Aggregative properties of different cell types of the fresh-water spongeEphydatia fluviatilis isolated on ficoll gradients

Summary Cell suspensions of the fresh-watersponge Ephydatia fluviatilis have been fractionated by means ofFicoll gradient centrifugation. Three fractions were isolated. The densest contains archeocyte-like cells only; the intermediate fraction is very rich in choanocytes, and the lightest is a mixture of cell types. Earch fraction shows specificaggregative properties and potentialities to reconstitute functional sponges.It appears that the sequence of reconstitution events can be selectively altered by certain disequilibria in the cell populationThese preliminary results constitute a first approach to the analysis ofcell type specificity in sponges.     

Spontaneous Return of Biodiversity in Restored Subtropical Thicket: Portulacaria afra as an Ecosystem Engineer

An accepted criterion for measuring the success of ecosystem restoration is the return of biodiversity relative to intact reference ecosystems. The emerging global carbon economy has made landscape‐scale restoration of severely degraded Portulacaria afra (spekboom)‐dominated subtropical thicket, by planting multiple rows of spekboom truncheons, a viable land‐use option. Although large amounts of carbon are sequestered when planting a monoculture of spekboom, it is unknown whether this is associated with the return of other thicket biodiversity components. We used available carbon stock data from degraded, restored, and intact stands at one site, and sampled carbon stocks at restored stands at another site in the same plant community. We also sampled plant community composition at both sites. The total carbon stock of the oldest (50 years) post‐restoration stand (250.8 ± 14 t C ha^?1) approximated that of intact stands (245 t C ha^?1) and we observed a general increase in carbon content with restoration age (71.4 ± 24 t C ha^?1 after 35 and 167.9 ± 20 t C ha^?1 after 50 years). A multiple correspondence analysis separated degraded stands from stands under restoration based on ground cover, floristic composition, and total carbon stock. Older post‐restoration and intact stands were clustered according to woody canopy recruit abundance. Our results suggest that spekboom is an ecosystem engineer that promotes spontaneous return of canopy species and other components of thicket biodiversity. The spekboom canopy creates a cooler micro‐climate and a dense litter layer, both likely to favor the recruitment of other canopy species.     

Overexpression of AtBBX29 Improves Drought Tolerance by Maintaining Photosynthesis and Enhancing the Antioxidant and Osmolyte Capacity of Sugarcane Plants

Plant Molecular Biology Reporter - B-box proteins have emerged as prominent mechanisms for controlling growth and developmental processes and in some instances responses to biotic and abiotic...     

Effectiveness of dry heat as a seed sterilisation technique: Implications for ex situ conservation

Seed-borne pathogens are a daily issue for ex situ collection managers who try to solve it using various chemicals more or less harmful to the staff and the plant material stored. The most common physical method for seed sterilisation is moist heat, in contrast to dry heat which is used much less frequently. Consequently, the efficiency of dry heat as disinfection method and the behaviour of seeds undergoing this treatment are currently poorly known, especially for wild species. In this study, seed viability was estimated by performing germination tests according to standard procedures. Germination tests were conducted on 13,200 seeds from 66 wild species of temperate regions belonging to 22 different families. Results indicate that dry seeds exposed to 60°C during 1hour were less infected by seed-borne pathogens in 14% of the cases, whereas no change has been registered in the other cases. For all 66 studied species, no decrease in germination percentage was detected after the heat treatment. Given its positive effect on infection control without affecting seed viability, dry heat treatment as proposed here opens opportunities for seed bank managers, but also for the disinfection of herbarium collections.     

A Panel of Trypanosoma brucei Strains Tagged with Blue and Red-Shifted Luciferases for Bioluminescent Imaging in Murine Infection Models

Background

Genetic engineering with luciferase reporter genes allows monitoring Trypanosoma brucei (T.b.) infections in mice by in vivo bioluminescence imaging (BLI). Until recently, luminescent T.b. models were based on Renilla luciferase (RLuc) activity. Our study aimed at evaluating red-shifted luciferases for in vivo BLI in a set of diverse T.b. strains of all three subspecies, including some recently isolated from human patients.

