Priming effects of nZVI on carbon sequestration and iron uptake are positively mediated by AM fungus in semiarid agricultural soils.

We investigated the priming effect of nanoscale zero-valent iron (nZVI) on carbon sink and iron uptake, and the possible mediation by AMF (arbuscular mycorrhizal fungi, Funneliformis mosseae) in semiarid agricultural soils. Maize seed dressings comprised of three nZVI concentrations of 0, 1, 2 g·kg-1 and was tested with and without AMF inoculation under high and low soil moistures, respectively. The ICP-OES observations indicated that both low dose of nZVI (1 g·kg-1) and high dose of nZVI (2 g·kg-1) significantly increased the iron concentrations in roots (L: 54.5-109.8 %; H: 119.1-245.4 %) and shoots (L: 40.8-78.9 %; H: 81.1-99.4 %). Importantly, the absorption and translocation rate of iron were substantially improved by AMF inoculation under the low-dose nZVI. Yet, the excess nanoparticles as a stress were efficiently relieved by rhizosphere hyphae, and the iron concentration in leaves and stems can maintain as high as about 300 mg·kg-1 while the iron translocation efficiency was reduced. Moreover, next-generation sequencing confirmed that appropriate amount of nZVI clearly improved the rhizosphere colonization of Funneliformis mosseae (p < 0.001) and the development of soil fungal community. Soil observations further showed that the hyphae development and GRSP (glomalin-related soil protein) secretion were significantly promoted (p < 0.05), with the increased R0.25 (< 0.25 mm) by 35.97-41.16 %. As a return, AMF and host plant turned to input more organic matter into soils for microbial growth and Fe uptake, and such interactions became more pronounced under drought stress. In contrast, high dose of nZVI (2 g·kg-1) tended to agglomerate on the surface of hyphae and spores, causing severe deformation and inactivation of AMF symbionts. Therefore, the priming effects of nZVI on carbon sequestration and Fe uptake in agricultural soils were positively mediated by AMF via the feedback loop of the plant-soil-microbe system for enhanced adaptation to global climate change.

Transition in plant-plant facilitation in response to soil water and phosphorus availability in a legume-cereal intercropping system.

BACKGROUND: The tradeoff between negative and positive interactions of facilitated species and facilitators may depend on the degree of resource availability in agroecosystems. However, the rhizospheric mechanisms driving trade-offs that occur along phosphorus (P) and water availability gradients have not yet been systematically clarified. We established three types of root isolation conditions (no barrier, nylon barrier and solid barrier) at different P and water addition levels to address the above issue in a maize-grass pea intercropping system. RESULTS: The total yield and biomass net effect (NE) and the relative interaction index (RII) were significantly higher than 0 under all environmental conditions, demonstrating that plant-plant interactions generated positive effects in the intercropping system. The maize yield and biomass RII were 0.029-0.095 and 0.018-0.066, respectively, which indicated that maize growth was constantly facilitated. However, the RII for grass pea yield and biomass exhibited a different trend in comparison with maize. It was higher than 0 (as the facilitated species) under low soil P and moisture conditions and transitioned to values lower than 0 (facilitator species) under high P and moisture conditions, which showed that the type and intensity of plant-plant interactions steadily shifted with the applied stressors. Direct interactions decreased the maize rhizospheric soil pH by 1.5% and 1.9% under Low-P conditions. Notably, the rhizospheric soil acid and alkaline phosphatase secretions of maize and grass pea increased by 17.4-27.4% and 15.3-27.7%, respectively, in P-deficient soils. These results show that plant-plant interactions can effectively relieve P stress by mineralizing organophosphorus in P-deficient soils. Furthermore, the above tendency became more pronounced under drought-stressed conditions. The nylon barrier partially restricted the exchange and utilization of available nutrients and decreased the total yield and biomass by 1.8-7.8% and 1.1-7.8%, respectively. The presence of a solid barrier completely restricted interspecific rhizospheric interactions and decreased the total yield and biomass by 2.1-13.8% and 1.6-15.7%, respectively. Phytate and KH2PO4 addition intensified asymmetric interspecific competition, and grass pea was consistently subjected to competitive pressures. CONCLUSION: Briefly, the tradeoff between facilitation and competition was driven by rhizospheric interactions, and the transition in the intensity and type of interaction was highly dependent on resource availability in a biologically diverse system.

Antiviral Activity of Fermented Ginseng Extracts against a Broad Range of Influenza Viruses.

