Phylogeny of five predominant pospiviroid species in Belgium

In Belgium pospiviroids are routinely detected in various hosts. The most frequently found pospiviroids are: Citrus exocortis viroid (CEVd), Chrysanthemum stunt viroid (CSVd), Potato spindle tuber viroid (PSTVd), Tomato apical stunt viroid (TASVd) and Tomato chlorotic dwarf viroid (TCDVd). Apart from the high incidence of pospiviroids in latently-infected ornamentals, viroids have also been found in plants where they cause disease: PSTVd and TCDVd in tomatoes and CSVd in chrysanthemum. In order to gain more epidemiological data on these infections, this study has conducted phylogenetic analyses of Belgian isolates for each of these five pospiviroid species. PSTVd and CEVd-isolates show a clustering depending on host plant identity. This was not observed for TCDVd and TASVd. A very high degree of sequence similarity was noticeable for CSVd-isolates from various hosts. During the past decade, PSTVd and CSVd-infected mother plants have been systematically eradicated in Belgium after positive detection results, also when found in symptomless plants, leading to a decreased trend of these quarantine pests in the past few years. However, other non-quarantine pospiviroid species are still ubiquitously present in many ornamentals. Since these pospiviroids can be equally harmful to crops as the two quarantine pests PSTVd and CSVd, there is still a risk that transmission occurs from symptomless-infected ornamental plants to economically important crops in Belgium such as tomato, pepper and chrysanthemum.     

Recovery and germination of Prosopis juliflora (Sw.) DC seeds after ingestion by goats and cattle

Prosopis juliflora is a perennial shrub introduced in the 1980s to the Baringo District in central Kenya, and became highly invasive starting around the late 1990s. This period coincides with a shift of the composition of ruminant herds from formerly cattle to goats in this area. To assess the possible role of this shift in herd structure on P. juliflora spread, we conducted feeding trials and germination tests to determine the capacity of seeds to survive the passage through the intestinal tract of goats and cattle, comparing germination with chemically scarified and untreated seeds. Recovery of seeds eight days after ingestion was lower from goats (7%) than from cattle (15%) dung. Germination dynamics were similar for seeds that had been manually extracted from pods with those recovered after intestinal passage. Chemically scarified seeds germinated fastest and reached a germination rate of 100% within five days. While no apparent scarification effect was observed, the main contribution of endozoochorous dispersal of Prosopis seeds is their release from the enclosing pod segments, their dispersal away from the mother plant and possibly the provision of nutrients by the dung for their establishment and initial growth.     

The structure of interleukin-2 complexed with its alpha receptor

Interleukin-2 (IL-2) is an immunoregulatory cytokine that binds sequentially to the alpha (IL-2Ralpha), beta (IL-2Rbeta), and common gamma chain (gammac) receptor subunits. Here we present the 2.8 angstrom crystal structure of a complex between human IL-2 and IL-2Ralpha, which interact in a docking mode distinct from that of other cytokine receptor complexes. IL-2Ralpha is composed of strand-swapped "sushi-like" domains, unlike the classical cytokine receptor fold. As a result of this domain swap, IL-2Ralpha uses a composite surface to dock into a groove on IL-2 that also serves as a binding site for antagonist drugs. With this complex, we now have representative structures for each class of hematopoietic cytokine receptor-docking modules.     

History matters: Impact of historical land use on butterfly diversity in clear-cuts in a boreal landscape

In Swedish boreal landscapes, the loss of species-rich semi-natural grasslands is largely due to a long history of agricultural abandonment. Large areas historically managed as meadows have become mature coniferous forest. This study focused on the potential biological legacy following a long period of grassland abandonment. The butterfly fauna in clear-cuts which was historically meadows and abandoned long enough to allow a generation of conifers to mature (70-90 years) was compared with clear-cuts which were historically coniferous forest. The results showed that clear-cuts historically managed as meadows were: (i) much richer in individuals, (ii) more species-rich, and (iii) contained many more grassland specialists than clear-cuts with a history as forest, with many of these species threatened in other parts of Europe.The results from our study demonstrate for the first time, to our knowledge, that the legacy of historical land-use in remnant plant communities can affect butterfly diversity in clear-cuts and hence the large-scale dynamics over a timescale of a full tree rotation. The results of this study have implications for forest management practices. Replanting clear-cuts on land that was previously meadows with deciduous trees or allowing the forest to regenerate naturally instead of planting conifers would make it possible to preserve a greater diversity of habitats for butterflies and other organisms.     

