Olga Rotreklová

Ecological and evolutionary significance of genomic GC content diversity in monocots

Significance Our large-scale survey of genomic nucleotide composition across monocots has enabled the first rigorous testing, to our knowledge, of its biological significance in plants. We show that genomic DNA base composition (GC content) is significantly associated with genome size and holocentric chromosomal structure. GC content may also have deep ecological relevance, because changes in GC content may have played a significant role in the evolution of Earth’s biota, especially the rise of grass-dominated biomes during the mid-Tertiary. The discovery of several groups with very unusual GC contents highlights the need for in-depth analysis to uncover the full extent of genomic diversity. Furthermore, our stratified sampling method of distribution data and quantile regression-like logic of phylogenetic analyses may find wider applications in the analysis of spatially heterogeneous data. Genomic DNA base composition (GC content) is predicted to significantly affect genome functioning and species ecology. Although several hypotheses have been put forward to address the biological impact of GC content variation in microbial and vertebrate organisms, the biological significance of GC content diversity in plants remains unclear because of a lack of sufficiently robust genomic data. Using flow cytometry, we report genomic GC contents for 239 species representing 70 of 78 monocot families and compare them with genomic characters, a suite of life history traits and climatic niche data using phylogeny-based statistics. GC content of monocots varied between 33.6% and 48.9%, with several groups exceeding the GC content known for any other vascular plant group, highlighting their unusual genome architecture and organization. GC content showed a quadratic relationship with genome size, with the decreases in GC content in larger genomes possibly being a consequence of the higher biochemical costs of GC base synthesis. Dramatic decreases in GC content were observed in species with holocentric chromosomes, whereas increased GC content was documented in species able to grow in seasonally cold and/or dry climates, possibly indicating an advantage of GC-rich DNA during cell freezing and desiccation. We also show that genomic adaptations associated with changing GC content might have played a significant role in the evolution of the Earth’s contemporary biota, such as the rise of grass-dominated biomes during the mid-Tertiary. One of the major selective advantages of GC-rich DNA is hypothesized to be facilitating more complex gene regulation.

Enriching Ploidy Level Diversity: the Role of Apomictic and Sexual Biotypes of Hieracium subgen. Pilosella (Asteraceae) that Coexist in Polyploid Populations

The capacity to generate variation in ploidy and reproductive mode was compared in facultatively apomictic versus sexual maternal plants that coexist in two model populations. The population structure was studied in polyploid hybrid swarms comprised of Hieracium pilosella (usually sexual, less commonly apomictic), H. bauhini (apomictic), and their hybrids (sexual, apomictic, or sterile). Relationships among established biotypes were proposed on the basis of their DNA ploidy level/chromosome number, reproductive mode and morphology. Isozyme phenotypes and chloroplast DNA haplotypes were assayed in the population that was richer in hybrids. The reproductive origin of seed progeny was identified in both sexual and apomictic mothers, using alternative methods: the karyological, morphological and reproductive characters of the cultivated progeny were compared with those of respective mothers, or flow cytometric seed screening was used. In both populations, the progeny of sexual mothers mainly retained a rather narrow range of ploidy level/chromosome number, while the progeny of facultatively apomictic mothers was more variable. The high-polyploid hybrids, which had arisen from the fertilization of unreduced egg cells of apomicts, mainly produced aberrant non-maternal progeny (either sexually and/or via haploid parthenogenesis). Apparently, such versatile reproduction resulted in genomic instability of the recently formed high-polyploid hybrids. While the progeny produced by both true apomictic and sexual mothers mostly maintained the maternal reproductive mode, the progeny of those ‘versatile’ mothers was mainly sexual. Herein, we argue that polyploid facultative apomicts can considerably increase population diversity.

