Warming and grazing enhance litter decomposition and nutrient release independent of litter quality in an alpine meadow

增温和放牧对高寒草甸凋落物分解及其养分释放的影响不依赖于凋落物品质在放牧生态系统中,增温、放牧和凋落物品质共同决定着凋落物分解和养分释放。然而,在以往的研究中这些因子的效应通常被单独地研究。在本研究中,我们在青藏高原高寒草甸开展了一个昼夜非对称增温和中度放牧两因子的凋落物分解试验。从每个处理中收集了凋落物样品,这些凋落物一部分放在它们的来源处理小区,另一部分放在其他处理小区以此来探究增温、放牧以及凋落物品质对凋落物分解和养分释放的影响。研究结果表明,增温而不是放牧显著增加了凋落物质量的损失、单位面积全碳、全氮以及全磷含量的损失,这主要是因为增温增加了凋落物生物量和分解速率。然而,尽管同时增温放牧处理也加快了凋落物分解速率,但由于降低了凋落物生物量,所以增温放牧处理并没有显著影响单位面积的凋落物碳和养分释放量。相比木质素含量和碳氮比而言,季节性土壤平均温度能够更好地预测凋落物分解速率。增温和放牧对凋落物分解存在交互作用,但它们和凋落物品质对凋落物的影响均不存在交互作用。单位面积的总氮释放的温度敏感性要高于总磷。因此,我们的结果表明,增温对凋落物分解以及养分释放的影响要显著大于凋落物品质变化对其分解的影响。在高寒草甸,氮释放的增加可能会间接导致土壤磷有效性的缺乏。     

Characterization of a new gene WX2 in Toxoplasma gondii

Using hybridization techniques, we prepared the monoclonal antibody （Mab） 7C3-C3 against Toxoplasma gondii. The protection tests showed that the protein （Mab7C3-C3） inhibited the invasion and proliferation of T. gondii RH strain in HeLa cells. The passive transfer test indicated that the antibody significantly prolonged the survival time of the challenged mice. It was also shown that the antibody could be used for the detection of the circulating antigen of T. gondii. After immunoscreening the T. gondii tachyzoite cDNA library with Mab7C3-C3, a new gene wx2 of T. gondii was obtained. Immunofluorescence analysis showed that the WX2 protein was located on the membrane of the parasite. Nucleotide sequence comparison showed 28% identity to the calcium channel α-IE unit and shared with the surface antigen related sequence in some conservative residues. However, no match was found in protein databases. Therefore, it was an unknown gene in T. gondii encoding a functional protein on the membrane of T. gondii. Because it has been shown to have a partial protective effect against T. gondii infection and is released as a circulating antigen, it could be a candidate molecule for vaccine or a novel target for new drugs.     

A CCCH-type zinc finger nucleic acid-binding protein quantitatively confers resistance against rice bacterial blight disease

Bacterial blight is a devastating disease of rice (Oryza sativa) caused by Xanthomonas oryzae pv oryzae (Xoo). Zinc finger proteins harboring the motif with three conserved cysteine residues and one histidine residue (CCCH) belong to a large family. Although at least 67 CCCH-type zinc finger protein genes have been identified in the rice genome, their functions are poorly understood. Here, we report that one of the rice CCCH-type zinc finger proteins, C3H12, containing five typical CX(8)-CX(5)-CX(3)-H zinc finger motifs, is involved in the rice-Xoo interaction. Activation of C3H12 partially enhanced resistance to Xoo, accompanied by the accumulation of jasmonic acid (JA) and induced expression of JA signaling genes in rice. In contrast, knockout or suppression of C3H12 resulted in partially increased susceptibility to Xoo, accompanied by decreased levels of JA and expression of JA signaling genes in rice. C3H12 colocalized with a minor disease resistance quantitative trait locus to Xoo, and the enhanced resistance of randomly chosen plants in the quantitative trait locus mapping population correlated with an increased expression level of C3H12. The C3H12 protein localized in the nucleus and possessed nucleic acid-binding activity in vitro. These results suggest that C3H12, as a nucleic acid-binding protein, positively and quantitatively regulates rice resistance to Xoo and that its function is likely associated with the JA-dependent pathway.     

Vimentin expressed on Mycobacterium tuberculosis-infected human monocytes is involved in binding to the NKp46 receptor

We previously showed that human NK cells used the NKp46 receptor to lyse Mycobacterium tuberculosis H37Ra-infected monocytes. To identify ligands on H37Ra-infected human mononuclear phagocytes, we used anti-NKp46 to immunoprecipitate NKp46 from NK cells bound to its ligand(s) on H37Ra-infected monocytes. Mass spectrometry analysis identified a 57-kDa molecule, vimentin, as a putative ligand for NKp46. Vimentin expression was significantly up-regulated on the surface of infected monocytes, compared with uninfected cells, and this was confirmed by fluorescence microscopy. Anti-vimentin antiserum inhibited NK cell lysis of infected monocytes, whereas antiserum to actin, another filamentous protein, did not. CHO-K1 cells transfected with a vimentin construct were lysed much more efficiently by NK cells than cells transfected with a control plasmid. This lysis was inhibited by mAb-mediated masking of NKp46 (on NK cells) or vimentin (on infected monocytes). ELISA and Far Western blotting showed that recombinant vimentin bound to a NKp46 fusion protein. These results indicate that vimentin is involved in binding of NKp46 to M. tuberculosis H37Ra-infected mononuclear phagocytes.     

