Impact of dichlorprop on soil microbial community structure and diversity during its enantioselective biodegradation in agricultural soils

Effect of chlorantraniliprole on soil bacterial and fungal diversity and community structure

Chlorantraniliprole (CAP) is an insecticide with low toxicity and high efficiency, which is widely used in agriculture in China. However, its potential ecological risks remain unknown. In this study, we investigated the impact of different CAP concentrations on bacterial and fungal communities in soil based on high-throughput sequencing. The results showed that CAP application had no significant effect on soil bacterial and fungal diversity, but altered the bacterial and fungal community structure. In particular, the soil bacterial and fungal community structure in the low CAP concentration treatment group exhibited large variability. Compared with 0 day, the phylum level of bacteria changed at 115 days, and fungi changed at 175 days, indicating that soil microbial community might have significant correlation with CAP degradation in soil. Correlation analysis between soil properties and microbial communities showed that TN, TP, and NO₃-N were three key factors that significantly influenced microbial community structure. These results provide basic data for studying the effects of pesticides on ecosystem and potential remediation strategies of polluted soil.

The Adsorption and Degradation of 2, 4-D Affected by Soil Organic Carbon and Clay

More has yet to be indicated on the adsorption and degradation processes, determining herbicides recycling in the environment. The sorption and degradation of 2, 4-D, affected by organic carbon (1.92-2.81%), soil clay (20-30%) and pH of the citrus orchards of Mazandaran province, Iran was investigated using HPLC equipped with UV detector for the identification and quantification of soil 2, 4-D. The adsorption (k_d) and degradation (K_deg) coefficients were determined using Freundlich and the first-degree kinetic equations. Gardens C (2.45 mL g^-1), and B (0.3 mL g^-1), with the highest (8.2 g day^-1) and least (2.7 g day^-1) degradation coefficients, had the highest and lowest K_d values. K_d variations with pH indicated higher adsorption of 2, 4-D in acidic pH. Due to the high presence of functional groups and soil biological activities, organic carbon affected the adsorption and degradation rates more effectively, which is of economic and environmental significance.

Biodegradation of two persistent aromatic compounds by using oil shale

Low-cost oil shale was investigated as a biodegradation promoter material, in order to exploit its potential for more widespread and efficient usage in the elimination of pollution. Degradation of two model pollutants, 4-nitrophenol and phenol, was examined in the presence of oil shale in a batch system. In order to investigate the role of the natural microflora of the oil shale in degradation, sodium azide was added to inhibit microbial growth. The effect of metal ions was also investigated. In the sodium azide-free solutions the model pollutants were completely degraded up to 2000 µmol/L concentration in a dose-dependent way, while the addition of sodium azide delayed greatly but did not stop the degradation. Manganese(II) ions increased the rate of the degradation of 4-nitrophenol, and given quantities of iron(II), manganese(II) or zinc(II) ions were also effective in degradation of phenol. Our results suggest that oil shale is not only an adsorbent but has an active role in the degradation of pollutants by its natural microflora. Utilizing these features of oil shale, it is a suitable candidate as an ameliorating agent, which can also be used in industrial size.

Mechanisms of the enantioselective effects of phenoxyalkanoic acid herbicides DCPP and MCPP

Phenoxyalkanoic acids (PAAs), synthetic indole-3-acetic acid (IAA) auxin mimics, are widely used as herbicides. Many PAAs are chiral molecules and show strong enantioselectivity in their herbicidal activity; however, there is a lack of understanding of mechanisms driving enantioselectivity. This study aimed to obtain a mechanistic understanding of PAA enantioselectivity using dichlorprop and mecoprop as model PAA compounds. Molecular docking, in vitro ³H-IAA binding assay, and surface plasmon resonance analysis showed that the R enantiomer was preferentially combined with TIR1-IAA7 (Transport Inhibitor Response1- Auxin-Responsive Protein IAA7) than the S enantiomer. In vivo tracking using ¹⁴C-PAAs showed a greater absorption of the R enantiomer by Arabidopsis thaliana, and further comparatively enhanced translocation of the R enantiomer to the nucleus where the auxin co-receptor is located. These observations imply that TIR1-IAA7 is a prior target for DCPP and MCPP, and that PAA enantioselectivity occurs because the R enantiomer has a stronger binding affinity for TIR1-IAA7 as well as a greater plant absorption and translocation capability than the S enantiomer. The improved understanding of PAA enantioselectivity is of great significance, as the knowledge may be used to design "green" molecules, such as R enantiomer enriched products, leading to improved plant management and environmental sustainability.

New Target in an Old Enemy: Herbicide (R)-Dichlorprop Induces Ferroptosis-like Death in Plants

Iron is an essential microelement in plants that is involved in several growth processes. The use of herbicides may cause the abnormal aggregation of iron in leaves, but the regulatory mechanisms underlying this phenomenon remain unclear. Here, we show that chiral herbicide (R)-dichlorprop ((R)-DCPP) triggers ferroptosis-like death in Arabidopsis thaliana. (R)-DCPP led to reactive oxygen species (ROS) accumulation and iron aggregation, and these processes were iron dependent. Under (R)-DCPP treatment, ROS, lipid hydrogen peroxides, and malondialdehyde were significantly accumulated. In addition, (R)-DCPP induced the depletion of glutathione, ascorbic acid, and glutathione peroxidase as well as the accumulation of toxic lipid peroxides. Thus, oxidation imbalance led to cell death, and this mode of action could be inhibited by the ferroptosis inhibitor ferrostatin-1 or ciclopirox olamine. NADPH oxidases were found to be involved in herbicide-induced ROS accumulation, and lipoxygenase and NADPH cytochrome P450 oxidase were shown to positively regulate (R)-DCPP-induced lipid peroxidation. Overall, these results indicate that the iron- and ROS-dependent signaling cascades were involved in the (R)-DCPP-induced phytotoxicity pathway, which disrupted the structure of plant cell membranes and triggered ferroptosis. Generally, this study provides new insight into the mechanisms of pesticide phytotoxicity and suggests new therapeutic directions to protect nontarget plants.