Green biotechnology offers tremendous possibilities for the improvement of crop plants by the introduction of new
traits beyond the limit of crossing barriers. Selection markers are necessary for selection of genetically modified
plants during the transformation and regeneration process. Many of the conventional selection markers are of
bacterial origin and provide growth advantages for the recipient plant in the presence of toxic selective agents, such
as antibiotics and herbicides. The bacterial origin of these markers together with their ability to inactivate
antibiotics fosters public concerns that horizontal gene transfer from transgenic plants to bacterial human pathogens
contributes to the generation of antibiotic-resistant strains. Although those concerns in most cases lack a sound
scientific basis, they nevertheless hinder public acceptance of green biotechnology and contribute to political
opinion making against it.
One way to counteract these concerns is the development of selection markers that are of plant origin. The project
application investigates the applicability of plant-encoded in contrast to bacterial-encoded antibiotic resistance as
an alternative selection marker. In the plant model Arabidopsis thaliana this resistance is induced by loss-of-
function of a putative chloroplast protein. The loss- or reduction-of-function can also be induced by RNA
interference (RNAi). This project deals with the application of this novel selection technology in other plants and
its integration into different transformation protocols. Further, the possibility to regulate RNAi-mediated resistance
induction with controlling elements (promoters and terminators) of plant-origin will be addressed. Finally, the
mechanism of RNAi targeted to potential chloroplast transit sequences will be investigated in more detail, which,
according to preliminary results, is different from the normal RNAi mechanism.