The stereoselectivity of metconazole on wheat grain filling and harvested seeds germination: Implication for the application of triazole chiral pesticides

Stereo-selective cardiac toxicity induced by metconazole via oxidative stress and the wnt/β-catenin signaling pathway in zebrafish embryos

Metconazole (MEZ), a chiral triazole fungicide, produces enantioselective adverse effects in non-target organisms. Among MEZ's isomers, cis-MEZ displays robust antimicrobial properties. Evaluating MEZ and cis-MEZ's toxicity may mitigate fungicide usage and safeguard non-target organisms. Our study evaluated the toxicity of MEZ and its cis-isomers at concentrations of 0.02, 0.2, 2, and 4 mg L-1. We report stereoselectivity and severe cardiovascular defects in zebrafish, including pericardial oedema, decreased heart rate, increased sinus venous and bulbous arteries distances, intersegmental vessel defects, and altered cardiovascular development genes (hand2, gata4, nkx2.5, tbx5, vmhc, amhc, dll4, vegfaa, and vegfc). Further, MEZ significantly increased oxidative stress and apoptosis in zebrafish, primarily in the cardiac region. Isoquercetin, an antioxidant found in plants, partially mitigates MEZ-induced cardiac defects. Furthermore, MEZ upregulated the Wnt/β-catenin pathway genes (wnt3, β-catenin, axin2, and gsk-3β) and β-catenin protein expression. Inhibitor of Wnt Response-1 (IWR-1) rescued MEZ-induced cardiotoxicity. Our findings highlight oxidative stress, altered cardiovascular development genes, and upregulated Wnt/β-catenin signaling as contributors to cardiovascular toxicity in response to MEZ and cis-MEZ treatments. Importantly, 1R,5S-MEZ exhibited greater cardiotoxicity than 1S,5R-MEZ. Thus, our study provides a comprehensive understanding of cis-MEZ's cardiovascular toxicity in aquatic life.

Enantioselective bioaccumulation, biotransformation and spatial distribution of chiral fungicide difenoconazole in earthworms (Eisenia fetida)

The enantioselective environmental behavior of difenoconazole, a widely utilized triazole fungicide commonly detected in agricultural soils, has yet to be comprehensively explored within the earthworm-soil system. To address this research gap, we investigated the bioaccumulation and elimination kinetics, degradation pathways, biotransformation mechanisms, spatial distribution, and toxicity of chiral difenoconazole. The four stereoisomers of difenoconazole were baseline separated and analyzed using SFC-MS/MS. Pronounced enantioselectivity was observed during the uptake phase, with earthworms exhibiting a preference for (2R,4R)-difenoconazole and (2R,4S)-difenoconazole. A total of five transformation products (TPs) were detected and identified using UHPLC-QTOF/MS in the earthworm-soil system. Four of the TPs were detected in both earthworm and soil, and one TP was produced only in eaerthwroms. Hydrolysis and hydroxylation were the primary transformation pathways of difenoconazole in both earthworms and soil. Furthermore, a chiral TP, 3-chloro, 4-hydroxy difenoconazole, was generated with significant enantioselectivity, and molecular docking results indicate the greater catalytic bioactivity of (2R,4R)- and (2R,4S)-difenoconazole, leading to the preferential formation of their corresponding hydroxylated TPs. Furthermore, Mass Spectrometry Imaging (MSI) was applied for the first time to explore the spatial distribution of difenoconazole and the TPs in earthworms, and the "secretory zone" was found to be the dominant region to uptake and biodegrade difenoconazole. ECOSAR predictions highlighted the potentially hazardous impact of most difenoconazole TPs on aquatic ecosystems. These findings are important for understanding the environmental fate of difenoconazole, evaluating environmental risks, and offering valuable insights for guiding scientific bioremediation efforts.

Stereoselective cardiotoxic effects of metconazole on zebrafish (Danio rerio) based on AGE-RAGE signalling pathway

Metconazole (MEZ) is a novel chiral triazole fungicide that is widely used to prevent and control soil-borne fungal pathogens and other fungal diseases. However, it has a long half-life in aquatic environments and thus poses potential environmental risks. This study evaluates the acute and stereoselective cardiotoxicity of MEZ in zebrafish (Danio rerio) embryos. In addition, transcriptomics, real-time quantitative PCR, enzyme activity determination, and molecular docking are performed to evaluate the molecular mechanisms underlying the cardiotoxicity of MEZ in zebrafish. MEZ decreases the heart rate while increasing the pericardial oedema rate; additionally, it induces stereoselective cardiotoxicity. 1S,5S-MEZ exhibits stronger cardiotoxicity than 1R,5R-MEZ. Furthermore, MEZ increases the expression of Ahr-associated genes and the transcription factors il6st, il1b, and AP-1. Heart development-related genes, including fbn2b, rbm24b, and tbx20 are differentially expressed. MEZ administration alters the activities of catalase, peroxidase, and glutathione-S-transferase in zebrafish larvae. Molecular docking indicates that 1R,5R-MEZ binds more strongly to the inhibitor-binding sites of p38 in the AGE-RAGE signalling pathway than to other MEZ enantiomers. Studies conducted in vivo and in silico have established the enantioselective cardiotoxicity of MEZ and its underlying mechanisms, highlighting the need to evaluate the environmental risk of chiral MEZ in aquatic organisms at the enantiomeric level.

