Variation In DNA Content Research Articles

A comparison of genetic stability in tea [Camellia sinensis (L.) Kuntze] plantlets derived from callus with plantlets from long-term in vitro propagation

Morphological variation, genotypic stability and genetic distances among micropropagated tea [Camellia sinensis (L.) Kuntze] cv. ‘Kolkhida’ plantlets after 7 years of propagation in vitro and among plantlets regenerated from callus were compared. Fifteen individuals, randomly chosen amongst a set of 100 plantlets regenerated from callus, and ten individuals, randomly chosen from a set of 100 micropropagated plants were used in the study. Morphological descriptors showed higher variability among callus-derived regenerants than in micropropagated plants. Flow cytometry analysis showed no significant variability of nuclear DNA content among micropropagated plants, however changes in DNA indicated aneuploidy in three out of ten callus-derived regenerants. ISSR analysis showed lesser genetic distances among micropropagated plantlets and maternal cultivar ‘Kolkhida’ compared with callus derived plantlets. Yet, there is some degree of genetic instability after long-term micropropagation. Results confirmed the hypothesis of genetic instability of some species during long term in vitro conservation. Tea vegetative explants plants were propagated in vitro for 7 years. A comparison of tea plantlets derived from callus with plantlets from long-term in vitro propagation revealed genetic variability and confirmed the hypothesis of genotype instability of tea plant.

Small, but surprisingly repetitive genomes: transposon expansion and not polyploidy has driven a doubling in genome size in a metazoan species complex

BackgroundThe causes and consequences of genome size variation across Eukaryotes, which spans five orders of magnitude, have been hotly debated since before the advent of genome sequencing. Previous studies have mostly examined variation among larger taxonomic units (e.g., orders, or genera), while comparisons among closely related species are rare. Rotifers of the Brachionus plicatilis species complex exhibit a seven-fold variation in genome size and thus represent a unique opportunity to study such changes on a relatively short evolutionary timescale. Here, we sequenced and analysed the genomes of four species of this complex with nuclear DNA contents spanning 110–422 Mbp. To establish the likely mechanisms of genome size change, we analysed both sequencing read libraries and assemblies for signatures of polyploidy and repetitive element content. We also compared these genomes to that of B. calyciflorus, the closest relative with a sequenced genome (293 Mbp nuclear DNA content).ResultsDespite the very large differences in genome size, we saw no evidence of ploidy level changes across the B. plicatilis complex. However, repetitive element content explained a large portion of genome size variation (at least 54%). The species with the largest genome, B. asplanchnoidis, has a strikingly high 44% repetitive element content, while the smaller B. plicatilis genomes contain between 14 and 25% repetitive elements. According to our analyses, the B. calyciflorus genome contains 39% repetitive elements, which is substantially higher than previously reported (21%), and suggests that high repetitive element load could be widespread in monogonont rotifers.ConclusionsEven though the genome sizes of these species are at the low end of the metazoan spectrum, their genomes contain substantial amounts of repetitive elements. Polyploidy does not appear to play a role in genome size variations in these species, and these variations can be mostly explained by changes in repetitive element content. This contradicts the naïve expectation that small genomes are streamlined, or less complex, and that large variations in nuclear DNA content between closely related species are due to polyploidy.

First report of genome size and ploidy of the underutilized leguminous tuber crop Yam Bean (Pachyrhizus erosus and P. tuberosus) by flow cytometry

AbstractCytological understanding is an important parameter to understand the genetic architecture of yam bean. The ploidy level and genome size of two cultivated species of yam bean (Pachyrhizus erosus and P. tuberosus) were estimated using flow cytometric analysis of young leaf tissue, with propidium iodide as a fluorescent dye. Six genotypes of P. erosus and three genotypes of P. tuberosus were analysed. Rice (Oryza sativa cv. Nipponbare) and Mung bean (Vigna radiata cv Berken) were used as internal reference standards. Variation of 2C nuclear DNA content among the six P. erousus lines was 4.18%, ranging from 1.17 to 1.22 pg, whereas only 1.8% variation was observed among the three P. tuberosus lines, which ranged from 1.07 to 1.09 pg. Moreover, it was found that the nuclear DNA content of P. tuberosus was lower than that of P. erosus. The result of the flow cytometric analysis showed that all the species were diploid (2n = 2x) and coefficient of variation (CV%) of all the accessions of the two species was less than 3.5%. This is the first report of ploidy analysis and genome size estimation of the leguminous underutilized tuber crop yam bean using flow cytometry. This result will be helpful for yam bean genome sequencing and crop improvement programmes.

