长期不同施肥措施下岩溶水稻土可培养细菌群落变化及其主要影响因素

【背景】施肥是目前提高作物产量的较优策略,不同的施肥措施在不同程度上影响土壤肥力和微生物群落结构。【目的】探究岩溶水稻土理化性质变化与细菌群落变化的对应关系,进而反映不同施肥措施对土壤可培养细菌群落的影响。最后选出最优施肥方案,为后续的合理施肥工作提供依据。【方法】对岩溶水稻土进行不施肥、常规施肥、常规施肥加绿肥3种施肥处理,通过对土壤理化性质、可培养细菌群落丰度及多样性变化的研究,探究在不同施肥措施下对岩溶水稻土壤细菌群落的影响。【结果】对比不施肥处理,常规施肥处理下土壤pH值和有机碳含量下降,结合大量研究结果证明,无机肥或氮肥的长期过量施加使土壤pH值下降,常规施肥加绿肥有利于有机碳的积累。分离纯化共得到164株菌,分别来自Actinobacteria、Bacteroidetes、Firmicutes和Proteobacteria。属水平上常规施肥配施绿肥较常规施肥组优势菌属Sphingomonas、Lysobacter的相对丰度增加。细菌群落多样性增加,出现Paenibacillus、Streptomyces和Pseudomonas等特有功能菌属。优势菌属Sphingopyxis、Lysobacter、Paenibacillus、Bosea、Streptomyces、Pseudomonas和Bacillus与TN存在显著正相关,在常规施肥加绿肥处理土壤中增加。【结论】常规施肥加绿肥处理下,固氮、溶磷等功能菌丰度增加,增加土壤肥力,保持土壤养分的可利用性,对作物的增产起重要作用。岩溶水稻土常规施肥配施绿肥处理的效果优于不施肥和常规施肥处理。     

巨峰葡萄花芽分化过程中成花基因LEA FY的表达

目的:研究LEAFY基因在巨峰葡萄花芽分化期间的表达差异,为实际生产提供理论依据。方法:用半定量RT-PCR方法研究LEAFY基因在巨峰葡萄花芽分化期间的表达。结果:LEAFY基因的表达量在所研究的8个时期内有明显差异,在5叶期、6叶期、7叶期、8叶期的表达量相对较高。结论:根据成花基因LEAFY表达上的差异,可以人为地提前或延迟巨峰葡萄的花期。     

栎旋木柄天牛生殖行为研究

为了阐明栎旋木柄天牛Aphrodisium sauteri Matsushita生殖行为的方式和特点,寻找有效的防治手段,本试验观察了栎旋木柄天牛的生殖行为,并在林间尝试了成虫诱集。结果表明:雌雄成虫之间表现出较强的吸引作用,近距离时雌雄虫可相互吸引,而远距离时雌虫引诱力更强。室内试验中求偶时间会随着成虫的衰弱而增加。成虫交配主要发生于白天。羽化出孔后1～14日龄雌虫和2～13日龄雄虫均可多次交配。成虫一次完整交配平均需时70.12min,交配后保护平均仅用时3.86min。一次完整交配过程中,不同日龄成虫的交配历时、交配间隔历时及交配次数都存在差异,各日龄成虫的交配间隔历时均大于交配历时。交配或产卵经历对雄虫交配行为的影响明显大于雌虫。雌虫产卵前期平均为30.71h。雌虫每产1粒卵平均需时99.58s,并随日龄增长显著加长。每头雌虫平均每日产卵量和总产卵量分别为7.89和26.20粒。雌虫多在白天产卵,用产卵器触探树皮表面寻找合适的产卵部位。卵主要产于树皮裂缝和枝条疤痕内,一般每次产卵1粒,卵表面无覆盖物。     

The role of repair protein Rad51 in synergistic cytotoxicity and mutagenicity induced by epidermal growth factor receptor inhibitor (Gefitinib, IressaR) and benzo[a]pyrene in human lung cancer

