Rapid transfer of low copy-number episomal plasmids fromSaccharomyces cerevisiae to Escherichia coli by electroporation

A simple and reproducible method for transferring low copy-number episomal plasmids from yeast toEscherichia coli has been developed. Although slightly more time-consuming than direct transfer methods, which are effective with high copy number plasmids, the method is significantly faster than methods that require purification of yeast DNA. Plasmid DNA is released from yeast cells during brief treatments involving grinding with glass beads and heating. The treated yeast are cooled, electrocompetentE. coli is added, the mixture is electroporated, and transformants are selected using standard conditions forE. coli electrotransformation. The procedure typically yields sufficient transformants for most applications.     

Some improvements in the quality of NAA procedures and the reliability of the results

After considering the need for quality control in NAA, the concept of quality in NAA procedures themselves is discussed, and some important factors identified. Two approaches to improve quality are then described in more detail. The first concerns the unique ability of NAA using different isotopic reactions and different modes (INAA/RNAA) to provide independent data sets in the same laboratory, thus allowing internal validation or crosschecking. The second discusses the need for chemical yield measurements in RNAA and the advantages of the radioisotopic tracer technique. Some recent advances and further possibilities for this use of tracers are listed.     

PHYLOGENETIC RELATIONSHIPS WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA) INFERRED FROM CLADISTIC ANALYSIS BASED ON MORPHOLOGICAL DATA1

A cladistic analysis was used to deduce the phylogenetic relationships within the colonial Volvocales. Forty-one pairs of characters related to gross morphology and ultrastructure of vegetative colonies as well as asexual and sexual reproduction were analyzed based on parsimony, using the PAUP 3.0 computer program, for 25 species belonging to nine volvocacean and goniacean genera of the colonial Volvocales. Chlamydomonas reinhardtii Dangeard was the outgroup. The strict consensus tree indicated the presence of two monophyletic groups, one composed of all the volvocacean species analyzed in this study and the other containing the goniacean species except for the four-celled species Gonium sociale (Dujardin) Warming. In addition, these two groups constitute a large monophyletic group, to which G. sociale is a sister group. A new combination Tetrabaena socialis (Dujardin) Nozaki et Itoh and a new family Tetrabaenaceae Nozaki et Itoh are thus proposed for G. sociale. In addition, the analysis suggests that the volvocacean genera Eudorina and Pleodorina are paraphyletic groups, respectively, and that the monotypic genus Yamagishiella has no autapomorphic characters and represents primitive features of the anisogamous and oogamous genera of the Volvocaceae. Phylogenetic relationships within the Volvocaceae and the Goniaceae, as well as the various modes of sexual reproduction exhibited by these organisms, are discussed on the basis of the analysis.     

长白山站的研究数据库管理系统

长白山站的研究数据库管理系统翟永华,赵士洞（中国科学院沈阳应用生态研究所１１００１５）Ｄａｔｅ－ＢａｓｅＭａｎａｇｅｍｅｎｔＳｙｓｔｅｍｉｎＣｈａｎｇｂａｉｓｈａｎＦｏｒｅｓｔＥｃｏｓｙｓｔｅｍＲｅｓｅａｒｃｈＳｔａｔｉｏｎ．￥ＺｈａｉＹｏｎｇｈｕａ...     

Cytogenetical localization of Zygotic hybrid rescue (Zhr), a Drosophila melanogaster gene that rescues interspecific hybrids from embryonic lethality

Hybrid females from crosses between Drsophila melanogaster males and females of its sibling species, D. simulans, D. mauritiana, or D. sechellia die as embryos. This lethality is believed to be caused by incompatibility between the X chromosome of D. melanogaster and the maternal cytoplasm. Zygotic hybrid rescue (Zhr) prevents this embryonic lethality and has been cytogenetically mapped to a proximal region of the X chromosome of D. melanogaster, probably in the centromeric heterochromatin. We have carried out high resolution cytological mapping of Zhr using deficiencies and duplications of the X heterochromatin. Deletions of the Zhr ⁺ gene from the hybrid genome exhibit the Zhr phenotype. On the contrary, addition of the wild-type gene to the hybrid genome causes embryonic lethality, regardless of sex. The Zhr locus has been narrowed down to the region covered by Dp(1;f)1162 but not covered Dp(1;f)1205, a chromosome carrying a duplication of heterochromatin located slightly distal to the In(1)sc ⁸ heterochromatic breakpoint.     

