Insights into mechanisms involved in the uptake, translocation, and metabolism of phthalate esters in Chinese cabbage (Brassica rapa var. chinensis)

Insights into the Enantiomeric Uptake, Translocation, and Distribution of Triazole Chiral Pesticide Mefentrifluconazole in Wheat (Triticum aestivum L.)

The uptake, translocation, and accumulation of mefentrifluconazole (MFZ), an innovative chiral triazole fungicide, in plants at the enantiomeric level are still unclear. Herein, we investigated the patterns and mechanisms of enantiomeric uptake, bioaccumulation, and translocation through several experiments. Rac-MFZ shows the strongest uptake and bioaccumulation capacity in wheat compared with its enantiomers, while S-(+)-MFZ has the highest translocation potential. Molecular docking provided evidence of the stronger translocation ability of S-(+)-MFZ than R-(-)-MFZ. Split-root experiments showed that MFZ and its enantiomers could undergo long-distance transport within the wheat. Active transport or facilitated and simple diffusion may be involved in the wheat uptake of MFZ. The limited acropetal translocation capability of MFZ may be attributed to the dominant uptake pathway of apoplastic. The concentrations of Rac-MFZ in different subcellular fractions varied greatly. In summary, this study provides novel insights for further understanding the behaviors of MFZ and its enantiomers in plants.

Insight into the fate of tolfenpyrad in tea plant (Camellia sinensis L.) from root uptake

Residual pesticides in agricultural environments, including soil and irrigation water, can be taken up by plants, and thus pose a potential risk to food safety. Although tolfenpyrad has been widely used in tea plantations, limited information is available on its root uptake and fate in tea plants (Camellia sinensis L.). Exploring the mechanisms involved is crucial for understanding the migration and accumulation of tolfenpyrad in tea plants, particularly in the edible parts. In this study, root uptake of tolfenpyrad and its subsequent translocation, distribution, and metabolism in tea seedlings were investigated. The results indicated that the passive transport and apoplastic pathway dominated the root uptake of tolfenpyrad. After uptake, tolfenpyrad distributed predominantly in the cell walls (90.8-92.0 %) of roots, resulting in limited upward translocation in water-soluble fractions through transpirational pull, with translocation factor values far <1 (TFstem/root = 0.115-0.453 and TFleaf/stem = 0.039-0.184). Similar accumulation patterns were observed for the carboxylated metabolite PT-CA as well as hydroxylated metabolite PT-OH. Interestingly, the subcellular distribution of PT-CA in stems was much different from that of the parent tolfenpyrad: PT-CA mainly distributed in the stem cell walls (41.72 %) and cell organelles (56.18 %) at 3 h, then gradually transferred into the cell-soluble fractions (33.07 %) after 120 h. Results from the present study indicated limited upward translocation of tolfenpyrad with its main metabolites to leaves. This finding helps to alleviate concerns about environmental residual tolfenpyrad in tea consumption and provides valuable information for the safety evaluation of tolfenpyrad.

Phthalate monoesters accumulation in residential indoor dust and influence factors

Phthalate monoesters (mPAEs) possess biological activity that matches or even exceeds that of their parent compounds, phthalate esters (PAEs), negatively impacting humans. Indoor dust is the main carrier of indoor pollutants. In this study, indoor dust samples were collected from 46 households in Changchun City, Jilin Province, in May 2019, and particulate and flocculent fibrous dust was used as the research target to analyze the concentration and compositional characteristics of mPAEs, primary metabolites of five significant PAEs. The influence of factors such as architectural features and living habits in residential areas on exposure to mPAEs was explored. Ten suspected enzyme genes along with two metabolic pathways with the ability to degrade PAEs were screened using PICRUSt2. The results showed that the total concentrations of the five mPAEs in the indoor dust samples were particulate dust (11.49-78.69 μg/g) and flocculent fibrous dust (21.61-72.63 μg/g), respectively. The molar concentration ratio (RC) of mPAEs to corresponding PAEs significantly differed among chemicals, with MMP/DMP and MEP/DEP sporting the highest RC values. Different bacterial types have shown distinct influences against mPAEs and PAEs. Enzyme function and metabolic pathway abundance had a significant effect on the concentration of some mPAEs, mPAEs are most likely derived from microbial degradation of PAEs.

