Mutational Analysis of Meiotic and Mitotic Centromere Function in Saccharomyces cerevisiae

A centromere (CEN) in Saccharomyces cerevisiae consists of approximately 150 bp of DNA and contains 3 conserved sequence elements: a high A + T region 78-86 bp in length (element II), flanked on the left by a conserved 8-bp element I sequence (PuTCACPuTG), and on the right by a conserved 25-bp element III sequence. We have carried out a structure-function analysis of the element I and II regions of CEN3 by constructing mutations in these sequences and subsequently determining their effect on mitotic and meiotic chromosome segregation. We have also examined the mitotic and meiotic segregation behavior of ARS plasmids containing the structurally altered CEN3 sequences. Replacing the periodic tracts of A residues within element II with random A + T sequences of equal length increases the frequency of mitotic chromosome nondisjunction only 4-fold; whereas, reducing the A + T content of element II while preserving the length results in a 40-fold increase in the frequence of chromosome nondisjunction. Structural alterations in the element II region that do not decrease the overall length have little effect on the meiotic segregation behavior of the altered chromosomes. Centromeres containing a deletion of element I or a portion of element II retain considerable mitotic activity, yet plasmids carrying these same mutations segregate randomly during meiosis I, indicating these sequences to be essential for maintaining attachment of the replicated sister chromatids during the first meiotic division. The presence of an intact element I sequence properly spaced from the element III region is absolutely essential for proper meiotic function of the centromere.     

Regulation and function of the Drosophila segmentation gene fushi tarazu

The Drosophila segmentation gene fushi tarazu (ftz) is expressed in a pattern of seven stripes at the blastoderm stage. Two cis-acting control elements are required for this expression: the zebra element, which confers the striped pattern by mediating the effects of a subset of segmentation genes; and the upstream element, an enhancer element requiring ftz+ activity for its action. Fusion of the upstream element to a basal promoter results in activation of the heterologous promoter in a ftz-dependent striped pattern, supporting the idea that ftz regulates itself by acting through its enhancer. The upstream element can also confer expression patterns similar to that of the homeotic gene Antennapedia, suggesting that a similar element may play a role in the activation of Antennapedia.     

The piggyBac element is capable of precise excision and transposition in cells and embryos of the mosquito, Anopheles gambiae

The piggyBac transposable element was tested for transposition activity in plasmid-based excision and inter-plasmid transposition assays to determine if this element would function in Anopheles gambiae cells and embryos. In the Mos55 cell line, precise excision of the piggyBac element was observed only in the presence of a helper plasmid. Excision occurred at a rate of 1 event per 1000 donor plasmids screened. Precise excision of the piggyBac element was also observed in injected An. gambiae embryos, but at a lower rate of 1 excision per 5000 donor plasmids. Transposition of the marked piggyBac element into a target plasmid occurred in An. gambiae cells at a rate of 1 transposition event per 24,000 donor plasmids. The piggyBac element transposed in a precise manner, with the TTAA target site being duplicated upon insertion, in 56% of transpositions observed, and only in the presence of the piggyBac helper. The remaining transpositions resulted in a deletion of target sequence, a novel observation for the phenomenon of piggyBac element insertion. 'Hot spots' for insertion into the target plasmid were observed, with 25 of 34 events involving one particular site. These results are the first demonstration of the precise mobility of piggyBac in this malaria vector and suggest that the lepidopteran piggyBac transposon is a candidate element for germline transformation of anopheline mosquitoes.     

Identification of a full-size hobo element and deletion-derivatives in Korean populations of Drosophila melanogaster.

