Nuclear DNA Amounts in Pteridophytes

DNA amounts (C-value and genome size) are much-used biodiversitycharacters. A workshop held at Kew in 1997 identified majorgaps in our knowledge of plant DNA amounts, recommending targetsfor new work to fill them. Murray reviewed non-angiosperm plantsnoting that representation of pteridophyte species (approx.0.42%) was poor, while locating C-value data for them was verydifficult. The workshop confirmed the need to make data forother groups besides angiosperms accessible for reference purposes.This paper pools DNA C-values for 48 pteridophyte species fromeight original sources into one reference source, and fulfilsa key workshop recommendation for this group. Comparing thesedata shows that nuclear 1C-values in pteridophytes vary approx.1000-fold, from 0.055 pg in Selaginella species to about 55pg in Ophioglossum petiolatum. Genome size estimates for 25pteridophytes vary approx. 200-fold from 0.055 to 10.7 pg, andthe mean genome sizes in diploids and polyploids (5.15 and 4.59pg, respectively) are not significantly different. Wider comparisonsshow that ranges of genome sizes in the major groups of landplants are very different. Those in bryophytes and pteridophytesare narrow compared with those in gymnosperms and angiosperms.The data indicate that the origin of land plants possibly involveda first major increase in genome size in the evolution of vascularplants, while a second such increase occurred later in gymnosperms.C-values for pteridophytes remain very few, but conversely opportunitiesfor new work on them are many. Copyright 2001 Annals of BotanyCompany Pteridophyte DNA amounts, DNA C-values, nuclear genome sizes     

Nuclear DNA Amounts in Angiosperms

Bennett and Smith (Philosophical Transactions of the Royal Societyof London B274:227-274; B334: 309-345) and Bennett, Smith andHeslop-Harrison (Proceedings of the Royal Society of London,B216: 179-199) published lists of nuclear DNA amounts estimatedfor 1612 angiosperm species collected from 163 sources datedbetween 1951 and 1986. Subsequently, interest in genome sizein angiosperms and its significance has continued, and manynew DNA estimates were published during 1986-1994. Their inaccessibility,and the flow of enquiries for such information, shows that afurther compilation is needed. This paper presents a supplementarylist of nuclear DNA C-values for 105 sources for 899 angiospermspecies not listed in the above-mentioned compilations, plus284 additional estimates for 208 species already listed by them.The data are assembled primarily for reference purposes, withspecies listed in alphabetical order, rather than by any taxonomicscheme. Some advantages and limitations of flow cytometry, nowincreasingly used to quantify DNA C-values in plants, are reviewed.Recent reports regarding the occurrence and extent of intraspecificvariation in genome size are also discussed. While some examplesare real, others reflect technical shortcomings. Work has begunto combine the genome size data compiled in this and the above-mentionedpapers into a unified data base, and to present the informationin separate lists, with species in alphabetical and systematicorders, respectively. DNA C-values are now known for 1% of theworld's angiosperm flora, but improved representation of taxonomicgroups, geographical regions and plant life forms is urgentlyneeded.Copyright 1995, 1999 Academic Press Angiosperm DNA amounts, DNA C-values, nuclear genome sizes, intraspecific variation, flow cytometry, reference lists, genome size database     

Nuclear DNA Amounts in Angiosperms--583 New Estimates

The amount of DNA in the unreplicated haploid nuclear genome(itsC-value) varies over 600-fold between angiosperm species.Information regarding this character is used in a strikinglywide variety of plant biological fields. Moreover, recent studieshave noted a significant need for more information about thisimportant aspect of genome biodiversity. Bennett and co-authorshave published four collected lists of nuclear DNA amounts inangiosperm species, compiled primarily for reference purposes,including the most recent in 1995 (Annals of Botany76: 113–176).Together they list estimates for over 2500 species which representabout 1% of the global angiosperm flora. Interest in angiospermgenome size has remained high, as shown by the recent publicationof many new estimates, creating a need for a fifth compilation.This paper presents a supplementary list of nuclear DNAC-valuesfrom 37 sources for 471 angiosperm species not listed in theaforementioned compilations, plus additional estimates for 113species already listed by them. It contains estimates for palm,orchid and tropical hardwood species which significantly improvesrepresentation of the global flora. Work is in hand to combinethe genome size data compiled in this and the aforementionedpapers into a unified database, and to present the informationin separate lists, with species in alphabetical and systematicorders, respectively. Meanwhile, the availability of DNAC-valuesfor angiosperm species can be checked on the World Wide Web(http://www.rbgkew.org.uk/cval/database1.html). Angiosperm DNA amounts; DNAC-values; nuclear genome sizes; reference lists; plant DNA database     

Nuclear DNA Amounts in Palms (Arecaceae)

