DNA C-values Research Articles

Genome Size Variation across a Cypriot Fabeae Tribe Germplasm Collection.

DNA content is an important trait linked to the evolutionary routes of taxa and often connected to speciation. In the present study, we studied C-values variation across the Cypriot Fabeae gene pool. Several hundred plants (Vicia spp., Lens spp., Pisum spp.) were sampled across Cyprus. Accurate estimates were established by flow cytometry and propidium iodine staining for 155 discrete populations/accessions. A ten-fold variation was detected across lineages with 1C DNA content varying from 1.584 pg for V. cretica (ARI02420) to 13.983 pg for V. faba (ARI00187). In general, flow cytometry was precise for the characterization of species, even though there were instances of genome overlapping across taxa. Most analyses in the current work refer to species that have not been characterized before by flow cytometry (or any other DNA content estimation method). Still, a correlation to C-values previously reported in Kew Plant DNA C-values database was attempted. A high degree of correlation except for V. dalmatica was established. The evaluation of genome size trait in relation with the Fabeae phylogeny, revealed that Pisum and Lens genera were rather homogenous, but an astonishing fluctuation was shown for Vicia spp. Moreover, it was established that genome up- or down-scaling was not directly linked to speciation drivers. The genomic size measurements presented here could deliver extra quality control for the identification and characterization of taxa in germplasm collections, particularly in cases where species share morphological characters.

Morphological, cariological, and phytochemical studies of diploid and autotetraploid Hippeastrum papilio plants

The polyploidization of Hippeastrum papilio influences its primary and secondary metabolism including the biosynthesis of bioactive alkaloids. Hippeastrum papilio is an ornamental plant that has advantages in comparison to the currently used plants for the extraction of galanthamine, a natural compound used for the cognitive treatment of Alzheimer's disease. In the present study, an autotetraploid line of H. papilio was induced for the first time, after treatment with 0.05% colchicine for 48h. The chromosome number in diploids was found to be 2n = 2x = 22 and for autotetraploids 2n = 4x = 44. The flow cytometric analyses detected a DNA C-value of 14.88 ± 0.03pg (1C) in diploids and 26.57 ± 0.12pg in autotetraploids. The morphological, cytological, and phytochemical studies showed significant differences between diploids and autotetraploids. The length and width of stomata in autotetraploids were 22.47% and 17.94%, respectively, larger than those observed in the diploid leaves. The biomass of one-year-old autotetraploid H. papilio plants was reduced by 53.99% for plants' fresh weight, 56.53% for leaves' fresh weight, and 21.70% for bulb diameter. The GC-MS analysis of methanol extracts from one-year-old diploid and autotetraploid H. papilio plants revealed over 60 primary and secondary metabolites including alkaloids, phenolic acids, sterols, saccharides, and alcohols, among others. Principal component analysis of the metabolite profiles indicates a divergence of the metabolism between diploid and autotetraploid plants. The content of galanthamine and haemanthamine was found to be 49.73% and 80.10%, respectively, higher in the leaves of autotetraploids, compared to the diploid ones. The biosynthesis of the saccharides shows a tendency to be upregulated in tetraploid plants, while that of phenolic acids was downregulated. Polyploidization of H. papilio creates possibilities for further crop improvement aimed at high-galanthamine-producing genotypes.

The Plant DNA C-Values Database: A One-Stop Shop for Plant Genome Size Data.

Genome size is a plant character with far-reaching implications, ranging from impacts on the financial and computing feasibility of sequencing and assembling genomes all the way to influencing the very ecology and evolution of species. The increasing recognition of the role of genome size in plant science has led to a rising demand for comprehensive and easily accessible sources of genome size data. The Plant DNA C-values database has established itself as a trusted and widely used central hub for users needing to access available plant genome size data, complemented with related cytogenetic (ploidy level) and karyological (chromosome number) information where available. Since its inception in 2001, the database has undergone six major updates to incorporate newly available genome size information, leading to the most recent release (Release 7.1), which comprises data for 12,273 species across all the major land plant and some algal lineages. Here we describe how to use the database efficiently, making use of its different query and filtering settings.

