基于形态性状的淫羊藿属（小檗科）的分支分析

小檗科（Berberidaceae）淫羊藿属（Epimedium Linn.）植物全世界约有55种,中国分布有44种,其余种类则分布于东亚、克什米尔、北非和高加索等地。该属植物具有复杂的形态学变异（例如：单叶、一回三出复叶、二回三出复叶,花茎具两叶、三叶或一叶,花瓣无距、有距、距多样式等）,导致仅依靠直观判断不能对该属系统进行划分。李超等[1]采用数量分类法对该属55种植物的分类结果多数与Stearn[2]25-26和王悦云等[3]的研究结果一致,但部分种类的分类仍存异议,例如：Sect.     

Decatenation checkpoint‐defective melanomas are dependent on PI3K for survival

Melanoma cell lines are commonly defective for the G2‐phase cell cycle checkpoint that responds to incomplete catenation of the replicated chromosomes. Here, we demonstrate that melanomas defective for this checkpoint response are less sensitive to genotoxic stress, suggesting that the defective cell lines compensated for the checkpoint loss by increasing their ability to cope with DNA damage. We performed an siRNA kinome screen to identify kinases responsible and identified PI3K pathway components. Checkpoint‐defective cell lines were three‐fold more sensitive to small molecule inhibitors of PI3K. The PI3K inhibitor PF‐05212384 promoted apoptosis in the checkpoint‐defective lines, and the increased sensitivity to PI3K inhibition correlated with increased levels of activated Akt. This work demonstrates that increased PI3K pathway activation is a necessary adaption for the continued viability of melanomas with a defective decatenation checkpoint.     

Nuclear magnetic resonance studies of the location and function of plant nutrients in vivo

The cytoplasmic and vacuolar pools of ammonium, inorganic phosphate and potassium can be studied non-invasively in plant tissues using high resolution nuclear magnetic resonance spectroscopy. The techniques that allow these pools to be discriminated in vivo are described and their application to plants is reviewed with reference to the phosphorus, nitrogen and potassium nutrition of root tissues.     

A field test for host fruit odour discrimination and avoidance behaviour for Rhagoletis pomonella flies in the western United States

Prezygotic isolation due to habitat choice is important to many models of speciation-with-gene-flow. Habitat choice is usually thought to occur through positive preferences of organisms for particular environments. However, avoidance of non-natal environments may also play a role in choice and have repercussions for post-zygotic isolation that preference does not. The recent host shift of Rhagoletis pomonella (Diptera: Tephritidae) from downy hawthorn, Crataegus mollis, to introduced apple, Malus domestica, in the eastern United States is a model for speciation-with-gene-flow. However, the fly is also present in the western United States where it was likely introduced via infested apples ≤ 60 years ago. R. pomonella now attacks two additional hawthorns in the west, the native C. douglasii (black hawthorn) and the introduced C. monogyna (English ornamental hawthorn). Flight tunnel tests have shown that western apple-, C. douglasii- and C. monogyna-origin flies all positively orient to fruit volatile blends of their respective natal hosts in flight tunnel assays. Here, we show that these laboratory differences translate to nature through field-trapping studies of flies in the state of Washington. Moreover, western R. pomonella display both positive orientation to their respective natal fruit volatiles and avoidance behaviour (negative orientation) to non-natal volatiles. Our results are consistent with the existence of behaviourally differentiated host races of R. pomonella in the west. In addition, the rapid evolution of avoidance behaviour appears to be a general phenomenon for R. pomonella during host shifts, as the eastern apple and downy hawthorn host races also are antagonized by non-natal fruit volatiles.     

Effect of sodium channel abundance on Drosophila development, reproductive capacity and aging

The voltage-gated Na (+) channels (VGSC) are complex membrane proteins responsible for generation and propagation of the electrical signals through the brain, the skeletal muscle and the heart. The levels of sodium channels affect behavior and physical activity. This is illustrated by the maleless mutant allele (mle (napts)) in Drosophila, where the decreased levels of voltage-gated Na(+) channels cause temperature-sensitive paralysis. Here, we report that mle (napts) mutant flies exhibit developmental lethality, decreased fecundity and increased neurodegeneration. The negative effect of decreased levels of Na(+) channels on development and ts-paralysis was more pronounced at 18 and 29°C than at 25°C, suggesting particular sensitivity of the mle (napts) flies to temperatures above and below normal environmental conditions. Similarly, longevity of mle (napts) flies was unexpectedly short at 18 and 29°C compared with flies heterozygous for the mle (napts) mutation. Developmental lethality and neurodegeneration of mle (napts) flies was partially rescued by increasing the dosage of para, confirming a vital role of Na(+) channels in development, longevity and neurodegeneration of flies and their adaptation to temperatures.     

