Dominant plant species shift their nitrogen uptake patterns in response to nutrient enrichment caused by a fungal fairy in an alpine meadow

Niche partitioning by time, space and chemical forms has been suggested as an important mechanism to maintain species coexistence. Climate warming is assumed to increase soil nutrient availability through enhancing mineralization of soil organic matter in a variety of terrestrial ecosystems. However, few studies have yet examined how dominant plant species contribute to species coexistence when nutrient enrichment occurs in native ecosystems. We studied a single fairy ring (5 m diameter) in a Kobresia meadow in the Tibetan Plateau. This kind of rings is caused by a basidiomycete fungus Agaricus campestris, and is evidenced by dark-green vegetation boundaries. Nutrient enrichment occurs due to enhanced decomposition of soil organic matter (SOM) in the fungus growth zone of these rings. We conducted a short-term ¹⁵N labelling experiment and found that dominant plant species shifted their N uptake patterns and preferred N form (NO ₃ ^? , NH ₄ ⁺ , and amino acid N) in response to nutrient enrichment in an N-limited alpine meadow. The legume Gueldenstaedtia diversifolia had the lowest aboveground biomass among the five plant species studied at low available N level, although it mainly utilized ammonium (the most abundant N form). The two graminoids (Elymus nutans and Stipa aliena) demonstrated similar aboveground biomass at low and high available N levels, showing a similar pattern switching from NH ₄ ⁺ /NO ₃ ^? uptake outside the ring to glycine uptake in the annulus zone of the ring. The biomass of the forb Gentiana straminea differed significantly at low and high available N levels, but its N uptake pattern almost remained unchanged. Species therefore differed in their response to nutrient enrichment, most species showing chemical niche shifts instead of niche conservatism. This finding has important implications with regard to understanding the mechanisms responsible for species coexistence when natural nutrient enrichment is induced by climate warming in terrestrial ecosystems.     

Detection, isolation, and characterization of acidophilic methanotrophs from Sphagnum mosses

Sphagnum peatlands are important ecosystems in the methane cycle. Methane-oxidizing bacteria in these ecosystems serve as a methane filter and limit methane emissions. Yet little is known about the diversity and identity of the methanotrophs present in and on Sphagnum mosses of peatlands, and only a few isolates are known. The methanotrophic community in Sphagnum mosses, originating from a Dutch peat bog, was investigated using a pmoA microarray. A high biodiversity of both gamma- and alphaproteobacterial methanotrophs was found. With Sphagnum mosses as the inoculum, alpha- and gammaproteobacterial acidophilic methanotrophs were isolated using established and newly designed media. The 16S rRNA, pmoA, pxmA, and mmoX gene sequences showed that the alphaproteobacterial isolates belonged to the Methylocystis and Methylosinus genera. The Methylosinus species isolated are the first acid-tolerant members of this genus. Of the acidophilic gammaproteobacterial strains isolated, strain M5 was affiliated with the Methylomonas genus, and the other strain, M200, may represent a novel genus, most closely related to the genera Methylosoma and Methylovulum. So far, no acidophilic or acid-tolerant methanotrophs in the Gammaproteobacteria class are known. All strains showed the typical features of either type I or II methanotrophs and are, to the best of our knowledge, the first isolated (acidophilic or acid-tolerant) methanotrophs from Sphagnum mosses.     

On structural damage incurred by bacteria upon exposure to hydrophobic polycationic coatings

Hydrophobic polycations previously developed by us efficiently kill E. coli and Staphylococcus aureus on contact. As visualized by electron microscopy herein, these pathogenic bacteria incur marked morphological damage from the exposure to these N-alkylated-polyethylenimine “paints” which results in the leakage of an appreciable fraction of the total cellular protein. The quantity and composition of that leaked protein is similar to that released upon traditional lysozyme/EDTA treatment, thus providing insights into the mechanism of action of our microbicidal coatings.     