Nuclear DNA amounts are reported for 83 species and 53 genera of palms, covering all of the six subfamilies. 4C DNA contents range between 3.89 and 55.62 pg in diploids, showing an approximate 14.3-fold variation in genome size. Polyploids have DNA contents of up to 156.40 pg/4c which demonstrates a 40.2-fold variation. Diploids with high DNA contents occur in three subfamilies of palms (Coryphoideae, Calamoideae, Arecoideae), and seem to be further restricted to particular tribes or subtribes (Thrinacinae, Borasseae, Lepidocaryeae, Caryoteae, some subtribes of Areceae). Palms from the subfamilies Nypoideae and Phytelephantoideae have the lowest DNA amounts, followed by the Phoeniceae and the Corypheae: Livistoninae from the subfamily Coryphoideae. Although DNA amounts in some genera and subtribes are usually constant, e.g., in Phoenix, Phytelephas, the Livistoninae, Dypsidinae, diploid Butiinae), considerable variation occurs at the diploid level in some large and apparently actively evolving genera such as Chamaedorea, Pinanga, Cenoma and possibly Bactris. Formaldehyde fixation is recommended for palms, as conventional ethanol-acetic acid fixation has proved to be unsuitable for DNA estimation of Feulgen-stained nuclei by microdensitometry, since it can lead to errors up to 2.5-fold in extent. Chromosome counts are reported for 72 of the species studied, of which 42 are new.     

Nuclear DNA Amounts in Mosses (Musci)

A comparative investigation into nuclear DNA amounts using flowcytometry and video-based Feulgen densitometry was carried outin 289 accessions of 138 different moss taxa (Bryatae), originatingfrom Austria, Switzerland, Spain, Mexico and the USA. Samplingincluded species from all major moss clades (except Sphagnum).Flow cytometry data agreed highly with the Feulgen data, whichonce again demonstrates the high reliability of both methodsfor DNA amount determination. For the first time, extensivedata on absolute C-values of mosses are available. Haploid DNAcontents (1C) ranged from 0.174 to 2.16 pg, which representsonly about a 12-fold variation. This low C-value variation isremarkable when compared to angiosperms which vary approx. 1000-fold.C-values are usually relatively constant within genera and evenfamilies; however, genera with varying C-values also exist.From the low frequency observed, secondary polyploidy playsonly a minor role in mosses. Possible reasons for the low C-valuevariation are discussed. Copyright 2000 Annals of Botany Company Mosses, Bryatae, genome size, nuclear DNA amounts, C-value variation, Feulgen, flow cytometry, densitometry, image analysis     

Nuclear DNA Amounts in Angiosperms and their Modern Uses--807 New Estimates

The DNA amount in the unreplicated haploid nucleus of an organismis known as its C-value. C-values differ about 1000-fold amongangiosperms and are characteristic of taxa. The data are usedin many biological fields, so they should be easily available.Values for 2802 angiosperm species (1%) were estimated during1950–1997, and five collected lists of C-values were publishedfor reference purposes during 1976–1997. Numbers of newangiosperm C-values published recently remained high, necessitatinga further supplementary list. This paper lists DNA C-valuesfor 807 angiosperm species from 70 original sources, including520 (75.2%) from sources published after 1996, and 691 for speciesnot included in any of the previous five lists. There is a continuingneed to estimate accurate DNA C-values for plant taxa, as shownin a workshop on this biodiversity topic sponsored by Annalsof Botany and held at Kew in 1997. Its key aim was to identifymajor gaps in our knowledge of plant DNA amounts and to recommendtargets and priorities for new work to fill them. A target ofestimating first C-values for the next 1% of angiosperm speciesin 5 years was set. The proportion of such C-values in the presentwork (85.6%) is very high; and the number being published (approx.220 per annum) has never been exceeded. In 1997, C-values werestill unknown for most (68%) families, so a target of completecoverage was set. This paper includes first C-values for 12families, but as less than 2% of such values listed here targetednew families, the need to improve familial representation remains.Copyright 2000 Annals of Botany Company Angiosperm DNA amounts, DNA C-values, nuclear genome sizes, plant DNA database     

Ribosomal DNA Amounts in PISUM SATIVUM

Different varieties of peas have different proportions of rDNA in their genomes; there is no obvious correlation between the proportions and seed or leaf size. The rDNA proportions in root tips, seedlings, leaves and in the cotyledon cells of high DNA content, were compared in four varieties. In three, there was no difference between tissues; the fourth showed an amplification of rRNA genes in the cells of high DNA content of the seed cotyledon, and also in the cells of young but not of older leaves. The fourth variety was the one that had the lowest proportion of rDNA of all those examined. Studies of the tissues of hybrids between genotypes with "low" and "high" proportions of rDNA showed that heterozygotes had the "high" value, showing again the occurrence of an amplification phenomenon.     