Methodology/Principal findings

We transfected T.b. brucei, T.b. rhodesiense and T.b. gambiense strains with either RLuc, click beetle red (CBR) or Photinus pyralis RE9 (PpyRE9) luciferase and characterised their in vitro luciferase activity, growth profile and drug sensitivity, and their potential for in vivo BLI. Compared to RLuc, the red-shifted luciferases, CBR and PpyRE9, allow tracking of T.b. brucei AnTaR 1 trypanosomes with higher details on tissue distribution, and PpyRE9 allows detection of the parasites with a sensitivity of at least one order of magnitude higher than CBR luciferase. With CBR-tagged T.b. gambiense LiTaR1, T.b. rhodesiense RUMPHI and T.b. gambiense 348 BT in an acute, subacute and chronic infection model respectively, we observed differences in parasite tropism for murine tissues during in vivo BLI. Ex vivo BLI on the brain confirmed central nervous system infection by all luminescent strains of T.b. brucei AnTaR 1, T.b. rhodesiense RUMPHI and T.b. gambiense 348 BT.

Conclusions/Significance

We established a genetically and phenotypically diverse collection of bioluminescent T.b. brucei, T.b. gambiense and T.b. rhodesiense strains, including drug resistant strains. For in vivo BLI monitoring of murine infections, we recommend trypanosome strains transfected with red-shifted luciferase reporter genes, such as CBR and PpyRE9. Red-shifted luciferases can be detected with a higher sensitivity in vivo and at the same time they improve the spatial resolution of the parasites in the entire body due to the better kinetics of their substrate D-luciferin.     

Use of a Mutated Protoporphyrinogen Oxidase Gene as an Effective In Vitro Selectable Marker System that Also Conveys <Emphasis Type="Italic">in planta</Emphasis> Herbicide Resistance in Sugarcane

Genetic engineering can be used to introduce economically important traits in sugarcane cultivars. Part of any transformation process involves the selection of genetically transformed cells. In this study, an efficient sugarcane in vitro selection system was developed using mutated protophorhyrinogen oxidase (PPO) genes as selectable markers. Two PPO genes, that encode proteins targeted either to the mitochondria or plastid, were isolated from tobacco and maize. Site-directed mutagenesis was used to alter the nucleotide sequence of these genes so that the resulting proteins are less sensitive to diphenylether type herbicides. Sugarcane callus was genetically transformed through particle bombardment with constructs allowing expression of either transgene, and putative transgenic calli were selected on fomesafen. It took approximately 4 weeks to select herbicide resistant calli clones on 10 mg/l fomesafen in the presence of light, which increased the selection pressure, and a further 8 weeks to regenerate resistant plantlets. PCR analysis confirmed that all regenerated putative transgenic sugarcane plants contained the transgene. All transgenic plants showed levels of herbicide resistance when planted in soil.     

The importance of historical myths for the ethnic consciousness of Romanians and ethnic Hungarians in Transylvania

Conclusion The ethnic Hungarians and the Romanians share a number of myths about their ancestors and about their homeland, Transylvania. I fully agree with Anthony D. Smith, who states that the core of ethnic identity is made up of a myth-symbol complex, consisting of myths, symbols, historical memory and key values. According to Smith, myths and symbols guarantee the preservation and the passing down to future generations of ethnic identity.²⁵ The main problem with the ethnic Hungarians and the Romanians of Transylvania is that their convictions are not compatible, they are even contradictory. In the ethnic Hungarians' view, Transylvania is in fact Hungarian, but it was taken from them by Romania in 1920. According to the Romanians, Transylvania is Romanian but for centuries mistakenly considered as Hungarian by the Hungarians. The historical myths are part of the Hungarian as well as the Romanian collective consciousness. They strengthen cohesion within these groups but, as the convictions are incompatible, they widen the gap between them. In my view, these contradictory views are an additional cause of the current mutual oversensitivity, the mutual suspicion and mutual ignorance which characterize the relation between the two ethnic groups. I think that the success of the Romanian nationalist parties such as the PUNR and România Mare ²⁶ among the Romanian villagers of Transylvania ²⁷is partly due to their exploitation of these contradictory myths.However, the differing oral traditions in the villages do not cause open conflicts. That everyone in his own group passes on his own version helps to explain this. In mixed villages like Dumbrava and Mànàstireni, the sensitive issues are not discussed in ethnically mixed groups. Virtually everything to do with history is suppressed in the day-to-day life of the village. Nevertheless, that does not stop one ethnic group from gossiping about the other. Thus, mutual distrust persists. Such a sense of fear is a dangerous breeding-ground because it can easily be exploited by nationalist parties. When anything occurs in politics which appeals to these feelings of fear and distrust, two fronts are lined up in no time. This actually happened as a result of the controversy about the archaeological excavations in Cluj.Fortunately, there is a sufficiently large number of people who realize that this is pointless and who see through the extremist nationalist party leaders' malice. Bearing in mind the tragic example of the former Yugoslavia, they advocate understanding and peaceful interethnic co-existence.I have touched on only one of several conditions for ethnic survival and revival: the shared historical myths. Research in this field is essential if we are to begin to understand, and, thus, perhaps to alleviate, the many social and political problems in this area.Greet Van de Vyver is Aspirant of the National Foundation for Scientific Research of Belgium and a Ph.D. Candidate in the Department of Social and Cultural Anthropology, Catholic University of Leuven in Belgium.     

