title: RuBisCO in Non-Photosynthetic Alga Euglena longa: Divergent Features, Transcriptomic Analysis and Regulation of Complex Formation.
abstract: 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, but one of them 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. Altogether, our results revealed signatures of evolutionary degradation (becoming defunct) of RuBisCO in E. longa and suggest that its biological role in this species may be rather unorthodox, if any.
authors.affiliation: Life Science Research Centre, Department of Biology and Ecology and Institute of Environmental Technologies, Faculty of Science, University of Ostrava, 701 00 Ostrava, Czech Republic.
authors.forename: Kristína
authors.initials: K
authors.lastname: Záhonová
authors.affiliation: Institute of Parasitology, Biology Centre ASCR, 370 05 České Budějovice, Czech Republic.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Füssy
authors.affiliation: Institute of Parasitology, Biology Centre ASCR, 370 05 České Budějovice, Czech Republic.|University of South Bohemia, Faculty of Science, 370 05 České Budějovice, Czech Republic.|Institute of Microbiology ASCR, Centrum Agaltech, 379 01 Třeboň, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Oborník
authors.affiliation: Life Science Research Centre, Department of Biology and Ecology and Institute of Environmental Technologies, Faculty of Science, University of Ostrava, 701 00 Ostrava, Czech Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Eliáš
authors.affiliation: Life Science Research Centre, Department of Biology and Ecology and Institute of Environmental Technologies, Faculty of Science, University of Ostrava, 701 00 Ostrava, Czech Republic.|Institute of Parasitology, Biology Centre ASCR, 370 05 České Budějovice, Czech Republic.
authors.forename: Vyacheslav
authors.identifier: http://orcid.org/0000-0003-4765-3263
authors.initials: V
authors.lastname: Yurchenko
mesh_terms: D044802:Euglena longa / Q000201:enzymology / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000235:genetics; D012273:Ribulose-Bisphosphate Carboxylase / Q000096:biosynthesis / Q000235:genetics; D059467:Transcriptome / Q000502:physiology*
chemical_list: D015800:Protozoan Proteins; D012273:Ribulose-Bisphosphate Carboxylase