Histone H4K20 tri‐methylation at late‐firing origins ensures timely heterochromatin replication

Among other targets, the protein lysine methyltransferase PR‐Set7 induces histone H4 lysine 20 monomethylation (H4K20me1), which is the substrate for further methylation by the Suv4‐20h methyltransferase. Although these enzymes have been implicated in control of replication origins, the specific contribution of H4K20 methylation to DNA replication remains unclear. Here, we show that H4K20 mutation in mammalian cells, unlike in Drosophila, partially impairs S‐phase progression and protects from DNA re‐replication induced by stabilization of PR‐Set7. Using Epstein–Barr virus‐derived episomes, we further demonstrate that conversion of H4K20me1 to higher H4K20me2/3 states by Suv4‐20h is not sufficient to define an efficient origin per se, but rather serves as an enhancer for MCM2‐7 helicase loading and replication activation at defined origins. Consistent with this, we find that Suv4‐20h‐mediated H4K20 tri‐methylation (H4K20me3) is required to sustain the licensing and activity of a subset of ORCA/LRWD1‐associated origins, which ensure proper replication timing of late‐replicating heterochromatin domains. Altogether, these results reveal Suv4‐20h‐mediated H4K20 tri‐methylation as a critical determinant in the selection of active replication initiation sites in heterochromatin regions of mammalian genomes.     

Sindbis virus replication, is insensitive to rapamycin and torin1, and suppresses Akt/mTOR pathway late during infection in HEK cells

Genetically engineered Sindbis viruses (SIN) are excellent oncolytic agents in preclinical models. Several human cancers have aberrant Akt signaling, and kinase inhibitors including rapamycin are currently tested in combination therapies with oncolytic viruses. Therefore, it was of interest to delineate possible cross-regulation between SIN replication and PI3K/Akt/mTOR signaling. Here, using HEK293T cells as host, we report the following key findings: (a) robust SIN replication occurs in the presence of mTOR specific inhibitors, rapamycin and torin1 or Ly294002 – a PI3K inhibitor, suggesting a lack of requirement for PI3K/Akt/mTOR signaling; (b) suppression of phosphorylation of Akt, mTOR and its effectors S6, and 4E-BP1 occurs late during SIN infection: a viral function that may be beneficial in counteracting cellular drug resistance to kinase inhibitors; (c) Ly294002 and SIN act additively to suppress PI3K/Akt/mTOR pathway with little effect on virus release; and (d) SIN replication induces host translational shut off, phosphorylation of eIF2α and apoptosis. This first report on the potent inhibition of Akt/mTOR signaling by SIN replication, bolsters further studies on the development and evaluation of engineered SIN genotypes in vitro and in vivo for unique cytolytic functions.     

Computer simulation of synchronization of Na/K pump molecules

The behavior of Na/K pump currents when exposed to an oscillating electric field is studied by computer simulation. The pump current from a single pump molecule was sketched based on previous experimental results. The oscillating electric field is designed as a symmetric, dichotomous waveform varying the membrane potential from −30 to −150 mV around the membrane resting potential of −90 mV. Based on experimental results from skeletal muscle fibers, the energy needed to overcome the electrochemical potentials for the Na and K-transports are calculated in response to the field’s two half-cycles. We found that a specially designed oscillating electric field can eventually synchronize the pump molecules so that all the individual pumps run at the same pumping rate and phase as the field oscillation. They extrude Na ions during the positive half-cycle and pump in K ions during the negative half-cycle. The field can force the two ion-transports into the corresponding half-cycles, respectively, but cannot determine their detailed positions. In other words, the oscillating electric field can synchronize pumps in terms of their pumping loops but not at a specific step in the loop. These results are consistent with our experimental results in measurement of the pump currents.     

Species co-existence and character divergence across carnivores

Co-occurring species might be morphologically similar because they are adapted to the same environment, or morphologically dissimilar to minimize competition. We use sister species comparisons to evaluate the relationship between morphological disparity and regional patterns of co-occurrence across carnivores. Up to 63% of the variation in range overlap can be explained by morphological divergence in dentition. Species that differ more in carnassial tooth length overlap more in their geographical range. Carnassials are the primary teeth associated with food processing, and hence difference in carnassial size may be a good indicator of difference in resource use. We suggest this pattern is consistent with competition in sympatry driving ecological character displacement, or competitive exclusion among ecologically similar species. Our study uses newly available data on global distributions, morphology and phylogeny, and is the first to demonstrate a close relationship between morphological disparity and co-occurrence at a regional scale encompassing multiple communities.