Comparative analysis of structure of allopolyploid liverwort Pellia borealis and ancestral taxa

Pellia borealis Lorb. is a simple thalloid liverwort that originated after hybridization between two allopatric taxa: Pellia epiphylla N and Pellia epiphylla S. The morphological and anatomical similarity of Pellia species along with its plasticity cause difficulties in clearly defining the species. Species from the Pellia epiphylla complex differ from the remaining Pellia species by bisexuality. Microstructure of the gametophytes of all three taxa and sporophytes of P. borealis and P. epiphylla S was investigated using scanning electron microscopy. As a result of these observations, some new diagnostic characters between analyzed taxa were discovered. P. borealis shows a different pattern of papillae distribution on the dorsal surface of the thallus compared to ancestral taxa and has larger cells. P. epiphylla N was distinguished by the localization and shape of archegonia. Comparison of P. borealis and P. epiphylla S capsule surface showed a significantly different microstructure

Chromosome variations in regenerants of Arabidopsis thaliana derived from 2- and 6-week-old callus detected using flow cytometry and FISH analyses

Shoot organogenesis was induced from 2- and 6-week-old callus derived from the leaves of Arabidopsis thaliana ecotype Columbia (2n = 10). Regenerated plants were evaluated for chromosomal variations by means of flow cytometry and fluorescent in situ hybridization (FISH). Flow cytometric measurements revealed the occurrence of diploid, tetraploid, and octoploid plants among the regenerants of 2-week-old calli, whereas only diploid and tetraploid plants were regenerated from the 6-week-old calli. Chromosome counting showed that plants developed from the 2-week-old calli exhibited mixoploidy and a high frequency of aneuploid cells. These plants were infertile and displayed altered morphology. FISH with 5S and 25S rDNA probes allowed to detect some structural chromosomal rearrangements in regenerated plants. Along with cells which exhibited correct localisation of rDNA loci, also cells bearing chromosomal translocations, deletions or duplications were found. The type of structural aberrations varied between diploid and tetraploid regenerants

Cytogenetic characterization of the Arabidopsis thaliana natural tetraploid ecotype Warschau stability during in vitro regeneration

The morphological and cytogenetic features of the natural autotetraploid Arabidopsis thaliana ecotype Warschau (Wa-1) were investigated. Most of the Warschau plant organs that were analyzed showed higher size values in comparison with diploid Columbia plants. The tetraploid chromosome number was confirmed by analysis of mitotic metaphase cells and rDNA loci were localized. 35S rDNA loci were present on chromosomes 2 and 4, while 5S rDNA, which is polymorphic among A. thaliana ecotypes, were present on chromosomes 4 and 5. Well-characterized autotetraploid plant material was used for in vitro culture to investigate somaclonal variation. Efficient regeneration through organogenesis was achieved. Most of the plants obtained in vitro exhibited an unchanged ploidy level. Detailed cytogenetic analysis that included chromosome, chromocenters and rDNA signals numbers, revealed the stability of regenerants. Based on these data we recommend the ecotype Warschau as a well-characterized plant material for future investigations on the consequences of polyploidy for the genome