Biosystematic studies inErythronium (Liliaceae-Tulipeae)

The floral biology ofErythronium japonicum has been studied from two approaches: a reinvestigation of its floral morphology and a pollinator case history. The perianth, differentiated into a sepal and petal cycle, has a tubular, but free arrangement basally around a slightly stipitate ovary. The two cycles of stamens with dimorphic filaments are positioned by the differently lobed auricles of the mature sepals and petals. These auricles also form a trap-lid mechanism for the inverted nectary which also has passageways. The perianth parts are highly UV absorbant due to the presence of flavonoids. This pattern contrasts strikingly with the purple trident basal guide lines so prominent in the visible spectrum. The weakly protandrous flowers also have exserted styles, thus functioning to exclude its own pollen and insure outbreeding. These floral adaptations are related specifically to the pollination behavior ofXylocopa appendiculata, and in general to the floral evolution within the genusErythronium. This work was supported in part by the U.S.-Japan Cooperative Science Program Grant GF-41367 and Grant-in-Aid No. 934053 from the Ministry of Education, Japan.     

Quantifying agonist activity at G protein-coupled receptors

When an agonist activates a population of G protein-coupled receptors (GPCRs), it elicits a signaling pathway that culminates in the response of the cell or tissue. This process can be analyzed at the level of a single receptor, a population of receptors, or a downstream response. Here we describe how to analyze the downstream response to obtain an estimate of the agonist affinity constant for the active state of single receptors. Receptors behave as quantal switches that alternate between active and inactive states (Figure 1). The active state interacts with specific G proteins or other signaling partners. In the absence of ligands, the inactive state predominates. The binding of agonist increases the probability that the receptor will switch into the active state because its affinity constant for the active state (K(b)) is much greater than that for the inactive state (K(a)). The summation of the random outputs of all of the receptors in the population yields a constant level of receptor activation in time. The reciprocal of the concentration of agonist eliciting half-maximal receptor activation is equivalent to the observed affinity constant (K(obs)), and the fraction of agonist-receptor complexes in the active state is defined as efficacy (ε) (Figure 2). Methods for analyzing the downstream responses of GPCRs have been developed that enable the estimation of the K(obs) and relative efficacy of an agonist. In this report, we show how to modify this analysis to estimate the agonist K(b) value relative to that of another agonist. For assays that exhibit constitutive activity, we show how to estimate K(b) in absolute units of M(-1). Our method of analyzing agonist concentration-response curves consists of global nonlinear regression using the operational model. We describe a procedure using the software application, Prism (GraphPad Software, Inc., San Diego, CA). The analysis yields an estimate of the product of K(obs) and a parameter proportional to efficacy (τ). The estimate of τK(obs) of one agonist, divided by that of another, is a relative measure of K(b) (RA(i)). For any receptor exhibiting constitutive activity, it is possible to estimate a parameter proportional to the efficacy of the free receptor complex (τ(sys)). In this case, the K(b) value of an agonist is equivalent to τK(obs)/τ(sys). Our method is useful for determining the selectivity of an agonist for receptor subtypes and for quantifying agonist-receptor signaling through different G proteins.     

Diet restriction and life history trade-offs in short- and long-lived species of Daphnia

The life-extending effects of diet restriction are well documented. One evolutionary model that accounts for this widespread conservation is the resource allocation model, where the selected individuals are those that can delay reproduction during periods of resource limitation. In this study, we use closely related species of a model organism, Daphnia, with widely divergent lifespans to address the relationship between diet restriction and longevity and assess whether the relationships are owing to trade-offs between reproductive and somatic investment. Specifically, we conducted a common garden experiment and constructed reaction norms for lifespan, fecundity, and body size as a function of food concentration. Our study provides evidence that the short-lived species in our study, D. pulex, shows the classically observed relationship of enhanced lifespan in response to reduced diet intake, but does not divert resources to somatic maintenance at the expense of reproduction during chronic diet restriction. In contrast, we find no evidence that the long-lived species in our study, D. pulicaria, gains any life-extending effects through diet restriction. Combined, our results provide evidence that the resource allocation model is not sufficient to explain the evolution of diet-mediated lifespan plasticity.     

A protein-free medium for the growth of hybridomas and other cells of the immune system

Summary A protein-free medium, termed ABC, has been developed which essentially eliminates the need for serum proteins. ABC supports the long-term growth of murine hybridomas as well as other transformed cells of the immune system. The requirement of hybridoma growth for transferrin has been met by substituting the soluble organo-iron compound, sodium nitroprusside. Substantial improvement in the growth of hybridomas was afforded by the inclusion of 18 trace elements complexed to disodium ethylene diaminetetraacetate (EDTA). The medium was further improved by the inclusion of components not found in Ham's F12 medium or by raising the concentrations of existing low molecular weight components. Murine hybridomas can be cultured routinely in this protein-free medium in an anchorage-independent manner with doubling times generally under 24 h. Visualized on electrophoretic gels, levels of monoclonal antibody taken from those cultures often exceeded 80% of the total protein. The medium was also able to support the growth of HuT 78 and H9 cells as well as certain other transformed cells of the immune system. In addition, normal human peripheral blood lymphocytes, activated with phytohemagglutinin and cultured with 50 U/ml recombinant interleukin 2, could be grown for 2 wk with a 50-fold expansion over input cell number.     

