Magnesium oxide nanoparticles reduce clubroot by regulating plant defense response and rhizosphere microbial community of tumorous stem mustard (Brassica juncea var. tumida).

Clubroot, caused by Plasmodiophora brassicae, is a major disease that significantly impairs the yield of cruciferous crops and causes significant economic losses across the globe. The prevention of clubroot, especially in tumorous stem mustard (without resistant varieties), are is limited and primarily relies on fungicides. Engineered nanoparticles have opened up new avenues for the management of plant diseases, but there is no report on their application in the prevention of clubroot. The results showed that the control efficacy of 500 mg/L MgO NPs against clubroot was 54.92%. However, when the concentration was increased to 1,500 and 2,500 mg/L, there was no significant change in the control effect. Compared with CK, the average fresh and dry weight of the aerial part of plants treated with MgO NPs increased by 392.83 and 240.81%, respectively. Compared with the F1000 treatment, increases were observed in the content of soil available phosphorus (+16.72%), potassium (+9.82%), exchangeable magnesium (+24.20%), and water-soluble magnesium (+20.64%) in the 1,500 mg/L MgO NPs treatment. The enzyme-linked immune sorbent assay (ELISA) results showed that the application of MgO NPs significantly increased soil peroxidase (POD, +52.69%), alkaline protease (AP, +41.21%), alkaline phosphatase (ALP, +79.26%), urease (+52.69%), and sucrase (+56.88%) activities; And also increased plant L-phenylalanine ammonla-lyase (PAL, +70.49%), polyphenol oxidase (PPO, +36.77%), POD (+38.30%), guaiacol peroxidase (POX, +55.46%) activities and salicylic acid (SA, +59.86%) content. However, soil and plant catalase (CAT, -27.22 and - 19.89%, respectively), and plant super oxidase dismutase (SOD, -36.33%) activities were significantly decreased after the application of MgO NPs. The metagenomic sequencing analysis showed that the MgO NPs treatments significantly improved the α-diversity of the rhizosphere soil microbial community. The relative abundance of beneficial bacteria genera in the rhizosphere soil, including Pseudomonas, Sphingopyxis, Acidovorax, Variovorax, and Bosea, was significantly increased. Soil metabolic functions, such as oxidative phosphorylation (ko00190), carbon fixation pathways in prokaryotes (ko00720), indole alkaloid biosynthesis (ko00901), and biosynthesis of various antibiotics (ko00998) were significantly enriched. These results suggested that MgO NPs might control clubroot by promoting the transformation and utilization of soil nutrients, stimulating plant defense responses, and enriching soil beneficial bacteria.

High-efficiency removal of tetracycline from water by electrolysis-assisted NZVI: mechanism of electron transfer and redox of iron.

A low-cost, stable and non-precious metal catalyst for efficient degradation of tetracycline (TC), one of the most widely used antibiotics, has been developed. We report the facile fabrication of an electrolysis-assisted nano zerovalent iron system (E-NZVI) that achieved TC removal efficiency of 97.3% with the initial concentration of 30 mg L-1 at an applied voltage of 4 V, which was 6.3 times higher than the NZVI system without an applied voltage. The improvement caused by electrolysis was mainly attributed to the stimulation of corrosion of NZVI, which accelerated the release of Fe2+. And Fe3+ in the E-NZVI system could receive electrons to reduce to Fe2+, which facilitated the conversion of ineffective ions to effective ions with reducing ability. Moreover, electrolysis assisted to expand the pH range of the E-NZVI system for TC removal. The uniformly dispersed NZVI in the electrolyte facilitated the collection and secondary contamination could be prevented with the easy recycling and regeneration of the spent catalyst. In addition, scavenger experiments revealed that the reducing ability of NZVI was accelerated in the presence of electrolysis, rather than oxidation. TEM-EDS mapping, XRD and XPS analyses indicated that electrolytic effects could also delay the passivation of NZVI after a long run. This is mainly due to the increased electromigration, implying that the corrosion products of iron (iron hydroxides and oxides) are not formed mainly near or on the surface of NZVI. The electrolysis-assisted NZVI shows excellent removal efficiency of TC and is a potential water treatment method for the degradation of antibiotic contaminants.

Arginine metabolism and deprivation in cancer therapy.

Certain cancer cells with nutrient auxotrophy and have a much higher nutrient demand compared with normal human cells. Arginine as a versatile amino acid, has multiple biological functions in metabolic and signaling pathways. Depletion of this amino acid by arginine depletor is generally well tolerated and has become a targeted therapy for arginine auxotrophic cancers. However, the modulatory eff ;ect of arginine on cancer cells is very complicated and still controversial. Therefore, this article focuses on arginine metabolism and depletion therapy in cancer treatment to provide systemical review on this issue.