CITOGENÉTICA DE PLANTAS TERRESTRES CHILENAS (EMBRYOPHYTA): ESTADO DEL ARTE Y PERSPECTIVAS

Chile is located in the south-western region of South America along the Pacific Ocean and contributes to the worldwide flora with ca. 6,120 species of Bryophyta, Pteridophyta, Pinophyta, Gnetophyta, and Magnoliophyta (1.9% of worldwide total species), exhibiting high endemism across all plant divisions. Little is known about the genetic diversity of Chilean land plants worldwide, including their cytogenetic and molecular characteristics. In 2012 we published the first state-of-the-art review in Cytogenetics of Chilean Angiosperms. The article gathered 78 publications from 1924 to 2010 accounting for approximately 139 species (2.8% of total Chilean species). The aim of this paper was to review the advances in cytogenetic studies of Chilean land plants, reporting additional cytogenetic data for species of four botanical divisions until 2020. Cytogenetic data were searched in the CPCD (Chilean Plants Cytogenetic Database). In total, we found 180 publications from both Chilean and foreign researchers. To date, cytogenetic data have been reported for 499 Chilean land plant species (8.2% of total) belonging to 244 genera and 117 families. In this context, the 2001-2020 period has been among the most productive regarding publications, with 74 available reports that include 163 additional species. Based on chromosome numbers, angiosperms and bryophytes registered the greatest diversity with 55 and 29 different 2n, respectively; both divisions having the greatest number of studied species. Given the importance of increasing information on Chilean land plants, it is expected that more publications will contribute to the knowledge of their cytogenetic diversity in the near future. Key words: chromosome banding, chromosome number, DNA C-value, karyotype morphology, polyploidy.

Genome Size of Life Forms of Araceae-A New Piece in the C-Value Puzzle.

The genome size of an organism is an important trait that has predictive values applicable to various scientific fields, including ecology. The main source of plant C-values is the Plant DNA C-values database of the Royal Botanic Gardens Kew, which currently contains 12,273 estimates. However, it covers only 2.9% of known angiosperm species and has gaps in the life form and geographic distribution of plants. Only 4.5% of C-value estimates come from researchers in Central and South America. This study provides 41 new C-values for the aroid family (Araceae), collected in the Piedras Blancas National Park area in southern Costa Rica, including terrestrial, epiphytic and aquatic life forms. Data from our study are combined with C-value entries in the RBGK database for Araceae. The analysis reveals a wider range of C-values for terrestrial aroids, consistent with other terrestrial plants, a trend toward slightly lower C-values for epiphytic forms, which is more consistent for obligate epiphytes, and comparatively low C-values for aquatic aroids.

Evolution of genome space occupation in ferns: linking genome diversity and species richness.

The dynamics of genome evolution caused by whole genome duplications and other processes are hypothesized to shape the diversification of plants and thus contribute to the astonishing variation in species richness among the main lineages of land plants. Ferns, the second most species-rich lineage of land plants, are highly suitable to test this hypothesis because of several unique features that distinguish fern genomes from those of seed plants. In this study, we tested the hypothesis that genome diversity and disparity shape fern species diversity by recording several parameters related to genome size and chromosome number. We conducted de novo measurement of DNA C-values across the fern phylogeny to reconstruct the phylogenetic history of the genome space occupation in ferns by integrating genomic parameters such as genome size, chromosome number and average DNA amount per chromosome into a time-scaled phylogenetic framework. Using phylogenetic generalized least square methods, we determined correlations between chromosome number and genome size, species diversity and evolutionary rates of their transformation. The measurements of DNA C-values for 233 species more than doubled the taxon coverage from ~2.2 % in previous studies to 5.3 % of extant diversity. The dataset not only documented substantial differences in the accumulation of genomic diversity and disparity among the major lineages of ferns but also supported the predicted correlation between species diversity and the dynamics of genome evolution. Our results demonstrated substantial genome disparity among different groups of ferns and supported the prediction that alterations of reproductive modes alter trends of genome evolution. Finally, we recovered evidence for a close link between the dynamics of genome evolution and species diversity in ferns for the first time.

