Wide distribution of O157-antigen biosynthesis gene clusters in Escherichia coli

Most Escherichia coli O157-serogroup strains are classified as enterohemorrhagic E. coli (EHEC), which is known as an important food-borne pathogen for humans. They usually produce Shiga toxin (Stx) 1 and/or Stx2, and express H7-flagella antigen (or nonmotile). However, O157 strains that do not produce Stxs and express H antigens different from H7 are sometimes isolated from clinical and other sources. Multilocus sequence analysis revealed that these 21 O157:non-H7 strains tested in this study belong to multiple evolutionary lineages different from that of EHEC O157:H7 strains, suggesting a wide distribution of the gene set encoding the O157-antigen biosynthesis in multiple lineages. To gain insight into the gene organization and the sequence similarity of the O157-antigen biosynthesis gene clusters, we conducted genomic comparisons of the chromosomal regions (about 59 kb in each strain) covering the O-antigen gene cluster and its flanking regions between six O157:H7/non-H7 strains. Gene organization of the O157-antigen gene cluster was identical among O157:H7/non-H7 strains, but was divided into two distinct types at the nucleotide sequence level. Interestingly, distribution of the two types did not clearly follow the evolutionary lineages of the strains, suggesting that horizontal gene transfer of both types of O157-antigen gene clusters has occurred independently among E. coli strains. Additionally, detailed sequence comparison revealed that some positions of the repetitive extragenic palindromic (REP) sequences in the regions flanking the O-antigen gene clusters were coincident with possible recombination points. From these results, we conclude that the horizontal transfer of the O157-antigen gene clusters induced the emergence of multiple O157 lineages within E. coli and speculate that REP sequences may involve one of the driving forces for exchange and evolution of O-antigen loci.     

Evolutionary dynamics of Rh2 opsins in birds demonstrate an episode of accelerated evolution in the New World warblers (Setophaga)

Low rates of sequence evolution associated with purifying selection can be interrupted by episodic changes in selective regimes. Visual pigments are a unique system in which we can investigate the functional consequences of genetic changes, therefore connecting genotype to phenotype in the context of natural and sexual selection pressures. We study the RH2 and RH1 visual pigments (opsins) across 22 bird species belonging to two ecologically convergent clades, the New World warblers (Parulidae) and Old World warblers (Phylloscopidae) and evaluate rates of evolution in these clades along with data from 21 additional species. We demonstrate generally slow evolution of these opsins: both Rh1 and Rh2 are highly conserved across Old World and New World warblers. However, Rh2 underwent a burst of evolution within the New World genus Setophaga, where it accumulated substitutions at 6 amino acid sites across the species we studied. Evolutionary analyses revealed a significant increase in d_N/d_S in Setophaga, implying relatively strong selective pressures to overcome long‐standing purifying selection. We studied the effects of each substitution on spectral tuning and found they do not cause large spectral shifts. Thus, substitutions may reflect other aspects of opsin function, such as those affecting photosensitivity and/or dark–light adaptation. Although it is unclear what these alterations mean for colour perception, we suggest that rapid evolution is linked to sexual selection, given the exceptional plumage colour diversification in Setophaga.     

A novel vaccine strategy to induce mycobacterial antigen-specific Th1 responses by utilizing the C-terminal domain of heat shock protein 70

Heat shock protein 70 (HSP70) is a member of a highly conserved superfamily of intracellular chaperones called stress proteins that can activate innate and adaptive immune responses. We evaluated the effect of a fusion DNA vaccine that encoded mycobacterial HSP70 and MPT51, a major secreted protein of Mycobacterium tuberculosis. Spleen cells from mice immunized with fusion DNA of full-length HSP70 and MPT51 produced a higher amount of interferon-γ (IFN-γ) in response to the CD4+, but not the CD8+ T-cell epitope peptide on MPT51 than those from mice immunized with MPT51 DNA. Furthermore, because HSP70 comprises the N-terminal ATPase domain and the C-terminal peptide-binding domain, we attempted to identify the domain responsible for its enhancing effect. The fusion DNA vaccine that encoded the C-terminal domain of HSP70 and MPT51 induced a higher MPT51-specific IFN-γ production by CD4+ T cells than the vaccine that encoded MPT51 alone, whereas that with the N-terminal domain did not. Similar results were obtained by immunization with the fusion proteins. These results suggest that the DNA vaccine that encodes a chimeric antigen molecule fused with mycobacterial HSP70, especially with its C-terminal domain, can induce a stronger antigen-specific T-helper cell type 1 response than antigen DNA alone.     

