Comprehensive study of chiral herbicide flusulfinam uptake, translocation, degradation, and subcellular distribution in rice (Oryza sativa L.).

The biological behavior of flusulfinam, a potential commercial chiral herbicide for rice, has not been well explored. Herein, the uptake of chiral flusulfinam by rice and its transport, degradation, and subcellular distribution in rice (Oryza sativa L.) were investigated. The enantiomeric fraction (EF) in roots was 0.54 during 0 d to 7 d in hydroponic laboratory conditions. The bioconcentration factor of flusulfinam enantiomers was 2.1, suggesting an absence of observed enantioselectivity in the absorption process. Notably, the EF in the shoots decreased to 0.35 on the 7th day. The translocation factors of R- and S-flusulfinam were 0.12 and 0.27, respectively, indicating a preferential transfer of the S-flusulfinam from the root to the shoot. Flusulfinam was identified in the root after spraying. The translocation factors of R- and S-flusulfinam were consistently similar, signifying the capacity for downward movement without enantioselectivity. Interestingly, the degradation half-lives of R- and S-flusulfinam in the total plant were 5.50 and 5.06 d (p < 0.05), respectively, supporting the preferential degradation of S-flusulfinam throughout the total plant. Flusulfinam primarily entered the roots via the apoplastic pathway and was subsequently transported within the plant through aquaporins and ion channels. The subcellular distribution experiment revealed the predominant accumulation of flusulfinam enantiomers in soluble components (84%) with no enantioselectivity in these processes. There was upregulation lipid transfer protein-2 and carboxylesterases15 genes, which could explain the preferential transport and degradation of S-flusulfinam. This study is important in assessing the environmental risk associated with flusulfinam and ensuring food safety.

Transcriptomic and physiological analyses unravel the effect and mechanism of halosulfuron-methyl on the symbiosis between rhizobium and soybean.

Halosulfuron-methyl (HSM) is a new and highly effective sulfonylurea herbicide widely used in weed control, but its residue in the environment poses a potential risk to soybean. Soybean-rhizobium symbiotic nitrogen fixation is crucial for sustainable agricultural development and ecological environment health. However, the impact of HSM on the symbiosis between soybean and rhizobium is unclear. In this study, the effects of HSM on the soybean-rhizobium symbiotic process and nitrogen fixation were investigated by means of transcriptomic and physiological analyses. Treatment with a concentration of HSM less than 0.5 mg L-1 had no effect on rhizobium growth, but significantly reduced nodules number, the biomass of soybean nodules, and nitrogenase activity in root nodules (P < 0.05). Transcriptomic analysis showed that differentially expressed genes (DEGs) involved in NH4+ assimilation were significantly downregulated (P < 0.05). In addition, the activities of NH4+ assimilation enzymes were markedly reduced. This result was further confirmed by the accumulation of NH4+ in root nodules, indicating that the inhibition of nitrogen fixation by HSM may be caused by excessive NH4+ accumulation in root nodules. Furthermore, DEGs involved in flavonoid synthesis, phytohormone biosynthesis, and phytohormone signaling transduction were significantly downregulated (P < 0.05), which was consistent with the decrease in flavonoid and phytohormone contents determined in this study. These results suggested that HSM may inhibit soybean nodulation by inhibiting flavonoid synthesis in soybean roots, disrupting the balance of plant endogenous hormones in roots during symbiosis, and blocking the transmission of hormone signals during the symbiosis. Our findings provide new insights into the effects of HSM on the legume-rhizobium nodule symbiotic process.

Simultaneous analysis of indaziflam and its metabolites in pitaya using dispersive solid phase extraction coupled with liquid chromatography coupled with tandem mass spectrometry.

A simple and efficient multiresidue method using dispersive solid phase extraction and liquid chromatography coupled with tandem mass spectrometry was developed for the targeted analysis of indaziflam and its five metabolites (indaziflam-diaminotriazine, indaziflam-carboxylic acid, indaziflam-triazine indanone, indaziflam-hydroxyethyl, and indaziflam-olefin) in pitaya samples (including roots, plants, flowers, peels, pulp, and whole fruit). The analytes were extracted with acetonitrile, and the extracts were purified using multiwalled carbon nanotubes. The method was validated using pitaya samples spiked at 0.5, 5, and 50 µg/kg, and the average recoveries varied from 61.1 to 103.7% with relative standard deviations lower than 12.7% (n = 5). This method exhibited sufficient linearity within the concentration range of 0.1-100 µg/L. The limits of detection and quantification were in the ranges of 0.001-0.1 and 0.003-0.3 µg/kg, respectively. The method was successfully applied to analyze pitaya samples in Nanning, and no indaziflam or its metabolites were detected in the samples analyzed.

