DNA-protein relations during microsporogenesis of Tradescantia

Basic proteins of plant nuclei during normal and pathological cell growth

Histone proteins were studied by microphotometry of plant tissue sections stained with fast green at pH 8.1. For comparative purposes the Feulgen reaction was used for deoxyribose nuclei acid (DNA); the Sakaguchi reaction for arginine; and the Millon reaction for estimates of total protein. Analysis of Tradescantia tissues indicated that amounts of nuclear histone fell into approximate multiples of the gametic (egg or sperm) quantity except in dividing tissues, where amounts intermediate between multiples were found. In differentiated tissues of lily, corn, onion, and broad bean, histones occurred in constant amounts per nucleus, characteristic of the species, as was found also for DNA. Unlike the condition in several animal species, the basic proteins of sperm nuclei in these higher plants were of the histone type; no evidence of protamine was found. In a plant neoplasm, crown gall of broad bean, behavior of the basic nuclear proteins closely paralleled that of DNA. Thus, alterations of DNA levels in tumor tissues were accompanied by quantitatively similar changes in histone levels to maintain the same Feulgen/fast green ratios found in homologous normal tissues.

Developmental strategies of the angiosperm pollen: a biochemical perspective

The current state of our knowledge of the biochemistry and biochemical cytology of normal pollen development and embryogenic transformation of pollen grains of cultured anthers of angiosperms is reviewed. Recent research shows that normal pollen development is characterized by gene activity for the synthesis of specific mRNAs associated with the gametophytic program. As a result of the trauma of excision and culture of anthers in a mineral salt medium, a small number of the enclosed pollen grains probably synthesize new mRNAs which code for the proteins involved in embryogenic divisions. Since these conclusions are based on the study of a small number of species, the need for sustained investigations on the molecular biology of pollen developmental transformations is emphasized.

Cytophotometric study of nuclear differentiation during pollen development in Tradescantia paludosa

During pollen development the dry weight, total protein, histone, DNA, arginine, and lysine content were analysed by cytophotometric methods in partially isolated nuclei. The amount of analysed substances increased from the end of the meiosis to the mitosis of the microspores to the double of the initial values. After mitosis the ratio histone/DNA remained almost unchanged in both vegetative and generative nuclei. On the other hand a large difference in the ratio non-histone protein/DNA could be observed, the vegetative nucleus containing more non-histone protein than the generative nucleus. The rate of RNA synthesis being higher in the vegetative nuclei, these non-histone proteins may have some function in nuclear activation. The DNA of the generative nucleus is duplicated before anthesis, whilst in the vegetative nucleus the DNA content remains constant.

[The development of pollen grains and formation of pollen tubes in higher plants : III. DNA-replication of vegetative and sperm nuclei in mature pollen grains of barley]

The DNA-content of vegetative and sperm nuclei in mature pollen grains of the barley varieties Amsel and Wisa and the F1-plants of crossings of the barley varieties Impala X Wisa and Union X Wisa was determined by cytophotometry. In addition, the DNA-content of nuclei of root tips of Amsel and Wisa was cytophotometrically measured.The DNA contents of the nuclei in root tips of Amsel and Wisa differed significantly.The data obtained from the measurements of the vegetative and sperm nuclei of the four types of barley show that DNA-replication continues in the nuclei of mature pollen grains. The DNA values of vegetative nuclei of Wisa are significantly lower than the values of Amsel and of the F1 plants. The DNA values of the different nuclei indicate that DNA replication of both types of sperm nuclei is synchronous, whereas it probably is not synchronous in vegetative and sperm nuclei respectively.In the discussion it is pointed out that a survey of the literature shows that in all of the plant species having binucleate or trinucleate pollen DNA replication of generative and of sperm nuclei has started at the time of pollen grain maturation. Depending on the plant species, replication may or may not be completed in the mature pollen grain. At a given stage of development of the pollen grain the vegetative nucleus may be arrested at the C-stage, may have partially or completely finished its DNA replication or may be partially or completely degenerated without prior replication of DNA.In the second part of the discussion it is stated that the course of DNA replication is likely to be similar in binucleate and trinucleate pollen grains. Thirdly, the hypothesis is discussed that in order to get haploid plants from pollen grains, changes in the normal development of the pollen grain and in the pattern of DNA replication must occur at a very early stage of pollen grain development.