Stereoselectivity of paclobutrazol enantiomers to oxidative stress in wheat

Chiral pesticides have the special chiral structures, so enantioselective biological effects are usually observed in living organisms. Current study used paclobutrazol as a case study and explored the enantioselective degradation and oxidative stress effect on wheat. The results demonstrated that the degradation of R-paclobutrazol was faster than S-paclobutrazol significantly and improved the content of MDA and O2 - in wheat plants, which proved that the R-paclobutrazol induced oxidative damage in wheat, showing selective biological effects, and S-paclobutrazol was friendly to wheat. This study provided a theoretical basis for the selective activity of chiral pesticides and the development of chiral pesticide monomers.

Highly selective chiral molecules detection by terahertz SWNT-based metamaterials

The selectively effective behavior of chiral molecules may have deleterious consequences on nontarget organisms and the surrounding ecosystem. Therefore, detecting enantiomers in minute concentrations is essential to prevent undesired side effects. The majority of approaches, including chiral coupling in the shortwave band with sophisticated fabrication and eluting molecules based on the time signal, are incapable of achieving rapid chiral detection. In this study, we use chemically modified single-wall carbon nanotubes (SWNT) as metamaterials to increase sensitivity in the THz region while using it as the chiral stationary phase to selectively bundle one of two enantiomers. We identify chiral molecules by detecting the optical response of chemically modified SWNT-based metamaterials. The measured spectra, in particular, show very selective indications in the spectral region directly associated with distinct chiral responses, which is caused by the difference in binding forces between chemically modified SWNTs and chiral molecules. In addition, we demonstrated that the desired resonance for aqueous sensing was enveloped resonance as opposed to that with a high quality factor, which was sought for drip-dry detection. Our findings provide a simple platform for highly selectively sensing chiral compounds.

Targeted and non-targeted analysis for the investigation of pesticides influence on wheat cultivated under field conditions

A comprehensive approach was applied to evaluate the effects of pesticides on the metabolism of wheat (Triticum aestivum L). The application of commercially available pesticide formulations under field cultivation conditions provided a source of metabolic data unlimited by model conditions, representing a novel approach to study the effects of pesticides on edible plants. Gas and liquid chromatography coupled to tandem mass spectrometry were employed for targeted and non-targeted analysis of wheat roots and shoots sampled six times during the six-week experiment. The applied pesticides: prothioconazole, tebuconazole, fluoxastrobin, diflufenican, florasulam, and penoxulam were found at concentrations ranging 0.0070-25.20 mg/kg and 0.0020-2.2 mg/kg in the wheat roots and shoots, respectively. The following pesticide metabolites were identified in shoots: prothioconazole-desthio (prothioconazole metabolite), 5-(4-chlorophenyl)-2,2-dimethyl-3-(1,2,4-triazol-1-ylmethyl)pentane-1,3-diol (tebuconazole metabolite), and N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl)-2,4-dihydroxy-6-(trifluoromethyl)benzene sulphonamide (penoxulam metabolite). The metabolic fingerprints and profiles changed during the experiment, reflecting the cumulative response of wheat to both its growth environment and pesticides, as well as their metabolites. Approximately 15 days after the herbicide treatment no further changes in the plant metabolic profiles were observed, despite the presence of pesticide and their metabolites in both roots and shoots. This is the first study to combine the determination of pesticides and their metabolites plant tissues with the evaluation of plant metabolic responses under field conditions. This exhaustive approach contributes to broadening the knowledge of pesticide effects on edible plants, relevant to food safety.

Isolation of Sphingomonas sp. AJ-1 and its enantioselective S-methylation of the triazole fungicide prothioconazole

Prothioconazole is a widely used chiral triazole fungicide, and its residue pollution has attracted wide attention in recent years. However, little is known about microbial metabolic processes of prothioconazole enantiomers. In this study, a prothioconazole-degrading strain, Sphingomonas sp. AJ-1, was isolated from activated sludge. The optimal temperature and pH for prothioconazole degradation by strain AJ-1 were 30 °C and 6.0, respectively, and the degradation rate of prothioconazole by strain AJ-1 was negatively correlated with the initial concentration. When supplemented with additional carbon source, the degradation rates of 10 mg/L (Rac)-/(S)-/(R)-prothioconazole by strain AJ-1 were 76.0 %, 100.0 % and 64.8 % within 6 d, respectively. The CS bond of prothioconazole was methylated to produce (S)-/(R)-prothioconazole-S-methyl by strain AJ-1, but the degradation rate of prothioconazole by strain AJ-1 with (S)-enantiomer was 2.54-fold of that with (R)-enantiomer. Moreover, the toxicity of (Rac)-prothioconazole-S-methyl was 5.57 times lower than that of (Rac)-prothioconazole to Pseudokirchneriella subcapitata. The results showed that strain AJ-1 had obvious enantioselective metabolism for prothioconazole, and this metabolism was a detoxification process. This study provides new insights into the enantioselective metabolism of the chiral fungicide prothioconazole in microorganisms.

