Karyotype variation in aminoethylcysteine resistant cell and callus cultures and regenerated plants of a dihaploid potato (Solanum tuberosum)

Karyotypic studies on cell suspensions and calli of an S-(2-aminoethyl)cysteine resistant cell line of the interdihaploid potato H²578 (2n=24) revealed a high degree of variation in the number of chromosomes (33–217) and dicentric chromosomes (0–8). The suspensions also exhibited megachromosomes and fused chromosomes. Differential staining showed that in suspensions dicentrics survived mitotic cycles mainly by parallel separation of the chromatids during anaphase and hardly by the breakage-fusion-bridge cycle. Two phenotypes of plantlets regenerated, each with 34 or 35 chromosomes with gross structural mutations and with the triploid amount of DNA. Chromosomal variation was related to the degree of tissue organization.     

Modification of root bud growth in Canada thistle with selected plant growth regulators: effects on translocation of glyphosate

Root applications of 0.1 M 6-benzyladenine (BA) and 10.0 M indole-3-butyric acid (IBA) enhanced or inhibited, respectively, root bud growth in hydroponically grown Canada thistle [Cirsium arvense (L.) Scop.]. Translocation of¹⁴C-glyphosate [N-(phosphonomethyl)glycine] into roots was positively correlated with this growth. Foliar applications of ethephon or chlorfluorenol also enhanced root bud growth, but glyphosate translocation was only weakly correlated with such growth in soil-grown Canada thistle. At glyphosate rates above 0.56 kg/ha, root bud growth was not stimulated by plant growth regulators (PGRs) and basipetal translocation was not enhanced. Paradoxically, ethephon and chlorflurenol restrained root bud growth in the field since thistle control steadily improved during the 3 years following treatment.     

Relation Entre la Teneur en Sucres Réducteurs des Tissus du Tournesol (Helianthus annuus L.) et leur Invasion par Macrophomina phaseolina (Tassi) Goid.

Relation between the amount of reducing sugars in sunflower tissues and their invasion by Macrophomina phaseolina (Tassi) Goid. Reducing sugars (R.S.) were measured with Bernfeld colorimetric method. In the roots, the amount of R.S. increased up to a maximum, then decreased from the beginning of flowering, and remained constant, at a very low level, from the outset of seed maturation. The same evolution was observed, with a delay of one week, in stem bases, but the amounts of R.S. were a little higher. Roots, and thereafter, stems, were invaded by Macrophomina phaseolina only after the minimum level of R.S.was reached. Varietal differences were observed, in a collection of sunflower hybrids, in response to invasion by M. phaseolina. R.S. levels in stem bases were higher in the resistant than in the susceptible hybrids.     

The effect of irrigation on powdery scab and other tuber diseases of potatoes

In field experiments seed tubers affected with powdery scab cankers were planted and the effect on disease incidence of timing of irrigation and some seed-tuber fungicides was investigated over 3 yr. For 2 yr, irrigation to maintain soil wetter than—20 centibars (—20 kPa) during the first half of the growing season increased disease compared to unirrigated plots. Disease incidence was not affected by irrigation at 2 wk intervals or when applied during the second half of the season. Little disease developed in 1983 even in irrigated plots, probably because of high soil temperatures. None of the fungicides tested gave consistent disease control. Common scab and silver scurf were both decreased by irrigation but in two years, black dot was increased. The relative importance of black dot could increase in irrigated crops where fungicides are used to control silver scurf.     

Covalent binding of 4-carbamoylbenzenediazonium chloride to deoxyguanine bases of DNA resulting in apparent irreversible inhibition of poly(adenosine diphosphoribose) polymerase at the nicotinamide binding site

The poly(adenosine diphosphoribose) polymerase activity of isolated liver nuclei was inhibited by 4-carbamoylbenzenediazonium chloride, referred to as 4-diazoniobenzamide, an effect that was dependent on the time of incubation and the concentration of the diazonium compound, with inhibition following first-order kinetics. The inhibition was not reversed by reisolation of nuclei and centrifugal washing, whereas the inhibition by benzamide or 4-aminobenzamide was completely reversible under these conditions. Simultaneous incubation of 4-diazoniobenzamide with benzamide prevented enzyme inhibition. The 4-diazoniobenzoic acid analogue was not inhibitory. The mechanism of action of 4-diazoniobenzamide was traced to a specific covalent binding to dGMP of DNA to form N2-[(4-carbamoylphenyl)azo]-2'-deoxyguanosine 5'-monophosphate. Coenzymic DNA, by tight association with the polymerase protein, fixes the -C(O)NH2 moiety of the adduct at the nicotinamide-binding site of the enzyme.     