Effects of transgenic Bt cotton on overwintering characteristics and survival of Helicoverpa armigera

The effects of transgenic Bt cotton on the overwintering generation of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), are unknown. We hypothesized that a Bt cotton diet may adversely affect fitness of this generation and examined fresh weight, lipids, glycogens, low-molecular-weight sugars and SCPs (supercooling points) of pupae, as well as survival of larvae, diapausing pupae and adult emergence in comparison with controls. Field and laboratory experiments showed that larvae fed on Bt cotton had a decreased pupation rate, and fewer entered diapause and emerged as adults compared with larvae fed non-Bt cotton. Furthermore, larvae fed Bt cotton had reduced pupal weight, glycogen content and trehalose levels both in diapausing and in non-diapausing pupae, and only diapausing pupae had an increased SCP compared to controls. The SCPs of diapausing pupae reared on Bt cotton were significantly higher than those reared on non-Bt cotton. The trehalose levels of diapausing pupae reared on Bt cotton were significantly lower than those of larvae reared on non-Bt cotton. Thus, these results suggest that a Bt cotton diet weakens the preparedness of cotton bollworm for overwintering and reduces survival of the overwintering generation, which will in turn reduce the density of the first generation in the following year. Effects of transgenic Bt cotton on the overwintering generation of cotton bollworm appear to have significantly contributed to the suppression of cotton bollworm observed throughout northern China in the past decade.     

Metformin activates AMP kinase through inhibition of AMP deaminase

The mechanism for how metformin activates AMPK (AMP-activated kinase) was investigated in isolated skeletal muscle L6 cells. A widely held notion is that inhibition of the mitochondrial respiratory chain is central to the mechanism. We also considered other proposals for metformin action. As metabolic pathway markers, we focused on glucose transport and fatty acid oxidation. We also confirmed metformin actions on other metabolic processes in L6 cells. Metformin stimulated both glucose transport and fatty acid oxidation. The mitochondrial Complex I inhibitor rotenone also stimulated glucose transport but it inhibited fatty acid oxidation, independently of metformin. The peroxynitrite generator 3-morpholinosydnonimine stimulated glucose transport, but inhibited fatty acid oxidation. Addition of the nitric oxide precursor arginine to cells did not affect glucose transport. These studies differentiate metformin from inhibition of mitochondrial respiration and from active nitrogen species. Knockdown of adenylate kinase also failed to affect metformin stimulation of glucose transport. Hence, any means of increase in ADP appears not to be involved in the metformin mechanism. Knockdown of LKB1, an upstream kinase and AMPK activator, did not affect metformin action. Having ruled out existing proposals, we suggest a new one: metformin might increase AMP through inhibition of AMP deaminase (AMPD). We found that metformin inhibited purified AMP deaminase activity. Furthermore, a known inhibitor of AMPD stimulated glucose uptake and fatty acid oxidation. Both metformin and the AMPD inhibitor suppressed ammonia accumulation by the cells. Knockdown of AMPD obviated metformin stimulation of glucose transport. We conclude that AMPD inhibition is the mechanism of metformin action.     

Long-term intraperitoneal injection of lipopolysaccharide induces high expression of Id2 in the brain of mice

Lipopolysaccharide (LPS) from gram negative bacteria plays an important role in the pathophysiology of neurodegenerative diseases. Many evidences showed that LPS-induced neuroinflammation is related to upregulation of NF-kappaB. Here, we report that long-term treatment of lower dosage LPS mainly causes upregulation of Id2 protein. As an inhibitor of cell differentiation, Id2 plays an import role in adult olfactory neurogenesis. However, Id2 protein in brain acts as two edges in a sword, persist over-expression of Id2 in brain can induce neurodamages and may be related to neurodegeneration.     

