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1.
A revision of Octoknema Pierre is provided, based on morphological data gathered from a study of herbarium specimens and observations in the field. Fourteen species of Octoknema are recognised including six new species: O. bakossiensis Gosline & Malécot, O. belingensis Gosline & Malécot, O. chailluensis Malécot & Gosline, O. kivuensis Gosline & Malécot, O. mokoko Gosline & Malécot and O. ogoouensis Malécot & Gosline. Data are given for four additional poorly known taxa (Octoknema species A, B, C and D).  相似文献   

2.
The accurate identification of taxa of Aotus is essential for 1) the development of precise biomedical assays, 2) the determination of potential illegal traffic of this genus, and 3) conservation. Although many studies have contributed to what we know about the phylogenetics of Aotus, none used a sufficiently large number of samples to clarify its complexity. To address this need, we sequenced 696 base pairs of the mitochondrial cytochrome-oxidase II gene (mtCOII) in 69 specimens of 7 taxa of Aotus. We also analyzed 8 microsatellite loci in 136 individuals of 6 taxa. In contrast to previous studies, we sampled only wild individuals and have a precise geographical origin for each one. The mtDNA results showed that: 1) the northern gray-necked group of Aotus is genetically more homogeneous than the polyphyletic red-necked group of Aotus; 2) the ancestors of Aotus vociferans seem to be the original species candidate for the current Aotus; 3) Aotus azarae azarae and A. a. boliviensis are the most differentiated taxa, likely a result of extreme genetic drift during stasipatric speciation; 4) the first genetic splits found among taxa of Aotus occurred during the Pliocene (or even Miocene) while the most recent ones happened during the Pleistocene, when forest refugia may have played an important role in speciation. The mean number of microsatellite alleles was 3–5.33 alleles per locus. We found some private alleles that could be useful in helping to identify illegal trade, although a larger sample size is needed to ensure that these alleles are really private to the relevant taxa. These new findings increase our understanding of the phylogeny of Aotus and the level of genetic diversity within different taxa of Aotus.  相似文献   

3.
The results of a study of morphological character variability in the populations of R. altaicus s. l., R. sulphureus subsp. exaltatus and R. schmakovii are presented. Univariate and multivariate analysis methods have been applied: a principal components method, discriminant and variance analysis. As a result, two Altai buttercup subspecies have been distinguished in the territory of the Altai mountains (R. altaicus subsp. altaicus, R. altaicus subsp. frigidus), as well as the new taxa R. sulphureus subsp. exaltatus and R. schmakovii  相似文献   

4.
The intron sequence of chloroplast rpS16 and the secondary structure of its pre-mRNA were characterized for the first time in 26 Allium sativum accessions of different ecologo-geographical origins and seven related Allium species. The boundaries and main stem-loop consensus sequences were identified for all six domains of the intron. Polymorphism was estimated for the total intron and its regions. The structural regions of the rpS16 intron proved to be heterogeneous for mutation rate and spectrum. Mutations were most abundant in domains II and IV, and transition predominated in domains I, III, V, and VI. In addition to structural elements and motifs typical for group IIB introns, several Allium-specific micro- and macrostructural mutations were revealed. A 290-bp deletion involving domains III and IV and part of domain V was observed in A. altaicum, A. fistulosum, and A. schoenoprasum. Several indels and nucleotide substitutions were found to cause a deviation of the pre-mRNA secondary structure from the consensus model of group II introns.  相似文献   

5.
Transposable elements (TEs) are being investigated as potential molecular tools in genetic engineering, for use in procedures such as transgenesis and insertional mutagenesis. Naturally active and reconstructed active TEs are both being studied to develop non-viral delivery vehicles. To date, the active elements being used include three Mariner-Like Elements (MLEs). We review below the studies that have investigated the ability of these MLEs to insert a transgene in vertebrate cells.  相似文献   

6.
7.
The genus Cantharellus is known to have a global distribution and to form ectomycorrhizal associations with a diverse set of host plants. Here we describe Cantharellus pseudoformosus as a species new to science with a possible association with Cedrus deodara. ITS and LSU data demonstrated that the material from India is distinct from Cantharellus formosus and other closely related species.  相似文献   

