Estimation of the relative DNA content in species of the genus Spiraea, sections Chamaedryon and Glomerati by flow cytometry

The relative DNA content was studied in seven species of the genus Spiraea L., section Chamaedryon Ser., and in two species, section Glomerati Nakai, from 28 natural populations growing in Asian Russia. The cell nuclei were isolated from a leaf tissue. The relative intensity of fluorescence was measured using flow cytometry of propidium iodide-stained nuclei. The analysis was performed using a CyFlowSpace device (Germany, Sysmex Partec) with a laser radiation source of 532 nm. Fresh leaves of Solanum lycopersicum cv. ‘Stupice’ were used as an internal standard. Data on the relative DNA content are presented for the first time for S. flexuosa Fisch ex Cambess. (0.42–0.47 pg), S. ussuriensis Pojark. (0.49–0.52; 0.85 pg), S. alpina-Pall. (0.49–0.51 pg), S. media Schmidt. (0.45; 0.98–1.01 pg), S. trilobata L. (0.46 pg), S. hypericifolia L. (0.49–0.52 pg) and S. aquilegifolia Pall. (0.48–0.51 pg). Mesophytic species of the genus Spiraea growing in the forest zone (S. chamaedryfolia L. and S. media) exhibit a 2-fold higher relative DNA content (C-value) compared to xerophytic species (S. hypericifolia, S. crenata L., S. aquilegifolia and S. trilobata) and species confined only to mountain areas (S. alpinа, S. trilobata and S. aquilegifolia).

ИССЛЕДОВАНИЕ РАЗМЕРА ГЕНОМА ПРЕДСТАВИТЕЛЕЙ РОДА POTENTILLA L. (ROSACEAE JUSS.)

<p>In our study, 15 representatives of the genus <em>Potentilla</em> L. were analyzed to obtain the relative DNA content and monoploid genome size in the seeds by flow cytometry method. For these <em>Potentilla</em> species, except <em>P. argentea </em>and<em> P. norvegica</em>, DNA content and genome size are revealed for the first time. As a result, the following data were obtaining: representatives of the older section <em>Desertae</em> are diploids with the large monoploid genome size. The genome of <em>P. asiatica</em> (Chrysanthae section) are decrease up to 0.35 pg, while the ploidy is increased to 4. Representatives of the <em>Multifidae</em> and <em>Supinae</em> section are presented with tetra- and hexaploid species with the 0.3 pg of the monoploid genome size. In section Tanacetifoliae are observed a further decrease of the genome size, representatives basically tetraploids. Thus, in the genome size evolution of a <em>Potentilla </em>genera are observed the increase of ploidy with significant reductions in monoploid genome size. This fact proves the general theory of genome evolution of angiosperms, directed towards its reduction. Linear regression analysis was showed a positive correlation between chromosome number and genome size of the representatives of the <em>Potentilla </em>genera. This suggests that between genome size and the number of chromosomes in <em>Potentilla </em>species are linear dependence. Pearson correlation analysis confirmed this result: the correlation coefficient is 0.97 at P&lt;0.05. </p>

УРОВНИ ПЛОИДНОСТИ И ОТНОСИТЕЛЬНОГО СОДЕРЖАНИЯ ДНК В КУЛЬТУРЕ КЛЕТОК И ТКАНЕЙ РАСТЕНИЙ IN VITRO

<p>We presented results of variations in the ploidy level and the genome size of the <em>R. acetosa</em> regenerants. These regenerants was obtained by indirect and direct morphogenesis in in vitro culture. Explants were prepared from seedlings on the three-leaf stage of plant development. More than 100 explants were used to stimulate the indirect and direct morphogenesis. Mesophilic explants were cultured on the MS nutrient medium containing auxin to callus proliferation (2 mg/L NAA, 1 mg/L BA). Cultivation of the callus was maintained for 4 weeks followed by an indirect morphogenes. Indirect morphogenesis stimulated on the MS medium with cytokinin and gibberellic acid predominance (0.5 mg/L BA, 0.2 mg/L GA3). Direct stimulate morphogenesis from the apical meristem of seedlings on nutrient media with a predominance of cytokinins (1 mg/L BA, 0.25 mg/L NAA). Rhizogenesis have stimulated by transferring of the regenerants to the ½MS medium supplemented with 0.2 mg/L of NAA. Research of a ploidy level and genome size was performed by flow cytometry used propidium iodide staining with <em>Vicia faba</em> cv “Innovec” (2C=26.90 pg) as internal DNA standard. We calculated the relative DNA content (2C) for <em>R. acetosa</em> equal to 6,98 pg. Cytogenetical analisis showed that the maximum genome size variation recorded for regenerants obtained through the indirect morphogenesis. Variations in the genome size of the regenerants obtained by direct morphogenesis deviates from the control group to 0.30 pg (2С=7.28 pg) and after indirect morphogenesis to 1.04 pg (2С=8.2 pg). Cytogenetical analysis of the regenerated plants showed the presence of different somatic chromosome numbers ranging from 2n = 14 to 2n = 28. The relative DNA content of tetraploid forms was 11.87 pg. In our study was shown, that the most effective method of plant conservation in the <em>in vitro</em> culture is a direct morphogenesis. Analysis of the relative nuclear DNA content and chromosome counts of regenerants obtained by indirect morphogenesis from the callus cultures showed significant variations in the DNA content, as well as the appearance of polyploid forms. Therefore, long-term cultivation of callus cultures increases the probability of genomic aberrations, which reduces the stability of the plant genome.</p>