[Studies on the significance of vegetative nuclei and their nucleoli in pollen grains and pollen tubes]

The communication deals with a study of the significance of vegetative nuclei of pollen grains. The study of vegetative nuclei was performed with pollen grains and pollen tubes of a tulip (Tulipa gesneriana, var. Bellona).The conclusions are summarized as follows: 1. The vegetative nucleus does not participate directly in the regulation of growth of the pollen tubes. 2. Stimulation of the growth of pollen tubes induced by means of boric acid is not accompanied by a simultaneous stimulation of spiralization of chromosomes in the generative nucleus or by its division. 3. The vegetative nucleus and its nucleolus take part in the division of the generative nucleus. 4. In the course of spiralization of the chromosomes of the generative nucleus, the nucleolus disappears from the vegetative nucleus. The vegetative nucleus, however, persists in spite of a decrease in DNA content. 5. The vegetative nucleus disappears after formation of spermatic nuclei.

Microspectrophotometry of cell nuclei stained with the Feulgen reaction. IV. Formation of tetraploid nuclei in rat liver cells during postnatal growth

1. DNA contents of the individual parenchymal nuclei of rat livers during postnatal growth were estimated by microspectrophotometric apparatus, and different ploidy classes of nuclei were classified by their DNA contents. With the same material the total number of parenchymal nuclei in the liver was counted microscopically. 2. If the DNA content of nuclei encountered most frequently in several tissues represents the diploid class, the ploidy classes of the rat liver cell nuclei correspond to di-, tri-, tetra-, and octoploid, with the di- and tetraploid ones predominating considerably. 3. In suckling rats (below 25 gm. of body weight) the liver parenchyma is composed almost exclusively of cells with diploid nuclei, whereas in young rats (above 80 gm.), of tetraploid nuclei. In the growth stage between 25 and 80 gm., there is a remarkable replacement of the diploid nuclei by the tetraploid ones. However, in the liver of adult rats weighing more than 150 gm., any increase or decrease in the frequency of diploid and tetraploid nuclei is hardly observable. In such rats, the nuclear population of the liver parenchyma seems to reach a cell-ecological equilibrium which is considered to be a stable one. 4. It is shown that such nuclear populations and the total number of nuclei in a liver are controlled by the growth state, and not by the age. 5. The decrease in the total number of diploid nuclei and the increase in tetraploid nuclei in the growing livers of rats weighing from 40 up to 130 gm. can both be explained by the hypothesis that the tetraploid nuclei originate from the interphase diploid nuclei without involving mitosis. This hypothesis implies that mitosis is confined to the reproduction of diploid cells alone. 6. It is suggested that, in general, the synthesis of DNA does not necessarily result in the formation of visible mitotic chromosomes. 7. Mitotic time and generation time of diploid nuclei and the percentage of the tetraploidization from diploid nuclei are calculated and discussed.

Biochimica Dei Tessuti Iperplastici: Modificazioni Del Metabolismo Cellulare Indotte Dalla Rigenerazione Epatica

The dynamic cell processes connected with liver regeneration have been studied as follows: 1) ribonucleic and desoxyribonucleic contents; 2) transamination reactions (glutamic-oxalacetic transaminase and glutamic-piruvic transaminase); 3) reactions related to the peptides constitution and demolition (dipeptidase); 4) reactions involved in the hydrolytic release of phosphoric bounds (alkaline phosphomonoesterase, acid pyrophosphatase, gluco-6-phosphatase); 5) reactions entering in nucleotides splitting and formation (nucleotidase).

It has been particularly observed that the metabolic differences between normal and regenerating liver are mainly quantitative and that the enhancement of proteosynthesis does not necessarily imply a simultaneous enhancement of all the related biochemical activities.

DNA in gametogenesis and embryogeny in Tradescantia

A microphotometric study of various Feulgen-stained gametophytic and sporophytic nuclei of Tradescantia paludosa was made to test the hypothesis that DNA is maintained in multiples of a basic unit within all cells of an organism. A multiple relationship was found in all tissues analyzed. The lowest amount of DNA was found in gametophytic nuclei, approximately twice and four times this amount in sporophytic nuclei, and approximately three and six times this amount in endosperm nuclei. Intermediate amounts of DNA were found only in tissues presumably undergoing an interphase synthesis of DNA preceding either cell division or endomitosis. It is concluded that within the limitations of present methods of measurement, DNA amounts show a quantitative behavior which supports the "constancy" hypothesis. Such quantitative stability of DNA gives support to the concept that DNA is associated with the stable elements of the gene.