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1.
JUN YOKOYAMA TATSUYA FUKUDA AKIKO YOKOYAMA MASAYUKI MAKI 《Botanical journal of the Linnean Society. Linnean Society of London》2002,138(3):369-380
Morphologically intermediate plants between Weigela hortensis (Siebold & Zucc.) K.Koch and W. maximowiczii (S.Moore) Rehder have been found in Miyagi and Yamagata Pref., northern Japan. Quantitative character analyses of flowers, pollen stainability and molecular analyses indicated that the intermediate plants were hybrids of those two species. This is the first record of an intersectional hybrid with W. maximowiczii (sect. Weigelastrum ) as one of the parent species. The morphological differences among hybrid individuals imply the possibility of backcrosses or formation of second or later generations of hybrids, although those may be quite rare because of a low frequency of viable pollen grains. Causes of hybridization between two distantly-related species in Weigela are discussed. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 369–380. 相似文献
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Of the 39 species composing the Xiphinema americanum group, 14 were described originally from North America and two others have been reported from this region. Many species are very similar morphologically and can be distinguished only by a difficult comparison of various combinations of some morphometric characters. Study of morphometrics of 49 populations, including the type populations of the 39 species attributed to this group, by principal component analysis and hierarchical cluster analysis placed the populations into five subgroups, proposed here as the X. brevicolle subgroup (seven species), the X. americanum subgroup (17 species), the X. taylori subgroup (two species), the X. pachtaicum subgroup (eight species), and the X. lambertii subgroup (five species). 相似文献
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Michael C. Whitlock 《Evolution; international journal of organic evolution》1995,49(2):252-259
The increase in phenotypic variance that occurs in some populations as a result of bottlenecks and founder events can cause a dramatic increase in the probability of a peak shift from one adaptive state to another. Periods of small population size allow drift in the amount of phenotypic variance. Increases in phenotypic variance, coupled with a constant individual fitness function with multiple peaks, can cause the mean fitness landscape to change from bimodal to unimodal, thereby allowing the population's mean phenotype to change deterministically by selection. As the amount of phenotypic variance is returned to an equilibrium state, the multiple peaks reemerge, but the population has moved from one stable state to another. These variance-induced peak shifts allow punctuational evolution from one peak to another at a rate that can be much higher than that predicted by Wright's shifting-balance process alone. 相似文献
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T. S. Cox 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,68(1-2):183-186
Summary The genetic variance among random-mated lines derived from backcrossing (BCgS1 lines) depends upon the backcross generation (g) and the number (n) of BCgF1 plants crossed in generations 1 through g. There is little effect of n on genetic variance for n > 6. The genetic variance among BCgF2-derived lines is greater than that among BCgS1 lines for all g. If either BCgF2-derived or BCgS1 lines are used as a base population for recurrent selection, 8, 16, 32, and 64 BC1F1, BC2F1, BC3F1, and BC4F1 plants, respectively, should be used to avoid loss of donor alleles to drift.Joint contribution of USDA-ARS and Journal Paper No. J-11224 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2471Formerly Research Geneticist, USDA-ARS, Ames, Iowa, USA 相似文献
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Hiroshi Souzu 《生物化学与生物物理学报:生物膜》1980,603(1):13-26
Freeze-thawing of Escherichia coli cells caused a release of cell membrane components such as protein, phospholipids and lipopolysaccharides. A greater amount of release and a lesser extent of cell survival were seen in slow freeze-thawing than in rapid freeze-thawing. Several dehydrogenases in the cells were also freed. The mode of release was also dependent on the rate of freeze-thawing.The materials released by slow freeze-thawing were found to be mostly composed of outer membrane components, whereas the materials released by rapid freeze-thawing contained cytoplasmic as well as outer membrane components. The chemical composition of these fragments differed significantly from that of the original membranes. The relative content of cytoplasmic membrane-bound enzymes in these fragments also differed from that of the cytoplasmic membrane.The fragmentation was assumed to have resulted mainly from the crystallization of external water. In slow freeze-thawing, it was considered that the phase separation of the membrane phospholipid bilayer increased the possibility of outer membrane fragmentation. Rapid freeze-thawing caused cytoplasmic membrane damage to the cells as well as to the outer membrane. In rapid freeze-thawing, the effect of phase separation appeared to be small because of rapid passage through the transition temperatures.The presence of 10% glycerol completely inhibited the release of cellular materials and enzymes. Cell survival was maintained at a high level in the glycerol-treated samples whether freeze-thawed slowly or rapidly. 相似文献
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Peter S. Thuy-Boun Ana Y. Wang Ana Crissien-Martinez Janice H. Xu Sandip Chatterjee Gregory S. Stupp Andrew I. Su Walter J. Coyle Dennis W. Wolan 《Molecular & cellular proteomics : MCP》2022,21(3):100197
The gut microbiota plays an important yet incompletely understood role in the induction and propagation of ulcerative colitis (UC). Organism-level efforts to identify UC-associated microbes have revealed the importance of community structure, but less is known about the molecular effectors of disease. We performed 16S rRNA gene sequencing in parallel with label-free data-dependent LC-MS/MS proteomics to characterize the stool microbiomes of healthy (n = 8) and UC (n = 10) patients. Comparisons of taxonomic composition between techniques revealed major differences in community structure partially attributable to the additional detection of host, fungal, viral, and food peptides by metaproteomics. Differential expression analysis of metaproteomic data identified 176 significantly enriched protein groups between healthy and UC patients. Gene ontology analysis revealed several enriched functions with serine-type endopeptidase activity overrepresented in UC patients. Using a biotinylated fluorophosphonate probe and streptavidin-based enrichment, we show that serine endopeptidases are active in patient fecal samples and that additional putative serine hydrolases are detectable by this approach compared with unenriched profiling. Finally, as metaproteomic databases expand, they are expected to asymptotically approach completeness. Using ComPIL and de novo peptide sequencing, we estimate the size of the probable peptide space unidentified (“dark peptidome”) by our large database approach to establish a rough benchmark for database sufficiency. Despite high variability inherent in patient samples, our analysis yielded a catalog of differentially enriched proteins between healthy and UC fecal proteomes. This catalog provides a clinically relevant jumping-off point for further molecular-level studies aimed at identifying the microbial underpinnings of UC. 相似文献
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Seed output in perennial plant populations is temporally variable and often synchronous over large regions. The similarly complex spatiotemporal dynamics of animal populations have been characterized by the power‐law scaling of the variance in population numbers with mean abundance. Here we show that a large compilation of published reproductive time series exhibits largely invariant mean–variance scaling properties across both angiosperm and conifer tree species. A simple model of seed production in tree stands shows that observed values of the scaling exponent reflect very general aspects of plant ecology and life history as well as the temporal dynamics of seed production. Together, these results suggest that the continuum of reproductive variability and synchrony observed in trees may reflect the influence of a common set of ecological processes. 相似文献
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