The Safety Assessment of Transgenic Plants in which Gene Expression Has Been Modified

Engineered crops have become a significant component of modern agriculture. Prior to release for commercial planting, a thorough pre-market regulatory review focuses on any potential agricultural and environmental impacts of genetically engineered crops, as well as any differences in food safety that may be associated with the introduction of novel genes and their products. The regulatory review process is a comparative one in which differences between a new transgenic crop variety and its conventional counterparts are assessed, followed by a determination if any changes that have occurred have introduced new risks or heightened existing risks. To date, the great majority of transgenic cultivars that have passed regulatory review contain genes that encode proteins that confer desired novel traits such as insect or herbicide resistance. Alteration of endogenous gene expression can be an alternative method of producing useful phenotypes in plants. For example, RNA-associated mechanisms can be used to switch off genes, while up-regulation of specific transcription factors can be used to enhance expression and thereby modify a plant’s growth or response to stress. Since neither of these two mechanisms necessarily depends on the expression of a new heterologous protein(s), it is reasonable to ask if the safety assessment paradigm developed for and applied to transgenic plants that express novel proteins is appropriate for genetically engineered plants in which gene expression has been altered. This article briefly summarizes the conclusions of a recent paper1 that examines the suitability of the currently used comparative safety paradigm to crops in which gene expression has been altered. Parrott et al. (2010) also serves as an up-to-date review of the safety assessment process.