Abstract
For most transgenic crops, the purported ecological risk from transgenic-host hybridization and introgression to unintended host species is negligible. Nonetheless, there remains a risk-associated focus on the potential for gene flow in the governance and regulation of crop biotechnology. Because of uncertainties in the large world of biology as well as regulatory certainties (regulations will likely not diminish), researchers and stakeholders have a great interest in eliminating or substantially decreasing gene flow from transgenic crops. To that end, numerous approaches have been investigated for limiting transgene flow via hybridization and introgression to unintended hosts. While such bioconfinement may be accomplished by ecological and management strategies as discussed elsewhere in this book, this chapter focuses on mitigating unintended gene flow from engineered crops by way of genetic engineering itself. The chapter will mainly discuss the manipulation of relatively simple means to alter plant sexual reproduction and plant growth and development to control transgene flow, with the desired outcome being the prevention of transgenes from moving and/or introgression into free-living unintended hosts. These approaches include: (i) decreasing or delaying flowering; (ii) eliminating pollen production via male sterility or selective male sterility; (iii) removing transgenes from pollen or eggs by gene use restriction technologies; and (iv) kill switches. Emerging synthetic biology approaches that may be used for transgene bioconfinement are explored. Taken together, the same molecular biology strategies that are used to improve crops can also help assure their biosafety.