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Protistology ■ 27
TWO NEW SPECIES OF THE DINOFLAGEL-LATE GENUS PHALACROMA STEIN (DINO-PHYTA) FROM THE TROPICAL MEXICAN PACIFIC
Hemández-Becerril David12, Esqueda-Lara Karina3
1 - Instituto de Ciencias del Mar y Limnología
2 - Universidad Nacional Autónoma de México
3 - Centro del Cambio Global y la Sustentabilidad del Sureste (CCGSS) [email protected]
Species of the thecate dinoflagellate genus Phala-croma Stein are common in the marine phytoplank-ton all over the world, but especially diverse in tropical areas. Some species are considered to produce Okadaic Acid or Dinophysistoxin, which cause diarrhetic shellfish poisoning (DSP). The genus Phalacroma includes mixotrophic and heterotrophic species with an elevated epitheca, visible in lateral view and narrow horizontally projected cingular lists. During surveys of phytoplankton from the tropical Mexican Pacific, two undescribed species of Phalacroma were found, and in this paper they are depicted following detailed observations by LM and SEM. Phalacroma ornamentatum sp. nov. is a new species, superficially similar to species of the Phalacroma rotundatum (Claparede et Lachmann) Kofoid et Michener group, but its main distinctive characteristics are: (1) thick theca, (2) ornamentation of the theca and sulcal lists, and (3) relatively narrow sulcal lists and junction close to the cingulum. The other new species is Phalacroma palmatum sp. nov., which is relatively similar to Phalacroma bipartitum Kofoid et Skogsberg, but is characterized by (1) shape and extension of the left sulcal list to the posterior part of cell, (2) absence of R2 in the left sulcal list, (3) sulcal lists joined at the cingulum level, and (4) ornamentation of the theca and both sulcal lists. Phalacroma ornamentatum was fairly common in the Gulf of California, whereas Phalacroma palmatum was very rare.
ORGANELLE DNA REPLICATION IN CHLOR-
ARACHNIOPHYTE ALGAE
Hirakawa Y.1, Watanabe A.2, Suzuki S.2, Ishida K.1
1 - Faculty of Life and Environmental Sciences, University of Tsukuba
2 - Graduate School of Life and Environmental Sciences, University of Tsukuba [email protected]
Plastids evolved by multiple endosymbiotic events where photosynthetic organisms became fully integrated with host eukaryotic cells. Chlorara-chniophyte algae possess complex plastids acquired by the uptake of a green alga, and the plastids harbor
a relict nucleus of the endosymbiont, the so-called nucleomorph. Therefore, chlorarachniophyte cells possess three different endosymbiotically-derived genomes in the plastid, mitochondrion, and nucleomorph. These organelle genomes do not encode essential DNA replication components (i.e., DNA polymerases), and it remains unclear whether nucleus-encoded counterparts are imported into respective organelles. To gain insight into the evolution of complex plastids, we investigated nucleus-encoded DNA polymerases related to the chlorarachniophyte organelles. We found that chlorarachniophytes evolved two phyloge-netically distinct DNA polymerases for the plastid and mitochondrion, although a single DNA poly-merase is dually targeted to both organelles in Archaeplastida. Our phylogenetic analyses suggest that the mitochondrion-targeted one is originated by the host, and the plastid-targeted one seems to be derived from a red algal lineage via lateral gene transfer. We also discovered a nucleomorph-tar-geted DNA polymerase that was phylogenetically related to viral sequences. Our data imply that organelle DNA polymerases of chlorarachniophytes have been replaced by a counterpart of other organisms during the evolution.
PRIMARY AND SECONDARY ENDOSYM-BIOTIC GENE TRANSFER OF BACTERIAL RECA IN EUKARYOTES Hofstatter P.G.1, Lahr D.J.G.1, Brown M.2
1 - University of Sao Paulo
2 - Mississippi State University [email protected]
Recombinases promote DNA repair by homologous recombination and these genes occur in all known domains of life: virus and bacteria (RecA), Archaea (RADA, RADB) and Eukaryotes (RAD51X, DMC1). The bacterial recombinases (RecA) are present not only among bacteria, but also in several eukaryotes: Chlorophyta, Rhodophyta, Amoebozoa, Peronosporomycetes (Oomycetes), Bacillariophyta and other SAR group lineages. The eukaryotic recA genes have two different origins, a mitochondrial and a chloroplastic. The acquisition of recA genes by eukaryotes was possible by means of endosym-biotic gene transfer (EGT) in the form of primary endosymbiosis (bacteria-eukaryote) and secondary endosymbiotic gene transfers (eukaryote-euka-ryote). The RecA proteins present a transit pep-tide and are imported by the organelles, where they act in homologous recombination. Several major eukaryotic lines lost the bacterial recombinases, as seen in Opisthokonta, where the bacterial ho-
28 • "PROTIST—2016
mologues were probably replaced by eukaryotic specific homologue or in the secondarily amito-chondriate groups where it is not necessary anymore. In the other hand, recA genes were subject to further duplication events in green plants, where they present several forms. The reconstruction of the RecA phylogeny with its EGT events retells the very evolutionary history of the euka-ryotes and also bacteria and enables a further understanding of endosymbiosis. We showed a group-wide presence of mitochondrial recA genes in Amoebozoa, Oomycetes, green plants and minor groups giving support to an ancestral EGT acquisition ofmitochondrial recA prior to eukaryotic diversification, as well as chloroplastic recA in all major photosynthesizing groups.
