correlation was observed with total organic carbon (R = 0.40 in GP; 0.38 in IP; P < 0.01). The exposure risk calculated by the highest bioaccessibility was generally lower than that calculated by the total content. However, Pb in one school dust sample had an unacceptable carcinogenic risk (adult risk = 1.19 × 10-4; child risk = 1.08 × 10-4). This study suggests that bioaccessibility of heavy metals in household dust is likely related to geochemical fractions and physical/chemical properties. Further research is needed to explore the sources of bioaccessible heavy metals in household dust.

Transcriptomics, proteomics, and metabolomics interventions prompt crop improvement against metal(loid) toxicity.

The escalating challenges posed by metal(loid) toxicity in agricultural ecosystems, exacerbated by rapid climate change and anthropogenic pressures, demand urgent attention. Soil contamination is a critical issue because it significantly impacts crop productivity. The widespread threat of metal(loid) toxicity can jeopardize global food security due to contaminated food supplies and pose environmental risks, contributing to soil and water pollution and thus impacting the whole ecosystem. In this context, plants have evolved complex mechanisms to combat metal(loid) stress. Amid the array of innovative approaches, omics, notably transcriptomics, proteomics, and metabolomics, have emerged as transformative tools, shedding light on the genes, proteins, and key metabolites involved in metal(loid) stress responses and tolerance mechanisms. These identified candidates hold promise for developing high-yielding crops with desirable agronomic traits. Computational biology tools like bioinformatics, biological databases, and analytical pipelines support these omics approaches by harnessing diverse information and facilitating the mapping of genotype-to-phenotype relationships under stress conditions. This review explores: (1) the multifaceted strategies that plants use to adapt to metal(loid) toxicity in their environment; (2) the latest findings in metal(loid)-mediated transcriptomics, proteomics, and metabolomics studies across various plant species; (3) the integration of omics data with artificial intelligence and high-throughput phenotyping; (4) the latest bioinformatics databases, tools and pipelines for single and/or multi-omics data integration; (5) the latest insights into stress adaptations and tolerance mechanisms for future outlooks; and (6) the capacity of omics advances for creating sustainable and resilient crop plants that can thrive in metal(loid)-contaminated environments.

Cell division in the shoot apical meristem is a trigger for miR156 decline and vegetative phase transition in Arabidopsis.

What determines the rate at which a multicellular organism matures is a fundamental question in biology. In plants, the decline of miR156 with age serves as an intrinsic, evolutionarily conserved timer for the juvenile-to-adult phase transition. However, the way in which age regulates miR156 abundance is poorly understood. Here, we show that the rate of decline in miR156 is correlated with developmental age rather than chronological age. Mechanistically, we found that cell division in the apical meristem is a trigger for miR156 decline. The transcriptional activity of MIR156 genes is gradually attenuated by the deposition of the repressive histone mark H3K27me3 along with cell division. Our findings thus provide a plausible explanation of why the maturation program of a multicellular organism is unidirectional and irreversible under normal growth conditions and suggest that cell quiescence is the fountain of youth in plants.

Multi-imaging platform for rhizosphere studies: Phosphorus and oxygen fluxes.

Rhizosphere is a soil volume of high spatio-temporal heterogeneity and intensive plant-soil-microbial interactions, for which visualization and process quantification is of highest scientific and applied relevance, but still very challenging. A novel methodology for quick assessment of two-dimensional distribution of available phosphorus (P) in rhizosphere was suggested, tested, and development up to the application platform. Available P was firstly trapped by an in-situ diffusive gradients in thin-films (DGT) sampler with precipitated zirconia as the binding gel, and subsequently, the loaded gel was analyzed with an optimized colorimetric imaging densitometry (CID). The imaging platform was established linking: i) DGT, ii) planar optode, and iii) soil zymography techniques to simultaneously determine available P, oxygen, and acid phosphatase in rhizosphere at sub-millimeter spatial scales. The DGT identified available P level in rice rhizosphere were spatially overlapping to the localized redox hotspots and phosphatase activity. The spatial relationship between available P and acid phosphatase activity was dependent on root development. The root radial oxygen loss (ROL) remained active during the experimental observations (2-3 days), while a flux of available P of 10 pg cm-2 s-1 was visualized within 2-3 mm of roots, confirming the correlative response of rice roots to oxygen secretion and P uptake. Summarizing, the established imaging platform is suitable to capture spatial heterogeneity and temporal dynamics of root activities, nutrient bioavailability, ROL and enzyme activities in rhizosphere.

AP2/ERF Transcription Factors Integrate Age and Wound Signals for Root Regeneration.

