Species richness and distribution patterns of leaf-inhabiting endophytic fungi in a temperate forest canopy

In 2005, researchers at the Leipzig Canopy Crane Research Facility collected living leaves of four temperate tree species at heights of between 15 and 33 m above the ground. Following surface sterilisation of the leaves, leaf-fragments were cultured on malt extract agar which allowed the growth of endophytic fungi into the surrounding medium. Isolated cultures were identified by morphology and sequence analysis of the D1/D2 region of the large subunit rDNA. Phylogenetic analysis established the taxonomic positions of the fungi. A total of 49 different taxa were identified, representing 20 families and ten orders. With the exception of one basidiomycetous yeast, all taxa belonged to filamentous ascomycetes. Species richness was highest on Tilia cordata and lowest on Quercus robur. Species-accumulation curves showed that the sampling effort was not sufficient to cover the majority of the likely species at the investigation site. Most endophytes proved to be ubiquitous within the canopy of the investigation site, but habitat preferences in terms of different tree species, different light regimes and season (sampling times) were obvious for some abundant endophytes. Apiognomonia errabunda and Aspergillus niger occurred predominantly on Q. robur, Diplodina acerina on Acer pseudoplatanus, one species of Phoma significantly prefered shaded leaves from the lower canopy layer whereas Sordaria fimicola prefered sun-exposed leaves from the upper tree crowns. Seasonal patterns were observed, for example, for A. errabunda, which was abundant in young leaves in the spring and almost completely absent in aged autumn-leaves, thus suggesting the accumulation of antifungal secondary plant metabolites during the growing season. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. Wilfried Morawetz died in March 2007.     

Kinetics of calcium-induced mixing of lipids and aqueous contents of large unilamellar phosphatidylserine vesicles

Calcium ion-induced fusion events in suspensions of large unilamellar phosphatidylserine (PS) liposomes were monitored by fluorescence methods. Mixing of vesicle contents was studied by measuring the increase in terbium emission intensity due to formation of a complex between Tb³⁺ ions and dipicolinic acid trapped in the liposomes. Lipid redistribution was determined with the aid of the resonance transfer of excitaton energy using dipalmitoylphosphatidylethanolamine labelled with the donor N-(7-nitro-2,1,3-benzoxadiazol-4-yl) or the acceptor tetramethylrhodamine at the free amino group. The two methods yielded significantly different results. While recombination of contents could not be detected at Ca²⁺ concentrations below 2.5 mM the threshold concentration for lipid mixing was 1 mM. For saturating Ca²⁺ concentrations (>5 mM Ca²⁺) initial rates were higher by almost an order of magnitude for lipid mixing than for recombination of liposome contents. These observations indicate that the observation of rapid lipid mixing phenomena does not allow one to draw conclusions as to the fate of the enclosed volumes.     

Association patterns and kinship in female reindeer (Rangifer tarandus) during rut

Non-random association of females has been reported in many social species, with kinship being the main mechanism in shaping these associations. Understanding the patterns of association during rut is particularly important in polygynous animals, as this may have implications for inbreeding vulnerability and genetic structuring of populations. However, these patterns are highly dynamic and may be influenced by the population sex ratio and male age structure. We examined females' association in reindeer (Rangifer tarandus), a highly polygynous ungulate, to determine whether genetically related females associate more often than non-kin during rut and whether this association was influenced by the aforementioned factors. During three rutting seasons the male age structure and the sex ratio of the herd was manipulated: two extremely female biased sex ratios, one with only adult males and one with only young males, whereas the third being closer to a more even sex ratio and male age structure. We found that genetic relatedness influenced female association in the mixed male age group, but not in the adult and young male age groups. Highly related females (relatedness ??0.5) associated more closely than unrelated females. Further, period of the rut as well as male age structure and sex ratio had a significant effect on female association. Our study suggests that the female reindeer association during rut is not only influenced by preference for kin but also by male?Cmale competition and male age as well.     

The Sodium-Dependent Inorganic Phosphate Transporter SLC34A1 (NaPi-IIa) Is Not Localized in the Mouse Brain: A Case of Tissue-Specific Antigenic Cross-Reactivity

The sodium-dependent inorganic phosphate transporter NaPi-IIa is expressed in the kidney. Here, the authors used a polyclonal antiserum raised against NaPi-IIa- and NaPi-IIa-deficient mice to characterize its expression in nervous tissue. Western blots showed that a NaPi-IIa immunoreactive band (~90 kDa) was only present in wild-type kidney membranes and not in kidney knockout or wild-type brain membranes. In the water-soluble fraction of wild-type and knockout brains, another band (~50 kDa) was observed; this band was not detected in the kidney. Light and electron microscopic immunohistochemistry using the NaPi-IIa antibodies showed immunolabeling of kidney tubules in wild-type but not knockout mice. In the brain, labeling of presynaptic nerve terminals was present also in NaPi-IIa-deficient mice. This labeling pattern was also produced by the NaPi-IIa preimmune serum. The authors conclude that the polyclonal antiserum is specific toward NaPi-IIa in the kidney, but in the brain, immunolabeling is caused by a cross-reaction of the antiserum with an unknown cytosolic protein that is not present in the kidney. This tissue-specific cross-reactivity highlights a potential pitfall when validating antibody specificity using knockout mouse-derived tissue other than the specific tissue of interest and underlines the utility of specificity testing using preimmune sera.     

New synthetic medium for the culture of premature barley embryos

Summary The preparative procedure is presented for a new, synthetic plant tissue culture medium designed specifically for the culture of excised barley embryos. The medium appears capable of supporting development of premature barley embryos with high survivability.     

Methanol poisoning and long term sequelae – a six years follow-up after a large methanol outbreak

Background  

Mass poisonings with methanol are rare but occur regularly both in developed and in developing countries. Data from the poisoning episodes are often published, but follow-up-data is scarce. We therefore conducted a six year follow-up study after the large methanol outbreak in Estonia in September 2001.