Ethanol mediates the interaction between Caenorhabditis elegans and the nematophagous fungus Purpureocillium lavendulum.

Accurately recognizing pathogens by the host is vital for initiating appropriate immune response against infecting microorganisms. Caenorhabditis elegans has no known receptor to recognize pathogen-associated molecular pattern. However, recent studies showed that nematodes have a strong specificity for transcriptomes infected by different pathogens, indicating that they can identify different pathogenic microorganisms. However, the mechanism(s) for such specificity remains largely unknown. In this study, we showed that the nematophagous fungus Purpureocillium lavendulum can infect the intestinal tract of the nematode C. elegans and the infection led to the accumulation of reactive oxygen species (ROS) in the infected intestinal tract, which suppressed fungal growth. Co-transcriptional analysis revealed that fungal genes related to anaerobic respiration and ethanol production were up-regulated during infection. Meanwhile, the ethanol dehydrogenase Sodh-1 in C. elegans was also up-regulated. Together, these results suggested that the infecting fungi encounter hypoxia stress in the nematode gut and that ethanol may play a role in the host-pathogen interaction. Ethanol production in vitro during fungal cultivation in hypoxia conditions was confirmed by gas chromatography-mass spectrometry. Direct treatment of C. elegans with ethanol elevated the sodh-1 expression and ROS accumulation while repressing a series of immunity genes that were also repressed during fungal infection. Mutation of sodh-1 in C. elegans blocked ROS accumulation and increased the nematode's susceptibility to fungal infection. Our study revealed a new recognition and antifungal mechanism in C. elegans. The novel mechanism of ethanol-mediated interaction between the fungus and nematode provides new insights into fungal pathogenesis and for developing alternative biocontrol of pathogenic nematodes by nematophagous fungi. IMPORTANCE Nematodes are among the most abundant animals on our planet. Many of them are parasites in animals and plants and cause human and animal health problems as well as agricultural losses. Studying the interaction of nematodes and their microbial pathogens is of great importance for the biocontrol of animal and plant parasitic nematodes. In this study, we found that the model nematode Caenorhabditis elegans can recognize its fungal pathogen, the nematophagous fungus Purpureocillium lavendulum, through fungal-produced ethanol. Then the nematode elevated the reactive oxygen species production in the gut to inhibit fungal growth in an ethanol dehydrogenase-dependent manner. With this mechanism, novel biocontrol strategies may be developed targeting the ethanol receptor or metabolic pathway of nematodes. Meanwhile, as a volatile organic compound, ethanol should be taken seriously as a vector molecule in the microbial-host interaction in nature.

Microbiota and functional analyses of nitrogen-fixing bacteria in root-knot nematode parasitism of plants.

BACKGROUND: Root-knot nematodes (RKN) are among the most important root-damaging plant-parasitic nematodes, causing severe crop losses worldwide. The plant rhizosphere and root endosphere contain rich and diverse bacterial communities. However, little is known about how RKN and root bacteria interact to impact parasitism and plant health. Determining the keystone microbial taxa and their functional contributions to plant health and RKN development is important for understanding RKN parasitism and developing efficient biological control strategies in agriculture. RESULTS: The analyses of rhizosphere and root endosphere microbiota of plants with and without RKN showed that host species, developmental stage, ecological niche, and nematode parasitism, as well as most of their interactions, contributed significantly to variations in root-associated microbiota. Compared with healthy tomato plants at different developmental stages, significant enrichments of bacteria belonging to Rhizobiales, Betaproteobacteriales, and Rhodobacterales were observed in the endophytic microbiota of nematode-parasitized root samples. Functional pathways related to bacterial pathogenesis and biological nitrogen fixation were significantly enriched in nematode-parasitized plants. In addition, we observed significant enrichments of the nifH gene and NifH protein, the key gene/enzyme involved in biological nitrogen fixation, within nematode-parasitized roots, consistent with a potential functional contribution of nitrogen-fixing bacteria to nematode parasitism. Data from a further assay showed that soil nitrogen amendment could reduce both endophytic nitrogen-fixing bacteria and RKN prevalence and galling in tomato plants. CONCLUSIONS: Results demonstrated that (1) community variation and assembly of root endophytic microbiota were significantly affected by RKN parasitism; (2) a taxonomic and functional association was found for endophytic nitrogen-fixing bacteria and nematode parasitism; and (3) the change of nitrogen-fixing bacterial communities through the addition of nitrogen fertilizers could affect the occurrence of RKN. Our results provide new insights into interactions among endophytic microbiota, RKN, and plants, contributing to the potential development of novel management strategies against RKN. Video Abstract.