Intrapopulation Genome Size Dynamics in Festuca pallens

BACKGROUND AND AIMS It is well known that genome size differs among species. However, information on the variation and dynamics of genome size in wild populations and on the early phase of genome size divergence between taxa is currently lacking. Genome size dynamics, heritability and phenotype effects are analysed here in a wild population of Festuca pallens (Poaceae). METHODS Genome size was measured using flow cytometry with DAPI dye in 562 seedlings from 17 maternal plants varying in genome size. The repeatability of genome size measurements was verified at different seasons through the use of different standards and with propidium iodide dye; the range of variation observed was tested via analysis of double-peaks. Additionally, chromosome counts were made in selected seedlings. KEY RESULTS AND CONCLUSIONS Analysis of double-peaks showed that genome size varied up to 1.188-fold within all 562 seedlings, 1.119-fold within the progeny of a single maternal plant and 1.117-fold in seedlings from grains of a single inflorescence. Generally, genome sizes of seedlings and their mothers were highly correlated. However, in maternal plants with both larger and smaller genomes, genome sizes of seedlings were shifted towards the population median. This was probably due to the frequency of available paternal genomes (pollen grains) in the population. There was a stabilizing selection on genome size during the development of seedlings into adults, which may be important for stabilizing genome size within species. Furthermore, a positive correlation was found between genome size and the development rate of seedlings. A larger genome may therefore provide a competitive advantage, perhaps explaining the higher proportion of plants with larger genomes in the population studied. The reason for the observed variation may be the recent induction of genome size variation, e.g. by activity of retrotransposons, which may be preserved in the long term by the segregation of homeologous chromosomes of different sizes during gametogenesis.

Chromosome numbers within the Achillea millefolium and the A. distans groups in the Czech Republic and Slovakia

TheAchillea millefolium group is represented in the Czech Republic and Slovakia by six species.Achillea setacea andA. asplenifolia are diploid;A. collina andA. pratensis are tetraploid;A. millefolium is hexaploid; andA. pannonica is octoploid. The populations from Slovakia of theA. distans group, distributed mainly in Central and south-eastern Europe, were all hexaploid. The presence of these taxa in the area studied was documented by means of chromosome counts in 285 plants originating from 110 mainly natural populations. Results of the chromosome counts are discussed against a background of literature data from Europe. For the species studied, brief descriptions as well as comments on their distribution and ecology are provided.

CYTOGEOGRAPHICAL SURVEY OF ELEOCHARIS SUBSER. ELEOCHARIS IN EUROPE 1: ELEOCHARIS PALUSTRIS

Chromosome numbers forEleocharis palustris subsp.palustris (based on 70 samples from Austria, Bulgaria, Croatia, the Czech Republic, Germany, Greece, Hungary, Lithuania, Romania, Russia, Slovakia, Slovenia, and Sweden) andEleocharis palustris subsp.vulgaris (based on 74 samples from Austria, the Czech Republic, Denmark, Germany, Ireland, Latvia, Luxembourg, the Netherlands, Portugal, and Sweden) are given. Also the chromosome number estimates based on relative DNA contents of plants from 8 localitiesE. palustris subsp.palustris from Croatia, the Czech Republic, Germany, Italy, Israel, and Slovenia, and from 18 localities ofE. palustris subsp.vulgaris from the Czech Republic, Germany and Sweden are included. InE. palustris subsp.palustris, 2n=16 prevailed, the mixoploid 2n=15, 16 was rare and a lone hypoploid 2n=15 was detected. InE. palustris subsp.vulgaris 2n=38 was most frequently detected, the hyperploid 2n=39 and mixoploid 2n=38, 39 were common, and the hypoploid 2n=36 and mixoploids in which 2n ranges from 36 to 42 were rarer. Distribution maps based on plants investigated either by chromosome counting or by flow cytometry, augmented by similar data from published sources are given for both subspecies in Europe.

Hieracium subgen. Pilosella: pollen stainability in sexual, apomictic and sterile plants

Two pollen stainability tests (Alexander’s stain and acetocarmine) were used to detect differences in pollen viability of the sexual, apomictic and sterile plants of Hieracium subgen. Pilosella. In sexual taxa (Hieracium bauhini and H. densiflorum), the average stainability was 93.7–98.4%. Similarly high stainability (92.2–97.2%) was found in the apomictic Hieracium pilosellinum and in the majority of the apomictic populations (or plants) of the pentaploid and hexaploid H. bauhini. In some apomictic plants of Hieracium bauhini the average pollen stainability was 49.0–75.4%. The lowest pollen stainability was found in the sterile plants, i.e. the triploid H. pistoriense (33.6%) and the pentaploid H. brachiatum (29.6%).

