Doubling Steps Research Articles

Assessment of different anther culture approaches to produce doubled haploids in cucumber (Cucumis sativus L.)

Cucumber is one of the most important vegetable crops worldwide, which makes it a good candidate to produce doubled haploid (DH) lines to accelerate plant breeding. Traditionally, these approaches involved induction of gynogenesis or parthenogenesis with irradiated pollen, which carries some disadvantages compared to androgenesis. Despite this, studies on anther/microspore cultures in cucumber are surprisingly scarce. Furthermore, most of them failed to unambiguously demonstrate the haploid origin of the individuals obtained. In this work we focused on anther cultures using two cucumber genotypes, different previously published protocols for anther culture, different in vitro culture variants to make it more efficient, and most importantly, a combination of flow cytometry and microsatellite molecular markers to evaluate the real androgenic potential and the impact of anther wall tissue proliferation. We developed a method to produce DH plants involving a bud pretreatment at 4 °C, a 35 °C treatment to anthers, culture with BAP and 2,4-D, and induction of callus morphogenesis by an additional 35 °C treatment and sequential culture first in liquid medium in darkness and second in solid medium with light. We also found that factors such as genotype, proliferation of anther wall tissues, orientation of anthers in the culture medium and growth regulator composition of the initial anther culture medium have a remarkable impact. Our rate of chromosome doubling (81%) was high enough to exclude additional chromosome doubling steps. Together, our results present androgenesis as an improvable but yet more convenient alternative to traditional gynogenesis and parthenogenesis-based approaches.

Efficient computation of pairings on Jacobi quartic elliptic curves

Abstract This paper proposes the computation of the Tate pairing, Ate pairing and its variations on the special Jacobi quartic elliptic curve Y 2 = d X 4 + Z 4 $Y^{2}=dX^{4}+Z^{4}$ . We improve the doubling and addition steps in Miller's algorithm to compute the Tate pairing. We use the birational equivalence between Jacobi quartic curves and Weierstrass curves, together with a specific point representation to obtain the best result to date among curves with quartic twists. For the doubling and addition steps in Miller's algorithm for the computation of the Tate pairing, we obtain a theoretical gain up to 27 % $27\%$ and 39 % $39\%$ , depending on the embedding degree and the extension field arithmetic, with respect to Weierstrass curves and previous results on Jacobi quartic curves. Furthermore and for the first time, we compute and implement Ate, twisted Ate and optimal pairings on the Jacobi quartic curves. Our results are up to 27 % $27\%$ more efficient compared to the case of Weierstrass curves with quartic twists.

Faster computation of the Tate pairing

Text This paper proposes new explicit formulas for the doubling and addition steps in Miller's algorithm to compute the Tate pairing on elliptic curves in Weierstrass and in Edwards form. For Edwards curves the formulas come from a new way of seeing the arithmetic. We state the first geometric interpretation of the group law on Edwards curves by presenting the functions which arise in addition and doubling. The Tate pairing on Edwards curves can be computed by using these functions in Miller's algorithm. Computing the sum of two points or the double of a point and the coefficients of the corresponding functions is faster with our formulas than with all previously proposed formulas for pairings on Edwards curves. They are even competitive with all published formulas for pairing computation on Weierstrass curves. We also improve the formulas for Tate pairing computation on Weierstrass curves in Jacobian coordinates. Finally, we present several examples of pairing-friendly Edwards curves. Video For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=nideQo-K9ME/.

N2O emissions of a mature Norway spruce (Picea abies) stand in the Black Forest (southwest Germany) as differentiated by the soil pattern

Nitrous oxide is a greenhouse gas contributing to stratospheric ozone depletion with major sources that derive from soils. Most measurements were performed at well‐aerated or anaerobic sites, excluding common hydromorphic soils (e.g., Gleysols). The main thesis of this study was that the intermediate aeration of such soils promotes N2O emissions. The investigated catena “Wildmooswald,” which is little more than 200 m long, includes common temperate forest soils (n = 7) of three aeration categories (Cambisols, Gleysols, and Histosol). The influence of fluctuating water tables of the Gleysols led to distinctively higher N2O release compared to the Cambisol within the same mature Norway spruce ecosystem. Even a stable “hot spot” of N2O emissions was detected at a Histosol, where artificial drainage created a redox environment comparable to the Gleysols. Ranking the soils according to emission rate results in fairly regular doubling steps; for example, mean annual flux rates in kg N ha−1 yr−1 for the 2.5 years of measurements were −0.1, 0.4, 1.0, 1.9/1.9, 3.2, and 6.4 for Fibric Histosol, Chromic Cambisol, Endoskeletic Cambisol, Histic Gleysol 1/2, Humic Gleysol, and Sapric Histosol, respectively. The annual emission rates (0.93 kg N ha−1 yr−1) of the predominant Cambisols (63.4% of the area) are comparable to other studies, but only 34.3% of intermediately aerated soils led to a redoubling of the average to 1.86 kg N ha−1 yr−1, which is clearly higher than previously presented from temperate forests. Therefore N2O releases of soils are underestimated if soils having intermediate aeration conditions are left unconsidered.

