The Epstein-Barr virus-encoded nuclear antigen EBNA-5 accumulates in PML-containing bodies.

EBNA-5 is one of the Epstein-Barr virus (EBV)-encoded nuclear proteins required for immortalization of human B lymphocytes. In the nuclei of EBV-transformed lymphoblastoid cell lines EBNA-5 is preferentially targetted to distinct nuclear foci. Previously we have shown (W.Q. Jiang, L. Szekely, V. Wendel-Hansen, N. Ringertz, G. Klein, and A. Rosen, Exp. Cell Res. 197:314-318, 1991) that the same foci also contained the retinoblastoma (Rb) protein. Using a similar double immunofluorescence technique, we now show that these foci colocalize with nuclear bodies positive for PML, the promyelocytic leukemia-associated protein. Artificial spreading of the chromatin by exposure to the forces of fluid surface tension disrupts this colocalization gradually, suggesting that the bodies consist of at least two subcomponents. Heat shock or metabolic stress induced by high cell density leads to the release of EBNA-5 from the PML-positive nuclear bodies and induces it to translocate to the nucleoli. In addition to their presence in nuclear bodies, both proteins are occasionally present in nuclear aggregates and doughnut-like structures in which PML is concentrated in an outer shell. Nuclear bodies with prominent PML staining are seen in resting B lymphocytes. This staining pattern does not change upon EBV infection. In freshly infected cells EBNA-5 antigens are first distributed throughout the nucleoplasm. After a few days intensely staining foci develop. These foci coincide with PML-positive nuclear bodies. At a later stage and in established lymphoblastoid cell lines EBNA-5 is almost exclusively present in the PML-positive nuclear foci. The colocalization is restricted to EBV-infected human lymphoblasts. The data presented indicate that the distinct EBNA-5 foci are not newly formed structures but the result of translocation of the viral protein to a specialized domain present already in the nuclei of uninfected cells.     

Monstrilloida (Copepoda) off the Brazilian coast

Seven monstrilloid species of the genera Thaumaleus and Monstrilla (Copepoda) are reported from the Brazilian coast. Occurrence, distribution and ecological information is given for: T. longispinosum, T. rigidum, T. quadridens, M. recticulata, M. grandis, M. dubia and M. rugosa.     

Protein polymorphism inEligmodontia typus. Genetic divergence with other phyllotine cricetids

By means of gel electrophoresis of tissue extracts we have studied protein polymorphism inEligmodontia typus. The analysis was performed on specimens from five population samples collected at different sites in Patagonia (Argentina). Mean heterozygosity (\-h) and proportion of polymorphic loci (P) were determined on the basis of 19 loci. Considering all individuals as one sample, \-h gave a value of 0.16 and P was 70%. Although these values are much higher than those reported for most rodent species, they are very similar to those obtained by us for four species of the genusCalomys and forGraomys griseoflavus. There is a striking genetic identity (I_N=0.99) among populations from regions with different environmental conditions, indicating that the species possesses a common genic pool. Genetic distance with other species of the Phyllotini was estimated. D_N was lower betweenE. typus andCalomys (mean D_N=0.88) than betweenE. typus andGraomys griseoflavus (D_N=1.01). The high morphological similarity between these last two species, especially regarding those characters related to desert life adaptation, could be assigned, at least in part, to convergent evolution.     

Sigma-B, a putative operon encoding alternate sigma factor of Staphylococcus aureus RNA polymerase: molecular cloning and DNA sequencing.

We have identified a gene cluster located on the chromosomal SmaI I fragment of a highly methicillin resistant strain of Staphylococcus aureus, consisting of four open reading frames (ORFs), named after the number of deduced amino acid residues, in the sequential order orf333-orf108-orf159-orf256. The gene cluster showed close similarities to the Bacillus subtilis sigB operon both in overall organization and in primary sequences of the gene products. The complete gene cluster (provisionally named sigma-B or sigB) was preceded by an sigmaA-like promoter (PA) and had an internal sigmaB-like promoter sequence (PB) between orf333 and orf108, suggesting a complex regulatory mechanism. The polypeptides encoded by orf333, -108, -159, and -256 showed 62, 67, 71, and 77% homologies, respectively, with the RsbU, RsbV, RsbW, and SigB polypeptides encoded by the B. subtilis sigB operon. A Tn551 insertional mutant, RUSA168 (insert in orf256 of the staphylococcal sigma-B operon), showed drastic reduction in methicillin resistance (decrease in MIC from 1,600 microg ml-1 to 12 to 25 microg ml-1off     