UNVEILING SSU RDNA INTRAGENOMIC POLYMORPHISM IN DEEP-SEA FORAMI-NIFERA USING SINGLE-CELL HIGH THROUGHPUT SEQUENCING Holzmann Maria1, Apothelot-Perret-Gentil Laure1, Voltsky Ivan12, Lejzerowicz Franck1
1 - University of Geneva
2 - Ben Gurion University of the Negev [email protected]
The SSU rRNA genes are commonly used for the assessment of protist diversity. It is assumed that the rDNA copies are identical within the individual cells. However, previous studies, using cloning and Sanger sequencing approach showed a high level of intra-individual polymorphism in shallow water benthic foraminifera. Here, we present the results of single cell high-throughput analysis of SSU rDNA in about 200 specimens of abyssal foraminifera. Our data confirm the presence of intragenomic polymorphism in foraminifera but levels of intra-individual divergence are different among taxono-mic groups. Our approach further allows us a quick sorting of foraminifera for barcoding purposes by distinguishing unknown foraminiferal sequences from those that are already present in our database. In the case of unknown sequences the longer SSU fragment is Sanger sequenced afterwards to phylogenetically characterize the putative new species.
ANCIENT MITOCHONDRIAL PROTEIN SECRETION
Horvathova L.1, Zarsky V.1, Derrelle R.2, Krupickova A.1, Klapst'ova V.1, Voleman L.1, Petru M.1, Elias M.3, Panek T.3, Cepicka I.4, Huysmans G.5, Chami M.6, Francetic O.7, Dolezal P.1 1 - Dept. of Parasitology, Charles University in Prague
2 - Dept. de Biologie, Université Paris-Sud 11
3 - Dept. ofBiology and Ecology, University ofOstrava
4 - Dept. of Zoology, Charles University in Prague
5 - Weill Cornell Medical College, Cornell University
6 - Biozentrum der Universität Basel
7 - Institut Pasteur [email protected].
The bacterial origin of mitochondria has been evidenced by a number of shared features with current bacteria, including some of the protein transport components. However, most of the original bacterial protein transport pathways have been lost from the mitochondria and replaced by the protein import apparatus. To some detail, mitochondria of Discoba represent an evolutionary intermediate stage as they carry the largest mitochondrial genomes encoding bacterial SecY and TAT trans-locases. By a multi-phylome approach we have analyzed eukaryotic proteomes for nuclear encoded genes, which are exclusive to Discoba. We show that their nuclei encode for about forty genes not found in other eukaryotic lineages. These include eight components of bacterial type II secretion system (T2SS). We show that mitochondria of Discoba express minimalist T2SS, which includes the pore forming secretin in the outer mitochondrial membrane and pseudopilin in the intermembrane space. Using the bacterial and yeast two hybrid assays, we are currently looking for the putative substrate of the ancient mitochondrial protein secretion pathway.
OCHER-COLORED GRANULES IN THE CILIATE CYCLOTRICHIUM SP. ARE EVIDENTLY DIATOM CHLOROPLASTS Hoshina Ryo1, Suzaki Toshinobu2, Kusuoka Yasushi3
1 - Nagahama Institute of Bioscience and Technology
2 - Kobe University
3 - Lake Biwa Museum [email protected]
As a crucial part of our exploration ofthe diversity of animal protists associated with algal endosymbionts, we have examined the ultrastructure and molecular characteristics of a ciliate ofthe genus Cyclotrichium collected from Lake Biwa, the largest and oldest lake in Japan. The ciliates, which are nearly spherical and about 100 ^m in diameter, are filled with hundreds of 2—3 ^m ocher-colored granules that impart their color to the whole cell. The internal structure of these granules is indistinct by light microscopy, but examination by SEM shows them to be chloroplasts consisting ofthree-layered thylakoid membranes. Many of the chloroplasts seem to be at different phases of digestion in food vacuoles (from
