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81.
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
82.
In vitro colonization ability of human colon mucosa by exogenous Lactobacillus strains 总被引:1,自引:0,他引:1
Leila-ouassila Sarem-Damerdji Farzin Sarem Luc Marchal Jean-Pierre Nicolas 《FEMS microbiology letters》1995,131(2):133-137
Abstract A 5.4 kb Hind III DNA fragment carrying the gene encoding raw starch-digesting α-amylase (RSDA), has been previously cloned from Bacillus circulans F-2 and expressed in Escherichia coli [Kim et al. (1990) Biochim. Biophys. Acta 1048, 2233–2238]. Interestingly, when the cell extract of E. coli harboring a plasmid carrying this fragment was incubated with l M NaCl, it exhibited about 10 times higher enzyme activity than when assayed without NaCl. Differential zymograms showed two different amylase activities: one for RSDA and the other for a salt-dependent a-amylase (SDA). Even though RSDA activity was detected without NaCl, SDA activity was detected only in high concentrations of NaCl. SDA activity was fully detected at above l M NaCl. Results from subcloning of the genes, fractionation analysis of cell extracts, and immunological assays clearly suggested that the two amylases are genetically distinct and that genes for both enzymes are closely linked on the 5.4 kb DNA fragment. 相似文献
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Identification of the signalling molecules involved in mesoderm formation in amphibian embryos still presents problems. None of the original candidates, such as activin, have been definitively ruled out, and the new factors, such as the nodal-related genes, have come on to the scene. Of the original candidates, activin has been definitively shown to act as a morphogen, whereas bone morphogenetic protein (BMP)-4 has emerged as a ventral inducer and an inhibitor of neural differentiation. The effects of BMP-4 are antagonized by chordin, a molecule related to the product of the Drosophila gene short gastrulation. 相似文献
85.
The metabolism of radiolabeled arachidonic acid (AA) by the intact bovine retina
has been studied. Synthesis of prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs), and incorporation of AA into glycerolipids has been measured by reverse-phase and straight-phase high performance liquid chromatography with flow scintillation detection, and by thin-layer chromatography. AA was actively acylated into glycerolipids, particularly triglycerides, phosphatidylcholine and phosphatidylinositol. AA was also converted to the major PGs, PGF2α, PGE2, PGD2, 6-keto-PGF1α and TXB2, and to the lipoxygenase reaction products, 12-HETE, 5-HETE, and other monohydroxy isomers. Approximately 6% of the radiolabeled AA was converted to eicosanoids. The synthesis of HETEs was inhibited in a concentration-dependent manner (IC50 = 8.3 NM) by nordihydroguaiaretic acid (NDGA). PG synthesis was inhibited by aspirin (10 μM), indomethacin (1 μM) and NDGA (IC50 = 380 nM). Metabolism of AA via lipoxygenase, cyclooxygenase and activation-acylation was inhibited by boiling retinal tissue prior to incubation. These studies demonstrate an active system for the uptake and utilization of AA in the bovine retina, and provide the first evidence of lipoxygenase-mediated metabolism of AA, resulting in the synthesis of mono-hydroxyeicosatetraenoic acids, in the retina. 相似文献
86.
J L Rubenstein J F Nicolas F Jacob 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1984,299(8):271-274
We describe a general technique to inhibit gene expression in eukaryotic cells. The gene we chose to inhibit was the E. coli LacZ gene (encoding beta-galactosidase), which has previously been cloned into a eukaryotic expression vector [1]. This plasmid is called pCH110. We constructed a variant of pCH110 in which we flipped a 2566 base pair 5' fragment of the LacZ gene into the antiparallel orientation. The plasmid containing this mutated LacZ gene is called pNSLacZ (NS signifies non-sense coding sequence). When equal amounts of pCH110 and pNSLacZ are co-transfected into 3T6 mouse fibroblasts, the beta-galactosidase activity is decreased by approximately a factor of ten. Increasing the ratio of pNSLacZ to pCH110 above 1:1 does not appreciably increase the level of inhibition. Next, we prove the specificity of the inhibition by adding a third gene to the transfection mixture. For this purpose, we used pSVneo beta, a plasmid which expresses a phosphotransferase. We found that even when the beta-galactosidase activity was diminished by a factor of 10, the phosphotransferase activity was unaffected. Therefore, we have demonstrated that: the presence of an antiparallel copy of the LacZ gene results in a significant and specific diminution of the LacZ gene's expression; only a fraction of the LacZ gene needs to be in the antiparallel orientation in order to observe this effect. These results suggest that this technique can serve as a tool to decrease the level of gene expression in order to study the function of specific genes, or as a therapeutic manoeuvre in the treatment of disorders of abnormal gene expression. 相似文献
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89.
Yaīr Reisner Gabriel Gachelin Philippe Dubois Jean-François Nicolas Nathan Sharon François Jacob 《Developmental biology》1977,61(1):20-27
Peanut agglutinin (PNA), a lectin specific for terminal d-galactosyl residues, was found to react with embryonal carcinoma cells, but not with their differentiated derivatives. Receptors for PNA were detectable at the surface of all cells of the quasinullipotent F9 line and on only 50% of the multipotent PCC3/A/1 line. The fraction of the PCC3/A/1 population which expresses the F9 antigen was found to be included in the subpopulation carrying the PNA receptors. PNA+ and PNA? subpopulations of PCC3/A/1 were separated by a PNA-mediated reversible agglutination of PNA+ cells with rabbit erythrocytes. These subpopulations were essentially F9+ and F9?, respectively. 相似文献
90.
Oryza sativa L. var. bahia coleoptile cell walls show sufficient autolytic activity for the release into the surrounding medium of amounts up to 60 μg of sugars per mg of dry weight of cell wall. The products released elute in Bio-gel P.2 as mono- and polysaccharides with glucose as the sole component. The polysaccharide component releases tri- and tetrasaccharides on treatment with a glucanase specific for β (1–3) (1–4) linkages in the same proportion as that of the mixed glucan of the cell wall. This supports the hypothesis that the polysaccharide component originates from the cell wall glucan and that autolysis is therefore related to the processes of the loss of rigidity of the cell wall. Nojirimycin (a specific glucanase inhibitor and inhibitor of auxin-induced elongation) decreases autolytic activity of the cell walls, reducing it to 30% of its normal value. Bio-gel P. 2 elution of the products released in autolysis in the presence of nojirimycin shows that only the monosaccharide fraction was affected. 相似文献