ELISA Quantitation and GC-MS identification of abscisic acid in stigma, ovary and pedicel of pollinated poplar flowers (Populus nigra L.)

A method of fractionation, quantitation and identification of abscisic acid (ABA) in poplar flowers is presented in the context of intra- and interspecific pollination studies in Populus nigra x P. nigra and P. nigra x P. deltoides, respectively. Poplar flowers were dissected into stigma, ovary and pedicel. Abscisic acid concentrations were measured at receptivity and 5 days after pollination in each part of the flower. Abscisic acid was fractionated by reverse-phase HPLC followed by an enzyme-linked immunosorbent assay (ELISA) with anti-ABA polyclonal antibody and GC-MS identification of the immunoreactive ABA fractions. Samples were fractionated and ABA was identified by the presence of a cross-reactive metabolite of ABA in the extracts. The interspecific cross (P. nigra x P. deltoides) had a high concentration of ABA in the pedicel, where abscission occurred, whereas in the intraspecific cross, ABA concentration in the pedicel was low. The results are discussed with reference to the control ABA exerts on the abscission of poplar flowers after interspecific incompatible pollinations.     

Genetic variation in productivity, leaf traits and carbon isotope discrimination in hybrid poplars cultivated on contrasting sites

? We examined the relationships between productivity, leaf traits and carbon isotope discrimination in bulk leaf matter (Δ₁) and in phloem sap (Δ_s) from more than 5-year-old trees belonging to Populus deltoides × P. nigra and Populus trichocarpa × P. deltoides; trees were grown in alluvial and non alluvial sites in a commercial poplar plantation.

? On both sites, a large genetic variability was evidenced for all variables. The genotypic ranking remained stable between years for all variables, while it differed between sites. Δ₁ scaled positively with Δ_s and neither Δ₁ nor Δ_s were correlated with productivity. A significant genotype by site interaction was evident for all variables. The non alluvial site resulted in lower productivity, and in thicker/denser leaves with lower nitrogen and carbon contents. Noteworthy, the genotypic ranking for Δ₁ measured at the alluvial site was similar to that previously established in a glasshouse.

? As observed in previous studies from younger trees, there is a potential to select genotypes, combining high productivity and high water-use efficiency, for growth in moderately drought-prone areas.

     

Importance of the life cycle in sympatric host race formation and speciation of pathogens

ABSTRACT Numerous morphological species of pathogenic fungi have been shown to actually encompass several genetically isolated lineages, often specialized on different hosts and, thus, constituting host races or sibling species. In this article, we explore theoretically the importance of some aspects of the life cycle on the conditions of sympatric divergence of host races, particularly in fungal plant pathogens. Because the life cycles classically modeled by theoreticians of sympatric speciation correspond to those of free-living animals, sympatric divergence of host races requires the evolution of active assortative mating or of active host preference if mating takes place on the hosts. With some particular life cycles with restricted dispersal between selection on the host and mating, we show that divergence can occur in sympatry and lead to host race formation, or even speciation, by a mere process of specialization, with strong divergent adaptive selection. Neither active assortative mating nor active habitat choice is required in these cases, and this may explain why the phylo-genetic species concept seems more appropriate than the biological species concept in these organisms.     

Lowest effective and optimum poultry manure dose for reclaiming burnt soils: pot experiments