Age and wounding are two major determinants for regeneration. In plants, the root regeneration is triggered by wound-induced auxin biosynthesis. As plants age, the root regenerative capacity gradually decreases. How wounding leads to the auxin burst and how age and wound signals collaboratively regulate root regenerative capacity are poorly understood. Here, we show that the increased levels of three closely-related miR156-targeted Arabidopsis (Arabidopsis thaliana) SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors, SPL2, SPL10, and SPL11, suppress root regeneration with age by inhibiting wound-induced auxin biosynthesis. Mechanistically, we find that a subset of APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factors including ABSCISIC ACID REPRESSOR1 and ERF109 is rapidly induced by wounding and serves as a proxy for wound signal to induce auxin biosynthesis. In older plants, SPL2/10/11 directly bind to the promoters of AP2/ERFs and attenuates their induction, thereby dampening auxin accumulation at the wound. Our results thus identify AP2/ERFs as a hub for integration of age and wound signal for root regeneration.

Mechanistic Insights into the Biodegradation of Carbon Dots by Fungal Laccase.

While carbon dots (CDs) have the potential to support the agricultural revolution, it remains obscure about their environmental fate and bioavailability by plants. Fungal laccase-mediated biotransformation of carbon nanomaterials has received little attention despite its known capacity to eliminate recalcitrant contaminants. Herein, we presented the initial investigation into the transformation of CDs by fungal laccase. The degradation rates of CDs were determined to be first-order in both substrate and enzyme. Computational docking studies showed that CDs preferentially bonded to the pocket of laccase on the basal plane rather than the edge through hydrogen bonds and hydrophobic interactions. Electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) and other characterizations revealed that the phenolic/amino lignins and tannins portions in CDs are susceptible to laccase transformation, resulting in graphitic structure damage and smaller-sized fragments. By using the 13C stable isotope labeling technique, we quantified the uptake and translocation of 13C-CDs by mung bean plants. 13C-CDs (10 mg L-1) accumulated in the root, stem, and leaf were estimated to be 291, 239, and 152 µg g-1 at day 5. We also evidenced that laccase treatment alters the particle size and surface chemistry of CDs, which could facilitate the uptake of CDs by plants and reduce their nanotoxicity to plants.

Preoperative prognostic nutrition index can independently predict the 6-month prognosis of elderly patients undergoing neurosurgical clipping for aneurysmal subarachnoid hemorrhage.

The number of elderly patients with aneurysmal subarachnoid hemorrhage (aSAH) is increasing annually. The prognostic nutritional index (PNI) is used as a novel and valuable prognostic marker for various neoplastic diseases and other critical illnesses. This study aimed to identify the short-term prognostic value of preoperative PNI in elderly patients who underwent neurosurgical clipping for aSAH. This retrospective study included elderly patients with aSAH who underwent neurosurgical clipping from January 2018 to December 2020. Clinical variables and 6-month outcomes were collected and compared. Epidemiological data and effect factors of prognosis were evaluated. Multivariate logistic regression and receiver operating characteristics (ROC) curve analyses were used to evaluate the predictive value of preoperative PNI. Multiple logistic regression was performed to establish a nomogram. A total of 124 elderly patients were enrolled. Multivariate logistic regression analysis showed that preoperative PNI (odds ratio (OR), 0.779; 95% confidence interval (CI), 0.689-0.881; P < 0.001), Hunt-Hess grade (OR, 3.291; 95%CI, 1.816-5.966; P < 0.001), and hydrocephalus (OR, 9.423; 95%CI, 2.696-32.935; P < 0.001) were significant predictors. The area under the ROC curve of PNI was 0.829 (95% CI, 0.755-0.903; P < 0.001) with a sensitivity and specificity of 68.4% and 83.3%, respectively, and the cutoff value was 46.36. Patients with preoperative PNI of < 46.36 had a significantly unfavorable 6-months prognosis (F = 40.768, P < 0.001). Preoperative PNI is independently correlated with the 6-month prognosis in elderly patients who undergo neurosurgical clipping for aSAH.

Human nails as a valuable noninvasive alternative for estimating exposure to parabens.

Exposure of human to parabens (commonly used preservatives) is inevitable due to their extensively applied in numerous consumer products. Thus, a reliable noninvasive matrix reflecting long-term exposure to parabens is essential for human biomonitoring study. Human nails are potentially a valuable alternative for measuring intergrated exposure to parabens. In this work, we collected 100 paired nail and urine samples from university students in Nanjing, China, and measured simultaneously for six parent parabens and four metabolites. Methylparaben (MeP), ethylparaben (EtP), and propylparaben (PrP) were three predominant paraben analogue in both matrices, with the median concentrations being 12.9, 0.753, and 3.42 ng/mL in urine, and 1540, 154, and 961 ng/g in nail, respectively, while 4-hydroxybenzoic acid (4-HB) and 3,4-dihydroxybenzoic acid (3,4-DHB) were the most abundant metabolites (median values of 143 and 35.9 ng/mL, respectively) in urine. Gender-related analysis suggested that females exposed to more higher parabens than males. Significantly positive correlations were found between levels of MeP, PrP, EtP, and OH-MeP (r = 0.54-0.62, p < 0.01) in paired urine and nail samples. Our result here suggests that human nails, as an emerging biospecimen, are a potentially valuable biological matrix to evaluate human long-term exposure to parabens.