An overview of plutonium isotopes in soils, China: Distribution, spatial patterns, and sources.

Plutonium (Pu) is an anthropogenic radionuclide which has drawn significant attentions due to its radiotoxicity, and the sources of plutonium linked with nuclear accidents and contaminations. The 240Pu/239Pu atom ratio is source dependent and can be used as a fingerprint to determine the sources of radioactive contaminant. However, the distribution and sources of plutonium in soils of China have not yet been systematically studied at a national scale up to date. The distribution, spatial patterns, and sources of plutonium in soils of China were discussed in this work. The concentrations of 239,240Pu are in the range of 0.002-4.824 mBq/g with a large variation, and the 239,240Pu concentrations in surface soils increase with the increasing latitude, which affects by multi-factors such as organic matter and particle size, etc. The inventories of 239,240Pu are in the range of 7.31-554 Bq/m2. The weighted average of 240Pu/239Pu atom ratios (0.180 ± 0.004) in all surface samples is good agreement with the ratio of global fallout (0.180 ± 0.014) of the nuclear weapons tests, this indicate that the major source of plutonium in China is global fallout. However, among some sites, distinctly lower 240Pu/239Pu atom ratio compared to the global fallout values were observed in the northwest China, indicating a significant contribution from other source besides the global fallout. Furthermore, the spatial clustering patterns of hot spots (high values) and cold spots (low values) for plutonium showing the clear associations with nuclear tests, especially the Chinese Lop Nor nuclear weapons tests (CNTs) and the Semipalatinsk nuclear weapons tests (STS). Radioactive material including plutonium from the STS or CNTs was transported by the prevailing westerlies to the northwest China. This review about the fingerprints and distribution of plutonium in soils of China will help researchers to establish a reference database for future radiation risk assessment and environmental radioactive management.

Effects of the Targeted Regulation of CCRK by miR-335-5p on the Proliferation and Tumorigenicity of Human Renal Carcinoma Cells.

Cell cycle-related kinase (CCRK) is most closely related to cyclin-dependent protein kinase, which may activate cyclin-dependent kinase 2 and is associated with the growth of human cancer cells. However, the expression and function of CCRK in the pathogenesis of clear cell renal cell cancer (ccRCC) are unclear. Herein, this research aimed to explore the potential mechanism of the targeted regulation of CCRK by miR-335-5p on the proliferation and tumorigenicity of human ccRCC cells. The results showed that CCRK was significantly overexpressed in ccRCC tissues and cells, and knockdown of the CCRK expression by shRNA inhibited cell proliferation in vitro and in vivo and enhanced cell apoptosis in vitro, which indicated that CCRK could be a potential target for antitumour drugs in the treatment of ccRCC. Moreover, miR-335-5p was found to bind directly to the 3' untranslated region of CCRK, was expressed at markedly low levels in ccRCC cells, and was closely associated with the tumour stage. The overexpression of CCRK partially reversed the inhibitory effects of miR-335-5p on the cell growth of ccRCC, which implied that miR-335-5p could serve as a promising tumour inhibitor for ccRCC. In summary, CCRK could serve as an alternative antitumour drug target, and miR-335-5p could be a promising therapeutic tumour inhibitor for ccRCC treatment.

Survival and infectivity of second-stage root-knot nematode Meloidogyne incognita juveniles depend on lysosome-mediated lipolysis.

Adaptation to nutrient deprivation depends on the activation of metabolic programs to use reserves of energy. When outside a host plant, second-stage juveniles (J2) of the root-knot nematode (Meloidogyne spp.), an important group of pests responsible for severe losses in the production of crops (e.g., rice, wheat, and tomato), are unable to acquire food. Although lipid hydrolysis has been observed in J2 nematodes, its role in fitness and the underlying mechanisms remain unknown. Using RNA-seq analysis, here, we demonstrated that in the absence of host plants, the pathway for the biosynthesis of polyunsaturated fatty acids was upregulated, thereby increasing the production of arachidonic acid in middle-stage J2 Meloidogyne incognita worms. We also found that arachidonic acid upregulated the expression of the transcription factor hlh-30b, which in turn induced lysosomal biogenesis. Lysosomes promoted lipid hydrolysis via a lysosomal lipase, LIPL-1. Furthermore, our data demonstrated that blockage of lysosomal lipolysis reduced both lifespan and locomotion of J2 worms. Strikingly, disturbance of lysosomal lipolysis resulted in a decline in infectivity of these juveniles on tomato roots. Our findings not only reveal the molecular mechanism of lipolysis in J2 worms but also suggest potential novel strategies for the management of root-knot nematode pests.

