Specific Inhibition of Lignification in Bryonia dioica: Effects on Thigmomorphogenesis

Rubbing-induced lignification in Bryonia dioica internodes is significantly impaired by N(o-hydroxyphenyl) and N(o-aminophenyl) sulfinamoyl tertiobutyl acetate, specific inhibitors of cinnamyl alcohol dehydrogenase, an enzyme which is strictly associated with lignin monomer synthesis. Along with the reduction of lignification, these inhibitors counteract the inhibition of elongation due to rubbing. These results indicate that lignification participates in the thigmomorphogenetic growth response of Bryonia dioica internodes. In a general way, the data point to the causal role of lignification in the limitation of plant growth.     

Characterization of cyclic nucleotide phosphodiesterase activity in Phaseolus vulgaris

Cyclic nucleotide phosphodiesterase (3',5'-cyclic nucleotide nucleotidohydrolase, EC 3.1.4.17) activity isolated from Phaseolus vulgaris L. cv. Limberg seedlings was partially purified and characterized by fractional (NH₄)₂SO₄ precipitation, DEAE-cellulose chromatography, chromatography on 3',5'-cAMP-agarose, gel permeation chromatography and chromatofocusing. A crude enzyme preparation, a 30–65% (NH₄)₂SO₄ pellet, showed an acidic pH optimum. The enzyme activity was stimulated by imidazole and divalent cations such as Ca²⁺, Mg²⁺ and Mn²⁺, whereas NaF, PP_i and Fe³⁺ were inhibitory. Isobutylmethylxanthine had no significant effect on the plant enzyme. An M_I of 42 000 was estimated by gel permeation high performance liquid chromatography. By chromatography on 3',5'-cAMP-agarose a phosphodiesterase was resolved that produced 5'-AMP as sole reaction product.     

Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid

The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA₃) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA₃ induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA₃ concentration. GA₃ having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA₃ appears to be on the transduction chain of the phytochrome signal.     

Elicitation of Necrosis in Vigna unguiculata Walp. by Homogeneous Aspergillus niger Endo-Polygalacturonase and by alpha-d-Galacturonate Oligomers

Endo-polygalacturonase (PG) was purified from a commercial preparation of Aspergillus niger pectinase by means of carboxymethylcellulose chromatography, preparative isoelectric focusing, and gel permeation through Sephadex G-50. The enzyme was electrophoretically homogeneous and consisted of a single polypeptide chain with a molecular weight of 33,500. The enzyme exhibited a specific activity significantly higher than those of purified polygalacturonases from phytopathogenic fungi. Galacturonate oligomers with a degree of polymerization higher than four appeared quickly as products of the enzymic hydrolysis of Napolygalacturonate. The oligomers were later degraded to di- and monogalacturonate. The homogeneous enzyme and growing mycelium of Aspergillus niger separately elicited a necrotic response in cowpea (Vigna unguiculata Walp.) pods. Heat-inactivated PG and PG inactivated with specific antibodies did not elicit necrosis, suggesting that the catalytic activity of the enzyme is necessary for its function as an elicitor. The PG-released oligosaccharides from Vigna cell wall and the galacturonides with a degree of polymerization greater than four separately elicited necrosis, whereas di- and monogalacturonate did not.     

Relative biological effectiveness (RBE) of neutrons produced by 50 MeV deuterons and by 34, 45, 65 and 75 MeV protons

RBE of p(34) + Be, p(45) + Be, p(65), + Be, p(75) + Be and d(50) + Be neutron beams produced at the cyclotron "Cyclone" of Louvain-la-Neuve were measured. The biological criterion was the regeneration of the crypts of the intestinal mucosa (50 regenerated crypts per circumference) after abdominal irradiation in mice. Taking the p(65) + Be neutrons as reference, RBE values were found equal to 1.12, 1.07, 1.00 (Ref.), 0.96 and 1.02 respectively. These results are consistent with those published for cell lethality in vitro. However, the RBE variation is smaller than this previously obtained in the laboratory for growth inhibition in Vicia faba.     

Chromosomal location of isozyme and seed storage protein genes in Dasypyrum villosum (L.) Candargy

Summary The zymogram phenotypes of glucose-phosphate isomerase (GPI), alcohol dehydrogenase-1 (ADH-1), glutamate oxaloacetate transaminase (GOT), superoxide dismutase (SOD), lipoxygenase (LPX), esterase (EST) and the banding patterns of gliadin and glutenin seed storage proteins were determined for Triticum aestivum cv. Chinese Spring (CS), Dasypyrum villosum, the octoploid amphiploid T. aestivum cv. Chinese Spring D. villosum (CS × v) (2n=8x=56; AABBDDVV), and for five CS-D. villosum disomic addition lines. The genes Gpi-V1, Adh-V1, Got-V2, and Sod-V2 coding for GPI-1, ADH-1, GOT-2, and SOD-2 isozymes were located in D. villosum on chromosome 1V, 4V, 6V, and 7V, respectively. Genes coding for gliadin- and glutenin-like subunits are located in D. villosum chromosomes 1V. There are no direct evidence for chromosomal location of genes coding for GOT-3, EST-1 and LPX-2 isozymes. The linkage between genes coding for glutenin-like proteins and GPI-1 isozymes in chromosome 1V is evidence of homoeology between chromosome 1V and the chromosomes of homoeologous group 1 in wheat.Research supported by the National Research Council (Italy) and National Science Foundation (USA). International cooperative project, Grant No. 85.01504.06 (CNR)     

Trichodorus persicus n. sp. (Nematoda: Trichodoridae) from Iran

Trichodorus persicus n. sp. is described from the Caspian region of Iran, where it was found in woodland and orchard soil. Males of the new species usually have two ventral cervical papillae anterior to the excretory pore but posterior to the base of the onchiostyle; there are three ventromedian preanal supplements, the posterior one lying near the heads of the retracted spicules; the spicules are 51–61 m long with faint transverse striations distally. Females have two pairs of lateral body pores, large rounded sclerotized thickenings at the vulva and the vagina tapers inwards in lateral view.     

The nuclear migration signal of Xenopus laevis nucleoplasmin.

Nucleoplasmin is the most abundant protein in the nucleus of Xenopus laevis oocytes. Its ability to target to the nucleus when microinjected into the cytoplasm has been the subject of many studies central to our understanding of how proteins segregate into nuclei. Using a cDNA clone we constructed beta-galactosidase-nucleoplasmin hybrids in modified bacterial expression vectors. The fusion proteins were expressed in Escherichia coli, purified and injected into the cytoplasm of X. laevis oocytes. The distribution of the fusion proteins between the cytoplasmic and nuclear compartments were analysed after incubation of various lengths of time. The results show that the signal sequence for nuclear transport is located close to the carboxy terminus of the protein. The signal sequence has been mapped to a small stretch of amino acids, containing a stretch of four lysines analogous to the SV40 large-T antigen signal.