FTIR and Raman Spectroscopy-Based Biochemical Profiling Reflects Genomic Diversity of Clinical Candida Isolates That May Be Useful for Diagnosis and Targeted Therapy of Candidiasis.

Despite the fact that Candida albicans is documented to be the main cause of human candidiasis, non-C. albicans Candida (NCAC) species, such as Candida glabrata and Candida tropicalis, are also suggested to be implicated in the etiopathogenesis of opportunistic fungal infections. As biology, epidemiology, pathogenicity, and antifungal resistance of NCAC species may be affected as a result of genomic diversity and plasticity, rapid and unambiguous identification of Candida species in clinical samples is essential for proper diagnosis and therapy. In the present study, 25 clinical isolates of C. albicans, C. glabrata, and C. tropicalis species were characterized in terms of their karyotype patterns, DNA content, and biochemical features. Fourier transform infrared (FTIR) spectra- and Raman spectra-based molecular fingerprints corresponded to the diversity of chromosomal traits and DNA levels that provided correct species identification. Moreover, Raman spectroscopy was documented to be useful for the evaluation of ergosterol content that may be associated with azole resistance. Taken together, we found that vibrational spectroscopy-based biochemical profiling reflects the variability of chromosome patterns and DNA content of clinical Candida species isolates and may facilitate the diagnosis and targeted therapy of candidiasis.

Cytogenetic and agronomic characterization of intergeneric hybrids between Saccharum spp. hybrid and Erianthus arundinaceus

In sugarcane (Saccharum spp. hybrid) breeding, introgression of useful genes via intergeneric hybridization is a powerful strategy for improving the crop productivity. Erianthus arundinaceus shows great potential in terms of useful traits; however, little is known about the cytogenetic and agronomic characteristics of intergeneric hybrids between these two species. Here, we examine the cytogenetic and agronomic characteristics, and relationships between the two in intergeneric F1 hybrids between modern sugarcane cultivar and E. arundinaceus identified by amplification of 5S rDNA markers and morphological characteristics. The nuclear DNA content of the hybrids varied from 6.07 to 8.94 pg/2C, with intra-clonal variation in DNA content and 5S rDNA sites. Genomic in situ hybridization revealed 53 to 82 chromosomes in the hybrids, with 53 to 56 derived from sugarcane and 1 to 29 from E. arundinaceus. There were significant positive correlations between the number of E. arundinaceus chromosomes and dry matter yield, millable stalk weight, single stalk weight, and stalk diameter, but not sucrose content, reducing sugar content, sucrose/reducing sugar ratio or fiber content. This detailed information on intergeneric F1 hybrids between modern sugarcane cultivar and E. arundinaceus will contribute to effective utilization of E. arundinaceus in sugarcane breeding.

A functional ex vivo assay to detect PARP1-EJ repair and radiosensitization by PARP-inhibitor in prostate cancer.

Here, we present a functional assay to detect the repair switch to the alternative PARP1-dependent end joining (PARP1-EJ) pathway and the associated susceptibility to PARPi-mediated radiosensitization in freshly collected tumor samples from prostate cancer (PCa) patients, thereby facilitating the selection of patients who should benefit from combined PARPi plus radiotherapy (RT) treatment. Our optimized ex-vivo approach sustains tumor slices for up to 15 days under culture conditions that maintain proliferation and oxygenation rates, as measured by EdU incorporation and pimonidazole staining, respectively. We present a robust system to analyze DSB repair using, for the first time in an ex vivo tumor slice setting, two DSB-markers simultaneously i.e. γH2AX and 53BP1. A computer-based processing method (i) controls variations in DNA content and slicing on the number of repair foci and (ii) measures the PARPi-mediated enhancement ratio on DSB foci numbers to ensure inter-patient-comparability. We validated this approach using a PC3 xenograft model with its previously described repair switch to PARP1-EJ. More importantly, we show that approximately 30% of the analyzed tumor tissue samples collected from PCa patients display a switch to PARP1-EJ, as indicated by the enhanced number of residual γH2AX/53BP1 foci exclusively after PARPi+RT. Furthermore, normal prostatic tissues show no repair switch to PARP1-EJ, indicating that this repair switch and its associated radiosensitizing effect is tumor-specific. Collectively, we present here a predictive assay for the switch to PARP1-EJ that enables individualization of anti-cancer treatment using a combination of RT and radiosensitizing anticancer agents such as PARPi in PCa.

