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101.
Nitrogen control in cyanobacteria 总被引:18,自引:2,他引:18
102.
Forbes SH; Hogg JT; Buchanan FC; Crawford AM; Allendorf FW 《Molecular biology and evolution》1995,12(6):1106-1113
We compared genotypes at eight (AC)n microsatellite loci in domestic sheep
(Ovis aries) and wild Rocky Mountain bighorn sheep (O. canadensis). The
domestic sheep had greater genetic variation, higher allele-size variances,
and larger allele sizes than the wild sheep. Accumulating evidence from
higher taxonomic comparisons shows that these parameters are biased if
microsatellite loci are selected in one taxon and used in another. Our
results demonstrate similar biases between congeneric species. We compared
standard measures of genetic variation, differentiation, and distance
within and between species (H, D, FST) to newer measures based on
allele-size variance (SW, SB, RST). The size-based distances better
detected species-level divergence, but standard measures better
distinguished allopatric populations. Empirical calibration of these
measures at the subspecies level is needed to establish their useful
ranges.
相似文献
103.
A plasmid library of Acinetobacter calcoaceticus HindIII fragments was
constructed, and clones that complemented an Escherichia coli pabA mutant
were selected. Plasmids containing a 3.9-kb fragment of A. calcoaceticus
DNA that also complemented E. coli trpD and trpC-(trpF+) mutants were
obtained. We infer that complementation of E. coli pabA mutants was the
result of the expression of the amphibolic anthranilate-
synthase/p-aminobenzoate-synthase glutamine-amidotransferase gene and that
the plasmid insert carried the entire trpGDC gene cluster. In E. coli
minicells, the plasmid insert directed the synthesis of polypeptides of
44,000, 33,000, and 20,000 daltons, molecular masses that are consistent
with the reported molecular masses of phosphoribosylanthranilate
transferase, indoleglycerol-phosphate synthase, and anthranilate-synthase
component II, respectively. A 3,105- bp nucleotide sequence was determined.
Comparison of the A. calcoaceticus trpGDC sequences with other known trp
gene sequences has allowed insight into (1) the evolution of the amphibolic
trpG gene, (2) varied strategies for coordinate expression of trp genes,
and (3) mechanisms of gene fusions in the trp operon.
相似文献
104.
Bellis M; Jubier-Maurin V; Dod B; Vanlerberghe F; Laurent AM; Senglat C; Bonhomme F; Roizes G 《Molecular biology and evolution》1987,4(4):351-363
The presence of the L1 sequences, L1Md4 next to the pseudogene beta h3 and
I12 found in the twelfth intron of the albumin gene, in certain strains of
laboratory mice but not of others has led to the suggestion that these
sequences were recent insertions into the Mus mus domesticus genome. To be
sure that they are really recent insertions and not relics of an ancestral
chromosome, we investigated the presence or absence of these sequences in
populations of wild mice belonging to the semispecies M. m. domesticus and
M. m. musculus as well as in other species of the genus Mus and in related
murids. The sequence I12 in the albumin gene was found in 34% of the
chromosomes of the wild mice belonging to M. m. domesticus and to a lesser
extent (6%) in M. m. musculus. Of 114 M. m. domesticus chromosomes, L1Md4
was found in only nine, seven of which came from the same locality. Its
presence was associated with the haplotype Hbbp, which is relatively rare
in European populations of M. musculus. Since there was no evidence for the
presence of these two L1 sequences in more distantly related species, we
conclude that they are recent insertions in the M. musculus genome.
相似文献
105.
B Chevassus JM Blanc P Bergot L Casenave AM Escaffre F Hérioux N Kaushik R Lanneberre 《遗传、选种与进化》1979,11(1):79-92
106.
Bassi AM Romano P Mangini S Colombo M Canepa C Nanni G Casu A 《Journal of biomedical science》2005,12(3):457-466
Summary We analysed the action, in rats in vivo, of the protein isoprenylation inhibitor perillyl alcohol (POH) and that of vitamin A, alone or in association, on m-RNA and protein expression of farnesyltransferases (FTases α and β subunits) and their protein substrates RhoA and RhoB, in isolated hepatocytes. Combined administration of POH and vitamin A induced a sharp decrease in FTase α protein after 96 h, suggesting an involvement not only of farnesyltransferases but also of geranylgeranyltransferases, which share the FTase α protein. FTase β protein did not decrease. POH plus vitamin A, in contrast with POH or vitamin A alone, induced a decrease in RhoB protein, probably because of different cleavages. No modification was observed in RhoA protein. Vitamin A alone increased RhoB m-RNA and protein expression. As one of the functions of RhoB is cell polarisation, these data support our previous hypothesis of a polarised transport of vitamin A from hepatocytes to hepatic stellate cells. As the behaviours of m-RNAs and proteins in this study were often different, cytoplasmic metabolic pathways must be considered for the parameters studied. The behaviour of Rho B, which is thought to have an antioncogene function, is discussed in view of its isoprenylated forms in the membranes. These preliminary findings stress the need, when studying the association of two isoprenoids in cancer therapy, to consider normal as well as tumour-bearing animals. 相似文献
107.
