Central nervous system signs in chickens caused by a new avian reovirus strain: a pathogenesis study

The present study describes the pathogenesis of infection of chicks with a new avian reovirus strain, belonging to the so-called enteric reovirus strains (ERS) that is capable of causing central nervous system signs in SPF white leghorns. After intramuscular (IM) or oral inoculation birds were either observed for clinical signs or sacrificed for macroscopic, histological and virological examination for 21 days. Virus isolation was performed on the brain, leg muscle, hock joint, liver and spleen. For the detection of viral antigen the immunohistochemistry (IHC) technique was performed on the caudal part of the cerebrum, spinal cord including spinal ganglia and right N. Ischiadicus. High mortality (79% in 7 days) was seen in birds that were inoculated IM. Survivors were depressed and stayed small until the end of the experiment. One bird had tremor and showed torticollis at 9 days after IM inoculation. Birds that were inoculated orally were depressed from day 4 and stayed small until the end of the experiment. One bird showed a torticollis at 10 days after inoculation. After both IM and oral inoculation ERS was isolated from the brain between 3 and 10 days after inoculation. Other examined organs were positive for virus isolation from day 1 or 5 until day 21. IHC revealed viral antigen positive cells in the Plexus chorioideus (plexus epithelial cells or cells within the underlying connective tissue) and in a spinal ganglion. The results indicate that the pathogenesis of ERS infection in chickens bears some resemblance with that of the mammalian reoviruses serotype 1 in mice.     

Molecular analysis of the Arbuscular mycorrhiza symbiosis

The molecular analysis of the arbuscular mycorrhizal (AM) symbiosis started at the beginning of this decade. The paper summarises the work of the ‘Laboratorium für Molekulare Genetik arbuskulärer Mykorrhiza’ at the MPI für terrestrische Mikrobiologie in Marburg on three major topics. Firstly, the plant response to the mycorrhizal colonisation was analysed using both, targeted and non‐targeted approaches. As an example, the localisation of the gst1 mRNA in potato mycorrhiza is shown. Second, molecular techniques were established to analyse gene expression of the fungal partner of the symbiosis. We present a differential RNA display analysis of spore germination in two AM fungi and the cloning of a gene from Glomus mosseae that shows expression at all stages of the fungal life cycle. In the last part, we introduce the work we are carrying out with a new root endophytic fungus, Piriformospora indica. Infection experiments on maize showed that despite the fungus performs as a root necrotroph, it has a positive effect on plant growth.     

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Development of a marker assisted selection program for cacao

ABSTRACT Production of cacao in tropical America has been severely affected by fungal pathogens causing diseases known as witches' broom (WB, caused by Moniliophthora perniciosa), frosty pod (FP, caused by M. roreri) and black pod (BP, caused by Phytophthora spp.). BP is pan-tropical and causes losses in all producing areas. WB is found in South America and parts of the Caribbean, while FP is found in Central America and parts of South America. Together, these diseases were responsible for over 700 million US dollars in losses in 2001 (4). Commercial cacao production in West Africa and South Asia are not yet affected by WB and FP, but cacao grown in these regions is susceptible to both. With the goal of providing new disease resistant cultivars the USDA-ARS and Mars, Inc. have developed a marker assisted selection (MAS) program. Quantitative trait loci have been identified for resistance to WB, FP, and BP. The potential usefulness of these markers in identifying resistant individuals has been confirmed in an experimental F(1) family in Ecuador.     

The function of a leader peptide in translocating charged amino acyl residues across a membrane

Insertion of bacteriophage coat proteins into the membrane of infected bacterial cells can be studied as a model system of protein translocation across membranes. The coat protein of the filamentous bacteriophage Pf3--which infects Pseudomonas aeruginosa--is 44 amino acids in length and has the same basic structure as the coat protein of bacteriophage M13, which infects Escherichia coli. However, unlike the Pf3 coat protein, the M13 coat protein is synthesized as a precursor (procoat) with a typical leader (signal) sequence, which is cleaved after membrane insertion. Nevertheless, when the gene encoding the Pf3 coat protein is expressed in E. coli, the protein is translocated across the membrane. Hybrid M13 and Pf3 coat proteins were constructed in an attempt to understand how the Pf3 coat protein is translocated without a leader sequence. These studies demonstrated that the extracellular regions of the proteins determined their cellular location. When three charged residues in this region were neutralized, the leader-free M13 coat protein was also inserted into the membrane. Differences in the water shell surrounding these residues may account for efficient membrane insertion of the protein without a leader sequence.     

No evidence of a circumsolar dust ring from infrared observations of the 1991 solar eclipse

During the past 25 years there have been many attempts to detect a possible dust ring around the sun, with contradictory results. Before the 1991 eclipse, infrared eclipse experiments used single-element detectors to scan the corona along the ecliptic for excess surface brightness peaks. The availability of relatively large-format infrared array detectors now provides a considerable observational advantage: two-dimensional mapping of the brightness and polarization of the corona with high photometric precision. The 1991 eclipse path included the high-altitude Mauna Kea Observatory, a further advantage to measure the corona out to large angular distances from the sun. Results are reported from an experiment conducted on Mauna Kea with a HgCdTe-array detector sensitive to wavelengths between 1 and 2.5 micrometers, using broad-band J, H, and K filters. Although the sky conditions were not ideal, the H- and K-band surface brightnesses clearly show the inhomogeneous structure in the K-corona and the elliptical flattening of the F-corona, but no evidence of a circumsolar, local dust component out to 15 solar radii.     

The V-antigen of Yersinia forms a distinct structure at the tip of injectisome needles

Many pathogenic bacteria use injectisomes to deliver effector proteins into host cells through type III secretion. Injectisomes consist of a basal body embedded in the bacterial membranes and a needle. In Yersinia, translocation of effectors requires the YopB and YopD proteins, which form a pore in the target cell membrane, and the LcrV protein, which assists the assembly of the pore. Here we report that LcrV forms a distinct structure at the tip of the needle, the tip complex. This unique localization of LcrV may explain its crucial role in the translocation process and its efficacy as the main protective antigen against plague.