 Poultry manure (PM) efficacy to improve burnt soil revegetation was evaluated to determine the lowest effective and the optimum dose for burnt soil reclamation. A ¹⁵N-labelled forest soil (LS) was used to set up six treatments: LS, laboratory burnt LS (BLS) and BLS with PM dose equivalent to 1 (BLS+PM1), 2 (BLS+PM2), 4 (BLS+PM4) and 8 Mg dry PM ha^–1 (BLS+PM8). Ryegrass was sown in all treatments and grown for 3 months in a greenhouse. At harvesting, in the BLS treatment: (1) ryegrass yield was very low and the shoot:root ratio was high; (2) ryegrass-N content was closer to that of metabolic tissues or young plants than to structural tissues or mature plants; (3) most of the available endogenous N still remained in the soil inorganic N pool. These results suggested that, although seed germinated normally, ryegrass growth was stopped at an early developmental stage, producing small and weak plants unable to protect the burnt soil against erosion and to exploit the post-fire pulse of available N which, consequently, could be lost. The addition of PM to BLS increased the ryegrass yield from the lowest dose (BLS≈LS<BLS+PM1< BLS+PM2<BLS+PM4<BLS+PM8;P<0.05), the increase of the phytomass yield per Mg of added PM varying as follows: PM8<PM1≤PM4<PM2. The uptake of soil-available N by the ryegrass was greatly enhanced in all manured treatments, but the contribution of PM-N to plant nutrition was only significant in BLS+PM4 and BLS+PM8 treatments. The lowest effective PM dose was PM1 and the optimum cost-to-benefit ratio treatments were PM2 and PM4. Received: 31 January 2000     

The Sierra Norte of Madrid: an agrobiodiversity refuge for common bean landraces

At the mountain area close to the city of Madrid, common beans were one of the main food crops present in everyday diet until 1960. This paper describes the morphological diversity, for forty-six phenological and morphological traits, found in forty-three traditional varieties of common beans collected in this area and seven commercial varieties used as reference. That comparison suggests that common bean breeding programs have led to later varieties with a higher production of straight pods. Quantitative traits showed also similar values when compared to the Iberian common bean collection, except for the phenological and seed size characters. The phenological differences could suggest an ecological adaptation of the studied landraces to the regional environmental conditions. The different seed size averages of both collections might correspond to the scarce presence of smaller seed-type common beans in Madrid collection. All the accessions collected in the Sierra Norte of Madrid belong to any of the groups included in the Spanish core collection. Madrilenian collection is also composed by indeterminate growth habit varieties, while the presence of bush accessions is relatively uncommon. Most of the Madrilenian landraces have a remarkable fitness for green-pod consumption (42 %) and their seeds are mainly white (30 %), ovate-shape (49 %) and medium-large (40 %). The study of seed storage protein allowed to classify the landraces according to their domesticated gene pools. Most of them (72 %), with T and C phaseolin type, seem to belong to Andean germplasm, while the remaining (28 %), with S and B phaseolin type, to Mesoamerican one. The remarkable morphological diversity of common beans found in this small area is a symptom of a broad genetic base despite genetic erosion, what indicates a widespread crop in the past. Therefore, it is advisable to design agro-environmental policies to promote the production and commercialization of common bean landraces in Sierra Norte of Madrid.     

Lignin changes after steam explosion and laccase-mediator treatment of eucalyptus wood chips

Eucalyptus globulus chips were steam exploded followed by treatment with a laccase-mediator system (LMS) under different experimental conditions. Removal of hemicelluloses and, to a lesser extent, lignin was observed. Thermogravimetic analyses of whole meal obtained from chips before and after steam explosion indicated an increase in lignin degradation temperature due to lignin condensation. In contrast, application of LMS treatment caused a reduction in lignin and polysaccharide degradation temperatures. Lignins were isolated from wood samples before and after each treatment and analyzed by 2D NMR and (13)C NMR. An increase in carboxyl and phenolic hydroxyl groups and a significant decrease in β-O-4 structures were found in steam-exploded samples. The most relevant changes observed after laccase treatment were increased secondary OH and degree of condensation.     

A synthetic conjugate polysaccharide vaccine against Haemophilus influenzae type b

Glycoconjugate vaccines provide effective prophylaxis against bacterial infections. To date, however, no commercial vaccine has been available in which the key carbohydrate antigens are produced synthetically. We describe the large-scale synthesis, pharmaceutical development, and clinical evaluation of a conjugate vaccine composed of a synthetic capsular polysaccharide antigen of Haemophilus influenzae type b (Hib). The vaccine was evaluated in clinical trials in Cuba and showed long-term protective antibody titers that compared favorably to licensed products prepared with the Hib polysaccharide extracted from bacteria. This demonstrates that access to synthetic complex carbohydrate-based vaccines is feasible and provides a basis for further development of similar approaches for other human pathogens.     

