Showing papers on "Nuclear DNA published in 1983"
TL;DR: It is found that Zn2+ also inhibits DNA fragmentation and 51Cr release induced by cytotoxic T cells, suggesting a final common biochemical pathway for both types of cell death.
Abstract: Within minutes of exposure of target cells to cytotoxic T lymphocytes, their nuclear DNA begins to be fragmented. This phenomenon precedes 51Cr release by at least an hour. DNA fragmentation occurs only when appropriately sensitized cytotoxic T cells are used and is not merely a result of cell death because killing of target cells by heating, freeze/thawing, or lysing with antibody and complement did not yield DNA fragments. Agarose gel electrophoresis of target cell DNA showed discrete multiples of an approximately 200-base-pair subunit, suggesting that fragmentation was the result of activation of a specific endonuclease. A similar pattern of DNA fragments is observed during glucocorticoid-induced killing of mouse thymocytes. The endonuclease in that case is inhibited by zinc ions, and we find that Zn2+ also inhibits DNA fragmentation and 51Cr release induced by cytotoxic T cells, suggesting a final common biochemical pathway for both types of cell death.
588 citations
TL;DR: The results suggest that the nuclear matrix is the site of nuclear transcription and may represent another potential level of control for regulation of gene expression in the eukaryotic cell.
Abstract: In the chicken oviduct, it has been well documented that steroid hormones stimulate the transcription of specific genes such as the ovalbumin gene. In addition to the presence of specific hormone receptors in the tissue, gene expression seems to require that target genes exist in large DNase I sensitive chromosomal domains. This structure appears necessary but not sufficient for transcriptional activation. In search of still other levels of control, we have investigated the interactions of genes with the nuclear matrix, a structure which has been implicated in DNA synthesis, transcription and RNA processing. Here we have isolated nuclear matrix and used a nondegradative method to fractionate nuclear DNA based on its preferential association with the matrix. The preparation was digested with a restriction enzyme and both matrix-bound and released DNAs were recovered. We found that only actively expressed genes were associated with the matrix. Furthermore, within a 100-kilobase (kb) DNase I sensitive chromosomal domain, only the transcribed regions were associated with the matrix. This association was shown to be reversible when hormone was withdrawn. Our results suggest that the nuclear matrix is the site of nuclear transcription and may represent another potential level of control for regulation of gene expression in the eukaryotic cell.
358 citations
TL;DR: The procedure has been used successfully with several dozen isolates of the plant pathogenic fungus Cochliobolus heterostrophus (including both laboratory strains and isolates collected directly from the field), and has been found to be equally suitable for C. carbonum, Neurospora crassa, N. tetrasperma, and Nectria haematococca.
231 citations
TL;DR: Leishmania tropica promastigotes that are highly resistant to methotrexate, a dihydrofolate reductase inhibitor, and it appears that drug resistance in parasitic protozoa may be mediated by gene amplification.
Abstract: Leishmania tropica promastigotes that are highly resistant to methotrexate, a dihydrofolate reductase inhibitor, have been developed. Organisms resistant to 1 mM methotrexate have a 40-fold increase in dihydrofolate reductase which is associated with thymidylate synthetase, and they contain amplified regions of DNA that may be directly visualized on stained gels of restriction digests. The amplified DNA in these organisms is about 56 kilobases in length, has a copy number about 80-fold higher than that of wild-type organisms, and constitutes about 10% of the nuclear DNA. When the methotrexate-resistant L. tropica are propagated in drug-free medium, the dihydrofolate reductase-thymidylate synthetase protein and the amplified DNA decrease in a parallel fashion until they are indistinguishable from the levels in wild-type organisms. However, when these apparent revertants are again challenged with 1 mM methotrexate, enzyme overproduction and DNA amplification occur rapidly. As in mammalian cells, it appears that drug resistance in parasitic protozoa may be mediated by gene amplification.