Cytogenetics of wild species of the Alstroemeriaceae family (Liliales)

Studies on cytogenetic diversity within the Alstroemeriaceae family along its intercontinental distribution are scarce when comparing species of their four genera. This study aimed at exploring the cytogenetic diversity of the family along their geographical distribution, including species that inhabit Oceania and South America. Using quantitative and qualitative methods, we analysed 50 species of the four genera (24% of the species of the family), comparing cytogenetic characters such as chromosome number, karyotype morphology and asymmetry, location of chromosome satellites, total haploid length, meiotic behaviour, C and FISH banding, and DNA C-values. We concur with other authors in that generic delimitation based on chromosome number is clear among Alstroemeria (2n = 16) and Bomarea (2n = 18), both belonging to Alstroemerioideae. Moreover, these two genera have different chromosome numbers compared to those of Luzuriaga and Drymophila (both 2n = 20) belonging to Luzuriagoideae. The above observations were also supported by the phylogeny reconstructed here. In addition, analyses on karyotype morphology and asymmetry have determined gradual differences in nuclear architecture among genera and species. We concluded that the cytogenetic diversity described within Alstroemeriaceae is concentrated mainly in South America, which is to be expected given the higher species diversity that has been described for that continent. Although the presence of three chromosome numbers within Alstroemeriaceae has no relation with their wide geographical distribution in two continents, an appreciable variation was observed in karyotype morphology and asymmetry, total haploid length and cytomolecular features when the species were compared along their geographical range.

State of the art in cytogenetics, insights into chromosome number evolution, and new C-value reports for the fern family Gleicheniaceae.

Studies concerning the cytogenetics of Gleicheniaceae have been scarce, especially those employing evolutionary approaches. Two chromosome number evolutionary models have been hypothesized for Gleicheniaceae. One proposes that ancestral haploid numbers were small and that the chromosome numbers of extant species evolved through polyploidy. The other model proposes that, at the genus level, fern chromosome evolution occurred from ancestors with essentially the same high chromosome numbers seen in living lineages. Neither of those hypotheses has been tested based on phylogenetic frameworks. We sought to (i) present the state of the art of Gleicheniaceae chromosome numbers; (ii) test the two evolutionary models of chromosome numbers within a phylogenetic framework; (iii) test correlations between DNA contents and chromosome numbers in the family. We report here DNA C-values for five species, which increases the number of investigated taxa nearly twofold and report two new genera records. Ancestral state chromosome reconstruction corroborates the hypothesis that ancestral chromosome numbers in Gleicheniaceae were as high as those of extant lineages. Our results demonstrate the possible role of dysploidy in the evolutionary chromosome history of Gleicheniaceae at the genus level and suggest that the relationship between chromosome number and DNA content does not appear to be linear.

Application of glycerol-preserved nuclei protocol for genome size estimation in the field conditions of a tropical rainforest

The extraordinary biodiversity of tropical regions has attracted many researchers. Despite an increasing number of genome size (GS) estimations, those of tropic flora remain poorly explored. In this study, we applied the glycerol-preserved nuclei protocol for GS estimation in the field conditions of a tropical rainforest in Brunei Darussalam, northern Borneo. Samples were prepared in the field following this protocol and subjected to the flow cytometry analysis in the laboratory approximately 1 month later. The glycerol-preserved nuclei protocol enabled us to perform GS estimations of thirty taxa of Euphorbiaceae s.l. (twenty taxa of Euphorbiaceae and ten taxa of Phyllanthaceae family, respectively), all representing first estimates of GS for respective taxa. We found 5.09-fold overall variation in GS, with the lowest value in Croton sp. (2C = 0.97 pg) and the highest value in Aporosa elmeri (2C = 4.94 pg). The vast majority of species presented very small GS (77%), while 23% of the species had small GS. Using available data of Euphorbiaceae s.l. from the Plant DNA C-values database, we also tested the correlations of GS with climate (tropical vs. temperate) and growth form (woody vs. herbaceous). Tropical taxa of Euphorbiaceae s.l. (incl. Euphorbiaceae s.s. and Phyllanthaceae) have significantly smaller GS values than temperate ones. No significant difference in GS between woody and herbaceous taxa was detected.

