Suppression of somatic crossing over in Glycine max (L.) merrill by deoxyribose cytidine

International Commission for Protection Against Environmental Mutagens and Carcinogens. Deoxyribonucleoside triphosphate levels: a critical factor in the maintenance of genetic stability

DNA precursor pool imbalances can elicit a variety of genetic effects and modulate the genotoxicity of certain DNA-damaging agents. These and other observations indicate that the control of DNA precursor concentrations is essential for the maintenance of genetic stability, and suggest that factors which offset this control may contribute to environmental mutagenesis and carcinogenesis. In this article, we review the biochemical and genetic mechanisms responsible for regulating the production and relative amounts of intracellular DNA precursors, describe the many outcomes of perturbations in DNA precursor levels, and discuss implications of such imbalances for sensitivity to DNA-damaging agents, population monitoring, and human diseases.

Soybean (Glycine max [L.] merrill) as a short-term assay for study of environmental mutagens. A report of the U.S. Environmental Protection Agency Gene-Tox Program

The soybean (Glycine max [L.] Merrill) spot test is suggested as a preliminary screening test for environmental mutagens. This system makes use of various types of spots that originate from the treatment of seeds or seedlings with mutagens. The homozygous dominant y11y11 dark green leaves may show light green and very dark green spots; the heterozygous y11y11 light green leaves may show dark green, yellow or twin spots; and the homozygous recessive y11y11 yellow leaves show light green receptors. The interpretation is that twin spots on the y11y11 leaves originate from somatic crossing-over, and the singles originate primarily from losses or gains of the segments or chromosome carrying the gene y11 or y11. The yellow plants (y11y11) can produce light green sectors if y11 mutates to y11. Studies carried out with a host of chemical and physical agents lend support to the idea that the soybean system can distinguish between several genetic mechanisms underlying the formation of spots. Spots are detected against their native genetic and phenotype background, thus minimizing the effects due to physiological changes. The system is rapid (4-5 weeks per chemical), inexpensive, and involves an eukaryotic organism. It has the advantage of being adaptable for liquid solutions of chemicals, solid wastes, emulsions of chemicals (e.g., in lanolin), and gaseous products.

Mutagens in a river heavily polluted with paper recycling wastes: results of field and laboratory mutagen assays

Paper recycling industries generate considerable quantities of waterborne wastes, and thus water pollution constitutes the greatest environmental problem associated with this industrial activity [Hunt and Franklin, 1973]. Generally the impact of this water pollution is considered in terms of aesthetic blight and deterioration of water quality. We present data that document another aspect of this pollution, the environmental contamination of an aquatic ecosystem with mutagenic materials. A natural population of the fern Osmunda regalis growing in a river heavily polluted with paper recycling wastes had a high incidence of chromosome mutations. This population was monitored for four years for the frequency of two-break chromosome mutations. These mutations were postzygotic in origin and suggested the presence of mutagens in the river water. The fern population is downstream from the outfalls of a paper recycling mill, which was discharging 13.3 X 10(6) liters of untreated paper recycling waste per day. In 1977 a waste-water-treatment facility was constructed to remove the solid waste previously discharged into the river. This facility generates 69,300 kg of solid waste daily, which is taken to a landfill. Periodic samples of this solid waste were collected from the waste-treatment facility in the summer of 1978, extracted with various solvents, and the extracts tested for mutagenic activity with the Salmonella/mammalian microsome mutagenicity test [Ames et al, 1975]. A majority of the solid waste samples contained mutagenic materials, but in all cases S-9 activation was required for mutagenic activity. The samples also were assayed with the soybean mitotic crossing-over assay [Vig, 1975]. Four out of six samples were positive. These results document the presence of mutagens in the solid waste generated by a paper recycling industry and the genetic impact of these mutagens on the local biota.

Somatic crossing over in Glycine max L. (Merrill): sensitivity to and saturation of the system at low levels of tritium emitted beta-radiation

Seeds of varieties L65-1237 and T219 of soybean were soaked in 20-50 ml of tritiated water (HTO) containing between 0.01 and 50 μCi/ml of tritium (T) for various periods from 24 to 142hr. Genetic damage was determined by counting the number of Y11Y11-y11y11 spots on the Y11y11 leaves. No effect was noticeable in treatments lasting up to 24hr independent of the concentration. However, somatic crossing over occurred when the seeds were treated with tritium for 92 hr or longer even with concentrations as low as 0.01 μCi/ml. The data indicate that the soybean system being used is sensitive to very low doses of beta radiation. The damage to the seeds treated with the lowest concentration was not significantly different in quality or quantity from that induced by higher concentrations. This indicates some type of saturation effect to tritium-emitted beta radiation. Analytical results showed that synthesis of organic matter and incorporation of tritium into the organic fraction was delayed until about 96 hr after the imbibition was started. This indicates a relationship between spot induction by tritium and organic synthesis.