214 citations
TL;DR: By high-resolution, restriction mapping of mitochondrial DNAs purified from 112 human individuals, the mystery of why vertebrate mtDNA is more prone than nuclear DNA to evolve by point mutation is now compounded by the discovery of a similar bias toward rapid evolution by length mutation.
Abstract: By high-resolution, restriction mapping of mitochondrial DNAs purified from 112 human individuals, we have identified 14 length variants caused by small additions and deletions (from about 6 to 14 base pairs in length). Three of the 14 length differences are due to mutations at two locations within the D loop, whereas the remaining 11 occur at seven sites that are probably within other noncoding sequences and at junctions between coding sequences. In five of the nine regions of length polymorphism, there is a sequence of five cytosines in a row, this sequence being comparatively rare in coding DNA. Phylogenetic analysis indicates that, in most of the polymorphic regions, a given length mutation has arisen several times independently in different human lineages. The average rate at which length mutations have been arising and surviving in the human species is estimated to be many times higher for noncoding mtDNA than for noncoding nuclear DNA. The mystery of why vertebrate mtDNA is more prone than nuclear DNA to evolve by point mutation is now compounded by the discovery of a similar bias toward rapid evolution by length mutation.
196 citations
TL;DR: A contiguous DNA sequence in the yeast nuclear genome with extensive homology to non-contiguous yeast mitochondrial DNA sequences is found and certain features of the content and organization suggest that it may have originated from petite mitochondrial DNA which integrated into the nuclear genome.
Abstract: We have found a contiguous DNA sequence in the yeast nuclear genome with extensive homology to non-contiguous yeast mitochondrial DNA sequences. Closely linked to this nuclear sequence in some, but not all, yeast strains is a tandem pair of transposable (Ty) elements. Certain features of the content and organization of this nuclear DNA sequence suggest that it may have originated from petite mitochondrial DNA which integrated into the nuclear genome.
172 citations
TL;DR: Two clones are isolated from a gene library of the insect, Locusta migratoria, representing separate fragments of nuclear DNA, which contain sequences homologous to the mitochondrial genes for ribosomal RNA, as well as regions of homology with highly repeated nuclear sequences.
Abstract: The endosymbiotic theory1 of the origin of mitochondria is widely accepted, and implies that loss of genes from the mitochondria to the nucleus of eukaryotic cells has occurred over evolutionary time2,3. However, evidence at the DNA sequence level for gene transfer between these organelles has so far been limited to a single example, the demonstration that a mitochondrial ATPase subunit gene of Neurospora crassa has an homologous partner in the nuclear genome4. From a gene library of the insect, Locusta migratoria, we have now isolated two clones, representing separate fragments of nuclear DNA, which contain sequences homologous to the mitochondrial genes for ribosomal RNA, as well as regions of homology with highly repeated nuclear sequences. The results suggest the transfer of sequences between mitochondrial and nuclear genomes, followed by evolutionary divergence.
149 citations
TL;DR: The results are consistent with mitochondrial transmission of mitochondrial Cytopathy; the inheritance and enzyme defects of mitochondrial cytopathy can be considered in the light of recent evidence that subunits of respiratory-enzyme complexes are encoded solely by mitochondrial DNA.
Abstract: Mendelian inheritance involves the transmission to successive generations of DNA contained in genes in the nucleus, but DNA is also contained in mitochondria, where it is believed to be responsible for the encoding of certain mitochondrial enzymes. Since nearly all mitochondrial DNA is maternally transmitted, one might expect a nonmendelian pattern of inheritance in mitochondrial cytopathy, a syndrome in which there are abnormalities in mitochondrial structure and deficiencies in a variety of mitochondrial enzymes. We studied the pedigrees of 6 affected families whose members we had examined personally and of 24 families described in the literature. In 27 families, exclusively maternal transmission occurred; in 3 there was also paternal transmission in one generation. Altogether, 51 mothers but only 3 fathers had transmitted the condition. These results are consistent with mitochondrial transmission of mitochondrial cytopathy; the inheritance and enzyme defects of mitochondrial cytopathy can be considered in the light of recent evidence that subunits of respiratory-enzyme complexes are encoded solely by mitochondrial DNA. The occasional paternal transmission may be explained if certain enzyme subunits that are encoded by nuclear DNA are affected.