Amounts of nuclear DNA in marine halophytes

The amount of nuclear DNA, expressed as the C-value, was estimated for 13 marine halophytic plant species from six families. Plant material was collected in the nature reserve of the Strunjan saltpan in the Northern Adriatic and comprised all halophytic species inside the investigated area. Reproductive region of the shoot or root tips of halophytes were dissected, nuclei were Feulgen stained and 2C-values were measured by DNA image cytometry as follows: Crithmum maritimum (4.38 pg DNA), Artemisia caerulescens (6.43 pg), Aster tripolium (21.43 pg), Inula crithmoides (3.63 pg), Atriplex portulacoides (1.83 pg), A. prostrata (1.51 pg), Salicornia europaea (2.75 pg), Salsola soda (2.62 pg), Sarcocornia fruticosa (5.91 pg), Suaeda maritima (2.11 pg), Limonium angustifolium (5.06 pg), Puccinellia palustris (8.15 pg) and Ruppia cirrhosa (4.65 pg). With the exception of the C-value estimate for A. caerulescens, which has been listed in the Plant DNA C-values Database, the C-values represent the first estimates for all the examined species. In addition, the C-value for R. cirrhosa is also the first report for the family Ruppiaceae. The investigated halophytes had a smaller genome size compared to other known C-values for species within a particular family and also when compared to the mean values of dicots and monocots. The study also showed that halophylic annuals have a smaller genome size (2.49 pg) than perennial ones (7.45 pg DNA).     

Amounts of nuclear DNA in marine halophytes

The amount of nuclear DNA, expressed as the C-value, was estimated for 13 marine halophytic plant species from six families. Plant material was collected in the nature reserve of the Strunjan saltpan in the Northern Adriatic and comprised all halophytic species inside the investigated area. Reproductive region of the shoot or root tips of halophytes were dissected, nuclei were Feulgen stained and 2C-values were measured by DNA image cytometry as follows: Crithmum maritimum (4.38 pg DNA), Artemisia caerulescens (6.43 pg), Aster tripolium (21.43 pg), Inula crithmoides (3.63 pg), Atriplex portulacoides (1.83 pg), A. prostrata (1.51 pg), Salicornia europaea (2.75 pg), Salsola soda (2.62 pg), Sarcocornia fruticosa (5.91 pg), Suaeda maritima (2.11 pg), Limonium angustifolium (5.06 pg), Puccinellia palustris (8.15 pg) and Ruppia cirrhosa (4.65 pg). With the exception of the C-value estimate for A. caerulescens, which has been listed in the Plant DNA C-values Database, the C-values represent the first estimates for all the examined species. In addition, the C-value for R. cirrhosa is also the first report for the family Ruppiaceae. The investigated halophytes had a smaller genome size compared to other known C-values for species within a particular family and also when compared to the mean values of dicots and monocots. The study also showed that halophylic annuals have a smaller genome size (2.49 pg) than perennial ones (7.45 pg DNA).     

Amounts of ribosomal DNA inAllium (Liliaceae)

Eight species ofAllium subgen.Allium sect.Allium have been studied at the cytological level by means of karyological analyses and at the biochemical level with regard to the proportions of ribosomal DNA. All the species have a basic genome of x = 8.A. sativum, A. commutatum, A. ampeloprasum, andA. vineale possess approximately 0.050% rDNA and two nucleolus organizer regions per basic chromosome set.A. sphaerocephalon andA. arvense have two nucleolus organizers, andA. amethystinum three nucleolus organizers per haploid (n = x) genome: the three species possess approximately 0.075% rDNA.A. acutiflorum has five nucleolus organizer regions per haploid genome and 0.121% rDNA. An attempt to relate these differences with functional and ecological characteristics indicates that evolutionary variation of rDNA proportions is not casual. Such data also can help to define systematic affinities and circumscribe infrageneric taxa.     

Nuclear DNA variation in Eu-Sorghums

There are significant differences in nuclear DNA amount between Eu-Sorghum species. The DNA variation is considerable. For example Sorghum durra has 63 per cent more DNA than Sorghum roxburghii. Increase in nuclear DNA is accompanied by increase in the mass of the nucleolus and of non-nucleolar material including the chromosomes. The ratio of DNA to non-DNA material is constant between species. The DNA concentration per unit volume at interphase in somatic nuclei and per unit of chromosome length is significantly lower in the wild species S. sudanense and S. virgatum than in the cultivated species S. caudatum, S. conspicuum, S. durra and S. roxburghii. It is suggested that the lower DNA concentration may reflect a lower proportion of heterochromatin relative to euchromatin in the wild as compared with the cultivated forms.     