We have isolated and characterized several members of the hobo transposable element family from Korean populations of Drosophila melanogaster. All of the Korean lines tested appeared to have 3.0 kb hobo elements and a high copy number of smaller derivatives of the element. To determine whether a 3.0 kb hobo element of these populations is consistent with the role of an autonomous hobo element, we cloned and sequenced this hobo element. Based on the result of the entire DNA sequence, a cloned 3.0 kb element called HKN96, it was found to be the same as a fully-functional 2959 bp HFL1-type sequence. Each small element appeared to have arisen from the HFL1 element by a different internal deletion. A specific 1.7 kb Kh hobo element, which is the most abundant in the Korean lines tested, seems to have originated from the HFL1 hobo element by an internal deletion of 1253 bp by the removal of nucleotides between positions 939 and 2191. The sequences of the Th1 and Th2 elements appeared to be identical to that of the HFL1 with the exception of internal deletions of 1442 bp and 1455 bp removing nucleotides 940-2381 and 923-2377, respectively. Based on the number of TPE repeats, all of the members of the hobo element family in Korean lines tested have three perfect S repeats. The widespread presence of identical copies of the Kh deletion derivative suggests that it might have a role in the regulation of hobo-induced hybrid dysgenesis.     

Studies on the Rate and Site-Specificity of P Element Transposition

A single genetically marked P element can be efficiently mobilized to insertionally mutagenize the Drosophila genome. We have investigated how the structure of the starting element and its location along the X chromosome influenced the rate and location of mutations recovered. The structure of two P[rosy+] elements strongly affected mobilization by the autonomous "Jumpstarter-1" element. Their average transposition rates differed more than 12-fold, while their initial chromosomal location had a smaller effect. The lethal and sterile mutations induced by mobilizing a P[rosy+] element from position 1F were compared with those identified previously using a P[neoR] element at position 9C. With one possible exception, insertion hotspots for one element were frequently also targets of the other transposon. These experiments suggested that the genomic location of a P element does not usually influence its target sites on nonhomologous chromosomes. During the course of these experiments, Y-linked insertions expressing rosy+ were recovered, suggesting that marked P elements can sometimes insert and function at heterochromatic sites.     

中国石蕊科地衣多样性与区系研究

通过实地调查我国华北、 西南等地区的石蕊科地衣多样性,结合前人的研究资料,从物种多样性、 生境、区系成分等多方面对我国石蕊科地衣进行研究.结果显示,我国石蕊科地衣共有5属107种,其中石蕊属(Cladonia)占优势,有94种,占石蕊科地衣总种数的87.9％.共鉴定出山西省新记录8种,云南省新记录种3种.石蕊科地衣生境...     

Influence of nicotine on tissue trace element concentrations and tissue antioxidant defense

Both altered trace element metabolism and cigaret smoking have been proposed to be risk factors for cardiovascular disease (CVD). Thus, it is important to identify the mechanisms by which cigaret smoke alters trace element metabolism. In the present study, serum trace element concentrations were measured in 19 smokers and 13 nonsmokers. In parallel studies, data from rats treated with 50 mg of nicotine over a 21-d period tested the hypothesis that nicotine induced altered trace element metabolism observed in smokers. Serum Cu and Zn concentrations were significantly higher in smokers than in nonsmokers. Serum nicotine concentrations in rats were comparable to those observed in heavy smokers, but serum trace element concentrations were not significantly altered by nicotine treatment. Tissue trace element concentrations were also not markedly affected by nicotine; however, trace element ratios in liver, kidney, lung, and brain were significantly altered by nicotine treatment. In addition, nicotine-treatment resulted in significantly lower liver glutathione concentrations and higher Cu, Zn superoxide dismutase activity than in controls. These data show that a 50-mg infusion of nicotine over 21 d does not produce in rats the serum trace element abnormalities observed in cigaret smokers. However, nicotine did affect the trace element relationships between tissues as well as components of the free radical defense system.     

Effect of digestive site acidity and compatibility on the species, lipopily and bioavailability of iron, manganese and zinc in Prunus persica Batsch and Carthamus tinctorus