Paradoxical effects of a stress signal on pro- and anti-apoptotic machinery in HTLV-1 tax expressing cells

Adult T-cell leukemia (ATL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) are associated with Human T-cell lymphotropic virus type 1 (HTLV-1) infection. The viral transactivator, Tax is able to mediate the cell cycle progression by targeting key regulators of the cell cycle such as p21/waf1, p16/ink4a, p53, cyclins D1-3/cdk complexes, and the mitotic spindle checkpoint MAD apparatus, thereby deregulating cellular DNA damage and checkpoint control. Genome expression profiling of infected cells exemplified by the development of DNA microarrays represents a major advance in genome-wide functional analysis. Utilizing cDNA microarray analysis, we have observed an apparent opposing and paradoxical regulatory network of host cell gene expression upon the introduction of DNA damage stress signal. We find the apparent induction of cell cycle inhibitors, and pro- as well as anti-apoptotic gene expression is directly linked to whether cells are at either G1, S, or G2/M phases of the cell cycle. Specifically, a G1/S block is induced by p21/waf1 and p16/ink4a, while pro-apoptotic expression at S, and G2/M is associated with caspase activation, and anti-apoptotic gene expression is associated with up regulation of Bcl-2 family member, namely bfl-1 gene. Therefore, the microarray results indicating expression of both pro- and anti-apoptotic genes could easily be explained by the particular stage of the cell cycle. Mechanism and the functional outcome of induction for both pathways are discussed.     

The Wnt antagonist secreted frizzled-related protein-1 is a negative regulator of trabecular bone formation in adult mice

Previous studies have associated activation of canonical Wnt signaling in osteoblasts with elevated bone formation. Here we report that deletion of the murine Wnt antagonist, secreted frizzled-related protein (sFRP)-1, prolongs and enhances trabecular bone accrual in adult animals. sFRP-1 mRNA was expressed in bones and other tissues of +/+ mice but was not observed in -/- animals. Despite its broad tissue distribution, ablation of sFRP-1 did not affect blood and urine chemistries, most nonskeletal organs, or cortical bone. However, sFRP-1-/- mice exhibited increased trabecular bone mineral density, volume, and mineral apposition rate when compared with +/+ controls. The heightened trabecular bone mass of sFRP-1-/- mice was observed in adult animals between the ages of 13-52 wk, occurred in multiple skeletal sites, and was seen in both sexes. Mechanistically, loss of sFRP-1 reduced osteoblast and osteocyte apoptosis in vivo. In addition, deletion of sFRP-1 inhibited osteoblast lineage cell apoptosis while enhancing the proliferation and differentiation of these cells in vitro. Ablation of sFRP-1 also increased osteoclastogenesis in vitro, although changes in bone resorption were not observed in intact animals in vivo. Our findings demonstrate that deletion of sFRP-1 preferentially activates Wnt signaling in osteoblasts, leading to enhanced trabecular bone formation in adults.     

有害疣孢霉Hypomyces perniciosus遗传转化体系的建立及其突变体库的构建

有害疣孢霉Hypomyces perniciosus是引起双孢蘑菇Agaricus bisporus湿泡病的病原真菌,目前其致病分子机理尚不清楚,而高效稳定的遗传转化体系和突变体库构建是挖掘和研究病原菌致病基因的基础和有效手段。因此,本实验以高致病力的有害疣孢霉菌株WH001为研究对象,采用冻融法将双元载体pBHt1转入农杆菌AGL-1中,建立并优化根癌农杆菌介导的遗传转化体系,并利用其构建T-DNA插入突变体库。结果表明有害疣孢霉菌株WH001的潮霉素（Hygromycin,Hyg）耐受浓度为250ng/L,当农杆菌侵染液浓度OD₆₀₀=1,侵染时间为30min,乙酰丁香酮（Acetosyringone,AS）浓度为1.5mg/mL,共培养时间为3d时,转化体系效率最高。然后利用该优化体系构建有害疣孢霉的突变体库,通过PCR检测和形态学鉴定获得若干表型发生改变、稳定遗传的T-DNA插入突变体,与原菌种WH001相比,突变体在菌丝形态、生长速率、色素分泌和致病力等方面发生改变。本研究为进一步挖掘有害疣孢霉未知基因功能、解析生物学性状、探讨致病分子机制奠定基础。     

The Revised Classification of Eukaryotes

This revision of the classification of eukaryotes, which updates that of Adl et al. [J. Eukaryot. Microbiol. 52 (2005) 399], retains an emphasis on the protists and incorporates changes since 2005 that have resolved nodes and branches in phylogenetic trees. Whereas the previous revision was successful in re‐introducing name stability to the classification, this revision provides a classification for lineages that were then still unresolved. The supergroups have withstood phylogenetic hypothesis testing with some modifications, but despite some progress, problematic nodes at the base of the eukaryotic tree still remain to be statistically resolved. Looking forward, subsequent transformations to our understanding of the diversity of life will be from the discovery of novel lineages in previously under‐sampled areas and from environmental genomic information.