Virtual and solution conformations of oligosaccharides

The possibility that observed nuclear Overhauser enhancements and bulk longitudinal relaxation times, parameters measured by 1H NMR and often employed in determining the preferred solution conformation of biologically important molecules, are the result of averaging over many conformational states is quantitatively evaluated. Of particular interest was to ascertain whether certain 1H NMR determined conformations are "virtual" in nature; i.e., the fraction of the population of molecules actually found at any time within the subset of conformational space defined as the "solution conformation" is vanishingly small. A statistical mechanics approach was utilized to calculate an ensemble average relaxation matrix from which (NOE)'s and (T1)'s are calculated. Model glycosidic linkages in four oligosaccharides were studied. The solution conformation at any glycosidic linkage is properly represented by a normalized, Boltzmann distribution of conformers generated from an appropriate potential energy surface. The nature of the resultant population distributions is such that 50% of the molecular population is found within 1% of available microstates, while 99% of the molecular population occupies about 10% of the ensemble microstates, a number roughly equal to that sterically allowed. From this analysis we conclude that in many cases quantitative interpretation of NMR relaxation data, which attempts to define a single set of allowable torsion angle values consistent with the observed data, will lead to solution conformations that are either virtual or reflect torsion angle values possessed by a minority of the molecular population. On the other hand, calculation of ensemble average NMR relaxation data yields values in agreement with experimental results. Observed values of NMR relaxation data are the result of the complex interdependence of the population distribution and NOE (or T1) surfaces in conformational space. In conformational analyses, NMR data can therefore be used to test different population distributions calculated from empirical potential energy functions.     

Secondary structure of 5S RNA: NMR experiments on RNA molecules partially labeled with nitrogen-15

A method has been found for reassembling fragment 1 of Escherichia coli 5S RNA from mixtures containing strand III (bases 69-87) and the complex consisting of strand II (bases 89-120) and strand IV (bases 1-11). The reassembled molecule is identical with unreconstituted fragment 1. With this technique, fragment 1 molecules have been constructed 15N-labeled either in strand III or in the strand II-strand IV complex. Spectroscopic data obtained with these partially labeled molecules show that the terminal helix of 5S RNA includes the GU and GC base pairs at positions 9 and 10 which the standard model for 5S secondary structure predicts [see Delihas, N., Anderson, J., & Singhal, R. P. (1984) Prog. Nucleic Acid Res. Mol. Biol. 31, 161-190] but that these base pairs are unstable both in the fragment and in native 5S RNA. The data also assign three resonances to the helix V region of the molecule (bases 70-77 and 99-106). None of these resonances has a "normal" chemical shift even though two of them correspond to AU or GU base pairs in the standard model. The implications of these findings for our understanding of the structure of 5S RNA and its complex with ribosomal protein L25 are discussed.     

Laser-Raman and infrared spectroscopic studies of protein conformation in the eggshell of the fish Salmo gairdneri

Laser-Raman and infrared spectroscopic studies reveal abundant beta-pleated sheet conformation in the eggshell proteins of the fish Salmo gairdneri. This secondary structure is the underlying molecular conformation, dictating the formation of the helicoidal architecture of the eggshell. Disulphide bonds crosslink the eggshell proteins of the fertilized eggs and are apparently found in g-g-g (gauche-gauche-gauche), g-g-t (gauche-gauche-trans) and t-g-t (trans-gauche-trans) conformation. There is no evidence for the existence of free sulphydryls. The tyrosines appear to act as hydrogen-bond acceptors, whereas the aromatic residues phenylalanine and tryptophan are also eggshell protein constituents.     

Structural and physico-chemical properties of amino acids of functionally important regions of proteins

A correlation of the localization of functionally important regions with places having low and high values on twelve profiles built on a basis of amino acid sequences was analysed using a broad set of proteins. The profiles of hydrophilicity, resemblance to the sequences of human proteins, flexibility, mutability and others were considered. The resemblance profile was plotted by the program fixing short similar fragments in the testing protein and 92 human ones. The active centres were shown to be located in the primary structure regions having relatively low values on the resemblance profiles. Similar effect was observed in the mutability and alpha-helicity profiles. The potential functionally important sites of the human leukocyte interferon and interleukin-2 isolated on the basis of the analysis of this profiles were in accord with the available literary data.