Applying knowledge and experience from potato (Solanum tuberosum) to update genetic stability data requirements in the risk assessment for vegetatively propagated biotech crops.

Regulatory agencies require data on genetic stability as part of the safety assessment for biotech crops, even though the genetic stability of a plant is not necessarily an environmental, human or animal health safety concern. While sexual reproduction has the potential to introduce genomic variation in conventionally bred and biotech crops, vegetative propagation is genetically stable. In vegetatively propagated crops, meiosis does not occur thus limiting the number of homologous recombination events that could lead to chromosomal rearrangements in progeny plants. Genetic stability data is often, but should not be, an automatic requirement for the safety assessment of vegetatively propagated biotech crops. Genetic stability data from biotech potato events has demonstrated that vegetative propagation of potato tubers does not affect the stability of introduced DNA sequences or lead to loss of trait efficacy. The knowledge and experience gained from over 30 years of assessing the safety of biotech crops can be used by regulatory authorities to eliminate data requirements that do not address environmental, food or feed safety concerns. As a first step, regulators should consider removing requirements for genetic stability as part of the safety review for vegetatively propagated biotech crops.

Improving regulatory efficiency for biotechnology products.

Small procedural changes in how regulatory agencies implement biotech policies can make significant differences in improving regulatory efficiency. This paper discusses how science based, crop specific guidance documents can improve dossier content and the review and approval of biotech varieties. In addition, we describe how the adoption of established risk assessment methodology and applying policy-linked decision making at the agency level can boost both efficiency and developer, public and government confidence in agency decision making and in biotech crops.

Safety evaluation of E12, W8, X17, and Y9 potatoes: Nutritional evaluation and 90-day subchronic feeding study in rats.

The nutritional and health effects of four biotech potato events, E12, W8, X17, and Y9, were evaluated in a subchronic rodent feeding study. E12 contains pSIM1278 insert DNA derived from potato and designed to down regulate potato genes through RNAi. These changes result in reduced black spot and reduced acrylamide. W8, X17, and Y9 contain the DNA inserts from pSIM1278 and pSIM1678 to further reduce acrylamide and express a gene from wild potato that protects against late blight. Rats were fed diets containing 20% cooked, dried potatoes from these four events and three conventional potato varieties. Compositional analyses of the processed potatoes and the rodent diets demonstrated comparability between the four events and their respective conventional varieties. Rats consumed the diets for 90 days and were evaluated for body weight, dietary intake, clinical signs, ophthalmology, neurobehavioral parameters, clinical pathology, organ weights, gross pathology, and histopathology. No adverse effects were observed as a result of test diet consumption. These results support the conclusion that foods containing E12, W8, X17, or Y9 potatoes are as safe, wholesome and nutritious as foods from conventional potato varieties.

Compositional safety of herbicide-tolerant DAS-81910-7 cotton.

DAS-81910-7 cotton is a transgenic event that was transformed to contain the aad-12 and pat genes. These genes code for the AAD-12 and PAT proteins, which confer tolerance to the herbicides 2,4-D and glufosinate, respectively. Crop composition studies were conducted with DAS-81910-7 cotton (both nonsprayed and sprayed with 2,4-D and glufosinate) to comply with requirements of regulatory authorities responsible for evaluating crop safety. Results indicate compositional equivalence between DAS-81910-7 cottonseed and nontransgenic cottonseed and between sprayed and nonsprayed DAS-81910-7 cottonseed. This study builds on the results from many prior studies which support the conclusion that transgenesis is less likely to unexpectedly alter the composition of crops as compared with traditional breeding.

Meiotic transmission of an in vitro-assembled autonomous maize minichromosome.

Autonomous chromosomes are generated in yeast (yeast artificial chromosomes) and human fibrosarcoma cells (human artificial chromosomes) by introducing purified DNA fragments that nucleate a kinetochore, replicate, and segregate to daughter cells. These autonomous minichromosomes are convenient for manipulating and delivering DNA segments containing multiple genes. In contrast, commercial production of transgenic crops relies on methods that integrate one or a few genes into host chromosomes; extensive screening to identify insertions with the desired expression level, copy number, structure, and genomic location; and long breeding programs to produce varieties that carry multiple transgenes. As a step toward improving transgenic crop production, we report the development of autonomous maize minichromosomes (MMCs). We constructed circular MMCs by combining DsRed and nptII marker genes with 7-190 kb of genomic maize DNA fragments containing satellites, retroelements, and/or other repeats commonly found in centromeres and using particle bombardment to deliver these constructs into embryogenic maize tissue. We selected transformed cells, regenerated plants, and propagated their progeny for multiple generations in the absence of selection. Fluorescent in situ hybridization and segregation analysis demonstrated that autonomous MMCs can be mitotically and meiotically maintained. The MMC described here showed meiotic segregation ratios approaching Mendelian inheritance: 93% transmission as a disome (100% expected), 39% transmission as a monosome crossed to wild type (50% expected), and 59% transmission in self crosses (75% expected). The fluorescent DsRed reporter gene on the MMC was expressed through four generations, and Southern blot analysis indicated the encoded genes were intact. This novel approach for plant transformation can facilitate crop biotechnology by (i) combining several trait genes on a single DNA fragment, (ii) arranging genes in a defined sequence context for more consistent gene expression, and (iii) providing an independent linkage group that can be rapidly introgressed into various germplasms.