Allopolyploidy and genomic differentiation in holocentric species of the Eleocharis montana complex (Cyperaceae)

Polyploidy and hybridization are key events in plant evolution. Due to these events, complexes of species can be formed. Dysploidy, a frequent chromosome change in holocentric organisms, may add some difficulties to species delimitation, especially in Cyperaceae. The Eleocharis montana complex is known for its members with overlapping morpho-anatomical features and unclear circumscription. To understand its biological history, several tools were used to investigate different American populations, including morpho-anatomical analysis, genome size estimates, cytogenomic analysis, molecular marker characterization, and genomic in situ hybridization (GISH). Despite overlapping morphological features, it was possible to separate two groups, the first containing E. parodii and E. subarticulata, presenting diploid and dysploid karyotypes, respectively, and small DNA C-values. The second contained E. elegans, E. contracta, and E. montana, with large genomes created by polyploidy. All analyses suggest that E. montana with 2n = 40 is a cytotype of E. contracta with 2n = 20, and both evolved from a natural hybridization involving E. parodii (2n = 10) and a second progenitor that is yet unknown. Furthermore, the GISH results indicated that E. parodii may be an ancestor of E. elegans. All species occur in the probable center of diversification in Austral South America, where the hybridization zone is identified. Fieldwork and information obtained from herbaria indicate that diploid and dysploid species (E. subarticulata and E. parodii) do not occur beyond the center of diversification. However, E. elegans and specially E. montana occur more widely, occupying different flooded environments and landscapes.

Genome size estimation of 43 Korean <i>Carex</i>

The genome size is defined as the amount of DNA in an unreplicated gametic chromosome com­plement and is expressed as the 1C value. It is a fundamental parameter of organisms that is useful for studies of the genome, as well as biodiversity and conservation. The genome sizes of Korean plants, including Carex (Cyperaceae), have been poorly reported. In this study, we report the genome sizes of 43 species and infraspe­cific taxa of Korean Carex using flow cytometry, and these results represent about 24.4% of the Carex species and infraspecific taxa distributed on the Korean peninsula. The Plant DNA C-Value Database (release 7.1) updated with and now including our data (a total of 372 Carex accessions) shows that the average genome size of members of the Carex species is 0.47 pg (1C), and the largest genome (C. cuspidate Bertol.; 1C = 1.64 pg) is 8.2 times larger than the smallest (C. brownii Tuck., C. kobomugi Ohwi, C. nubigena D. Don ex Tilloch & Tay­lor, and C. paxii Kuk.; 1C = 0.20 pg). The large genomes are frequently found in the subgen. Carex, especially in sect. Aulocystis, sect. Digitatae, sect. Glaucae, sect. Paniceae, and sect. Siderostictae. Our data updates the current understanding of genome sizes in Carex. This will serve as the basis for understanding the phylogeny and evolution of Carex and will be especially useful for future genome studies.

Determination on DNA C-values of three Macromitrium species, with comments on biological significances of DNA C-values for bryological research

Determination on DNA C-values of three <i>Macromitrium</i> species, with comments on biological significances of DNA C-values for bryological research

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.

Analysis of retrotransposon abundance, diversity and distribution in holocentric Eleocharis (Cyperaceae) genomes.

Background and AimsLong terminal repeat-retrotransposons (LTR-RTs) comprise a large portion of plant genomes, with massive repeat blocks distributed across the chromosomes. Eleocharis species have holocentric chromosomes, and show a positive correlation between chromosome numbers and the amount of nuclear DNA. To evaluate the role of LTR-RTs in karyotype diversity in members of Eleocharis (subgenus Eleocharis), the occurrence and location of different members of the Copia and Gypsy superfamilies were compared, covering interspecific variations in ploidy levels (considering chromosome numbers), DNA C-values and chromosomal arrangements.MethodsThe DNA C-value was estimated by flow cytometry. Genomes of Eleocharis elegans and E. geniculata were partially sequenced using Illumina MiSeq assemblies, which were a source for searching for conserved proteins of LTR-RTs. POL domains were used for recognition, comparing families and for probe production, considering different families of Copia and Gypsy superfamilies. Probes were obtained by PCR and used in fluorescence in situ hybridization (FISH) against chromosomes of seven Eleocharis species.Key ResultsA positive correlation between ploidy levels and the amount of nuclear DNA was observed, but with significant variations between samples with the same ploidy levels, associated with repetitive DNA fractions. LTR-RTs were abundant in E. elegans and E. geniculata genomes, with a predominance of Copia Sirevirus and Gypsy Athila/Tat clades. FISH using LTR-RT probes exhibited scattered and clustered signals, but with differences in the chromosomal locations of Copia and Gypsy. The diversity in LTR-RT locations suggests that there is no typical chromosomal distribution pattern for retrotransposons in holocentric chromosomes, except the CRM family with signals distributed along chromatids.ConclusionsThese data indicate independent fates for each LTR-RT family, including accumulation between and within chromosomes and genomes. Differential activity and small changes in LTR-RTs suggest a secondary role in nuclear DNA variation, when compared with ploidy changes.

