Sex ratio and reproductive effort in the dioecious Juniperus communis subsp. alpina (Suter) Celak. (Cupressaceae) along an altitudinal gradient. (1/40)

The hypothesis that reproductive cost differs between sexes was tested in Juniperus communis subsp. alpina along an altitudinal gradient. Sex ratio (male : female) increased significantly with elevation, and above 2,600 m it was significantly male-biased. The reproductive effort was markedly greater for females than for males at all elevations. However, over 3 years of study, the growth of the females, measured as elongation of the main axes, was similar to that of the males. In both sexes, growth decreased with increasing elevation. Neither size of the ripe seed cones, nor the number of developed seeds per cone varied with elevation. The percentage of filled seeds was significantly greater at higher elevations indicating more favourable conditions for wind pollination in these stands. However, cone production decreased with elevation and so, reproductive success of J. communis subsp. alpina in Sierra Nevada decreases towards both upper and lower altitudinal distribution limits. The results do not support the hypothesis of differential reproductive cost between sexes; thus, alternative arguments to explain the altitudinal variation of sex ratio are discussed.  (+info)

Phytochemical study on American plants I. Two new phenol glucosides, together with known biflavones and diterpene, from leaves of Juniperus occidentalis Hook. (2/40)

Two new phenol glucosides termed juniperosides I (1) and II (2) were isolated, together with known two biflavones, cupressuflavone and amentoflavone and a diterpene, 3beta-hydroxy sandaracopimaric acid, from leaves of Juniperus occidentalis HOOK. (Cupressaceae) collected in Oregon, U.S.A., and their structures were established as (1S)- and (1R)-1-(2'-hydroxy-6'-methylphenyl)ethanol 2'-O-beta-D-glucopyranosides (1, 2), respectively, on the basis of spectral, chemical, and synthetic evidence. The glycosides 1 and 2, as well as the corresponding aglycones 1a and 2a, are apparently novel types of naturally occurring compounds; to our knowledge, isolation of these types of natural phenol derivatives has only rarely been reported from the vegetable kingdom.  (+info)

Vulnerability curves from conifer sapwood sections exposed over solutions with known water potentials. (3/40)

The cohesion-tension (CT) theory requires stability of liquid water in conducting elements under high tensions. This stability has been measured using different methods, some of which yielded contradictory results. In this study a method is presented to establish known tensions in the water inside conifer tracheids, to detect cavitation events under these conditions and to construct vulnerability curves. Tangential sapwood sections of Juniperus virginiana L. were placed closely over the surface of NaCl solutions with water potentials ranging from -0.91 to -7.57 MPa. Water potentials were measured with a thermocouple hygrometer in contact with the section, and ultrasound acoustic emissions (UAE) from the sections were registered with an ultrasound transducer. The emission rate of signals increased with the concentration of the solution. Exposure of 100 microm sections in the airspace over a solution provided optimal conditions for the rupture of the water column: many tracheid walls bordered on air, and water in the lumen came under high tension. Nevertheless, the water remained in the metastable liquid state for periods of many hours. The vulnerability obtained from simultaneous measurements of water potentials and ultrasound acoustic emissions on sapwood sections was substantially higher than from conventionally measured curves of detached branches. It is argued that the isolation of tracheids in a massive organ as well as the rate of potential decline will influence the probability of cavitations at a given water potential and thus the parameters of the vulnerability curve.  (+info)

Crystal structure of Jun a 1, the major cedar pollen allergen from Juniperus ashei, reveals a parallel beta-helical core. (4/40)

Pollen from cedar and cypress trees is a major cause of seasonal hypersensitivity in humans in several regions of the Northern Hemisphere. We report the first crystal structure of a cedar allergen, Jun a 1, from the pollen of the mountain cedar Juniperus ashei (Cupressaceae). The core of the structure consists primarily of a parallel beta-helix, which is nearly identical to that found in the pectin/pectate lyases from several plant pathogenic microorganisms. Four IgE epitopes mapped to the surface of the protein are accessible to the solvent. The conserved vWiDH sequence is covered by the first 30 residues of the N terminus. The potential reactive arginine, analogous to the pectin/pectate lyase reaction site, is accessible to the solvent, but the substrate binding groove is blocked by a histidine-aspartate salt bridge, a glutamine, and an alpha-helix, all of which are unique to Jun a 1. These observations suggest that steric hindrance in Jun a 1 precludes enzyme activity. The overall results suggest that it is the structure of Jun a 1 that makes it a potent allergen.  (+info)