The Detection, Rate and Manifestation of Residual Sexuality in Apomictic Populations of Pilosella (Asteraceae, Lactuceae)

The effect of maternal, facultatively apomictic plants on population diversity was evaluated in seven hybridizing polyploid Pilosella populations, where apomictic (P. bauhini or P. aurantiaca) and sexual (P. officinarum) biotypes coexist. The ploidy level, reproductive system, morphology, clonal structure and chloroplast DNA haplotypes were used to characterize these plants and their hybrids. The reproductive origins of the progeny were assessed through either a flow cytometric seed screen and/or a comparison between the ploidy level of progeny embryos/seedlings and the maternal ploidy level. The cultivated progeny derived from residual sexuality in maternal apomicts were also identified based on their morphology and reproductive behaviour. The progeny different from their maternal parents (0.6−92.3 % of progeny embryos and 0−100 % of progeny seedlings) originated either sexually or via haploid parthenogenesis. Comparing the facultatively apomictic and sexual mothers, the progeny arrays generated in the field showed that apomictic mothers produce progeny that is more variable in ploidy level. This effect was demonstrated at both the embryonic and seedling stages of progeny development. Residual sexuality in apomicts was also effective in experimental crosses, generating progeny similar to spontaneous hybrids in the field. The 2n + n hybrids produced from an apomictic and a sexual parent displayed similar reproductive behaviour, producing polyhaploid, sexual and apomictic progeny in variable ratios. Repeated hybridizations between parental species and/or multi-step crosses can result in hybrid swarms rich in cytotypes and morphotypes. The variation recorded in these populations suggests prevailing introgressive hybridization towards the sexual species P. officinarum.

Estimating paternal efficiency in an agamic polyploid complex: pollen stainability and variation in pollen size related to reproduction mode, ploidy level and hybridogenous origin in Pilosella (Asteraceae)

Pollen quality was evaluated in Pilosella plants sourced from the field and representing various cytotypes (diploid to octoploid), reproduction modes (sexuality, facultative apomixis and seed sterility or semisterility) and status of origin (basic species, hybridogenous intermediate species and recent hybrids). Two methods of non-vital pollen staining were compared, providing a similar pattern of variation in pollen stainability and pollen size. A complex influence of ploidy level, reproduction mode and plant origin on pollen quality was found. Sexual biotypes had high and equable pollen stainability whereas apomictic and (semi)sterile plants were more variable in this trait. Nevertheless, the sexual, apomictic and (semi)sterile plants did not significantly differ in pollen stainability, while the impacts of both ploidy level and plant origin were significant. Apomictic triploids had low pollen stainability and heterogeneously sized pollen, most likely resulting from disturbed meiosis. The other biotypes, including higher odd-ploid cytotypes, displayed various patterns of pollen quality partially depending on the hybridogenous origin. Whereas high pollen quality was detected in most of the apomictic hexaploids and heptaploids, including recent hybrids, serious pollen dysfunction was found in most octoploids. Seed (semi)sterility was not strongly associated with reduced pollen quality. Either blocked or unstable pollen production was occasionally recorded, predominantly among recent hybrids. Despite autonomous apomixis independent of pollen, most apomictic biotypes displayed fairly high pollen stainability and pollen size homogeneity, implying sufficient production of viable reduced pollen. Most representatives of this agamic polyploid complex, including facultative apomicts, might efficiently mate as both male and female parents in natural populations.

Na pomoc pedagogické praxi

Publikace pomaha budoucim a zacinajicim středoskolským ucitelům hledat odpovědi na otazky, s nimiž je konfrontuje výkon pedagogicke profese. V prvni kapitole popisujeme inovace ucitelských studijni ch programů na Přirodovědecke fakultě Masarykovy univerzity. Dale se věnujeme naslechům i výstupům pedagogicke praxe v ramci VS studia. V kapitole třeti se dělime o zkusenosti s reflexivni analýzou pedagogicke praxe s využitim virtualnich hospitaci a videozaznamů pedagogických praxi. Nasleduje kapitola postřehů vysokoskolských studentů – absolventů pedagogicke praxe. Dale se věnujeme zacatku profesni drahy ucitele a problematice provozu skoly, ale i specifikům ucitelstvi biologie, fyziky, chemie, geografie a matematiky. Přilohy obsahuji pozorovaci schema, klasifikacni a jine archy.