Modified Ethylene Signaling as an Example of Engineering for Complex Traits: Secondary Effects and Implications for Environmental Risk Assessment

Abstract

The next wave of genetically engineered crops will use genes that modify gene regulation, plant metabolism, or signal transduction. The potential for these genes to have cascading effects on metabolism, physiology, and development increases the possibility for unintended effects that influence crop performance or environmental impact. This review examines altered ethylene signaling as an example of a complex trait with many horticultural applications. Genes for modified ethylene production or perception intended to regulate ripening, senescence, or stress or disease resistance have been observed to cause a broad range of secondary effects, including modified growth and development and increased severity to biotic and abiotic stresses. Successful use of complex traits in crop varieties will frequently require methods to reduce secondary effects, including the use of targeted gene expression. Risk assessment will need to consider observed pleiotropic effects on fitness within the context of potential environmental impacts.