Genome size analysis of field grown and tissue culture regenerated Rauvolfia serpentina (L) by flow cytometry: Histology and scanning electron microscopic study for in vitro morphogenesis

An efficient genetically stable regeneration protocol has been established in Rauvolfia serpentina (L) Benth ex. Kurz, an important medicinal plant, used for the treatment of various cardiovascular diseases. Here, in this present study, plants were regenerated through organogenesis (direct and indirect) and embryogenesis pathways. This is the first ever somatic embryo formation report of R. serpentina in liquid Murashige and Skoog (MS) medium from isolated root segments. The genetic fidelity of the regenerated plants was also analysed by flow cytometry. The 2C DNA content of the regenerated plants raised through organogenesis and somatic embryogenesis was measured along with field grown natural plants, which served as donor plant. The estimated 2C DNA levels are 2.08, 1.76 and 1.88 pg in direct, indirect and somatic embryo regenerated plants respectively while in field grown plant it was noted to be 1.94 pg in R. serpentina. This is perhaps the first ever 2C DNA estimation study in tissue culture raised plants along with natural population of Rauvolfia, an immensely important medicinal plant, present in India. We developed improved callus mediated shoot regeneration (indirect) protocol from leaf callus. Highest shoot regeneration percentage (66.10%) with 4.0 shoots / callus mass was noted on 2.0 mg l−1 BAP + 0.5 mg l−1 NAA added MS medium. The shoot tips and nodal explants on 2.5 mg l−1 BAP amended MS medium induced direct shoot buds, with highest shoot regeneration frequency (81.45%) from shoot tips. On 1.0 mg l−1NAA added MS medium maximum numbers of roots (8.87) were noted, indicating the effectiveness of NAA over IBA in rooting. Excised roots were cultured in agitated liquid MS medium and in 1.0 mg l−1 NAA added conditions somatic embryos were formed. The mature somatic embryos germinated on 1.5 mg l−1 BAP + 0.25 mg l−1 GA3 supplemented MS medium. The histology and scanning electron microscopic (SEM) evidences have been presented to describe the in vitro morphogenesis process. The well-rooted plantlets were acclimatized and transferred to soil successfully (79%). The flow cytometric analysis showed no significant variation in nuclear DNA contents, hence was observed to be genetically stable with their genome size similar to field grown Rauvolfia plants.

Nuclear DNA content variation of herbaceous angiosperm species on 10 global latitudinal transects1,2

Many studies have examined variation in nuclear DNA content across environmental gradients. However, these studies have often produced conflicting results. We speculated that the conflicting phenomenon resulted from insufficient sampling of the taxa and limitations in the geographical range. To clarify whether the relationships between nuclear DNA content and environmental gradients are universally nonlinear across a wide geographical range, we chose 3,290 herbaceous angiosperm species, which have both nuclear DNA values in the Angiosperm DNA C-values database and geographical distribution information in the Global Biodiversity Information Facility (GBIF) database. Then we selected 10 global longitudinal transects each with a span of 15°, and evenly divided each transect (from 82.5°N to 82.5°S) into 22 blocks. We obtained geographical records (presence or absence) of these 3,290 species together with 14 bioclimatic factors within these blocks, and calculated the average DNA 1C-values and genome sizes of the species in each block. By using polynomial functions, we analyzed the correlation of nuclear DNA values with latitude. By using the Gaussian model, we further analyzed the correlation of nuclear DNA values with the 14 bioclimatic factors. Finally, we also performed quantile regression analyses to elucidate the differences in geographical distribution pattern among groups with nuclear DNA values of different sizes. We found that species in equatorial areas had the smallest mean nuclear DNA values, the values increased with latitude for both the northern and southern hemispheres following nonlinear functions. We found that nuclear DNA contents decreased with increasing latitude in the Arctic. The change of nuclear DNA content with latitude was weaker in the species groups with smaller nuclear DNA content than those with a larger nuclear DNA content. Nonlinear relationships (following Gaussian models) also existed between nuclear DNA values and the 14 bioclimatic factors, such as annual precipitation and mean temperature. Therefore, the relationships of nuclear DNA content with either latitude or the 14 bioclimatic factors covarying with latitude are universally nonlinear across a global geographical gradient. Nuclear DNA contents are of ecological significance for angiosperms. There exist obvious differences in the geographical distribution patterns among species groups with nuclear DNA values of different sizes, with a selective advantage for species with small nuclear DNA content in extreme environments.

