Molecular phylogeny of the Siphonocladales (Chlorophyta: Cladophorophyceae)

The Siphonocladales are tropical to warm-temperate, marine green macro-algae characterized by a wide variety of thallus morphologies, ranging from branched filaments to pseudo-parenchymatous plants. Phylogenetic analyses of partial large subunit (LSU) rDNA sequences sampled from 166 isolates revealed nine well-supported siphonocladalean clades. Analyses of a concatenated dataset of small subunit (SSU) and partial LSU rDNA sequences greatly clarified the phylogeny of the Siphonocladales. However, the position of the root of the Siphonocladales could not be determined unambiguously, as outgroup rooting and molecular clock rooting resulted in a different root placement. Different phylogenetic methods (likelihood, parsimony and distance) yielded similar tree topologies with comparable internal node resolution. Likewise, analyses under more realistic models of sequence evolution, taking into account differences in evolution between stem and loop regions of rRNA, did not differ markedly from analyses using standard four-state models. The molecular phylogeny revealed that all siphonocladalean architectures may be derived from a single Cladophora-like ancestor. Parallel and convergent evolution of various morphological characters (including those traditionally employed to circumscribe the families and genera) have occurred in the Siphonocladales. Consequently, incongruence with traditional classifications, including non-monophyly in all families and most genera, was shown.     

Species boundaries and phylogenetic relationships within the green algal genus Codium (Bryopsidales) based on plastid DNA sequences

Despite the potential model role of the green algal genus Codium for studies of marine speciation and evolution, there have been difficulties with species delimitation and a molecular phylogenetic framework was lacking. In the present study, 74 evolutionarily significant units (ESUs) are delimited using 227 rbcL exon 1 sequences obtained from specimens collected throughout the genus' range. Several morpho-species were shown to be poorly defined, with some clearly in need of lumping and others containing pseudo-cryptic diversity. A phylogenetic hypothesis of 72 Codium ESUs is inferred from rbcL exon 1 and rps3-rpl16 sequence data using a conventional nucleotide substitution model (GTR+Gamma+I), a codon position model and a covariotide (covarion) model, and the fit of a multitude of substitution models and alignment partitioning strategies to the sequence data is reported. Molecular clock tree rooting was carried out because outgroup rooting was probably affected by phylogenetic bias. Several aspects of the evolution of morphological features of Codium are discussed and the inferred phylogenetic hypothesis is used as a framework to study the biogeography of the genus, both at a global scale and within the Indian Ocean.     

Synthesis and evaluation of a (99m)Tc-BAT-phenylbenzothiazole conjugate as a potential in vivo tracer for visualization of amyloid beta

We have conjugated S,S'-bis-trityl-N-BOC-N'-acetic acid-1,2-ethylenedicysteamine, a protected bis-amino-bis-thiol (BAT) tetraligand, with 2-(4'-aminophenyl)-1,3-benzothiazole, a derivative of thioflavin-T with known affinity for amyloid. The conjugate was efficiently labelled with (99m)Tc by heating of the protected precursor in diluted hydrochloric acid followed by neutralization and heating in the presence of (99m)Tc-tartrate. It was demonstrated that the (99m)Tc-BAT-phenylbenzothiazole conjugate binds in vitro to amyloid beta present in postmortem brain slices of Alzheimer's patients. Despite its high lipophilicity and neutral character, the radiolabelled conjugate did not cross the blood-brain barrier to a sufficient degree and therefore is not useful for detection of Alzheimer's disease. Further evaluation of this (99m)Tc-labelled tracer agent could elucidate its potential usefulness to visualize amyloid plaques in peripheral amyloidosis.     

Flow cytometric detection of type 1 (IL-2, IFN-gamma) and type 2 (IL-4, IL-5) cytokines in T-helper and T-suppressor/cytotoxic cells in rheumatoid arthritis, allergic asthma and atopic dermatitis.

