Stable expression of a biodegradable protein-based polymer in tobacco chloroplasts.

Bioelastic protein-based polymers (PBP) have several medical (prevention of post-surgical adhesions) and non-medical (biodegradable plastic) applications. This study compares expression levels of PBP genes (synthetic) integrated into the nuclear genome or the large single-copy (LSC) or inverted repeat (IR) region of the chloroplast genome in transgenic tobacco plants. Polymer transcripts accumulated up to 100-fold higher in the IR plants than in those of nuclear transgenic plants. Integration of foreign genes into all of the chloroplast genomes (homoplasmy) and higher levels of polymer transcripts were observed only in the IR and not in LSC transgenic plants. Expression of the polymer protein was further confirmed by Western blot analysis.