黄土高原植被演替对土壤碳库及δ~(13)C的影响

采集宁夏云雾山草原植被演替阶段的土壤和植物样品,测定土壤容重(BD)、土壤含水量(WC)、土壤有机碳(SOC)含量、以及土壤和植物优势种稳定碳同位素组成(δ13C),并比较了它们之间的差异,分析其反映的环境信息。结果表明:在表层0~10 cm深度,灌木地SOC含量为71.7 g·kg-1,显著高于草地的54.6 g·kg-1;灌木地0~20 cm深度SOC含量占1 m深SOC含量的58.1%,而草地在0~40 cm深度的SOC含量占1 m深的34.1%;短期植被演替(约10 a)对土壤剖面0~20 cm层的δ13C值有显著影响,其中对0~10 cm层δ13C影响最大;草地演替为灌木地后δ13C偏负1.4‰,30 cm以下土壤δ13C值对短期植被变化不敏感;通过δ13C在C3植被的短期演替过程中的响应关系发现,δ13C值作为土壤碳库更替和碳循环的研究工具有很好的辨识力;灌木的δ13C值从叶子到根系存在明显差异,逐渐偏正,变化为2.2‰,草地为1.9‰;通过对0~40 cm深度植物根系δ13C值的测定发现,灌木地由表层的-28.15‰变为-26.11‰,偏正了2.04‰,草地根系δ13C值从表层的-27.08‰变为-27.57‰,偏负了0.49‰。     

Human p38δ MAP kinase mediates UV irradiation induced up-regulation of the gene expression of chemokine BRAK/CXCL14

The mitogen-activated protein kinase (MAPK) family comprises ERK, JNK, p38 and ERK5 (big-MAPK, BMK1). UV irradiation of squamous cell carcinoma cells induced up-regulation of gene expression of chemokine BRAK/CXCL14, stimulated p38 phosphorylation, and down-regulated the phosphorylation of ERK. Human p38 MAPKs exist in 4 isoforms: p38α, β, γ and δ. The UV stimulation of p38 phosphorylation was not inhibited by the presence of SB203580 or PD169316, inhibitors of p38α and β, suggesting p38 phosphorylation was not dependent on these 2 isoforms and that p38γ and/or δ was responsible for the phosphorylation. In fact, inhibition of each of these 4 p38 isoforms by the introduction of short hairpin (sh) RNAs for respective isoforms revealed that only shRNA for p38δ attenuated the UV-induced up-regulation of BRAK/CXCL14 gene expression. In addition, over-expression of p38 isoforms in the cells showed the association of p38δ with ERK1 and 2, concomitant with down-regulation of ERK phosphorylation. The usage of p38δ isoform by UV irradiation is not merely due to the abundance of this p38 isoform in the cells. Because serum deprivation of the cells also induced an increase in BRAK/CXCL14 gene expression, and in this case p38α and/or β isoform is responsible for up-regulation of BRAK/CXCL14 gene expression. Taken together, the data indicate that the respective stress-dependent action of p38 isoforms is responsible for the up-regulation of the gene expression of the chemokine BRAK/CXCL14.     

Nitrogen deposition and drought events have non-additive effects on plant growth – Evidence from greenhouse experiments

Climate change and nitrogen deposition affect biodiversity and ecosystem functioning, but interactive effects of these global change drivers are poorly understood. We analysed single and interactive effects of nitrogen (N) fertilisation and drought on the growth performance of Calluna vulgaris. We measured biomass production and allocation, tissue nutrient (N, phosphorus (P) and carbon (C)) concentrations, N allocation patterns (using ¹⁵N tracer) and plant's water status (using δ ¹³C signatures) as response variables in a 2-year greenhouse experiment. N fertilisation increased biomass production and biomass shoot:root ratios. ¹⁵N allocation patterns indicated an increasing aboveground N allocation following N fertilisation. Tissue δ ¹³C signatures were higher in N-fertilised plants. Plant responses to drought were weak. We found strong antagonistic interaction effects of N fertilisation and drought for biomass production. δ ¹³C values peaked when N-fertilised plants were subjected to drought, indicating that N fertilisation increased the evaporative demands of Calluna plants, likely due to increased biomass shoot:root ratios, which in turn resulted in higher drought susceptibility. As an important consequence, even slight drought events may weaken the competitiveness of Calluna when interacting with enhanced airborne N loads. Single-factor studies, thus, need to be complemented by multi-factor analyses to assess conceivable impacts of co-occurring global change drivers.     

Location and motion of free cholesterol molecules in high density lipoprotein

Human high density lipoprotein (HDL₃) was reconstituted with the free cholesterol molecules replaced with 4-[¹³C]-cholesterol. 90 MHz [¹³C]-NMR spectra were obtained and two cholesterol resonances at chemical shifts of 41.73 and 42.20 ppm could be resolved. The former signal arises from the C-4 atom of cholesterol molecules associated with phospholipids and located in the surface of the HDL₃ particle while the latter resonance is due to cholesterol molecules associated with cholesterol ester and triglyceride molecules in the core. HDL₃ reconstituted without any cholesterol ester or triglyceride gave a single resonance at 41.73 ppm indicating that all the free cholesterol molecules are in the surface. 60% of the free cholesterol molecules present in normal HDL₃ are in the phospholipid monolayer around the surface where they undergo relatively restricted motion compared to the remaining 40% situated in the liquid core. The free cholesterol molecules can equilibrate between the two pools in the timescale 10ms–700s.     

