Hierarchical Plant Responses and Diversity Loss after Nitrogen Addition: Testing Three Functionally-Based Hypotheses in the Inner Mongolia Grassland

Numerous studies have shown that nitrogen (N) deposition decreases biodiversity in terrestrial ecosystems. To explain the N-induced species loss, three functionally based hypotheses have been proposed: the aboveground competition hypothesis, the belowground competition hypothesis, and the total competition hypothesis. However, none of them is supported sufficiently by field experiments. A main challenge to testing these hypotheses is to ascertain the role of shoot and root competition in controlling plant responses to N enrichment. Simultaneously examining both aboveground and belowground responses in natural ecosystems is logistically complex, and has rarely been done.In a two-year N addition experiment conducted in a natural grassland ecosystem, we investigated both above- and belowground responses of plants at the individual, species, and community levels. Plants differed significantly in their responses to N addition across the different organizational levels. The community-level species loss was mainly due to the loss of perennial grasses and forbs, while the relative abundance of plant species was dependent mainly on individual-level responses. Plasticity in biomass allocation was much smaller within a species than between species, providing a biological basis for explaining the functionally based species loss. All species increased biomass allocation to aboveground parts, but species with high belowground allocations were replaced by those with high aboveground allocations, indicating that the increased aboveground competition was the key process responsible for the observed diversity loss after N addition in this grassland ecosystem.Our findings shed new light on the validity of the three competing hypotheses concerning species loss in response to N enrichment. They also have important implications for predicting the future impacts of N deposition on the structure and functioning of terrestrial ecosystems. In addition, we have developed a new technique for ascertaining the roles of aboveground and belowground competition in determining plant responses to N fertilization

Mariner mutagenesis of Brucella melitensis reveals genes with previously uncharacterized roles in virulence and survival

BACKGROUND: Random gene inactivation used to identify cellular functions associated with virulence and survival of Brucella spp has relied heavily upon the use of the transposon Tn5 that integrates at G/C base pairs. Transposons of the mariner family do not require species-specific host factors for efficient transposition, integrate nonspecifically at T/A base pairs, and, at a minimum, provide an alternative approach for gene discovery. In this study, plasmid vector pSC189, containing both the hyperactive transposase C9 and transposon terminal inverted repeats flanking a kanamycin resistance gene, were used to deliver Himar1 transposable element into the B. melitensis genome. Conjugation was performed efficiently and rapidly in less than one generation in order to minimize the formation of siblings while assuring the highest level of genome coverage. RESULTS: Although previously identified groups or classes of genes required for virulence and survival were represented in the screen, additional novel identifications were revealed and may be attributable to the difference in insertion sequence biases of the two transposons. Mutants identified using a fluorescence-based macrophage screen were further evaluated using gentamicin-based protection assay in macrophages, survival in the mouse splenic clearance model and growth in vitro to identify mutants with reduced growth rates. CONCLUSION: The identification of novel genes within previously described groups was expected, and nearly two-thirds of the 95 genes had not been previously reported as contributing to survival and virulence using random Tn5-based mutagenesis. The results of this work provide added insight with regard to the regulatory elements, nutritional demands and mechanisms required for efficient intracellular growth and survival of the organism

Simulation of chemical reaction dynamics based on quantum computing

The molecular energies of chemical systems have been successfully calculated on quantum computers, however, more attention has been paid to the dynamic process of chemical reactions in practical application, especially in catalyst design, material synthesis. Due to the limited the capabilities of the noisy intermediate scale quantum (NISQ) devices, directly simulating the reaction dynamics and determining reaction pathway still remain a challenge. Here we develop the ab initio molecular dynamics based on quantum computing to simulate reaction dynamics by extending correlated sampling approach. And, we use this approach to calculate Hessian matrix and evaluate computation resources. We test the performance of our approach by simulating hydrogen exchange reaction and bimolecular nucleophilic substitution SN2 reaction. Our results suggest that it is reliable to characterize the molecular structure, property, and reactivity, which is another important expansion of the application of quantum computingComment: 8 pages, 4 figure

Grazing Alters Ecosystem Functioning and C:N:P Stoichiometry of Grasslands along a Regional Precipitation

Grasslands have experienced dramatic shifts in structure and functioning driven primarily by human disturbances and global climate change. The long-term grazing has resulted in widespread declines in biodiversity and ecosystem functioning and services. This is triggered by the direct and indirect effects of grazing and often mediated by the complex interactions between vegetation and environmental. Thus, it is critical to obtain a better understanding of how grazing, abiotic factors and biotic–abiotic interactions influence key properties of ecosystem functioning and sustainability and thereby provide guideline for improving grassland management practices in the Eurasian steppe. While abundant evidence demonstrates that heavy grazing alters the ecosystem structure and function of grass- lands, research on how grazing specifically affects ecosystem functioning and stoichiometry on broad scales is scarce because of a lack of adequate ungrazed reference sites. We examined the effects of grazing on ecosystem functioning and C:N:P stoichiometry along the 700 km China–Mongolia transect (CMT) using consistent methods. The CMT, which covers a wide range of biotic and abiotic conditions, enables us to observe the total effects of multiple mechanisms that probably operate simultaneously but vary in their relative strengths across regions. The key research questions we are trying to address are: 1) How has grazing affected ecosystem functioning (i.e. species richness, above- and below-ground biomass and litter biomass) and C:N:P stoichiometry of grasslands along the regional precipitation gradient during the last 50 years? 2) How do the responses of plant and soil C, N and P pools and stoichiometry to grazing differ among community types? 3) What is the relative importance of plant functional group (PFG) composition and species plasticity in influencing ecosystem functioning and stoichiometry

