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between the river mouths and coastal areas. It is suggested that habitat segregation occurred among these species and was caused by the environmental factors and the differences ofutilization ofterrestrial or marine organic matter.
ANALYSES OF PHOTOSYNTHETIC OXIDATIVE STRESS RESPONSES IN HERBIVOROUS UNICELLULAR ORGANISMS Uzuka Akihiro12, Hirooka Shunsuke2, Fujiwara Takayuki12, Kanesaki Yu3, Yoshikawa Hirofumi3, Miyagishima Shin-ya12
1 - The Graduate University For Advanced Studies [SOKENDAI]
2 - National Institute of Genetics
3 - Tokyo University of Agriculture, Japan auzuka@nig.ac.jp
Photosynthesis generates reactive oxygen species (ROS) which destroy biomolecules. It is known that photosynthetic organisms, such as plants and algae, have strategies to cope with the photosynthetic oxidative stress to perform photosynthesis safely. When unicellular predators, such as amoebae, feed on photosynthetic organisms under illumination, they are probably exposed to ROS that are generated by engulfed prey during digestion. The aim of my study is to examine whether the algal predators are really exposed to oxidative stress, and if so, to understand how they cope with the photosynthetic oxidative stress. To this end, I have isolated amoebae that feed on both photosynthetic and non-photosynthetic bacteria from marsh. From them, I chose three amoebae which were evolutionally distantly related. These amoebae were co-cultured with the cyanobacteria or E. coli under dark or light condition and I measured ROS generated by engulfed photosynthetic prey and examined transcriptome changes of amoeba cell. The results show that singlet oxygen, which is believed to be the main ROS produced by photosynthesis, is generated in amoeba by engulfed photosynthetic prey under illumination but not in dark condition or during predation of non-photosynthetic prey. On the other hand, higher level ofhydrogen peroxide is produced under illumination than under dark condition regardless ofthe photosynthetic ability ofprey. Even if they are evolutionally distantly related species, three species of amoebae exhibited similar pattern of transcriptome changes. Now, I am conducting some assays to investigate whether phenomena which are predicted based on transcriptome changes are really occur.
IRON SULFUR CLUSTER ASSEMBLY IN AMITOCHONDRIATE OXYMONAD MONOCERCOMONOIDES
Vacek Vojtech1, Karnkowska Anna2, Cepicka Ivan3, Novak Lukas1, Treitli Sebastian1, Zubacova Zuzana1, Hampl Vladimir1
1 - Department of Parasitology, Charles University in Prague, Faculty ofScience, Czech Republic
2 - Department of Botany, University of British Columbia, Vancouver, V6T 1Z4, Canada
3 - Department of Zoology, Charles University in Prague, Faculty of Science, Czech Republic vacek3@natur.cuni.cz
Oxymonads are a group of anaerobic or micro-aerophilic protists living in guts of insects and vertebrates. They are the only group of eukaryotes without mitochondrion, however in their closest free-living relative Paratrimastix pyriformis have been found organelles which are morphologically ntsimilar to hydrogenosomes. Concomitantly with the absence of mitochondrion, Monocercomonoides lacks classical mitochondrial ISC system for synthesis of Fe-S clusters. Instead, subunits of SUF system were found in genome and transcriptome of Monocercomonoides: SufB, SufC, SufS and SufU. All these proteins contain well conserved catalytic sites which are needed for their function in FeS cluster assembly. Heterologous localization of SufB and SufC in Trichomonas vaginalis expression system showed cytosolic localization. We have also found subunits of SUF system in transcriptomic data from Paratrimastix pyriformis and two other members of Preaxostyla — oxymonad strain NAU3 distantly related to Monocercomonoides and isolate MORAITICA, the deepest branching lineage of Preaxostyla available at the moment. Phylogenetic analyses of SUF subunits showed that all preaxostyla SUFs forms single clade, which is clearly distinct from clades of other eukaryotes — proving that common ancestor of all known Preaxostyla acquired SUF system by horizontal gene transfer independently from other eukaryotes. To prove that SUF subunits are indeed functionally active in Monocercomonoides we have performed several complementation experiments in E. coli. Preliminary experiments with complementation proved that SufB of Monocercomonoides can substitute SufB of E. coli in synthesis of Fe-S cluster and therefore SUF system is functionally active in Fe-S cluster assembly. Heterologous localization of SufB and SufC in Trichomonas vaginalis expression system showed cytosolic localization. Our results indicate that Monocercomonoides is the first known
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organism, which assemble Fe-S clusters in the cytosol by concerted action of SUF and CIA pathways.
