Search PubMed⌕ Search

Biomedical subjects

P R Day

Publications and source records attributed to P R Day.

17 recordsLinked to original sources
PubMed2003

Using empirical data to model transgene dispersal.

One element of the current public debate about genetically modified crops is that gene flow from transgenic cultivars into surrounding weed populations will lead to more problematic weeds, particularly for traits such as herbicide resistance. Evolutionary biologists can inform this debate by providing accurate estimates of gene flow potential and subsequent ecological performance of resulting hybrids. We develop a model for gene flow incorporating exponential distance and directional effects to be applied to windpollinated species. This model is applied to previously published data on gene flow in experimental plots of Agrostis stolonifera L. (creeping bentgrass), which assessed gene flow from transgenic plants resistant to the herbicide glufosinate to surrounding non-transgenic plants. Our results show that although pollen dispersal can be limited in some sites, it may be extensive in others, depending on local conditions such as exposure to wind. Thus, hybridization under field conditions is likely to occur. Given the nature of the herbicide resistance trait, we regard this trait as unlikely to persist in the absence of herbicide, and suggest that the ecological consequences of such gene flow are likely to be minimal.

Agrostis↗
PubMed2002

Expression of pokeweed antiviral proteins in creeping bentgrass.

Fungal diseases of creeping bentgrass, an important amenity grass used extensively on golf courses, are a serious problem in golf course management. Transgenic approaches to improving disease resistance to fungal diseases are being explored in many species, and in some cases ribosome-inactivating proteins have been found to be effective. We have generated transgenic creeping bentgrass plants expressing three forms of ribosome-inactivating proteins from pokeweed, which are termed pokeweed antiviral proteins (PAP). PAP-Y and PAP-C are nontoxic mutants of PAP; PAPII is the native form of another ribosome-inactivating protein from pokeweed. In creeping bentgrass, PAP-C transformants did not accumulate the protein, suggesting that it is unstable, and in a field test these plants were not protected from infection by the fungal pathogen Sclerotinia homoeocarpa, the causal agent of dollar spot disease. PAPII transformants could accumulate stable levels of the protein but had symptoms of toxicity; one low-expressing line exhibited good disease resistance. PAP-Y transformants accumulated stable levels of protein, and under greenhouse conditions they appeared to be phenotypically normal.

Agrostis↗
PubMed1996

Genetic modification of proteins in food.

Plant breeders have been extremely successful in improving the quality and yield of the major crops, while maintaining the safety of the food supply. This success has been achieved with very little understanding of the biochemical mechanisms that determine the selected traits. Each time a cross is made, tens of thousands of genes are mixed and reassorted, largely at random. The skill of the breeder lies in selecting the lines to be crossed and recognizing the preferred progeny, discarding those that lack the desirable trait or exhibit undesirable properties. With the advent of recombinant DNA technology, breeders have not only extended the range of biological materials from which genes can be accessed, but have also gained new insights into genome organization and gene structure as well as the nature and function of the proteins that those genes encode. Such knowledge affords exquisite specificity in altering the genetic makeup of new crop varieties. For example, resistance to insect pests can now be achieved through the addition of a single well-characterized gene, instead of introducing thousands of unwanted genes from a wild relative that code for uncharacterized and possibly toxic proteins that must be eliminated by generations of backcrossing and screening to recover a commercially acceptable insect-resistant line. The technology also affords unique opportunities to identify the individual components of foods that may cause allergies, and to remove them from food, or change them, so that the food can be consumed safely. A number of commercial products derived through genetic engineering have been approved through regulatory processes that address environmental and food safety concerns. These products are available, or will shortly be available, to growers, producers, and consumers. They will provide foods and feeds that are produced with fewer chemical inputs and have improved nutritional composition and quality.

Biotechnology↗
PubMed1996

Genetic modification of plants: significant issues and hurdles to success.

Transformation and regeneration is routine for many crop plants. A genetically engineered tomato with a longer shelf life at full ripeness was introduced in the United States in 1994, and other soon-to-be-released products, both foods and fibers, incorporate genes for resistance to pests, diseases, and environmentally benign herbicides. Other possibilities are altered plant fats and oils, methionine- and lysine-enhanced grain and legume proteins, plant foods that can deliver immunizing antigens, and other ways of controlling fruit ripening. Food safety concerns include the inadvertent production of toxicants and allergens. Foreign DNA can be introduced into plants by bacterial vectors, direct uptake by protoplasts, and mechanical introduction on metal particles or other materials. Limitations include little or no control of copy number or site of integration of the introduced DNA, dependence on selectable markers for recovery of traits, and inadequate knowledge of how to control key metabolic steps to maximize desirable traits. Directed genetic change still requires conventional crop breeding to deliver benefits to farmers and consumers.

6-Phytase↗
PubMed1976

Inheritance of killer phenotypes and double-stranded RNA in Ustilago maydis.

Three different killer specificities in U. maydis are inherited cytoplasmically and transmitted by cell fusion. Each killer generates low frequencies of specifically immune forms in crosses with sensitive strains. The properties of immunity to each killer are also inherited cytoplasmically and transmitted by cell fusion. Killer strains carry virus-like particles about 41 nm in diameter. Each killer possesses distinct double-stranded RNA components that range in molecular weight from 0.46 X 10(6) to 2.9 X 10(6). Two components are shared by all three killers. Immune strains possess new forms. Crosses and heterokaryons between different killers revealed unilateral or mutual restrictions that prevent inclusion of two killer specificities in the same cell.

Basidiomycota↗
PubMed1976

Suppression of the killer phenotype in Ustilago maydis.

Nineteen sensitive cell lines of U. maydis were crossed with three killer strains and sample progenies were screened for killer segregation patterns. Crosses involving 11 lines gave killer frequencies ranging from 71%-100% of the progeny and 4:0 segregations in tetrads. Segregations in some crosses involving each of the remaining 8 lines gave killer frequencies from 0%-58% and mixed tetrads containing both non-killer and killer meiotic products. Many of the killers were unstable on further culture. Killer suppression showed varying degrees of specificity, appeared to be cytoplasmically determined for at least one strain, and was associated with possession of dsRNA in this strain and one other. No dsRNA was detected in two other suppressive strains. There was no evidence for segregation of nuclear maintainer genes for any of the killer determinants.

Basidiomycota↗
PubMed1972

Simple dye release assay for determining cellulolytic activity of fungi.

A colorimetric assay, based on the release of dye from a paper substrate, is described as a simple and rapid means of detecting cellulolytic activity. It is readily adaptable to rapidly screening in situ large numbers of fungal liquid cultures. Since it is a nondestructive assay, samples can be recovered for later use.

Cellulose↗
PubMed1971

Pathogenicity resulting from mutation at the b locus of Ustilago maydis.

This paper explores the genetic basis of the ability of the fungus, Ustilago maydis, to induce neoplastic galls in the corn plant (Zea mays). Pathogenic mutants of U. maydis were produced by ultraviolet irradiation of cultures of nonpathogenic diploids homozygous at the b locus. The mutants formed smaller neoplasms, produced fewer teliospores, and showed higher frequencies of meiotic failure and lower rates of basidiospore survival than did the wild-type fungus.

Basidiomycota↗