Hereditary variability of plants under the action of exogenous DNA

Summary Injection of exogenous barley donor DNA into grains of barley recipient plants at the milk maturity stage, with a specially designed syringe, led to the appearance of transformed plants. The transformation (in rare cases) was caused by the unsheared DNA since the DNA passing through the syringe needle remained relatively stable (10⁶ to 10⁷ daltons) as was confirmed by DNA sedimentation analysis.14 plants grown from seeds injected with highly polymeric DNA containing close to 30 per cent protein had transformed pollen grains. In the 2nd generation only 2 plants from the 8 studied preserved these changes. In the progeny of these two plants, i.e., in the 3rd seed generation after injection, 82.1 per cent of plants preserved the transformed characters. The next, 4th generation, preserved a transformed phenotype in 89.6 per cent of plants.It was also shown that reversion to a recipient-like state was not always constant. We found the reversion of transformed properties (i.e., normal starch and two-rowed spikes) in 40 per cent of the 4th generation descendants of one of the plants which had lost the phenotypical expression of these properties in the 3rd generation but had them in the 2nd generation.The study of the morphological properties of transformed plants showed that with respect to phenotypic expression some characters were changed towards the donor type, some remained as in the recipients and some were of the intermediate type.     

Incorporation of3H-thymidine into DNA and the activity of alkaline phosphatase in zinc-deficient fetal rat brains

The incorporation of³H-thymidine into DNA in the brains of the 17-day and 20-day old rat fetuses was significantly reduced by maternal zinc restriction during pregnancy. The activity of the enzyme thymidine kinase (EC 2.7.1.21) was similarly reduced in the zine-deprived fetal brains on days 14 and 20 of gestation, but not on day 17. Fetal brain alkaline phosphatase (EC 3.1.3.1) was significantly depressed by maternal zinc deprivation on days 17 and 20 of pregnancy. The data suggest an association between thymidine kinase and the reduced incorporation of³H-thymidine into DNA in the brains of 20-day old fetuses but not in animals on day 17. Alkaline phosphatase was however depressed at this stage. The suggestion is made that because of the complexity of brain development, future biochemical studies in this area should concern specific structures in the brain at particular critical stages during neurogenesis.     

DNA sequence analysis of the defective interfering particles of bacteriophage f1.

Restriction mapping and nucleotide sequence analysis of several defective, interfering particles of bacteriophage f1 are described. These particles contain the nucleotide sequences corresponding to the carboxyl terminus of gene IV and the amino-terminus of gene II and the intergenic space between them. Tandem duplication of a portion of this intergenic space generates defective particles with novel nucleotide sequences not found in wild-type f1. This duplication is shown to contain the origin of complementary strand synthesis. Our results suggest that the duplication occurs at the site of gene II protein action, i.e. the origin of viral strand synthesis. A model is presented for the generation of these duplications in defective particles.     

Mitochondrial mutagenesis in Saccharomyces cerevisiae. III. Nitrous acid.

Nitrous acid (NA) induced mutations efficiently in mitDNA, conferring resistance to erythromycin and weakly induces mit- mutations. In some strains of yeast it also enhanced rho- mutations. The frequencies of nuclear and mitochondrial mutations induced with NA are compared.     

Effect of foliar application of phosphorus on RNA and DNA under salt-stress in peanut plants (Arachis hypogaea L.)

Summary Peanut (Arachis hypogaea L., var. TMV-2) plants were raised in sand cultures salinized with sodium chloride at 0.4% on air dry weight basis. Phosphate was sprayed to the drip point, once daily for five days from 20th to 25th day and from 30th to 35th day. Shoot apices and mature leaves were harvested for nucleic acid analyses at 30th and 40th day, receiving one and two sets of sprays respectively. Salinity decreased RNA and DNA levels which were partially restored by foliar application of phosphate.     

The major DNA polymerase in cultured plant cells: Partial purification and correlation with cell multiplication

A DNA polymerase activity was isolated from cells of Oryza sativa L. grown in suspension culture. Molecular mass ( 180,000), optimal requirements for pH (neutral), Mg²⁺ (5–10 mM), Mn²⁺ (1 mM), template preference (activated DNA), lack of activity with native or denatured DNA, and sensitivity to N-ethylmaleimide and ionic strength are similar to those of the vertebrate -polymerase. Like DNA polymerase , the DNA polymerase described in this work is the most abundant in proliferating cells of Oryza sativa L., Parthenocissus tricuspidata (Siebold et Zucc.) Planchon, Acer pseudoplatanus L., and Medicago sativa L. and responds to changes in the rate of cell multiplication. We therefore postulate that this -like DNA polymerase is the replicating enzyme of plant cells.Abbreviations BSA bovine serum albumin - EDTA ethylendiamino-tetracetic acid - DTT dithiothreitol - PTSF p-toluenesulfonyl fluoride     

Nuclear ultrastructure: Condensed chromatin in plants is species-specific (karyotypical), but not tissue-specific (functional)

Summary In contrast to mammalian cell nuclei those of plants display nearly an identical ultrastructure in all developmental stages and tissues. This indicates that the gross organization of chromatin is species-specific, but not tissue-specific and function-dependent. The species-specific nuclear ultrastructure is determined by the basic nuclear DNA content (2 C value). The higher the DNA content, the more the euchromatin remains in the condensed state during interphase, but to a lower coiling order than the heterochromatin.Some difficulties in the interpretation of electron micrographs of cell nuclei, and the possible role of repetitive DNA sequences in the karyotypical condensation of euchromatin in plants are discussed.     

In vitro construction of a recombinant adenovirus Ad2:Ad5

A hybrid virus containing the left half of the Ad5 genome and the right half of the Ad2 genome has been constructed by ligating together in vitro the BamHI.-A fragment of Ad5 (map co-ordinates 0–59.5) to the-SawHI-A fragment of Ad2 (map coordinates 59.5–100), and using this DNA to transfect susceptible cells. Viable progeny virus has been obtained which grows as well as the parental virus without any requirement for helper virus, and probably contains a hybrid hexon polypeptide consisting of the major part of the Ad5 hexon with an Ad2 carboxy terminus.