食用菌厉眼蕈蚊Lycoriella ingenua在温度逆境下的存活率

以食用菌重要害虫-厉眼蕈蚊属的Lycoriella ingenua为研究对象,研究了不同逆境温度下各虫态存活率的差异。结果表明温度对不同虫态存活率的影响存在显著性差异。成虫和蛹对高温具有一定适应性,卵对高温的适应性最低但具有一定的低温耐受力。在35-40℃高温下,相同暴露时间,各虫态的存活率随温度的升高而降低,但成虫的存活率均高于其它虫态。38℃下全部死亡的暴露时间分别为:成虫48 h,蛹24 h,幼虫12 h,卵2h。在40℃达到全部死亡的暴露时间分别为:成虫24 h、蛹12 h、卵和幼虫0.5 h。低温处理下,各虫态随着暴露时间的延长存活率逐渐降低。5℃低温下,相同暴露时间,成虫存活率均高于其它虫态,但在0℃低温下暴露24 h后全部死亡,显著高于其它虫态;幼虫在低温下取食活动减弱,5℃下暴露24 h后停止取食,相同暴露时间下随着温度的降低存活率下降;蛹对0℃的耐受力高于成虫和幼虫,暴露4 h后可以正常羽化,48 h后全部死亡;卵对短时间的低温具有一定耐受力,但随着暴露时间的延长存活率降低幅度大。     

Variation in the methods leads to variation in the interpretation of biodiversity–ecosystem multifunctionality relationships

生物多样性常常和生态系统多功能性(生态系统同时提供多个生态系统功能的能力)正相关。然而,生物多样性与生态系统多功能性的关系是否依赖于生态系统功能的数目有诸多争议。其中,生物多样性对生态系统多功能性的影响或许不随生态系统功能数目的变化而变化,或者随生态系统功能数目的增多而增强。我们期望通过研究不同生态系统多功能性指数的统计原理来解决这些争议。 我们使用了模型模拟和一系列来自不同空间尺度(从局域到全球)和不同生物群系(温带和高寒草地、森林和干旱地)的经验数据。我们回顾了量化生态系统多功能性的三种方法,包括平均值法、加和法和阈值法。我们发现随着生态系统功能数目的增加,生物多样性与生态系统多功能性的关系要么不变,要么增强。这些结果可由平均和加和的多功能性指数的统计原理来解释。具体来讲,当利用生态系统功能的平均值计算多功能性指数时,由于多样性对多功能性的效应等于多样性对单个生态系统功能效应的平均值,所以不会随生态系统功能数目的变化而变化。同样的道理,当利用单个生态系统的加和值计算多功能性指数时,多样性的效应会随着生态系统功能数目的增加而增强。我们提出了一个改进的多功能性指数,将平均或加和多功能性指数转化为标准化的多功能性指数, 以便于对不同研究的结果进行比较。此外,我们提出了基于变量数值范围的标准化方法来解决阈值法的数学假象问题(多样性效应随生态系统功能数目的增加而增强)。我们的研究结果表明,量化多功能性指数的方法不同,结果也不同。因此,有必要加深对不同方法数理基础的理解。而标准化的多功能性指数为比较不同研究中的生物多样性与生态系统多功能性的关系提供了有效的方法。     

阿尔茨海默病体液生物学标记物研究进展

由于阿尔茨海默病患者的增多及其危害性, 建立能够用于早期诊断的方法受到人们的高度关注. 脑脊液和血液中某些生物学标记物与AD的典型病理变化老年斑(senile plaques, SP)和神经元纤维缠结(neurofibrillary tangles, NTFs)相关, 在临床诊断和治疗方面显示了广阔的前景, 但截止目前尚缺乏灵敏、特异的生物学标记物及分析方法用以诊断和监测疾病进程. 本文详细综述了近年来体液中阿尔茨海默病生物学标记物及其分析方法的研究进展, 鉴于其病理的复杂性, 许多问题仍有待深入研究.     

