No abstract

Exploration of structurally novel natural products greatly facilitates the discovery of biologically active pharmacophores that are biologically validated starting points for the development of new drugs. Endophytes that colonize the internal tissues of plant species, have been proven to produce a large number of structurally diverse secondary metabolites. These molecules exhibit remarkable biological activities, including antimicrobial, anticancer, anti-inflammatory and antiviral properties, to name but a few. This review surveys the structurally diverse natural products with new carbon skeletons, unusual ring systems, or rare structural moieties that have been isolated from endophytes between 1996 and 2016. It covers their structures and bioactivities. Biosynthesis and/or total syntheses of some important compounds are also highlighted. Some novel secondary metabolites with marked biological activities might deserve more attention from chemists and biologists in further studies.

Hypoxia is a classic characteristic of the tumor microenvironment with a significant impact on cancer progression and therapeutic response. Hypoxia-inducible factor-1 alpha (HIF-1α), the most important transcriptional regulator in the response to hypoxia, has been demonstrated to significantly modulate hypoxic gene expression and signaling transduction networks. In past few decades, growing numbers of studies have revealed the importance of noncoding RNAs (ncRNAs) in hypoxic tumor regions. These hypoxia-responsive ncRNAs (HRNs) play pivotal roles in regulating hypoxic gene expression at the transcriptional, posttranscriptional, translational and posttranslational levels. In addition, as a significant gene expression regulator, ncRNAs exhibit promising roles in regulating HIF-1α expression at multiple levels. In this review, we briefly elucidate the reciprocal regulation between HIF-1α and ncRNAs, as well as their effect on cancer cell behaviors. We also try to summarize the complex feedback loop existing between these two components. Moreover, we evaluated the biomarker potential of HRNs for the diagnosis and prognosis of cancer, as well as the potential clinical utility of shared regulatory mechanisms between HIF-1α and ncRNAs in cancer treatment, providing novel insights into tumorigenicity, which may lead to innovative clinical applications.

It is increasingly evident that soil microorganisms play a substantial role in ecosystem processes, which occupy a large part of genetic diversity in terrestrial ecosystems. During the past decades, nitrogen (N) addition induced by human has been regarded as the main driver of global changes to soil microecological processes. Although growing studies demonstrated the loss of biodiversity due to N addition in regional scale, the role of global N addition on soil microbial diversity is lacking. Here, we sought to illuminate the impacts and driving factors of soil microbial diversity in relation to global N addition using a meta‐analysis from 1,078 paired observations in 212 studies. We found a negative influence of global N addition on soil microbial diversity, and the reduction of soil microbial diversity was determined by land use types, N fertility types, methods, N addition rates, and duration. In fact, there was a linear decrease of soil microbial diversity along the latitudinal gradient, and N addition‐induced acidification was the predominant contributor to the reduction of soil microbial diversity. Both of soil properties (pH, soil organic carbon, soil total N, and soil microbial biomass C) and climatic factors (mean annual temperature and mean annual precipitation) determined soil microbial diversity under global N addition. It was noted that soil fungal diversity was more adaptable to acidic environments, whereas soil bacterial diversity was more adaptable to neutral environment. Most importantly, soil fungal diversity was more sensitive than soil bacterial diversity under global N addition. Our meta‐analysis provides a new insight in understanding the key role of global N addition in shaping soil microbial diversity. Thereby, we recommend that future research should be focused on the soil microbial processes using manipulative controlled experiments, which identify the available measures to reduce the loss of soil microbial diversity globally.

No abstract

No abstract

We examined foliar nitrogen (N) and phosphorus (P) stoichiometry of 3 wetland plants (Phalaris arundinacea, Miscanthus sacchariflorus, and Carex brevicuspis) distributed along an elevation gradient in the Dongting Lake, China, and how this stoichiometry is related to soil physico-chemical characteristics, elevation, and flooding days. Plant and soil samples were collected from 3 lakeshore sites. Total N and P concentrations of plants and six physico-chemical characteristics of the soil were measured, in addition to the elevation and flooding days. P. arundinacea and M. sacchariflorus had higher total N and P concentrations than C. brevicuspis. The foliar N:P ratio decreased with increasing elevation, and only increased with increasing foliar total N concentration. Canonical correspondence analysis indicated that the foliar stoichiometry was primarily regulated by soil water content, followed by soil nutrient concentration. The foliar N and P stoichiometry of the 3 wetland plants was insignificantly correlated with soil total P concentration. However, foliar stoichiometric characteristics and soil total N concentration significantly differed among the 3 species. These results demonstrate that spatial variation of foliar stoichiometry in wetland plants exists along an elevation gradient, with this information being useful for the conservation and management of wetland plants in this lake.

Ca(II) complexes with poly(ethylene glycol) (PEG), poly(N-vinyl-2-pyrrolidone) (PVP) and poly(vinyl alcohol)(PVA) were formed in aqueous solutions. The Ca(II) complexes were used as Ca precursors to react with sodium phosphates to prepare amorphous calcium phosphate (ACP). The experimental results showed that ACP precipitates could be formed in the presence of PVA or PEG while only crystalline calcium phosphate precipitates (hydroxyapatite) was formed in the presence of PVP. When Ca ions were coordinated with PEG, the viscosity of the system was not obviously influenced, which was appropriate to separate the precipitates. Hence, PEG is considered to be an optimal polymeric complexing agent to prepare ACP. The Ca(II) complexes with the polymeric complexing agents can favour ACP formation, which is attributed to the coordinated polymeric complexing agents remaining in the structure of ACP, i.e. in aggregated Ca 9 (PO 4 ) 6 clusters. The existence of the coordinated complexing agents depresses the conversion process from ACP to crystalline hydroxyapatite, hence, ACP can survive in the mother solution.MST/6205