Spacing patterns of an Acacia tree in the Kalahari over a 61-year period: How clumped becomes regular and vice versa

Nearest tree neighbour distances and the tree spatial formation on a large scale over time and space replicates were examined. The study was conducted in a natural savanna ecosystem in the Southern Kalahari, South Africa. Nearest tree neighbour and point pattern analysis methods were used to investigate changes in the spatial pattern of trees in two plots. Trees larger than 2 m canopy diameter were mapped. We used aerial photographs of the study area from 1940, 1964, 1984, 1993, and a satellite image from 2001 to follow two plots over time. Field work was carried out too for classification accuracy. We were able to identify and individually follow over 2400 individual trees from 1940 until 2001. Nearest neighbour analysis results indicate that dead trees were on average closer to their nearest neighbouring trees than living trees were to their neighbours. Most dead trees were on average 6 m from their nearest neighbours, while most living trees were about 20 m apart. Point pattern analysis results show a cyclical transition from clumped to random and sequentially to regular tree spacing. These transitions were not correlated across two plots. Generally, decreases in small-scale clumping coincided with periods of high mortality. Our findings show that regular, clumped, and random tree pattern can occur, pending on time, location, and scale within the location.     

Dynamitin mutagenesis reveals protein-protein interactions important for dynactin structure

Dynactin is a highly conserved, multiprotein complex that works in conjunction with microtubule-based motors to power a variety of intracellular motile events. Dynamitin (p50) is a core element of dynactin structure. In the present study, we use targeted mutagenesis to evaluate how dynamitin's different structural domains contribute to its ability to self-associate, interact with dynactin and assemble into a complex with its close binding partner, p24. We show that these interactions involve three distinct structural elements: (i) a previously unidentified dimerization motif in the N-terminal 100 amino acids, (ii) an α-helical motif spanning aa 106–162 and (iii) the C-terminal half of the molecule (aa 213–406), which is predicted to fold into an antiparallel α-helix bundle. The N-terminal half of dynamitin by itself is sufficient to disrupt dynactin, although very high concentrations are required. The ability of mutations in dynamitin's interaction domains to disrupt dynactin in vitro was found to correlate with their inhibitory effects when expressed in cells. We determined that the dynactin subunit, p24, governs dynamitin oligomerization by binding dynamitin along its length. This suppresses aberrant multimerization and drives formation of a protein complex that is identical to the native dynactin shoulder.     

A major QTL and an SSR marker associated with glycoalkaloid content in potato tubers from <Emphasis Type="Italic">Solanum tuberosum </Emphasis>× <Emphasis Type="Italic">S. sparsipilum</Emphasis> located on chromosome I

New potato (Solanum tuberosum) varieties are required to contain low levels of the toxic glycoalkaloids and a potential approach to obtain this is through marker-assisted selection (MAS). Before applying MAS it is necessary to map quantitative trait loci (QTLs) for glycoalkaloid content in potato tubers and identify markers that link tightly to this trait. In this study, tubers of a dihaploid BC(1) population, originating from a cross between 90-HAF-01 (S. tuberosum(1)) and 90-HAG-15 (S. tuberosum(2) x S. sparsipilum), were evaluated for content of alpha-solanine and alpha-chaconine (total glycoalkaloid, TGA) after field trials. In addition, tubers were assayed for TGA content after exposure to light. A detailed analysis of segregation patterns indicated that a major QTL is responsible for the TGA content in tubers of this potato population. One highly significant QTL was mapped to chromosome I of the HAG and the HAF parent. Quantitative trait loci for glycoalkaloid production in foliage of different Solanum species have previously been mapped to this chromosome. In the present research, QTLs for alpha-solanine and alpha-chaconine content were mapped to the same location as for TGA content. Similar results were observed for tubers exposed to light. The simple sequence repeat marker STM5136 was closely linked to the identified QTL.     

Two Distinct <Emphasis Type="Italic">Photobacterium</Emphasis> Populations Thrive in Ancient Mediterranean Sapropels

Eastern Mediterranean sediments are characterized by the periodic occurrence of conspicuous, organic matter-rich sapropel layers. Phylogenetic analysis of a large culture collection isolated from these sediments revealed that about one third of the isolates belonged to the genus Photobacterium. In the present study, 22 of these strains were examined with respect to their phylogenetic and metabolic diversity. The strains belonged to two distinct Photobacterium populations (Mediterranean cluster I and II). Strains of cluster I were isolated almost exclusively from organic-rich sapropel layers and were closely affiliated with P. aplysiae (based on their 16S rRNA gene sequences). They possessed almost identical Enterobacterial Repetitive Intergenic Consensus (ERIC) and substrate utilization patterns, even among strains from different sampling sites or from layers differing up to 100,000 years in age. Strains of cluster II originated from sapropels and from the surface and carbon-lean intermediate layers. They were related to Photobacterium frigidiphilum but differed significantly in their fingerprint patterns and substrate spectra, even when these strains were obtained from the same sampling site and layer. Temperature range for growth (4 to 33°C), salinity tolerance (5 to 100‰), pH requirements (5.5–9.3), and the composition of polar membrane lipids were similar for both clusters. All strains grew by fermentation (glucose, organic acids) and all but five by anaerobic respiration (nitrate, dimethyl sulfoxide, anthraquinone disulfonate, or humic acids). These results indicate that the genus Photobacterium forms subsurface populations well adapted to life in the deep biosphere.     