Analysis of Pathotypic and Genotypic Diversity of Xanthomonas oryzae pv. oryzae in China

Virulence analysis and restriction fragment length polymorphism (RFLP) were used to evaluated the population structure of Xanthomonas oryzae pv . oryzae ( Xoo ) from the main rice-growing region in China. The pathotype of Xoo was determined for 103 strains by inoculating 13 near-isogenic rice lines using IR24 as the recurrent parent. Sixty-one pathotypes was shared by these strains, on the basis of the consensus of three clustering statistics, and four clusters for pathotype were formed. Cluster 2 consists of strains with high molecular polymorphorism and many pathotypes that are either virulent to a majority of the 13 major resistance ( R ) genes or avirulent only to Xa21 , and is geographically dispersed. The resistance gene Xa21 has broader resistance than others to the strains tested. A probe from a member of the avrBs3/pthA type III effector family, 1376 bp Sph I-digested fragment, was used to screen the genomes of 52 strains tested. Four common bands were found in the DNA fingerprint pattern of Xoo , suggesting basic patterns of evolutionary relationship for members of avrBs3/pthA family and/or the pathogen. Each distinct RFLP banding pattern of each strain was considered as a haplotype; 42 haplotypes were revealed by the probe and divided into four lineages by the same statistics method. It was observed that some isolates with different pathotypes shared the same haplotype and others with different haplotypes harboured identical pathotype. There was a weak correlation between virulent pathotypes and molecular haplotypes.     

甘薯根腐病菌侵染对甘薯内源激素水平的影响

甘薯根腐病病原菌[Fusarium solani(Mart.)Sacc.f.sp.batatas McClure,简称FSB]侵染及其培养液滤液处理高敏感性甘薯品种‘胜利百号’后,引起甘薯叶片、茎尖和根部组织内源ABA含量大幅升高。其中在根部出现最早,但茎尖中积累浓度最高。侵染后甘薯叶片、茎尖和根部组织内源GA1/3含量显著低于对照。甘薯组培苗经FSB培养滤液处理9h后,ABA含量显著上升,处理15h,ABA含量呈下降趋势,而GA1/3含量在101和102稀释液处理15h(103稀释液处理12h)时出现显著上升。这些结果有助于解释甘薯根腐病株矮小不产生藤蔓,并在秋季大量现蕾开花的生理现象。     

Preparation of (+)-Trans-Isoalliin and Its Isomers by Chemical Synthesis and RP-HPLC Resolution

Naturally occurring (+)-trans-isoalliin, (R_CR_S)-(+)-trans-S-1-propenyl-L-cysteine sulfoxide, is a major cysteine sulfoxide in onion. The importance of producing it synthetically to support further research is very well recognized. The (+)-trans-isoalliin is prepared by chemical synthesis and reversed-phase (RP)-HPLC. First, S-2-propenyl-L-cysteine (deoxyalliin) is formed from L-cysteine and allyl bromide, which is then isomerized to S-1-propenyl-L-cysteine (deoxyisoalliin) by a base-catalyzed reaction. A mixture of cis and trans forms of deoxyisoalliin is formed and separated by RP-HPLC. Oxidation of the trans form of deoxyisoalliin by H₂O₂ produces a mixture of (−)- and (+)-trans-isoalliin. Finally, RP-HPLC is used successfully in separating (−)- and (+)-trans-isoalliin, and hence, (+)-trans-isoalliin is synthesized for the first time in this study. In addition, the (±) diastereomers of cis-isoalliin are also separated and purified by RP-HPLC.     

Grazing increases functional richness but not functional divergence in Tibetan alpine meadow plant communities

