Aleksandra Grabowska-Joachimiak

Karyotype structure and chromosome fragility in the grass Phleum echinatum Host

Phleum echinatum Host (2n = 2x = 10) is an annual Mediterranean species which differs from other representatives of the genus Phleum by reduced chromosome number, asymmetric karyotype and unusually high amount of DNA in the genome. Chromosomes of this plant were studied using conventional acetic-orcein staining and fluorescence in situ hybridization (FISH). FISH showed the major 35S ribosomal DNA (rDNA) site at the secondary constriction of satellite chromosome (3) and the minor 35S rDNA site near 5S rDNA cluster in the monobrachial chromosome 5. Telomeric repeats were detected at all chromosome ends within secondary constriction in satellited chromosome 3 and at the centromeric regions of chromosomes 1 and 2. Intrachromosomally located telomeric repeats are probably traces of chromosomal rearrangements that have shaped P.echinatum genome; they were prone to breakage which was manifested in chromosome fragmentation. The most distinct telomeric signals, suggesting massive amplification of interstitial telomeric sequences (ITRs), were observed at the nucleolar organizer region (NOR) of the third chromosome pair. Double FISH confirmed co-localization of telomeric and 35S rDNA repeats in this locus characterized by the biggest fragility in the karyotype. Fragile sites of P.echinatum, composed of amplified telomeric repeats, may bear a resemblance to metazoan rare fragile sites enriched in microsatellite repeats.

Synergids and filiform apparatus in the sexual and apomictic dandelions from section Palustria (Taraxacum, Asteraceae)

An evolutionary trend to reduce “unnecessary costs” associated with the sexual reproduction of their amphimictic ancestors, which may result in greater reproductive success, has been observed among the obligatory apomicts. However, in the case of the female gametophyte, knowledge about this trend in apomicts is not sufficient because most of the ultrastructural studies of the female gametophyte have dealt with amphimictic angiosperms. In this paper, we tested the hypothesis that, in contrast to amphimictic plants, synergids in apomictic embryo sacs do not form a filiform apparatus. We compared the synergid structure in two dandelions from sect. Palustria: the amphimictic diploid Taraxacum tenuifolium and the apomictic tetraploid, male-sterile Taraxacum brandenburgicum. Synergids in both species possessed a filiform apparatus. In T. brandenburgicum, both synergids persisted for a long time without any degeneration, in spite of the presence of an embryo and endosperm. We propose that the persistent synergids in apomicts may play a role in the transport of nutrients to the embryo.

Polyploidy, alien species and invasiveness in Polish angiosperms

Chromosome numbers, mainly for Polish flora, were examined in order to investigate whether such features as chromosome numbers and polyploid frequencies are correlated with a plant’s origin (native vs. alien) and invasiveness. Polyploid frequencies were estimated using three methods: the 11 and 14 thresholds and the 3.5 x value. Comparisons of the 2n values were done on different levels: in all angiosperms and in dicots and monocots separately. Invasive and non-invasive plants were compared in the entire dataset and in alien species only. Significant differences in both chromosome numbers and polyploid frequencies between alien and native species were observed. In most cases, native plants had more chromosomes and were more abundant in polyploids than in alien species. Also, monocots had higher polyploid frequencies than dicots. Comparisons of invasive and non-invasive plants done for all of the data and only for alien species showed that invasive species generally had more chromosomes and polyploids were more frequent in them than in the latter group; however, these differences were not always statistically significant. Possible explanations for these observations are discussed.

Differentiation of the pollen size in five representatives of Taraxacum sect. Palustria

Measurements of the pollen size in 5 species of Taraxacum sect. Palustria at three levels of ploidy: 2n = 3x = 24 (T. paucilobum), 2n = 4x = 32 (T. vindobonense, T. trilobifolium), 2n = 5x = 40 (T. mendax) and one taxon of unknown number of chromosomes 2n = ? (T. portentosum) are presented in this paper. Obtained results indicate a lack of distinct positive correlation between the pollen size and ploidy in the studied group of plants. Distinct relationship was, however, found between ploidy and the range of pollen size and shape variability. Most variable were the pollen grains of triploid T. paucilobum and the least — those in pentaploid T. mendax. Ranges of pollen variability in tetraploid T. trilobifolium and T. vindobonense and in T. portentosum of unknown number of chromosomes showed intermediate values.

Karyotype and nuclear DNA content of hexa-, octo-, and duodecaploid lines of Bromus subgen. Ceratochloa

The subgenus Ceratochloa of the genus Bromus includes a number of closely related allopolyploid forms or species that present a difficult taxonomic problem. The present work combines data concerning chromosome length, heterochromatin distribution and nuclear genome size of different 6x, 8x and 12x accessions in this subgenus. Special attention is paid to the karyotype structure and genomic constitution of duodecaploid plants recently found in South America. Hexaploid lineages possess six almost indistinguishable genomes and a nuclear DNA content between 12.72 pg and 15.10 pg (mean 1Cx value = 2.32 pg), whereas octoploid lineages contain the same six genomes (AABBCC) plus two that are characterized by longer chromosomes and a greater DNA content (1Cx = 4.47 pg). Two duodecaploid accessions found in South America resemble each other and apparently differ from the North American duodecaploid B. arizonicus as regards chromosome size and nuclear DNA content (40.00 and 40.50 pg vs. 27.59 pg). These observations suggest that the South American duodecaploids represent a separate evolutionary lineage of the B. subgenus Ceratochloa, unrecognized heretofore.