Enhanced disappearance of mesotrione and fomesafen by water hyacinth (Eichhornia crassipes) in water.

This study aimed to investigate the potential use of water hyacinth (Eichhornia crassipes) in removing two herbicides (mesotrione and fomesafen) with long degradation cycles in water. The relative growth rate (RGR) of water hyacinth in the presence of 100-mg/L mesotrione and fomesafen was significantly lower than that in their absence, particularly with fomesafen. Moreover, the RGRFW and RGRDW with treatment with fomesafen were 1.47- and 1.58-fold lower than those with treatment with mesotrione, respectively. The disappearance rate constants of mesotrione and fomesafen in natural water were, respectively, 0.1148 and 0.0276 d-1 with plants and 0.0038 and 0.0005 d-1 without plants. The disappearance rate constants with and without plants were significantly different, indicating that uptake by plants combined with degradation by plant-associated bacteria account for 96.7% and 98.2% of the removal of mesotrione and fomesafen, respectively. The bioconcentration factor for mesotrione and fomesafen in living water hyacinth plants ranged 0.38-16.97 and 1.05-3.50 L/kg, respectively, whereas the residues of mesotrione and fomesafen in water decreased by 70-92 and 22-34%, respectively, after the plants were grown for 14 d in culture solution with 100-mg/L mesotrione and fomesafen. These results show that uptake by plants combined with degradation by plant-associated bacteria may be the dominant process in the removal of mesotrione and fomesafen from water by plants. Water hyacinth may be applied as an efficient, economical, and ecological alternative to accelerate the removal and degradation of agro-industrial waste water polluted with mesotrione and fomesafen.

Determinations of dinotefuran and metabolite levels before and after household coffee processing in coffee beans using solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry.

BACKGROUND: Coffee is one of the most popular beverages in the world. However, as daily consumables, coffee beans may contain pesticide residues that are capable of causing adverse health effects. Thus, we investigated residue dynamics in coffee beans using supervised field trials under Good Agricultural Practice conditions and determined the effects of household coffee processing on the coffee-bean pesticide residues dinotefuran and its metabolites 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) and 1-methyl-3-(tetrahydro-3-furylmethyl) guanidine (DN). RESULTS: The recovery rate of dinotefuran and its metabolites UF and DN was in the range 73.5%-106.3%, with a relative SD < 10%. The limits of detection and limits of quantification for dinotefuran, UF and DN were all 0.003 and 0.01 mg kg-1 , respectively. Dissipation experiments were conducted over 2015 and 2016 and showed a mean half-life of 40.8 days. Coffee processing procedures were performed as described for traditional household coffee processing in Ethiopia. Dinotefuran contents were reduced by 44.4%-86.7% with washing of coffee beans and the roasting process reduced these contents by 62.2%-100%. DN residues were not detected in roasted coffee beans before day 21 or in brewed coffee before day 35 and UF residues were not detected in brewed coffee before day 35. Kruskal-Wallis analyses indicated large variations in the stability of pesticide residues between processing methods (P ≤ 0.05). Reductions of pesticide concentrations with washing were also significantly lower than those following roasting (P = 0.0001) and brewing processes (P = 0.002). Moreover, processing factors were less than one for all processing stages, indicating reductions of pesticides contents for all processing stages. CONCLUSION: The cumulative effects of the three processing methods are of paramount importance with respect to an evaluation of the risks associated with the ingestion of pesticide residues, particularly those in coffee beans. © 2018 Society of Chemical Industry.

Determination of propineb and its metabolites propylenethiourea and propylenediamine in banana and soil using gas chromatography with flame photometric detection and LC-MS/MS analysis.