Rad51 protein is essential for homologous recombination repair of DNA damage, and is over-expressed in chemo- or radioresistant carcinomas. The polycyclic hydrocarbon carcinogen benzo[a]pyrene (B[a]P) affects MAPKs transduction pathways. Gefitinib (IressaR, ZD1839) is a selective epidermal growth factor receptor tyrosine kinase inhibitor that blocks growth factor-mediated cell proliferation and ERK1/2 activation. We hypothesized that gefitinib enhances B[a]P-mediated cytotoxicity by decreasing ERK1/2 activation. Exposure of human lung cancer cells to gefitinib decreased B[a]P-elicited ERK1/2 activation and induced Rad51 protein expression. Gefitinib and B[a]P co-treatment decreased Rad51 protein stability by triggering degradation via a 26S proteasome-dependent pathway. Expression of constitutive active MKK1/2 vectors (MKK1/2-CA) rescues the decreased ERK1/2 activity, and restores Rad51 protein level and stability under gefitinib and B[a]P co-treatment. Gefitinib enhances B[a]P-induced growth inhibition, cytotoxicity and mutagenicity. Co-treatment with gefitinib and B[a]P can further inhibit cell growth significantly after depletion of endogenous Rad51 by siRad51 RNA transfection. Enhancement of ERK1/2 activation by MKK1-CA expression decrease B[a]P- and gefitinib-induced cytotoxicity, and B[a]P-induced mutagenicity. Rad51 protein protects lung cancer cells from synergistic cytotoxic and mutagenic effects induced by gefitinib and B[a]P. Suppression of Rad51 protein expression may be a novel lung cancer therapeutic modality to overcome drug resistance to gefitinib.     

Bioassay evidence for the transmission of WSSV by the harpacticoid copepod Nitocra sp

White Spot Syndrome Virus (WSSV) is now one of the most devastating and virulent viral agents threatening the penaeid shrimp culture industry and has been responsible for serious economic losses for shrimp farms worldwide. One remarkable characteristic of WSSV is its wide reservoir range, which contributes to its wide geographical distribution. Among epizootiological surveys, there is substantial evidence for WSSV-positive copepods found in shrimp farming ponds. Therefore, copepods are suspected to be the vector of WSSV. In the present study, nested-PCR analysis showed positive results in the harpacticoid copepod Nitocra sp. exposed to WSSV by virus-phytoplankton adhesion route. Oral route and intramuscular injection were used to test the pathogenicity of WSSV isolated from the WSSV-positive Nitocra sp. For the oral route of infection, Marsupenaeus japonicus postlarvae were fed with WSSV-positive copepods. The shrimp postlarvae in the infected treatment became WSSV-positive and occurred 52.50+/-5.00% mortality which was significant higher (P <0.05) than that in the control treatment (20.00+/-0.00%) when postlarvae were fed with WSSV free copepods. In the intramuscular injection challenge, M. japonicus juveniles were injected with the copepods inoculum extracted from the WSSV-positive Nitocra sp., and showed 72.50+/-9.57% mortality which was also significant higher (P <0.05) than that in the control treatment (22.50+/-5.00%) when juveniles were received mock injection of a tissue homogenate prepared from WSSV-negative Nitocra sp. Based on these laboratory challenge studies, it was confirmed that the copepods can serve as a vector in WSSV transmission.     

蛋白质组研究中的化学"探针"

随着蛋白质组学概念的提出以及诸如血浆蛋白质组等有影响力的计划开展, 蛋白质组研究迅速发展起来, 这门基于分析化学和物理化学的领域也逐渐为广大生物学家所关注, 同时也相应地在细胞生物学、生物化学等领域的研究中崭露头角。蛋白质表达量的变化以及各种各样的修饰无不反映出机体对环境变化的应激和自身功能的需要。因此, 定量蛋白质组和修饰化的蛋白质组成为了目前蛋白质组研究的重要领域之一。文章着重从采用化学标记实现定量和修饰化研究这个角度来介绍近些年来在这方面取得的进展, 希望对生物学领域的研究有所借鉴。     