B Chromosomes of the Asian Seabass (Lates calcarifer) Contribute to Genome Variations at the Level of Individuals and Populations.

The Asian seabass (Lates calcarifer) is a bony fish from the Latidae family, which is widely distributed in the tropical Indo-West Pacific region. The karyotype of the Asian seabass contains 24 pairs of A chromosomes and a variable number of AT- and GC-rich B chromosomes (Bchrs or Bs). Dot-like shaped and nucleolus-associated AT-rich Bs were microdissected and sequenced earlier. Here we analyzed DNA fragments from Bs to determine their repeat and gene contents using the Asian seabass genome as a reference. Fragments of 75 genes, including an 18S rRNA gene, were found in the Bs; repeats represented 2% of the Bchr assembly. The 18S rDNA of the standard genome and Bs were similar and enriched with fragments of transposable elements. A higher nuclei DNA content in the male gonad and somatic tissue, compared to the female gonad, was demonstrated by flow cytometry. This variation in DNA content could be associated with the intra-individual variation in the number of Bs. A comparison between the copy number variation among the B-related fragments from whole genome resequencing data of Asian seabass individuals identified similar profiles between those from the South-East Asian/Philippines and Indian region but not the Australian ones. Our results suggest that Bs might cause variations in the genome among the individuals and populations of Asian seabass. A personalized copy number approach for segmental duplication detection offers a suitable tool for population-level analysis across specimens with low coverage genome sequencing.

Estimation of nuclear DNA content and its variation among Indian Tea accessions by flow cytometry.

Nuclear DNA content and genome size variation among 36 Indian tea accessions were analyzed by flow cytometry. Initial standardization of protocols for isolation of nuclei, DNA staining and selection of an internal standard for tea accessions which have significantly high amount of phenolic secondary metabolites in their cytosol was carried out. Results obtained revealed that 2C DNA content of Indian tea is 7.46pg which correspondsto 1C genome size of 3673Mb. Inter accession variation in 2C DNA content was also observed among 35 diploid taxa ranging from 7.23 to 7.73pg which was significant at 1% probability level. The 2C DNA content of triploid (UPASI 3) was observed to be 11.47pg which is concurrent with the expected value. Results obtained showed that Assam and Cambod type tea accession have higher 2C DNA content of 7.73pg whereas Assam Cambod hybrids and Assam China hybrids have reduction in DNA content with 2C amounts, 7.23 and 7.32pg DNA respectively. The present study suggests that the species involved in origin of Indian tea must have differed in their genome sizes owing to significant inter accession variation in nuclear DNA content.

Genomic mosaicism in the developing and adult brain.

ABSTRACTSince the discovery of DNA, the normal developing and functioning brain has been assumed to be composed of cells with identical genomes, which remains the dominant view even today. However, this pervasive assumption is incorrect, as proven by increasing numbers of reports within the last 20 years that have identified multiple forms of somatically produced genomic mosaicism (GM), wherein brain cells—especially neurons—from a single individual show diverse alterations in DNA, distinct from the germline. Critically, these changes alter the actual DNA nucleotide sequences—in contrast to epigenetic mechanisms—and almost certainly contribute to the remarkably diverse phenotypes of single brain cells, including single‐cell transcriptomic profiles. Here, we review the history of GM within the normal brain, including its major forms, initiating mechanisms, and possible functions. GM forms include aneuploidies and aneusomies, smaller copy number variations (CNVs), long interspersed nuclear element type 1 (LINE1) repeat elements, and single nucleotide variations (SNVs), as well as DNA content variation (DCV) that reflects all forms of GM with greatest coverage of large, brain cell populations. In addition, technical considerations are examined, along with relationships among GM forms and multiple brain diseases. GM affecting genes and loci within the brain contrast with current neural discovery approaches that rely on sequencing nonbrain DNA (e.g., genome‐wide association studies (GWAS)). Increasing knowledge of neural GM has implications for mechanisms of development, diversity, and function, as well as understanding diseases, particularly considering the overwhelming prevalence of sporadic brain diseases that are unlinked to germline mutations. © 2018 The Authors. Developmental Neurobiology Published by Wiley Periodicals, Inc. Develop Neurobiol, 2018