Nuclear DNA variation in Lathyrus

In the genus Lathyrus the divergence and evolution of species was accompanied by large scale changes in nuclear DNA amount. All the species are diploids with 14 chromosomes so that the DNA changes were the result of amplification or deletion of segments within chromosomes. Our evidence indicates that the quantitative changes involve mainly the repetitive, as distinct from the non-repetitive fraction of the chromosomal DNA and, on a cytological basis, mainly heterochromatin in contrast to euchromatin. There is an element of discontinuity in the distribution of DNA amounts among species which suggests that the DNA variation results from a series of separate, spasmodic events. The discontinuities may be viewed, also, as steady states from the standpoint of genetic balance and biological fitness.     

Nuclear DNA variation in Tephrosia

2C nuclear DNA amounts and chromatin areas were estimated in twenty diploid and tetraploid (2n=22, 44; x=11) species of the genus Tephrosia. There were significant differences between the species both in DNA content and chromatin area. The divergence and evolution of Tephrosia species was accompanied by large scale quantitative DNA variation, ranging from 1.3 picograms in T. strigosa to 7.4 in T. pumila, and the DNA amount varied independently of the chromosome number. The element of discontinuity in the distribution of DNA changes between complements was quite regular. The species fell into eight distinct cluster groups with an interval of 0.74 pg between the two adjoining groups. In the light of the karyotypic and nuclear DNA differences between T. leptostachya, T. hamiltonii, T. wallichii and T. purpurea, T. incana and T. villosa, T. subtriglora and T. multiflora, these is indeed a case for considering them as separate species and not synonyms of T. purpurea, T. villosa and T. multiflora. DNA density increased with increase in DNA contents. As expected, the DNA content of colchitetraploids (C₀, C₁, C₂) was almost double to the amount present in their corresponding diploids.     

Nuclear matrix-associated DNA methylase

Previous procedures for the extraction of DNA methylase (EC 2.1.1.37) from nuclei of mouse ascites cells have involved the use of buffers containing 0.2M NaCl. Whilst such 'soluble' methylase accounts for the bulk (70-80%) of DNA methylase activity a further portion of activity is detectable in a 'bound' form firmly associated with 2 M NaCl-resistant nuclear matrix-like structures. This association, which in part requires continuing DNA replication and protein synthesis, can, however, be disrupted in vitro with high concentrations of ammonium sulphate, and the enzymic properties of the 'bound' form of DNA methylase are similar to those described for the 'soluble' form.     

Nuclear DNA amounts in pacific Crustacea

Nuclear DNA amounts have been determined for 42 species of crustaceans bringing the total number of species with known nuclear DNA content to over 70. Genome size in Crustacea varies over a 25-fold range with a modal value of 2 to 3 pg haploid being common in many groups. Both average genome size and the amount of variability among species are characteristic for certain groups. A trend towards small genomes is evident in advanced and specialized crustacean groups. Somatic polyploidy is a very pronounced feature of the Crustacea. The data suggest that evolution by polyploidy may be more common in crustaceans than earlier data had indicated. These features and the presence of very characteristic satellite fractions in the nuclear DNA recommend the Crustacea for further studies in evolutionary genetics.     

Nuclear DNA cytophotometry in prostate carcinoma

Eighty patients with prostate carcinoma underwent fine-needle aspiration biopsy for cytologic grading and DNA-single-cell fluorescence photometry before and at 6-month intervals after endocrine treatment. The histograms of DNA values showed single peaks and bimodal and scattered distributions which correlated to the different tumor grades before therapy. The DNA values were significantly different from the controls with benign prostatic hypertrophy. After start of therapy, regressive changes of the DNA-histograms were increases of diploid and hypodiploid DNA values and disappearance of secondary peaks. Progressive changes were increased scattering of DNA values and appearance of secondary peaks. Progressive changes in the histograms were closely related to clinical remission and stable disease, but related poorly to clinical progression. The survival correlated with the pretherapeutic DNA-histograms and with the DNA-median, third-quartile, and maximum parameters.     

Nuclear DNA amounts in Macaronesian angiosperms

Nuclear DNA contents for 104 Macaronesian angiosperms, with particular attention on Canary Islands endemics, were analysed using propidium iodide flow cytometry. Prime estimates for more than one-sixth of the whole Canarian endemic flora (including representatives of 11 endemic genera) were obtained. The resulting 1C DNA values ranged from 0.19 to 7.21 pg for Descurainia bourgeauana and Argyranthemum frutescens, respectively (about 38-fold difference). The majority of species, however, possessed (very) small genomes, with C-values <1.6 pg. The tendency towards small nuclear DNA contents and genome sizes was confirmed by comparing average values for Macaronesian and non-Macaronesian representatives of individual families, genera and major phylogenetic lineages. Our data support the hypothesis that the insular selection pressures in Macaronesia favour small C-values and genome sizes. Both positive and negative correlations between infrageneric nuclear DNA amount variation and environmental conditions on Tenerife were also found in several genera.