| 1. |
- Hehenberger, Elisabeth, et al.
(author)
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Functional Relationship between a Dinoflagellate Host and Its Diatom Endosymbiont
- 2016
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In: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 33:9, s. 2376-2390
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Journal article (peer-reviewed)abstract
- While we know much about the evolutionary patterns of endosymbiotic organelle origins, we know less about how the actual process unfolded within each system. This is partly due to the massive changes endosymbiosis appears to trigger, and partly because most organelles evolved in the distant past. The dinotoms are dinoflagellates with diatom endosymbionts, and they represent a relatively recent but nevertheless obligate endosymbiotic association. We have carried out deep sequencing of both the host and endosymbiont transcriptomes from two dinotoms, Durinskia baltica and Glenodinium foliaceum, to examine how the nucleocytosolic compartments have functionally integrated. This analysis showed little or no functional reduction in either the endosymbiont or host, and no evidence for genetic integration. Rather, host and endosymbiont seem to be bound to each other via metabolites, such as photosynthate exported from the endosymbiont to the host as indicated by the presence of plastidic phosphate translocators in the host transcriptome. The host is able to synthesize starch, using plant-specific starch synthases, as a way to store imported photosynthate.
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| 2. |
- Irwin, Nicholas, et al.
(author)
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Phylogenomics supports the monophyly of the Cercozoa
- 2019
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In: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 130, s. 416-423
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Journal article (peer-reviewed)abstract
- The phylum Cercozoa consists of a diverse assemblage of amoeboid and flagellated protists that forms a major component of the supergroup, Rhizaria. However, despite its size and ubiquity, the phylogeny of the Cercozoa remains unclear as morphological variability between cercozoan species and ambiguity in molecular analyses, including phylogenomic approaches, have produced ambiguous results and raised doubts about the monophyly of the group. Here we sought to resolve these ambiguities using a 161-gene phylogenetic dataset with data from newly available genomes and deeply sequenced transcriptomes, including three new transcriptomes from Aurigamonas soils, Abollifer prolabens, and a novel species, Lapot gusevi n. gen. n. sp. Our phylogenomic analysis strongly supported a monophyletic Cercozoa, and approximately-unbiased tests rejected the paraphyletic topologies observed in previous studies. The transcriptome of L. gusevi represents the first transcriptomic data from the large and recently characterized Aquavolonidae-Treumulida-'Novel Clade 12' group, and phylogenomics supported its position as sister to the cercozoan subphylum, Endomyxa. These results provide insights into the phylogeny of the Cercozoa and the Rhizaria as a whole.
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| 3. |
- Strassert, Jürgen F. H., et al.
(author)
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Phylogeny, Evidence for a Cryptic Plastid, and Distribution of Chytriodinium Parasites (Dinophyceae) Infecting Copepods
- 2019
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In: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 66:4, s. 574-581
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Journal article (peer-reviewed)abstract
- Spores of the dinoflagellate Chytriodinium are known to infest copepod eggs causing their lethality. Despite the potential to control the population of such an ecologically important host, knowledge about Chytriodinium parasites is limited: we know little about phylogeny, parasitism, abundance, or geographical distribution. We carried out genome sequence surveys on four manually isolated sporocytes from the same sporangium, which seemed to be attached to a copepod nauplius, to analyze the phylogenetic position of Chytriodinium based on SSU and concatenated SSU/LSU rRNA gene sequences, and also characterize two genes related to the plastidial heme pathway, hemL and hemY. The results suggest the presence of a cryptic plastid in Chytriodinium and a photosynthetic ancestral state of the parasitic Chytriodinium/Dissodinium clade. Finally, by mapping Tara Oceans V9 SSU amplicon data to the recovered SSU rRNA gene sequences from the sporocytes, we show that globally, Chytriodinium parasites are most abundant within the pico/nano- and mesoplankton of the surface ocean and almost absent within microplankton, a distribution indicating that they generally exist either as free-living spores or host-associated sporangia.
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| 4. |
- Strassert, Jürgen F H, et al.
(author)
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Single cell genomics of uncultured marine alveolates shows paraphyly of basal dinoflagellates
- 2018
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In: The ISME Journal. - : Macmillan Publishers Ltd.. - 1751-7362 .- 1751-7370. ; 12, s. 304-308
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Journal article (peer-reviewed)abstract
- Marine alveolates (MALVs) are diverse and widespread early-branching dinoflagellates, but most knowledge of the group comes from a few cultured species that are generally not abundant in natural samples, or from diversity analyses of PCR-based environmental SSU rRNA gene sequences. To more broadly examine MALV genomes, we generated single cell genome sequences from seven individually isolated cells. Genes expected of heterotrophic eukaryotes were found, with interesting exceptions like presence of proteorhodopsin and vacuolar H+-pyrophosphatase. Phylogenetic analysis of concatenated SSU and LSU rRNA gene sequences provided strong support for the paraphyly of MALV lineages. Dinoflagellate viral nucleoproteins were found only in MALV groups that branched as sister to dinokaryotes. Our findings indicate that multiple independent origins of several characteristics early in dinoflagellate evolution, such as a parasitic life style, underlie the environmental diversity of MALVs, and suggest they have more varied trophic modes than previously thought.
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