The concentrations and behavior of classic phthalates and emerging phthalate alternatives in different environmental matrices and their biological health risks

Because of their excellent plasticity, phthalates or phthalic acid esters (PAEs) are widely used in plastic products. However, due to the recognized toxicity of PAEs and legislative requirements, the production and use of emerging PAE alternatives have rapidly grown, such as di-isononyl cyclohexane-1,2-dicarboxylate (DINCH) and di(2-ethylhexyl) terephthalate (DEHTP) which are the primary replacements for classic PAEs. Nowadays, PAEs and emerging PAE alternatives are frequently found in a variety of environmental media, including the atmosphere, sludge, rivers, and seawater/sediment. PAEs and emerging PAE alternatives are involved in endocrine-disrupting effects, and they affect the reproductive physiology of different species of fish and mammals. Therefore, their presence in the environment is of considerable concern due to their potential effects on ecosystem function and public health. Nevertheless, current research on the prevalence, destiny, and conduct of PAEs in the environment has primarily focused on classic PAEs, with little attention given to emerging PAE alternatives. The present article furnishes a synopsis of the physicochemical characteristics, occurrence, transport, fate, and adverse effects of both classic PAEs and emerging PAE alternatives on organisms in the ecosystem. Our analysis reveals that both classic PAEs and emerging PAE alternatives are widely distributed in all environmental media, with emerging PAE alternatives increasingly replacing classic PAEs. Various pathways can transform and degrade both classic PAEs and emerging PAE alternatives, and their own and related metabolites can have toxic effects on organisms. This research offers a more extensive comprehension of the health hazards associated with classic PAEs and emerging PAE alternatives.

Root-zone regulation and longitudinal translocation cause intervarietal differences for phthalates accumulation in vegetables

Selecting and cultivating low-accumulating crop varieties (LACVs) is the most effective strategy for the safe utilization of di-(2-ethylhexyl) phthalate (DEHP)-contaminated soils, promoting cleaner agricultural production. However, the adsorption-absorption-translocation mechanisms of DEHP along the root-shoot axis remains a formidable challenge to be solved, especially for the research and application of LACV, which are rarely reported. Here, systematic analyses of the root surface ad/desorption, root apexes longitudinal allocation, uptake and translocation pathway of DEHP in LACV were investigated compared with those in a high-accumulating crop variety (HACV) in terms of the root-shoot axis. Results indicated that DEHP adsorption was enhanced in HACV by root properties, elemental composition and functional groups, but the desorption of DEHP was greater in LACV than HACV. The migration of DEHP across the root surface was controlled by the longitudinal partitioning process mediated by root tips, where more DEHP accumulated in the root cap and meristem of LACV due to greater cell proliferation. Furthermore, the longitudinal translocation of DEHP in LACV was reduced, as evidenced by an increased proportion of DEHP in the root apoplast. The symplastic uptake and xylem translocation of DEHP were suppressed more effectively in LACV than HACV, because DEHP translocation in LACV required more energy, binding sites and transpiration. These results revealed the multifaceted regulation of DEHP accumulation in different choysum (Brassica parachinensis L.) varieties and quantified the pivotal regulatory processes integral to LACV formation.

Phthalate acid esters: A review of aquatic environmental occurrence and their interactions with plants

The increasing use of phthalate acid esters (PAEs) in various applications has inevitably led to their widespread presence in the aquatic environment. This presents a considerable threat to plants. However, the interactions between PAEs and plants in the aquatic environment have not yet been comprehensively reviewed. In this review, the properties, occurrence, uptake, transformation, and toxic effects of PAEs on plants in the aquatic environment are summarized. PAEs have been prevalently detected in the aquatic environment, including surface water, groundwater, seawater, and sediment, with concentrations ranging from the ng/L or ng/kg to the mg/L or mg/kg range. PAEs in the aquatic environment can be uptake, translocated, and metabolized by plants. Exposure to PAEs induces multiple adverse effects in aquatic plants, including growth perturbation, structural damage, disruption of photosynthesis, oxidative damage, and potential genotoxicity. High-throughput omics techniques further reveal the underlying toxicity molecular mechanisms of how PAEs disrupt plants on the transcription, protein, and metabolism levels. Finally, this review proposes that future studies should evaluate the interactions between plants and PAEs with a focus on long-term exposure to environmental PAE concentrations, the effects of PAE alternatives, and human health risks via the intake of plant-based foods.