Statistical analysis for the spatial validity of a model to forecast the daily number of forest fires

In earlier papers a qualitative and quantitative model was developed for predicting the number of forest fires occurring per day. This model permits the forecast at 00.00 hours Universal Time Convention (UTC) of any day (d), the number of forest fires per day for a range of several days (d tod+5) over a particular region. Input data are the number of forest fires in the region during two preceding days (d–2 andd–1) and the type of day (real and evaluated from radiosonde ford–2,d–1,d and predicted from meteorological medium-range forecasts, i.e. of European Centre, ford+1,d+2,d+3,d+4 andd+5. As this model requires data obtained by radiosonde, particularly temperatures and geopotentials at 850 and 700 hPa and dew points (or specific humidity) at 850 hPa, this study investigates the spatial validity of the model in relation to the distance from the radiosonde station (RS). The highest quality forecast is obtained for the region immediately surrounding the RS, and diminishes with increasing distance from it, this being due to the data obtained from the RS not being representative of the atmospheric column over the region. Hence, the derivation of the critical distance for a particular quality level of measurement. Conversely, fixed quality level implies a specific separation between RS and the region for the prediction, with a higher predictive quality implying a shorter distance.     

Characterization of type II protein secretion (xcp) genes in the plant growth-stimulatingPseudomonas putida, strain WCS358

InPseudomonas aeruginosa, the products of thexcp genes are required for the secretion of exoproteins across the outer membrane. Despite structural conservation of the Xcp components, secretion of exoproteins via the Xcp pathway is generally not found in heterologous organisms. To study the specificity of this protein secretion pathway, thexcp genes of another fluorescent pseudomonad, the plant growth-promotingPseudomonas putida strain WCS358, were cloned and characterized. Nucleotide sequence analysis revealed the presence of at least five genes, i.e.,xcpP, Q, R, S, andT, with homology toxcp genes ofP. aeruginosa. Unlike the genetic organization inP. aeruginosa, where thexcp cluster consists of two divergently transcribed operons, thexcp genes inP. putida are all oriented in the same direction, and probably comprise a single operon. Upstream ofxcpP inP. putida, an additional open reading frame, with no homolog inP. aeruginosa, was identified, which possibly encodes a lipoprotein. Mutational inactivation ofxcp genes inP. putida did not affect secretion, indicating that no proteins are secreted via the Xcp system under the growth conditions tested, and that an alternative secretion system is operative. To obtain some insight into the secretory pathway involved, the amino acid sequence of the N-terminus of the major extracellular protein was determined. The protein could be identified as flagellin. Mutations in thexcpQ andR genes ofP. aeruginosa could not be complemented by introduction of the correspondingxcp genes ofP. putida. However, expression of a hybrid XcpR protein, composed of the N-terminal one-third ofP. aeruginosa XcpR and the C-terminal two-thirds ofP. putida XcpR, did restore protein secretion in aP. aeruginosa xcpR mutant.     

Nitrogen losses from perennial grass species

Nitrogen losses from plants may occur through a variety of pathways, but so far, most studies have only quantified losses of nutrients by above-ground litter production. We used ¹⁵N pulse labelling to quantify total nitrogen losses from above- and below-ground plant parts. Using this method we were able to include also pathways other than above-ground litter production. To test the hypothesis that species from nutrient-poor habitats lose less nitrogen than species from more fertile soils, six perennial grasses from habitats with a wide range of nutrient availability were investigated: Lolium perenne, Arrhenatherum elatius, Anthoxanthum odoratum, Festuca rubra, F. ovina and Molinia caerulea. The results of an experiment carried out in pots in a green-house at two fertility levels show that statistically significant losses occur through pathways other than above-ground litter production. In the low fertility treatment, most (70%) losses from L. perenne occurred by litter production, but in Ar. elatius, F. rubra, F. ovina and M. caerulea, more than 50% of labelled N losses took place by root turn-over, leaching or exudation from roots. When nutrient supply increased, the ¹⁵N losses in above-ground dead material increased in all species and in Ar. elatius, A. odoratum and F. rubra the ¹⁵N losses via other pathways decreased. Ranked according to decreasing turnover coefficient the sequence of species was: L. perenne, A. odoratum, F. rubra, F. ovina, Ar. elatius, M. caerulea. These results suggest that species adapted to sites with low availability of nutrients lose less nitrogen (including above- and below-ground losses) than species adapted to more fertile soils.