8.
The yeast genes IXR1 and HMO1 encode proteins belonging to the family of chromatin nonhistone proteins, which are able to recognize and bind to irregular DNA structures. The full deletion of gene IXR1 leads to an increase in cell resistance to the lethal action of UV light, γ-rays, and MMS, increases spontaneous mutagenesis and significantlly decreases the level of UV-induced mutations. It was earlier demonstrated in our works that the hmo1 mutation renders cells sensitive to the lethal action of cisplatin and virtually does not affect the sensitivity to UV light. Characteristically, the rates of spontaneous and UV-induced mutagenesis in the mutant are increased. Epistatic analysis of the double mutation hmo1 ixr1 demonstrated that the interaction of these genes in relation to the lethal effect of cisplatin and UV light, as well as UV-induced mutagenesis, is additive. This suggests that the products of genes HMO1 and IXR1 participate in different repair pathways. The ixr1 mutation significantly increases the rate of spontaneous mutagenesis mediated by replication errors, whereas mutation hmo1 increases the rate of repair mutagenesis. In wild-type cells, the level of spontaneous mutagenesis was nearly one order of magnitude lower than that obtained in cells of the double mutant. Consequently, the combined activity of the Hmo1 and the Ixr1 proteins provides efficient correction of both repair and replication errors.  相似文献   

9.
T. C. Hawes 《Polar Biology》2008,31(10):1287-1289
Direct observations of feeding behaviour in Branchinecta gaini are described. B. gaini possess sophisticated food manipulation behaviours, using their abdominal appendages to ‘scrape’ at and carry away food items. Scraping behaviour was employed by animals for both detrital feeding and the cannibalisation of dead conspecifics. In the absence of like observations from other non-raptatory species of Branchinecta, it appears that adults of B. gaini occupy an intermediary position between species that feed exclusively on vegetative and detrital material and those (e.g. B. gigas, B. ferox, B. raptor) that are known to be carnivorous. In an Antarctic context, particularly, specialisation towards carnivory would have little adaptive value, while expansion of diet breadth via increased manipulative and digestive flexibility would, on the other hand, be advantageous. These behaviours, moreover, mean that B. gaini plays an active role in the breakdown and recycling of its own nutrient base.  相似文献   

10.
The eukaryotic transposon Mos1 is a class-II transposable element that moves using a “cut-and-paste” mechanism in which the transposase is the only protein factor required. The formation of the excision complex is well documented, but the integration step has so far received less investigation. Like all mariner-like elements, Mos1 was thought to integrate into a TA dinucleotide without displaying any other target selection preferences. We set out to synthesize what is currently known about Mos1 insertion sites, and to define the characteristics of Mos1 insertion sequences in vitro and in vivo. Statistical analysis can be used to identify the TA dinucleotides that are non-randomly targeted for transposon integration. In vitro, no specific feature determining target choice other than the requirement for a TA dinucleotide has been identified. In vivo, data were obtained from two previously reported integration hotspots: the bacterial cat gene and the Caenorhabditis elegans rDNA locus. Analysis of these insertion sites revealed a preference for TA dinucleotides that are included in TATA or TA × TA motifs, or located within AT-rich regions. Analysis of the physical properties of sequences obtained in vitro and in vivo do not help to explain Mos1 integration preferences, suggesting that other characteristics must be involved in Mos1 target choice.  相似文献   

11.
Hydrogen exchange rates for backbone amide protons of oxidized Pseudomonas aeruginosa cytochrome c-551 (P. aeruginosa cytochrome c) have been measured in the presence of low concentrations of the denaturant guanidine hydrochloride. Analysis of the data has allowed identification of submolecular unfolding units known as foldons. The highest-energy foldon bears similarity to the proposed folding intermediate for P. aeruginosa cytochrome c. Parallels are seen to the foldons of the structurally homologous horse cytochrome c, although the heme axial methionine-bearing loop has greater local stability in P. aeruginosa cytochrome c, in accord with previous folding studies. Regions of low local stability are observed to correspond with regions that interact with redox partners, providing a link between foldon properties and function. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