143 citations
TL;DR: Comparisons of the distribution of DNA amounts among chromosomes within the complements show that increase in total nuclear DNA amount within the genus Vicia is achieved by equal increments to each chromosome independent of size, which concludes that relative size may itself be of adaptive importance.
Abstract: 2C nuclear DNA amounts in diploid species of the genus Vicia (x = 5, 6, and 7) range from approximately four to twenty seven picograms. The DNA amount varies independently of the chromosome number and of taxonomic grouping within the genus. Comparisons of the distribution of DNA amounts among chromosomes within the complements show that increase in total nuclear DNA amount within the genus is achieved by equal increments to each chromosome independent of size i.e., small chromosomes acquire the same amount of extra DNA as the large chromosomes. An inevitable consequence of such a pattern of DNA change is that the chromosomes within complements with high DNA amount are more alike in size and DNA content, more symmetrical, than within complements of species with low DNA amount. In a few species the symmetry is confounded as a result of Robertsonian fusion. The equal distribution of extra DNA among chromosomes within a complement has been reported in other genera of flowering plants viz. in Lolium, Festuca and Lathyrus. In all cases there is evidently a severe constraint either upon the way in which the nuclear DNA variation is achieved or else upon its persistence in the face of selection. Since the pattern of change affects the relative sizes of chromosomes within complements we conclude that relative size may itself be of adaptive importance.
112 citations
TL;DR: Evidence is presented that young mitochondria of the rapidly senescing race, A+, possess an extremely high copy number of α-event senDNA plasmid in contrast to the more slowly senesced races s+ or s−, the first clear evidence for the active mobilization of genetic elements from the mitochondrion to the nucleus.
Abstract: Cellular senescence in the ascomycete fungus Podospora anserina is associated with the appearance of an altered mitochondrial genome. Discrete mitochondrial DNA sequences are excised and amplified and isolated as multimerically arranged, head-to-tail repetitions. We have referred to the most frequently observed excision/amplification product as alpha-event senDNA. It is a 2.6-kilobase pair (kbp) monomeric unit (see refs 1, 3, 7) and is often found in senescent mitochondria in conjunction with other excision products. At the final stage of senescence these plasmids constitute virtually all of the DNA present in senescent mitochondria; they have replicated to high copy number at the expense of the young native genome. Because P. anserina is characterized by race-specific timing of senescence (that is, a programme of senescence), we have begun to contrast rapidly and slowly senescing races in terms of senDNA. Here we present evidence that young mitochondria of the rapidly senescing race, A+, possess an extremely high copy number of alpha-event senDNA plasmid in contrast to the more slowly senescing races s+ or s-. Moreover, we observe that during senescence the alpha-event senDNA and the beta-event senDNA (a 9.8-kbp monomer) are transposed to the nucleus and integrated into nuclear DNA. These plasmids contain the coding information for subunits I and III (respectively) of the mitochondrial cytochrome c oxidase. This constitutes the first clear evidence for the active mobilization of genetic elements from the mitochondrion to the nucleus.
105 citations
Journal Article•
TL;DR: Five distinct cDNA clones for the major chlorophyll a/b binding protein (Cab) of the petunia thylakoid membrane light-harvesting complex have been characterized.
Abstract: Five distinct cDNA clones for the major chlorophyll a/b binding protein (Cab) of the petunia thylakoid membrane light-harvesting complex have been characterized. The nucleotide sequences of the polypeptide coding regions are similar between clones; however, the 3'-untranslated regions are divergent. Analysis of petunia nuclear DNA through genomic hybridizations and characterization of cloned nuclear fragments indicates there are at least sixteen genes for the major Cab protein. These genes can be classified into at least five small multigene families on the basis of their homology to the different cDNA clones. Two families contain only two genes each and in both cases the genes are closely linked in the genome. In one case, one gene is in an inverted orientation with respect to the other such that the 5' ends are adjacent; in the other case, the two genes are in a tandem array. Both genes from one of these families are transcribed in green leaves. The genes belonging to separate nuclear gene families encode different polypeptide components of the major Cab protein.