Unveiling the absorption, translocation, and metabolism of penthiopyrad in pakchoi under hydroponic and soil-cultivated conditions

The efficient use of pesticides has long been a topic of public concern, necessitating a thorough understanding of their movement in plants. This study investigates the translocation and distribution of penthiopyrad in pakchoi plants cultivated both in hydroponic and soil-cultivated conditions. Results indicate that penthiopyrad predominantly accumulates in the roots, with concentrations of 11.3-53.9 mg/kg following root application, and in the leaves, with concentrations of 2.0-17.1 mg/kg following foliar application. The bioconcentration factor exceeded 1, with values ranging from 1.2 to 23.9 for root application and 6.4 to 164.0 for foliar application, indicating a significant role in the absorption and accumulation processes. The translocation factor data, which were <1, suggest limited the translocations within pakchoi plants. The limitation may be attributed to the hydrophobic properties of penthiopyrad (log Kow = 3.86), as evidenced by its predominant distribution in the subcellular solid fractions of pakchoi tissues, accounting for 93.1% to 99.5% of the total proportion. Six metabolites (753-A-OH, M12, 754-T-DO, M11, PCA, and PAM) were identified in this study as being formed during this process. These findings provide valuable insights into the absorption, translocation, and metabolism of penthiopyrad in pakchoi.

Accumulation characteristics of liquid crystal monomers in plants: A multidimensional analysis

Liquid crystal monomers (LCMs), identified as emerging contaminations, have been detected in soils and plants, but their accumulation characteristics in plants haven't been studied. Therefore, this study systematically investigated the accumulation characteristics of LCMs in plants from four dimensions (i.e., plant fruit species, soil types, plant growth stages, and LCMs categories) for the first time. The LCMs concentrations (9.96 × 10-4 to 114.608 ng/g) in 22 plant fruits were predicted by the partition-limited model. Grains with the highest lipid content showed the highest LCMs accumulation propensity. Plants grown in paddy soil showed a strong LCMs accumulation capacity. Results showed that the LCMs accumulation capacity in plants from soils decreased when the soil organic matter content increased. A preferential accumulation of LCMs in plant root systems during growth was found by the molecular dynamics simulations. Compared to polychlorinated biphenyls (as the reference contaminants of LCMs), LCMs exhibit higher accumulation in plant roots and lower translocation to shoots. For the fourth dimension, lipophilicity was found to be the main reason of LCMs accumulation by intergraded stepwise linear regression with sensitivity analysis. This is the inaugural research concentrating on LCMs accumulation in plants, providing insights and theoretical guidance for future LCMs management strategies multidimensionally.

Congener-specific uptake and accumulation of bisphenols in edible plants: Binding to prediction of bioaccumulation by attention mechanism multi-layer perceptron machine learning model

Plant accumulation of phenolic contaminants from agricultural soils can cause human health risks via the food chain. However, experimental and predictive information for plant uptake and accumulation of bisphenol congeners is lacking. In this study, the uptake, translocation, and accumulation of five bisphenols (BPs) in carrot and lettuce plants were investigated through hydroponic culture (duration of 168 h) and soil culture (duration of 42 days) systems. The results suggested a higher bioconcentration factor (BCF) of bisphenol AF (BPAF) in plants than that of the other four BPs. A positive correlation was found between the log BCF and the log Kow of BPs (R2carrot = 0.987, R2lettuce = 0.801, P < 0.05), while the log (translocation factor) exhibited a negative correlation with the log Kow (R2carrot = 0.957, R2lettuce = 0.960, P < 0.05). The results of molecular docking revealed that the lower binding energy of BPAF with glycosyltransferase, glutathione S-transferase, and cytochrome P450 (-4.34, -4.05, and -3.52 kcal/mol) would be responsible for its higher accumulation in plants. Based on the experimental data, an attention mechanism multi-layer perceptron (AM-MLP) model was developed to predict the BCF of eight untested BPs by machine learning, suggesting the relatively high BCF of bisphenol BP, bisphenol PH, and bisphenol TMC (BCFcarrot = 1.37, 1.50, 1.03; BCFlettuce = 1.02, 0.98, 0.67). The prediction of BCF for ever-increasing varieties of BPs by machine learning would reduce repetitive experimental tests and save resources, providing scientific guidance for the production and application of BPs from the perspective of priority pollutants.

