Selectable Marker Genes in Chloroplast Genetic Transformation

Incorporation of a selectable marker gene during chloroplast genetic transformation is essential to obtain transformed chloroplasts, which is the same as nuclear transformation. Although many selective marker genes have been used in chloroplast transformation, it is obviously different from the nuclear transformation because of its specific structure and inheritance. Therefore, selection and utilization of the right selectable marker genes are very important to chloroplast transformation. Since most selectable marker genes in chloroplast transformations are antibiotic resistance genes which might threaten the human beings, it is a hotspot to explore strategies for getting rid of the dependence on antibiotic resistance genes. Progress on selective marker genes of chloroplast genetic transformation is reviewed; especially the antibiotic-free selective marker—betaine aldehyde dehydrogenase (BADH) and the marker elimination system are discussed.