TL;DR: It is demonstrated that mtDNA-like sequences are present in human nuclear DNA.
TL;DR: The structure of the genomic mitochondrial sequence homologues indicates that during sea urchin evolution there occurred a germ-line transposition of a fragment of the mitochondrial genome into the nuclear DNA, followed by rearrangements and single nucleotide substitutions.
01 Jan 1983
TL;DR: Ribulose-1,5-bisphosphate carboxylase is the major stromal protein in chloroplasts from C3 plants and performs the first step in the Calvin cycle.
Abstract: Ribulose-1,5-bisphosphate (RuBP) carboxylase is the major stromal protein in chloroplasts from C3 plants. It performs the first step in the Calvin cycle and is composed of 8 large subunits and 8 small subunits. The large subunits, of 53,000 daltons, are encoded by chloroplast DNA and the small subunits, of 14,000 daltons, are encoded by nuclear DNA (1,2). The small subunit is synthesized as a 20,000 dalton precursor, on free cytoplasmic ribosomes (3–6). This precursor functions in the post-translational transport of the small subunit from the site of synthesis into chloroplasts (5,6).
TL;DR: Examination of nuclear DNA by Southern hybridization and analysis of cloned small subunit genes confirm that there are a number of different genes which encode this single protein.
Abstract: The sequences in the petunia genome which encode the small subunit polypeptides of the chloroplast enzyme ribulose-1,5-bisphosphate carboxylase have been characterized. Sequence analysis of four cDNA clones indicate that there are several distinct genes transcribed in leaf tissue. There is 8-9% nucleotide divergence between the transcripts however these changes do not alter the encoded amino acid sequence. Examination of nuclear DNA by Southern hybridization and analysis of cloned small subunit genes confirm that there are a number of different genes which encode this single protein.
TL;DR: The environment has been shown to induce heritable changes in three plant systems, namely flax, Nicotiana rustica, and soybean cell suspension cultures, and the phenomenon of environmentally induced DNA variation is compared with examples of gene amplification or deletion in other systems.
Abstract: The environment has been shown to induce heritable changes in three plant systems, namely flax, Nicotiana rustica, and soybean cell suspension cultures. Changes in nuclear DNA sequences associated with the induction phenomenon have been demonstrated in both flax and soybean. In flax, which has been most extensively studied, the overall variation in the nuclear DNA is described together with a number of transcribed and nontranscribed sequences which have been shown to vary. Possible mechanisms by which the observed DNA changes could arise are discussed and the phenomenon of environmentally induced DNA variation compared with examples of gene amplification or deletion in other systems.
TL;DR: There is substantial interspecific variation in nuclear DNA content in Festuca much of which cannot be accounted for by variation in chromosome number.
Abstract: There is substantial interspecific variation in nuclear DNA content in Festuca much of which cannot be accounted for by variation in chromosome number. The distribution of species DNA contents closely matches the taxonomic divisions within the genus. Polyploid taxa, especially high polyploids, tend to have less DNA than expected. (a) There may be errors in the proposed modes of origin of polyploid forms. In particular, the distinction between European and Moroccan forms may have been underestimated, and/or (b) polyploid species may have undergone a reduction in nuclear DNA content since their divergence, relative to their progenitor species of lower ploidy.
TL;DR: It appears that, as in lower eukaryotes, there are shared sequences between the nuclear and mitochondrial genomes in mammals.