Ultra-violet light generation at 205 nm by two frequency doubling steps of a cw titanium-sapphire laser

We have built a source at 205 nm from a CW titanium-sapphire laser at 820 nm. Two successive frequency doubling steps are made in LBO and BBO crystals. The difficulties encountered with the BBO crystal account for the low output power. In a quasi-continuous regime we obtain 1 mW (peak power) at 205 nm for a fundamental power at 820 nm of 2.2 W. In these conditions, the life time of a point of the BBO crystal is several hours.

Acute exposure to swine dust causes bronchial hyperresponsiveness in healthy subjects

Six urban subjects, with little or no previous experience of farm-work, were exposed to dust while weighing swine for 2-5 h. Three subjects experienced toxic symptoms 4-5 h after the beginning of exposure. Bronchial responsiveness increased in all subjects within 6 h (more than three doubling steps difference in a methacholine test). One week later, airway responsiveness had partly normalized. The mean (interquartile range) cumulative dose of methacholine causing a 20% decrease in forced expiratory volume in one second (FEV1) was 3.1 (1.0-6.6) mg, before exposure, fell to 0.13 (0.01-0.76) mg 6 h after exposure (p < 0.02), and was 0.99 (0.42-1.5) mg one week later (n = 5, p < 0.05), Mean (SD) FEV1 decreased 5 (2)%. The concentration of total dust varied between 9 and 14 mg.m-3 and of endotoxin between 0.1 and 0.5 mu g.m-3. Thus inhalation of swine farm dust, caused a marked increase in bronchial responsiveness in non-sensitized subjects.

Continuous subcutaneous growth hormone releasing factor analogue augments growth hormone secretion in normal male subjects with no desensitization of the somatotroph.

The effects of 8 day continuous subcutaneous (s.c.) infusions of growth hormone releasing hormone analogue (NLE27GRF(1-29)NH2 (GHRH.A)) on growth hormone (GH) secretion were studied in 14 normal adult male volunteers. GHRH.A was administered in doses which ranged from 7.5 to 120 ng/kg/min in doubling steps. Baseline GH profiles obtained during a 24 h infusion of normal saline in each subject were compared with profiles performed on days 1 and 8 of the infusion. Doses above 30 ng/kg/min augmented GH pulse amplitude and frequency. Doses of 60 ng/kg/min and 120 ng/kg/min appeared more satisfactory as these represented doses on the upwards slope of the dose response curve. However, at a dose of 120 ng/kg/min the GH secretion did not return to baseline for 12 of the 24 h. There was no evidence of desensitization or of depletion of the releasable GH pool with any dose. The possibility of treatment of short children with depot preparations of GHRH.A appears promising.

Nucleoside diphosphokinase, an enzyme with step changes in activity during the cell cycle of the fission yeast Schizosaccharomyces pombe. I. Persistence of steps after a block to the DNA-division cycle.

In confirmation of earlier results, nucleoside diphosphokinase is shown to be a 'step' enzyme in Schizosaccharomyces pombe with a sharp doubling in activity at the beginning of the cell cycle. These doubling steps occur at the same time in the cycle in the smaller cells of the mutant wee1.6. An important result is that the activity steps persist with normal cell cycle timing after a block to the DNA-division cycle imposed by the cycle mutants cdc2.33 and cdc2.33wee1.6. This is clear proof that oscillatory controls of some cell cycle events can persist after the main periodic events of the DNA-division cycle have been abolished.

Arabinosyl nucleosides. XXXII. Mechanism of inhibition of L5178y mouse lymphoma cells by 9-β-D-arabinofuranosylguanine

The mechanism of the growth-inhibitory action of 9-β-D-arabinofuranosylguanine (ara-G) on mouse lymphoma cells (L5178y) at the level of nucleic acid synthesis was studied. Ara-G inhibits the cell proliferation at an ED 50 concentration of 12.3 μM. The cells die because of unbalanced growth. At cytostatic concentrations ara-G inhibits the incorporation rate of dThd into DNA to a much higher degree compared to those of the precursors into RNA or proteins. Ara-G has no effect on the induction of DNA polymerase α occurring at the beginning of the S-phase; this compound exerts its inhibitory activity during the S-phase. Ara-G is intracellularly phosphorylated to ara-GTP. It was demonstrated that ara-G is incorporated into DNA but not into RNA; one molecule of ara-G is incorporated per 7050 molecules of deoxyguanosine. The ara-GMP moieties, incorporated into DNA of L5178y cells are not removed during a culture period of 7.7 doubling steps; compared to the controls no reduction of the viability and growth rate was observed.

Enzyme synthesis and potential during induction synchrony in the fission yeast Schizosaccharomyces pombe

The synthesis of three enzymes (aspartate transcarbamylase, ornithine transcarbamylase and alcohol dehydrogenase) was measured after induction synchronisation of Schizosaccharomyces pombe by a 3 h treatment with deoxyadenosine, an inhibitor of DNA synthesis. These enzymes all show a step pattern of periodic synthesis after selection synchrony. After induction synchrony, however, they showed a pattern of continuous increase without doubling steps. It appears that whereas this technique does synchronise DNA synthesis and cell division, it does not synchronise these step enzymes. The potential (rate of derepression) of sucrase and maltase was also measured. This was synchronised and increased in steps. The step occurred during the early part of the period of DNA synthesis. This may indicate that enzyme potential is regulated by gene dosage. The lag between the S period and the potential steps that was found with these enzymes after selection synchrony was not found after induction synchrony. DNA synthesis during induction synchrony was re-examined and was found to start earlier than had previously been reported.