Ecological Succession of a Relict Central European Peat Bog and Variability of Its Insect Biodiversity

The isolated habitat of the ervené Blato bog (South Bohemia, Czech Republic) and its relict insect fauna have been the subject of long-term monitoring. The species composition and abundance of Lepidoptera (light traps) and Coleoptera (pitfall traps) were monitored for 4 years (1994–1997) simultaneously on two sites – in the edaphic climax pine forest and in wetland successional habitats. The method of statistical evaluation by RDA and CCA ordination, representing the habitat preference of species of Coleoptera (Carabidae only) and Lepidoptera (all nocturnal phototactic taxa) between the edaphic climax forest and succession stages, was used. All categories of the peatland taxa (tyrphobiontic, tyrphophilous and tyrphoneutral species) were analysed. Ten highly stenotopic tyrphobiontic species and 23 tyrphophilous species of Lepidoptera (out of 487) were most characteristic of the bog habitat. Only two tyrphophilous carabid species (out of 20) were characteristic of the bog. The most important relict species (tyrphobionts) of Lepidoptera are most diverse and abundant within the successional habitats and in the open wet forest. The relict fauna of the closed climax pine forest is much less diverse and composed mostly of abundant tyrphophilous and tyrphoneutral forest species. Preservation or restoration of sufficiently constant hydrological conditions, which prevents formation of the closed forest, is the basic management for habitat conservation of all relict tyrphobiontic species of the ervené Blato bog and similar peat land habitat islands. The peat bog is a unified complex system of specific diverse and relict taxa. The most specific taxa are tyrphobiontic Lepidoptera, but a number of other vulnerable tyrphophilous and tyrphoneutral insects are associated with the peat bog as well.     

Pa-AGOG, the founding member of a new family of archaeal 8-oxoguanine DNA-glycosylases

Oxidative damage represents a major threat to genomic stability, as the major product of DNA oxidation, 8-oxoguanine (GO), frequently mispairs with adenine during replication. In order to prevent these mutagenic events, organisms have evolved GO-DNA glycosylases that remove this oxidized base from DNA. We were interested to find out how GO is processed in the hyperthermophilic archaeon Pyrobaculum aerophilum, which lives at temperatures around 100°C. To this end, we searched its genome for open reading frames (ORFs) bearing the principal hallmark of GO-DNA glycosylases: a helix–hairpin–helix motif and a glycine/proline-rich sequence followed by an absolutely conserved aspartate (HhH-GPD motif). Interestingly, although the P.aerophilum genome encodes three such ORFs, none of these encodes the potent GO-processing activity detected in P.aerophilum extracts. Fractionation of the extracts, followed by analysis of the active fractions by denaturing polyacrylamide gel electrophoresis, showed that the GO-processing enzyme has a molecular size of ~30 kDa. Mass spectrometric analysis of proteins in this size range identified several peptides originating from P.aerophilum ORF PAE2237. We now show that PAE2237 encodes AGOG (Archaeal GO-Glycosylase), the founding member of a new family of DNA glycosylases, which can remove GO from single- and double-stranded substrates with great efficiency.     

Tagging quantitative trait loci for maturity-corrected late blight resistance in tetraploid potato with PCR-based candidate gene markers

Late blight caused by the oomycete Phytophthora infestans is the economically most important and destructive disease in potato cultivation. Quantitative resistance to late blight available in tetraploid cultivars is correlated with late maturity in temperate climates, which is an undesirable characteristic. A total of 30 DNA-based markers known to be linked to loci for pathogen resistance in diploid potato were selected and tested as polymerase chain reaction-based markers for linkage with quantitative trait loci (QTL) for late blight resistance and plant maturity in two half-sib families of tetraploid potatoes. Most markers originated from within or were physically closely linked to candidate genes for quantitative resistance factors. The families were repeatedly evaluated in the field for quantitative resistance to late blight and maturity. Resistance was corrected for the maturity effect. Nine of eleven different map segments tagged by the markers harbored QTL affecting maturity-corrected resistance. Interactions were found between unlinked resistance QTL, providing testable strategies for marker-assisted selection in tetraploid potato. Based on the linkage observed between QTL for resistance and plant maturity and based on the genetic interactions observed between candidate genes tagging resistance QTL, we discuss models for the molecular basis of quantitative resistance and maturity.     

A prevalent POLG CAG microsatellite length allele in humans and African great apes

The human nuclear gene for the catalytic subunit of mitochondrial DNA polymerase (POLG) contains within its coding region a CAG microsatellite encoding a polyglutamine repeat. Previous studies demonstrated an association between length variation at this repeat and male infertility, suggesting a mechanism whereby the prevalent (CAG)₁₀ allele, which occurs at a frequency of >80% in different populations, could be maintained by selection. Sequence analysis of the POLG CAG microsatellite region of more than 1000 human chromosomes reveals that virtually all allelic variation at the locus is accounted for by length variation of the CAG repeat. Analysis of POLG from African great apes shows that a prevalent length allele is present in each species, although its exact length is species-specific. In common chimpanzee (Pan troglodytes) a number of different sequence variants contribute to the prevalent length allele, strongly supporting the idea that the length of the POLG microsatellite region, rather than its exact nucleotide or amino acid sequence, is what is maintained. Analysis of POLG in other primates indicates that the repeat has expanded from a shorter, glutamine-rich sequence, present in the common ancestor of Old and New World monkeys.     

