Nuclear Genome Size Research Articles

Karyology and Cytophotometric Estimation of Nuclear DNA Variation in Several Species of Polysiphonia (Rhodophyta, Ceramiales)

Results are given for a karyological investigation of 13 species of Polysiphonia from the North Atlantic Ocean and adjacent seas. Chromosome complements of 1 N = 28-36 are newly reported for six species. Microspectrophotometry with the DNA-localizing fluorochrome DAPI is used to estimate nuclear genome sizes. Incorporation of fluorescence values for chicken erythrocytes (RBC) permitted quantification of I f values for nine Polysiphonia species. The 2 C DNA contents range from 0.8 - 2.2 pg. The absence of a positive correlation between estimated genome size and 1 N chromosome complement excludes the possibility that speciation has resulted exclusively from loss or gain of chromosomes and associated genome

Variations of nuclear genome size in Citrus genus

Variations of nuclear genome size in Citrus genus

Quantitative nuclear DNA differences associated with genome evolution in Guizotia (Compositae)

The present communication deals with 2C nuclear genome size variation in a fairly small genus Guizotia. Twenty-four accessions belonging to six species, out of seven known, were analysed in order to elucidate the extent of DNA variation both at an intra—as well as interspecific level. At the intraspecific level none of the species exhibited significant differences in their genome size. Between the species, the 2C DNA amounts ranged from 3.61 pg in G. reptans to 11.37 pg in G. zavattarii; over three-fold DNA variation is evident. Apparently these interspecific DNA differences have been achieved independent of the numerical chromosomal change(s), as all the Guizotias share a common chromosome number 2n=2x=30. The cultivated oilseed crop, G. abyssinica (7.57 pg), has accommodated nearly 78% extra DNA in its chromosome complement during the evolutionary time scale of its origin and domestication from the wild progenitor G. schimperi (4.25 pg). The extent of genomic DNA difference(s) between the species has been discussed in the light of their interrelationships and diversity.

Nuclear DNA amounts in angiosperms

Collected lists of nuclear DNA amounts estimated for a total of almost 1000 angiosperm species were published by Bennett & Smith (Phil. Trans. R. Soc. Lond.B 274, 227—274 (1976)), and by Bennettet al. (Proc. R. Soc. Lond. B 216, 179-199 (1982a)). Subsequently, work on nuclear genome size in flowering plant taxa, and interest in its consequences, has increased. Thus, estimates for 588 angiosperm species not previously listed were published, or communicated to us, between 1982 and mid-1986. As these additional estimates came from more than 50 sources which were either widely scattered in the scientific literature or unpublished personal communications, they are not readily accessible. This, and the many personal enquiries for the information received, shows that a further publication, compiling the new data is needed. This paper, therefore, contains a further supplementary list of absolute DNA amounts. This new compilation includes DNACvalues for 629 angiosperm species not listed in either of the above-mentioned papers, with additional estimates for 119 species already listed by them. These data are assembled primarily for reference purposes. Analysis of citations of the two previously published lists and of personal requests for additional information both show that the major users of genome size information are cell and molecular biologists. Consequently, the species are listed as before in alphabetical order, rather than by any taxonomic scheme, as this was felt to be more helpful to these users

Karyology and cytophotometric estimation of inter- and intraspecific nuclear DNA variation in four species of Porphyra (Rhodophyta)

Abstract A cytogenetic investigation of four Porphyra species (Rhodophyta) from the temperate and tropical western Atlantic indicates that P. leucosticta Thuret in Le Jolis and P. spiralis Oliveira Filho et Coli var. amplifolia Oliveira Filho et Coli include populations with three and four chromosomes. Microspectrophotometry with the DNA-localizing fluorochrome hydroethidine was used to estimate nuclear genome sizes. Relative fluorescence (If) values for the angiosperms Antirrhinum majus Linnaeus and Arabidopsis thaliana (Linnaeus) Heynhold, and the green seaweed Cladophora albida (Hudson) Kutzing were plotted against their known DNA contents in order to derive a standard line. Mean nuclear DNA (If) values for Porphyra spermatia were extrapolated to obtain estimates of their genome sizes. The results indicate a narrow range of relatively small values (0.93–1.18 pg/2 C genome) in the isolates that were examined. Similarities in nuclear genome size for both three-and four-chromosome populations of P. leucos...

ANATOMICAL VARIATION IN FIRST LEAVES OF NINE TRITUCUM GENOTYPES, AND ITS RELATIONSHIP TO PHOTOSYNTHETIC CAPACITY

SummaryThe variation in over 20 leaf characters including morphological, anatomical and cellular features have been examined in nine Triticum genotypes at three levels of ploidy. The characters included transectional leaf area, leaf width, distance between vascular bundles, volume occupied by each cell type, cell size and number, and chloroplast size and number. Analysis of these characters showed that the major components of the variation were related to the ploidy level and the genotype of the species and cultivars examined. The measured characters most strongly influenced by ploidy level were cell size, chloroplast number and leaf thickness. Genetic variation accounted for the variation in all other measured characters. The interaction of genetic variation with the major effects attributable to ploidy level creates a characteristic anatomical ‘fingerprint’ for each genotype.The observation that photosynthetic capacity is negatively correlated with the ratio of mesophyll cell size to nuclear genome size, and with no other character, is discussed.