A sensitive and specific method for the determination of propineb and its metabolites, propylenethiourea (PTU) and propylenediamine (PDA), using gas chromatography with flame photometric detection (GC-FPD) and LC-MS/MS was developed and validated. Propineb and its metabolite residue dynamics in supervised field trials under Good Agricultural Practice (GAP) conditions in banana and soil were studied. Recovery of propineb (as CS2), PDA and PTU ranged from 75.3 to 115.4% with RSD (n = 5) of 1.3-11.1%. The limit of quantification (LOQ) of CS2, PDA and PTU ranged from 0.005 to 0.01 mg kg-1, and the limit of detection (LOD) ranged from 0.0015 to 0.0033 mg kg-1. Dissipation experiments showed that the half-life of propineb in banana and soil ranged from 4.4 to 13.3 days. PTU was found in banana with a half-life of 31.5-69.3 days, while levels of PDA were less than 0.01 mg kg-1 in banana and soil. It has been suggested that PTU is the major metabolite of propineb in banana. The method was demonstrated to be reliable and sensitive for the routine monitoring of propineb and its metabolites in banana and soil. It also serves as a reference for the detection and monitoring of dithiocarbamates (DTCs) residues and the evaluation of their metabolic pathway.

Interactions between salicylic acid and antioxidant enzymes tilting the balance of H2O2 from photorespiration in non-target crops under halosulfuron-methyl stress.

Halosulfuron-methyl (HSM) is a safe, selective and effective sulfonylurea herbicide (SU) for the control of sedge and broadleaf weeds in sugarcane, corn, tomato, and other crops. The primary site of action is acetolactate synthase (ALS), a key enzyme of branched chain amino acids (BCAAs) synthesis. In addition to ALS inhibition, BCAAs deficiencies and oxidative damage may be involved in toxic effects of SUs. However, secondary targets of HSM relevant to plant physiological responses are unclear. In the present study, comparative growth inhibition and peroxidization injury between sensitive and tolerance crops were observed at biochemical and physiological levels suggesting involvement of H2O2, ethylene, salicylic acid (SA) in the oxidative stress responses to HSM. HSM caused accumulation of H2O2, stimulated photorespiration and consequent accumulation of SA that worsened the peroxidization injury to the sensitive C3 plant soybean (Glycine max). The growth inhibition at low concentrations of HSM could be lessened by supplementary BCAAs, reactive oxygen species scavengers or ethylene inducers, whereas the oxidation damage at high concentrations of HSM could not be reversed and ultimately lead to plant death. H2O2 at a low level stimulated the antioxidase system including glutathione S-transferase activities in the HSM-tolerant C4 maize (Zea mays), which contributes to HSM tolerance. H2O2 plays an important role on HSM stress responses in both HSM-sensitive and HSM-tolerant soybean and maize.

Enantioselective Phytotoxicity of Imazamox Against Maize Seedlings.

There is increasing concern about the enantioselective effects of chiral herbicides. To study the enantioselective toxicity of the chiral herbicide imazamox on maize, maize seedlings (Zhengda 619, Zea mays L.) were exposed to imazamox racemate and enantiomers in hydroponic experiments. The results showed that imazamox enantiomers selectively affected maize. The effective concentration of Rac-, S- and R-imazamox that caused 50 % inhibition after 5 days treatments (EC50,5d) were 0.4212, 1.2142 and 0.2460 mg L(-1), respectively, for maize root length; 0.0002, 0.1005, 0.0032 mg L(-1), respectively, for maize root fresh weight; 0.7114, 1.4056 and 0.4530 mg L(-1), respectively, for maize shoot height; 0.6220, 1.5418, 0.2286 mg L(-1), respectively, for maize shoot fresh weight; and 0.1100, 0.3306, 0.0307 mg L(-1), respectively, for the total chlorophyll content of leaves. The root morphological parameters and root activity reflected the toxicity effects in the order R-imazamox > Rac-imazamox > S-imazamox. Maize roots were more sensitive to imazamox than maize shoots. The chiral herbicide imazamox poses enantioselective phytotoxicity on maize seedlings: the order of toxicity is R-imazamox > Rac-imazamox > S-imazamox.

PhoB-regulated phosphate assimilation of Ralstonia solanacearum is cross-activated by VsrB in Pi-abundant rich medium.