[Polycyclic Aromatic Hydrocarbons in Surface Soil of China (2000-2020): Temporal and Spatial Distribution, Influencing Factors].

With the rapid development of China's economy and society, the polycyclic aromatic hydrocarbon (PAH) pollution of surface soil has attracted increasing attention. Based on a systematic review, this study identified 166 relevant papers (published from 2000 to 2020) dealing with the contamination of 16 PAHs in the surface soil of China and summarized the pollution level, temporal, and spatial distribution influencing factors of PAHs with statistics, spatial interpolation analysis, and source analysis methods. The results showed that the surface soil of China has been polluted by human-caused PAHs, with a median concentration of 675.70 µg·kg-1. Although the overall condition is good, some sampling points have been seriously polluted. Among the monomers of PAHs, the concentrations of fluoranthene (Fla) and pyrene (Pyr) are high, while acenaphthylene (Acy) and acenaphthene (Ace) are relatively low. During the survey period, the concentration data of surface soil PAHs are generally within the moderate pollution levels of 313.10-1070.45 µg·kg-1, while the annual changes of PAHs do not show obvious fluctuations and are less affected by oil production and consumption. Statistics and spatial interpolation results show that PAH pollution in the surface soil of China has regional characteristics, where the concentration decreases in order from northwest, north, east, northeast, southwest, and south-central China. The pollution level in most provinces is "contaminated" or "weakly contaminated." From the source analysis results, PAH pollution in surface soils in most areas of China comes from the high-temperature combustion of fossil fuels such as petroleum, biomass, and coal. Heilongjiang and some northwestern regions (e.g., Xinjiang and Tibet) were mainly represented by oil source pollution. Such results could provide a reference for soil environmental management and PAH pollution control in China.

Review of hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) contamination in Chinese soils.

Despite a ban on the production and use of organochlorine pesticides (OCPs) after 1983, serious OCP pollution still exists in the soil in certain areas of China because OCPs degrade very slowly. Based on a systematic review, we identified 136 relevant papers focusing on soil contamination from hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) in China (published from 2001 to 2019). We compiled scientific data, extracted and analyzed relevant information, and summarized the pollution characteristics of HCH and DDT in Chinese soils found in two land use types: agricultural land and land for construction. Related studies on HCH and DDT in Chinese soils focus on the Beijing-Tianjin-Hebei region and the Yangtze and Pearl River Deltas, where agricultural soils are predominant. The average concentrations of both HCH and DDT in agricultural soils were generally lower than the risk screening value (100 µg/kg) in most provinces in China, except for DDT concentrations in the Inner Mongolia autonomous region. However, in certain central and eastern regions, mean or maximum recorded DDT concentrations approaching or exceeding 100 µg/kg were recorded. Regarding land for construction, soils with excessive concentrations of HCH and DDT were primarily observed at sites of operational or defunct pesticide factories. According to isomer and metabolite compositions, HCH and DDT at most sites originated from historical residues, but others may have been new inputs after 1983. Since 2015, the concentrations of HCH and DDT in agricultural soils in China have been decreasing, and those in the soils of land for construction (except for sites of operational or defunct pesticide factories) have not exceeded the standard after 2005. This indicates that the measures to prohibit the production and use of OCPs in China have been effective. However, the management of operational or defunct pesticide factories polluted by OCPs requires further improvement.

Immobilization of Cr(VI) in Soil Using a Montmorillonite-Supported Carboxymethyl Cellulose-Stabilized Iron Sulfide Composite: Effectiveness and Biotoxicity Assessment.

A novel composite of montmorillonite-supported carboxymethyl cellulose-stabilized nanoscale iron sulfide (CMC@MMT-FeS), prepared using the co-precipitation method, was applied to remediate hexavalent chromium (Cr(VI))-contaminated soil. Cr(VI)-removal capacity increased with increasing FeS-particle loading. We tested the efficacy of CMC@MMT-FeS at three concentrations of FeS: 0.2, 0.5, and 1 mmol/g, hereafter referred to as 0.2 CMC@MMT-FeS, 0.5 CMC@MMT-FeS, and 1.0 CMC@MMT-FeS, respectively. The soil Cr(VI) concentration decreased by 90.7% (from an initial concentration of 424.6 mg/kg to 39.4 mg/kg) after 30 days, following addition of 5% (composite-soil mass proportion) 1.0 CMC@MMT-FeS. When 2% 0.5 CMC@MMT-FeS was added to Cr(VI)-contaminated soil, the Cr(VI) removal efficiency, as measured in the leaching solution using the toxicity characteristic leaching procedure, was 90.3%, meeting the environmental protection standard for hazardous waste (5 mg/kg). The European Community Bureau of Reference (BCR) test confirmed that the main Cr fractions in the soil samples changed from acid-exchangeable fractions to oxidable fractions and residual fractions after 30 days of soil remediation by the composite. Moreover, the main complex formed during remediation was Fe(III)-Cr(III), based on BCR and X-ray photoelectron spectroscopy analyses. Biotoxicity of the remediated soils, using Vicia faba and Eisenia foetida, was analyzed and evaluated. Our results indicate that CMC@MMT-FeS effectively immobilizes Cr(VI), with widespread potential application in Cr(VI)-contaminated soil remediation.