Isolation and expression analysis of proline metabolism-related genes in Chrysanthemum lavandulifolium

Proline plays a significant role in plant resistance to abiotic stresses, and its level is determined by a combination of synthesis, catabolism and transport. The primary proteins involved are Δ¹-pyrroline-5-carboxylate synthetase (P5CS), proline dehydrogenase (PDH) and proline transporter (ProT). To utilise proline metabolism to improve the stress resistance of Chrysanthemum × morifolium, we isolated two P5CS-homologous genes (ClP5CS1 and ClP5CS2), one PDH gene (ClPDH) and four ProT-homologous genes (ClProT1-4) (GenBANK accession numbers: KF743136–KF743142) from Chrysanthemum lavandulifolium, which is closely related to chrysanthemums and exhibits strong resistance to stresses. Expression analysis of these genes in different organs and under various stresses indicated that ClP5CSs showed substantial constitutive expression, while ClPDH was only strongly expressed in the capitulum and was inhibited under most stresses. The expression patterns of four ClProT genes presented characteristics of organ specificity and disparity under stresses. Above all, the expression of ClProT2 was restricted to above-ground organs, especially strong in the capitulum and could be obviously induced by various stress conditions. Promoters of ClPDH and ClProTs contained many cis-acting regulatory elements involved in stress responses and plant growth and development. High levels of free proline were found in flower buds, the capitulum under the non-stress condition and later periods of stress conditions except cold treatment. Interestingly, organ specificity and disparity also exist in the level of free proline under different stress conditions. Our study indicates that ClProTs play significant roles in proline accumulation and stress responses, and that ClProT2 could be used to genetically modify the stress resistance of chrysanthemums. In addition, proline metabolism might be closely related to plant flowering and floral development.     

Osmoregulation of leaf motor cells

"Osmotic Motors"--the best-documented explanation for plant leaf movements--frequently reside in specialized motor leaf organs, pulvini. The movements result from dissimilar volume and turgor changes in two oppositely positioned parts of the pulvinus. This Osmotic Motor is powered by a plasma membrane proton ATPase, which drives KCl fluxes and, consequently, water, across the pulvinus into swelling cells and out of shrinking cells. Light signals and signals from the endogenous biological clock converge on the channels through which these fluxes occur. These channels and their regulatory pathways in the pulvinus are the topic of this review.     

15N自然丰度法在陆地生态系统氮循环研究中的应用

随着氮沉降的不断增加以及人们对全球变化问题的日益关注, 稳定同位素技术在全球变化研究中得到广泛的应用。因为植物和土壤的氮同位素组成记录了氮循环影响因子的综合作用, 并且具有测量简单以及不受取样时间和空间限制的优点, 所以氮同位素自然丰度法被用于氮循环的研究中。该文从氮循环过程中植物和土壤的氮分馏入手, 总结国内外相关文献, 阐述了植物和土壤氮自然丰度在预测生态系统氮饱和和氮循环长期变化趋势中的应用; 总结了利用树轮δ ¹⁵N法研究氮循环过程中应该注意的事项以及目前尚未解决的问题。     

Low-dimensional compounds containing cyano groups. XIX. Crystal structure, spectroscopic, thermal and magnetic properties of {[Cu(tn)2]3[Pt(CN)4]2}[Pt(CN)4] (tn = 1,3-diaminopropane) complex

Violet prismatic crystals of {[Cu(tn)₂]₃[Pt(CN)₄]₂}[Pt(CN)₄] (tn = 1,3-diaminopropane) were crystallized from the water-methanol solution containing CuCl₂·2H₂O, tn and K₂[Pt(CN)₄]·3H₂O. Prepared complex was characterized using elemental analysis, infrared and UV-Vis spectroscopy, magnetic measurement and thermal analysis. X-ray analysis revealed an ionic character of the complex containing mononuclear square planar [Pt(CN)₄]²⁻ complex anions and penta-nuclear [Cu(tn)₂-Pt(CN)₄-Cu(tn)₂-Pt(CN)₄-Cu(tn)₂]²⁺ complex cations. The inner Cu(II) atom of the complex cation is hexa-coordinated, whereas two crystallographically equivalent peripheral Cu(II) atoms are penta-coordinated in the shape of a deformed square pyramid. Four v(CN) absorption bands observed in the IR spectrum are in agreement with the higher number of crystallographically different cyano groups and a broad highly asymmetric band observed in the reflectance UV-Vis spectrum is consistent with the presence of both hexa- and penta-coordinated Cu(II) atoms in the structure. The temperature dependence of the inverse susceptibility suggests the presence of a weak antiferromagnetic exchange coupling between Cu(II) ions. The complex is stable up to 210 °C when its two-stage thermal decomposition starts.     

Cardio-protective determinants are conserved in aged human myocardium after ischemic preconditioning

Ischemic preconditioning (IPrec) improves post-ischemic dysfunctions of the myocardium along with activation of protein kinase C isozymes including PKCdelta. Moreover, expression of cardio-protective determinants can reduce ischemic damages. Because IPrec is limited in aged hearts, we assessed in an experimental model the impact of aging on PKCdelta and selected protective proteins in the preconditioned myocardium from adult (< or =55) and older (> or =70 years) humans. Adult myocardium showed PKCdelta up-regulation after IPrec along with improved post-ischemic contractility. Although there was no functional benefit, PKCdelta increased in older myocardium as well. Subsequent mRNA analyses demonstrated that IPrec stabilizes the mRNA expression of protective proteins (Hsp70, Bcl-2/-xL, IAPs) in both aging groups. Moreover, older hearts revealed increase in post-ischemic Hsp90beta. Our study indicates, that IPrec conserves the expression of cardio-protective determinants in aged hearts despite limited functional recovery.