Linkage relationship between the genes for adenosine deaminase and S-adenosyl-homocysteine hydrolase on human chromosome 20

Summary The genes for adenosine deaminase (ADA) and Sadenosyl homocysteine hydrolase (AHCY or SAHH) are known to be syntenic and within measurable distance from each other, on chromosome 20 in man. In the present study an informative family is described in which the recombination fraction (θ) between the respective genes is estimated to be about 0.18. Together with the published finding of θ=0.15 (Eiberg and Mohr 1985) in informative Danish families, the recombination fraction for the pooled data is calculated to be θ=0.14 (in men), (in women) and (both sexes taken together).     

An interstitial duplication of the X chromosome in a male allows physical fine mapping of probes from the Xq13-q22 region

Summary An insertional translocation into the proximal long arm of the X chromosome in a boy showing muscular hypotony, growth retardation, psychomotor retardation, cryptorchidism, and Pelizaeus-Merzbacher disease (PMD) was identified as a duplication of the Xq21–q22 segment by employing DNA probes. With densitometric scanning for quantitation of hybridization signals, 15 Xq probes were assigned to the duplicated region. Analysis of the duplication allowed us to dissect the X-Y homologous region physically at Xq21 and to refine the assignments of the loci for DXYS5, DXYS12, DXYS13, DXS94, DXS95, DXS96, DXS111, and DXS211. Furthermore, we demonstrated the presence of two different DXYS13, and DXS17 alleles in genomic DNA of our patient, suggesting that the duplication resulted from a meiotic recombination event involving the two maternal X chromosomes.     

Conformational analysis of a cyclic thymopoietin-analogue by 1H n.m.r. spectroscopy and restrained molecular dynamics simulations

The internuclear distances of the cyclic thymopoietin derivative c[D-Val-Tyr-Arg-Lys-Glu] have been determined using two-dimensional nuclear Overhauser n.m.r. spectroscopy. These distances are used as constraints for a restrained Molecular Dynamics (MD) simulation. The two starting structures used for the calculations consist of a beta and gamma turn for model 1 and two gamma turns for model 2. The rms difference in atomic positions of the two conformations is 0.242 nm. They converge during the restrained MD simulation to the same final structure. The positional rms difference of the time averaged (5-14 ps) conformations is 0.011 nm. The hydrogen bond pattern is similar to that of model 1, but in addition we find three more gamma turns. The vicinal NH-C alpha H couplings agree well with those calculated from the time averaged structures.     

Molecular cloning of thentrA gene of the broad host-rangeRhizobium sp. NGR234, and phenotypes of a site-directed mutant

Summary The clonedntrA (rpoN) gene andntrA mutants ofRhizobium meliloti were used to isolate the homologous gene from the broad-host rangeRhizobium sp. NGR234 by hybridization and interspecies complementation. The NGR234 locus was analyzed by deletion and insertional mutagenesis. A site-directedntrA mutant, NGR234rn1, was made with an interposon, GmI, and its phenotype was examined ex planta and in symbiosis. NGR234rn1 formed Fix⁻ nodules on six genera tested from among its legume hosts, including both indeterminate and determinate nodule-type plants. Formation of nodules onMacroptilium was delayed, and expression of anR. meliloti nodABC-lacZ fusion was reduced by the mutant allele.     

The effect of seaweed concentrate on the growth and yield of potassium stressed wheat

The effects of the seaweed concentrate “Kelpak’ on the growth and yield of wheat grown under conditions of varying K supply were investigated. Kelpak had no significant effect on the yield of wheat receiving an adequate K supply, but significantly increased the yield of K stressed plants. The increase in yield was caused by an increase in both grain number and individual grain weight. Although the beneficial effects of seaweed concentrates have often been attributed to their cytokinin content, several lines of evidence suggested that this group of plant growth regulators may not be solely responsible for the observed effects of Kelpak on wheat. Irrespective of the physiological mechanism of action, Kelpak would appear to have considerable potential for increasing yield in K stressed wheat and may therefore reduce the requirement of wheat for K fertilization.     

Effects of rhizosphere soil,vesicular-arbuscular mycorrhizal fungi and phosphate onPlantago major L. ssp.pleiosperma Pilger

Biotic factors in the rhizosphere and their effect on the growth ofPlantago major L. ssp.pleiosperma Pilger (Great plantain) were studied. In a pot experiment the effect on shoot growth of the addition of 2.5% rhizosphere soil at four levels of phosphate was highly dependent on the availability of phosphate: a promoting effect at low phosphate levels was observed while a reducing effect occurred at higher phosphate levels. As the roots were infected with vesicular-arbuscular mycorrhizal (VAM) fungi in the treatment with rhizosphere soil, two other experiments were set up to separate effects of the indigenous VAM fungi from effects of the total rhizosphere population. The uptake of phosphate and shoot growth was not decreased at higher phosphate availability when VAM inoculum was added alone or in combination with rhizosphere soil. The growth reducing effect of the rhizosphere soil could therefore not be ascribed only to mycorrhizal infection. The results suggest that biotic factors in the rhizosphere soil affect the phosphate uptake ofPlantago major ssp.pleiosperma. This may, under conditions of phosphate limitation, lead to an increase of phosphate stress and, subsequently, a growth reduction. Futhermore, it is concluded that VAM fungi, as part of the rhizosphere population, may compensate this phosphate stress by enhancing the phosphate uptake.Grassland Species Research Group Publication No. 148.     

Characterization of a meta-Fluorotyrosine-Tolerant Cell Culture of Eschscholtzia californica Cham

A cell line of Eschscholtzia californica selected for meta-fluorotyrosine (MFT) tolerance was found to have 10-fold increased levels of phenylalanine and tyrosine compared to the parent line, while most other amino acids were only increased 2-fold. Tracer experiments with shikimic acid in the presence of MFT showed that the biosynthesis of the aromatic amino acids was not impaired in the tolerant line. Feeding experiments with phenylalanine, tyrosine, or shikimic acid also revealed a reduced turnover of the pools of the aromatic amino acids in the variant. Thus undisturbed de novo biosynthesis of the aromatic amino acids and dilution of toxic effects of MFT by the enlarged pool sizes seemed to be the main reason for the acquired tolerance. Despite the enlarged availability of the precursor tyrosine, formation of the benzophenanthridine alkaloids was enhanced neither in the growth nor in the production medium.