108.
Reduction of conjugal transfer efficiency by three restriction activities of Anabaena sp. strain PCC 7120. 总被引:7,自引:0,他引:7 下载免费PDF全文
J Elhai A Vepritskiy A M Muro-Pastor E Flores C P Wolk 《Journal of bacteriology》1997,179(6):1998-2005
The efficiency of conjugal transfer of plasmids from Escherichia coli to the cyanobacterium Anabaena sp. strain PCC 7120 was quantitated as a function of the number of restriction sites for the restriction enzymes carried by the recipient. In addition to the previously recognized isoschizomers of AvaI and AvaII, PCC 7120 was found to possess an isoschizomer of AvaIII. Plasmids modified in E. coli with methylases that protect in vitro against restriction by the three enzymes were transferred with high efficiency, nearly independent of the number of restriction sites on the plasmid. Plasmids left unprotected against one of the three restriction enzymes were transferred with lower efficiencies. For low numbers of sites, the efficiency of conjugal transfer decreased as an exponential function of the number of unprotected sites. The methods presented may be used to increase the efficiency of conjugal transfer into restriction-competent bacteria. 相似文献
109.
Lotus corniculatus nodulation specificity is changed by the presence of a soybean lectin gene 总被引:5,自引:0,他引:5 下载免费PDF全文
Plant lectins have been implicated as playing an important role in mediating recognition and specificity in the Rhizobium-legume nitrogen-fixing symbiosis. To test this hypothesis, we introduced the soybean lectin gene Le1 either behind its own promoter or behind the cauliflower mosaic virus 35S promoter into Lotus corniculatus, which is nodulated by R. loti. We found that nodulelike outgrowths developed on transgenic L. corniculatus plant roots in response to Bradyrhizobium japonicum, which nodulates soybean and not Lotus spp. Soybean lectin was properly targeted to L. corniculatus root hairs, and although infection threads formed, they aborted in epidermal or hypodermal cells. Mutation of the lectin sugar binding site abolished infection thread formation and nodulation. Incubation of bradyrhizobia in the nodulation (nod) gene-inducing flavonoid genistein increased the number of nodulelike outgrowths on transgenic L. corniculatus roots. Studies of bacterial mutants, however, suggest that a component of the exopolysaccharide surface of B. japonicum, rather than Nod factor, is required for extension of host range to the transgenic L. corniculatus plants. 相似文献
110.
Mutational and kinetic analysis of basic amino acid transport in the cyanobacterium Synechocystis sp. PCC 6803 总被引:4,自引:0,他引:4
Two nitrogen-deregulated mutants of Phanerochaete chrysosporium, der8-2 and der8-5, were isolated by subjecting wild type conidia to gamma irradiation, plating on Poly-R medium containing high levels of nitrogen, and identifying colonies that are able to decolorize Poly-R. The mutants showed high levels of ligninolytic activity (14C-synthetic lignin 14CO2), and lignin peroxidase, manganese peroxidase and glucose oxidase activities in both low nitrogen (2.4 mM) and high nitrogen (24 mM) media. The wild type on the otherhand displayed these activities in low nitrogen medium but showed little or no activities in high nitrogen medium. Fast protein liquid chromatographic analyses showed that the wild type as well as the der mutants produce three major lignin peroxidase peaks (designated L1, L2 and L3) with lignin peroxidase activity in low nitrogen medium. Furthermore, in low nitrogen medium, mutant der8-5 produced up to fourfold greater lignin peroxidase activity than that produced by the wild type. In high nitrogen medium, the wild type produced no detectable lignin peroxidase peaks whereas the mutants produced peaks L1 and L2, but not L3, and a new lignin peroxidase protein peak designated LN. Mutants der8-2 and der8-5 also produced high levels of glucose oxidase, an enzyme known to be associated with secondary metabolism and an important source of H2O2 in ligninolytic cultures, both in low and high nitrogen media. In contrast, the wild type produced high levels of glucose oxidase in low nitrogen medium and only trace amounts of this enzyme in high nitrogen medium. The results of this study indicate that the der mutants are nitrogen-deregulated for the production of a set of secondary metabolic activities associated with lignin degradation such as lignin peroxidases, manganese peroxidases and glucose oxidase. 相似文献