COMPARATIVE DESCRIPTION OF MACRONUCLEAR ELECTROPHORETIC KARYOTYPES OF PARAMECIUM PRIMAURELIA AND
PARAMECIUM NOVAURELIA SIBLING SPECIES
I. V. Nekrasova,1 A. A. Potekhin,1, * E. Przybos,2 M. S. Rautian 1
1 Faculty of Biology and Soil Sciences, St. Petersburg State University, Russia, and 2 Institute of Systematics and Evolution of
Animals, Polish Academy of Sciences, Krakow, Poland;
* e-mail: aurelia@fromru.com
The macronuclear genomes of two sibling species belonging to the Paramecium aurelia complex - P. primaurelia and P. novaurelia -
were analyzed by pulsed-field gel electrophoresis (PFGE). Their electrophoretic karyotypes showed a continuous spectrum of different-sized DNA molecules with a
species-specific pattern of banding, which was reproducible and did not change with strain senescence. Thus, P. aurelia macronuclear PFGE profiles could be
described by an approach analogous to that used for the description of metaphase chromosome banding patterns. At first, well-identifiable regions (size fractions) of a
PFGE profile, which can be seen at any resolution, are determined. Then, the bands of the second order of resolution (subfractions) can be defined in some of these
regions. The blocks of the first and second orders can be utilized as inner markers of the PFGE profile allowing precise comparison of different PFGE profiles. Such
comparative analysis has demonstrated some marking differences in organization of the macronuclear genomes of P. primaurelia and P. novaurelia,
and low level of intraspecific polymorphism. Worth noting is that the P. novaurelia strain isolated in USA was different from all other analyzed P.
novaurelia strains originating from Europe. The nature of banding of P. aurelia PFGE profiles is discussed. The revealed high order and stability of the
macronuclear genome organization makes possible searching for new approaches to study the mechanisms of this non-trivial genome formation and maintenance.
Further PFGE analysis of the macronuclear genomes of the other Paramecium species in relation with the Paramecium phylogeny may provide
insights into the directions of the evolution of the macronuclear genome in Ciliata.
Key words: Paramecium aurelia species complex, sibling species, genome of the macronucleus, karyotype, PFGE
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