Transgenic carnations obtained byAgrobacterium tumefciens-mediated transformation of leaf explants

For the development of anAgrobacterium-mediated transformation procedure of carnation (Dianthus caryophyllus L.), an intron-containing -glucuronidase (gus) gene was used to monitor the frequency of transformation events soon after infection of leaf explants. The efficiency of gene transfer was dependent on the carnation genotype, explant age and cocultivation time. Leaf explants from the youngest leaves showed the highest number of GUS-positive spots. After selection on a kanamycin-containing medium, transgenic shoots were generated among a relatively high number of untransformed shoots. The selection procedure was modified in such a way that the contact between explant and medium was more intense. This improved the selection and decreased the number of escapes. Kanamycin-resistant and GUS-positive plants were obtained from five cultivars after infection of leaf explants with the supervirulentAgrobacterium strain AGLO. A higher transformation frequency was observed with the binary vector pCGN7001 than with the p35SGUSint vector. Integration of the genes into the carnation genome was demonstrated by Southern blot hybridization. The number of incorporated T-DNA insertions varied between independent transformants from one to eight. Transformants were morphologically identical to untransformed plants. Segregation of the genes occurred in a Mendelian way.     

The biosynthetic pathway of new polyamines in Caldariella acidophila

A spontaneous mutant of Escherichia coli (strain AB2847), selected for resistance to the aminoglycoside antibiotic neamine, shows severe restriction of amber suppressors in vivo. Ribosomes isolated from the mutant exhibit only low misreading in vitro in the presence of the antibiotic. Genetic and biochemical analyses indicate that the neamine-resistant phenotype is the result of two distinct mutations. The first, res3128, appears to affect the gene (strA) coding for the ribosomal protein S12. Although it leads to a restrictive phenotype it does not, however, confer resistance to streptomycin. The second mutation, X3128, is located between the sirA and AROB loci and is lethal when segregated from the res3128 mutation. It may affect the ribosome at the level of a post-translational modification.     

On the nature of chromophore in pig kidney diamine oxidase.

The nature of the 500-nm chromophore in pig kidney diamine oxidase was investigated by absorption spectroscopy and fluorescence in the presence of various chelating or carbonyl-specific reagents. From the spectroscopic measurements the following conclusions can be drawn. First, the 500-nm absorption band is not due to copper, the reduction of which is not related to the disappearance of this band. Second, phenylhydrazine and cycloserine give rise, upon reaction with the enzyme, to absorptions very similar to those of a pyridoxal enzyme, aspartate aminotransferase. Third, these enzyme derivatives are unexpectedly non-fluorescent. Copper removal, obtained after prolonged incubation of cycloserine-treated enzyme in the presence of reducing and chelating agents, leads to a fluorescence similar to that of cycloserine-aspartate transminase. It is proposed that copper is coordinated to the postulated pyridoxal phosphate of diamine oxidase through the pyridine nitrogen.     

Molecular cloning of pea mRNAs encoding a shoot-specific polypeptide and light-induced polypeptides

Summary The molecular cloning of cDNA corresponds to pea seedling mRNA sequences encoding a shoot-specific polypeptide, the small subunit of the ribulose 1,5 biphosphate carboxylase and a component of the light-harvesting chlorophyll a/b complex is described. cDNA prepared from polysomal poly(A)RNA of light-grown shoots was enriched for shoot-specific and light-induced sequences by heterologous liquid hybridization with mercurated polysomal poly(A)RNA of dark-grown roots, followed by sulfhydryl chromatography. Cloned shoot-specific sequences were identified by 2D electrophoretic analysis of hybrid release translation products. The cloned shoot-specific sequence corresponded to a mRNA of 850 nt present both in light-and dark-grown shoots, and produced anin vitro translation product of M_r27 500 and isoelectric point of 4.7.     

The effect of feeding on plasma immunoreactive ACTH and beta-endorphin levels in newborn infant.

