Comparative cytogenetic analysis of diploid and hexaploid Chenopodium album agg.

Two cytotypes of Chenopodium album, diploid (2n=2x=18) and hexaploid (2n=6x=54), were analysed using flow cytometry and aFisH experiment. The genome size was indicated as 1.795 pg for the diploid and 3.845 pg for the hexaploid plants which suggested genome downsizing in the evolution of hexaploid cytotype. Double FisH with 25s rDNA and 5s rDNA allowed three to five homologue chromosome pairs to be distinguished depending on the cytotype. The variation in size and number of rDNA sites between the polyploid C. album and its putative diploid ancestor indicated that rDNA loci underwent rearrangements after polyploidization. Flow cytometry measurements of the relative nuclear DNA content in the somatic tissue of C. album revealed extensive endopolyploidization resulting in tissues comprising a mixture of cells with a different DNA content (from 2Cto 32C) in varying proportions. The pattern of endopolyploidy was characteristic for the developmental stage of the plant and for the individual organ. Polysomaty was not observed in the embryo tissues however endo- polyploidization had taken place in most tested organs of seedlings. The endopolyploidy in diploid and hexaploid C. album was compared to find any relationship between the pattern of polysomaty and polyploidy level in this species. This revealed that polyploid plants showed a decline in the number of endocycles as well as in the frequency of endopolyploidy cells compared to diploid plants

DNA damage in Crepis capillaris cells in response to in vitro condition

We analyzed DNA damage, mitotic activity and polyploidization in Crepis capillaris callus cells during short- and long-term in vitro culture, and the influence of plant growth regulators on these processes. Changes in the concentration of growth regulators altered the stability of callus. The level of DNA damage was highly dependent on the growth regulator composition of the medium. Cytokinin at high concentrations damaged DNA in the absence of auxin. Short- and long-term callus differed in sensitivity to growth regulators. Mitotic activity changed when callus was transferred to medium with modified growth regulators. Callus cell nuclear DNA content increased with age and in response to plant growth regulators. Hormones played a role in the genetic changes in C. capillaries callus culture. We demonstrated the usefulness of C. capillaris callus culture as a model for analyzing the effect of culture conditions, including plant growth regulators, on genetic stability

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

Cytogenetic studies of three European species of Centaurea L. (Asteraceae)

Cytogenetic analysis of several populations of Centaurea jacea (2n = 4x = 44), C. oxylepis (2n = 4x = 44) and C. phrygia (2n = 2x = 22) was performed using flow cytometry, differential chromosome staining and FISH. In all species Arabidopsis-type telomeric repeats hybridized only to the terminal part of chromosomes. In C. phrygia three pairs and in C. oxylepis six pairs of chromosomes revealed the hybridization signals of 45S rDNA. Centaurea jacea showed polymorphism in the 45S rDNA loci number, five or six pairs of sites were observed. 5S rDNA loci were located in two pairs of chromosomes in C. phrygia. In C. jacea and C. oxylepis the number and position of 5S rDNA loci were the same: three pairs located interstitially and one terminally. The genome size of the diploid C. phrygia was established as 2.14 pg/2C. The genomes of tetraploid species were nearly two times larger and genome size polymorphism was observed among C. jacea populations

Influence of a heavy-metal-polluted environment on Viola tricolor genome size and chromosome number

Intraspecific changes in genome size and chromosome number lead to divergence and species evolution. Heavy metals disturb the cell cycle and cause mutations. Areas contaminated by heavy metals (metalliferous sites) are places where microevolutionary processes accelerate; very often only a few generations are enough for a new genotype to arise. This study, which continues our long-term research on Viola tricolor (Violaceae), a species occurring on both metalliferous (Zn, Pb, Cd, Cu) and non-metalliferous soils in Western and Central Europe, is aimed at determining the influence of environments polluted with heavy metals on genome size and karyological variability. The genome size of V. tricolor ranged from 3.801 to 4.203 pg, but the differences between metallicolous and non-metallicolous populations were not statistically significant. Altered chromosome numbers were significantly more frequent in material from the polluted sites than from the non-polluted sites (43% versus 28%). Besides the standard chromosome number (2n = 26), aneuploid cells with lower (2n = 18–25) or higher (2n = 27, 28) chromosome numbers were found in plants from both types of site, but polyploid (2n = 42) cells were observed only in plants from the metalliferous locality. The lack of correlation between chromosome variability in root meristematic cells and genome size estimated from peduncle cells can be attributed to elimination of somatic mutations in generative meristem, producing chromosome-stable non-meristematic tissues in the peduncle

Genome size variation in Chenopodium quinoa (Chenopodiaceae)

The extent and significance of intraspecific genome size variation were analysed in quinoa (Chenopodium quinoa Willd.), a pseudocereal important for human consumption in the Andean region of South America. Flow cytometry, with propidium iodide as the DNA stain, was used to estimate the genome size of 20 quinoa accessions from Ecuador, Peru, Bolivia, Argentina, Chile and the USA. Limited genome size variation was found among the analysed accessions. The differences between the accessions were statistically significant but the maximum inter-accession difference between the populations with the largest and the smallest genome reached only 5.9%. The largest genome was found in population C4 from Chile (mean 3.077 pg/2C) and the smallest in the Peruvian population P2 (mean 2.905 pg/2C). The variation was not correlated with collection site; however, the quinoa accessions analysed in this study belonged to three distinct geographical groups: northern highland, southern highland and lowland

Brachypodium distachyon - a model plant to study grass genome structure, dynamics and evolution

Plenary Session: Present status of cell, tissue and organ in vitro cultur