Biocontrol and plant growth promotion by combined Bacillus spp. inoculation affecting pathogen and AMF communities in the wheat rhizosphere at low salt stress conditions

Applying plant growth-promoting rhizobacteria (PGPR) improves the efficiency of soil-borne disease control and is considered a sustainable practice. However, the effect of PGPR on the fungal community, especially pathogenic fungi and arbuscular mycorrhizal fungi (AMF), remains unclear. In this study, we examined the effects of a compound microbial agent (consisting of Bacillus subtilis HG-15 and Bacillus velezensis JC-K3) on the incidence and yield of wheat under low salt stress, as well as compared the diversity and community composition of the rhizosphere fungal and AMF communities of wheat in the CK (not inoculated bacterial agent) and BIO (inoculated with a bacterial agent) groups. Chlorophyll relative content (SPAD), net photosynthesis rate (Pn), transpiration rate (Tr), leaf water use efficiency (WUE _L), grains per spike and wheat yield in the BIO group increased more than in the CK group. The number of diseased plants and disease incidence was observed to be reduced. The relative efficacy reached 79.80%. We classified 1007 fungal operational taxonomic units (OTU) based on Miseq sequencing data: 11 phyla, 173 families, 319 genera, and 521 species. Fifty-four OTUs were classified from the AMF effective sequences, including 1 phylum, 3 families, 3 genera, and 17 species. The inoculation of bacterial agents reduced the relative abundance of pathogen genera such as Gibberella, Fusarium, Cladosporium, and Alternaria in wheat rhizosphere. It increased the relative abundance of AMF species such as Glomus-group-B-Glomus-lamellosu-VTX00193, Glomus-viscosum-VTX00063, and Glomus-Glo2-VTX00280. In addition, pH, EC, exchangeable K, available N, total N, organic matter, and olsen P were the main driving forces for shaping wheat rhizosphere fungi. The pH value was positively correlated with the relative abundance of fungal communities in soil, especially Gibberella, Cladosporium, Fusarium, and Alternaria. In summary, inoculation with Bacillus subtilis HG-15 and Bacillus velezensis JC-K3 affected wheat yield, incidence, rhizosphere soil chemical properties, rhizosphere fungi, and AMF fungal diversity and community. The findings may provide a theoretical foundation and strain support for constructing efficient PGPR-community and clarifying its mechanism of pathogenic bacteria inhibition.

Systematic evaluation of chiral pesticides at the enantiomeric level: A new strategy for the development of highly effective and less harmful pesticides

Over the past few decades, pesticides have been used in large quantities, and they pose potential risks to organisms across various environments. Reducing the use of pesticides and their environmental risks has been an active research focus and difficult issue worldwide. As a class of pesticides with special structures, chiral pesticides generally exhibit enantioselectivity differences in biological activity, ecotoxicity, and environmental behavior. At present, replacing the racemates of chiral pesticides by identifying and developing their individual enantiomers with high efficiency and environmentally friendly characteristics is an effective strategy to reduce the use of pesticides and their environmental risks. In this study, we review the stereoselective behaviors of chiral pesticide, including their environmental behavior, stereoselective biological activity, and ecotoxicity. In addition, we emphasize that the systematic evaluation of chiral pesticides at the enantiomeric level is a promising novel strategy for developing highly effective and less harmful pesticides, which will provide important data support and an empirical basis for reducing pesticide application.

Risk Assessment of the Chiral Fungicide Triticonazole: Enantioselective Effects, Toxicity, and Fate

The enantioselective toxicity of triticonazole (TRZ) to non-target organisms, the effect on wheat growth and quality, and the environmental fate of TRZ were investigated systematically in this study. The acute toxicity of S-TRZ to non-target aquatic and terrestrial organisms was greater than that of rac-TRZ and R-TRZ. The S-enantiomer significantly inhibited the growth and lodging resistance of wheat. S- and R-TRZ not only reduced the grain yield but also inhibited the activities of ADP-glucose pyrophosphorylase (AGPase) and starch synthase. The results of homology modeling and molecular docking further showed that the inhibition of AGPase activity by the two enantiomers hindered the accumulation of starch. By contrast, the racemate promoted the growth and development of wheat and improved grain quality. And the half-lives of the racemate in stems, grains, leaves, and soils were shorter than those of the enantiomers. The results of risk quotient (RQ) values showed that the application of TRZ enantiomers during wheat planting would bring a higher potential dietary risk to Chinese consumers. In comprehensive consideration of these results, the application of the racemate may be safer and more reasonable at the flowering stage of wheat.