Variations in bulk leaf carbon isotope discrimination, growth and related leaf traits among three Populus nigra L. populations

The ongoing global change could be an additional threat to the establishment and the long-term survival of Populus nigra L., an emblematic European riparian species. With the general aim of gaining insights into the adaptive potential of this species, we (i) quantified variations within and among three French P. nigra populations for key physiological attributes, i.e., water-use efficiency (assessed from bulk leaf carbon isotope discrimination, Δ(13)C), growth performance and related leaf traits, (ii) examined genotype and population by environment interactions, and (iii) explored the relationship between Δ(13)C and growth. Thirty genotypes were sampled in each of three naturally established populations and grown in two different sites, Orléans (ORL) and Guémené-Penfao (GMN). In ORL, two similar plots were established and different watering regimes were applied in order to test for the drought response. Significant variations were observed for all traits within and among populations irrespective of site and watering. Trait variation was larger within than among populations. The effect of drought was neither genotype- nor population-dependent, contrary to the effect of site. The population ranking was maintained in all sites and watering regimes for the two most complex traits: Δ(13)C and growth. Moreover, these two traits were unrelated, which indicates that (i) water-use efficiency and growth are largely uncoupled in this species, and (ii) the environmental factors driving genetic structuration for Δ(13)C and growth act independently. The large variations found within populations combined with the consistent differences among populations suggest a large adaptive potential for P. nigra.     

Synthesis and Biological Evaluation of Novel 3-Alkylpyridine Marine Alkaloid Analogs with Promising Anticancer Activity

Cancer continues to be one of the most important health problems worldwide, and the identification of novel drugs and treatments to address this disease is urgent. During recent years, marine organisms have proven to be a promising source of new compounds with action against tumoral cell lines. Here, we describe the synthesis and anticancer activity of eight new 3-alkylpyridine alkaloid (3-APA) analogs in four steps and with good yields. The key step for the synthesis of these compounds is a Williamson etherification under phase-transfer conditions. We investigated the influence of the length of the alkyl chain attached to position 3 of the pyridine ring on the cytotoxicity of these compounds. Biological assays demonstrated that compounds with an alkyl chain of ten carbon atoms (4c and 5c) were the most active against two tumoral cell lines: RKO-AS-45-1 and HeLa. Micronucleus and TUNEL assays showed that both compounds are mutagenic and induce apoptosis. In addition, Compound 5c altered the cellular actin cytoskeleton in RKO-AS-45-1 cells. The results suggest that Compounds 4c and 5c may be novel prototype anticancer agents.     

Oxidation of hardwood kraft-lignin to phenolic derivatives with oxygen as oxidant

 A hardwood kraft lignin was oxidized in alkaline medium to obtain phenolic compounds (syringaldehyde, vanillin and its acids). To avoid lignin condensation, the lignin was precipitated from a black liquor with a calcium salt dissolved in a water soluble alcohol. Oxygen was the oxidant employed, and copper (II) and cobalt (II) salts were used as catalysts. Effect of temperature, reaction time, oxygen pressure, alkali concentration and catalyst on yield and product distribution were studied. In all the range of variables lignin conversion and aldehyde yield remains low and the more important effect on aldehyde yield was due to the alkali concentration, which must be fixed at about 2 N. The precipitation method did not significantly increase the aldehyde yield, in contrast with the results of nitrobenzene and CuO oxidations. In catalyzed oxidations, no increase in phenolic aldehydes was observed and, with some catalyst, the conversion into phenolic derivatives was reduced. Lignin conversion into low molecular weight products is responsible for the low phenolic product yield and the type of catalyst could lead the oxidation into phenolic products or into low molecular weight acids. Received 23 November 1998