Enantioselective uptake, translocation, and biotransformation of pydiflumetofen in wheat (Triticum aestivum L.): Insights from chiral profiling and molecular simulation

Pydiflumetofen (PYD), a highly effective and broad-spectrum fungicide, is commonly employed for the control of fungal diseases. In this study, the uptake, translocation, and biotransformation of PYD by wheat (Triticum aestivum L.) were firstly investigated at a chiral level. The findings revealed that the residue concentration of R-PYD in wheat was higher than that of S-PYD, because of its higher uptake rate (k1 = 0.0421 h-1) and lower elimination rate (k2 = 0.0459 h-1). Additionally, R-PYD exhibited higher root bioconcentration factors and translocation factors compared with S-enantiomer, indicating R-PYD was more easily accumulating in roots and translocating to shoots. Furthermore, a total of 9 metabolites, including hydroxylated, demethylated, demethoxylated, dechlorinated, hydrolyzed, and glycosylated-conjugated products, were detected qualitatively in wheat roots or shoots. Symplastic pathway-mediated uptake, which predominantly relied on aquaporins and anion channels, was confirmed by root adsorption and inhibition experiments, without displaying any enantioselective effect. Molecular simulations demonstrated that R-PYD exhibited stronger binding affinity with TaLTP 1.1 with a lower grid score (-6.79 kcal/mol), whereas weaker interaction with the metabolic enzyme (CYP71C6v1) compared to the S-enantiomer. These findings highlight the significance of plant biomacromolecules in the enantioselective bioaccumulation and biotransformation processes. Importantly, a combination of experimental and theoretical evidence provide a comprehensive understanding of the fate of chiral pesticides in plants from an enantioselective perspective.

In vitro and in silico perspectives on the activation of antioxidant responsive element by citrus-derived flavonoids

Introduction

Oxidative stress plays an essential role in the pathogenesis of chronic diseases. Disrupting the Keap1-Nrf2 pathway by binding Keap1 is identified as a potential strategy to prevent oxidative stress-related chronic diseases. Therefore, of special interest is the utilization of dietary antioxidations from citrus, including narirutin, naringenin, hesperetin, hesperidin, naringin, neohesperidin dihydrochalcone, neohesperidin, and nobiletin, has been exploited as a prospective way to treat or prevent several human pathologies as Keap1-Nrf2 inhibitors for modulation of antioxidant properties.

Methods

To probe into the structural foundation of the molecular identification of citrus-derived antioxidations, we calculated the antioxidant responsive element activation ability of citrus-derived flavonoids after binding with Keap1. Also, the quantum chemistry properties and binding mode were performed theoretically with frontier molecular orbitals, molecular electrostatic potential analysis, molecular docking, and absorption, distribution, metabolism, excretion (ADME) calculation.

Results and discussion

Experimental findings combining computational assays revealed that the tested citrus-derived flavonoids can be grouped into strong agonists and weak agonists. The citrus-derived antioxidations were well housed in the bound zone of Keap1 via stable hydrogen bonding and hydrophobic interaction. Eventually, three of eight antioxidations were identified after ADME and physicochemical evaluations. The citrus-derived flavonoids were identified as potential dietary antioxidants of the Keap1-Nrf2 interaction, and can be used to improve oxidative stress-related chronic diseases.

Uptake, translocation and subcellular distribution of broflanilide, afidopyropen, and flupyradifurone in mustard (Brassica juncea)

Novel pesticides broflanilide (BFI), afidopyropen (ADP), and flupyradifurone (FPO) have been widely used and become the new organic pollutants. However, uptake, translocation and residual distribution of BFI, ADP, and FPO in plants remain unclear. Therefore, residues distribution, uptake, and translocation of BFI, ADP, and FPO were investigated in mustard field trials and hydroponic experiments. The field results indicated that the residues of BFI, ADP, and FPO were 0.001-1.87 mg/kg at 0-21 d and dissipated fast in mustard (half-lives=5.2-11.3 d). More than 66.5 % of FPO residues were distributed in the cell-soluble fractions because of their high hydrophilicity, while hydrophobic BFI and ADP were primarily stored in the cell walls and organelles. The hydroponic data showed that the foliar uptake rates of BFI, ADP, and FPO were weak (bioconcentration factors<1), but the root uptake rate was strong (bioconcentration factors>1). The upward and downward translations of BFI, ADP, and FPO were limited (translation factor<1). BFI and ADP are uptake by roots via apoplast pathway, and FPO is uptake via symplastic pathway. This study contributes to the understanding of the formation of pesticide residues in plants and provides a reference for safe application and risk assessment of BFI, ADP, and FPO.

Mechanisms for the structural dependent transformation of 6:2 and 8:2 polyfluoroalkyl phosphate diesters in wheat (Triticum aestivum L.)