Ralstonia solanacearum is a devastating phytopathogen infecting a broad range of economically important crops. Phosphate (Pi) homeostasis and assimilation play a critical role in the environmental adaptation and pathogenicity of many bacteria. However, the Pi assimilation regulatory mechanism of R. solanacearum remains unknown. This study revealed that R. solanacearum pstSCAB-phoU-phoBR operon expression is sensitive to extracellular Pi concentration, with higher expression under Pi-limiting conditions. The PhoB-PhoR fine-tunes the Pi-responsive expression of the Pho regulon genes, demonstrating its pivotal role in Pi assimilation. By contrast, neither PhoB, PhoR, PhoU, nor PstS was found to be essential for virulence on tomato plants. Surprisingly, the PhoB regulon is activated in a Pi-abundant rich medium. Results showed that histidine kinase VsrB, which is known for the exopolysaccharide production regulation, partially mediates PhoB activation in the Pi-abundant rich medium. The 271 histidine of VsrB is vital for this activation. This cross-activation mechanism between the VsrB and PhoB-PhoR systems suggests the carbohydrate-Pi metabolism coordination in R. solanacearum. Overall, this research provides new insights into the complex regulatory interplay between Pi metabolism and growth in R. solanacearum.

Molecular Mechanism of GmSNE3 Ubiquitin Ligase-Mediated Inhibition of Soybean Nodulation by Halosulfuron Methyl.

In this study, the role of E3 ubiquitin ligase GmSNE3 in halosulfuron methyl (HSM) inhibiting soybean nodulation was investigated. GmSNE3 was strongly induced by HSM stress, and the overexpression of GmSNE3 significantly reduced the number of soybean nodules. Further investigation found that GmSNE3 could interact with a nodulation signaling pathway 1 protein (GmNSP1a) and GmSNE3 could mediate the degradation of GmNSP1a. Importantly, GmSNE3-mediated degradation of GmNSP1a could be promoted by HSM stress. Moreover, HSM stress and the overexpression of GmSNE3 resulted in a substantial decrease in the expression of the downstream target genes of GmNSP1a. These results revealed that HSM promotes the ubiquitin-mediated degradation of GmNSP1a by inducing GmSNE3, thereby inhibiting the regulatory effect of GmNSP1a on its downstream target genes and ultimately leading to a reduction in nodulation. Our findings will promote a better understanding of the toxic mechanism of herbicides on the symbiotic nodulation between legumes and rhizobia.

Developmental toxicity and metabolomics analyses of zebrafish (Danio rerio) embryos exposed to Fenoxaprop-p-ethyl.

Fenoxaprop-p-ethyl (FEN) is an aryloxy phenoxy propionate herbicide that has been widely used in paddy fields. Previous studies have indicated that FEN is highly toxic to aquatic organisms, but little is known about the developmental effects of FEN. This study investigated acute and developmental toxicity, malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activities, and metabolomic analyses in zebrafish embryos after 96 h of exposure. FEN exhibited high acute toxicity to zebrafish embryos and larvae. Exposure to FEN could reduce heartbeat and hatching rates and increase malformation rates in embryos. Oxidative damage was also caused in embryos. The results of metabolomics analysis showed that 102 differentially abundant metabolites were found in zebrafish embryos in the 0.05 mg/L FEN treatment group, and 60 differentially abundant metabolites were found in the 0.20 mg/L FEN treatment group. These differentially abundant metabolites mainly belonged to 9 metabolic pathways, of which folate pathways and ABC transport protein pathways had the greatest impact. These results suggested that FEN induced high acute and developmental toxicity in zebrafish embryos.

Novel herbicide flusulfinam: absolute configuration, enantioseparation, enantioselective bioactivity, toxicity and degradation in paddy soils.

BACKGROUND: Flusulfinam, a novel chiral herbicide, effectively controls Echinochloa crusgalli and Digitaria sanguinalis in paddy fields, indicating significant potential for practical agricultural applications. However, limited information is available on flusulfinam from a chiral perspective. A comprehensive evaluation of the enantiomeric levels of flusulfinam was performed. RESULTS: Two enantiomers, R-(+)- and S-(-)-flusulfinam, were separately eluted using a Chiralcel OX-RH column. The bioactivity of R-flusulfinam against the two was 1.4-3.1 fold that of Rac-flusulfinam against two weed species. R-flusulfinam toxicity to Danio rerio larvae and Selenastrum capricornutumwere was 0.8- and 3.0-fold higher than Rac-flusulfinam, respectively. Degradation experiments were conducted using soil samples from four Chinese provinces. The findings indicated that S-flusulfinam (half-life T1/2 = 40.8 days) exhibits preferential degradation than R-flusulfinam (T1/2 = 46.2-57.8 days) in the soils of three provinces. Under anaerobic conditions, soil from Anhui exhibited preferential degradation of R-flusulfinam (T1/2 = 46.2 days) over S-flusulfinam (T1/2 = 63 days). Furthermore, two hydrolysis products of flusulfinam (M299 and M100) are proposed for the first time. CONCLUSION: The enantioselective bioactivity, toxicity and degradation of flusulfinam were investigated. Our findings indicate that R-flusulfinam is an extremely effective and low-toxicity enantiomer for the tested species. The soil degradation test indicated that the degradation of flusulfinam was accelerated by higher organic matter content and lower soil pH. Furthermore, microbial communities may play a crucial role in driving the enantioselective degradation processes. This study lays the groundwork for the systematic evaluation of flusulfinam from an enantiomeric perspective. © 2024 Society of Chemical Industry.