Comparison of in vitro strategies for predicting Dichlorodiphenyltrichloroethane (DDT) and its metabolites bioavailability from soils.

In vitro strategies have widely been used to assess bioaccessibility of organic pollutants in soils. However, studies for comparing in vitro models with in vivo data are still limited. In this study, Dichlorodiphenyltrichloroethane (DDT) and its metabolites (called as DDTr) bioaccessibility in nine contaminated soils were measured using physiologically based extraction test (PBET), in vitro digestion model (IVD), and Deutsches Institut für Normung (DIN) with/without Tenax as an absorptive sink, and DDTr bioavailability was assessed using an in vivo mouse model. Whether or not Tenax was added, DDTr bioaccessibility significantly varied among three methods, suggesting that DDTr bioaccessibility depended on the in vitro method employed. Multiple linear regression analysis indicated that sink, intestinal incubation time and bile content are identified to be the dominant factors in controlling DDTr bioaccessibility. Comparison of in vitro and in vivo results demonstrated that DIN assay with Tenax (TI-DIN) provided the best prediction for DDTr bioavailability (r2 = 0.66, slope=0.78). After extending intestinal incubation time to 6 h or increasing bile content to 4.5 g/L (same to DIN assay) of the TI-PBET and TI-IVD assays, the in vivo-in vitro correlation will improved significantly, with r2 = 0.76 and slope= 1.4 for TI-PBET and r2 = 0.84 and slope= 1.9 for TI-IVD under 6 h intestinal incubation, and r2 = 0.59 and slope= 0.96 for TI-PBET and r2 = 0.51 and slope= 1.0 for TI-IVD under 4.5 g/L of bile content. The results suggest that it is essential to understand these key factors influencing bioaccessibility for the development of standardized in vitro methods, which helps to refine the risk assessment of human exposure to contaminants via soil ingestion.

Enhanced lead phytoextraction and soil health restoration through exogenous supply of organic ligands: Geochemical modeling".

Phytoremediation of lead (Pb) contaminated soil is a green technology to reduce Pb exposure and root exudates-derived organic acids play a vital role in this treatment process. In this study, Pb hyperaccumulator Pelargonium hortorum was chosen to investigate root-induced organic acid secretions and their subsequent role in Pb phytoextraction. In the first step, root exudation of P. hortorum was investigated in hydroponic experiments (0.2X Hoagland solution) under control and Pb stress conditions. Possible chemical interactions between Pb and the observed root exudates were then analyzed using Visual MINTEQ modeling. In the next step, the effects of the exogenous application of organic acids on Pb phytoextraction and soil enzymatic activities were studied in a pot experimental setup. Results indicated significant exudation of malic acid > citric acid > oxalic acid > tartaric acid in root exudates of P. hortorum under 50 mg L-1 Pb. Visual MINTEQ modeling results revealed that organic acids directly affect Pb dissolution in the nutrient solution by modulation of solution pH. Experimental results revealed that malic acid and citric acid significantly increased available Pb contents (7.2- and 6.7-folds) in the soil with 1500 mg kg-1 Pb contamination. Whereas, in shoot and root, the highest increase in Pb concentration was observed with citric acid (2.01-fold) and malic (3.75-fold) supplements, respectively. Overall, Pb uptake was notably higher when malic acid was applied (2.8-fold) compared to other organic acids, followed by citric acid (2.7-fold). In the case of soil enzymatic activities, oxalic acid significantly improved dehydrogenase, alkaline phosphatase, and microbial biomass by 1.6-, 1.4- and 1.3-folds, respectively. The organic acids were successful in reviving enzyme activity in Pb-contaminated soil, and might thus be used for long-term soil regeneration.

FindIT2: an R/Bioconductor package to identify influential transcription factor and targets based on multi-omics data.

BACKGROUND: Transcription factors (TFs) play central roles in regulating gene expression. With the rapid growth in the use of high-throughput sequencing methods, there is a need to develop a comprehensive data processing and analyzing framework for inferring influential TFs based on ChIP-seq/ATAC-seq datasets. RESULTS: Here, we introduce FindIT2 (Find Influential TFs and Targets), an R/Bioconductor package for annotating and processing high-throughput multi-omics data. FindIT2 supports a complete framework for annotating ChIP-seq/ATAC-seq peaks, identifying TF targets by the combination of ChIP-seq and RNA-seq datasets, and inferring influential TFs based on different types of data input. Moreover, benefited from the annotation framework based on Bioconductor, FindIT2 can be applied to any species with genomic annotations, which is particularly useful for the non-model species that are less well-studied. CONCLUSION: FindIT2 provides a user-friendly and flexible framework to generate results at different levels according to the richness of the annotation information of user's species. FindIT2 is compatible with all the operating systems and is released under Artistic-2.0 License. The source code and documents are freely available through Bioconductor ( https://bioconductor.org/packages/devel/bioc/html/FindIT2.html ).