Polyfluoroalkyl phosphate esters (PAPs) are widely used and detected in various environmental media and organisms, but little is known about their behaviors in plants. In this study, the uptake, translocation and transformation of 6:2 and 8:2 diPAP in wheat using hydroponic experiments were investigated. 6:2 diPAP was more easily taken up by roots and translocated to shoots than 8:2 diPAP. Their phase I metabolites were fluorotelomer saturated carboxylates (FTCAs), fluorotelomer unsaturated carboxylates (FTUCAs) and perfluoroalkyl carboxylic acids (PFCAs). PFCAs with even-numbered chain length were the primary phase I terminal metabolites suggesting that they were mainly generated through β-oxidation. Cysteine and sulfate conjugates were the primary phase II transformation metabolites. The higher levels and ratios of phase II metabolites in the 6:2 diPAP exposure group indicated that the phase I metabolites of 6:2 diPAP were more susceptible to phase II transformation than that of 8:2 diPAP, which was confirmed by density functional theory calculation. Enzyme activity analyses and in vitro experiments demonstrated that cytochrome P450 and alcohol dehydrogenase actively participated in the phase Ⅰ transformation of diPAPs. Gene expression analyses showed that glutathione S-transferase (GST) was involved in the phase Ⅱ transformation, and the subfamily GSTU2 played a dominant role.

Spatiotemporal Dynamics of Phthalate Esters in Tea Plants Growing Different Geographical Environments and an Attempt on Their Risk Assessment

The phthalate esters (PAEs) have become ubiquitous pollutants. In the present work, we investigated their pollution on teas. Dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DBP), and di-(2-ethyl) hexyl phthalate (DEHP) were detected in all fresh tea leaves with DBP being the major congener of PAEs in teas followed by DiBP and DEHP. Seasonal variation, spatial distribution difference, correlationship of environmental factors, and potential health risks of PAEs were analyzed. The PAEs content in one bud and two leaves was lower than that in upper mature leaves in tea plants. The PAEs content in fresh tea leaves was the lowest in spring, while it was high in autumn and winter. The correlation analysis results showed that PAEs had significantly negative correlation with ambient air temperature, while it was positively correlated with the air quality index. PAEs analysis of spring tea in Anhui and Zhejiang provinces further indicated that the factor of provincial regions had little impact on the PAEs pollution level in tea. By contrast, the different environmental areas significantly affected PAE pollution, especially the agricultural areas. The human daily intake-based (13 g/day) risk assessment indicated that both the carcinogenic and non-carcinogenic risks (1.76 × 10^-7-6.12 × 10^-7) of PAEs via tea consumption were acceptable, with the estrogen equivalence (1.60-6.29 ng E₂/kg) being at a medium level. This study provides significant information for pollution control and risk assessment of PAEs in Chinese tea production.

Phthalate esters and their metabolites in paired soil-crop systems from farmland in major provinces of eastern China: Pollution characteristics and implications for human exposure

The extensive application of phthalate esters (PAEs) as plasticizers has raised considerable concern regarding their environmental load, but the associated occurrence of PAE metabolites has often been ignored. The soil-plant system is a vital source of human exposure to PAEs via crop intake. Here, paired soil-plant samples were collected from eastern China to investigate the occurrence characteristics of seven PAE congeners and two primary monoester phthalate metabolites (mPAEs) in farmland. The detection frequencies of PAEs and mPAEs in the investigated soil-plant systems were 100 %. The total concentrations of PAEs in the collected soil and plant samples ranged from 0.07 to 1.83 mg/kg (dw) and from 3.9 to 24 mg/kg (dw), respectively. Moreover, di-(2-ethylhexyl) phthalate, diisobutyl phthalate and di-n-butyl phthalate were the predominant PAE congeners in the farmlands of eastern China, collectively accounting for >90 % of the total concentration of PAEs. In addition, the total concentrations of the two mPAEs were markedly higher in plant samples (49 ng/g dw to 549 ng/g dw) than in soil samples (3 ng/g dw to 22 ng/g dw), indicating that PAEs are readily metabolized in plants. The hazard index (HI) values of all PAEs in all crops were <1, demonstrating that the risks of PAEs in the crops were acceptable. However, the daily intake of mPAEs from the consumption of cabbage was higher than or comparable to that of some PAEs (such as di-n-octyl phthalate). This highlights the importance of taking metabolites into consideration in further environmental investigations and risk assessments of PAEs.