植物核DNA含量在全球尺度上的纬度变异式样及其气候适应意义——以菊科植物为例

PDF HTML阅读 XML下载 导出引用 引用提醒 植物核DNA含量在全球尺度上的纬度变异式样及其气候适应意义——以菊科植物为例 DOI: 10.5846/stxb201704270777 作者: 作者单位: 上海师范大学,上海师范大学,上海师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31070479） Latitudinal variation patterns of plant nuclear DNA amount on a global scale and their environmental adaptation significance: a case study with Asteraceae Author: Affiliation: College of Life and Environmental Sciences,Shanghai Normal University,Shanghai Normal University,College of Life and Environmental Sciences,Shanghai Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:核DNA含量是重要的生物学概念，涉及DNA C-值和基因组大小。前人有关植物核DNA含量在纬度梯度上的变异规律存在着矛盾的报道，而且多数将核DNA含量与纬度、海拔、气候等因素之间的关系描述成线性关系。核DNA含量是否具有环境适应上的意义，也还存在争议。先前有关核DNA含量与环境因素间关系的矛盾性报道可能与取样过小、地理范围过窄、研究对象遗传背景差异过大有关。如果对一个遗传背景相近的类群在全球范围内进行取样，核DNA含量会呈现有规律的纬度梯度变化，可能与大的气候因素之间存在非线性关系。菊科（Asteraceae）是被子植物的最大科，是一个广泛认可的自然分类群。为揭示全球空间尺度上植物核DNA含量在纬度梯度上的变异规律，以及这种变异是否具有环境适应意义，以菊科为对象开展了核DNA含量与纬度、生物气候因素关系的统计分析。从"植物DNA C-值数据库"检索到822种菊科植物的核DNA含量数据；在全球范围内，沿经度方向上设立10条样带，每条样带横跨15个经度，每条样带又均分成22个样块，每个样块纵跨7.5个纬度；其次，从"世界气候数据网站"下载1950-2000年时间段14个生物气候因子数据，应用ArcGIS 9.3获得每个样块14个生物气候因子的平均值；根据"全球生物多样性信息网站"记录，计算每个样块菊科植物平均的核DNA含量数据。为避免气候变量之间的多重共线性对数据分析的影响，应用主成分分析对数据进行了降维，发现最冷季度平均温度、最干季度雨量分别是第一、二主成分上荷载最大的因子，去除与它们相关性在-0.7至+0.7之间的其他气候因子后获得了最冷季度平均温度、最干季度雨量和最湿月份雨量三个变量用于进一步数据分析。结果发现，菊科植物在全球10个样带上的核DNA含量与纬度关系密切，与最冷季度平均温度、最干季度雨量和最湿月份雨量呈现极显著的单峰型的非线性关系，可以用二项式进行拟合。因此，全球空间尺度上植物核DNA含量沿着纬度梯度有规律性的非线性变化，这种变化具有很强的气候适应意义。 Abstract:Nuclear DNA amount is an important biological concept that includes DNA C-value and genome size. There are conflicting reports about latitudinal variation patterns of plant nuclear DNA amount. Relationships of plant nuclear DNA amount with latitude, altitude, and climatic variables have been reported as linear. Disputes also exist as to whether nuclear DNA amount of plants is of environmental adaptation significance. We speculated that the conflicting reports were due to insufficient sampling of the taxa, limitations in the geographical range, and different genetic backgrounds of the samples. Asteraceae is not only the largest family within angiosperms, but also a widely accepted natural taxa. To clarify the latitudinal variation patterns of plant nuclear DNA amount on a global scale, and to explore the possible climatic adaptation significance of these patterns, we conducted a study with Asteraceae to analyze the relationships of nuclear DNA amount with latitude and bioclimatic variables. First, we obtained the data of nuclear DNA amounts of 822 species of Asteraceae from the Plant DNA C-value database. We selected ten global longitudinal transects, each with a span of 15 longitudinal degrees, and evenly divided each transect(from 82.5°N to 82.5°S) into 22 blocks. We obtained geographical records of the 822 species from the Global Biodiversity Information Faculty, together with fourteen bioclimatic factors within these blocks from the Worldclim Global Climate Database. We calculated the average DNA 1C-values and genome sizes of each species in each block. To avoid multicollinearity among the fourteen climatic variables, we performed principal component analysis(PCA) to reduce the dimensionality of the variables. We found that the mean temperature of the coldest quarter and the precipitation of the driest quarter had the highest loads in the first two principal components. The climatic variables with low correlation coefficients(-0.7 to 0.7) with the above two variables were included in the analyses. We found that the nuclear DNA amounts of Asteraceae had a regular latitudinal variation that could be expressed by polynomial functions. The relationships of nuclear DNA amount with the mean temperature of the coldest quarter, the precipitation of the driest quarter, and the wettest month were typically nonlinear with a unimodal pattern, and could be expressed by binominal equations. Therefore, on the global scale, plant nuclear DNA amount changes regularly on latitudinal gradients, which has distinct climatic adaptation significance. 参考文献 相似文献 引证文献

