Paramecium (ciliates, Protista) is a unicellular eukaryotic organism characterized by the presence of two nuclei: polyploid macronucleus, which is responsible for vegetative functions, and diploid micronuclei (gametic nuclei), which are responsible for the transfer of genetic information to the next generation.
Micronuclei participate in meiosis and mitosis and are involved in sexual processes such as autogamy and conjugation. Autogamy is a self-fertilization process which occurs in a single cell in the absence of a partner for conjugation. Conjugation involves two cells of opposite, complementary mating type at the right clonal age. The discovery of Paramecium mating types led to this organism being assigned as a model organism in genetics research.
Paramecium, like some other ciliates (e.g. Tetrahymena or Vorticella), has a complex structure of species. Taxonomic species are differentiated into cryptic species; examples include the 15 species of the P. aurelia complex. Problems of speciation are studied by our group using conventional methods (genetic crosses) and molecular methods (comparative analysis of genome fragments). Faunistic studies have revealed a wider range of prevalence than was previously assumed for a number of species in the P. aurelia complex.
Thanks to research on Paramecium, we can better understand the mechanisms of genome evolution and non-Mendelian inheritance, which is based on epigenetic processes affecting the gene expression and phenotype of the cell. With international cooperation, we are currently conducting research on the mating type determination in species belonging to the P. aurelia complex (Singh et al. 2014). Each of these species is characterized by two complementary mating types which are necessary in conjugation. In the P. aurelia complex, only one species is characterized by the Mendelian mode of mating type inheritance. In the remaining species, mating types are inherited either maternally or randomly. Both of those modes of mating type inheritance are epigenetic processes based on RNA interference. The genotypes of cells of opposite mating types are identical. The maternal determination of mating types occurs during macronuclear genome rearrangement when genetic material from a diploid germline undergoes polyploidization followed by elimination and telomerization. As a result of these changes, new functional macronuclear genes are formed which determine cell phenotype and mating type.
A collection of live strains from all continents (except Antarctica) represents the individual species of the P. aurelia complex, as well as other species from the Paramecium genus. This collection is a kind of gene bank for many genetics, systematics, population biology, and biogeography studies conducted independently within the institute and in the framework of international programs.
National Center for Science (OPUS) number 2012/05 / B / NZ8 / 00387 "Paramecium jenningsi - structure of species and syngen characteristics based on genetic crosses, cytological studies and analysis of chosen genome fragments" 2013-2015 Head: prof. dr. E. Przyboś, contractors from ISEA: dr S. Tarcz, N. Sawka, M. Surmacz.
National Science Centre (PRELUDIUM) number 2013/09 / N / NZ8 / 03198 Fri. "Identification of genes Mendelian and epigenetic mating type inheritance in selected species of Paramecium aurelia" 2014-2016 Head: N. Sawka.
National Science Centre (OPUS) number 2014/15 / B / NZ8 / 00258 "Biogeography and microevolution of microbial eukaryotes in the light of genetic variation assessment of natural population of ciliates belonging to Paramecium aurelia species complex" 2015-2017 Head dr hab. S. Tarcz contractors from ISEA: prof. dr. E. Przyboś, Dr. N. Sawka, M. Surmacz.
Scientific network European Research Group GDRE (fr. Groupement Europeen de Recherches) "Paramecium Genome Dynamics and Evolution" (Head Dr. L. Sperling, contractors from ISEA: E. Przyboś, M. Prajer, S. Tarcz, N. Sawka-Gądek).
COST action BM1102 "Ciliates as model systems to study genome evolution, mechanisms of non-Mendelian inheritance, and their roles in environmental adaptation" 2011-2015 (Head prof. C. Miceli, contractors from ISEA: prof. dr hab. E. Przyboś, dr hab. M. Prajer, dr hab. S. Tarcz, dr N. Sawka-Gądek.
"Trans-generational epigenetic inheritance, genome defense and mating incompatibility in the Paramecium aurelia complex of 15 sibling species" 2013-2018 (Head dr S. Duharcourt contractors from ISEA: prof. dr hab. E. Przyboś, dr hab. M. Prajer, dr hab. S. Tarcz, dr N. Sawka-Gądek).
Przyboś E. Tarcz S. 2019. Global molecular variation of Paramecium jenningsi complex (Ciliophora, Protista). A starting point for further, detailed biogeography surveys. Systematics and Biodiversity 17: 527-539.
Przyboś E., Rautian M., Beliavskaya A., Tarcz S. 2019. Evaluation of the molecular variability and characteristics of Paramecium polycaryum and Paramecium nephridiatum, within subgenus Cypriostomum (Ciliophora, Protista). Molecular Phylogenetics and Evolution 132: 296–306.
Przyboś E. Tarcz S. 2018. New Stands of the Paramecium aurelia spp. Complex (Protista, Oligohymenophorea) in Ethiopia, Madagascar, Taiwan, and Romania. Folia Biologica (Kraków) 66: 111-119.
Tarcz S., Sawka-Gądek N., Przyboś E. 2018. Worldwide sampling reveals low genetic variability in populations of the freshwater ciliate Paramecium biaurelia (P. aurelia species complex, Ciliophora, Protozoa). Organisms Diversity & Evolution 18: 39-50.
Przyboś E., Tarcz S. 2016. Paramecium jenningsi complex: existence of three cryptic species confirmed by multi-locus analysis and strain crosses, Systematics and Biodiversity, 14:2, 140-154.
Przyboś E., Tarcz S., Rautian M., Sawka N. 2015. Delimiting Species Boundaries within a Paraphyletic Species Complex: Insights from Morphological, Genetic, and Molecular Data on Paramecium sonneborni (Paramecium aurelia species complex, Ciliophora, Protozoa). Protist, 166(4):438-456
Singh D. P., Saudemont B., Guglielmi G., Arnaiz O., Jean-François Gout J.-F., Prajer M., Potekhin A., Przyboś E., Aubusson-Fleury A., Bhullar S., Bouhouche B., Lhuillier-Akakpo M., Tanty V., Blugeon C., Alberti A., Labadie K., Aury J.-M., Sperling L.., Duharcourt S., Meyer E. 2014. Genome-defence small RNAs exapted for epigenetic mating-type inheritance. Nature 509: 447-452.
Tarcz S., Rautian M., Potkhin A., Sawka N., Beliavaskaya A., Kiselev A., Nekrasova I., Przyboś E. 2014. Paramecium putrinum (Ciliophora, Protozoa): The first insight into the variation of two DNA fragments – Molecular support for the existence of cryptic species. Molecular Phylogenetics and Evolution 73:140-145
Tarcz S., Przyboś E., Surmacz M. 2013. An assessment of haplotype variation in ribosomal and mitochondrial DNA fragments suggests incomplete lineage sorting in some species of the Paramecium aurelia complex (Ciliophora, Protozoa). Molecular Phylogenetics and Evolution 67: 255-265.
Arnaiz O. Mathy N., Baudry C., Malinsky S., Aury J.-M., Denby Wilkes C., Garnier O., Labadie K., Lauderdale B., Le Muël A., Marmignon A., Nowacki M., Poulain J., Prajer M., Wincker P., Meyer E., Duharcourt S., Duret L., Betermier M., Sperling L. 2012. The Paramecium germline genome provides a niche for intragenic parasitic DNA: evolutionary dynamics of internal eliminated sequences. PLoS Genetics 8: e1002984.