Telonemia-specific environmental 18S rDNA PCR reveals unknown diversity and multiple marine-freshwater colonizations

<p>Abstract</p> <p>Background</p> <p>Recent surveys of eukaryote 18S rDNA diversity in marine habitats have uncovered worldwide distribution of the heterotrophic eukaryote phylum Telonemia. Here we investigate the diversity and geographic distribution of Telonemia sequences by in-depth sequencing of several new 18S rDNA clone libraries from both marine and freshwater sites by using a Telonemia-specific PCR strategy.</p> <p>Results</p> <p>In contrast to earlier studies that have employed eukaryote-wide PCR design, we identified a large and unknown diversity of phylotypes and the first rigorous evidence for several freshwater species, altogether comprising 91 unique sequences. Phylogenies of these and publicly available sequences showed 20 statistically supported sub-clades as well as several solitary phylotypes with no clear phylogenetic affiliation. Most of these sub-clades were composed of phylotypes from different geographic regions.</p> <p>Conclusions</p> <p>By using specific PCR primers we reveal a much larger diversity of Telonemia from environmental samples than previously uncovered by eukaryote-wide primers. The new data substantially diminish the geographic structuring of clades identified in earlier studies. Nevertheless, since these clades comprise several distinct phylotypes we cannot exclude endemicity at species level. We identified two freshwater clades and a few solitary phylotypes, implying that Telonemia have colonized freshwater habitats and adapted to the different environmental and ecological conditions at independent occasions.</p

A phylogenetic mosaic plastid proteome and unusual plastid-targeting signals in the green-colored dinoflagellate Lepidodinium chlorophorum

Background Plastid replacements through secondary endosymbioses include massive transfer of genes from the endosymbiont to the host nucleus and require a new targeting system to enable transport of the plastid-targeted proteins across 3-4 plastid membranes. The dinoflagellates are the only eukaryotic lineage that has been shown to have undergone several plastid replacement events, and this group is thus highly relevant for studying the processes involved in plastid evolution. In this study, we analyzed the phylogenetic origin and N-terminal extensions of plastid-targeted proteins from Lepidodinium chlorophorum, a member of the only dinoflagellate genus that harbors a green secondary plastid rather than the red algal-derived, peridinin-containing plastid usually found in photosynthetic dinoflagellates. Results We sequenced 4,746 randomly picked clones from a L. chlorophorum cDNA library. 22 of the assembled genes were identified as genes encoding proteins functioning in plastids. Some of these were of green algal origin. This confirms that genes have been transferred from the plastid to the host nucleus of L. chlorophorum and indicates that the plastid is fully integrated as an organelle in the host. Other nuclear-encoded plastid-targeted protein genes, however, are clearly not of green algal origin, but have been derived from a number of different algal groups, including dinoflagellates, streptophytes, heterokonts, and red algae. The characteristics of N-terminal plastid-targeting peptides of all of these genes are substantially different from those found in peridinin-containing dinoflagellates and green algae. Conclusions L. chlorophorum expresses plastid-targeted proteins with a range of different origins, which probably arose through endosymbiotic gene transfer (EGT) and horizontal gene transfer (HGT). The N-terminal extension of the genes is different from the extensions found in green alga and other dinoflagellates (peridinin- and haptophyte plastids). These modifications have likely enabled the mosaic proteome of L. chlorophorum

Large-Scale Phylogenomic Analyses Reveal That Two Enigmatic Protist Lineages, Telonemia and Centroheliozoa, Are Related to Photosynthetic Chromalveolates