Wave-separation in complex systems. Application to brain-signals

A departure from single-system dynamics, that may arise in characterizing self-organized dynamics of complex systems, is dealt with by using the Karhunen-Loève expansion of the trajectory matrix to decompose an experimental signal in a sum of spectral features. For an electroencephalographic -signal, a separation of waves and extraction of additive sub-signals are achieved, each sub-signal covering a well-bounded and physiologically meaningful frequency range. From the subsignals, an attractor that vanishes on phase-randomizing the data is characterized, under conditions where none was found for the recorded signal.     

Molecules and Morphology,Phylogenetics and Genetics

Various explanations can be offered for the incongruence between phylogenetic hypotheses resulting from morphological and molecular data sets. Of these, the possibility that incongruence may result from the mutation of major morphogenetic genes leading to dramatic morphological divergence unaccompanied by equivalent change of the phylogenetic marker molecule(s) used is discussed in detail. As evidence for this hypothesis, several examples for such incongruence are surveyed. It seems possible that in many cases the genetic basis of the morphological characters responsible for the incongruence found may be simple, and that the genes involved may be homologous to genes known from mutant systems. It is suggested that: 1. the systematic documentation of incongruence between molecular and morphological phylogenies may help to assess the frequency of evolutionary change through the mutation of major morphogenetic genes, and that 2. the identification of major morphological characters distinguishing closely related taxa with mutant phenotypes known from mutant systems eventually may allow an experimental approach to the problem of evolutionary change resulting from major genes. Natural taxa suspected to be the result of such processes could be changed morphologically through transformation with the relevant genes.     

The unexpected long period of elevated CH4 emissions from an inundated fen meadow ended only with the occurrence of cattail (Typha latifolia)

Drainage and agricultural use transform natural peatlands from a net carbon (C) sink to a net C source. Rewetting of peatlands, despite of high methane (CH₄) emissions, holds the potential to mitigate climate change by greatly reducing CO₂ emissions. However, the time span for this transition is unknown because most studies are limited to a few years. Especially, nonpermanent open water areas often created after rewetting, are highly productive. Here, we present 14 consecutive years of CH₄ flux measurements following rewetting of a formerly long-term drained peatland in the Peene valley. Measurements were made at two rewetted sites (non-inundated vs. inundated) using manual chambers. During the study period, significant differences in measured CH₄ emissions occurred. In general, these differences overlapped with stages of ecosystem transition from a cultivated grassland to a polytrophic lake dominated by emergent helophytes, but could also be additionally explained by other variables. This transition started with a rapid vegetation shift from dying cultivated grasses to open water floating and submerged hydrophytes and significantly increased CH₄ emissions. Since 2008, helophytes have gradually spread from the shoreline into the open water area, especially in drier years. This process was periodically delayed by exceptional inundation and eventually resulted in the inundated site being covered by emergent helophytes. While the period between 2009 and 2015 showed exceptionally high CH₄ emissions, these decreased significantly after cattail and other emergent helophytes became dominant at the inundated site. Therefore, CH₄ emissions declined only after 10 years of transition following rewetting, potentially reaching a new steady state. Overall, this study highlights the importance of an integrative approach to understand the shallow lakes CH₄ biogeochemistry, encompassing the entire area with its mosaic of different vegetation forms. This should be ideally done through a study design including proper measurement site allocation as well as long-term measurements.     

Evolutionary rescue under demographic and environmental stochasticity

Populations suffer two types of stochasticity: demographic stochasticity, from sampling error in offspring number, and environmental stochasticity, from temporal variation in the growth rate. By modelling evolution through phenotypic selection following an abrupt environmental change, we investigate how genetic and demographic dynamics, as well as effects on population survival of the genetic variance and of the strength of stabilizing selection, differ under the two types of stochasticity. We show that population survival probability declines sharply with stronger stabilizing selection under demographic stochasticity, but declines more continuously when environmental stochasticity is strengthened. However, the genetic variance that confers the highest population survival probability differs little under demographic and environmental stochasticity. Since the influence of demographic stochasticity is stronger when population size is smaller, a slow initial decline of genetic variance, which allows quicker evolution, is important for population persistence. In contrast, the influence of environmental stochasticity is population-size-independent, so higher initial fitness becomes important for survival under strong environmental stochasticity. The two types of stochasticity interact in a more than multiplicative way in reducing the population survival probability. Our work suggests the importance of explicitly distinguishing and measuring the forms of stochasticity during evolutionary rescue.