Type 1 cytokines (a.o. IL-2 and IFN-gamma) play an important role in the pathogenesis of rheumatoid arthritis. On the other hand, IgE-mediated diseases such as allergic asthma and atopic dermatitis show a type 2 cytokine (amongst others IL-4 and IL-5) profile.This study examined simultaneously the intracellular production of IL-2, IFN-gamma, IL-4 and IL-5 in T-lymphocytes of patients with rheumatoid arthritis during treatment with methotrexate or salazopyrin, patients with allergic asthma or atopic dermatitis under stable treatment, compared to healthy controls.A three-colour flow cytometric analysis was used for cytokine detection in T-helper cells and T-suppressor/cytotoxic cells.Compared to controls, patients with symptomatic atopic dermatitis showed an increased number of IL-4-producing T-helper lymphocytes in basal circumstances (P=0.001), in contrast to asymptomatic allergic asthma patients. Compared to controls, rheumatoid arthritis patients, treated with salazopyrin, showed an increased number of IL-2-producing T-helper and T-suppressor/cytotoxic lymphocytes after in vitro stimulation with PMA and ionomycin (P=0.01). In contrast, rheumatoid arthritis patients, treated with methotrexate, a more potent disease modifying drug, did not show this type 1 cytokine profile. A positive correlation was found between the number of IFN-gamma producing T-helper cells and disease activity (Ritchie Index and number of swollen joints) in both rheumatoid arthritis patient groups.Active atopic dermatitis patients showed a type 2 cytokine profile, whereas stable asthma patients with lower disease activity did not show a predominance of type 2 cytokines. Rheumatoid arthritis patients under treatment with salazopyrin had a type 1 cytokine profile, which could not be demonstrated in patients treated with methotrexate. This imbalance between type 1 and type 2 cytokines in different immune mediated disorders can be related with treatment and the grade of disease activity. These results stress the need for further investigation of the influence of therapy on cytokine profiles.     

Are the Effects of Response Inhibition on Gambling Long-Lasting?

A recent study has shown that short-term training in response inhibition can make people more cautious for up to two hours when making decisions. However, the longevity of such training effects is unclear. In this study we tested whether training in the stop-signal paradigm reduces risky gambling when the training and gambling task are separated by 24 hours. Two independent experiments revealed that the aftereffects of stop-signal training are negligible after 24 hours. This was supported by Bayes factors that provided strong support for the null hypothesis. These findings indicate the need to better optimise the parameters of inhibition training to achieve clinical efficacy, potentially by strengthening automatic associations between specific stimuli and stopping.     

Tracing the introduction history of the brown seaweed Dictyota cyanoloma (Phaeophyceae,Dictyotales) in Europe

Dictyota cyanoloma has recently been described from the Mediterranean Sea and Macaronesia but doubt had arisen as to whether this species was truly native in Europe. The species is mainly found on non-natural substrata (harbour walls, marinas, boat hulls, etc.), strongly suggesting that it is an introduction. Molecular sequence information from historical herbarium samples proves the presence of D. cyanoloma in the Adriatic Sea as early as 1935. Since approximately the year 2000, however, the number of records as well as the geographic range of the species has expanded significantly. The present-day distribution of D. cyanoloma occupies most of the Mediterranean Sea, Macaronesia, NW Africa and southern Portugal, but recent records from Galicia and SW England (Falmouth, Cornwall) indicate that the species is rapidly expanding northward. Collections from Australia demonstrated that the species is also present from Perth in Western Australia, over much of the southern Australian coastline up to Minnie Water in New South Wales. Phylogenetic analyses resolve D. cyanoloma in a sister clade to a previously unreported Australian Dictyota species. Analysis of genetic diversity of the mitochondrial markers (nad6–nad11 and atp9–orf11) reveals that even though Australian populations contain a much higher haplotype richness, European populations are also fairly diverse. Furthermore, only two out of 25 haplotypes are shared between both regions. These somewhat counterintuitive results could be indicative of a more complicated introduction history.     