Spatio-temporal quantification of differential growth processes in root growth zones based on a novel combination of image sequence processing and refined concepts describing curvature production

Differential growth processes in root and shoot growth zones are governed by the transport kinetics of auxin and other plant hormones. While gene expression and protein localization of hormone transport facilitators are currently being unraveled using state-of-the-art techniques of live cell imaging, the quantitative analysis of growth reactions is lagging behind because of a lack of suitable methods. A noninvasive technique, based on digital image sequence processing, for visualizing and quantifying highly resolved spatio-temporal root growth processes was applied in the model plant Arabidopsis thaliana and was adapted to provide precise information on differential curvature production activity within the root growth zone. Comparison of root gravitropic curvature kinetics in wild-type and mutant plants altered in a facilitator for auxin translocation allowed the determination of differences in the location and in the temporal response of curvature along the growth zone between the investigated plant lines. The findings of the quantitative growth analysis performed here confirm the proposed action of the investigated transport facilitator. The procedure developed here for the investigation of differential growth processes is a valuable tool for characterizing the phenomenology of a wide range of shoot and root growth movements and hence facilitates elucidation of their molecular characterization.     

Biosynthesis and accumulation of ergoline alkaloids in a mutualistic association between Ipomoea asarifolia (Convolvulaceae) and a clavicipitalean fungus

Ergoline alkaloids occur in taxonomically unrelated taxa, such as fungi, belonging to the phylum Ascomycetes and higher plants of the family Convolvulaceae. The disjointed occurrence can be explained by the observation that plant-associated epibiotic clavicipitalean fungi capable of synthesizing ergoline alkaloids colonize the adaxial leaf surface of certain Convolvulaceae plant species. The fungi are seed transmitted. Their capacity to synthesize ergoline alkaloids depends on the presence of an intact differentiated host plant (e.g. Ipomoea asarifolia or Turbina corymbosa [Convolvulaceae]). Here, we present independent proof that these fungi are equipped with genetic material responsible for ergoline alkaloid biosynthesis. The gene (dmaW) for the determinant step in ergoline alkaloid biosynthesis was shown to be part of a cluster involved in ergoline alkaloid formation. The dmaW gene was overexpressed in Saccharomyces cerevisiae, the encoded DmaW protein purified to homogeneity, and characterized. Neither the gene nor the biosynthetic capacity, however, was detectable in the intact I. asarifolia or the taxonomically related T. corymbosa host plants. Both plants, however, contained the ergoline alkaloids almost exclusively, whereas alkaloids are not detectable in the associated epibiotic fungi. This indicates that a transport system may exist translocating the alkaloids from the epibiotic fungus into the plant. The association between the fungus and the plant very likely is a symbiotum in which ergoline alkaloids play an essential role.     

Identification and characterization of simple sequence repeat markers from a glandular Origanum vulgare expressed sequence tag

Oregano (Origanum vulgare) and marjoram (Origanum majorana) are two sensorial distinct spices within the genus Origanum (Lamiaceae). Simple sequence repeat (SSR) markers were developed from expressed sequence tags (ESTs) of essential oil glands of O. vulgare. Thirteen EST-SSR loci were evaluated using 20 individual plants of O. vulgare and 19 plants of Origanum majorana. The number of alleles per locus ranged from one to four. All loci developed from O. vulgare successfully cross-amplified in O. majorana.     

Angststörungen in der Schwangerschaft und nach der Geburt:

Anxiety disorders are widespread. In contrast to affective disorders, they are characterized by a high persistence and a low remission rate. A considerable number of women suffer from anxiety disorders not only prior to conception but also throughout the transition into parenthood. The detection of anxiety disorders is complicated by the overlap of somatic and anxiety symptoms. Additionally, certain anxiety syndromes are specifically exacerbated during pregnancy. We present the diagnostic criteria of the most important anxiety disorders and highlight the symptoms that make an adequate diagnosis during pregnancy difficult. We outline the natural course and delineate options for referral and intervention.     

Human cytomegalovirus impairs the function of plasmacytoid dendritic cells in lymphoid organs

Human dendritic cells (DCs) are the main antigen presenting cells (APC) and can be divided into two main populations, myeloid and plasmacytoid DCs (pDCs), the latter being the main producers of Type I Interferon. The vast majority of pDCs can be found in lymphoid organs, where the main pool of all immune cells is located, but a minority of pDCs also circulate in peripheral blood. Human cytomegalovirus (HCMV) employs multiple mechanisms to evade the immune system. In this study, we could show that pDCs obtained from lymphoid organs (tonsils) (tpDCs) and from blood (bpDCs) are different subpopulations in humans. Interestingly, these populations react in opposite manner to HCMV-infection. TpDCs were fully permissive for HCMV. Their IFN-alpha production and the expression of costimulatory and adhesion molecules were altered after infection. In contrast, in bpDCs HCMV replication was abrogated and the cells were activated with increased IFN-alpha production and upregulation of MHC class I, costimulatory, and adhesion molecules. HCMV-infection of both, tpDCs and bpDCs, led to a decreased T cell stimulation, probably mediated through a soluble factor produced by HCMV-infected pDCs. We propose that the HCMV-mediated impairment of tpDCs is a newly discovered mechanism selectively targeting the host's major population of pDCs residing in lymphoid organs.