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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-