Relationships among Morphological Characters, Isozymes Polymorphism and DNA Variability – the Impact on Lactuca Germplasm Taxonomy

Fifty one accessions of nineteen Lactuca species, the hybrid L. serriola &times; L. sativa and the related species Mycelis muralis were evaluated for morphological variability, esterase (EST) polymorphism, Amplified Fragment Length Polymorphism (AFLP) and relative DNA content. Sixteen Lactuca accessions were classified taxonomically on the basis of morphology, isozyme analysis and AFLP. Twenty-eight bands (isoforms) of EST were recorded allowing 82% of accessions to be distinguished. The relative DNA content, measured using flow-cytometry (DAPI staining), ranged from 2.02 pg in L. capensis to 17.96 pg in L. canadensis. The results from AFLP analysis and the relative DNA content measurement corresponded well with recent taxonomic classification of the genus Lactuca. &nbsp;

Crossability, Cytogenetics, and Reproductive Pathways in Rudbeckia Subgenus Rudbeckia

Rudbeckia L. are valuable nursery crops that offer broad adaptability and exceptional ornamental merit. However, there is little information on interspecific and interploid crossability and ploidy levels of specific cultivars. The objectives of this study were to determine the ploidy levels and relative DNA contents (genome sizes) of selected species and cultivars, to evaluate self-compatibility and crossability among species and ploidy levels, and to explore reproductive pathways in triploid R. hirta L. with the goal of facilitating future breeding endeavors and development of new hybrids. Reciprocal interspecific crosses were performed between R. hirta cultivars and R. fulgida Ait., R. missouriensis Engelm. ex C.L. Boynton & Beadle, and R. subtomentosa Pursh. as well as reciprocal interploid crosses among four R. hirta cultivars. A combination of relative DNA content analysis and chromosome counts was used to test for hybridity and to determine ploidy levels for selected species, cultivars, and interploid R. hirta F1 hybrids. Of the specific clones tested, R. subtomentosa and R. missouriensis were diploid, R. fuligida varieties were tetraploid, and R. hirta include both diploid and tetraploid cultivars. Mean 1Cx DNA content varied over 320% among species. The interploid R. hirta crosses produced triploids as well as pentaploids and hexaploids. Seedlings from open-pollinated triploid R. hirta appeared, based on diverse phenotypes and DNA contents, to be aneuploids resulting from sexual fertilization, not apomixis. Of the 844 seedlings from interspecific F1 crosses, only one individual, R. subtomentosa ×R. hirta, had a DNA content intermediate between its parents and was confirmed as the only interspecific hybrid. Although most taxa had low self-fertility, seedlings (with genomic sizes similar to their maternal parent) resulted after interspecific crosspollination, indicating that pseudogamy is one reproductive pathway in Rudbeckia species.

Solutions for the Cell Cycle in Cell Lines Derived from Human Tumors

The goal of the paper is to compute efficiently solutions for model equations that have the potential to describe the growth of human tumor cells and their responses to radiotherapy or chemotherapy. The mathematical model involves four unknown functions of two independent variables: the time variabletand dimensionless relative DNA contentx. The unknown functions can be thought of as the number density of cells and are solutions of a system of four partial differential equations. We construct solutions of the system, which allow us to observe the number density of cells for differenttandxvalues. We present results of our experiments which simulate population kinetics of human cancer cellsin vitro. Our results show a correspondence between predicted and experimental data.