Plant community diversity and ecosystem function are conditioned by competition among co-occurring species for multiple resources. Previous studies suggest that removal of standing biomass by grazing decreases competition for light, but coincident grazing effects on competition for soil nutrients remain largely unknown in Tibetan rangelands where grazing tends to deplete soil phosphorus availability. We measured five functional traits indicative of plant productivity and stoichiometry leaf carbon concentration (LCC), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), specific leaf area (SLA), leaf dry matter content (LDMC) for component species of plant communities in grazed and ungrazed plots in five Tibetan alpine meadows. We examined the diversity of traits singly Rao index of functional diversity (FDrao) and in aggregate functional richness (FRic), functional divergence (FDiv), and functional evenness (FEve) in response to grazing. We tested whether foliar trait diversity increases with nutrient competition but decreases with light competition when competitive exclusion is reduced by grazing. The FDrao of LPC significantly increased under grazing, but FDrao for LCC, LNC and SLA tended to decrease. The FDrao of LDMC increased at the drier site but decreased at the wettest site. There was a strong negative association between increase in FDrao of LPC and decrease in soil nutrients, especially soil phosphorus availability. The FRic for all five traits together increased with species diversity following grazing, but neither FDiv nor FEve differed significantly between grazed and ungrazed plots at most sites. Grazing in Tibetan alpine meadows tends to increase competition for soil phosphorus while decreasing competition for light, resulting in an increase in the functional richness in grazed plant communities without any significant changes in the overall functional diversity of foliar traits. Our study highlights the potential importance of grazing mediated competition for multiple resources in alpine meadow ecosystems.     

Early-spring soil warming partially offsets the enhancement of alpine grassland aboveground productivity induced by warmer growing seasons on the Qinghai-Tibetan Plateau

Aims

The response of vegetation productivity to global warming is becoming a worldwide concern. While most reports on responses to warming trends are based on measured increases in air temperature, few studies have evaluated long-term variation in soil temperature and its impacts on vegetation productivity. Such impacts are especially important for high-latitude or high-altitude regions, where low temperature is recognized as the most critical limitation for plant growth.

Methods

We used Partial Least Squares regression to correlate long-term aboveground net primary productivity (ANPP) data of an alpine grassland on the Qinghai-Tibetan Plateau with daily air and soil temperatures during 1997–2011. We also analyzed temporal trends for air temperature and soil temperature at different depths.

Results

Soil temperatures have steadily increased at a rate of 0.4–0.9 °C per decade, whereas air temperatures showed no significant trend between 1997 and 2011. While temperature increases during the growing season (May–August) promoted aboveground productivity, warming before the growing season (March–April) had a negative effect on productivity. The negative effect was amplified in the soil layers, especially at 15 cm depth, where variation in aboveground productivity was dominated by early-spring soil warming, rather than by increasing temperature during the growing season.

Conclusions

Future warming, especially in winter and spring, may further reduce soil water availability in early spring, which may slow down or even reverse the increases in grassland aboveground productivity that have widely been reported on the Qinghai-Tibetan Plateau.

     

The P2Y12 Antagonists, 2-Methylthioadenosine 5��-Monophosphate Triethylammonium Salt and Cangrelor (ARC69931MX), Can Inhibit Human Platelet Aggregation through a Gi-independent Increase in cAMP Levels