Molecular Reconstruction of an Old Pedigree of Diploid and Triploid Hydrangea macrophylla Genotypes.

The ornamental crop species Hydrangea macrophylla exhibits diploid and triploid levels of ploidy and develops lacecap (wild type) or mophead inflorescences. In order to characterize a H. macrophylla germplasm collection, we determined the inflorescence type and the 2C DNA content of 120 plants representing 43 cultivars. We identified 78 putative diploid and 39 putative triploid plants by flow cytometry. In our collection 69 out of 98 flowering plants produced lacecap inflorescences, whereas 29 plants developed mophead inflorescences. Surprisingly, 12 cultivars included diploid as well as triploid plants, while 5 cultivars contained plants with different inflorescence types. We genotyped this germplasm collection using 12 SSR markers that detected 2–7 alleles per marker, and identified 51 different alleles in this collection. We detected 62 distinct fingerprints, revealing a higher genetic variation than the number of cultivars suggested. Only one genotype per cultivar is expected due to the vegetative propagation of Hydrangea cultivars; however we identified 25 cultivars containing 2–4 different genotypes. These different genotypes explained the variation in DNA content and inflorescence type. Diploid and triploid plants with the same cultivar name were exclusively mix-ups. We therefor assume, that 36% of the tested plants were mislabeled. Based on the “Wädenswil” pedigree, which includes 31 of the tested cultivars, we predicted cultivar-specific fingerprints and identified at least 21 out of 31 cultivars by SSR marker-based reconstruction of the “Wädenswil” pedigree. Furthermore, we detected 4 putative interploid crosses between diploid and triploid plants in this pedigree. These interploid crosses resulted in diploid or/and triploid offspring, suggesting that crosses with triploids were successfully applied in breeding of H. macrophylla.

Karyotype diversity and 2C DNA content in species of the Caesalpinia group

BackgroundThe Leguminosae family is the third-largest family of angiosperms, and Caesalpinioideae is its second-largest subfamily. A great number of species (approximately 205) are found in the Caesalpinia group within this subfamily; together with these species’ phenotypic plasticity and the similarities in their morphological descriptors, make this a complex group for taxonomic and phylogenetic studies. The objective of the present work was to evaluate the karyotypic diversity and the 2C DNA content variation in 10 species of the Caesalpinia group, representing six genera: Paubrasilia, Caesalpinia, Cenostigma, Poincianella, Erythrostemon and Libidibia. The GC-rich heterochromatin and 45S rDNA sites (which are used as chromosome markers) were located to evaluate the karyotype diversity in the clade. The variation in the 2C DNA content was determined through flow cytometry.ResultsThe fluorochrome banding indicated that the chromomycin A3+/4′,6-diamidino-2-phenylindole− blocks were exclusively in the terminal regions of the chromosomes, coinciding with 45S rDNA sites in all analyzed species. Physical mapping of the species (through fluorescence in situ hybridization) revealed variation in the size of the hybridization signals and in the number and distribution of the 45S rDNA sites. All hybridization sites were in the terminal regions of the chromosomes. In addition, all species had a hybridization site in the fourth chromosome pair. The 2C DNA content ranged from 1.54 pg in Erythrostemon calycina to 2.82 pg in the Paubrasilia echinata large-leaf variant. The Pa. echinata small-leaf variant was isolated from the other leaf variants through Scoot-Knott clustering.ConclusionsThe chromosome diversity and the variation in the 2C DNA content reinforce that the actual taxonomy and clustering of the analyzed taxa requires more genera that were previously proposed. This fact indicates that taxonomy, phylogeny and cytoevolutionary inference related to the complex Caesalpinia group have to be done through integrative evaluation.