Nuclear DNA C-values are correlated with pollen size at tetraploid but not diploid level and linked to phylogenetic descent in Streptocarpus (Gesneriaceae)

Genome size can affect the phenotype of plants by a simple physical effect of the DNA material at the cellular level. Pollen contains the bare necessities to initiate and sustain pollen tube growth and carries the haploid genome. This work investigates the extent to which the nuclear DNA content affects pollen size in an evolutionary context within Streptocarpus (Gesneriaceae), by correlating genome size with pollen size of 38 samples representing 36 taxa in a phylogenetic framework. Streptocarpus was found to possess an average genome size among diploid species of 0.82pg (1C). Significant genome downsizing of up to 44.4% was observed among the polyploid species which are exclusively found in Madagascar. The pollen size ranged between 11.27μm and 25.55μm at the diploid level, but 1C values were not found to drive pollen size. On the other hand, 1C values in most polyploids showed a strong positive correlation with pollen size, near linear in species of sect. Parasaintpaulia. In a phylogenetic context, polyploidy has evolved at least twice in the genus, and contrary to pollen size, genome size was strongly lineage-specific rather than adaptive in Streptocarpus. Repeated parallel increases and decreases in genome size (1C, and 1Cx) during the evolution of the genus were inferred. Overall, in Streptocarpus at least, pollen size is a limited predictor of genome size and only partly reflecting ploidy level, but may be of taxonomic value. The study demonstrates that the relationship between pollen size and genome size is not straightforward, and their evolutionary trajectories unlinked.

Analysis of DNA C-value and Ploidy of Five Species in Magnoliaceae

Analysis of DNA C-value and Ploidy of Five Species in Magnoliaceae

Clues to the evolution of genome size and chromosome number in Tabebuia alliance (Bignoniaceae)

