We analysed chromosome lengths, karyotype structure, and nuclear DNA content (flow cytometry) in diploid (2n=20) and triploid (2n=30) European H. lupulus var. lupulus, American H. lupulus var. neomexicanus (2n=20) and Japanese ornamental hop, H. japonicus (F/2n=16; M/2n=17). Diploid female representatives of H. lupulus var. lupulus and H. l. var. neomexicanus differed in total length of the basal chromosome set (23.16 µm and 25.99 µm, respectively) and nuclear 2C DNA amount (5.598 pg and 6.064 pg) but showed similar karyotype structure. No deviation from the additivity, both in chromosome length and 2C DNA amount was evidenced in triploid monoecious H. lupulus (2n=30, XXY). H. japonicus showed different karyotype structure, smaller basal chromosome set (F/18.04 µm, M/20.66 µm) and lower nuclear DNA amount (F/3.208 pg and M/3.522 pg). There are first evaluations of nuclear genome size in diploid, not commercial representative of European H. lupulus var. lupulus and American H. lupulus var. neomexicanus and first attempt to determine the absolute male and female genome size in two Humulus species.
On the basis of previous studies showing a positive correlation between number of copies of retrotransposons and geographical environment, we hypothesized that different ecogeographical conditions on opposite slopes of Evolution Canyon I could cause intraspecific variation in plant genome size. To test this hypothesis, we chose Lotus peregrinus L. (annual, self-pollinator) as the first candidate because of its biological contrast to the previously studied carob tree (long-lived, cross-pollinator). Absolute nuclear DNA content of 60 genotypes of L. peregrinus was estimated by PI flow cytometry, with tomato (Lycopersicon esculentum cv. Stupicke) as internal reference standard. The mean 2C-value in L. peregrinus was 2.546 pg, ranging from 2.39 pg to 2.71 pg. The mean 2C-value was higher in plants from the south-facing slope (2.549 pg) than from the north-facing slope (2.544 pg), but we were not able to show significant interslope differences in genome size.
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.
Two cytotypes of Chenopodium album, diploid (2n=2x=18) and hexaploid (2n=6x=54), were analysed using flow cytometry and a FISH 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 2C to 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 endopolyploidization 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.
The number of different cell types (NCT) characterizing an organism is often used to quantify organismic complexity. This method results in the tautology that more complex organisms have a larger number of different kinds of cells, and that organisms with more different kinds of cells are more complex. This circular reasoning can be avoided (and simultaneously tested) when NCT is plotted against different measures of organismic information content (e.g., genome or proteome size). This approach is illustrated by plotting the NCT of representative diatoms, green and brown algae, land plants, invertebrates, and vertebrates against data for genome size (number of base-pairs), proteome size (number of amino acids), and proteome functional versatility (number of intrinsically disordered protein domains or residues). Statistical analyses of these data indicate that increases in NCT fail to keep pace with increases in genome size, but exceed a one-to-one scaling relationship with increasing proteome size and with increasing numbers of intrinsically disordered protein residues. We interpret these trends to indicate that comparatively small increases in proteome (and not genome size) are associated with disproportionate increases in NCT, and that proteins with intrinsically disordered domains enhance cell type diversity and thus contribute to the evolution of complex multicellularity.
Since M. sinensis Anderss., M. sacchariflorus (Maxim.) Hack. and M. ×giganteus J.M.Greef & Deuter ex Hodk. and Renvoize have considerably the highest potential for biomass production among Miscanthus Anderss. species, there is an urgent need to broaden the knowledge about cytological characteristics required for their improvement. In this study our objectives were to assess the genome size variation among eighteen Miscanthus accessions, as well as estimation of the monoploid genome size (2C and Cx) of the M. sinensis cultivars, which have not been analyzed yet. The characterization of three Miscanthus species was performed with the use of flow cytometry and analysis of the stomatal length. The triploid (2n = 3x = 57) M. sinensis 'Goliath' and M. ×giganteus clones possessed the highest 2C DNA content (8.34 pg and 7.43 pg, respectively). The intermediate 2C-values were found in the nuclei of the diploid (2n = 2x = 38) M. sinensis accessions (5.52–5.72 pg), whereas they were the lowest in the diploid (2n = 2x = 38) M. sacchariflorus ecotypes (4.58–4.59 pg). The presented study revealed interspecific variation of nuclear DNA content (P<0.01) and therefore allowed for recognition of particular taxa, inter- and intraspecific hybrids and prediction of potential parental components. Moreover, intraspecific genome size variation (P<0.01) was observed in M. sinensis cultivars at 3.62%. The values of the stomatal size obtained for the triploid M. ×giganteus 'Great Britain' (mean 30.70 μm) or 'Canada' (mean 29.67 μm) and diploid M. sinensis 'Graziella' (mean 29.96 μm) did not differ significantly, therefore this parameter is not recommended for ploidy estimation.