Genome size and ploidy level among wild and cultivated Prunus taxa in Slovakia

2C DNA content and ploidy level variation of Prunus spinosa and closely related taxa together with Prunus domestica L. and Prunus insititia L. was studied in Slovakia. The aim of the study was to define genome sizes and find differences between closely related taxa within Prunus spinosa sensu lato mentioned in previous works. According to our results, investigated taxa can be divided into three groups according to ploidy level: Prunus spinosa, Prunus dasyphylla, Prunus ×fruticans, Prunus ×dominii and Prunus ×schurii are tetraploids, Prunus ×fechtneri is pentaploid, and P. domestica and P. insititia are hexaploids. Genome size differences within tetraploid taxa were relatively small (Prunus spinosa: 1.40 ± 0.02, P. ×domini: 1.44 ± 0.01, P. ×fruticans: 1.48 ± 0.02, P. ×schurii: 1.44 ± 0.02), but statistically significant. Although further research is needed, it seems that the concept of several taxa as product of hybridization between P. spinosa and cultivated plum species has been supported by our study.

Variation in nuclear DNA content and chromosome numbers in blueberry

Abstract Commercial blueberry production in the U.S. relies on cultivars derived from combinations of different blueberry species. Interspecific hybridization continues to be a vital strategy for blueberry breeding, especially in regards to improving abiotic and biotic stress tolerance to expand the range of production. Blueberry species have many different genome sizes, presumably due to differing ploidy levels and/or DNA content. In some species, such as Vaccinium corymbosum L. and V. pallidum Aiton, there are also different ploidy series available for breeding, further complicating the observed DNA content in elite selections. In this study we determined DNA content in 77 blueberry taxa including 11 species and 64 hybrid cultivars. Among these taxa are 11 diploid, 49 tetraploid, one pentaploid, and 16 hexaploid plants representing southern highbush, northern highbush, low bush, rabitteye, and half high blueberries. DNA content was measured for three separate tissue samples from at least three individual plants per taxa for accuracy. Absolute genome sizes varied significantly (P = 0.05) among ploidy levels, with 2C-value means of 1.09 pg for diploid, 2.10 pg for tetraploid, and 3.60 pg for hexaploid taxa. Holoploid genome size (2C DNA) was significantly correlated with ploidy or presumed chromosome number (2n) (r = 0.96, P = 0.0001) but only weakly correlated with monoploid genome size (1Cx-DNA) (r = 0.43, P = 0.0001).

Aneuploidy, TP53 mutation, and amplification of MYC correlate with increased intratumor heterogeneity and poor prognosis of breast cancer patients.

The clinical course of breast cancer varies from one patient to another. Currently, the choice of therapy relies on clinical parameters and histological and molecular tumor features. Alas, these markers are informative in only a subset of patients. Therefore, additional predictors of disease outcome would be valuable for treatment stratification. Extensive studies showed that the degree of variation of the nuclear DNA content, i.e., aneuploidy, determines prognosis. Our aim was to further elucidate the molecular basis of aneuploidy. We analyzed five diploid and six aneuploid tumors with more than 20 years of follow-up. By performing FISH with a multiplexed panel of 10 probes to enumerate copy numbers in individual cells, and by sequencing 563 cancer-related genes, we analyzed how aneuploidy is linked to intratumor heterogeneity. In our cohort, none of the patients with diploid tumors died of breast cancer during follow-up in contrast to four of six patients with aneuploid tumors (mean survival 86.4 months). The FISH analysis showed markedly increased genomic instability and intratumor heterogeneity in aneuploid tumors. MYC gain was observed in only 20% of the diploid cancers, while all aneuploid cases showed a gain. The mutation burden was similar in diploid and aneuploid tumors, however, TP53 mutations were not observed in diploid tumors, but in all aneuploid tumors in our collective. We conclude that quantitative measurements of intratumor heterogeneity by multiplex FISH, detection of MYC amplification and TP53 mutation could augment prognostication in breast cancer patients.

Updating the maize karyotype by chromosome DNA sizing.