21种杀虫剂和3种植物次生物质对杨扇舟蛾各组织谷胱甘肽S-转移酶的抑制作用

为了比较杨扇舟蛾Clostera anachoreta (Fabricius)各组织谷胱甘肽S 转移酶（GSTs）的差异,利用分光光度酶动力学的方法,研究了21种杀虫剂和3种植物次生物质对杨扇舟蛾4个组织（中肠、脂肪体、头部和体壁）GSTs活性的体外影响。结果表明:21种杀虫剂和3种植物次生物质对杨扇舟蛾4个组织GSTs活性的抑制作用不同。毒死蜱、氟虫腈、槲皮素和单宁酸对于杨扇舟蛾头GSTs活性抑制作用最强;槲皮素和单宁酸对中肠GSTs活性的抑制作用最强;单宁酸对脂肪体GSTs活性的抑制作用最强;辛硫磷、高效氯氟氰菊酯、溴氰菊酯和硫丹对皮GSTs活性的抑制作用最强。杨扇舟蛾4个组织GSTs对杀虫剂和植物次生物质敏感性存在的这种差异,可能是由于其在同工酶组成上的差异造成的。     

Slow spontaneous ��-to-�� structural conversion in a non-denaturing neutral condition reveals the intrinsically disordered property of the disulfide-reduced recombinant mouse prion protein

In prion diseases, the normal prion protein is transformed by an unknown mechanism from a mainly α-helical structure to a β-sheet-rich, disease-related isomer. In this study, we surprisingly found that a slow, spontaneous α-to-coil-to-β transition could be monitored by circular dichroism spectroscopy in one full-length mouse recombinant prion mutant protein, denoted S132C/N181C, in which the endogenous cysteines C179 and C214 were replaced by Ala and S132 and N181 were replaced by Cys, during incubation in a non-denaturing neutral buffer. No denaturant was required to destabilize the native state for the conversion. The product after this structural conversion is toxic β-oligomers with high fluorescence intensity when binding with thioflavin T. Site-directed spin-labeling ESR data suggested that the structural conversion involves the unfolding of helix 2. After examining more protein mutants, it was found that the spontaneous structural conversion is due to the disulfide-deletion (C to A mutations). The recombinant wild-type mouse prion protein could also be transformed into β-oligomers and amyloid fibrils simply by dissolving and incubating the protein in 0.5 mM NaOAc (pH 7) and 1 mM DTT at 25°C with no need of adding any denaturant to destabilize the prion protein. Our findings indicate the important role of disulfide bond reduction on the structural conversion of the recombinant prion protein, and highlight the special “intrinsically disordered” conformational character of the recombinant prion protein.     

NMR characterization of the electrostatic interaction of the basic residues in HDGF and FGF2 during heparin binding

Electrostatic interaction is a major driving force in the binding of proteins to highly acidic glycosaminoglycan, such as heparin. Although NMR backbone chemical shifts have generally been used to identify the heparin-binding site on a protein, however, there is no correlation between the binding free energies and the perturbed backbone chemical shifts for individual residues. The binding event occurs at the end of a side chain of basic residue, and does not require causing significant alterations in the backbone environment at a distance of multiple bonds. We used the H₂CN NMR pulse sequence to detect heparin binding through the side-chain resonances Hε–Cε–Nζ of Lys and Hδ–Cδ–Nε of Arg in the two proteins of hepatoma-derived growth factor (HDGF) and basic fibroblast growth factor (FGF2). H₂CN titration experiments revealed chemical shift perturbations in the side chains, which were correlated with the free energy changes in various mutants. The residues K19 in HDGF and K125 in FGF2 demonstrated the most significant perturbations, consistent with our previous observation that the two residues are crucial for binding. The result suggests that H₂CN NMR provides a precise evaluation for the electrostatic interactions. The discrepancy observed between backbone and side chain chemical shifts is correlated to the solvent accessibility of residues that the K19 and K125 backbones are highly buried with the restricted backbone conformation and are not strongly affected by the events at the end of the side chains.