Electrophoretic Karyotype Polymorphism of Sibling Species of the Paramecium aurelia Complex

Abstract

Variability of karyotypes is one of the main mechanisms of speciation in organisms. Electrophoretic karyotypes of the macronucleus (MAC) obtained by pulsed-field gel electrophoresis were compared for 86 strains of all 15 sibling species of the Paramecium aurelia complex in order to determine if karyotype differences corresponded to biological species boundaries. Because the electrophoretic karyotype of the MAC reflects indirectly the frequency and distribution of fragmentation sites in the micronuclear (MIC) chromosomes, any change in MAC electrophoretic karyotype may be a marker of certain chromosomal mutations in the MIC. Thirteen main variants of electrophoretic MAC karyotypes were observed in this species complex. Ten of them appeared to correspond to biological species, while the three other variants characterized several species each. Intraspecific polymorphism was observed for several species: in some cases a certain variant of MAC karyotype was specific for all strains from the same part of the world. Distribution of the MAC karyotype variants along molecular phylogenetic trees of the P. aurelia complex shows that isolation of each species or group of species of this complex was accompanied by divergence in the molecular organization of the genome.

The Size of DNA Molecules and Chromatin Organization in the Macronucleus of the Ciliate Didinium nasutum (Ciliophora)

“…This suspension was poured into templates to prepare agarose blocks as described earlier (Nekrasova et al. ). The blocks were placed into a lysing buffer (0.5 M EDTA, pH 9.5; 10% sodium lauroylsarcosine; 100 μg/ml proteinase K; Sigma Chem.…”

“…The resulting cell suspension was mixed in a 1:1 ratio with molten 1.5% SeaKem agarose (FMC Corp., Philadelphia, PA) in 0.125 M EDTA, pH 8.0, at 50°C. This suspension was poured into templates to prepare agarose blocks as described earlier (Nekrasova et al 2010). The blocks were placed into a lysing buffer (0.5 M EDTA, pH 9.5; 10% sodium lauroylsarcosine; 100 lg/ml proteinase K; Sigma Chem.…”

“…Samples of Paramecium quadecaurelia DNA were prepared as described earlier (Nekrasova et al 2010). Saccha-romyces cerevisiae chromosomes (CHEF DNA Size Marker #170-3605; Bio-Rad Laboratories, M€ unchen, Germany) were used as electrophoretic markers.…”

“…The PFGE was carried out using an original apparatus (Mezhevaya et al 1990), the reorientation angle was 120°. The different pulse/duration PFGE conditions were used as described by Nekrasova et al (2010) and Rautian and Potekhin (2002). The 4-mm-thick 1% SeaKem agarose (FMC Corp.) gels were prepared with 0.5X TBE buffer.…”

RNA interference in formation of the somatic genome of ciliates Paramecium and Tetrahymena

“…Размер мини-хромосом МАК tetrahymena и Paramecium составляет от 50 до 2000 т. п. н. [21][22][23]. Амплификация мини-хромосом приводит к плоидности МАК около 800n для P. tetraurelia и около 50n для t. thermophila [7].…”