Insight into the effect of microplastics on the adsorption and degradation behavior of thiamethoxam in agricultural soils.

Thiamethoxam and microplastics are both common pollutants in farmland soil; however, few studies have focused on the interaction between thiamethoxam and microplastics in soil. Here, a batch experiment and soil incubation experiment were performed to explore the mechanism and effects of microplastics on the adsorption and degradation behaviors of thiamethoxam in soil, respectively. First, the batch experimental results indicated that the adsorption process of thiamethoxam on the microplastic/soil mixtures and soil-only systems mainly relies on chemical interactions. All sorption processes had moderate intensities of adsorption, and the sorption process occurred on the heterogeneous surface. In addition, the particle size and dose of microplastics could both affect the adsorption behavior of thiamethoxam onto microplastics/soil systems. The sorption capacity of thiamethoxam in soil decreases as the particle size of microplastics increases, but the sorption capacity increases as the dose of microplastics increases. Second, the results of the soil incubation experiment showed that the half-lives of thiamethoxam ranged from 57.7 d to 86.6 d, from 86.6 d to 173.3 d, and 115 d in the biodegradable microplastic/soil systems, nondegradable microplastic/soil systems, soil-only systems, respectively. These results indicate that biodegradable microplastics promoted the degradation of thiamethoxam, while nondegradable microplastics delayed the degradation process of thiamethoxam in soil. Overall, microplastics could change the degradation behaviors, sorption capacity and adsorption efficiency, and then affect the mobility and persistence of thiamethoxam in the soil environment. These findings contribute to understanding the influence of microplastics on the environmental fate of pesticides in the soil environment.

Characterization and novel pathway of atrazine catabolism by Agrobacterium rhizogenes AT13 and its potential for environmental bioremediation.

Agrobacterium rhizogenes AT13, a novel bacterial strain that was isolated from contaminated soil, could utilize atrazine as the sole nitrogen, thereby degrading it. Optimization of the degradation reaction using a Box-Behnken design resulted in 99.94% atrazine degradation at pH 8.57, with an inoculum size of 3.10 × 109 CFU/mL and a concentration of 50 mg/L atrazine. Ultra-high performance liquid chromatography-electrospray ionization-high resolution mass spectrometry (UPLC-ESI-HRMS), liquid chromatography tandem mass spectrometry (LC-MS/MS) and high performance liquid chromatography (HPLC) analyses identified and quantified six reported metabolites and a novel metabolite (2-hydroxypropazine) from atrazine degradation by AT13. On the basis of these metabolites, we propose an atrazine degradation pathway that includes dichlorination, hydroxylation, deamination, dealkylation and methylation reactions. The toxicity of the degradation products was evaluated by Toxicity Estimation Software Tool (T.E.S.T). Bioaugmentation of atrazine-polluted soils/water with strain AT13 significantly improved the atrazine removal rate. Thus, AT13 has potential applications in bioremediation.

Biodegradation characteristics and mechanism of terbuthylazine by the newly isolated Agrobacterium rhizogenes strain AT13.

