Multiscale wolf predation risk for elk: does migration reduce risk?

While migration is hypothesized to reduce predation risk for ungulates, there have been few direct empirical tests of this hypothesis. Furthermore, few studies examined multiscale predation risk avoidance by migrant ungulates, yet recent research reveals that predator–prey interactions occur at multiple scales. We test the predation risk reduction hypothesis at two spatial scales in a partially migratory elk (Cervus elaphus) population by comparing exposure of migrant and resident elk to wolf (Canis lupus) predation risk. We used GPS and VHF telemetry data collected from 67 migrant and 44 resident elk over the summers of 2002–2004 in and adjacent to Banff National Park (BNP), Canada. We used wolf GPS and VHF telemetry data to estimate predation risk as a function of the relative probability of wolf occurrence weighted by a spatial density model that adjusted for varying pack sizes. We validated the predation risk model using independent data on wolf-killed elk, and showed that combining wolf presence and spatial density best predicted where an elk was likely to be killed. Predation risk on summer ranges of migrant elk was reduced by 70% compared to within resident elk summer ranges. Because wolves avoided areas near high human activity, however, fine-scale selection by resident elk for areas near high human activity reduced their predation risk exposure to only 15% higher than migrants, a difference significant in only one of three summers. Finally, during actual migration, elk were exposed to 1.7 times more predation risk than residents, even though migration was rapid. Our results support the hypothesis that large-scale migrations can reduce predation. However, we also show that where small-scale spatial variation in predation risk exists, nonmigratory elk may equally reduce predation risk as effectively as migrants under some circumstances.     

Interphase chromosome arrangement in Arabidopsis thaliana is similar in differentiated and meristematic tissues and shows a transient mirror symmetry after nuclear division

Whole-mount fluorescence in situ hybridization (FISH) was applied to Arabidopsis thaliana seedlings to determine the three-dimensional (3D) interphase chromosome territory (CT) arrangement and heterochromatin location within the positional context of entire tissues or in particular cell types of morphologically well-preserved seedlings. The interphase chromosome arrangement was found to be similar between all inspected meristematic and differentiated root and shoot cells, indicating a lack of a gross reorganization during differentiation. The predominantly random CT arrangement (except for a more frequent association of the homologous chromosomes bearing a nucleolus organizer) and the peripheric location of centromeric heterochromatin were as previously observed for flow-sorted nuclei, but centromeres tend to fuse more often in nonendoreduplicating cells and NORs in differentiated cells. After mitosis, sister nuclei revealed a symmetric arrangement of homologous CTs waning with the progress of the cell cycle or in the course of differentiation. Thus, the interphase chromosome arrangement in A. thaliana nuclei seems to be constrained mainly by morphological features such as nuclear shape, presence or absence of a nucleolus organizer on chromosomes, nucleolar volume, and/or endopolyploidy level.     

Targeted metabolomics analysis of Campylobacter coli VC167 reveals legionaminic acid derivatives as novel flagellar glycans

Glycosylation of Campylobacter flagellin is required for the biogenesis of a functional flagella filament. Recently, we used a targeted metabolomics approach using mass spectrometry and NMR to identify changes in the metabolic profile of wild type and mutants in the flagellar glycosylation locus, characterize novel metabolites, and assign function to genes to define the pseudaminic acid biosynthetic pathway in Campylobacter jejuni 81-176 (McNally, D. J., Hui, J. P., Aubry, A. J., Mui, K. K., Guerry, P., Brisson, J. R., Logan, S. M., and Soo, E. C. (2006) J. Biol. Chem. 281, 18489-18498). In this study, we use a similar approach to further define the glycome and metabolomic complement of nucleotide-activated sugars in Campylobacter coli VC167. Herein we demonstrate that, in addition to CMP-pseudaminic acid, C. coli VC167 also produces two structurally distinct nucleotide-activated nonulosonate sugars that were observed as negative ions at m/z 637 and m/z 651 (CMP-315 and CMP-329). Hydrophilic interaction liquid chromatography-mass spectrometry yielded suitable amounts of the pure sugar nucleotides for NMR spectroscopy using a cold probe. Structural analysis in conjunction with molecular modeling identified the sugar moieties as acetamidino and N-methylacetimidoyl derivatives of legionaminic acid (Leg5Am7Ac and Leg5AmNMe7Ac). Targeted metabolomic analyses of isogenic mutants established a role for the ptmA-F genes and defined two new ptm genes in this locus as legionaminic acid biosynthetic enzymes. This is the first report of legionaminic acid in Campylobacter sp. and the first report of legionaminic acid derivatives as modifications on a protein.     

A nested case-control study of lung cancer risk and ionizing radiation exposure at the portsmouth naval shipyard

Results have been inconsistent between studies of lung cancer risk and ionizing radiation exposures among workers at the Portsmouth Naval Shipyard (PNS). The purpose of this nested case-control study was to evaluate the relationship between lung cancer risk and external ionizing radiation exposure while adjusting for potential confounders that included gender, radiation monitoring status, smoking habit surrogates (socioeconomic status and birth cohort), welding fumes and asbestos. By incidence density sampling, we age-matched 3,291 controls selected from a cohort of 37,853 civilian workers employed at PNS between 1952 and 1992 with 1,097 lung cancer deaths from among the same cohort. Analyses using conditional logistic regression were conducted in various model forms: log-linear (main), linear excess relative risk (ERR), and categorical. Lung cancer risk was positively associated with occupational dose (OR = 1.02 at 10 mSv; 95% CI 0.99- 1.04) but flattened after the inclusion of work-related medical X-ray doses (OR = 1.00; 95% CI 0.98-1.03) in multivariate analyses. Similar risk estimates were observed in the linear ERR model at 10 mSv of cumulative exposure with a 15-year lag.     