Selenium Increased Arsenic Accumulation by Upregulating the Expression of Genes Responsible for Arsenic Reduction, Translocation, and Sequestration in Arsenic Hyperaccumulator Pteris vittata.

Selenate enhances arsenic (As) accumulation in As-hyperaccumulator Pteris vittata, but the associated molecular mechanisms are unclear. Here, we investigated the mechanisms of selenate-induced arsenic accumulation by exposing P. vittata to 50 µM arsenate (AsV50) and 1.25 (Se1.25) or 5 µM (Se5) selenate in hydroponics. After 2 weeks, plant biomass, plant As and Se contents, As speciation in plant and growth media, and important genes related to As detoxification in P. vittata were determined. These genes included P transporters PvPht1;3 and PvPht1;4 (AsV uptake), arsenate reductases PvHAC1 and PvHAC2 (AsV reduction), and arsenite (AsIII) antiporters PvACR3 and PvACR3;2 (AsIII translocation) in the roots, and AsIII antiporters PvACR3;1 and PvACR3;3 (AsIII sequestration) in the fronds. The results show that Se1.25 was more effective than Se5 in increasing As accumulation in both P. vittata roots and fronds, which increased by 27 and 153% to 353 and 506 mg kg-1. The As speciation analyses show that selenate increased the AsIII levels in P. vittata, with 124-282% more AsIII being translocated into the fronds. The qPCR analyses indicate that Se1.25 upregulated the gene expression of PvHAC1 by 1.2-fold, and PvACR3 and PvACR3;2 by 1.0- to 2.5-fold in the roots, and PvACR3;1 and PvACR3;3 by 0.6- to 1.1-fold in the fronds under AsV50 treatment. Though arsenate enhanced gene expression of P transporters PvPht1;3 and PvPht1;4, selenate had little effect. Our results indicate that selenate effectively increased As accumulation in P. vittata, mostly by increasing reduction of AsV to AsIII in the roots, AsIII translocation from the roots to fronds, and AsIII sequestration into the vacuoles in the fronds. The results suggest that selenate may be used to enhance phytoremediation of As-contaminated soils using P. vittata.

Assessment of DDT and its Metabolites Bioaccessibility in Historically Contaminated Soils Using Unfed and Fed in Vitro Methods.

Bioaccessibility of hydrophobic organic contaminants (HOCs) from unintentional ingestion of soil is increasingly assessed with in vitro gastrointestinal models incorporating a sorption sink. In this study, the bioaccessibility of DDTs in contaminated soils (n = 11) was determined using "unfed" unified bioaccessibility method (UBM) and fed organic estimation human simulation test (FOREhST) with/without Tenax as an absorbent. By adding Tenax, the bioaccessibility of DDTs determined using UBM was significantly increased from 4.9-30.6% to 31.6-86.0%. In contrast, the bioaccessibility of DDTs determined using FOREhST without/with Tenax were similar with values of 20.0-60.9% vs 31.5-47.6%, implying that the influence of food components on the absorption efficiency of the sink should not be overlooked. Much high fraction of DDTs (bioaccessibility: 11.7-24.8%) remained in FOREhST supernatant after Tenax collection, suggesting that prediction of bioavailability through bioaccessibility obtained by absorbent needs to be treated with caution when bioaccessibility is determined using a "fed state" in vitro method.

Environmentally relevant concentrations of arsenic induces apoptosis in the early life stage of zebrafish.

Arsenic (As) in the aquatic environment is a considerable environmental issue, previous studies have reported the toxic effects of low concentrations (≤ 150 µg/L) of As on fish. However, limited information is available regarding the impact of low levels of As on apoptosis. To evaluate this, zebrafish embryos were exposed to different concentrations (0, 25, 50, 75, and 150 µg/L) of As (arsenite [AsIII] and arsenate [AsV]) for 120 h. Our results indicated that low concentrations of AsIII exposure significantly inhibited the survival of zebrafish larvae, and significantly increased the transcription of Caspase-9 and Caspase-3, the ratio of Bax/Bcl-2 transcription, and protein levels of Caspase-3. In contrast, AsV decreased the ratios of Bax/Bcl-2 transcription and protein levels, as well as protein levels of Caspase-3. Our data demonstrated that AsIII and AsV exert different toxic effects, AsIII induced apoptosis via the mitochondrial pathway and the extrinsic pathway, while AsV induced apoptosis only via the mitochondrial pathway.