Terbuthylazine (TBA) is an emerging environmental contaminant that poses moderate to high risk to non-target organisms. In this study, a newly TBA-degrading strain, Agrobacterium rhizogenes AT13, was isolated. This bacterium degraded 98.7% of TBA (100 mg/L) within 39 h. Based on the six detected metabolites, three novel pathways of strain AT13, including dealkylation, deamination-hydroxylation, and ring-opening reactions, were proposed. The risk assessment demonstrated that most degradation products might be substantially less harmful than TBA. Whole-genome sequencing and RT-qPCR analysis revealed that ttzA, which encodes S-adenosylhomocysteine deaminase (TtzA), is closely related to TBA degradation in AT13. Recombinant TtzA showed 75.3% degradation of 50 mg/L of TBA within 13 h and presented a Km value of 0.299 mmol/L and a Vmax value of 0.041 mmol/L/min. The molecular docking results indicated that the binding energy of TtzA to TBA was -32.9 kcal/mol and TtzA residue ASP161 formed two hydrogen bonds with TBA at distances of 2.23 and 1.80 Å. Moreover, AT13 efficiently degraded TBA in water and soil. Overall, this study provides a foundation for the characterization and mechanism of TBA biodegradation and may enhance our understanding of the TBA biodegradation by microbes.

Analytical method for sequential determination of persistent herbicides and their metabolites in fish tissues by UPLC-MS/MS.

A novel and accurate liquid chromatography-tandem mass spectrometry method was developed to sequentially determine three persistent herbicides (atrazine (ATZ), acetochlor (ACE), and metolachlor (MET)) and seven characteristic metabolites (desethylatrazine (DEA), deisopropylatrazine (DIA), diaminochlorotriazine (DACT), MET-oxanilic acid (MET-OA), MET-ethanesulfonic acid (MET-ESA), ACE-ESA, and ACE-OA) in fresh fish tissues from six fish species. A modified QuEChERS method was conducted to extract the target compounds from fish tissues. Matrix-matched calibrations of the target analytes were carried out at spiking levels of 1, 10, 100, and 1000 ng g-1. The method was validated in accordance with Codex guidelines (CAC/GL 71-2009). Recoveries for the target analytes were 67-120% with relative standard deviations below 20%, and the matrix effects ranged from -58.7% to 59.3%. The limits of detection and quantitation were 0.01-1.90 and 0.02-6.35 ng g-1, respectively. Moreover, the method was successfully applied to analyze the concentrations of the target chemicals in fresh tissue samples of six fish species (n = 67) collected from four markets in Nanning City, Guangxi Province, China. The concentrations in all samples were 1.1-140.5 ng g-1. Interestingly, this study was the first to measure DEA and DIA in fish liver, and their highest concentrations were 10.7 and 14.2 ng g-1, respectively. This method provides a basis for studying the pathways of biotransformation, bioaccumulation, detoxification, and exposure patterns of ACE, ATZ, MET, and their metabolites in aquatic environments.

Metabolomic and transcriptomic investigation of the mechanism involved in enantioselective toxicity of imazamox in Lemna minor.

Imazamox (IM) is a chiral pesticide that has been widely used in agriculture. Currently, few studies have investigated the toxicity mechanisms of imazamox to aquatic macrophyte from the enantiomer level. In this study, the enantioselective effects of IM on the toxicity and physiological and biochemical system of aquatic macrophyte Lemna minor were systematically investigated. Metabolomic and transcriptomic for Lemna minor were used to identify potential mechanisms of toxicity. 7 d EC50s for racemic-, R-, and S-IM were 0.036, 0.035, and 0.203 mg/L, respectively, showing enantioselective toxicity. In addition, IM caused Lemna minor lipid peroxidation and antioxidant damage, and inhibited the activities of the target enzymes. Metabolomic and transcriptomic data indicated that R-IM interferenced differentially expressed genes and metabolites of Lemna minor which were enriched in carbon fixation during photosynthesis, glutathione metabolic pathway, pentose phosphate pathway, zeatin biosynthesis, and porphyrin and chlorophyll metabolism. S-IM affected phenylalanine metabolism, phenylpropanoid biosynthesis, zeatin biosynthesis and secondary metabolite biosynthesis. Racemic-IM influenced carbon fixation during operation, glutathione metabolic pathway, zeatin biosynthesis and pentose phosphate pathway. The results provide new insights into the enantioselective toxicity mechanisms of IM to Lemna minor, and lay the foundation for conducting environmental risk assessments.

Adipokinetic hormone signaling regulates cytochrome P450-mediated chlorantraniliprole sensitivity in Spodoptera frugiperda (Lepidoptera: Noctuidae).

