Molecular strategies for gene containment in transgenic crops

Abstract

The potential of genetically modified (GM) crops to transfer foreign genes through pollen to related plant species has been cited as an environmental concern. Until more is known concerning the environmental impact of novel genes on indigenous crops and weeds, practical and regulatory considerations will likely require the adoption of gene-containment approaches for future generations of GM crops. Most molecular approaches with potential for controlling gene flow among crops and weeds have thus far focused on maternal inheritance, male sterility, and seed sterility. Several other containment strategies may also prove useful in restricting gene flow, including apomixis (vegetative propagation and asexual seed formation), cleistogamy (self-fertilization without opening of the flower), genome incompatibility, chemical induction/deletion of transgenes, fruit-specific excision of transgenes, and transgenic mitigation (transgenes that compromise fitness in the hybrid). As yet, however, no strategy has proved broadly applicable to all crop species, and a combination of approaches may prove most effective for engineering the next generation of GM crops.

Figure 1

Potential strategies for restricting gene flow. (A) By restricting flower opening and floral development (cleistogamy) in a GM crop, pollen dispersal and outcrossing could be prevented, thereby mitigating gene flow. (B) Gene flow through pollen could be restricted via chloroplast engineering, male-sterility approaches (including tapetum-specific excision of transgenes), and genome incompatibility. (C) Gene flow through seeds could be restricted by seed-sterility approaches (including seed-specific excision of transgenes) and apomixis.