Estimation of Genome Size (C-Value) in Iridaceae by Cytophotometry

Nuclear genome sizes have been calculated for 19 genera and 30 species of Iridaceae using cytospectrophotometry. Mean extinction values for nuclei in squashes of actively growing root tips stained in Schiffs reagent were compared with a standard, maize, of known genome size, treated in the same

Freeze-fracture architecture and polypeptide composition of thylakoid membranes from euploid Ricinus cells.

The freeze-fracture architecture and polypeptide composition of thylakoid membranes of euploid cells of Ricinus communis L. were examined. Electron microscopic examination of the chloroplasts of 1N 2N and 4N cells revealed little variation in the size of chloroplasts, lamellar structure and internal organization of plastids, despite increases in plastid numbers per cell observed to accompany the increase in nuclear ploidy. Thylakoid membranes from euploid cells were also similar in their freeze-fracture morphology. Two basic types of intramembranous particles were observed on the fracture faces of thylakoid membranes of euploid cells. The endoplasmic fracture (EF) face of experimentally unstacked thylakoid membranes of 1N, 2N and 4N cells contain 2 size categories of particles (115-121 A and 164-166 A), whereas the protoplasmic fracture (PF) face of these membranes contain a single size category of particles (85-88 A). The distribution and size of the EF- and PF-face particles were found to be similar among membranes from cells of the 3 ploidy levels. Analysis of the polypeptide composition of thylakoid membranes from 1N, 2N and 4N cells revealed no difference in the relative proportion of the constituent polypeptides of these membranes. The possible factors involved in the regulation of the development of thylakoid structure and composition in the presence of altered nuclear genome size are discussed.

Ptiotosynthetic activity and chloroplast membrane polypeptides in euploid cells of Ricinus

The possible effects of altered nuclear complement size on the poiypeptide composition and photochemical activity of chloroplasts in haploid, diploid, and tetraploid cells, of Ricinus communis L. have been evaluated. The electron transport capacity in isolated chloroplasts decreases with the increase in nuclear genome size. Both Photosystem II (DCPIP reduction) and Photosystem 1 oxygen uptake (TMPD to methyl viologen) activities were lower in plastid preparations from tetraploid individuals than in diploid and haploid cell preparations. Photosynthetic O2‐evolution and CO2‐fixation rates in leaf tissue from euploid individuals were also found to decrease with the increase in size of the nuclear genome. Specific activity levels of RuBP‐carboxylase were observed to increase with ploidy. Electrophoretic examination of the poiypeptide composition of thylakoid membranes from haploid, diploid, and tetraploid celis revealed no difference in the relative proportions of the constituent polypeptides of these membranes. The regulation of chloroplast development and the basis for altered plastid function in the presence of altered nuclear genome size are discussed.

Comparative sensitivity of different plant chromosomes to [formula omitted] nitrosourea (NMU) : Degraeve, N., University of Liège, Genetics Dept., Liège (Belgium)

We examined induced androgenesis in vitro in the dioecious plant Melandrium album and aimed to produce complete plants from cultured immature microspores. Flow cytometric analysis of nuclear DNA content was used to screen ploidy levels in regenerated plants and to estimate the nuclear genome size in plants differing in sex. Haploid and spontaneous dihaploid (polyhaploid) females dominated among androgenic regenerants. Androgenic males occurred sporadically. They were exclusively dihaploid and genetically supermales (AAYY). The progenies obtained as a result of the crosses between supermales and standard females contained only males. This is the first report on complete androgenesis in M. album from the microspores carrying the Y chromosome.

Physical characterization of deoxyribonucleic acids in Dictyostelium discoideum

Methods are described for the preparation of highly purified nuclear and mitochondrial DNA from Dictyostelium discoideum. The former had a buoyant density of 1.683 g cm −3, yielded a thermal transition profile normal for double stranded DNA, and had a T m of 78.8 ± 0.2 °. These properties indicated a base composition of 23.1% G + C. The total DNA content per haploid cell is estimated as 1.0 × 10 −13g of which 60–65% is nuclear and 35–40% mitochondrial. The nuclear genome size was about 3.6 × 10 10 daltons or abovit 5.4 × 10 7 nucleotide pairs distributed among seven chromosomes. The sedimentation coefficient of the best preparations of purified DNA was 35.6 S for bulk and 27.6 S for nuclear. The purified mitochondrial DNA had a buoyant density of 1.688 g cm −3 (28% G + C) and yielded a normal thermal transition profile with a T m of 80 ± 0.2 °. No evidence of circularity was found.