Despite long-term research, the aquatic genus Nymphaea still possesses major taxonomie challenges. High phenotypic plasticity and possible interspecific hybridization often make it impossible to identify individual specimens. The main aim of this study was to assess phenotypic variation in Nymphaea taxa sampled over a wide area of Eastern Europe and temperate Asia. Samples were identified based on species-specific genome sizes and diagnostic morphological characters for each taxon were then selected. A total of 353 specimens from 32 populations in Poland, Russia and Ukraine were studied, with nine biometric traits being examined. Although some specimens morphologically matched N. xborealis (a hybrid between N. alba and N. Candida) according to published determination keys, only one hybrid individual was revealed based on genome size data. Other specimens with intermediate morphology possessed genome size corresponding to N. alba, N. Candida or N. tetragona. This indicates that natural hybridization between N. alba and N. Candida is not as frequent as previously suggested. Our results also revealed a considerably higher variation in the studied morphological traits (especially the quantitative ones) in N. alba and N. Candida than reported in the literature. A determination key for the investigated Nymphaea species is provided, based on taxonomically-informative morphological characters identified in our study.
Accumulation of selfish DNA in cells has fundamental consequences for organism metabolism. Detrimental effects of large genome size have been demonstrated for several aspects of performance in plant and animal species. Here we check if a large genome affects occupancy among Coccinelidae and Chrysomelidae occurring in Poland. It was possible to match literature data on distribution and genome-size data for 19 species of chrysomelids and 10 species of coccinelids of different rarity (occurrence expressed as % of Poland area) and body size. There was a marginally significant (P = 0.04) and expected excess of species with large genomes among rare species (<0.73% of area), as well as an excess of species with small genomes among common species (>0.89% of area) However overall correlation was not significant (P = 0.13). Body size was not related to rarity in these species. The detection of this weak signal provides a clue to the important idea that large-scale patterns may stem from differences observed at the cellular level.
The paper presents three new localities of Nasturtium microphyllum reported on the Ilanka River near Rzepin. In one of the localities onerow yellowcress specimens were in the flowering and fruiting stages, while in the two other localities plants were flowering, but they were not bearing fruits. Fruiting specimens were identifi ed on the basis of seed sculpture traits, while flowering plants – by flow cytometry, based on the genome size.
Flow cytometry estimation of 2C nuclear DNA content of the examined Nasturtium species resulted in taxonomic identification of N. × sterile in eight new localities, N. microphyllum in four new localities and N. officinale in one new locality in western Poland. Scanning electron microscopy proved a few of the micromorphological traits of seeds and fruits (size and shape of cells on the fruit septum surface, their anticlinal walls; secondary sculpture on the outer periclinal walls of cells on the siliqua valve internal surface) to be of taxonomic importance.
Prokaryotic or gan isms are ex posed in the course of evo lu tion to var i ous im pacts, result ing of ten in dras tic changes of their ge nome size. De pending on cir cum stances, the same lin eage may di verge into spe cies hav ing sub stan tially re duced genomes, or such whose genomes have un der gone con sid er able en large ment. Ge nome re duc tion is a con se quence of ob li gate intracellular life style ren der ing nu mer ous genes ex pend able. An other con se quence of intracellular life style is re duc tion of ef fec tive pop u la- tion size and lim ited pos si bil ity of gene ac quire mentvia lat eral trans fer. This causes a state of re laxed se lec tion re sult ing in ac cu mu la tion of mildly del e te ri ous mu ta tions that can not be cor rected by re com bi na tion with the wild type copy. Thus, gene loss is usually irreversible. Additionally, constant environment of the eukaryotic cell renders that some bac te rial genes in volved in DNA re pair are ex pand able. The loss of these genes is a prob a ble cause of mutational bias re sult ing in a high A+T con tent. While causes of genome reduction are rather indisputable, those resulting in genome ex pan sion seem to be less ob vi ous. Pre sum ably, the ge nome en large ment is an indirect consequence of adaptation to changing environmental conditions and requires the ac qui si tion and in te gra tion of nu mer ous genes. It seems that the need for a great number of capabilities is common among soil bacteria irrespective of their phylo gen etic re la tion ship. How ever, this would not be pos si ble if soil bac te ria lacked in dig e nous abil i ties to ex change and ac cu mu late ge netic in for ma tion. The lat ter are con sid er ably fa cil i tated when house keep ing genes are phys i cally sep a rated from adaptive loci which are useful only in certain circum stances.
The characteristic features of higher plant mitochondrial genomes: size, structure, recombination activity and evolutionary dynamics, are reviewed with the emphasis on the mitochondrial DNA (mtDNA) of Phaseolus vulgaris. Among all examined eukaryotic organisms, higher plants were found to contain the largest and most complex mitochondrial genomes. The plant mtDNA structure in vivo and mechanisms of evolution are controversial. We present the currently accepted models and how these models correspond to mitochondrial genomes of several common bean lines.
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