SYNCHRONIZED AND ER-DEPENDENT DYNAMICS OF MITOSOMES Voleman L.1, Najdrova V.1, Astvaldsson A.2, Tumova P.3, Einarsson E.2, Svindrych Z.4, Hagen G.M.4, Tachezy J.1, Svard S.G.2, Dolezal P.1
1 - BIOCEV— Biotechnology andBiomedicine Center of the Academy of Sciences and Charles University in Vestec and Department of Parasitology, Faculty of Science, Charles University in Prague, Czech Republic
2 - Department ofCell and Molecular Biology, BMC, Uppsala University, Uppsala, Sweden
3 - Department of Tropical Medicine, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
4 - Institute of Cellular Biology and Pathology, First Faculty of Medicine, Charles University in Prague, Czech Republic lubos.voleman@gmail.com
Mitosomes are the smallest evolutionary forms of mitochondria that evolved in eukaryotes adapted to anaerobic environments. While abandoning many attributes of the aerobic mitochondria such as the genome, respiration and the cristae, mitosomes have retained the double membrane and the bare bones of the pathways for the protein import and the synthesis ofthe iron-sulfur clusters. Here, we studied the dynamics of the mitosomes in the parasitic protist Giardia intestinalis, which belongs to one of five supergroups of eukaryotes known as Excavata. We found that mitosomes are extremely steady organelles during the interphase undergoing neither the fission nor the fusion during the interphase, thus being highly prone to become heterogeneous. Surprisingly, the mitosomal division is restricted to mitosis, when both central and peripheral organelles divide in a synchronized manner. The mitosomes also divide during the encystation of the parasite, thus preconfigure the cyst for the rapid excystation in a new host. Interestingly, the division involves the association of the mitosomes with the endoplasmic reticulum, a relationship typical for the mitochondria of Opisthokonta. While several such tethering mechanisms, which enable lipid transfer between the organelles, have been described for Opisthokonta, none of these have been shown to function in other eukaryotic supergroups including Excavata. However, we were able to show that lipid enzyme long chain acyl-CoA synthetase 4 is distributed to the mitosome-ER interface.
MORPHOLOGICAL AND MOLECULAR INVESTIGATION OF MARINE PARAMOEBI-DAE (AMOEBOZOA, DACTYLOPODIDA) Volkova E.N., Kudryavtsev A.A. Saint Petersburg State University, Russia radistkacat80@mail.ru
We present a revision of marine dactylopodid amoebae containing an intracellular eukaryotic symbiont traditionally called 'parasome', and currently known as 'Perkinsela-like organism' (PLO) related to Kinetoplastida. This group traditionally consists of two genera: Paramoeba Schaudinn, 1896 and Neoparamoeba Page, 1987 which differ in their cell coat structure; the former being covered with scales, while the latter, with the thin, scaleless glycocalyx. The third PLO-containing genus, Janickina Chatton, 1953 has no clear taxonomic affinities yet, as no molecular data are available for its members. We present the results of investigation of the biodiversity and phylogenetic relationships within the genera Paramoeba and Neoparamoeba based on 15 marine and brackish water strains isolated from a broad range ofhabitats. The conclusions are based on morphological, ultrastructural and molecular evidence. The data obtained allow us to conclude that (1) Morpho-species of Paramoeba and Neoparamoeba show considerable levels of intragenomic and intraspecies variability based on the SSU rDNA and ITS region sequences; (2) A detailed study combining analysis of light-microscopic data, ultrastructure and molecular evidence is necessary in most of cases to discriminate species within this group; (3) The cell coats of Paramoeba/Neoparamoeba clade have evolved from the scale-bearing ancestral taxa through several independent scale losses in various lineages of this clade. We also present novel data that contribute to further understanding of the co-evolution of amoebae and their intracellular symbionts.
Partially supported by the RFBR grant 15-29-02749; the study utilized the equipment of the core facility centers of St. Petersburg State University.
CILIATES AS BIOINDICATORS OF MARINE WATER QUALITY Warren A.1, Xu H.2
1 - Department of Life Sciences, Natural History Museum, London, UK
2 - Laboratory ofMicrobialEcology, Ocean University of China, Qingdao, China a.warren@nhm.ac.uk
Although protists, and especially ciliates, have long