12.
Based on population analysis of the DRB1, DQA1, DQB1 and TNFA allele frequency distribution patterns, regional features of immunogenetic structure of the population of West Siberia were investigated. Statistically significant linkage disequilibrium within the HLA class II region, as well as between the TNFA and DRB1, DQA1, and DQB1 was demonstrated. Population frequency distribution patterns of two- and multilocus haplotypes were examined.  相似文献   

13.
14.
There are three most important bacterial causative agents of serious infections that could be misused for warfare purposes: Bacillus anthracis (the causative agent of anthrax) is the most frequently mentioned one; however, Fracisella tularensis (causing tularemia) and Yersinia pestis (the causative agent of plague) are further bacterial agents enlisted by Centers for Disease Control and Prevention into the category A of potential biological weapons. This review intends to summarize basic information about these bacterial agents. Military aspects of their pathogenesis and the detection techniques suitable for field use are discussed.  相似文献   

15.
Survey of seven strains determined as Septonema ochraceum (Dothideomycetes, inc. sed.) isolated from pine litter or obtained from public collections revealed three new species, Fusicladium cordae, F. sicilianum (Venturiaceae), Cladophialophora matsushimae (Herpotrichiellaceae) and a cryptic species morphologically identical to Devriesia americana (Teratosphaeriaceae), but phylogenetically distinct. Morphological survey and phylogenetic analysis using nucleotide sequence data from the nuclear ribosomal subunit genes indicate a close relationship within three species colonising pine litter needles, F. cordae, F. pini and F. ramoconidii. F. sicilianum is most related to F. rhodense. C. matsushimae represents a species belonging to one of the lineages of the polyphyletic genus Cladophialophora. None of the strains observed can be classified morphologically as S. ochraceum, of which the type material does not exist.  相似文献   

16.
Following a re-examination of the material treated under Barleria brevispina (Fiori) Hedrén in the recent Flora of Somalia account of the Acanthaceae, it is concluded that two distinct species are involved and Barleria compacta Malombe & I. Darbysh. is described here from north-eastern Somalia. Its affinities and conservation status are discussed.  相似文献   

17.
Ophiostoma species such as O. quercus are the most frequent causal agents of sapstain of freshly felled hardwood timber and pulpwood. Many species are regarded as economically important agents of wood degradation. The aim of this study was to identify a collection of Ophiostoma isolates, resembling O. quercus, found on stained Eucalyptus pulpwood chips in China. DNA sequences of the internal transcribed spacer regions, including the 5.8S region, of the ribosomal DNA, and parts of the β-tubulin and elongation factor-1α genes, revealed that the isolates were not O. quercus. Surprisingly, they represented O. tsotsi, a wound-infesting fungus recently described from hardwoods in Africa. In addition, sequence data from an isolate from agarwood in Vietnam, identified in a previous study as belonging to an unknown Pesotum species, were also shown to represent O. tsotsi. A high level of genetic variability was observed among isolates of both O. quercus and O. tsotsi. This was unexpected and suggests that both species have been present in Asia for a significant amount of time.  相似文献   

18.
19.
A study of the 26 Cyperaceae published in G. Raddi’s Agrostografia brasiliensis is presented. Several new synonyms and a re-evaluation of some taxa described by G. Raddi are proposed. The first citation of Fimbristylis pilosa Vahl for Brazil is reported. The new combination, Pleurostachys pilulifera (Bertol.) Longhi-Wagner, Baldini & A. C. Araújo is made.  相似文献   

20.
Hsc/Hsp70-interacting protein (HIP) is a rapidly evolving Hsp70 cofactor. Analyses of multiple Drosophila species indicate that the HIP gene is duplicated only in D. melanogaster. The HIP region, in fact, contains seven distinctly evolving duplicated genes. The regional duplication occurred in two steps, fixed rapidly, and illustrates multiple modes of duplicate gene evolution. HIP and its duplicate HIP-R are adaptively evolving in a manner unique to the region: they exhibit elevated divergence from other drosophilids and low polymorphism within D. melanogaster. HIP and HIP-R are virtually identical, share polymorphisms, and are subject to gene conversion. In contrast, two other duplicate genes in the region, CG33221 and GP-CG32779, are pseudogenes, and the chimeric gene Crg1 is subject to balancing selection. HIP and HIP-R are evolving rapidly and adaptively; however, positive selection is not sufficient to explain the molecular evolution of the region as a whole. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

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