ADP plays an integral role in the process of hemostasis by signaling through two platelet G-protein-coupled receptors, P2Y₁ and P2Y₁₂. The recent use of antagonists against these two receptors has contributed a substantial body of data characterizing the ADP signaling pathways in human platelets. Specifically, the results have indicated that although P2Y₁ receptors are involved in the initiation of platelet aggregation, P2Y₁₂ receptor activation appears to account for the bulk of the ADP-mediated effects. Based on this consideration, emphasis has been placed on the development of a new class of P2Y₁₂ antagonists (separate from clopidogrel and ticlopidine) as an approach to the treatment of thromboembolic disorders. The present work examined the molecular mechanisms by which two of these widely used adenosine-based P2Y₁₂ antagonists (2-methylthioadenosine 5′-monophosphate triethylammonium salt (2MeSAMP) and ARC69931MX), inhibit human platelet activation. It was found that both of these compounds raise platelet cAMP to levels that substantially inhibit platelet aggregation. Furthermore, the results demonstrated that this elevation of cAMP did not require G_i signaling or functional P2Y₁₂ receptors but was mediated through activation of a separate G protein-coupled pathway, presumably involving G_s. However, additional experiments revealed that neither 2MeSAMP nor ARC69931MX (cangrelor) increased cAMP through activation of A2a, IP, DP, or EP₂ receptors, which are known to couple to G_s. Collectively, these findings indicate that 2MeSAMP and ARC69931MX interact with an unidentified platelet G protein-coupled receptor that stimulates cAMP-mediated inhibition of platelet function. This inhibition is in addition to that derived from antagonism of P2Y₁₂ receptors.Upon damage to the endothelial layer of the blood vessel wall, the underlying subendothelium is exposed to platelets in the blood, initiating a cascade of signaling events resulting in the transformation of “resting” platelets into “activated” platelets (1). One significant characteristic associated with these signaling events is the secretion of ADP from the platelet-dense granules (2). This released ADP acts to further amplify the platelet activation response by interacting with its G-protein-coupled receptors on the platelet surface, namely P2Y₁ (coupled to G_q) and P2Y₁₂ (coupled to G_i) (3–5). The consequence of platelet activation through ADP is a conformational change in the platelet membrane glycoprotein αIIbβ3 (6, 7), which then binds to fibrinogen present in the plasma. The binding of fibrinogen with αIIbβ3 on the surface of adjacent platelets results in fibrinogen-platelet cross-linking and the formation of a hemostatic plug at the site of vascular injury (8).Consequently, ADP is thought to play an integral role in the normal process of hemostasis. Of the two ADP-receptor signaling pathways in platelets, evidence has indicated that ADP-mediated P2Y₁₂ signaling appears to play a more prominent role in platelet activation than ADP-mediated P2Y₁ signaling (9, 10). For the most part, support for this notion derives from the use of the adenosine-based P2Y₁₂ antagonists (i.e. 2MeSAMP⁴ and ARC69931MX), which have a much broader inhibitory profile than P2Y₁ antagonists (e.g. A3P5P (adenosine-3′-phosphate-5′-phosphate) or MRS2179) (9). Thus, 2MeSAMP and ARC69931MX inhibit platelet aggregation in response to multiple agonists, such as thromboxane A₂, collagen, thrombin, etc. (11–13), whereas P2Y₁ antagonists do not. On the other hand, this general requirement for P2Y₁₂ signaling seems to be inconsistent with earlier reports indicating that activation of certain platelet receptors (e.g. thromboxane A₂ receptor) can cause aggregation through ADP-independent mechanisms (14, 15). Based on this apparent inconsistency in the contribution of P2Y₁₂ signaling to the overall platelet activation response, the present study investigated the possibility that the broad spectrum of inhibitory activity of this new generation of P2Y₁₂ antagonists (i.e. MeSAMP and ARC69931MX) may derive from an elevation in platelet cAMP levels.Our data demonstrated that both 2MeSAMP and ARC69931MX do in fact significantly raise human platelet cAMP. Furthermore, this pharmacological effect is independent of P2Y₁₂-G_i signaling and appears to proceed through activation of a separate G_s-coupled platelet receptor. Taken together, the results therefore indicate that these adenosine-based P2Y₁₂ antagonists can produce their inhibition of platelet function through a cAMP-mediated mechanism.     

Palladium nanoparticle/chitosan-grafted graphene nanocomposites for construction of a glucose biosensor

Graphene (GR) was covalently functionalized with chitosan (CS) to improve its biocompatibility and hydrophilicity for the preparation of biosensors. The CS-grafted GR (CS-GR) rendered water-soluble nanocomposites that were readily decorated with palladium nanoparticles (PdNPs) using in situ reduction. Results with TEM, SEM, FTIR, Raman and XRD revealed that CS was successfully grafted without destroying the structure of GR, and PdNPs were densely decorated on CS-GR sheets with no aggregation occurring. A novel glucose biosensor was then developed through covalently immobilizing glucose oxidase (GOD) on a glassy carbon electrode modified with the PdNPs/CS-GR nanocomposite film. Due to synergistic effect of PdNPs and GR, the PdNPs/CS-GR nanocomposite film exhibited excellent electrocatalytical activity toward H(2)O(2) and facilitated high loading of enzymes. The biosensor demonstrated high sensitivity of 31.2 μA mM(-1)cm(-2) for glucose with a wide linear range from 1.0 μM to 1.0mM as well as a low detection limit of 0.2 μM (S/N=3). The low Michaelis-Menten constant (1.2mM) suggested enhanced enzyme affinity to glucose. These results indicated that PdNPs/CS-GR nanocomposites held great potential for construction of a variety of electrochemical biosensors.