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.

[Response of Photosynthetic Bacterial Community to Cadmium Contamination in Paddy Soil].

Heavy metal pollution in rice fields leads to huge losses in rice yield every year and is thus of increasing concern. Therefore, it is important to understand the changes in the microecology and physicochemical properties of paddy soil under different levels of cadmium pollution. The purpose of this study was to investigate the response of the photosynthetic bacterial community in paddy soil to different cadmium pollution levels using 16S sequencing technology. The results showed that pH, total cadmium, and available cadmium content decreased gradually with the increase in cadmium pollution. The soil α diversity was slightly different in the high cadmium (Cd), medium Cd, and low Cd groups; however, the enriched photosynthetic populations and photosynthetic bacterial communities were significantly different among these groups. The effective connections between photosynthetic bacterial species in the high Cd group were significantly greater than those in the medium and low Cd groups, the connections were closer, and the density was higher. Alkaline nitrogen, pH, available (P/K), total (N/P), organic matter, total cadmium, and available cadmium were important factors affecting the photosynthetic bacterial community and were significantly correlated with the photosynthetic bacterial community, explaining 59.90% of the variation in the photosynthetic bacterial community. Effective Cd content was significantly positively correlated with Methylorubrum populi, Methylorubrum extorquens, Methylobacterium sp. Leaf125, and Rhodopseudomonas sp. AAP120 (R>0.05, P<0.05). This study will provide a theoretical basis for the microbial remediation of cadmium contamination in paddy fields. This study is important for understanding the effects of cadmium pollution on specific functional microbial populations in paddy soils.

Physiological change alters endophytic bacterial community in clubroot of tumorous stem mustard infected by Plasmodiophora brassicae.

BACKGROUND: Endophytic bacteria are considered as symbionts living within plants and are influenced by abiotic and biotic environments. Pathogen cause biotic stress, which may change physiology of plants and may affect the endophytic bacterial communiy. Here, we reveal how endophytic bacteria in tumorous stem mustard (Brassica juncea var. tumida) are affected by plant physiological changes caused by Plasmodiophora brassicae using 16S rRNA high-throughput sequencing. RESULTS: The results showed that Proteobacteria was the dominant group in both healthy roots and clubroots, but their abundance differed. At the genus level, Pseudomonas was dominant in clubroots, whereas Rhodanobacter was the dominant in healthy roots. Hierarchical clustering, UniFrac-weighted principal component analysis (PCA), non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) indicated significant differences between the endophytic bacterial communities in healthy roots and clubroots. The physiological properties including soluble sugar, soluble protein, methanol, peroxidase (POD) and superoxide dismutase (SOD) significantly differed between healthy roots and clubroots. The distance-based redundancy analysis (db-RDA) and two-factor correlation network showed that soluble sugar, soluble protein and methanol were strongly related to the endophytic bacterial community in clubroots, whereas POD and SOD correlated with the endophytic bacterial community in healthy roots. CONCLUSIONS: Our results illustrate that physiologcial changes caused by P. brassicae infection may alter the endophytic bacterial community in clubroots of tumorous stem mustard.

Infection of Plasmodiophora brassicae changes the fungal endophyte community of tumourous stem mustard roots as revealed by high-throughput sequencing and culture-dependent methods.

Diverse fungal endophytes live in plants and are shaped by some abiotic and biotic stresses. Plant disease as particular biotic stress possibly gives an impact on the communities of fungal endophytes. In this study, clubroot disease caused by an obligate biotroph protist, Plasmodiophora brassicae, was considered to analyze its influence on the fungal endophyte community using an internal transcribed spacer (ITS) through high-throughput sequencing and culture-dependent methods. The results showed that the diversity of the endophyte community in the healthy roots was much higher than the clubroots. Ascomycota was the dominant group of endophytes (Phoma, Mortierella, Penicillium, etc.) in the healthy roots while P. brassicae was the dominant taxon in the clubroots. Hierarchical clustering, principal component analysis (PCA), principal coordinates analysis (PCoA) and analysis of similarities (ANOSIM) indicated significant differences between the endophyte communities in the healthy roots and clubroots. Linear discriminant analysis effect size (LefSe) analysis showed that the dominant genera could be regarded as potential biomarkers. The endophyte community in the healthy roots had a more complex network compared with the clubroots. Also, many plant pathogenic Fusarium were isolated from the clubroots by the culture-dependent method. The outcome of this study illustrates that P. brassicae infection may change the fungal endophyte community associated with the roots of tumourous stem mustard and facilitates the entry of soil pathogen into the roots.

Preliminary research on the expression, purification and function of the apoptotic fusion protein, Sival.

The objective of the present study was to investigate cloning, expression, and functions of the recombinant protein, Siva1. Siva1 gene was synthesized by RT-PCR from HCT116 cells. Plasmids were cleaved with the restriction endonuclease, BamH1/Sal1 and products were connected to pQE30, which underwent cleavage by BamH1/Sal1. The recombinant plasmid, pQE30-Siva1, was identified after digestion with restriction endonucleases followed by transformation into E. coli M15. Expression of Siva1 was induced by IPTG and identified by SDS- PAGE following purification with affinity chromatography. The results showed that size of Siva1 was 12 kDa, consistent with the molecular weight of the His-Siva1 fusion protein. Functional test demonstrated that Siva1 significantly inhibited the invasion and migration of HCT116 cells. It may thus find clinical application for control of cancers.

[Experimental study of HIF-1alpha antisense oligonucleotide on implanted human gastric cancer in nude mice].

OBJECTIVE: To observe the effect of HIF-1alpha antisense oligonucleotide (HIF-1alpha ASOND) on implanted human gastric cancer in nude mice. METHODS: BALB/c nude mice were subcutaneously transplanted with SCG-7901 tumor cells, then the mice were randomly divided into antisense oligonucleotide (ASOND) group, sense oligonucleotide (SOND) group and the control group. The HIF-1alpha ASOND complexed with cationic liposome, HIF-1alpha SOND complexed with cationic liposome and liposome were injected intra-tumorally in the above groups, respectively. Tumor growth curve in each group animals was observed. The tumor weight was measured and then the rate of inhibition was calculated. The morphological changes of tumor cells was observed under microscope. The expression of HIF-1alpha, VEGF and MVD in tumor tissue was determined by immunohistochemical methods. RESULTS: The growth of tumor of ASOND group was significantly inhibited. There was statistically significant difference (P < 0.05) in the weight of tumor between ASOND group and control group. The inhibitory rates of ASOND group and SOND group were 47.94% and 16.88% respectively, and both inhibitory rates were significantly different (P < 0.01). The tumor tissue expression of HIF-1alpha, VEGF and MVD in ASOND group was significantly lower than those of SOND and the control groups (P < 0.01). CONCLUSION: In tumor tissue, the injection of HIF-1alpha ASOND to treat gastric carcinoma transplanted subcutaneously in nude mice can reduce the expression of HIF-1alpha, consequently reduce the formation of VEGF and new blood vessels, so as to achieve inhibition of tumor growth.