Ginseng products used as herb nutritional supplements are orally consumed and fermented to ginsenoside compounds by the intestinal microbes. In this study, we investigated antiviral protective effects of fermented ginseng extracts against different strains of influenza viruses in genetically diverse mouse models. Intranasal coinoculation of mice with fermented ginseng extract and influenza virus improved survival rates and conferred protection against H1N1, H3N2, H5N1, and H7N9 strains, with the efficacy dependent on the dose of ginseng samples. Antiviral protection by fermented ginseng extract was observed in different genetic backgrounds of mice and in the deficient conditions of key adaptive immune components (CD4, CD8, B cell, MHCII). The mice that survived primary virus inoculation with fermented ginseng extract developed immunity against the secondary infection with homologous and heterosubtypic viruses. In vitro cell culture experiments showed moderate virus neutralizing activity by fermented ginseng extract, probably by inhibiting hemagglutination and neuraminidase activity. This study suggests that fermented ginseng extracts might provide a means to treat influenza disease regardless of virus strains.

Protective effect of ginseng polysaccharides on influenza viral infection.

Ginseng polysaccharide has been known to have multiple immunomodulatory effects. In this study, we investigated whether Panax ginseng polysaccharide (GP) would have a preventive effect on influenza infection. Administration of mice with GP prior to infection was found to confer a survival benefit against infection with H1N1 (A/PR/8/34) and H3N2 (A/Philippines/82) influenza viruses. Mice infected with the 2009 H1N1 virus suspended in GP solution showed moderately enhanced survival rates and lower levels of lung viral titers and the inflammatory cytokine (IL-6). Daily treatment of vaccinated mice with GP improved their survival against heterosubtypic lethal challenge. This study demonstrates the first evidence that GP can be used as a remedy against influenza viral infection.

Cleavage of supercoiled circular double-stranded DNA induced by a eukaryotic cambialistic superoxide dismutase from Cinnamomum camphora.

A eukaryotic cambialistic superoxide dismutase (SOD) has been purified to homogeneity from mature seeds of the disease- and insect-resistant camphor tree (Cinnamomum camphora). Besides the known role of this SOD in protecting cells against oxidative stress, it can induce the cleavage of supercoiled double-stranded DNA into nicked and linear DNA. It can not cleave linear DNA or RNA, demonstrating there is no DNase or RNase in the purified cambialistic SOD. Furthermore, the SOD can linearize circular pGEM-4Z DNA that is relaxed by topoisomerase I. This result indicates that the DNA-cleaving activity requires substrates being topologically constrained. The supercoiled DNA-cleaving activity of the cambialistic SOD can be inhibited by either SOD inhibitor (azide) or catalase and hydroxyl radical scavengers (ethanol and mannitol). The chelator of iron, diethylenetriaminepentaacetic acid (DTPA), also inhibits the supercoiled DNA-cleaving activity. These results show that the dismutation activity is crucial for the supercoiled DNA cleavage. The modification of tryptophan residue of the cambialistic SOD with N-bromosuccinimide (NBS) shows that these two activities are structurally correlative. The reaction mechanism is proposed that the hydroxyl radical formed in a transition-metal-catalyzing Fenton-type reaction contributes to the DNA-cleaving activity. In addition, the cleavage sites in supercoiled pGEM-4Z DNA are random.

Structural studies of an eukaryotic cambialistic superoxide dismutase purified from the mature seeds of camphor tree.

An iron-superoxide dismutase (SOD) was purified and characterized from the mature seeds of camphor tree (Cinnamomum camphora). The ultraviolet and visible absorption spectra of camphor Fe-SOD showed patterns typical of cambialistic Fe-SODs. The inductively coupled plasma assay indicated that there was 0.5-1 atom of Fe(2+) per camphor Fe-SOD subunit. The cDNA of camphor Fe-SOD, including the coding region and the 3' noncoding region, was obtained by reverse transcription polymerase chain reaction using the total RNA from immature seeds of C. camphora as template and then sequenced. The complete amino acid sequence of camphor Fe-SOD was deduced from the cDNA sequence. The correctness of the amino acid sequence was confirmed by directly sequencing five peptide fragments of the enzyme. The molecular mass calculated for the camphor Fe-SOD subunit from its 204 amino acid residues was 22,930.6 Da, The cDNA of camphor Fe-SOD was cloned into the expression vector PMFT7-5 and then expressed in Escherichia coli strain BL21. The reconstructed Fe- or Mn-SOD was purified to homogeneity through column chromatography. Activity of the Fe- or Mn-SOD was found to be almost equal to that of natural camphor Fe-SOD, which is the first cambialistic SOD isolated from eukaryotic cells.