Abstract: Although Pst I does not cut the circular mitochondrial genome of the rat, BamHI generates from this genome two unequal fragments of DNA. Each of these fragments was cloned in pBR322. Nuclear DNA was digested from rat liver singly or doubly with Pst I and BamHI, and it was demonstrated that nuclear DNA shared a common sequence with the larger mitochondrial DNA BamHI fragment. The cloned larger mitochondrial DNA fragment was further subdivided with HindIII into four pieces that were labeled and then used to probe the double-digested nuclear DNA. The hybridization data showed that the common sequence is less than 3 kilobase pairs long and lies within the part of the mitochondrial genome containing the D-loop and a portion of the rRNA genes. It therefore appears that, as in lower eukaryotes, there are shared sequences between the nuclear and mitochondrial genomes in mammals.
TL;DR: Evidence for the importance of this molecular association (which is probably cation-mediated) is provided by alkaline buffer extraction of the protein matrix in chromosomes of Amphidinium carterae, leading to complete destabilisation of the DNA framework.
Abstract: High resolution electron microscope autoradiographs of [3H]adenine incorporation in the dinoflagellate Prorocentrum micans suggest that RNA transcription occurs on extrachromosomal DNA filaments, but not on DNA in the main body of the chromosome. This genetically inactive DNA has an important role, however, in stabilising chromosome structure by its association with protein matrix. Evidence for the importance of this molecular association (which is probably cation-mediated) is provided by alkaline buffer extraction of the protein matrix in chromosomes of Amphidinium carterae, leading to complete destabilisation of the DNA framework. The clear distinction between structural DNA and genetically active DNA in these chromosomes provides a marked contrast to normal eucaryote chromosomes. This distinction is related to the occurrence of high DNA values in these organisms, and the evolutionary status of the dinoflagellate chromosome.
TL;DR: There appear to be constraints upon changes in nuclear organization during speciation in the evolution of species within the genus Lathyrus.
Abstract: Large changes in chromosome size and nuclear DNA amounts have occurred in the evolution of species within the genusLathyrus, which are also reflected in the amounts of heterochromatin and euchromatin and of repetitive and non-repetitive sequences. The distributions of nuclear DNA in the chromosome complements of 4Lathyrus species are compared. Although there is a doubling of the total amounts of nuclear DNA between highest and lowest of the four species the distribution among the chromosomes of each complement is approximately the same. Hence underlying these evolutionary changes there appear to be constraints upon changes in nuclear organization during speciation.
TL;DR: The results of this study suggest that DNA sequences which account for the DNA content differences among the plants are unstable and can undergo deletion or amplification in a hybrid and may be heritably stable and show little or no segregation in the F2 progeny.
Abstract: Nuclear DNA content varies over 20% within the diploid (2n = 18) species M. douglasEi and M. bigelovii. Two different intraspecific crosses were made between M. douglasEi biotypes which differed by about 10% in 2C nuclear DNA content. The F2 progeny of one intraspecific cross showed no striking evidence of segregation for DNA content. The mean DNA contents of F2 progeny from two sister hybrids from the second intraspecific cross were significantly different at the 1% level. An interspecific cross was made between biotypes of M. douglasEi and M. bigelovii that differed by approximately 10% in DNA amount. The 12 Fl progeny did not cluster around the parental midpoint, but instead encompassed nearly the entire range between the parental means. The five families of F2 progeny studied each had a mean DNA content corresponding to that of the particular Fl from which they were derived, indicating that the Fl plants were not of identical DNA content. The results of this study suggest that DNA sequences which account for the DNA content differences among the plants are unstable and can undergo deletion or amplification in a hybrid. The altered DNA content may be heritably stable and show little or no segregation in the F2 progeny.
TL;DR: It was concluded that these attributes constitute probalistic constraints on th primary structure (base sequence) of both coding and non-coding DNA.
Abstract: Coding sequences of eucaryotic nuclear DNA were characterized by an excess of short runs and a deficit of long runs of weak and of strong hydrogen bonding bases; non-coding sequences by a deficit of short runs and an excess of long runs, in the same of purines and of pyrimidines. The conservation of these attributes across DNA sequences coding for proteins of widely different function, across widely different eucaryotic species for the same protein and across related genes that diverged a long time ago and that now show large differences in base and, if coding, amino acid sequence suggested that these attributes have survival value. It was concluded that these attributes constitute probalistic constraints on th primary structure (base sequence) of both coding and non-coding DNA.