Understanding the early evolution and diversification of eukaryotes relies on a fully resolved phylogenetic tree. In recent years, most eukaryotic diversity has been assigned to six putative supergroups, but the evolutionary origin of a few major “orphan” lineages remains elusive. Two ecologically important orphan groups are the heterotrophic Telonemia and Centroheliozoa. Telonemids have been proposed to be related to the photosynthetic cryptomonads or stramenopiles and centrohelids to haptophytes, but molecular phylogenies have failed to provide strong support for any phylogenetic hypothesis. Here, we investigate the origins of Telonema subtilis (a telonemid) and Raphidiophrys contractilis (a centrohelid) by large-scale 454 pyrosequencing of cDNA libraries and including new genomic data from two cryptomonads (Guillardia theta and Plagioselmis nannoplanctica) and a haptophyte (Imantonia rotunda). We demonstrate that 454 sequencing of cDNA libraries is a powerful and fast method of sampling a high proportion of protist genes, which can yield ample information for phylogenomic studies. Our phylogenetic analyses of 127 genes from 72 species indicate that telonemids and centrohelids are members of an emerging major group of eukaryotes also comprising cryptomonads and haptophytes. Furthermore, this group is possibly closely related to the SAR clade comprising stramenopiles (heterokonts), alveolates, and Rhizaria. Our results link two additional heterotrophic lineages to the predominantly photosynthetic chromalveolate supergroup, providing a new framework for interpreting the evolution of eukaryotic cell structures and the diversification of plastids

Coccolithus huxleyi (Lohmann) Kamptner : Morfologiske undersøkelser i lys og elektronmikroskop

Coccolithus huxleyi er en av de vanligste coccolithoforider, den har en svært vid utbredelse. På norskekysten trekker den til seg oppmerksomheten ved lokale masseoppblomstringer med misfarging av sjøen til følge. I den senere tid har undersøkelser av nærstående arter avslørt ting av stor interesse for cellebiologer, systematikere og økologer. Ved Institutt for Marin Biologi, avdeling B, Universitetet i Oslo, er et betydelig arbeid lagt ned ved undersøkelser over fysiologiske forhold hos Coccolithus huxleyi. Det synes naturlig at arten kunne gi grunnlag for et hovedfagsarbeide

Hydrurus foetidus (Chrysophyceae): an update and request for observations

Hydrurus foetidus is a cold-water golden alga (Chrysophyceae) found in fast-flowing rivers mainly during time of snowmelt. It has primarily been studied by scientists located near alpine or northern locations, but there are also observations both in south and north America, Russia, Japan, in the Hope Bay area (Antarctica) and Himalaya. If and where environmental conditions are appropriate, Hydrurus may be distributed “worldwide.” More information is wanted from areas where its presence may be expected

Monetary policy and asset prices : interest rate rules and asset prices in Norway

This thesis will investigate the role of asset prices, in particular stock prices, on monetary policy in Norway. There has been a long established consensus in the literature that asset prices should not be targeted explicitly, mainly due to the uncertainty surrounding the identification of asset price misalignments and the uncertain effects interventions may have on asset markets. However, recent contributions in the literature have argued that asset prices might have a more prominent role due to, among others, their forward-looking nature. This thesis will survey some of these contributions and perform an empirical investigation on interest rate rules and asset prices using Norwegian data. Asset prices could be included in empirically estimated interest rate rules (reaction functions) provided that the simultaneity issue between asset prices and interest rates, and the measurement problem are appropriately addressed. Using Norwegian data I find that asset prices enter significantly in a simultaneous model estimated using two stage least squares (2SLS). I also find that asset prices contain more precise information on future inflation than the output gap and the growth gap, particularly in conjunction with the unemployment gap. This implies that asset prices can be viewed as an alternative real-time variable to the output gap or alike

Structure of extracellular polysaccarides produced by a soil Cryptomonas Sp. (Cryptophyceae)

The Hindak strain of a Cryptomonas species (Cryptophyceae) produces extracellular polysaccharides. Because there is no information on the structure of these compounds in the Cryptophyceae we conducted structural studies. Gas–liquid chromatographic analyses showed that the polysaccharide is composed of fucose, rhamnose, xylose, mannose, glucose, galactose, galacturonic acid, glucuronic acid, and traces of 3-O-methyl galactose. The polysaccharide was separated into two subtractions by ion-exchange chromatography. Fraction A consisted mainly of 1,3-linked galactose units and 1,4-linked galacturonic acid. Unlike fraction B, fraction A did not have xylose, 3-O-methyl galactose, or glucuronic acid. Also, its degree of branching was low compared to that of fraction B. Only traces of sulfate were present infraction A, but fraction B was 10–15% sulfated. Protein was approximately 1% in both fractions. These polysaccharides appear to be a novel type of polymer in algae