Exposure to pyrazosulfuron-ethyl induces immunotoxicity and behavioral abnormalities in zebrafish embryos

Pyrazosulfuron-ethyl is one of the most widely used herbicides in agriculture and can be widely detected in aquatic ecosystems. However, its biosafety, including its potential toxic effects on aquatic organisms and its mechanism, is still poorly understood. As an ideal vertebrate model, zebrafish, the effect of pyrazosulfuron-ethyl on early embryonic development and immunotoxicity of zebrafish can be well evaluated. From 10 to 72 h post fertilization (hpf), zebrafish embryos were exposed to 1, 5, and 9 mg/L pyrazosulfuron-ethyl which led in a substantial reduction in survival, total length, and heart rate, as well as a range of behavioral impairments. In zebrafish larvae, the number of neutrophils and macrophages was considerably decreased and oxidative stress levels increased in a dose-dependent way after pyrazosulfuron-ethyl exposure. And the expression of immune-related genes, such as TLR-4, MyD88 and IL-1β, were downregulated by pyrazosulfuron-ethyl exposure. Moreover, pyrazosulfuron-ethyl exposure also inhibited motor behavior. Notch signaling was upregulated after exposure to pyrazosulfuron-ethyl, while inhibition of Notch signaling pathway could rescue immunotoxicity. Therefore, our findings suggest that pyrazosulfuron-ethyl has the potential to induce immunotoxicity and neurobehavioral changes in zebrafish larvae.

Adaptation mechanism and tolerance of Rhodopseudomonas palustris PSB-S under pyrazosulfuron-ethyl stress

BACKGROUND

Pyrazosulfuron-ethyl is a long lasting herbicide in the agro-ecosystem and its residue is toxic to crops and other non-target organisms. A better understanding of molecular basis in pyrazosulfuron-ethyl tolerant organisms will shed light on the adaptive mechanisms to this herbicide.

RESULTS

Pyrazosulfuron-ethyl inhibited biomass production in Rhodopseudomonas palustris PSB-S, altered cell morphology, suppressed flagella formation, and reduced pigment biosynthesis through significant suppression of carotenoids biosynthesis. A total of 1127 protein spots were detected in the two-dimensional gel electrophoresis. Among them, 72 spots representing 56 different proteins were found to be differently expressed using MALDI-TOF/TOF-MS, including 26 up- and 30 down-regulated proteins in the pyrazosulfuron-ethyl-treated PSB-S cells. The up-regulated proteins were involved predominantly in oxidative stress or energy generation pathways, while most of the down-regulated proteins were involved in the biomass biosynthesis pathway. The protein expression profiles suggested that the elongation factor G, cell division protein FtsZ, and proteins associated with the ABC transporters were crucial for R. palustris PSB-S tolerance against pyrazosulfuron-ethyl.

CONCLUSION

Up-regulated proteins, including elongation factor G, cell division FtsZ, ATP synthase, and superoxide dismutase, and down-regulated proteins, including ALS III and ABC transporters, as well as some unknown proteins might play roles in R. palustris PSB-S adaptation to pyrazosulfuron-ethyl induced stresses. Functional validations of these candidate proteins should help to develope transgenic crops resistant to pyrazosulfuron-ethyl.

Effect of wheat and rice straw biochars on pyrazosulfuron-ethyl sorption and persistence in a sandy loam soil

The objective of this research was to investigate the effect of wheat and rice biochars on pyrazosulfuron-ethyl sorption in a sandy loam soil. Pyrazosulfuron-ethyl was poorly sorbed in the soil (3.5-8.6%) but biochar amendment increased the herbicide adsorption, and the effect varied with the nature of the feedstock and pyrolysis temperature. Biochars prepared at 600°C were more effective in adsorbing pyrazosulfuron-ethyl than biochars prepared at 400°C. Rice biochars were better than wheat biochars, and higher herbicide adsorption was attributed to the biochar surface area/porosity. The Freundlich constant 1/n suggested nonlinear isotherms, and nonlinearlity increased with increase in the level of biochar amendment. Desorption results suggested sorption of pyrazosulfuron-ethyl was partially irreversible, and the irreversibility increased with increase in the level of biochar. Both sorption and desorption of pyrazosulfuron-ethyl correlated well with the content of biochars. The free energy change (ΔG) indicated that the pyrazosulfuron-ethyl sorption process was exothermic, spontaneous and physical in nature. Persistence studies indicated that biochar (0.5%) amendment did not have significant effect on herbicide degradation, and its half-life values in the control, 0.5% WBC600- and RBC600-amended rice planted soils were 7, 8.6, and 10.4 days, respectively.

Fungal degradation of an acetolactate synthase (ALS) inhibitor pyrazosulfuron-ethyl in soil

Owing to reported phytotoxicity of some sulfonylurea class of herbicides in number of sensitive crops and higher persistence in soil, present study was conducted to isolate and identify pyrazosulfuron-ethyl degrading fungi from soil of rice field. Penicillium chrysogenum and Aspergillus niger, were isolated and identified from rhizospere soil of rice field, as potent pyrazosulfuron-ethyl degrading fungi. Degradation of pyrazosulfuron-ethyl by P. chrysogenum and A. niger, yielded transformation products/metabolites which were identified and characterized by LC/MS/MS. The rate of dissipation of pyrazosulfuron-ethyl was found higher in soil of rice field and soil inoculated with P. chrysogenum. This showed important route of degradation of pyrazosulfuron-ethyl by microbes apart from chemical degradation.