Plant species composition in green spaces within the built-up areas of Beijing,China

Plant species composition is a critical issue in ecological research. Studies on the characteristics of plant species composition in the built-up areas, however, are hampered by a lack of basic field-based investigation. In this article, the plant species composition in the built-up areas of Beijing, China, is investigated using abundant field observations. The origin of species, chorological spectra, life forms and plant communities were determined. The characteristic species in each type of green space were determined by k-means classification, and urban plant communities were identified by two-way indicator species analysis (TWINSPAN). Plant species composition in the built-up areas was further compared with that in natural mountain floras in Beijing to reveal the differences in life form composition and chorological spectra, and the coincidence of species in the two communities. A total of 618 plant species belonging to 349 genera and 103 families were identified. Our results revealed wide chorological spectra with trees dominated by deciduous species. Although native plant species were widely distributed, 53% of the plant species were aliens, among which 67% were introduced from America and other Asian countries. Furthermore, the characteristics of the plant species composition in the built-up areas are significantly different from those of the natural habitats. Our results highlight the dramatic changes in characteristics of plant species composition in the built-up area of Beijing. Several suggestions are proposed to increase the diversity of native species through the planning and management of green spaces.     

The MicroArray Quality Control (MAQC) project shows inter- and intraplatform reproducibility of gene expression measurements

Over the last decade, the introduction of microarray technology has had a profound impact on gene expression research. The publication of studies with dissimilar or altogether contradictory results, obtained using different microarray platforms to analyze identical RNA samples, has raised concerns about the reliability of this technology. The MicroArray Quality Control (MAQC) project was initiated to address these concerns, as well as other performance and data analysis issues. Expression data on four titration pools from two distinct reference RNA samples were generated at multiple test sites using a variety of microarray-based and alternative technology platforms. Here we describe the experimental design and probe mapping efforts behind the MAQC project. We show intraplatform consistency across test sites as well as a high level of interplatform concordance in terms of genes identified as differentially expressed. This study provides a resource that represents an important first step toward establishing a framework for the use of microarrays in clinical and regulatory settings.     

Using RNA sample titrations to assess microarray platform performance and normalization techniques

We have assessed the utility of RNA titration samples for evaluating microarray platform performance and the impact of different normalization methods on the results obtained. As part of the MicroArray Quality Control project, we investigated the performance of five commercial microarray platforms using two independent RNA samples and two titration mixtures of these samples. Focusing on 12,091 genes common across all platforms, we determined the ability of each platform to detect the correct titration response across the samples. Global deviations from the response predicted by the titration ratios were observed. These differences could be explained by variations in relative amounts of messenger RNA as a fraction of total RNA between the two independent samples. Overall, both the qualitative and quantitative correspondence across platforms was high. In summary, titration samples may be regarded as a valuable tool, not only for assessing microarray platform performance and different analysis methods, but also for determining some underlying biological features of the samples.     

Expression of gloshedobin,a thrombin-like enzyme from the venom of Gloydius shedaoensis,in Escherichia coli

Gloshedobin, a thrombin-like enzyme from the venom of Gloydius shedaoensis, was expressed in Escherichia coli using expression vector pET-32a(+). The gene was expressed under T7 promotor with a fusion partner of Thx.Tag and a 6xHis.Tag at its 5 terminal. After induction by IPTG for 6 h, the recombinant enzyme was expressed in the cytoplasm. Expression at 25°C gave twice the amount of recombinant gloshedobin in cytoplasm than at 37°C.     

The plant cyclin-dependent kinase inhibitor ICK1 has distinct functional domains for in vivo kinase inhibition,protein instability and nuclear localization