The content of PAEs in field soils caused by the residual film has a periodical peak

The wide use of plastic film mulch has led to the release of phthalate esters (PAEs), which seriously threatens the soil environment and the safety of crop production. However, it is unknown whether there is a maximum threshold of soil PAEs accumulation induced by plastic film residue, and the dynamic changes of soil PAEs under field conditions are still unclear. To address these issues, a field experiment was conducted to investigate the temporal fluctuations of soil PAEs content and the response of microbial community structure in the field with plastic film residue. Results showed that the content of soil PAEs fluctuated during an observation period of one year, had a periodical peak in winter and summer, and was exacerbated by the increase in the aging degree and residual amount of plastic films. The PAEs content in soil with black films was higher than the US soil allowable criteria. High-throughput sequencing analysis showed that the addition of residual film significantly increased the alpha diversity of bacterial communities, changed the structure of bacterial community, and generated significant disturbances in bacterial function. Besides, the residual film recruited more microbiota related to plastic film and PAEs degradation. Results of the present study provide insight into the dynamic variation of soil PAEs caused by plastic film residue in one year, which is important to help evaluate the pollution risk of PAEs on soils and crops caused by residual plastic film.

Occurrence, source, ecological risk, and mitigation of phthalates (PAEs) in agricultural soils and the environment: A review

The widespread distribution of phthalates (PAEs) in agricultural soils is increasing drastically; however, the environmental occurrence and potential risk of PAEs in agricultural systems remain largely unreviewed. In this study, the occurrence, sources, ecotoxicity, exposure risks, and control measures of PAEs contaminants in agricultural soils are summarized, and it is concluded that PAEs have been widely detected and persist in the soil at concentrations ranging from a few μg/kg to tens of mg/kg, with spatial and vertical variations in China. Agrochemicals and atmospheric deposition have largely contributed to the elevated contamination status of PAEs in soils. In addition, PAEs cause multi-level hazards to soil organisms (survival, oxidative damage, genetic and molecular levels, etc.) and further disrupt the normal ecological functions of soil. The health hazards of PAEs to humans are mainly generated through dietary and non-dietary pathways, and children may be at a higher risk of exposure than adults. Improving the soil microenvironment and promoting biochemical reactions and metabolic processes of PAEs are the main mechanisms for mitigating contamination. Based on these reviews, this study provides a valuable framework for determining future study objectives to reveal environmental risks and reduce the resistance control of PAEs in agricultural soils.

Adaptation of bacterial community in maize rhizosphere for enhancing dissipation of phthalic acid esters in agricultural soil

Rhizospheric degradation is a green and in situ strategy to accelerate dissipation of organic pollutants in soils. However, the mechanism on microbial degradation of phthalic acid esters (PAEs) in rhizosphere is still unclear. Here, the bacterial community and function genes in bulk and rhizospheric soils of maize (Zea mays L.) exposed to gradient concentrations of di-(2-ethylhexyl) phthalate (DEHP) were analyzed with 16 S rRNA, metagenomic sequencing and quantitative PCR (qPCR). Maize rhizosphere significantly increased the dissipation of DEHP by 4.02-11.5% in comparison with bulk soils. Bacterial community in rhizosphere exhibited more intensive response and shaped its beneficial structure and functions to DEHP stress than that in bulk soils. Both rhizospheric and pollution effects enriched more PAE-degrading bacteria (e.g., Bacillus and Rhizobium) and function genes in rhizosphere than in bulk soil, which played important roles in degradation of PAEs in rhizosphere. The PAE-degrading bacteria (including genera Sphingomonas, Sphingopyxis and Lysobacter) identified as keystone species participated in DEHP biodegradation. Identification of PAE intermediates and metagenomic reconstruction of PAE degradation pathways demonstrated that PAE-degrading bacteria degraded PAEs through cooperation with PAE-degrading and non-PAE-degrading bacteria. This study provides a comprehensive knowledge for the microbial mechanism on the superior dissipation of PAEs in rhizosphere.

Leaching of phthalate acid esters from plastic mulch films and their degradation in response to UV irradiation and contrasting soil conditions

Phthalate acid esters (PAEs) are commonly used plastic additives, not chemically bound to the plastic that migrate into surrounding environments, posing a threat to environmental and human health. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) are two common PAEs found in agricultural soils, where degradation is attributed to microbial decomposition. Yet the impact of the plastic matrix on PAE degradation rates is poorly understood. Using ¹⁴C-labelled DBP and DEHP we show that migration from the plastic matrix into soil represents a key rate limiting step in their bioavailability and subsequent degradation. Incorporating PAEs into plastic film decreased their degradation in soil, DBP (DEHP) from 79% to 21% (9% to <1%), over four months when compared to direct application of PAEs. Mimicking surface soil conditions, we demonstrated that exposure to ultraviolet radiation accelerated PAE mineralisation twofold. Turnover of PAE was promoted by the addition of biosolids, while the presence of plants and other organic residues failed to promote degradation. We conclude that PAEs persist in soil for longer than previously thought due to physical trapping within the plastic matrix, suggesting PAEs released from plastics over very long time periods lead to increasing levels of contamination.