Regulation of sclerocyte differentiation in the hydroxyurea treated sponge Ephydatia fluviatilis

Abstract. Freshwater sponges ( Ephydatia fluviatilis ) were raised in mineral medium containing hydroxyurea (HU) at a final concentration of 100 μg/ml. The spicules present in these sponges were counted daily. In HU-treated sponges, the regulation mechanisms of skeletogenesis remained functional despite the absence of an aquiferous system. Indeed, as in controls, the differentiation of sclerocytes from stem cells ceased when a critical number of spicules had been secreted. Stem cells again started to differentiate into sclerocytes when isolated from sponges that had completed their skeletogenesis. The number of spicules secreted was found to be an inverse function of silicate concentration. These results demonstrate that the regulation of skeletogenesis is not dependent on the differentiation of the aquiferous system.     

Sigma Factor SigB Is Crucial to Mediate Staphylococcus aureus Adaptation during Chronic Infections

Staphylococcus aureus is a major human pathogen that causes a range of infections from acute invasive to chronic and difficult-to-treat. Infection strategies associated with persisting S. aureus infections are bacterial host cell invasion and the bacterial ability to dynamically change phenotypes from the aggressive wild-type to small colony variants (SCVs), which are adapted for intracellular long-term persistence. The underlying mechanisms of the bacterial switching and adaptation mechanisms appear to be very dynamic, but are largely unknown. Here, we analyzed the role and the crosstalk of the global S. aureus regulators agr, sarA and SigB by generating single, double and triple mutants, and testing them with proteome analysis and in different in vitro and in vivo infection models. We were able to demonstrate that SigB is the crucial factor for adaptation in chronic infections. During acute infection, the bacteria require the simultaneous action of the agr and sarA loci to defend against invading immune cells by causing inflammation and cytotoxicity and to escape from phagosomes in their host cells that enable them to settle an infection at high bacterial density. To persist intracellularly the bacteria subsequently need to silence agr and sarA. Indeed agr and sarA deletion mutants expressed a much lower number of virulence factors and could persist at high numbers intracellularly. SigB plays a crucial function to promote bacterial intracellular persistence. In fact, ΔsigB-mutants did not generate SCVs and were completely cleared by the host cells within a few days. In this study we identified SigB as an essential factor that enables the bacteria to switch from the highly aggressive phenotype that settles an acute infection to a silent SCV-phenotype that allows for long-term intracellular persistence. Consequently, the SigB-operon represents a possible target to develop preventive and therapeutic strategies against chronic and therapy-refractory infections.     

Modulating the proteinase inhibitory profile of a plant cystatin by single mutations at positively selected amino acid sites

Cysteine proteinase inhibitors of the cystatin superfamily have several important functions in plants, including the inhibition of exogenous cysteine proteinases during herbivory or infection. Here we used a maximum-likelihood approach to assess whether plant cystatins, like other proteins implicated in host-pest interactions, have been subject to positive selection during the course of their evolution. Several amino acid sites were identified as being positively selected in cystatins from either Poaceae (monocots) and Solanaceae (dicots). These hypervariable sites were located at strategic positions on the protein: on each side of the conserved glycine residues in the N-terminal trunk, within the first and second inhibitory loops entering the active site of target enzymes, and surrounding the larfav motif, a sequence of unknown function conserved among plant cystatins. Supporting the assumption that positively selected, hypervariable sites are indicative of amino acid sites implicated in functional diversity, mutants of the 8th cystatin unit of tomato multicystatin including alternative residues at positively selected sites in the N-terminal trunk exhibited highly variable affinities for the cysteine proteases papain, cathepsin B and cathepsin H. Overall, these observations support the hypothesis that plant cystatins have been under selective pressure to evolve in response to predatory challenges by herbivorous enemies. They also indicate the potential of site-directed mutagenesis at positively selected sites for the generation of cystatins with improved binding properties.