Infection dynamics of the monogenean parasite Gyrodactylus gasterostei on sympatric and allopatric populations of the three-spined stickleback Gasterosteus aculeatus

Parasites with high host specificity maximally depend on their hosts, which should increase the likelihood of coevolution. However, coevolution requires reciprocal selection exerted by the host and the parasite, and thus a considerable level of parasite virulence. In species of the monogenean ectoparasite genus Gyrodactylus consecutive generations are confronted with a single host, which may constrain the evolution of virulence. Transmission, which is often important in the ecology of Gyrodactylus species, may have the opposite effect, but may also lead to the avoidance of coevolutionary arms races. We investigated the potential outcome of coevolution between Gyrodactylus gasterostei Gl?ser, 1974 and its host, the three-spined stickleback (Gasterosteus aculeatus L.) by determining the strength of genotype by genotype (GxG) interactions on two levels: within and between sympatric and allopatric host populations. To do so, we compared the parasite's infection dynamics on laboratory-reared sympatric (Belgian) and allopatric (German) hosts. We found that a parasite line successfully infected a range of sympatric host genotypes (represented by families), while it failed to establish on allopatric hosts. Phylogeographic studies suggest that neutral genetic divergence between the host populations cannot explain this dramatic difference. Provided that this result can be generalised towards other parasite lines, we conclude that coevolution in this host-parasite system is more likely to lead to local adaptation on the population level than to GxG interactions within populations.     

Chiral inversion of R(-) to S(+) ketoprofen in pigs

The S(+) enantiomer of ketoprofen is predominant in the plasma of pigs after administration of racemic ketoprofen, although the occurrence and extent of R(-)-to-S(+) inversion is uncertain. Plasma concentrations of both enantiomers were measured and percentages of S(+) ketoprofen were calculated at different time points after intravenous and oral dosing of pigs with 1.5mg/kg R(-) ketoprofen. S(+) ketoprofen was formed immediately after administration and concentrations exceeded R(-) concentrations after 1h. Absence of pre-systemic inversion was deduced from the lower S(+) percentages after oral administration. A rapid and increasing inversion, reaching a maximum of about 70%, occurred and appeared to be responsible for the predominance of S(+) ketoprofen in pig plasma after administration of the racemate.     

Effect of thermal treatment on the quality of cloudy apple juice

Apple juice from eight different varieties of apples was heated at high-temperature (60-90 degrees C) and short-time (20-100 s) (HTST) combinations. To determine the effect of heating conditions on enzymatic browning and cloud stability in apple juices, the activity of polyphenol oxidase and pectinesterase was analyzed and correlated with the thermal treatment conditions and the quality of the juice. Additional investigations included the measurement of pH value, soluble solid content, titratable acidity, color, and turbidity after 3 and 6 months. The results showed that HTST treatment at 80 degrees C already inactivated polyphenol oxidase, whereas pectinesterase activity was reduced to half and could even at 90 degrees C not be inactivated completely. In fact, highest residual pectinesterase activity was found at 60 degrees C. Heating at 70 degrees C caused stable pectinesterase activity and even a slight increase for 50 and 100 s heating times. Turbidity and lightness increased after HTST treatment. In particular, differences in cloud stability between the varieties were measured. HTST parameters did not correlate with the residual cloud stability after 6 months. The sensory evaluation revealed that only a few combinations were distinguishable. The best stability of cloud and color in relation to heat impact was achieved by HTST treatment between 70 degrees C/100 s and 80 degrees C/20 s.     

Einfluß von NPK auf die Biomasseproduktion und Stickstoffbindung der stengelknöllchenbildenden Gründüngungsleguminosen Sesbania rostrata und Aeschynomene afraspera im Naßreisanbau

Influence of NPK on performance of the stem-nodulating legumes Sesbania rostrata and Aeschynomene afraspera in lowland rice The stem-nodulating tropical legumes S. rostrata and A. afraspera are promising green manure species for the low-input rice farming systems of lowland areas. Nutrient imbalances and soils low in available nutrients can considerably affect the use of biofertilizers. Use of mineral N, P, and K fertilizers in the growth of S. rostrata and A. afraspera as biofertilizers for lowland rice in the Philippines was evaluated. Applied P and K both stimulated growth, nodulation, and N₂ fixation. N accumulation in PK fertilized S. rostrata was about 40% higher than in nonfertilized green manure. Mineral N application (urea) depressed nodulation and N₂ fixation (ARA) in roots and resulted in an increased ARA in stem nodules. The legumes produced more N gains in the presence of small amounts of N. Use of S. rostrata and A. afraspera green manure increased in all cases significantly rice grain yield. Thus integration of mineral N, P, and K fertilizers in a green manurebased rice farming system can considerably improve biofertilizer production and increase rice grain yield.