The effects of compatibility, that is combination of Prunus persica Batsch (L.) and Carthamus tinctorus (L.), and different acidity of digestive site on the species, lipopily and bioavailability of coordinated complex of iron, manganese, and zinc in medical decoction were studied. In view of octanol, a long-chain alkanol, resembled as the configuration of carbohydrate and adipose in human body, the octanol- and water-solubility were used to define the species of trace element in phytomedicine, to identify the lipopily and bioavailability of trace element, and octanol-water system was adopted to study the distribution of trace element in decoction of P. persica Batsch (L.) (A), C. tinctorus (L.) (B), and combination of medicine A and B (C) in stomach and intestine. The total concentration, water- and octanol-solubility concentration of iron, manganese, and zinc in medicinal material A, B and C or its decoction under gastric and intestinal acidity, were determined respectively by flame atomic absorption spectrometry, analyzed and compared. The compatibility of medicine A and B enhances the extract percent, octanol-solubility concentration, and stability of coordinated complex of iron, manganese, and zinc. Different acidity of digestive site and compatibility of medicines impact on the ligands of iron, manganese, and zinc, then greatly affect the species and its quantification, the lipopily and bioavailability of trace element. Such influence is quite different for different trace element. Such factors, especially the concentration of octanol-solubility trace element, could be the basis of the dosage to avoid trace element overload.     

Use of a mammalian interspersed repetitive (MIR) element in the coding and processing sequences of mammalian genes.

The mammalian interspersed repetitive (MIR) element was amplified in mammals 130 million years ago. The MIR element is at least 260 bp in length and is found in approximately 105 copies in the mammalian genome. We analyzed copies of the MIR element in the DNA of various mammals to determine its relationship to the structure and function of genes, in an attempt to identify specific uses of the MIR element within the mammalian genome. We found that alternative splicing within the acetylcholine receptor gene in humans takes place within the MIR element and results in the incorporation of part of the MIR element into the coding sequence of this gene. Furthermore, the polyadenylation signal (AATAAA) at the 3' end of four different mammalian genes is derived from the MIR element. These uses of the MIR element suggest that other regulatory sequences found within the mammalian genome originated from ancient transposable elements, many of which may no longer be recognizable.     

西瓜果实AGPL1基因启动子的序列分析

利用PCR技术从西瓜嫩叶中扩增出1.2 kb AGPL1基因启动子,通过PlantCARE和PLACE数据库对启动子序列进行生物信息学分析。结果表明,AGPL1启动子具有多个典型的TATA-Box和CAAT-Box等基本元件,以及高水平转录顺式作用元件5UTR Py-rich stretch,光响应元件ACE、ATCC-motif、Box 4、I-Box、Sp1、TCCC-motif、GAG-motif、MNF1,2个赤霉素响应元件GARE-motif、P-box,参与蛋白代谢调节的顺式作用元件O2-site,参与水杨酸反应的顺式作用元件TCA-element,厌氧诱导所需的顺式作用元件ARE、逆境胁迫响应元件TC-rich repeats、生理昼夜节律控制元件circadian等,为研究外源基因在果实中的特异表达提供参考。     

Identification and sequence of a gene required for a developmentally regulated DNA excision in Anabaena

Vegetative cells of the cyanobacterium Anabaena contain an 11 kb DNA element within the coding region of the nifD gene. This element is excised by site-specific recombination between directly repeated 11 bp sequences at each of its ends during differentiation of nitrogen-fixing cells called heterocysts. Site-specific recombination, leading to the same rejoined nifD gene, was observed during propagation in E. coli of a fragment containing the 11 kb element and flanking sequences. An assay for excision of the element in E. coli was developed, based on mini-Mu-lac transposition into the element. Since the 11 kb element lacks an origin of replication, its excision results in loss of lac and conversion of blue colony-forming cells to white on X-gal plates. Insertion and deletion mutagenesis identified a region of the element needed for excision. Mutations in this region could be complemented by a 6 kb fragment containing an open reading frame that runs counter to those of the nif genes, beginning 240 bp from the recombination site.     