Bioactivity guided isolation of antifungal compounds from the liverwort Bazzania trilobata (L.) S.F. Gray

A dichloromethane and a methanol extract of the liverwort Bazzania trilobata showed antifungal activity against the phytopathogenic fungi Botrytis cinerea, Cladosporium cucumerinum, Phythophthora infestans, Pyricularia oryzae and Septoria tritici. Bioautography on thin-layer chromatograms was used to isolate six antifungal sesquiterpenes: 5- and 7-hydroxycalamenene, drimenol, drimenal, viridiflorol, gymnomitrol and three bisbibenzyls: 6 ',8'-dichloroisoplagiochin C, isoplagiochin D and 6'-chloroisoplagiochin D. Furthermore we report the isolation of gymnomitr-8(12)-en-4-one and the new coumarin 7,8-dihydroxycoumarin-7-O-beta-D-glucuronide. Their structures have been elucidated based on extensive NMR spectral evidence.     

Cellular and molecular control of dendritic growth and development of cerebellar Purkinje cells

Purkinje cells are the principal neurons of the cerebellar cortex and are characterized by a large and highly branched dendritic tree. For this reason, they have for a long time been an attractive model system to study the regulation of dendritic growth and differentiation. In this article, I will first review studies on different aspects of Purkinje cell dendritic development and then go on to present studies which have aimed at experimentally altering Purkinje cell dendritic development. Some of the cellular and molecular mechanisms which have been shown by these studies to be important determinants of Purkinje cell dendritic development will be discussed, in particular the role of the parallel fiber input, of hormones, and of neuronal growth factors. The organotypic slice culture method will be introduced as an important experimental tool to study Purkinje cell dendritic development under controlled conditions. Using cerebellar slice cultures, protein kinase C (PKC) has been identified as a major determinant of Purkinje cell dendritic development and the contribution of specific isoforms of PKC will be discussed. Finally, it will be shown that Purkinje cell dendritic development in slice cultures does not depend on the activation of glutamate receptors and appears to be independent of the presence of the neurotrophin BDNF. These studies indicate that the initial outgrowth of the Purkinje cell dendritic tree can occur in the absence of signals derived from afferent fibers, but is under control of PKC signaling.     

Genetic diversity of Cryptosporidium spp. in captive reptiles

The genetic diversity of Cryptosporidium in reptiles was analyzed by PCR-restriction fragment length polymorphism and sequence analysis of the small subunit rRNA gene. A total of 123 samples were analyzed, of which 48 snake samples, 24 lizard samples, and 3 tortoise samples were positive for Cryptosporidium: Nine different types of Cryptosporidium were found, including Cryptosporidium serpentis, Cryptosporidium desert monitor genotype, Cryptosporidium muris, Cryptosporidium parvum bovine and mouse genotypes, one C. serpentis-like parasite in a lizard, two new Cryptosporidium spp. in snakes, and one new Cryptosporidium sp. in tortoises. C. serpentis and the desert monitor genotype were the most common parasites and were found in both snakes and lizards, whereas the C. muris and C. parvum parasites detected were probably the result of ingestion of infected rodents. Sequence and biologic characterizations indicated that the desert monitor genotype was Cryptosporidium saurophilum. Two host-adapted C. serpentis genotypes were found in snakes and lizards.     

New molecular screening tools for analysis of free-living diazotrophs in soil

Free-living nitrogen-fixing prokaryotes (diazotrophs) are ubiquitous in soil and are phylogenetically and physiologically highly diverse. Molecular methods based on universal PCR detection of the nifH marker gene have been successfully applied to describe diazotroph populations in the environment. However, the use of highly degenerate primers and low-stringency amplification conditions render these methods prone to amplification bias, while less degenerate primer sets will not amplify all nifH genes. We have developed a fixed-primer-site approach with six PCR protocols using less degenerate to nondegenerate primer sets that all amplify the same nifH fragment as a previously published PCR protocol for universal amplification. These protocols target different groups of diazotrophs and allowed for direct comparison of the PCR products by use of restriction fragment length polymorphism fingerprinting. The new protocols were optimized on DNA from 14 reference strains and were subsequently tested with bulk DNA extracts from six soils. These analyses revealed that the new PCR primer sets amplified nifH sequences that were not detected by the universal primer set. Furthermore, they were better suited to distinguish between diazotroph populations in the different soils. Because the novel primer sets were not specific for monophyletic groups of diazotrophs, they do not serve as an identification tool; however, they proved powerful as fingerprinting tools for subsets of soil diazotroph communities.     

Synthesis of dammarane-type triterpenoids with anti-inflammatory activity in vivo

The 17-alpha-substituted triterpene 1 [(17alpha)-23-(E)-dammara-20,23-diene-3beta,25-diol] showed promising activity in animal models of immunosuppression and inflammation. Using a mouse model for inflammatory skin diseases (oxazolone-induced allergic contact dermatitis, ACD) as the directing in vivo test system, Structure-activity-relationship studies with the aim to understand the necessary structural requirements for the biological activity of 1 were conducted. Furthermore, we anticipated to identify biologically active compounds with the 17beta configuration, which are thermodynamically more stable and much easier to synthesize. This was achieved by identifying the 17-beta substituted dammarane 5B and its analogues.