Polyploidy and aspartate-transcarbamylase activity in Hippocrepis comosa L.

The DNA content of plants which were sampled in natural di-, tetra- and hexaploid populations of Hippocrepis comosa L. was estimated and the aspartate transcarbamylase activities of the corresponding cell-free extracts were compared. The amount of DNA is not exactly proportional to the number of genomes. The three kinds of populations do not differ in their aspartate transcarbamylase specific activity. While the enzyme properties are identical in the extracts derived from the diploid and hexaploid plants, the aspartate transcarbamylase present in the tetraploid cytotype shows a slightly lower affinity for one of its substrates and a significantly lower sensitivity to the feedback inhibitor UTP which is still observed after partial purification. These properties might be related to the previously reported greater ability of the tetraploid cytotype to adapt to a variety of biotopes.Abbreviations ATCase aspartate transcarbamylase - CAP carbamylphosphate - EDTA ethylenediaminetetracetic acid - Tris trihydroxymethylaminomethane - AMP adenosine monophosphate - ATP adenosine triphosphate - CMP cytidine monophosphate - CTP cytidine triphosphate - UMP uridine monophosphate - UTP uridine triphosphate     

Spot position of rat liver ribosomal proteins by four different two-dimensional electrophoreses in polyacrylamide gel

Summary Separation of the proteins from rat liver 40S and 60S ribosomal subunits and polysomes was done in four different two-dimensional polyacrylamide gel electrophoresis systems. The first dimension was run at acidic or basic pH, the second dimension either with sodium dodecyl sulphate or at acidic pH in 18% acrylamide. The position of each individual protein of both subunits and polysomes was determined in each system. This identification resulted from a new method avoiding any previous purification of individual proteins. The new proposed uniform nomenclature for mammalian ribosomal proteins (McConkey et al. in press) was used for numbering the proteins in the four systems.     

Biochemical evidence for the non-inactivation of the steroid sulfatase locus in human placenta and fibroblasts

Summary Steroid sulfatase activities are significantly higher in placentas obtained after the birth of girls than after the birth of boys, and also in female fibroblasts compared to male strains. This constitutes biochemical evidence for the non-inactivation of the X-linked sulfatase locus. No hydrolytic activity is found in the fibroblasts of ichthyotic boys. Heterozygosity is demonstrated in the fibroblasts of the four mothers studied, as they have steroid sulfatase activity of less or equivalent to the normal male value.     

Binding of 4-methylumbelliferyl-galactosides to peanut agglutinin

The binding of 4-methylumbelliferyl-α-D-galactopyranoside, -β-D-galactopyranoside and -D-Galβ(1→3)DGalNac to peanut agglutinin was studied by fluorescence. Peanut agglutinin quenched the fluorescence intensity of 4-methylumbelliferyl-α-D-galactopyranoside but enhanced that of the two 4-methylumbelliferyl-β-galactosides. For α-D-galactopyranoside, the association constants measured at 4 and 25°C were 3.4 × 10³ and 1.7 × 10³ M^?1 respectively, and for D-Galβ(1→3)DGalNac, 1.5 × 10⁵ and 3.3 × 10⁴ M^?1. The binding enthalpies estimated from these values are consistent with the existence of extended sugar binding sites in the peanut agglutinin molecule.     

Divergent evolution of chloroplast-type ferredoxins

The TOL plasmid pWW0 of Pseudomonas putida encodes a set of enzymes required for the oxidation of toluene to Krebs cycle intermediates. The structural genes for these enzymes are encoded in two operons which comprise the xylCMABN and xylXYZLTEGFJQKIH genes, respectively. The function of the xylT gene has not yet been identified. The nucleotide sequence of xylT was determined in this study and putative gene product was shown to contain a sequence characteristic for chloroplast-type ferredoxins. The nahT gene, the homologue of xylT, present on NAH plasmid NAH7 encoding naphthalene-degrading enzymes, was also sequenced. The sequence conservation between xylT and nahT strongly suggests that both gene products have some physiological function. Chloroplast-type ferredoxins have been discovered in photosynthetic organisms (plants, algae, cyanobacteria and Rhodobacter) and Halobacterium species. Furthermore, chloroplast-type ferredoxin-like sequences have been found in the electron-transfer components of some oxygenases. The sequences of XylT and NahT were compared with those of the previously identified chloroplast-type ferredoxins, in order to examine their evolutionary relationships.     

Mitochondrial DNA evolution in lagomorphs: Origin of systematic heteroplasmy and organization of diversity in European rabbits

Summary A characterization was conducted on mitochondrial DNA (mtDNA) molecules extracted separately from 107 European rabbits (Oryctolagus cuniculus) both wild and domestic, 13 European hares (Lepus capensis), and 1 eastern cottontail (Sylvilagus floridanus). Experimentally this study took into account restriction site polymorphism, overall length variation of the noncoding region, and numbers of repeated sequences. Nucleotide divergences indicate that the mtDNAs from the three species derived from a common ancestor some 6–8 million years (Myr) ago. Every animal appeared heteroplasmic for a set of molecules with various lengths of the noncoding region and variable numbers of repeated sequences that contribute to them. This systematic heteroplasmy, most probably generated by a rate of localized mtDNA rearrangements high enough to counterbalance the cellular segregation of rearranged molecules, is a shared derived character of leporids.The geographic distribution of mtDNA polymorphism among wild rabbit populations over the western European basin shows that two molecular lineages are represented, one in southern Spain, the second over northern Spain, France, and Tunisia. These two lineages derived from a common ancestor some 2 Myr ago. Their present geographical distribution may be correlated to the separation of rabbits into two stocks at the time of Mindel glaciation.Finally the distribution of mtDNA diversity exhibits a mosaic pattern both at inter- and intrapopulation levels.     

Sequences homologous to Tc(s) transposable elements ofCaenorhabditis elegans are widely distributed in the phylum nematoda

Summary To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements fromCaenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found inCaenorhabditis and inTeratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and inBursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited toC. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history.     

Agrobacterium rhizogenes mediated induction of apparently untransformed roots and callus in chrysanthemum

The agropine type Agrobacterium rhizogenes strain LBA9402 induced callus and roots on stems of greenhouse grown plants and on leaf disks of in vitro grown plantlets of chrysanthemum (Dendranthema grandiflora Tzvel.). In this callus and roots no opines were detected, nor were any of the other features of the hairy root syndrome observed. Experiments aimed to identify the nature of the tumour-like growth revealed that induction was correlated with the presence of the TR-DNA on the Ri-plasmid. Root induction was probably the result of auxin synthesis following transient expression of iaaM and iaaH genes, present on the TR-DNA. The chrysanthemum cultivar used, cv. Parliament, showed a high auxin sensitivity compared to tobacco. Analysis of early transformation events using the GUSintron reporter gene revealed that low efficiency gene transfer and transient gene expression took place, but most probably without stable integration of the T-DNA in the plant genome. The results presented here stress the fact that callus formation or root induction as measures for transformation efficiency should be used with caution.     

Altered sensitivity to colchicine and PHA in human cultured cells

Summary PHA-stimulated lymphocytes cultivated from a pair of human monozygotic twins yielded mostly tetraploid cells when colchicine was not used to arrest the metaphases. The rate of tetraploidy was also enhanced by colchicine in fibroblasts cultured without PHA. In in situ condition, larger than usual cells were observed. Other defects found in parental lymphocyte cultures included C-anaphase cells and increased cell aggregation. These results suggest a membrane mutation resulting in hypersensitivity to PHA and variant response to colchicine.