Programmed cell death induced by high levels of cytokinin in Arabidopsis cultured cells is mediated by the cytokinin receptor CRE1/AHK4

High levels of cytokinins (CKs) induce programmed cell death (PCD) both in animals and plant cells. High levels of the CK benzylaminopurine (BA) induce PCD in cultured cells of Arabidopsis thaliana by accelerating a senescence process characterized by DNA laddering and expression of a specific senescence marker. In this report, the question has been addressed whether members of the small family of Arabidopsis CK receptors (AHK2, AHK3, CRE1/AHK4) are required for BA-induced PCD. In this respect, suspension cell cultures were produced from selected receptor mutants. Cell growth and proliferation of all receptor mutant and wild-type cell cultures were similar, showing that the CK receptors are not required for these processes in cultured cells. The analysis of CK metabolites instead revealed differences between wild-type and receptor mutant lines, and indicated that all three receptors are redundantly involved in the regulation of the steady-state levels of isopentenyladenine- and trans-zeatin-type CKs. By contrast, the levels of cis-zeatin-type CKs were controlled mainly by AHK2 and AHK3. To study the role of CK receptors in the BA-induced PCD pathway, cultured cells were analysed for their behaviour in the presence of high levels of BA. The results show that CRE1/AHK4, the strongest expressed CK receptor gene of this family in cultured cells, is required for PCD, thus linking this process to the known CK signalling pathway.     

Description of a new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) from the western Derby eland Taurotragus derbianus derbianus Gray (Artiodactyla: Bovidae) in Senegal

Examination of faecal samples from semi-captive western Derby elands Taurotragus derbianus derbianus Gray, in the Bandia and Fathala Reserves of Senegal, revealed the presence of o?cysts of the genus Eimeria Schneider, 1875 that we considered to represent a new species, Eimeria derbiani n. sp. The new species possesses nearly ellipsoidal o?cysts (length/width ratio 1.3) with a bi-layered wall and an average size of 27.6 × 21.5 μm. E. derbiani possesses a micropyle covered by a micropylar cap and ovoidal, single-layered sporocysts with an average size of 14.9 × 7.7 μm, each with a Stieda body. Sporozoites of E. derbiani possess a large refractile body and a nucleus. Sporulation lasted for 2 days at 23°C. The new species is differentiated from the two species parasitising Taurotragus oryx Pallas, E. canna Triffitt, 1924 and E. triffittae Yakimoff, 1934.     

Involvement of cis-Zeatin, Dihydrozeatin, and Aromatic Cytokinins in Germination and Seedling Establishment of Maize, Oats, and Lucerne

The aims of this study were to monitor endogenous cytokinin levels during germination and early seedling establishment in oats, maize, and lucerne to determine which cytokinin forms are involved in these processes; to quantify the transfer ribonucleic acid (tRNA)-bound cytokinins; and to measure cytokinin oxidase/dehydrogenase (CKX) activity. Cytokinins were identified using UPLC-MS/MS. The predominant free cytokinins present in the dry seeds were dihydrozeatin-type (DHZ) in lucerne and maize and cZ-type (cis-zeatin) in oats. Upon imbibition, there was a large increase in cZ-type cytokinins in lucerne although the cZ-type cytokinins remained at high levels in oats. In maize, the high concentrations of DHZ-type cytokinins decreased prior to radicle emergence. Four tRNA-bound cytokinins [cis-zeatin riboside (cZR)>N ⁶-(2-isopentenyl)adenosine (iPR), dihydrozeatin riboside (DHZR), trans-zeatin riboside (tZR)] were detected in low concentrations in all three species investigated. CKX activity was measured using an in vitro radioisotope assay. The order of substrate preference was N ⁶-(2-isopentenyl)adenine (iP)>trans-zeatin (tZ)>cZ in all three species, with activity fluctuating as germination proceeded. There was a negative correlation between CKX activity and iP concentrations and a positive correlation between CKX activity and O-glucoside levels. As O-glucosides are less resistant to CKX degradation, they may provide a readily available source of cytokinins that can be converted to physiologically active cytokinins required during germination. Aromatic cytokinins made a very small contribution to the total cytokinin pool and increased only slightly during seedling establishment, suggesting that they do not play a major role in germination.     

Novel high-affinity binders of human interferon gamma derived from albumin-binding domain of protein G

Recombinant ligands derived from small protein scaffolds show promise as robust research and diagnostic reagents and next generation protein therapeutics. Here, we derived high-affinity binders of human interferon gamma (hIFNγ) from the three helix bundle scaffold of the albumin-binding domain (ABD) of protein G from Streptococcus G148. Computational interaction energy mapping, solvent accessibility assessment, and in silico alanine scanning identified 11 residues from the albumin-binding surface of ABD as suitable for randomization. A corresponding combinatorial ABD scaffold library was synthesized and screened for hIFNγ binders using in vitro ribosome display selection, to yield recombinant ligands that exhibited K(d) values for hIFNγ from 0.2 to 10 nM. Molecular modeling, computational docking onto hIFNγ, and in vitro competition for hIFNγ binding revealed that four of the best ABD-derived ligands shared a common binding surface on hIFNγ, which differed from the site of human IFNγ receptor 1 binding. Thus, these hIFNγ ligands provide a proof of concept for design of novel recombinant binding proteins derived from the ABD scaffold.     

