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Protistology ■ 91
3 - University of South Bohemia, Faculty of Science, 370 05 Ceske Budejovice, Czech Republic
4 - Institute ofMicrobiologyASCR, Centrum Agaltech, 379 01 Trebon, Czech Republic kika.z.ahonova@gmail.com
Euglena longa, a close relative of the photosynthetic model alga Euglena gracilis, possesses an enigmatic non-photosynthetic plastid. Its genome has retained a gene for the large subunit of the enzyme RuBisCO (rbcL). Here we provide new data illuminating the putative role of RuBisCO in E. longa. We demonstrated that the E. longa RBCL protein sequence is extremely divergent compared to its homologs from the photosynthetic relatives, suggesting a possible functional shift upon the loss of photosynthesis. Similarly to E. gracilis, E. longa harbors a nuclear gene encoding the small subunit of RuBisCO (RBCS) as a precursor polyprotein comprising multiple RBCS repeats, one of which is highly divergent. Both RBCL and the RBCS proteins are synthesized in E. longa, but their abundance is very low compared to E. gracilis. No RBCS monomers could be detected in E. longa, suggesting that processing of the precursor polyprotein is inefficient in this species. The abundance of RBCS is regulated post-transcriptionally. Indeed, blocking the cytoplasmic translation by cycloheximide has no immediate effect on the RBCS stability in photosynthetically grown E. gracilis, but in E. longa, the protein is rapidly degraded. E. longa appears to lack the chaperone RBCX essential for assembly of a conventional RuBisCO complex. Altogether, our results revealed signatures of evolutionary degradation of RuBisCO in E. longa and suggest that its role in this species may be rather unorthodox.
PROTIST COMMUNITIES IN WATER AND SEDIMENT OF A SEA CUCUMBER FARMING SYSTEM Zhang Q., Tan S., Gong J.
Laboratory of Microbial Ecology and Matter Cycles, Yantai Institute of Coastal Zone Research, Chinese Academy ofScience, Yantai, China jgong@yic.ac.cn
Little is known about the distinctive communities of uncultured protsit within the aquaculture ecosystem. In this work, the planktonic and benthic protist communities in a sea cucumber farming system were simultaneously investigated on three sampling dates. Analyses of SSU rRNA gene libraries of six samples revealed 108 eukaryotic taxonomic units, among which 17.5% were rare. Stramenopiles and Alveolata are predominant groups in both sediment and water samples. Dinophyta, Rhizaria and parasitic Mesomycetozoa were only detected
in water samples. Parasitic Apicomplexa were found frequently from both water and sediment samples. Based on terminal-restriction fragment length polymorphisms, distinct succession and contrasting protist community structure was found among temporal samples and between planktonic and benthic habitats. Redundancy analysis indicated that the temprature, concentration of dissolved phosphate, and N:Si in surface water were the most significant abiotic variables shaping the planktonic communities. This study indicates that temprature and stoichiometric ratios play important roles in driving succession of protist communities, and parasitic protist could be early examed by molecular technologies for the farming pools. This work was supported by projects from NSFC (No. 313018680) and Scientific Development Program of Yantai (No. 2014ZH073).
MAKE PERCISE IDENTIFICAITON USING DNA TAXONOMY TECHNIQUES FOR CLOSELY RELATED EUPLOTES CONGENERS (PROTOZOA, CILIOPHORA) WITH HIGHLY PHENOTYPIC PLASTICITY Zhao Y.1, Yi Z.2, Song W.3
1 - Research Center forEco-Environmental Sciences, Chinese Academy ofSciences, Beijing100085, China
2 - Guangzhou Key Laboratory of Subtropical Biodiversity andBiomonitor, SchoolofLife Science, South China Normal University, Guangzhou 510631, China
3 - Laboratory of Protozoology, Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China yanzhao@rcees.ac.cn
Ciliated protists constitute astounding diversity and play crucial role in different biotopes yet still incompletely characterized microbes. DNA barcoding is promising to address this dilemma. This molecular technique based on COX 1 gene has become a routine method for animal organism identification and taxonomic clarification. This common region also can distinguish ciliates species, but has not displayed universality, and establishing a standardized DNA barcoding system for ciliated protists is still confronted with many difficulties and challenges. Here, we collected the species-rich taxon Euplotes from brackish and fresh waters. In the framework of traditional classification system, the Euplotes spp. with available morphological features can provide a useful template against which to test the accuracy of DNA-based taxonomy. Using >30 samples, we have assessed the most common COX 1 region and the alternative SSU-V4, SSU-V9, LSU-D1/D2, ITS1, ITS2 markers. And SSU-V9, LSU-D1/D2 and ITS1 could distinguish the most
92 • "PROTIST—2016
closely related species and are proper markers for ciliates barcoding.