Cytogenetic analysis of Miscanthus × giganteus and its parent forms

This study aimed at comparative karyotype analysis and measurement of the nuclear DNA amount in giant miscanthus, Miscanthus × giganteus, and its hypothetical ancestors: eulalia grass (M. sacchariflorus) and porcupine grass (M. sinensis). The triploid chromosome number 2n  =   57 in M. × giganteus and the diploid chromosome number 2n  =   38 in the other species were confirmed. In the karyotype of giant miscanthus three satellite chromosomes were observed, whereas in M. sinensis there were two and in M. sacchariflorus probably four chromosomes of this type. In the first species 1–4 B-chromosomes were evidenced. The highest proportion of the C-banding/DAPI (4’,6-diamidino-2-phenylindole) positive heterochromatin was found in M. sinensis cv. Gracillimus, and the least in the M. sinensis M07 genome. The banding patterns observed in M. × giganteus resembled those observed in M. sacchariflorus. The 2C nuclear DNA content in M. × giganteus was 7.47 pg and in M. sacchariflorus it was 5.14 pg; two analysed lines of M. sinensis differed in 2C DNA value (5.18 pg and 5.49 pg).

Karyotyping of Chinchilla lanigera Mol. (Rodentia, Chinchillidae)

There is relatively little information about the karyotype structure of the chinchilla (Chinchilla lanigera Mol.), an endemic South American rodent with 2n = 64 chromosomes and “duplicate-type X chromosome”. The species, endangered in nature, is a popular domesticated animal providing one of the most valuable furs in the world. In the present study, detailed karyotype analysis of the domestic chinchilla was performed using selected methods of differential chromosome staining (G-banding, C-banding, C-banding/DAPI, CMA3/DA/DAPI, Ag-NOR staining) as well as fluorescence in situ hybridization (FISH) with rDNA and telomeric (TTAGGG)n repetitive probes. The analysed specimens showed 59 metacentric and five submetacentric chromosomes. C-banding revealed mainly centromeric distribution of heterochromatin on the autosomes, interstitial and centromeric C-positive bands on the X chromosome and almost entirely heterochromatic nature of the Y chromosome. The average amount of heterochromatin in the haploid autosome set (31A) was 11.44%, whereas in the X chromosome 39.84%. Two active nucleolar organizer regions (NORs) and 45S rDNA repeats were located within one pair of big autosomes. In respect of morphology and G-banding patterns, the chinchilla chromosomes were arranged in homologous pairs and a G-banded karyotype was proposed. The obtained results could be the first step towards determination of the standard karyotype for the breeding chinchilla.

Woodsia pulchella in the Western Carpathians: A Relict Species at the Northern Limit of Its Distribution

In the Western Carpathians, we identified a strongly isolated stand of a species belonging in the fern genus Woodsia. Based on morphological characters, nuclear DNA content analysis and chromosome counts, we determined that the species occurring in the Polish Tatra Mts. is W. pulchella and not W. alpina, as was supposed before. The population is situated 365 km from the nearest one in the eastern Alps in Austria. Woodsia pulchella grows on northern slopes of the Giewont massif in the Western Tatra, on dolomite rocks between 1100–1480 m a.s.l. at two closely-situated localities. The current distribution of W. pulchella in Europe is detailed and the evolutionary origin of this very rare and relict species is discussed.

Testing the translocation hypothesis and Haldane’s rule in Rumex hastatulus

The translocation hypothesis regarding the origin of the XX/XY1Y2 sex chromosome system was tested with reference to the F1 hybrids between two chromosomal races of Rumex hastatulus. The hybrids derived from reciprocal crossing between the Texas (T) race and the North Carolina (NC) race were investigated for the first time with respect to the meiotic chromosome configuration in the pollen mother cells, pollen viability, and sex ratio. A sex chromosome trivalent in the NC × T males and two sex chromosome bivalents in the T × NC males were detected. The observed conjugation patterns confirmed the autosomal origin of the extra chromosome segments occurring in the North Carolina neo-sex chromosomes. Decreased pollen viability was found in the T × NC hybrid in contrast to the NC × T hybrid and the parental forms. Moreover, only in the T × NC hybrid sex ratio was significantly female-biased (1:1.72). Thus, Haldane’s rule for both male fertility and male rarity was shown in this hybrid. According to the authors’ knowledge, R. hastatulus is just the second plant with sex chromosomes in which Haldane’s rule was evidenced.