Engineering the Chloroplast Genome to Confer Stress Tolerance and Production of Pharmaceutical Proteins

Abstract

The life-supporting metabolic process of photosynthesis is carried out in endosymbiotic organelles, the chloroplasts. Scientific endeavors over the last decade have enabled us to successfully engineer the chloroplast genome. This singular development has opened new avenues for agricultural biotechnology and has contributed immensely to our understanding of the basic genetic mechanisms operative within the organelle. The chloroplast genome has been engineered to express agronomically important traits such as disease-resistance, drought-tolerance, herbicide-resistance, insect resistance and production of antibodies, biopharmaceuticals and edible vaccines. The ability to hyper-express prokaryotic and eukaryotic proteins without the drawbacks of gene silencing or position effects, combined with the advantage of gene containment due to plastid maternal inheritance, make chloroplast transformation technology both useful and environmentally-friendly. The recent use of a plant-derived selectable marker for chloroplast transformation is an important development that should help allay public fears about GM foods. In addition, the extension of chloroplast transformation technology to edible plant species such as potato and tomato, coupled with the hyper-expression of antigens, opens up the possibility of oral delivery of vaccines and other biopharmaceuticals. This review focuses on some of these recent accomplishments and their impact.