Morpho-biochemical Responses and Disturbed Redox Homeostasis in Barley Under Benzyl-butyl Phthalate Stress

The present study is aimed to address the morphometric consequences, yield attributes, and biochemical responses of barley plants under the stress of an endocrine disruptor i.e., benzyl-butyl phthalate (BBP). The morphometric analyses (plant length, dry weight, and net primary productivity) revealed that the inhibition induced by BBP was concentration- and time-dependent. The seed weight and the number of seeds per spike have also significantly declined with an increase in BBP doses. Similarly, BBP exhibited significant alterations over the control in the biochemical indices viz., pigments, sugars, proteins, proline, malonaldehyde, and hydrogen peroxide contents of barley plants. Furthermore, BBP stress negatively influenced the activities of antioxidative enzymes viz., SOD, POD, CAT, APX, and GR of barley with an increase in doses and exposure durations due to the over-produced reactive oxygen species. The uptake and transport of BBP were determined and observed as a responsible cue for these toxicological implications in barley plants under BBP exposure. The correlation of barley plants' morpho-biochemical responses with BBP uptake and transport was also established using Pearson's correlation. Thus, this study indicated the toxicological behavior of meagerly explored phthalate (i.e., BBP) in the crop plant and these observations can be utilized for the generation of tolerant cultivars.

Insights into the accumulation, distribution and toxicity of pyrene associated with microplastics in rice (Oryza sativa L.) seedlings

Microplastic and polycyclic aromatic hydrocarbons (PAHs) can be introduced into agroecosystems through various agricultural activities and may threaten food safety and human health. However, little research has focused on the behavior of microplastics-associated PAHs and their toxicity effects in agroecosystems, especially in crops. In the present study, we investigated the accumulation, distribution and toxicity of pyrene associated with polyethylene (PE) microplastics in rice (Oryza sativa L.). With quantitative analysis using 14C isotope labelling, the total accumulation efficiency of 14C-pyrene in rice seedlings was 22.4 ± 1.2% and 14.5 ± 0.3% when exposed to freely dissolved pyrene and PE-associated pyrene, respectively. The translocation of 14C-pyrene was significantly decreased by microplastics adsorption even when the amount of pyrene in the rice roots had no significant difference. Subcellular distribution of 14C-pyrene in rice suggested that PE microplastics-associated pyrene located more on cell walls than free dissolved pyrene. Furthermore, results showed free pyrene, but not PE-associated pyrene, significantly decreased the length and biomass of rice roots as well as increased the activities of antioxidant enzymes (superoxide dismutase and catalase). It indicated that the association with microplastics alleviated the phytotoxicity of pyrene in rice seedlings. These findings shed new light on the environmental behavior and effects of PAHs associated with microplastics in crops and will be helpful to its comprehensive risks assessment.

Major biotransformation of phthalic acid esters in Eisenia fetida: Mechanistic insights and association with catalytic enzymes and intestinal symbionts

Phthalic acid esters (PAEs) are an important group of organic pollutants that are widely used as plasticizers in the environment. The PAEs in soil organisms are likely to be biotransformed into a variety of metabolites, and the combined toxicity of PAEs and their metabolites might be more serious than PAEs alone. However, there are only a few studies on PAE biotransformation by terrestrial animals, e.g. earthworms. Herein, the key biotransformation pathways of PAEs and their association with catalytic enzymes and intestinal symbionts in earthworms were studied using in vivo and in vitro incubation approaches. The widely distributed PAE in soil, dibutyl phthalate (DBP), was proven to be biotransformed rapidly together with apparent bioaccumulation in earthworms. The biotransformation of PAE congeners with medium or long side chains appeared to be faster compared with those with short side chains. DBP was biotransformed into butyl methyl phthalate (BMP), monobutyl phthalate (MBP), and phthalic acid (PA) through esterolysis and transesterification. Besides, the generation of small quantities of low-molecular weight metabolites via β-oxidation, decarboxylation or ring-cleavage, was also observed, especially when the appropriate proportion of NADPH coenzyme was applied to transfer electrons for oxidases. Interestingly, the esterolysis of PAEs was mainly regulated by the cytoplasmic carboxylesterase (CarE) in earthworms, with a Michaelis constant (K_m) of 0.416 mM in the catalysis of DBP. The stronger esterolysis in non-intestinal tissues indicated that the CarE was primarily secreted by non-intestinal tissues of earthworms. Additionally, the intestinal symbiotic bacteria of earthworms could respond to PAE stress, leading to the changes in their diversity and composition. The enrichment of some genera e.g. Bacillus and Paracoccus, and the enhancement of metabolism function, e.g. amino acids, energy, lipids biosynthesis and oxidase secretion, indicated their important role in the degradation of PAEs.