In order to clarify whether an interaction between endogenous opioids and feeding occurs at birth, we studied Beta-endorphin (beta-EP) and ACTH plasma levels in response to a feed of 10% glucose, or formula, in 120 healthy full-term infants. Neither postprandial beta-EP nor ACTH increases were found at the 24th hour or on the fourth day of life. beta-EP physiology in newborn infants seems to be different from adults.     

On coenzyme Q orientation in membranes: A linear dichroism study of ubiquinones in a model bilayer

Summary A general approach is developed to interpret linear dichroism (LD) spectra of ubiquinones (Q _n) in host bilayers. Information is reported in terms of guest-host mutual orientation and localization. The overall orientational anisotropy of guest ubiquinone molecules is described by a basic set of limiting orientation/localization modes. Assignments of the UV transitions of the ubiquinone chromophore were obtained by the liquid crystal-linear dichroism technique and molecular orbital (CNDO/S) calculations. The LD spectra of Q _n in the bilayers provided by the lyotropic nematic mesophase exhibited by water solutions of potassium laurate and decanol were interpreted on the basis of the above assignments. The resulting experimental evidence showed a multisite distribution in the host bilayer for the aromatic heads of all the investigated Q _n derivatives except Q₀. The orientational distribution suggested by the LD spectra fits the solubilization model recently proposed by G. Lenaz [J. Membrane Biol. (1988) 104:193–209] for ubiquinone in lipid membranes. Within this model Q _n molecules are located in the midplane and their headgroups oscillate transversally across the membrane. Q ₀ instead has a single site location, close to the polar bilayer interface. Experimental evidence that the headgroup carbonyls tend to grasp the polar interface of the host bilayer was also obtained. Orientation and location distributions of Q _n guest molecules are therefore likely to result from the tendency of their aromatic heads to grasp the polar heads of the host bilayer and from the concurrent tendency of their chains to settle into the hydrocarbon host interior.abbreviations AA average absorption - OD, OD optical densities for plane polarized radiations parallel () and perpendicular () to the sample optical axis - OD OD — OD - EPR electron paramagnetic resonance - LC-LD liquid crystal-linear dichroism - LD linear dichroism - LD _r reduced linear dichroism. - MO molecular orbital - N nematic - NMR nuclear magnetic resonance - S _jj order parameters of the directions j of the transition moments of the guest chromophore - S _ii order parameters of the orientational axes i of the guest molecule with respect to the magnetic field - S _ii order parameters of the axes i of the guest molecules with respect to the bilayer axis a - S _a order parameters of the host bilayer axis a with respect to the orienting magnetic field - _j,i deflection angles between the directions j and the axes i - O _i optical factors of the i axis see Eq. (A4)] - Q_n ubiquinone whose isoprenoid chain contains n isoprenoid units Dr. A. Rossi is gratefully acknowledged for the t.e.m. reduction of the spectra. Ubiquinone homologs were kind gifts from Eisai Co., Tokyo, Japan. This work was supported by M.U.R.S.T., and C.N.R. Target Project on Biotechnology and Bioinstrumentation, Rome, Italy.     

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.     

Effect of abscisic acid on CO2 exchange in Lemna gibba

The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10⁻⁷M and in a few experiments, 10⁻⁶M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO₂ uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [¹⁴C]-ABA uptake by Lemna . Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA.     

Lipid peroxidation induced by cercosporin as a possible determinant of its toxicity

The photodynamic action of cercosporin was assayed in various kinds of natural and artificial membranes. Cerosporin induces lipoperoxidation of liposomes, rat liver and pea internode mitochondria and microsomes, estimated both as malondialdehyde (MDA) formation and O2 consumption. Cercosporin-induced lipoperoxidation is inhibited by either singlet oxygen quenchers, free radical trapping agents or EDTA. Superoxide anion (O2-), hydrogen peroxide and hydroxyl radicals (.OH) are not involved in the activity of cercosporin. In addition cercosporin, by chelating iron, lowers the lipoperoxidation induced by such a metal. Therefore cercosporin stimulates, through singlet oxygen production, the hydroperoxide formation but, at the same time, it inhibits the continuation of the iron-mediated free radical chain. The present results suggest that cellular lipid peroxidation has a certain relevance to toxic activity of cercosporin.