An amplified mass piezoelectric immunosensor for Schistosoma japonicum

An ultrasensitive piezoelectric immunosensor using an amplification path based on an insoluble biocatalyzed precipitation product has proposed for Schistosoma japonicum. A mercapto Schistosoma japonicum antigen was self-assembled onto the quartz crystal surface via an Au nanoparticle mediator monolayer to sense the Schistosoma japonicum antibody (SjAb). And the horseradish peroxidase labeled protein A conjugate which was bounded to the SjAb by a "sandwich" format was used as a biocatalyst for the oxidative precipitation of 4-chloro-1-naphthol by H(2)O(2) to yield the insoluble product benzo-4-chlorohexadienone, resulting in an amplified mass sensing of antigen-antibody interaction. The amount of the precipitate accumulated on the quartz crystal is controlled by the antibody concentration. The SjAb can be linearly determined in the range of 10-200 ngml(-1) and the detection limit reaches as low as 5 ngml(-1).     

Transformation of iron sulfide to greigite by nitrite produced by oil field bacteria

Nitrate, injected into oil fields, can oxidize sulfide formed by sulfate-reducing bacteria (SRB) through the action of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB). When reservoir rock contains siderite (FeCO₃), the sulfide formed is immobilized as iron sulfide minerals, e.g. mackinawite (FeS). The aim of our study was to determine the extent to which oil field NR-SOB can oxidize or transform FeS. Because no NR-SOB capable of growth with FeS were isolated, the well-characterized oil field isolate Sulfurimonas sp. strain CVO was used. When strain CVO was presented with a mixture of chemically formed FeS and dissolved sulfide (HS⁻), it only oxidized the HS⁻. The FeS remained acid soluble and non-magnetic indicating that it was not transformed. In contrast, when the FeS was formed by adding FeCl₂ to a culture of SRB which gradually produced sulfide, precipitating FeS, and to which strain CVO and nitrate were subsequently added, transformation of the FeS to a magnetic, less acid-soluble form was observed. X-ray diffraction and energy-dispersive spectrometry indicated the transformed mineral to be greigite (Fe₃S₄). Addition of nitrite to cultures of SRB, containing microbially formed FeS, was similarly effective. Nitrite reacts chemically with HS⁻ to form polysulfide and sulfur (S⁰), which then transforms SRB-formed FeS to greigite, possibly via a sulfur addition pathway (3FeS + S⁰ → Fe₃S₄). Further chemical transformation to pyrite (FeS₂) is expected at higher temperatures (>60°C). Hence, nitrate injection into oil fields may lead to NR-SOB-mediated and chemical mineral transformations, increasing the sulfide-binding capacity of reservoir rock. Because of mineral volume decreases, these transformations may also increase reservoir injectivity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Out-of-plane dimeric Mn quadridentate Schiff-base complexes: Synthesis, structure and magnetic properties

Four Mn^III quadridentate Schiff-base compounds have been prepared and structurally characterized: [Mn(salpn)(CH₃OH)₂]BPh₄ (1), [Mn₂(salpn)₂(N₃)₂] (2), [Mn₂(salpn)₂(NCS)₂] (3), [Mn₂(salpn)₂(H₂O)₂](H₂O)(ClO₄)₂ (4) (salpn = N,N′-(1,2-propylene)-bis-(salicylideneiminate)). Among them, 1 is a discrete Mn^III monomeric complex with a square-bipyramidal geometry. Complexes 2, 3 and 4 form the similar phenolate-bridged out-of-plane dimers. Magnetic susceptibility studies reveal that 2, 3 and 4 all exhibit ferromagnetic intra-dimer coupling between Mn^III ions.     

Proteomic analysis of somatic embryogenesis in Valencia sweet orange (Citrus sinensis Osbeck)

Two dimensional gel electrophoresis combined with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was employed to study the somatic embryogenesis (SE) in Valencia sweet orange (Citrus sinensis Osbeck). Twenty-four differentially expressed proteins were identified at five time points of citrus SE (0, 1, 2, 3, 4 weeks after embryo initiation) covering globular, heart/torpedo and cotyledon-shaped embryo stages. The general expression patterns for these proteins were consistent with those appeared at 4 weeks of citrus SE. The most striking feature of our study was that five proteins were predicted to be involved in glutathione (GSH) metabolism and anti-oxidative stress, and they exhibited different expression patterns during SE. Based on that oxidative stress has been validated to enhance SE, the preferential representation for anti-oxidative proteins suggests that they could have a developmental role in citrus SE. Some proteins involved in cell division, photosynthesis and detoxification were also identified, and their possible roles in citrus SE were discussed.     

Dissection of the factors affecting development-controlled and race-specific disease resistance conferred by leucine-rich repeat receptor kinase-type <Emphasis Type="Italic">R</Emphasis> genes in rice

Development-controlled resistance and resistance specificity frequently restrict the application of a disease resistance (R) gene in crop breeding programs. Xa3/Xa26 and Xa21, encoding leucine-rich repeat (LRR)-kinase type plasma membrane proteins, mediate race-specific resistance to Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial blight, one of the most devastating rice diseases. Plants carrying Xa3/Xa26 and plants carrying Xa21 have different resistance spectra and the functions of the two R genes are regulated by developmental stage. Four chimeric genes encoding proteins consisting of different parts of XA3/XA26 and XA21 were constructed by domain swapping and transformed into a susceptible rice variety. The resistance spectra and development-regulated resistance of the transgenic plants carrying Xa3/Xa26, Xa21, or chimeric gene to different Xoo strains were analyzed in the same genetic background. The results suggest that the gradually increased expression of Xa3/Xa26 and Xa21 plays an important role in the progressively enhanced Xoo resistance during rice development. In addition, the LRR domains of XA3/XA26 and XA21 are important determinants of race-specific recognition during rice–Xoo interaction, but juxtamembrane regions of the two R proteins also appear to contribute to resistance specificity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.