Ecological Stoichiometry and Multi-element Transfer in a Coastal Ecosystem

Energy (carbon) flows and element cycling are fundamental, interlinked principles explaining ecosystem processes. The element balance in components, interactions and processes in ecosystems (ecological stoichiometry; ES) has been used to study trophic dynamics and element cycling. This study extends ES beyond its usual limits of C, N, and P and examines the distribution and transfer of 48 elements in 16 components of a coastal ecosystem, using empirical and modeling approaches. Major differences in elemental composition were demonstrated between abiotic and biotic compartments and trophic levels due to differences in taxonomy and ecological function. Mass balance modeling for each element, based on carbon fluxes and element:C ratios, was satisfactory for 92.5% of all element–compartment combinations despite the complexity of the ecosystem model. Model imbalances could mostly be explained by ecological processes, such as increased element uptake during the spring algal bloom. Energy flows in ecosystems can thus realistically estimate element transfer in the environment, as modeled uptake is constrained by metabolic rates and elements available. The dataset also allowed us to examine one of the key concepts of ES, homeostasis, for more elements than is normally possible. The relative concentrations of elements in organisms compared to their resources did not provide support for the theory that autotrophs show weak homeostasis and showed that the strength of homeostasis by consumers depends on the type of element (for example, macroelement, trace element). Large-scale, multi-element ecosystem studies are essential to evaluate and advance the framework of ES and the importance of ecological processes.     

Structure of genes for Hsp30 from the white-rot fungus Coriolus versicolor and the increase of their expression by heat shock and exposure to a hazardous chemical

We isolated and analysed two genomic DNAs that encode the heat-shock protein Hsp30 from Coriolus versicolor. The amino acid sequences substitute only three amino acid substitutions. The promoter regions contain the consensus heat-shock element, a xenobiotic-response element, a stress-response element, and a metal-response element. The levels of mRNAs for Hsp30 increased markedly after exposure of C. versicolor to pentachlorophenol and levels were higher than those after heat shock.     

Measuring fractional forest canopy element cover and openness – definitions and methodologies revisited

Canopy structural parameters are often used to give adequate representation of vegetated ecosystems for various purposes including primary productivity, climate system, water and carbon gas exchanges, and radiation extinction. Canopy structural parameters are usually described using several pseudo‐synonymous terms, often measuring different components of vegetation canopies. Standardization in the definitions has fallen short, leading to confusion of terms even in standard text books making the comparison of historic measures futile. Here we clarify concepts that have been used for fractional canopy element cover and openness measures. The fractional canopy element cover and openness concepts considered are canopy closure, canopy cover, canopy openness, crown closure, crown completeness, crown cover, crown porosity, site openness and tilt openness. New methodologies are presented to obtain large scale fractional canopy element cover and openness measures using hemispherical photography. The new methodologies and variations in definitions of fractional canopy element cover and openness concepts are demonstrated using photographic measurements in complex topography. The results indicate that both fractional canopy element cover and openness parameters can be estimated with a few point‐based measurements using hemispherical photography. Hemispherical photography is therefore less time, labour and resource intensive, as compared to point based measuring techniques of canopy element cover and openness. Most of the commonly and interchangeably used concepts of fractional canopy element cover and openness measures represent physically different structural properties of a vegetated ecosystem.     

Genetic and molecular analysis of the Spm-dependent a-m2 alleles of the maize a locus

The Suppressor-mutator (Spm) transposable element family of maize consists of the fully functional standard Spm (Spm-s) and many mutant elements. Insertion of an Spm element in or near a gene can markedly alter its expression, in some cases bringing the gene under the control of the mechanisms that regulate expression of the element. To gain insight into such mechanisms, as well as to enlarge our understanding of the Spm element's genetic organization, we have analyzed derivatives of a unique Spm insertion at the maize a locus in which the gene is co-expressed and co-regulated with the element. We describe the genetic properties and the structure of the a locus and Spm element in 9 strains (collectively designated the a-m2 alleles) selected by McClintock from the original a-m2 allele for heritable changes affecting either the Spm element or expression of the a gene. Most of the mutations are intra-element deletions within the 8.3-kb Spm element; many alter both Spm function and expression of the gene. Spm controls a gene expression in alleles with internally deleted, transposition-defective Spm elements and element ends contain the target sequences that mediate Spm's ability to activate expression of the gene. We argue that the properties of the a-m2 alleles reflect the operation of an element-encoded positive regulatory mechanism, as well as a negative regulatory mechanism that affects expression of the element, but appears not to be mediated by an element-encoded gene product.