TL;DR: Electron microscopic analysis of the DNA fragments present shows an enrichment for HeLa DNA replicating forks, and this matrix-DNA complex appears to be composed of a unique set of proteins.
Abstract: Upon treatment of HeLa nucleoids with EcoR1 restriction enzyme, a minute fraction of the DNA remains attached to the nuclear matrix. This matrix-DNA complex appears to be composed of a unique set of proteins. Electron microscopic analysis of the DNA fragments present shows an enrichment for HeLa DNA replicating forks.
TL;DR: Sequences of alternating purine-pyrimidine residues with Z-DNA forming potential have been detected in the nuclear DNA of two higher plant species: wheat and radish.
TL;DR: Temperature-sensitive mutants of cdc2 mutants are defective in an aspect of initiation of DNA replication common to all chromosomes such that a random fraction of the chromosomes fail to initiate replication at 37 degrees C, but that once initiated, replication proceeds normally.
Abstract: Chromosomal DNA replication was examined in temperature-sensitive mutants of Saccharomyces cerevisiae defective in a gene required for the completion of S phase at the nonpermissive temperature, 37 degrees C. Based on incorporation of radioactive precursors and density transfer experiments, strains carrying three different alleles of cdc2 failed to replicate approximately one-third of their nuclear genome at 37 degrees C. Whole-cell autoradiography experiments demonstrated that 93 to 96% of the cells synthesized DNA at 37 degrees C. Therefore, all cells failed to replicate part of their genome. DNA isolated from terminally arrested cells was of normal size as measured on neutral and alkaline sucrose gradients, suggesting that partially replicated DNA molecules do not accumulate and that DNA strands are ligated properly in cdc2 mutants. In addition, electron microscopic examination of the equivalent of more than one genome's DNA from arrested cells failed to reveal any partially replicated molecules. The sequences which failed to replicate at 37 degrees C were not highly specific; eight different cloned sequences replicated to the same extent as total DNA. The 2-microns plasmid DNA and rDNA replicated significantly less well than total DNA, but approximately one-half of these sequences replicated at 37 degrees C. These observations suggest that cdc2 mutants are defective in an aspect of initiation of DNA replication common to all chromosomes such that a random fraction of the chromosomes fail to initiate replication at 37 degrees C, but that once initiated, replication proceeds normally.
TL;DR: It is not yet clear whether mutagenic potential is a necessary attribute for anti-cancer action, but cells in late S or early G2 phase of the cell cycle are most susceptible to DNA intercalators while non-replicating cells are much more resistant.
Journal Article•
TL;DR: It is proposed that guanine cytosine-enriched low m.w.W. DNA fragments accumulate in cells after nuclear DNA is degraded, and that these fragments may serve as a primary source of autoantigen for anti-DNA antibody production and interfere with normal cellular metabolism.
Abstract: The fate of the newly synthesized DNA in peripheral blood lymphocytes from patients with systemic lupus erythematosus was examined After lymphocytes were stimulated with the mitogen phytohemagglutinin (PHA), DNA was pulse-labeled with radioactive thymidine and was analyzed by sucrose density gradient centrifugation Two classes of DNA were identified; the main DNA fraction that migrated to the same position as that of control samples, and low mw DNA fragments The low mw DNA fragments were further characterized: i) The amount of low mw fragments increased with increasing time of culture after PHA stimulation ii) The guanine cytosine content was 47% of the total bases at 4 days after PHA stimulation iii) The base composition was similar to that of DNA fragments isolated from DNA/anti-DNA antibody immune complexes These results lead us to propose that guanine cytosine-enriched low mw DNA fragments accumulate in cells after nuclear DNA is degraded, and that these fragments may serve as a primary source of autoantigen for anti-DNA antibody production In addition, they may interfere with normal cellular metabolism
TL;DR: The high percentage of duplex formation, the low standard deviation of relative binding, the elimination of complications resulting from differences in the number of rRNA cistrons in nuclear DNA, make this method preferable to the membrane-filter technique commonly used in phylogenetic classifications based on the homology of large rRNAs.
