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2.
MAJOR CLADES OF THE ANGIOSPERMS 总被引:2,自引:0,他引:2
ROLF DAHLGREN KÅRE BREMER 《Cladistics : the international journal of the Willi Hennig Society》1985,1(4):349-368
Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny. 相似文献
3.
Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution 总被引:1,自引:0,他引:1
In order to study the relationships among mammalian alpha-globin genes, we
have determined the sequence of the 3' flanking region of the human alpha 1
globin gene and have made pairwise comparisons between sequenced
alpha-globin genes. The flanking regions were examined in detail because
sequence matches in these regions could be interpreted with the least
complication from the gene duplications and conversions that have occurred
frequently in mammalian alpha-like globin gene clusters. We found good
matches between the flanking regions of human alpha 1 and rabbit alpha 1,
human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and
horse alpha 1 and goat II alpha. These matches were used to align the
alpha-globin genes in gene clusters from different mammals. This alignment
shows that genes at equivalent positions in the gene clusters of different
mammals can be functional or nonfunctional, depending on whether they
corrected against a functional alpha-globin gene in recent evolutionary
history. The number of alpha-globin genes (including pseudogenes) appears
to differ among species, although highly divergent pseudogenes may not have
been detected in all species examined. Although matching sequences could be
found in interspecies comparisons of the flanking regions of alpha- globin
genes, these matches are not as extensive as those found in the flanking
regions of mammalian beta-like globin genes. This observation suggests that
the noncoding sequences in the mammalian alpha-globin gene clusters are
evolving at a faster rate than those in the beta-like globin gene clusters.
The proposed faster rate of evolution fits with the poor conservation of
the genetic linkage map around alpha-globin gene clusters when compared to
that of the beta-like globin gene clusters. Analysis of the 3' flanking
regions of alpha-globin genes has revealed a conserved sequence
approximately 100-150 bp 3' to the polyadenylation site; this sequence may
be involved in the expression or regulation of alpha-globin genes.
相似文献
4.
INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti… 相似文献
5.
Molecular evolutionary genetics of the cattle-adapted serovar Salmonella dublin. 总被引:4,自引:0,他引:4
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R K Selander N H Smith J Li P Beltran K E Ferris D J Kopecko F A Rubin 《Journal of bacteriology》1992,174(11):3587-3592
An electrophoretic analysis of allelic variation at 24 enzyme loci among 170 isolates of the serovar Salmonella dublin (serotype 1,9,12[Vi]:g,p:-) identified three electrophoretic types (Du 1, Du 3, and Du 4), marking three closely related clones, one of which (Du 1) is globally distributed and was represented by 95% of the randomly selected isolates. All but 1 of 114 nonmotile isolates of serotype 1,9,12:-:- recovered from cattle and swine in the United States were genotypically Du 1. The virulence capsular polysaccharide (Vi antigen) is confined to clone Du 3, which apparently is limited in distribution to France and Great Britain. For all 29 isolates of Du 3, positive signals were detected when genomic DNA was hybridized with a probe specific for the ViaB region, which contains the structurally determinant genes for the Vi antigen; and 23 of these isolates had been serologically typed as Vi positive. In contrast, all 30 isolates of Du 1 tested with the ViaB probe were negative. These findings strongly suggest that the ViaB genes were recently acquired by S. dublin via horizontal transfer and additive recombination. The clones of S. dublin are closely similar to the globally predominant clone (En 1) of Salmonella enteritidis (serotype 1,9,12:g,m:-) in both multilocus enzyme genotype and nucleotide sequence of the fliC gene encoding phase 1 flagellin. Comparative sequencing of fliC has revealed the molecular genetic basis for expression of the p and m flagellar epitopes by which these serovars are distinguished in the Kauffmann-White serological scheme of classification. 相似文献
6.
Mendoza Beltran Angelica Scheel Claus Nordstrøm Fitton Nuala Schmidt Jannick Kløverpris Jesper Hedal 《The International Journal of Life Cycle Assessment》2021,26(8):1570-1585
The International Journal of Life Cycle Assessment - To estimate life cycle impacts from introducing the yield-enhancing inoculant containing the nitrogen-fixing bacterium Bradyrhizobium japonicum... 相似文献
7.
Anti-HIV Pronucleotides: SATE Versus Phenyl as a Protecting Group of AZT Phosphoramidate Derivatives
T. Beltran D. Egron I. Lefebvre C. Périgaud A. Pompon G. Gosselin 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):973-975
Abstract We comparatively studied the decomposition pathways in CEM cell extract of several PHENYL phosphoramidate diesters of AZT. A correlation between anti-HIV activities in TK? cell lines and pharmacokinetic data has been observed. This study would help to design corresponding SATE phosphoramidate diesters which revealed potent anti-HIV properties. 相似文献
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10.
Under natural conditions, plants are subjected to continuous changes of irradiance that drive variations of stomatal conductance to water vapour (gs). We propose a dynamic model to predict the temporal response of gs at the leaf level using an asymmetric sigmoid function with a unique parameter describing time constants for increasing and decreasing gs. The model parameters were adjusted to observed data using Approximate Bayesian Computation. We tested the model performance for (1) instant changes of irradiance; or (2) continuous and controlled variations of irradiance simulating diurnal time courses. Compared with the two mostly used steady‐state models, our dynamic model described daily time courses of gs with a higher accuracy. In particular, it was able to describe the hysteresis of gs responses to increasing/decreasing irradiance and the resulting rapid variations of intrinsic water‐use efficiency. Compared to the mechanistic model of temporal responses of gs by Kirschbaum, Gross & Pearcy, for which time constants were estimated with a large variance, our model estimated time constants with a higher precision. It is expected to improve predictions of water loss and water‐use efficiency in higher scale models by using a small number of parameters. 相似文献