CC BY
25
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