THE INTRICATE EVOLUTIONARY HISTORY
OF RhoBTB PROTEINS
Zihala D.1, Klimes V.1, Rivero F.2, Elias M.1
1 - University ofOstrava, Faculty ofScience, Department of Biology and Ecology, Chittussiho 10, 710 00 Ostrava, Czech Republic
2 - Centre forCardiovascular and Metabolic Research, The Hull York Medical School and Department of Biological Sciences, University of Hull, Cottingham Road, Hull HU6 7RX, UK z.ihaladavid@gmail.com
The Rho family is one of the major subgroups of the huge superfamily of Ras-like GTPases. Rho proteins are known primarily as regulators ofvarious pathways that are connected to the actin cytoskele-ton (cell movement, polarization, morphogenesis etc.). These proteins usually contain only the Rho-type GTPase domain, but some of them possess also a tandem of two so-called BTB domains and are called RhoBTB proteins. The BTB domain is a protein-protein interaction domain and is often a part of proteins that are connected to protein ubiquitination through Cullin3-dependend E3 ligases. Proteins with the domain architecture characteristic for RhoBTB proteins have been reported only from metazoans and dictiosteliid slime moulds, but this distribution was deduced from a phylognetically very limited survey. We have utilized the currently available wealth of genomic and transcritpomic data from diverse eukaryotes, including a wide coverage of protist taxa, and found out that RhoBTB proteins occur in many additional eukaryotic lineages. Although scattered, the phyletic pattern of RhoBTB genes is compatible with a hypothesis that a primordial RhoBTB gene was present already in the last eukaryotic common ancestor. Interestingly, RhoBTB proteins from some taxa (Amoebozoa, Apusomonadida, and Cryptomonadida) proved to possess a RING/U-box domain inserted into the first BTB domain. RING and U-box are related domains that constitute a class of E3 enzymes, so our findings further support the idea that RhoBTB3 proteins ancestrally served as components of ubiquitin-mediated regulation. These and other findings of our evolutionary analyses of RhoBTB proteins will be presented and discussed.
THE STATE OF ART IN THE TAXONOMY OF
"HELIOZOA"
Zlatogursky V.V.
Department of Invertebrate Zoology, Faculty of
Biology, Saint-Petersburg State University v.zlatogursky@gmail.com
"Heliozoa" is a former taxon of spherical axopodial protists. These organisms, being outwardly similar have revealed to be not necessarily related. Some of lineages are now placed into the proper "supergroups", while many deviant forms still remain "orphans". The most diverse group — the centrohelids — recently was placed in Haptista along with haptophytes and their internal taxonomy also was considerably revised showing interesting examples of parallel evolution. But in comparison to other groups with a developed taxonomy "Heliozoa" still seem to be undeservingly neglected. Many taxa of flagellates, ciliates and in a less degree of amoebae get much more attention, while heliozoan taxonomy suffer from the lack of skilled taxonomists. The great amount of their diversity is likely to be unknown. The heliozoans require closer attention, being ubiquitous in freshwater, marine (both planktonic and benthic) and soil environments, important consumers of bacteria, protists and even micrometazoans. But the taxonomic impediment currently prevents them from being incorporated into ecological and biogeographic studies. Many heliozoans, especially centrohelids, are easy to maintain in the culture, have a rich morphology and potentially can serve a good model for addressing many of fundamental questions of protistology, including a species problem, the endemism vs ubiquity dilemma and the evolution of cell coverings. Many of them can be indicators ofwater quality and should be included to biodiversity indexes. But first of all, their taxonomy need to be evaluated and the main proportion of species should be described on the modern level. Study support: RFBR grants 15-04-18101_a, 15-29-02749-ofi_m.
THE RELIABILITY OF PROTOZOANS AS INDICATORS OF AQUATIC ECOSYSTEM HEALTH Zolotarev V.A.
I.D. Papanin Institute for biology of inland waters Russian Academy of Sciences (IBIW RAS) forest753@gmail.com
Metapopulations of microbial organisms occur worldwide wherever their required habitats are realised. This is a consequence of ubiquitous dispersal driven by huge population sizes, and the consequently low probability of local extinction (Finlay, 2002). Microorganisms should be used in biomonitoring for several compelling reasons. (1) A cosmopolitan distribution facilitates comparisons of test results in geographically different regions. (2) Problems of scale are diminished. (3) Replicability