Interactor/inhibitor 1 of Cdc2 kinase (ICK1) from Arabidopsis thaliana is the first plant cyclin-dependent kinase (CDK) inhibitor, and overexpression of ICK1 inhibits CDK activity, cell division and plant growth in transgenic plants. In this study, ICK1 and deletion mutants were expressed either alone or as green fluorescent protein (GFP) fusion proteins in transgenic Arabidopsis plants. Deletion of the C-terminal 15 or 29 amino acids greatly reduced or completely abolished the effects of ICK1 on the transgenic plants, and recombinant proteins lacking the C-terminal residues lost the ability to bind to CDK complex and the kinase inhibition activity, demonstrating the role of the conserved C-terminal domain in in vivo kinase inhibition. In contrast, the mutant ICK1DeltaN108 with the N-terminal 108 residues deleted had much stronger effects on plants than the full-length ICK1. Analyses demonstrated that this effect was not because of an enhanced ability of ICK1DeltaN108 protein to inhibit CDK activity, but a result of a much higher level of ICK1DeltaN108 protein in the plants, indicating that the N-terminal domain contains a sequence or element increasing protein instability in vivo. Furthermore, GFP-ICK1 protein was restricted to the nuclei in roots of transgenic plants, even with the C-terminal or the N-terminal domain deleted, suggesting that a sequence in the central domain of ICK1 is responsible for nuclear localization. These results provide mechanistic understanding about the function and regulation of this cell cycle regulator in plants.     

Depletion of collagen II-reactive T cells and blocking of B cell activation prevents collagen II-induced arthritis in DBA/1j mice

Collagen II (CII)-induced arthritis in DBA/1j mice is mediated by both CII-reactive T cells and anti-CII Ab-producing B cells. To determine the relative role of these processes in the development of arthritis, we specifically eliminated CII-reactive T cells by treating the mice with CII-pulsed syngeneic macrophages that had been transfected with a binary adenovirus system. These macrophages express murine Fas ligand in a doxycycline-inducible manner with autocrine suicide inhibited by concomitant expression of p35. The mice were treated i.v. with four doses of CII-APC-AdFasLp35Tet or a single dose of AdCMVsTACI (5 x 10(9) PFU), or both simultaneously, beginning 2 wk after priming with CII in CFA. Treatment with CII-APC-AdFasLp35Tet alone or in combination with a single dose of AdCMVsTACI prevented the development of CII-induced arthritis and T cell infiltration in the joint. The elimination of T cells was specific in that a normal T cell response was observed on stimulation with OVA after treatment with CII-APC-AdFasLp35Tet. Treatment with AdCMVsTACI alone prevented production of detectable levels of circulating anti-CII autoantibodies and reduced the severity of arthritis but did not prevent its development. These results indicate that the CII-reactive T cells play a crucial role in the development of CII-induced arthritis and that the anti-CII Abs act to enhance the development of CII-induced arthritis.     

Control of petal and pollen development by the plant cyclin-dependent kinase inhibitor ICK1 in transgenic <Emphasis Type="Italic">Brassica</Emphasis> plants

The cyclin-dependent protein kinases (CDKs) have a central role in cell cycle regulation and can be inhibited by the binding of small protein CDK inhibitors. The first plant CDK inhibitor gene ICK1 was previously identified in Arabidopsis thaliana. In comparison to known animal CDK inhibitors, ICK1 protein exhibits unique structural and functional properties. The expression of ICK1 directed by the constitutive CaMV 35S promoter was shown to inhibit cell division and plant growth. The aim of this study was to determine the effects of ICK1 overexpression on particular organs and cells. ICK1 was expressed in specific tissues or cells of Brassica napus L. plants using two tissue-specific promoters, Arabidopsis AP3 and Brassica Bgp1. Transgenic AP3-ICK1 plants were morphologically normal except for some modified flowers either without petals or with petals of reduced size. Surprisingly, petals of novel shapes such as tubular petals were also observed, indicating a profound effect of cell division inhibition on morphogenesis. The cell size in the smaller modified petals was similar to that in control petals, suggesting that the reduction of petal size is mainly due to the reduction of cell numbers and that the inhibition of cell division does not necessarily lead to an increase in cell size. Transgenic Bgp1-ICK1 plants were normal morphologically; however, dramatic decreases in seed production were observed in some plants. In those plants, the ability of pollen to germinate and pollen nuclear number were affected. These results are discussed in relation to the cell cycle and plant development.     

一类具有时滞的神经网络模型的收敛性

运用Lyapunov泛函方法,讨论一类具有时滞的神经网络模型平衡点的全局渐近稳定性,并获得一个新的充分条件．