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44 • "PROTIST—2016
1 - Department of Environmental Life Sciences, Tohoku University, Japan
2 - Division of Environmental Photobiology, National Institute for Basic Biology, Japan
3 - Division of Morphogenesis, National Institute for Basic Biology, Japan
4 - Functional Genomics Facility, National Institute for Basic Biology, Japan [email protected]
Stable endosymbiotic relationship between cnida-rian animal and dinoflagellate Symbiodinium spp. is a prerequisite for sustaining coral reef ecosystem. Recent studies have shown that elevated seawater temperature can cause collapse of endosymbiosis by expulsion of the symbiotic algae from cnidarians, which is known as 'bleaching', and subsequent mass mortality. However, the technical difficulty in maintaining and using corals as material in laboratory has hampered further understanding of the molecular biology of the cnidarian-dinofla-gellate endosymbiosis. Here we show transcriptomic analyses using the symbiotic sea anemone Exaiptasia pallida (formerly Aiptasiaspp.), an emerging model cnidarian, in multiple culture conditions. The genome-wide gene expression profiles were analyzed by mapping the RNAseq reads from symbiotic and experimental apo-symbiotic anemones onto the host and endosymbiont genome sequences. A large portion of the genes differentially expressed in response to light and elevated temperature in the symbiotic and apo-symbiotic anemones was not overlapped and, in a number of cases, different members in a single gene family were activated between the symbiotic and apo-symbiotic anemones. These suggest that the anemones use distinct gene sets to respond to environmental changes depending on the symbiosis states with Symbiodinium. From the endosymbiont side, several photosynthesis-related genes associated with the photosystem II core assembly were detected to be down-regulated under the heat condition in hospite, which potentially affect the photodamage-induced stress responses. Overall, our data suggest that the endosymbiosis with Symbiodinium substantially affect the host's transcriptional profiles, potentially leading to the altered ecological contribution to the environment.
CHLOROPLAST DIVISION OF TETRASEL-MIS SP. IN THE FOOD VACUOLE OF MIXO-TROPHIC ALGAE RAPAZA VIRIDIS Maruyama M.1, Miyagishima S.2, Suzaki T.3, Kashiyama Y.14
1 - Fukui University of Technology
2 - National Institute of Genetics
3 - Kobe University
4 - Ritsumeikan University [email protected]
Rapaza viridis is a euglenoid that always possesses chloroplasts in cells without exception. R. viridis requires not only light but also a specific strain of green algae (Tetraselmis sp.) as its prey for their survival/growth, hence apparently being of obligate mixotrophy. Nonetheless, the degradative process of chloroplasts of the prey was barely observed. Furthermore, only trace amount of 132,173-cyclopheophorbide enols (CPEs), the non-phototoxic catabolites of chlorophylls, was produced along with the predation, indicating that only a small proportion of chlorophylls was actually discarded from the ingested chloroplasts. We thus investigated cell dynamics regarding ingested chloroplasts in R. viridis to understand the fate of the chloroplasts and chlorophylls contained therein. Unlike other phycophagic euglenoids, decrement of chlorophyll fluorescence from the ingested chloroplasts was rarely observed, and any evidence for digestive degradation of the chloroplasts was not recognized. Furthermore, the chloro-plastic eye-spots of Tetraselmis sp. became dispersed several hours after the ingestion and eventually disappeared. In the next hours, interestingly, the ingested chloroplasts became subdivided into more than several pieces with various sizes. Within a day, the unique, rough appearance of chloroplasts of Tetraselmis sp. in the DIC image became insignificant and changed into a rather smooth appearance that is no more distinguishable from those originally possessed by R. viridis. Afterward, the number of "chloroplasts" per cell began to decrease, suggesting progress of R. viridis cell divisions at this stage. We discuss the mechanism for the observed chloroplast division and the origin of "chloroplasts" of R. viridis.