BACKGROUND: Fall armyworm (FAW, Spodoptera frugiperda) is one of the most destructive and invasive pests worldwide and causes significant economic losses. Intensive and frequent use of insecticides has led to the development of resistance in FAW. Adipokinetic hormone (AKH) have been proven to be involved in insecticide resistance in insects. However, the molecular mechanism underlying chlorantraniliprole resistance mediated by AKH signaling in FAW remains unclear. RESULTS: The expression of SpfAKHR was highest in male adults and lowest in 1st instar larvae. SpfAKH was expressed the highest in eggs and the lowest in 6th instar larvae. AKH signaling was involved in the sensitivity of FAW to chlorantraniliprole through a toxicological bioassay, and the combination of chlorantraniliprole and bithionol (an inhibitor of key enzymes in the AKH pathway) significantly increased the mortality of FAW. Chlorantraniliprole significantly induced the expression of ten P450s, SpfAKH and SpfAKHR in FAW. RNA interference against SpfAKHR significantly decreased the P450 content, downregulated the expression of three P450 genes (SpfCYP6B50, SpfCYP321A9 and SpfCYP9A58) and inhibited the resistance of FAW to chlorantraniliprole. The topical application of AKH peptide significantly increased the P450 content, upregulated the expression of five P450 genes (SpfCYP321A9, SpfCY321A8, SpfCYP321A10, SpfCYP321A7 and SpfCYP6AB12), and enhanced the survival of FAW against chlorantraniliprole. CONCLUSIONS: AKH plays an important role in enhancing chlorantraniliprole resistance in FAW by exerting a positive influence on P450 gene expression and P450 content. These results provide valuable insights into insecticide resistance regulation and FAW control strategies. © 2022 Society of Chemical Industry.

The effect of microplastics on behaviors of chiral imidazolinone herbicides in the aquatic environment: Residue, degradation and distribution.

The pollution of aquatic environments by microplastics and herbicides has become a global concern. This study was focused on imazamox, imazapic, and imazethapyr sorption to polypropylene microplastics in water. And the potential effects of microplastics on herbicide enantiomer degradation and distributions in water, sediment, and water-sediment microcosms were investigated. Adsorption experiment results indicated that herbicide sorption to microplastics involved both chemisorption and physical adsorption. Degradation experiment results indicated that microplastics could markedly increase herbicide persistence in water and sediment. Marked stereoselective degradation was not found for the three herbicides in water and sediment, but stereoselective degradation of imazapic in water containing microplastics was found. The water-sediment microcosms experiment results indicated that microplastics have significant effect on stereoselectivity degradation and distribution in water and water-sediment microcosms for imazapic, and have little effect on stereoselectivity behaviors of imazamox and imazethapyr in water-sediment systems. Furthermore, the microcosm experiment results also indicated that herbicides can partition between water and microplastics and that microplastics could affect herbicide persistence and distributions in aquatic environments. The present study provides new insights into the fate of chiral pollutants in aquatic environments containing microplastics, and contributes to understanding behaviors of herbicides and microplastics in aquatic environments.

Insight into the adsorption mechanisms of ionizable imidazolinone herbicides in sediments: Kinetics, adsorption model, and influencing factors.

To reveal the adsorption mechanisms of imazamox, imazapic, and imazethapyr on sediment and batch experiments were carried out in this study. The adsorption kinetics of three imidazolinone herbicides on sediment were accurately described by the pseudo-second-order kinetic model(R2 > 0.9004). The values of adsorption capacity (Qe.cal) were ranged from 0.0183 to 0.0859 mg kg-1 for three herbicides. Adsorption equilibrium was reached within 24 h for three herbicides on sediment, and well fitted by the Freundlich model(R2 > 0.9561). The KF of values for adsorption obtained sediment samples were ranged from 0.2501 to 1.322 L1/n mg1-1/n kg-1for three herbicides. These results indicated that intraparticle diffusion and external mass transport were the main rate controlling steps of the adsorption of herbicides on sediment and that the chemical adsorption was dominant during the adsorption processes. The calculated hysteresis coefficient H were 0.9422,0.7877 and 0.744 for imazmox, imazapic and imazethapyr in raw sediment, respectively, indicating that there is a hysteresis in desorption. The influences of solution pH and sediment organic carbon content on the imidazolinone herbicide adsorption behaviors were also examined. Which shown that the adsorption process for herbicides was highly pH-dependent and adsorption efficiency was closely related to the organic matter content of the sediment, suggesting that electrostatic interactions played crucial roles in the adsorption behavior between sediment and imidazolinone herbicides, and the herbicides were mostly absorbed by the amorphous materials of sediment. These research findings are important for assessing the fate and transport of imidazolinone herbicides in water-sediment systems.