Extending the host range of Listeria monocytogenes by rational protein design

In causing disease, pathogens outmaneuver host defenses through a dedicated arsenal of virulence determinants that specifically bind or modify individual host molecules. This dedication limits the intruder to a defined range of hosts. Newly emerging diseases mostly involve existing pathogens whose arsenal has been altered to allow them to infect previously inaccessible hosts. We have emulated this chance occurrence by extending the host range accessible to the human pathogen Listeria monocytogenes by the intestinal route to include the mouse. Analyzing the recognition complex of the listerial invasion protein InlA and its human receptor E-cadherin, we postulated and verified amino acid substitutions in InlA to increase its affinity for E-cadherin. Two single substitutions increase binding affinity by four orders of magnitude and extend binding specificity to include formerly incompatible murine E-cadherin. By rationally adapting a single protein, we thus create a versatile murine model of human listeriosis.     

Impact of environmental and endogenous factors on endopolyploidization in angiosperms

Endopolyploidy (EP) is due to consecutive replication cycles not alternating with mitotic nuclear divisions. Previously it was shown, that EP strongly correlates with the phylogenetic position of a taxon, more weakly with the life strategy and slightly negative with the genome size. Here we wanted to investigate the plasticity of endopolyploidization in response to naturally occurred changes of ploidy levels and long-term as well as short-term changes of environmental factors. Contrary to artificially generated polyploids, natural polyploids show a lower EP level than the corresponding diploids.

Different nutritive supply does not significantly alter the EP level, while temperature may influence EP occasionally. Out of five investigated species, two (Arabidopsis thaliana, Brassicaceae and Lapsana communis, Asteraceae) showed a negative correlation between EP and temperature.

Among 10 species of 5 different families, growing in habitats atypical for the family or showing untypical life strategies, only one, the annual Galinsoga parviflora, deviates from the EP characteristics of its family by exhibiting endopolyploidy.

Apparently, significant immediate alterations of the EP level are the exception rather than the rule when environmental conditions or basic ploidy levels are modified, while in an evolutionary term selective effects may well occur.     

Monitoring the expression of green fluorescent protein in carrot

Green fluorescent protein (GFP) was successfully used as a visual reporter at various stages of carrot (Daucus carota L.) transformation. GFP-fluorescence was non-invasively observed in protoplasts, callus and plants after the delivery of mgfp5-er gene using two transformation methods: direct DNA transfer into polyethylene glycol (PEG) -treated protoplasts and inoculation of root discs with Agrobacterium rhizogenes. Transient GFP-expression was detected in the treated protoplasts and monitored during the first week of the cell culture until the stable level of expression was observed. It was useful for the comparison of protoplast susceptibility to DNA uptake and the transgene expression as the fluorescence declined with various rates depending on the used carrot genotype and PEG-concentration. GFP-monitoring in callus enabled the selection of stably expressing lines. It also allowed verification of the homogeneous tissue composition with regard to the expression of the transgene. In plants, GFP-performance depended on the assayed tissue and organ despite of the constitutive 35S promoter. The expression was visually detected in both vegetative and generative parts, but particularly strong fluorescence was observed in leaf marginal meristems, petioles, stems, and styles. Those tissues can be convenient for examination of the transgenic plants during their growth. The results encourage that GFP is a valuable reporter and can be routinely used for optimization of transformation protocol, selection of transformants and monitoring transgenic carrot.     

Flow cytometric analysis reveals different nuclear DNA contents in cultivated Fonio (Digitaria spp.) and some wild relatives from West-Africa

Nuclear DNA amounts of 118 cultivated fonio accessions representing 94 landraces collected from the major growing areas of West-Africa (Benin, Burkina Faso, Guinea, Mali and Togo) and eight accessions of four wild relatives were investigated by Laser flow cytometry. In cultivated species, average 2C-values ranged from 1.848 ± 0.031 pg for Digitaria iburua to 1.956 ± 0.004 pg for D. exilis. In D. exilis landraces the chromosome number was determined at 2n = 36. The closely related wild species D. longiflora and D. ternata showed similar 2C DNA contents of 1.869 ± 0.035 pg and 1.775 ± 0.070 pg, respectively. Distinctly larger genomes were identified for more distant species D. lecardii and D. ciliaris with 2.660 ± 0.070 pg and 2.576 ± 0.030 pg per 2C nucleus, respectively. Intra-specific variations were found to be slight and insignificant, suggesting genome size stability mainly within the cultivated gene pool. These results support the distance of cultivated fonio species D. exilis and D. iburua from D. lecardii and D. ciliaris as well as their close relationships with D. longiflora and D. ternata. Relevance of the results for ploidy level considerations in fonio millets is discussed.