Abstract: In a new combination of techniques for ribosomal RNA hybridization, complementary DNA is synthesized on 25S ribosomal RNA fragments generated by mild alkali treatment, by the enzymatic addition of polyadenylic acid tails, hybridization of these tails with oligo deoxyribosylthymine, and reverse transcription in the presence of tritiated TTP. Hybridization reactions are performed in solution. Heteroduplexes are collected on diethylaminoethylcellulose filter discs after treatment with S1 nuclease. The problems presented by secondary rRNA structure are avoided by denaturation before reverse transcription and before hybridization. The high percentage of duplex formation (78–87%), the low standard deviation of relative binding (averaging ± 1.00330% relative binding), and small differences in reciprocal hybridizations (1.71–5.18% relative binding), as well as the elimination of complications resulting from differences in the number of rRNA cistrons in nuclear DNA, make this method preferable to the membrane-filt...
TL;DR: An autonomously replicating sequence of Nicotiana tabacum was cloned into the EcoRI site of YIp5, which consists of pBR322 and the yeast ura3 gene, which was capable of transforming ura 3-Saccaromyces cerevisiae YNN140 at 103–104 transformants per μg DNA.
Abstract: An autonomously replicating sequence (ars) of Nicotiana tabacum was cloned into the EcoRI site of YIp5, which consists of pBR322 and the yeast ura3 gene Recombinant DNA was capable of transforming ura3-Saccaromyces cerevisiae YNN140 at 103–104 transformants per μg DNA Transformants had a generation time of 3–4 h in the medium used for selection, in which approximately 30% of the cell retained the Ura+ phenotype after 24 h The average copy number of hybrid plasmids was in the range of 10–20 molecules per cell The size of the inserted DNAs from tobacco nuclear DNA was 49, 30 and 12 kilobase pairs (kbp), of which the 12 kbp insert hybridized to several bands of EcoRI-digested nuclear DNA An EcoRI-generated 17 kbp ars fragment was cloned from tobacco chloroplast DNA
TL;DR: DNA, RNA, protein and heterochromatin were measured cytophotometrically in developing soybean (Glycine max) seeds to interpreted that increased DNA levels in soybean cotyledons generated during embryogeny increase the protein synthesizing capacity.
Abstract: DNA, RNA, protein and heterochromatin were measured cytophotometrically in developing soybean (Glycine max) seeds. The average 2C DNA content for the soybean genome was 2.64 pg. The amounts of nuclear DNA in embryo axes showed no significant change during embryo development, whereas the DNA content in cotyledon nuclei increased significantly from 3.58 pg to 5.49 pg. The number of endopolyploid nuclei increased from 26% to 48% and the DNA content from 4.45 to 5.49 pg after cessation of cell division. The changes in RNA and protein content during embryo development were in general similar to those in DNA content. This can be interpreted that increased DNA levels in soybean cotyledons generated during embryogeny increase the protein synthesizing capacity. During the first 15 days of germination, the number of endopolyploid nuclei in cotyledons declined from 46% to 4%, and this decline is interpreted as DNA degradation providing a ready source of nucleosides and phosphates during early embryo growth. A later decline, however, between 15 and 20 days after germination, was age related similar to leaf senescence, because the percentage of endopolyploid nuclei remained unchanged while the number of non-viable cells increased. In senescing cotyledons, 73% and 80% of RNA and protein but only 20% of DNA were lost, as compared to dormant cotyledons. The heterochromatin (condensed chromatin) measurements indicated that nuclei of metabolically inactive dormant and senescent cotyledon nuclei contained an average of 33% more heterochromatin than nuclei from the green cotyledons of seedlings.