Keith Redenbaugh

Commercialization of a tomato with an antisense polygalacturonase gene: The FLAVR SAVR™ tomato story

The FLAVR SAVR™ tomato was developed through the use of antisense RNA to regulate the expression of the enzyme polygalacturonase (PG) in ripening tomato fruit. This enzyme is one of the most abundant proteins in ripe tomato fruit and has long been thought to be responsible for softening in ripe tomatoes. The FLAVR SAVR™ tomato is the first genetically engineered whole food to be sold in commerce. The history of the development of this product is discussed beginning with the results of theoriginal antisense work (including conclusions regarding the role of PG in ripe tomatoes) and will be followed by a description of the regulatory and food safety assessment. Finally, the development of an operating business to produce, market and distribute a genetically engineered whole food product is discussed.

Artificial seeds for plant propagation

Abstract Artificial seeds consisting of tissue-culture produced embryos encased in a protective coating, will allow the economical mass propagation of elite plant varieties. They would also be a channel for new plant lines produced through biotechnological advances to be delivered directly to the greenhouse or field.

Alfalfa somatic embryo maturation and conversion to plants

Abstract Maturation of somatic embryos of alfalfa ( Medicago sativa L.) on medium containing abscisic acid (ABA) prior to planting increased plant formation from somatic embryos (‘conversion’) from 0% to 80% under growth chamber conditions. The embryos were planted directly into soil potting mix under non-sterile conditions without any exogenous nutrients. There was a positive correlation of increased conversion frequency and high embryo fresh/dry weights, dry matter content and starch levels when the somatic embryos were matured on ABA medium. Starch grains were present in the cotyledons and axis of somatic embryos that were ABA-matured and absent in embryos that did not receive the ABA treatment. ABA may be promoting somatic embryo storage reserve accumulation necessary for high conversion and vigor in the soil environment.

Maturation and greenhouse planting of alfalfa artificial seeds

SummaryConversion (plant production) was obtained from direct-planting alfalfa somatic embryos and encapsulated somatic embryos (artificial seeds) of alfalfa into a growth chamber and greenhouse. The embryos were planted in a commercial soil potting mix under nonsterile conditions in a manner similar to zygotic seed. Embryo maturation with abscisic acid (ABA), prior to planting, gave 48% conversion in soil under growth chamber conditions. Under greenhouse conditions, 64% conversion was obtained when humidified air was used to prevent soil surface drying. Previously, conversion in soil was between 0–6% without the ABA maturation treatment. The replacement of ABA with mannitol or combinations of mannitol and ABA during maturation resulted in lower conversion in the growth chamber than with ABA alone. ABA may be promoting the accumulation of embryo storage reserves such as proteins and carbohydrates for growth after planting in the soil environment.

FIELD PLANTING OF ALFALFA ARTIFICIAL SEEDS

SummaryEncapsulated somatic embryos (artificial seeds) and naked (uncoated) somatic embryos of alfalfa (Medicago sativa L.) were planted directly into the field to demonstrate the feasibility of using artificial seeds for direct sowing. Various row coverings that provided protection for the somatic embryos during conversion (plant formation) in the field and encapsulation methods were investigated. The highest conversion obtained in the field was 25% when naked somatic embryos were planted under the protective covering of inverted styrofoam cups. In comparison, 60% conversion was obtained when embryos were planted in potting mix in a growth chamber. Somatic embryos encapsulated by the thin-coat method converted at 23% under cups in the field and 40% in potting mix in the growth chamber. Naked somatic embryos had an average of 13 and 9% conversion in the field under plastic and cloth coverings, respectively, whereas encapsulated embryos converted at 5 and 14%, respectively. Direct-planted embryos (no row covering) converted at 1% in the field. Successful conversion of coated and naked somatic embryos planted in the field supports the concept of artificial seeds serving as a substitute for natural seeds.

Regulatory assessment of the FLAVR SAVR tomato

Abstract This article provides a case study of the FLAVR SAVR☆m tomato as a demonstration of the regulatory procedures and safety assessment necessary in the USA. The data generated demonstrate that FLAVR SAVR tomatoes do not significantly differ from traditionally bred tomato vareities, are functionally unchanged except for the intended effects of the FLAVR SAVR and kan genes, and as such remain a food and subject to regulation as a food. The US Food and Drug Administration is considering the safety of the FLAVR SAVR tomato in a Request for Advisory Opinion. This tomato is expected to be the first genetically engineered whole food on the market.

Artificial seeds: A method for the encapsulation of somatic embryos

A detailed description of alfalfa (Medicago sativa L.) somatic embryogenesis and methods to produce alfalfa artificial seeds are described. These protocols provide directions for producing alfalfa artificial seeds that will convert into whole plants when planted in vitro or directly into soil.

Regulatory issues for commercialization of tomatoes with an antisense polygalacturonase gene

SummarySignificant progress has been made in development of transgenic plants containing agriculturally useful genes. Concurrent with scientific advances has been development of a regulatory infrastructure within the U.S. Department of Agriculture (USDA) for assessing safety of controlled release of genetically engineered plants into the environment, as well as creation of a food policy by the Food and Drug Administration (FDA). Field trials and safety assessments of tomato containing an antisense polygalacturonase gene (FLAVR SAVR™ tomato) have been conducted. A detailed safety analysis of thekanr selectable marker was also done. Based on these data plus nutritional measurements, lack of changes in levels of natural toxins, and lack of any unintended changes, we have requested that the USDA and FDA determine that this genetically engineered tomato is safe for release into the environment and human consumption.