Occurrence of Lewis a epitope in N-glycans of a glycoallergen, Jun a 1, from mountain cedar (Juniperus ashei) pollen. (5/40)

We have determined the structures of N-glycans linked to major allergens in the mountain cedar (Juniperus ashei) pollen, Jun a 1. First, two kinds of the pollen glycoallergen (Jun a 1-A and Jun a 1-B) were purified from partially purified Jun a 1 by cation exchange chromatography. The N-glycans were liberated by hydrazinolysis from the two glycoallergens and the resulting sugar chains were N-acetylated and then coupled with 2-aminopyridine. Three pyridylaminated sugar chains were purified by reversed-phase HPLC and size-fractionation HPLC from Jun a 1-A and Jun a 1-B respectively. The structures were determined by a combination of exo- and endo-glycosidase digestions, two dimensional sugar chain mapping, and electrospray ionization mass spectrometry (ESI-MS) analysis. Structural analysis indicated that Lewis a epitope (Galbeta1-3(Fucalpha1-4)GlcNAcbeta1-) occurs in the N-glycans of the pollen allergens.  (+info)

Modulation of cellular response to cisplatin by a novel inhibitor of DNA polymerase beta. (6/40)

DNA polymerase beta (Pol beta) is an error-prone enzyme whose up-regulation has been shown to be a genetic instability enhancer as well as a contributor to cisplatin resistance in tumor cells. In this work, we describe the isolation of new Pol beta inhibitors after high throughput screening of 8448 semipurified natural extracts. In vitro, the selected molecules affect specifically Pol beta-mediated DNA synthesis compared with replicative extracts from cell nuclei. One of them, masticadienonic acid (MA), is particularly attractive because it perturbs neither the activity of the purified replicative Pol delta nor that of nuclear HeLa cell extracts. With an IC50 value of 8 microM, MA is the most potent of the Pol beta inhibitors found so far. Docking simulation revealed that this molecule could substitute for single-strand DNA in the binding site of Pol beta by binding Lys35, Lys68, and Lys60, which are the main residues involved in the interaction Pol beta/single-strand DNA. Selected inhibitors also affect the Pol beta-mediated translesion synthesis (TLS) across cisplatin adducts; MA was still the most efficient. Therefore, masticadienonic acid sensitized the cisplatin-resistant 2008C13*5.25 human tumor cells. Our data suggest that molecules such as masticadienonic acid could be suitable in conjunction with cisplatin to enhance anticancer treatments.  (+info)

A monoterpene glucoside and three megastigmane glycosides from Juniperus communis var. depressa. (7/40)

A new monoterpene glucoside (1) and three new natural megastigmane glycosides (2-4) were isolated along with a known megastigmane glucoside (5) from twigs with leaves of Juniperus communis var. depressa (Cupressaceae) collected in Oregon, U.S.A., and their structures were determined on the basis of spectral and chemical evidence. In addition, the antibacterial activities of the isolated components against Helicobacter pylori were also investigated.  (+info)

Genetic variation in five Mediterranean populations of Juniperus phoenicea as revealed by inter-simple sequence repeat (ISSR) markers. (8/40)

BACKGROUND AND AIMS: The assessment of the genetic variability and the identification of isolated populations within a given species represent important information to plan conservation strategies on a genetic basis. In this work, the genetic variability in five natural populations of Juniperus phoenicea, three from Sardinia, one from Cyprus and the last one in the Maritime Alps was analysed by means of ISSRs, on the hypothesis that the latter could have been a refugial one during the last glaciation. METHODS: ISSRs were chosen because of their ability to detect variation without any prior sequence information. The use of three primers yielded 45 reproducible, polymorphic bands, which were utilized to estimate the basic parameters of genetic variability and diversity. KEY RESULTS: All of the populations analysed harboured an adequate amount of genetic variability, with H(S) = 0.1299. The proportion of genetic diversity between populations has been estimated by G(ST) = 0.12. The three Sardinian populations are separated, as tested by AMOVA, from the Cyprus and the continental ones. CONCLUSIONS: The results indicate that geographical isolation has represented a major barrier to gene flow in Juniperus phoenicea. This work represents a first step towards a full genetic characterization of a conifer from the Mediterranean, a world biodiversity hotspot confronted with climate change, and thus contributes towards the planning of genetics-informed conservation strategies.  (+info)

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