Abundance Profiles (abundance + profile)

Distribution by Scientific Domains

Selected Abstracts

A potato tuber-expressed mRNA with homology to steroid dehydrogenases affects gibberellin levels and plant development

Christian W.B. Bachem
Summary Using cDNA-AFLP RNA fingerprinting throughout potato tuber development, we have isolated a transcript-derived fragment (TDF511) with strong homology to plant steroid dehydrogenases. During in vitro tuberization, the abundance profile of the TDF shows close correlation to the process of tuber formation. However, when tuberization is inhibited by the addition of gibberellins (GAs) to the growth medium, the appearance of TDF511 in the fingerprint is delayed, then steadily increases in intensity during later stages of development. TDF511 was used to isolate the corresponding cDNA (CB12). The DNA and deduced amino-acid sequences of the cDNA show high homology to a fruit-ripening gene from tomato, a series of steroid dehydrogenases, and the maize Ts2 gene. A section of the cDNA was cloned in antisense orientation behind a 35S CaMV promoter and transformed into potato. Transgenic plants expressing the antisense gene showed significantly earlier emergence, an increase in height, and longer tuber shape. In vitro tuberization experiments reveal extended stolon lengths in comparison to the controls. The analysis of endogenous GA levels showed that the transgenic antisense plants have elevated levels of biologically active GAs and their respective precursors. We propose that this gene plays a role in the metabolism of plant-growth substances important for tuber life cycle and plant development. [source]

Metallicity gradients: Mass dependency in dwarf elliptical galaxies,

M. Koleva
Abstract The formation and evolution of galaxies is imprinted on their stellar population radial gradients. Two recent articles present conflicting results concerning the mass dependence of the metallicity gradients for early-type dwarf galaxies. On one side, Spolaor et al. (2009) show a tight positive correlation between the total metallicity [Z /H] and the mass. On the other side, in a distinct sample, we do not find any trend involving [Fe/H] (Koleva et al. 2009). In order to investigate the origin of the discrepancy, we examine various factors that may affect the determination of the gradients: namely the sky subtraction and the signal-to-noise ratio. We conclude that our detection of gradients are well above the possible analysis biases. Then, we measured the [Mg/Fe] relative abundance profile and found moderate gradients. The derived [Z /H] gradients scatter around ,0.4 dex/re. The two samples contain the same types of objects and the reason of the disagreement is still not understood ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Transcript and activity levels of different Pleurotus ostreatus peroxidases are differentially affected by Mn2+

Roni Cohen
The white-rot fungus Pleurotus ostreatus produces both manganese-dependent peroxidase (MnP) and versatile peroxidase (VP) in non-manganese-amended peptone medium (PM). We studied the effect of Mn2+ supplementation on MnPs and VPs in P. ostreatus by analysing the enzymatic and transcript abundance profiles of the peroxidases, as well as the lignin mineralization rate. The fungus was grown in PM under solid-state conditions using perlite as an inert solid support. Mn2+ amendment resulted in a 1.7-fold increase in [14C]-lignin mineralization relative to unamended medium. Anion-exchange chromatography was used to resolve the fungal peroxidase's enzymatic activity profile. Five peaks (P1,P5) of VP and one peak (P6) of MnP activity were detected in unamended medium. In Mn2+ -amended medium, a reduction in the activity of the VPs was observed. On the other hand, a sharp increase in the MnP activity level of peak P6 was detected. The P6 isoenzyme was purified and showed manganese-dependent peroxidation of phenolic substrates. Internal sequence analysis of the purified enzyme revealed 100% identity with the deduced amino acid sequence of P. ostreatus MnP3 (GenBank AB016519). The effect of Mn2+ on the relative abundance of gene transcripts of three VPs and one MnP from P. ostreatus was monitored using reverse transcription,polymerase chain reaction (RT,PCR) with oligonucleotide primer sets synthesized on the basis of non-conserved sequences of the different peroxidases. The reduction in VP gene transcript abundance and the increase in mnp3 transcript level were collinear with the changes observed in the enzyme activity profiles. These results indicate that the activity of peroxidases is regulated at the transcriptional level. We suggest that the expression of MnP and VP may be differentially regulated by the presence of Mn2+. [source]

Effect of turbulent diffusion on iron abundance profiles

P. Rebusco
ABSTRACT We compare the observed peaked iron abundance profiles for a small sample of groups and clusters with the predictions of a simple model involving the metal ejection from the brightest galaxy and the subsequent diffusion of metals by stochastic gas motions. Extending the analysis of Rebusco et al., we found that for five out of eight objects in the sample an effective diffusion coefficient of the order of 1029 cm2 s,1 is needed. For AWM4, Centaurus and AWM7 the results are different suggesting substantial intermittence in the process of metal spreading across the cluster. There is no obvious dependence of the diffusion coefficient on the mass of the system. We also estimated the characteristic velocities and the spatial scales of the gas motions needed to balance the cooling losses by the dissipation of the same gas motions. A comparison of the derived spatial scales and the sizes of observed radio bubbles inflated in the ICM by a central active galactic nucleus (AGN) suggests that the AGN/ICM interaction makes an important (if not a dominant) contribution to the gas motions in the cluster cores. [source]