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31.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
32.
Light and Electron Microscopic Observations of Gametogenesis in Hastigerina pelagica (Foraminifera)*
M. SPINDLER O. R. ANDERSON C. HEMLEBEN A. W. H. B 《The Journal of eukaryotic microbiology》1978,25(4):427-433
SYNOPSIS. During gametogenesis mother individuals of Hastigerina pelagica (d'Orbigny) undergo significant morphological changes. Thirty h before gamete release, the cytoplasm changes from pale orange to bright red, possibly due to transport of stored lipids from the inner region to more peripheral parts of the cytoplasm. During the next 10 to 15 h the bubble capsule which surounds the calcareous shell is discarded. After all bubbles have disappeared, the individual sheds its spines by resorbing the spine bases close to the shell surface. A single mother nucleus divides into some hundreds of thousands of gamete nuclei within a span of ~ 20 h. A bulge of cytoplasm is extruded from the aperture and increases in size during the next 5 to 10 h. This bulge consists of cytoplasmic strands in which gametes and spherical bodies are embedded. The gametes and spherical bodies mature and are released during the afternoon and early evening. The gametes have 2 unequal acronematic flagella. A previously undescribed structure in foraminiferal reproduction is the spherical body which consists of a large vacuole surrounded by a thin cytoplasmic layer in which several nuclei, various typical cell organelles and multiple flagella are present. The spherical bodies are believed to play a role as receptacles of waste material, possibly including residual digestive enzymes, thereby protecting the gametes from lysis during the reproductive process. Fusion of gametes and further development into the next generation have not been observed. 相似文献
33.
D. M. W. ANDERSON G. PINTO 《Botanical journal of the Linnean Society. Linnean Society of London》1980,80(1):85-89
The variation in chemical composition of 15 specimens of the gum exudate from Acacia karroo Hayne, obtained from four different African locations, has been investigated. The range of analytical values found (e.g., specific rotation + 36° to + 67°; uronic acid 10.3 to 18.1%; rhamnose 4 to 10%) reflect the well-known variability of this Acacia species. The major analytical difference concerns the unusually wide range of molecular weights observed, i.e., 1.5 × 105 to 48 × 105. The material of highest molecular weight, from trees infested with Cerambycid beetles, is consumed by bush-babies (Galagidae). 相似文献
34.
Cultured chick embryo fibroblasts derived from skin and skeletal muscle exhibit hyaluronidase activity both associated with the cell layer and secreted into the medium. Although both forms of the enzyme have a number of similar characteristics (R.W. Orkin and B.P. Toole, 1980, J. Biol. CHem. 255), they differ in thermal stability at neutral pH and in behavior on ion-exchange chromatography. Both forms of the enzyme are equally stable at acidic pH for long intervals, but the cell-associated hyaluronidase is significantly less stable than the secreted froms at neutral pH and at temperatures more than or equal to 30 degrees C. Neither the presence of proteases nor inhibitors of hyaluronidase appear to be involved in the cell-asspcoated enzyme. Chromatography of the two forms of hyaluronidase on carboxymethyl cellulose reveals that most (60-90 percent) of the secreted form of the enzyme elutes at a lower ionic strength than the cell- associated enzyme. Treatment of the secreted form of hyaluronidase with neuraminidase shifts its elution profile on carboxymethyl cellulose toward that of the cell-associated form, and also decreases its thermal stability at neutral pH. In contrast, treatment of the secreted form of hyaluronidase with alkaline phosphatase has no detectable effect. These data suggest that the secreted hyaluronidase differs from the cellular form in possessing additional sialic acid residues which endow the former with increased stability in the extracellular milieu. 相似文献
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Direct enumeration of Escherichia coli biotype 1 in foods within 24 h has been achieved by a development of the method of Delaney, McCarthy & Grasso (1962) which is based on the production of indole at 44°. Indole positive E. coli growing at this temperature on a cellulose acetate membrane overlaying tryptone bile agar can be demonstrated. Characterization of 555 indole positive colonies from 843 samples of food showed that 95% were E. coli biotype 1 and a further 3·4% were 'faecal coliforms'. Anaerogenic and non-lactose fermenting E. coli are detected and the significance of these strains is discussed. 相似文献
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