Differentiation of SH-SY5Y cells to a neuronal phenotype changes cellular bioenergetics and the response to oxidative stress

Cell differentiation is associated with changes in metabolism and function. Understanding these changes during differentiation is important in the context of stem cell research, cancer, and neurodegenerative diseases. An early event in neurodegenerative diseases is the alteration of mitochondrial function and increased oxidative stress. Studies using both undifferentiated and differentiated SH-SY5Y neuroblastoma cells have shown distinct responses to cellular stressors; however, the mechanisms remain unclear. We hypothesized that because the regulation of glycolysis and oxidative phosphorylation is modulated during cellular differentiation, this would change bioenergetic function and the response to oxidative stress. To test this, we used retinoic acid (RA) to induce differentiation of SH-SY5Y cells and assessed changes in cellular bioenergetics using extracellular flux analysis. After exposure to RA, the SH-SY5Y cells had an increased mitochondrial membrane potential, without changing mitochondrial number. Differentiated cells exhibited greater stimulation of mitochondrial respiration with uncoupling and an increased bioenergetic reserve capacity. The increased reserve capacity in the differentiated cells was suppressed by the inhibitor of glycolysis 2-deoxy-d-glucose. Furthermore, we found that differentiated cells were substantially more resistant to cytotoxicity and mitochondrial dysfunction induced by the reactive lipid species 4-hydroxynonenal or the reactive oxygen species generator 2,3-dimethoxy-1,4-naphthoquinone. We then analyzed the levels of selected mitochondrial proteins and found an increase in complex IV subunits, which we propose contributes to the increase in reserve capacity in the differentiated cells. Furthermore, we found an increase in MnSOD that could, at least in part, account for the increased resistance to oxidative stress. Our findings suggest that profound changes in mitochondrial metabolism and antioxidant defenses occur upon differentiation of neuroblastoma cells to a neuron-like phenotype.     

4-alkoxy-3-arylfuran-2(5H)-ones as inhibitors of tyrosyl-tRNA synthetase: synthesis, molecular docking and antibacterial evaluation

A series of novel 4-alkoxy-3-arylfuran-2(5H)-ones as tyrosyl-tRNA synthetase inhibitors were synthesized. Of these compounds, 3-(4-hydroxyphenyl)-4-(2-morpholinoethoxy)furan-2(5H)-one (27) was the most potent. The binding model and structure-activity relationship indicate that replacement of morpholine-ring in the side chain of 27 with a substituent containing more hydrophilic groups would be more suitable for further modification. Antibacterial assay revealed that the synthetic compounds are effective against growth of Gram-positive organisms, and 27 is the most potent agent against Staphylococcus aureus ATCC 25923 with MIC(50) value of 0.23 μg/mL.     

协青早B//协青早B/东乡野生稻BC1F9群体低磷耐性鉴定及其生理机制

通过水培法对协青早B∥协青早B/东乡野生稻BC1F9群体221个株系低磷耐性进行了鉴定,测定了株高、叶龄、黄叶数、地上部干物质量等形态指标及丙二醛(MDA)、可溶性糖和地上部磷含量等生理指标,计算了磷效率,并对各指标间相关性进行了分析.结果表明:221个株系的7个指标均显示出差异性,耐性株系在低磷胁迫下表现为相对叶龄、相对株高、相对地上部干物质量和相对可溶性糖含量较高,相对黄叶数和相对MDA含量较低,相对地上部磷含量差异不明显;磷效率与磷利用效率和磷吸收效率均呈正相关,其中磷利用效率与磷效率达到极显著水平(P＜0.01),表明东乡野生稻回交重组自交系中耐性株系低磷耐性原因主要是具有高磷利用效率,即其单位吸磷量干物质合成力较高.     

海南岛生物多样性保护优先区评价与系统保护规划

选择海南岛140个濒危物种为指示物种,在物种栖息地评价的基础上,利用系统保护规划工具MARXAN模型进行迭代运算,提出了海南岛生物多样性保护优先区域,并对保护优先区进行评价.结果表明:海南岛保护优先区面积5383.7km2,占海南岛陆地面积的15.6%,集中分布于鹦哥岭、尖峰岭、五指山等林区和北部湿地;在保护优先区中,11个I级指示物种栖息地的保护比例均超过各自栖息地总面积的65%.通过对保护优先区与现有自然保护区的空缺分析,建议扩充尖峰岭保护区群、鹦哥岭-黎母山保护区群、五指山-吊罗山保护区群;新建抱龙林场-林鼻岭-福万岭保护体系;在海南岛北部建立以水源保护为主,同时兼顾珍稀物种保护的水源地保护带.