Epiphytic cyanophytes Xenococcus kerneri and Chamaesiphon minutus on the freshwater red alga Paralemanea catenata (Rhodophyta)

Epiphytes of Paralemanea catenata (Kützing) Vis & Sheath (Rhodophyta) were studied on material from the River Dyje in National Park Podyjí. Longitudinal sections of the thalli were made with help of Cryo Cut Microtome techniques. The epiphytic cyanophytes Xenococcus kerneri Hansgirg and Chamaesiphon minutus (Rostafinski) Lemmermann were recognized on the cortex of the thalli. Our observations of the determined species are discussed.     

Local ranges of phytosociological associations: are they reflected in numerical classification?

In the tradition of European phytosociology, delimitations of vegetation units such as associations are mostly based on data from small areas where more detailed vegetation sampling has been carried out. Such locally delimited vegetation units are often accepted in large-scale synthetic classifications, e.g. national vegetation monographs, and tentatively assigned to a small geographical range, forming groups of similar (vicarious) vegetation units in different small areas. These vicarious units, however, often overlap in species composition and are difficult to recognize from each other. We demonstrate this issue using an example of the classification of dry grasslands (Festuco-Brometea) in the Czech Republic. The standard vegetation classification of the Czech Republic supposes that the majority of accepted associations (66 out of 68) have a restricted distribution in one of the two major regions, Bohemia or Moravia. We compared the classification into traditional associations with the numerical classification of 1440 phytosociological relevés from the Czech Republic, in order to test whether the traditionally recognized associations with small geographical ranges are reflected in numerical classification. In various comparisons, the groups of relevés identified by numerical analysis occupied larger areas than the traditional associations. This suggests that with consistent use of total species composition as the vegetation classification criterion, the resulting classification will usually include more vegetation units with larger geographical ranges, while many of the traditional local associations will disappear.     

The heterochromatin as a marker for protoplast differentiation of <Emphasis Type="Italic">Cucumis sativus</Emphasis>

The protoplast cultures of Cucumis sativus in two culture systems were used to study heterochromatin reassembly during dedifferentiation of isolated protoplasts and their subsequent differentiation into calli and proembryos. Here we show that dedifferentiation of the cucumber mesophyll cells is accompanied by a dramatic reduction in size and numbers of nuclear chromocenters. Although chromocenters were newly established during protoplast culture, the measured relative heterochromatin content differed according to the culture system used. Protoplast culture leading to proembryo formation displayed a lower level of relative heterochromatin content than cultures resulting in calli and the relative heterochromatin content reached values close to those estimated for somatic embryos.     

Understory vegetation in reclaimed and unreclaimed post-mining forest stands

In the Sokolov coal mining district of the Czech Republic, spoil heaps are reclaimed by forest plantations, which are planted directly into the rough substrate (alkaline tertiary clay). We compared the understory that spontaneously developed in seven types of forest stands: one type was unreclaimed stands (spontaneously overgrown by Betula pendula and Salix caprea) and six were plantations, each dominated by one tree genus (Alnus, Larix, Picea, Pinus, Quercus, and Tilia). The age of the stands ranged from 22 to 33 years. The cover of understory plant species in each stand was estimated, and 16 other environmental and community variables were quantified. The number of plant species was highest in Quercus, Larix, and unreclaimed stands, and was negatively correlated with forest canopy cover and with the cover of the understory dominant, the grass Calamagrostis epigejos. Understory composition differed considerably among the types of forest stands and was significantly explained by the measured environmental variables. Forward selection in redundancy analysis indicated that the most important variable driving understory composition was thickness of the fermentation layer, which is clearly connected with soil development. Environmental variables, including fermentation layer, were also affected by the type of forest stand. Therefore, all of the explained variability in understory composition could be attributed to the type of forest stand, which apparently affected the understory by its impact on soil formation. However, the most favorable soil conditions were not favorable for understory development, as they supported mainly C. epigejos, which suppressed other species. Our study also showed that even in the absence of reclamation measures, mining sites can be successfully restored due to spontaneous succession.     

Intensive physical activity increases peripheral blood dendritic cells

We analyzed the frequency and absolute numbers of circulating myeloid and plasmacytoid DCs in peripheral blood and evaluated their maturation status to test the hypothesis that significant physical stress to the body might induce measurable changes in DCs subsets, phenotype and function, which would complete existing knowledge about the response of the cellular immune system to an acute exercise in top sportsmen. We evaluated the heart rate and draw blood samples before and after the physical load in 18 profesional ice-hockey players. We observed an increase in leukocytes numbers with a predominant increase in the population of DCs and lymphocytes after exercise. Both myeloid and plasmacytoid DCs increased significantly. We found a correlation between the increase of peripheral blood DCs and serum epinephrine and norepinephrine levels. Increase in peripheral blood DCs also correlates with the extent of heart rate elevation during exercise.