The 82 genera recognized for Bignoniaceae are organized in eight major tribes, Jacarandeae, Tourrettieae, Tecomeae, Coleeae, Crescentiae, Oroxyleae, Catalpeae and Bignonieae. In addition, a monophyletic group, Crescentiina, including the Tabebuia alliance and the Paleotropical clade is recognized. The Tabebuia alliance, endemic to the Neotropics, includes c. 14 genera of trees and shrubs and is comprised of c. 147 species mainly of the genera Tabebuia and Handroanthus. We measured the nuclear DNA contents of 19 Bignoniaceae species to address genome size and chromosome number evolution of the Tabebuia alliance. Nuclear DNA content was estimated using flow cytometry and chromosome counts were performed using propidium iodide-stained metaphase cells. We also obtained data for three different Bignoniaceae species from the Royal Botanical Garden, Kew Plant DNA C-values database. We obtained the phylogenetic tree of analysed species from published data and used independent phylogenetic contrast to correlate chromosome number and 1C DNA content. An almost threefold range of variation in nuclear DNA content was observed among the 22 Bignoniaceae species that could only partially be explained by the occurrence of polyploidy. We found no significant correlation between chromosome number and DNA content among the analysed species. Our results suggest that both increases and decreases of genome size occurred in the evolution of the analysed Bignoniaceae Juss. species, with a large variation among Tabebuia alliance species.

Challenges of flow-cytometric estimation of nuclear genome size in orchids, a plant group with both whole-genome and progressively partial endoreplication.

Nuclear genome size is an inherited quantitative trait of eukaryotic organisms with both practical and biological consequences. A detailed analysis of major families is a promising approach to fully understand the biological meaning of the extensive variation in genome size in plants. Although Orchidaceae accounts for ∼10% of the angiosperm diversity, the knowledge of patterns and dynamics of their genome size is limited, in part due to difficulties in flow cytometric analyses. Cells in various somatic tissues of orchids undergo extensive endoreplication, either whole-genome or partial, and the G1-phase nuclei with 2C DNA amounts may be lacking, resulting in overestimated genome size values. Interpretation of DNA content histograms is particularly challenging in species with progressively partial endoreplication, in which the ratios between the positions of two neighboring DNA peaks are lower than two. In order to assess distributions of nuclear DNA amounts and identify tissue suitable for reliable estimation of nuclear DNA content, we analyzed six different tissue types in 48 orchid species belonging to all recognized subfamilies. Although traditionally used leaves may provide incorrect C-values, particularly in species with progressively partial endoreplication, young ovaries and pollinaria consistently yield 2C and 1C peaks of their G1-phase nuclei, respectively, and are, therefore, the most suitable parts for genome size studies in orchids. We also provide new DNA C-values for 22 orchid genera and 42 species. Adhering to the proposed methodology would allow for reliable genome size estimates in this largest plant family. Although our research was limited to orchids, the need to find a suitable tissue with dominant 2C peak of G1-phase nuclei applies to all endopolyploid species.

Estimation of Nuclear DNA Content in Tannin-rich Medicinal Plant Cornus officinalis by Flow Cytometry

ObjectiveThe amount of nuclear DNA (C-value) is a key biodiversity character that provides strong unifying elements in revealing the phylogenetic regularity and relationship between genome size and functional traits for plant resource. The estimation of C-values could primarily extend our knowledge on the genetic background and genome diversity for medicinal plants, and thereby the variation of pharmacological constituents and phylogenetic mechanism of medicinal plant taxa will be revealed. However, a large number of medicinal plants (e.g. Cornus officinalis) typically contain a series of secondary metabolites, especially tannic acid, which would significantly affect the estimation of DNA content by flow cytometry (FCM). Methodological discussions and improvement need to be made to solve this problem. MethodsTwo isolation buffers LB01 and Otto 1 were selected to prepare nuclear suspension with additional treatments of pre-soaking and centrifugation combination of gradient centrifugal force and duration. The best isolation and estimation methods were determined by FCM measurement in C. officinalis. ResultsThe dry leaves were pre-soaked in Otto I buffer for 15 min and the Otto I nuclear suspension was centrifugated at 1.0103g for 2 min. The results showed that debris and nuclei were better separated and the scatterplots of good quality were obtained with low coefficient of variation (CV). Contrarily, the nuclear DNA content of C. officinalis could not be accurately estimated for nuclei extracted by LB01 buffer. Finally, 2C-value and genome size of C. officinalis were first estimated as 5.92 pg and 2893 Mbp, respectively. ConclusionThe new methods proposed here are able to accurately estimate DNA content of C. officinalis, which provides valuable references for the estimation of genome size in other tannin-rich medicinal plants.