The karyotype is a basic concept regarding the genome, fundamentally described by the number and morphological features of all chromosomes. Chromosome class, centromeric index, intra- and interchromosomal asymmetry index, and constriction localization are important in clinical, systematic and evolutionary approaches. In spite of the advances in karyotype characterization made over the last years, new data about the chromosomes can be generated from quantitative methods, such as image cytometry. Therefore, using Zea mays L., this study aimed to update the species’ karyotype by supplementing information on chromosome DNA sizing. After adjustment of the procedures, chromosome morphometry and class as well as knob localization enabled describing the Z. mays karyotype. In addition, applying image cytometry, DNA sizing was unprecedentedly measured for the arms and satellite of all chromosomes. This way, unambiguous identification of the chromosome pairs, and hence the assembly of 51 karyograms, were only possible after the DNA sizing of each chromosome, their arms and satellite portions. These accurate, quantitative and reproducible data also enabled determining the distribution and variation of DNA content in each chromosome. From this, a correlation between DNA amount and total chromosome length evidenced that the mean DNA content of chromosome 9 was higher than that of chromosome 8. The chromosomal DNA sizing updated the Z. mays karyotype, providing insights into its dynamic genome with regards to the organization of the ten chromosomes and their respective portions. Considering the results and the relevance of cytogenetics in the current scenario of comparative sequencing and genomics, chromosomal DNA sizing should be incorporated as an additional parameter for karyotype definition. Based on this study, it can be affirmed that cytogenetic approaches go beyond the simple morphological description of chromosomes.

Variation of nuclear DNA content in seeds of Nitraria schoberi L.

For the first time are search of nuclear DNA relative content in Nitraria schoberi L. seeds from 15 natural populations of Siberia, the Crimea, Kazakhstan, and Tajikistan has been conducted by the method of flow cytometry. High intra-and interpopulational variations of nuclear DNA content - 2,93-3,39 pg, at average value - 3,22±0,108 pg is revealed.

Cytological and genome size data analyzed in a phylogenetic frame: Evolutionary implications concerning Sisyrinchium taxa (Iridaceae: Iridoideae).

Sisyrinchium is the largest genus of Iridaceae in the Americas and has the greatest amount of cytological data available. This study aimed at investigating how genomes evolved in this genus. Chromosome number, genome size and altitude from species of sect. Viperella were analyzed in a phylogenetic context. Meiotic and pollen analyses were performed to assess reproductive success of natural populations, especially from those polyploid taxa. Character optimizations revealed that the common ancestor of sect. Viperella was probably diploid (2n = 2x =18) with two subsequent polyplodization events. Total DNA content (2C) varied considerably across the phylogeny with larger genomes detected mainly in polyploid species. Altitude also varied across the phylogeny, however no significant relationship was found between DNA content changes and altitude in our data set. All taxa presented regular meiosis and pollen viability (> 87%), except for S. sp. nov. aff. alatum (22.70%), suggesting a recent hybrid origin. Chromosome number is mostly constant within this section and polyploidy is the only source of modification. Although 2C varied considerably among the 20 taxa investigated, the diversity observed cannot be attributed only to polyploidy events because large variations of DNA content were also observed among diploids.

Extensive analysis of native and non-native Centaurea solstitialis L. populations across the world shows no traces of polyploidization.

Centaurea solstitialis L. (yellow starthistle, Asteraceae) is a Eurasian native plant introduced as an exotic into North and South America, and Australia, where it is regarded as a noxious invasive. Changes in ploidy level have been found to be responsible for numerous plant biological invasions, as they are involved in trait shifts critical to invasive success, like increased growth rate and biomass, longer life-span, or polycarpy. C. solstitialis had been reported to be diploid (2n = 2x = 16 chromosomes), however, actual data are scarce and sometimes contradictory. We determined for the first time the absolute nuclear DNA content by flow cytometry and estimated ploidy level in 52 natural populations of C. solstitialis across its native and non-native ranges, around the world. All the C. solstitialis populations screened were found to be homogeneously diploid (average 2C value of 1.72 pg, SD = ±0.06 pg), with no significant variation in DNA content between invasive and non-invasive genotypes. We did not find any meaningful difference among the extensive number of native and non-native C. solstitialis populations sampled around the globe, indicating that the species invasive success is not due to changes in genome size or ploidy level.