HETEROGENEITY IN NUTRIENT UPTAKE BY INDIVIDUAL DINOFLAGELLATE CELLS REVEALED USING NanoSIMS Matantseva O.1, Vogts A.2, Voss M.2, Skarlato S.1
1 - Institute ofCytology RAS, St. Petersburg, Russia
2 - Institute for Baltic Sea Research Warnemuende, Germany
Dinoflagellates are one of the most successful groups of marine protists. Many photosynthetic dinoflagellates can utilize not only inorganic, but also organic compounds as nutrients, which is advantageous in eutrophied coastal zones. Therefore, nutritional physiology of these organisms receives much scientific attention. Usually it is studied by bulk approaches; however, the use of
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modern single-cell tools significantly advances our knowledge in this field. We used stable isotope tracers, isotope ratio mass spectrometry and nanoscale secondary ion mass spectrometry (NanoSIMS) to investigate concurrent uptake of nitrate and urea by dinoflagellates Prorocentrum minimum at the population and single-cell levels. Although bulk and averaged single-cell measurements revealed similar relationships between the urea and nitrate uptake, NanoSIMS disclosed significant heterogeneity in nutritional activity of individual cells. Dinoflagellates readily consumed urea even if this nutrient was new to the cells, but some cells took it up at a 9-folds higher rate than others. Furthermore, sudden urea input resulted in overall 30-40% suppression ofthe nitrate uptake. However, a closer look with NanoSIMS showed that in 30% of cells nitrate consumption was completely inhibited, whereas in other cells it might be not suppressed. We conclude that even sporadic inputs of urea to coastal ecosystems are likely to have a prominent effect on P. minimum populations. Physiological heterogeneity among individual dinoflagellate cells can represent a so far overlooked strategy towards ecological success. Funded by the Russian Science Foundation, project 16-14-10116 (to OM, SS) and Federal Ministry of Education and Research, grant BMBF 03F0626A (to AV, MV).
TRENDS IN ENDOSYMBIOTIC GENE TRANSFER ON PLASTID METABOLIC PATHWAYS IN DINOFLAGELLATES WITH NON-CANONICAL PLASTIDS Matsuo E.1, Inagaki Y.12
1 - Graduate School of Life and Environmental Sciences, University of Tsukuba
2 - Center for Computational Sciences, University of Tsukuba
The major photosynthetic dinoflagellates possess red algal-derived plastids, but some minor lineages established non-canonical plastids derived from phylogenetically diverse eukaryotic algae. Dinoflagellates Karlodinium veneficum and Lepidodinium chlorophorum, which bear non-canonical plastids derived from haptophyte- and green algal endosymbionts, respectively, and their nuclear genomes contain genes encoding plastidal proteins that are likely transferred from the genomes ofthe endosymbiont algae (endosymbiotic gene transfer, EGT). Although EGT is generally considered to be an essential step in transforming an endosymbiotic alga into a plastid, it has yet to be fully understood to what extent metabolic functions in the Karlodinium and Lepidodinium plastids rely
on endosymbiotically acquired proteins. We here surveyed nucleus-encoded plastidal proteins in Karlodinium and Lepidodinium, and investigated the origins of the proteins involved in two metabolic pathways localized in the plastid. Chlorophyll a biosynthetic pathway in the two species appeared to be reorganized in different ways. The pathway in Karlodinium was found to be occupied by proteins acquired from the haptophyte endosymbiont, while 'laterally derived' proteins, which were acquired from diverse eukaryotes rather than the green algal endosymbiont, comprise the pathway in Lepidodinium. In contrast, the majority of proteins which were detected in isoprene biosynthetic pathway in Karlodinium or Lepidodinium were derived from host dinoflagellate, suggesting that switch from the canonical to non-canonical plastids barely triggered reorganization of this particular pathway in the two species. In this talk, we discuss biological reasons for the marked difference in the impact of gene transfer between the two metabolic pathways in Karlodinium and Lepidodinium.
LAGENOPHRYS PATINA (CILIOPHORA: PERITRICHIA: LAGENOPHRYIDAE) ATTACHED TO TWO MEXICAN POPULATIONS OF HYALELLA AZTECA (CRUSTACEA: AM-PHIPODA): STATISTICAL APPROACH TO PROBE SITE PATTERN PREFERENCE ON HOST
Mayén-Estrada R.1, Macip-Ríos R.2, Hermoso-Salazar M.3, Romero-Niembro V.M.1
1 - Lab. Protozoología, Depto. Biol. Comparada, Fac. Ciencias, Universidad Nacional Autónoma de México, Circuito Ext. s/núm. Ciudad Universitaria, C. P. 04510, Ciudad de México, Mexico
2 - ENES Morelia, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro No.8701, Col. Ex Hacienda de San José de la Huerta, C.P. 58190 Morelia, Michoacán, Mexico
3 - Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Circuito Ext. s/núm. Ciudad Universitaria, C. P. 04510, Ciudad de México, Mexico [email protected]
Members of genus Lagenophrys are obligate symbiotic peritrichs of crustaceans, however the pattern of distribution on corporal surface varies according to involved species. To demonstrate with statistical tests the preference for an amphipod body region or appendage to attach, two Hyalella azteca populations were collected in two Mexican lakes, Xochimilco Lake and Cuitzeo Lake, and density and prevalence of Lagenophrys patina on host surface were calculated. We used a contingency table and
