Gene expression and oxalate oxidase activity of two germin isoforms induced by stress

Wheat germin is a homopentameric 125 kD glycoprotein mainly localized in the cell wall of monocots, and is a specific marker of the onset of growth in germinating seeds. The major objective of this study was to examine the expression and oxalate oxidase activity of two wheat germin isoforms: gf-2.8 and gf-3.8 in transgenic tobacco plants. The transgenic tobacco plants were created with different constructs: 1) one entire excision of gf-2.8 germin promoter and two partially deleted promoter sequences were used to generate 3 independent GUS constructs; 2) the whole gf-2.8 gene construct and the fusion with CaMV 35S promoter; 3) one entire excision of gf-3.8 germin gene and one partially deleted gf-3.8 promoter sequences were used to generate 2 independent GUS constructs; 4) the whole gf-3.8 gene and the fusion with CaMV 35S promoter. Hormonal treatment (auxin and gibberellin), salt treatment, heavy metals (Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg, As) and Al induced high GUS activity in tobacco transformed with entire and one partially deleted of the gf-2.8 gene. The immunoblotting confirmed induction of gf-2.8 gene and its product expressed oxalate oxidase activity in tobacco transformed with the entire gf-2.8 construct. Neither nicotinic acid, salicylic acid, heat shock, cold nor UV-C have enhanced significant GUS activity and germin gf-2.8 synhesis and activity. The germin gf-3.8 constructs with GUS gene and with the entire gf-3.8 sequences gave non-positive response with factors mentioned above. It has been demonstrated that gf-3.8 germin isoform is present as a monomer (M_r 25 kD). The non-active gf-3.8 protein is synthetised in transgenic tobacco plants only under control of the CaMV 35S promoter. Consequently, among two germin isoforms, only the gf-2.8 protein seems to be regulated by hormonal, salt and heavy metal factors. The gf-2.8 oxalate oxidase activity could be then involved in general stress-induced signalling in plant.     

Parasites in hybridizing communities: the Red Queen again?

Over the past two decades, infection levels in hybrids have frequently been compared with those in their progenitor species to find out whether parasites favour or penalize hybridization. Four static infection scenarios are possible, depending on whether hybrid resistance differs from that of one or both parental species. All four alternatives have been supported by some empirical data, but any potential dynamics might have been overlooked because of limited sampling or experimental designs. However, coevolutionary oscillations generated by frequency-dependent selection might provide a better explanation for the observed results than does a static genetic perspective of host resistance.     

Structural studies on exopolysaccharides produced by three different propionibacteria strains

The exopolysaccharides produced by three propionibacteria strains, Propionibacterium freudenreichii 109, Propionibacterium freudenreichii 111, and Propionibacterium thoenii 126, grown on whey-based media, were found to be charged heteropolymers, composed of D-glucose, D-mannose, and D-glucuronic acid in molar ratios of 2:2:1. By means of methylation analysis, mass spectrometry, partial acid hydrolysis, and 1D/2D NMR (1H and 13C) studies, it was determined that all three exopolysaccharides contain the same branched, pentasaccharide repeating unit: [Formula: see text].     

Characterization of ozonated vegetable oils by spectroscopic and chromatographic methods

In this work the effect of ozonation on olive oil, soybean oil, oleic-, linoleic- and linolenic acid was studied. The effects of ozonation time on the oils and acids were analyzed by 1H, 13C NMR. Further, the peroxide- and acid values, the viscosity and the molar mass were determined for pure and ozonated oils. The fatty chains in both ozonated oils showed a gradual decrease of unsaturation with the gradual increase of ozonation time. Reaction products were identified according to Criegee mechanism. The major product in the early stage of the reaction was ozonide. The disappearance of unsaturation and formation of ozonide was almost equal. Ozonation increased the peroxide and acid values for both oils, the increase being higher for soybean oil. After long ozonation times higher molar mass species, as well as low molar mass species were observed. These are interpreted as oligomeric ozonides and cross-ozonides, respectively.     

Structural properties of the human acidic ribosomal P proteins forming the P1-P2 heterocomplex

The ribosome has a morphologically distinct structural feature called the stalk, recognized as a vital element for its function. The ribosomal P proteins constitute the main part of the eukaryotic ribosomal stalk, forming a pentameric structure P0-(P1-P2)(2). The group of P1/P2 proteins in eukaryotes is very diverse, and in spite of functional and structural similarities they do not fully complement one another, probably constituting an adaptive feature of the ribosome from a particular species to diverse environmental conditions. The functional differences among the P1/P2 proteins were analysed in vivo several times; however, a thorough molecular characterization was only done for the yeast P1/P2 proteins. Here, we report a biophysical analysis of the human P1 and P2 proteins, applying mass spectrometry, CD and fluorescence spectroscopy, cross-linking and size exclusion chromatography. The human P1/P2 proteins form stable heterodimer, as it is the case for P1/P2 from yeast. However, unlike the yeast complex P1A-P2B, the human P1-P2 dimer showed a three-state transition mechanism, suggesting that an intermediate species may exist in solution.     

Screening for compounds that induce apoptosis of cancer cells grown as multicellular spheroids

Screening and initial characterization of anticancer drugs are typically performed using monolayer cultures of tumor cells. It is well established that such monolayer cultures do not represent the characteristics of 3-dimensional solid tumors. The multicellular tumor spheroid model is of intermediate complexity between in vivo tumors and in vitro monolayer cultures and would be more suitable for drug screening. The authors describe a procedure in which multicellular spheroids are used to screen for compounds that induce tumor cell apoptosis. Multicellular spheroids were generated in 96-well plates, and apoptosis was determined using the M30-Apoptosense enzyme-linked immunosorbent assay method. A Z' factor of approximately 0.5 was observed for HCT116 colon carcinoma spheroids using staurosporine to induce apoptosis. This procedure is attractive for secondary screening of hits from larger cell-based screens.     

Cancer stem cells: the theory and perspectives in cancer therapy

The cancer stem cell theory elucidates not only the issue of tumour initiation and development, tumour's ability to metastasise and reoccur, but also the ineffectiveness of conventional cancer therapy. This review examines stem cell properties, such as self-renewal, heterogeneity, and resistance to apoptosis. The 'niche' hypothesis is presented, and mechanisms of division, differentiation, self-renewal and signalling pathway regulation are explained. Epigenetic alterations and mutations of genes responsible for signal transmission may promote the formation of cancer stem cells. We also present the history of development of the cancer stem cell theory and discuss the experiments that led to the discovery and confirmation of the existence of cancer stem cells. Potential clinical applications are also considered, including therapeutic models aimed at selective elimination of cancer stem cells or induction of their proper differentiation.