Exploring the mechanism of aloe-emodin in the treatment of liver cancer through network pharmacology and cell experiments

Objective: Aloe-emodin (AE) is an anthraquinone compound extracted from the rhizome of the natural plant rhubarb. Initially, it was shown that AE exerts an anti-inflammatory effect. Further studies revealed its antitumor activity against various types of cancer. However, the mechanisms underlying these properties remain unclear. Based on network pharmacology and molecular docking, this study investigated the molecular mechanism of AE in the treatment of hepatocellular carcinoma (HCC), and evaluated its therapeutic effect through in vitro experiments.Methods: CTD, Pharmmapper, SuperPred and TargetNet were the databases to obtain potential drug-related targets. DisGenet, GeneCards, OMIM and TTD were used to identify potential disease-related targets. Intersection genes for drugs and diseases were obtained through the Venn diagram. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of intersecting genes were conducted by the website of Bioinformatics. Intersection genes were introduced into STRING to construct a protein-protein interaction network, while the Cytoscape3.9.1 software was used to visualize and analyze the core targets. AutoDock4.2.6 was utilized to achieve molecular docking between drug and core targets. In vitro experiments investigated the therapeutic effects and related mechanisms of AE.Results: 63 overlapped genes were obtained and GO analysis generated 3,646 entries by these 63 intersecting genes. KEGG analysis mainly involved apoptosis, proteoglycans in cancer, TNF signaling pathway, TP53 signaling pathway, PI3K-AKT signaling pathway, etc. AKT1, EGFR, ESR1, TP53, and SRC have been identified as core targets because the binding energies of them between aloe-emodin were less than -5 kcal/Mol.The mRNA and protein expression, prognosis, mutation status, and immune infiltration related to core targets were further revealed. The involvement of AKT1 and EGFR, as well as the key target of the PI3K-AKT signaling pathway, indicated the importance of this signaling pathway in the treatment of HCC using AE. The results of the Cell Counting Kit-8 assay and flow analysis demonstrated the therapeutic effect of AE. The downregulation of EGFR, PI3KR1, AKT1, and BCL2 in mRNA expression and PI3KR1, AKT,p-AKT in protein expression confirmed our hypothesis.Conclusion: Based on network pharmacology and molecular docking, our study initially showed that AE exerted a therapeutic effect on HCC by modulating multiple signaling pathways. Various analyses confirmed the antiproliferative activity and pro-apoptotic effect of AE on HCC through the PI3K-AKT signaling pathway. This study revealed the therapeutic mechanism of AE in the treatment of HCC through a novel approach, providing a theoretical basis for the clinical application of AE

Chemical Composition, Antimicrobial and Insecticidal Activities of Essential Oils of Discarded Perfume Lemon and Leaves (Citrus Limon (L.) Burm. F.) as Possible Sources of Functional Botanical Agents

Two essential oils were isolated from discarded perfume lemon and leaves (Citrus limon (L.) Burm. F.) by hydro-distillation with good yield (0.044% for perfume lemon and 0.338% for leaves). Their biological activities were evaluated against five selected bacterial strains and Aedes albopictus (Ae. albopictus, Diptera: Culicidae). Chemical composition indicated that both essential oils were rich in essential phytochemicals including hydrocarbons, monoterpenes and sesquiterpene. These constituents revealed some variability among the oils displaying interesting chemotypes (R)-(+)-limonene (12.29–49.63%), citronellal (5.37–78.70%) and citronellol (2.98–7.18%). The biological assessments proved that the two essential oils had similar effect against bacterial (inhibition zones diameter ranging from 7.27 ± 0.06 to 10.37 ± 0.15 mm; MICs and MBCs ranging from 1.6 to 6.4 mg/mL); against Ae. albopictus larvae (LC(50) ranging from 384.81 to 395.09 ppm) and adult mosquito (LD(50) ranging from 133.059 to 218.962 μg/cm(2)); the activity of the two chemotypes ((R)-(+)-limonene and citronellal): larvae (LC(50) ranging from 267.08 to 295.28 ppm), which were all presented in dose-dependent manners. Through this work, we have showcased that recycling and reusing of agriculture by-products, such as discarded perfume lemon and leaves can produce eco-friendly alternatives in bacterial disinfectants and mosquito control product