Nuclear receptor nhr-48 is required for pathogenicity of the second stage (J2) of the plant parasite Meloidogyne incognita.

Nuclear receptors (NRs) are a diverse class of transcription factors, which are involved in regulating a large number of physiological events in metazoans. However, the function of NRs is poorly understood in plant-parasitic nematodes. Here, members of the NR1J+K group of NRs in nematodes, including the free-living and plant parasites, were examined and phylogenetically analyzed. We found that the number of members of the NR1J+K group in plant-parasitic nematodes was less than that in the free-living nematodes, suggesting this reduction of NR1J+K group members in plant parasites maybe arose during the separation of the free-living and intermediately plant parasitic nematodes (Bursaphelenchus xylophilus). Interestingly, the DNA-binding domain (DBD) and ligand-binding domain (LBD) of NR1J+K members were separated into two gene locations in the plant parasites. Knockdown of Meloidogyne incognita WBMinc13296, the ortholog of Caenorhabditis elegans nhr-48 DBD, reduced infectivity, delayed development, and decreased reproductivity. J2 of M. incognita subjected to silencing of WBMinc13295, the orthologs of B. xylophilus nhr-48 LBD, exhibited developmental lag within the host and reduced reproductivity. This study provides new insights into the function of NRs and suggests that NRs are potential targets for developing effective strategies for biological control of plant-parasitic nematodes.

Cystic adventitial disease of the common femoral vein: A case report.

Adventitial cystic disease (ACD) of the common femoral vein is a rare vascular disorder. It becomes more difficult to recognize preoperatively especially when the femoral vein is affected. We report the case of a 62-year-old female patient who presented with a one-month history of painless swelling in her right lower extremity. She had no specific past medical history and no history of trauma, and had a full coagulopathy profile that was negative for any hypercoagulable syndrome. On examination, her lower right leg was significantly swollen with a palpable mass in her right inguinal region. A computerized tomography (CT) with contrast was performed to provide more information and revealed an eccentric compression over the medial wall of the right common femoral vein. During surgical exploration, adventitial cystic mucinous disease was enucleated and the patient underwent femoral exploration, excision of the cysts and reconstruction of iliac femoral vein graft using an artificial blood vessel. The pathological examination confirmed the diagnosis. The patient continued to do well, and she had an unremarkable venous duplex evaluation at her 6-month follow-up. The presentation, investigation, treatment, and pathology of this condition are discussed with a literature review.

Associated bacteria of different life stages of Meloidogyne incognita using pyrosequencing-based analysis.

The root knot nematode (RKN), Meloidogyne incognita, belongs to the most damaging plant pathogens worldwide, and is able to infect almost all cultivated plants, like tomato. Recent research supports the hypothesis that bacteria often associated with plant-parasitic nematodes, function as nematode parasites, symbionts, or commensal organisms etc. In this study, we explored the bacterial consortia associated with M. incognita at different developmental stages, including egg mass, adult female and second-stage juvenile using the pyrosequencing approach. The results showed that Proteobacteria, with a proportion of 71-84%, is the most abundant phylum associated with M. incognita in infected tomato roots, followed by Actinobacteria, Bacteroidetes, Firmicutes etc. Egg mass, female and second-stage juvenile of M. incognita harbored a core microbiome with minor difference in communities and diversities. Several bacteria genera identified in M. incognita are recognized cellulosic microorganisms, pathogenic bacteria, nitrogen-fixing bacteria and antagonists to M. incognita. Some genera previously identified in other plant-parasitic nematodes were also found in tomato RKNs. The potential biological control microorganisms, including the known bacterial pathogens and nematode antagonists, such as Actinomycetes and Pseudomonas, showed the largest diversity and proportion in egg mass, and dramatically decreased in second-stage juvenile and female of M. incognita. This is the first comprehensive report of bacterial flora associated with the RKN identified by pyrosequencing-based analysis. The results provide valuable information for understanding nematode-microbiota interactions and may be helpful in the development of novel nematode-control strategies.