Expression of a C3 plant Rubisco SSU gene in regenerated C4 Flaveria plants

We report the successful transformation, via Agrobacterium tumefaciens infection, and regeneration of two species of the genus Flaveria: F. brownii and F. palmeri. We document the expression of a C₃ plant gene, an abundantly expressed ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit gene isolated from petunia, in these C₄ plants. The organ-specific expression of this petunia gene in Flaveria brownii is qualitatively identical to its endogenous pattern of expression.     

Effects of Sugars on the Glucosylation of Exogenous Hydroquinone by Catharanthus roseus Cells in Suspension Culture

The effects of sugars on the glucosylation of exogenous hydroquinone(HQ) was investigated by supplying individual sugars simultaneouslywith HQ to a suspension culture of Catharanthus roseus cells.The production of arbutin was enhanced as much as 2- to 3-foldby sucrose or glucose at concentrations of up to 6%, with theenhancement being directly dependent on the concentration ofthe sugar. The exogenously added sugar was not metabolized andremained unchanged. Sorbitol also promoted the production ofarbutin in a similar manner. Sucrose improved the viability of cells and, in cultures suppliedwith sucrose and HQ, the activity of UDP-glucose: hydroquinoneglucosyltransferase increased over a much longer period of timethan that in control cultures supplemented with HQ only. (Received December 11, 1989; Accepted March 26, 1990)     

Atypical Protein Kinase C Zeta: Potential Player in Cell Survival and Cell Migration of Ovarian Cancer

Ovarian cancer is one of the most aggressive gynaecological cancers, thus understanding the different biological pathways involved in ovarian cancer progression is important in identifying potential therapeutic targets for the disease. The aim of this study was to investigate the potential roles of Protein Kinase C Zeta (PRKCZ) in ovarian cancer. The atypical protein kinase C isoform, PRKCZ, is involved in the control of various signalling processes including cell proliferation, cell survival, and cell motility, all of which are important for cancer development and progression. Herein, we observe a significant increase in cell survival upon PRKCZ over-expression in SKOV3 ovarian cancer cells; additionally, when the cells are treated with small interference RNA (siRNA) targeting PRKCZ, the motility of SKOV3 cells decreased. Furthermore, we demonstrate that over-expression of PRKCZ results in gene and/or protein expression alterations of insulin-like growth factor 1 receptor (IGF1R) and integrin beta 3 (ITGB3) in SKOV3 and OVCAR3 cells. Collectively, our study describes PRKCZ as a potential regulatory component of the IGF1R and ITGB3 pathways and suggests that it may play critical roles in ovarian tumourigenesis.     

The Importance of the Human Footprint in Shaping the Global Distribution of Terrestrial,Freshwater and Marine Invaders

Human activities such as transport, trade and tourism are likely to influence the spatial distribution of non-native species and yet, Species Distribution Models (SDMs) that aim to predict the future broad scale distribution of invaders often rely on environmental (e.g. climatic) information only. This study investigates if and to what extent do human activities that directly or indirectly influence nature (hereafter the human footprint) affect the global distribution of invasive species in terrestrial, freshwater and marine ecosystems. We selected 72 species including terrestrial plants, terrestrial animals, freshwater and marine invasive species of concern in a focus area located in NW Europe (encompassing Great Britain, France, The Netherlands and Belgium). Species Distribution Models were calibrated with the global occurrence of species and a set of high-resolution (9×9 km) environmental (e.g. topography, climate, geology) layers and human footprint proxies (e.g. the human influence index, population density, road proximity). Our analyses suggest that the global occurrence of a wide range of invaders is primarily limited by climate. Temperature tolerance was the most important factor and explained on average 42% of species distribution. Nevertheless, factors related to the human footprint explained a substantial amount (23% on average) of species distributions. When global models were projected into the focus area, spatial predictions integrating the human footprint featured the highest cumulative risk scores close to transport networks (proxy for invasion pathways) and in habitats with a high human influence index (proxy for propagule pressure). We conclude that human related information–currently available in the form of easily accessible maps and databases—should be routinely implemented into predictive frameworks to inform upon policies to prevent and manage invasions. Otherwise we might be seriously underestimating the species and areas under highest risk of future invasions.