Phylogeny and Molecular Evolution of the Green Algae

The green lineage (Viridiplantae) comprises the green algae and their descendants the land plants, and is one of the major groups of oxygenic photosynthetic eukaryotes. Current hypotheses posit the early divergence of two discrete clades from an ancestral green flagellate. One clade, the Chlorophyta, comprises the early diverging prasinophytes, which gave rise to the core chlorophytes. The other clade, the Streptophyta, includes the charophyte green algae from which the land plants evolved. Multi-marker and genome scale phylogenetic studies have greatly improved our understanding of broad-scale relationships of the green lineage, yet many questions persist, including the branching orders of the prasinophyte lineages, the relationships among core chlorophyte clades (Chlorodendrophyceae, Ulvophyceae, Trebouxiophyceae and Chlorophyceae), and the relationships among the streptophytes. Current phylogenetic hypotheses provide an evolutionary framework for molecular evolutionary studies and comparative genomics. This review summarizes our current understanding of organelle genome evolution in the green algae, genomic insights into the ecology of oceanic picoplanktonic prasinophytes, molecular mechanisms underlying the evolution of complexity in volvocine green algae, and the evolution of genetic codes and the translational apparatus in green seaweeds. Finally, we discuss molecular evolution in the streptophyte lineage, emphasizing the genetic facilitation of land plant origins.     

Metal binding properties and structure of a type III metallothionein from the metal hyperaccumulator plant Noccaea caerulescens

Metallothioneins (MT) are low molecular weight proteins with cysteine-rich sequences that bind heavy metals with remarkably high affinities. Plant MTs differ from animal ones by a peculiar amino acid sequence organization consisting of two short Cys-rich terminal domains (containing from 4 to 8 Cys each) linked by a Cys free region of about 30 residues. In contrast with the current knowledge on the 3D structure of animal MTs, there is a striking lack of structural data on plant MTs. We have expressed and purified a type III MT from Noccaea caerulescens (previously Thlaspi caerulescens). This protein is able to bind a variety of cations including Cd(2+), Cu(2+), Zn(2+) and Pb(2+), with different stoichiometries as shown by mass spectrometry. The protein displays a complete absence of periodic secondary structures as measured by far-UV circular dichroism, infrared spectroscopy and hydrogen/deuterium exchange kinetics. When attached onto a BIA-ATR biosensor, no significant structural change was observed upon removing the metal ions.     

Contrasting geographical distributions as a result of thermal tolerance and long-distance dispersal in two allegedly widespread tropical brown algae

Background

Many tropical marine macroalgae are reported from all three ocean basins, though these very wide distributions may simply be an artifact resulting from inadequate taxonomy that fails to take into account cryptic diversity. Alternatively, pantropical distributions challenge the belief of limited intrinsic dispersal capacity of marine seaweeds and the effectiveness of the north-south oriented continents as dispersal barriers. We aimed to re-assess the distribution of two allegedly circumtropical brown algae, Dictyota ciliolata and D. crenulata, and interpret the realized geographical range of the respective species in relation to their thermal tolerance and major tectonic and climatic events during the Cenozoic.

Methodology/Principal Findings

Species delimitation was based on 184 chloroplast encoded psbA sequences, using a Generalized Mixed Yule Coalescent method. Phylogenetic relationships were inferred by analyzing a six-gene dataset. Divergence times were estimated using relaxed molecular clock methods and published calibration data. Distribution ranges of the species were inferred from DNA-confirmed records, complemented with credible literature data and herbarium vouchers. Temperature tolerances of the species were determined by correlating distribution records with local SST values. We found considerable conflict between traditional and DNA-based species definitions. Dictyota crenulata consists of several pseudocryptic species, which have restricted distributions in the Atlantic Ocean and Pacific Central America. In contrast, the pantropical distribution of D. ciliolata is confirmed and linked to its significantly wider temperature tolerance.

Conclusions/Significance

Tectonically driven rearrangements of physical barriers left an unequivocal imprint on the current diversity patterns of marine macroalgae, as witnessed by the D. crenulata–complex. The nearly circumglobal tropical distribution of D. ciliolata, however, demonstrates that the north-south oriented continents do not present absolute dispersal barriers for species characterized by wide temperature tolerances.