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86 • "PROTIST—2016
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 [email protected]
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 [email protected]
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
