Recognition of nucleoplasmin by its nuclear transport receptor importin α/β: insights into a complete import complex

Nuclear import of the pentameric histone chaperone nucleoplasmin (NP) is mediated by importin α, which recognizes its nuclear localization sequence (NLS), and importin β, which interacts with α and is in charge of the translocation of the NP/α/β complex through the nuclear pore. Herein, we characterize the assembly of a functional transport complex formed by full-length NP with importin α/β. Isothermal titration calorimetry (ITC) was used to analyze the thermodynamics of the interactions of importin α with β, α with NP, and the α/β heterodimer with NP. Our data show that binding of both importin α and α/β to NP is governed by a favorable enthalpic contribution and that NP can accommodate up to five importin molecules per NP pentamer. Phosphomimicking mutations of NP, which render the protein active in histone chaperoning, do not modulate the interaction with importin. Using small-angle X-ray scattering, we model the α/β heterodimer, NP/α, and NP/α/β solution structures, which reveal a glimpse of a complete nuclear import complex with an oligomeric cargo protein. The set of alternative models, equally well fitting the scattering data, yields asymmetric elongated particles that might represent consecutive geometries the complex can adopt when stepping through the nuclear pore.     

Monitoring forest plant biodiversity changes and developing conservation strategies: a study from Camili Biosphere Reserve Area in NE Turkey

This study was carried out in forestland of Camili Biosphere Reserve (CBR) area in NE Turkey. It was designed to evaluate the consequences of disturbances on changes in secondary forest succession from 1985 to 2005 for monitoring forest plant biodiversity changes and developing conservation strategies. The successional stages were mapped using Geographic Information System (GIS), Global Positioning System (GPS), aerial photos and high resolution satellite images (IKONOS). The results showed that stable stage decreased about 77.96% over the last 20-year time period. Although 701.6 ha conifer forests existed in competition and reaction stages in 1985, none existed in 2005. In overall, about 33.23% of the area decreased, 42.36% did not change and 24.41% increased in different seral stages. Consequently, 8.83% of the area decreased as a whole to indicate that the forest has been developing from stable to nudation stage, that is to say, retrogressive succession is going on in the area. Forest structure and its relationship with plant biodiversity along with its changes over time were determined using FRAGSTATS. We also investigated spatio-temporal configuration of six secondary forest successional stages and generated structural diversity measures. These measures revealed that the landscape has been fragmented, posing a danger to lose the important components of plant biodiversity. Sustainable management of such degraded forests is of crucial importance for plant biodiversity conservation. In conclusion, the study contributes to the development of a framework for effective conservation of plant biodiversity through plant biodiversity integrated Multiple Use Forest Management (MUFM) plans by using the successional stages and plant biodiversity changes.     

Chemical derivatization of compact disc polycarbonate surfaces for SNPs detection

Compact discs have been proposed as an efficient analytical platform, with potential to develop high-throughput affinity assays for genomics, proteomics, clinics, and health monitoring. Chemical derivatization of CD surfaces is one of the keys to developing highly efficient microarraying-based assays on discs. Approaches for mild chemical modification of polycarbonate (PC) disc surface based on nitration, reduction, and chloromethylation reactions have been developed. Derivatized surfaces as amino and thiol are obtained for PC, maintaining unchanged the mechanical and optical properties of the discs. Studies of covalent attachment of oligonucleotide probes (5' Cy5-labeled, 3' NH 2-ended) on the modified surfaces have been performed to develop microarraying assays based on hybridization of cDNA strands and single nucleotide polymorphism discrimination (SNPs). A demonstration of the applicability to the compact disc audio/video technology for its use as analytical system is performed, including the employment of a commercial CD player to read the results on disc.     

Toxicity of inorganic cadmium salts to the microalga Scenedesmus armatus (Chlorophyta) with respect to medium composition, pH and CO2 concentration

Batch cultures of algae grown at low (0.1 %) and elevated (2.0 %) concentrations of CO₂, as well as in original BBM (Bold Basal Medium) and BBM modified with phosphate, EDTA and a combination of both, were exposed to cadmium (Cd(NO₃)₂·4H₂O, 3CdSO₄·8H₂O and CdCl₂·H₂O) for 24 h. Regardless of the salt applied, the concentration-dependent relationships of Cd toxicity were found to be biphasic, suggesting the different affinity of target sites to cadmium. Nominal values of EC₅₀ obtained for algae grown in original BBM and at low CO₂ were 18.0, 16.44 and 15.37 mg·dm⁻³ for cadmium nitrate, sulphate and chloride, respectively. However, it was estimated that 97 % of the free cadmium in the added salts were bound by components of original BBM such as EDTA, phosphates, chloride and sulphate. The effect of Cd-salts at concentrations corresponding to EC₅₀ values on algae were tested in media with 10-fold reduced phosphates (BBM-P), BBM depleted of EDTA (BBM-EDTA) and of both phosphates and EDTA (BBM-P-EDTA). For algae grown at low CO₂ and BBM-P, cadmium was about 25 % less toxic than those applied in original BBM. Cadmium greatly inhibited (about 85 % of the control) the growth of algae cultured in BBM-EDTA; this effect was only slightly dependent on the CO₂ concentration. Deficits of both EDTA and P led to effects similar to those brought about by the absence of EDTA only. The toxicity of cadmium depends on CO₂ concentration only when algae are grown in original BBM. The growth of algae under high CO₂ conditions was reduced considerably less (about 80% of control) compared with low CO₂ concentrations (about 50 % of control). A relationship was found between the toxicity of cadmium salts and final pH values only in variants of low-CO₂ grown algae; with an increase of medium pH the toxicity decreased. The results suggest that both growth conditions and the binding ability of the medium markedly affect the toxicity of cadmium towards microalgae.     

Anti-Oxidative Effect of Elevated CO2 Concentration in the Air on Maize Hybrids Subjected to Severe Chill

Elevated CO₂ concentration (700 cm³ m⁻³, EC) inhibited chill-dependent (7 °C) depression of net photosynthetic rate of two maize hybrids with different sensitivity to low temperature. The rate of superoxide radical formation in leaves, leaf membrane injury, and the decrease in maximal quantum efficiency of photosystem 2 were successfully diminished by the treatment. The protective effect of EC toward stress conditions was prolonged at the recovery phase (20 °C). The genotypic impact on studied parameters was also notable. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of reactive oxygen species and development of antioxidative systems during <Emphasis Type="Italic">in vitro</Emphasis> growth and <Emphasis Type="Italic">ex vitro</Emphasis> transfer

Ex vitro transfer is often stressful for in vitro grown plantlets. Water stress and photoinhibition, often accompanying the acclimatization of in vitro grown plantlets to ex vitro conditions, are probably the main factors promoting production of reactive oxygen species (ROS) and in consequence oxidative stress. The extent of the damaging effects of ROS depends on the effectiveness of the antioxidative systems which include low molecular mass antioxidants (ascorbate, glutathione, tocopherols, carotenoids, phenols) and antioxidative enzymes (superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase). This review is focused on ROS production and development of antioxidative system during in vitro growth and their further changes during ex vitro transfer.