Composting and green technologies for remediation of phthalate (PAE)-contaminated soil: Current status and future perspectives

Phthalate esters (PAEs) are hazardous organic compounds that are widely added to plastics to enhance their flexibility, temperature, and acidic tolerance. The increase in global consumption and the corresponding environmental pollution of PAEs has caused broad public concerns. As most PAEs accumulate in soil due to their high hydrophobicity, composting is a robust remediation technology for PAE-contaminated soil (efficiency 25%-100%), where microbial activity plays an important role. This review summarized the roles of the microbial community, biodegradation pathways, and specific enzymes involved in the PAE degradation. Also, other green technologies, including biochar adsorption, bioaugmentation, and phytoremediation, for PAE degradation were also presented, compared, and discussed. Composting combined with these technologies significantly enhanced removal efficiency; yet, the properties and roles of each bacterial strain in the degradation, upscaling, and economic feasibility should be clarified in future research.

Root Uptake Pathways and Cell Wall Accumulation Mechanisms of Organophosphate Esters in Wheat (Triticum aestivum L.)

The behavior of organophosphate esters (OPEs) in plants has drawn considerable attention because of their adverse effects to biota. However, the root uptake pathways and cell wall accumulation mechanisms of OPEs in plants are still unclear. In this study, the uptake pathways, subcellular distribution, and accumulation mechanisms of OPEs in wheat roots were elucidated. The results demonstrated that the symplast is the major pathway for uptake of both tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPHP) in wheat roots. Inhibitor experiments showed that the transmembrane transport of OPEs is a passive uptake process, and aquaporins and carrier proteins contribute to the uptake of OPEs. More than 69% of TCEP was accumulated in cell sap due to its high hydrophilicity, while the hydrophobic TPHP was mainly stored in the root cell wall. The sorption affinity of TPHP decreased gradually following the sequential fractionation of wheat roots, which confirmed the significant contribution to TPHP sorption on wheat roots. A significant positive correlation between the sorption affinity values and the percentage of aromatic carbon was observed (r² = 0.856, p < 0.01), indicating that the accumulation of hydrophobic OPEs in roots does not just depend on lipids alone, but the aromatic moieties of lignin in the cell wall also contribute to OPE accumulation.

The mechanism of uptake and translocation of antibiotics by pak choi (Brassica rapa subsp. chinensis)

Antibiotic uptake by vegetables from the environment is one pathway in which humans are exposed to antibiotics through the food chain and can pose potential risks to human health. Therefore, understanding the mechanism of how antibiotics enter vegetables will contribute to developing effective measures to reduce antibiotic contamination in crops. In this study, a series of hydroponic experiments were conducted to investigate the uptake and translocation of six antibiotics in pak choi. The results showed the accumulation capacity of fluoroquinolones was significantly higher than that of tetracycline and sulfamethoxypyridazine. The antibiotic uptake kinetics in roots were well described by the Michaelis-Menten equation. The results for the metabolic inhibitor, aquaporin inhibitor, and transpiration inhibitor showed that the uptake processes for ofloxacin, norfloxacin, and enrofloxacin were energy-dependent, those for sulfamethoxypyridazine and ciprofloxacin were aquaporin-dependent, and that for tetracycline was energy- and aquaporin-dependent. Antibiotic translocation was associated with water transport through xylem vessels, which could be controlled by aquaporin activities and transpiration. Roots were the main accumulator of antibiotics, and the degradation percentages of tetracycline, norfloxacin, enrofloxacin, and ofloxacin by Pak choi were 0-14.48% within 72 h. Overall, our findings provide a better understanding of the transfer of antibiotics from the environment to vegetables, which will be of great significance for developing optimal management practices to mitigate antibiotic contamination in vegetables and ensuring food safety.