Production of biologically degradable polymer polyaspartate in transgenic potato

Autor: Hausmann,T.; Huehns, M.; Neumann, K.; Lockau W.; Ziegler, K.; Kahmann, U.; Pistorius, E. K.; Broer, I.
In:

Renewable Resources and Biorefineries Conference (RRB3)

Autor: Hausmann,T.; Huehns, M.; Neumann, K.; Lockau W.; Ziegler, K.; Kahmann, U.; Pistorius, E. K.; Broer, I.
Jahr: 2007

Einordung:
Institut: Professur Agrobiotechnologie

Abstract:
The production of biodegradable polymers that substitute petrochemical compounds in commercial products, in transgenic plants is an important challenge for plant biotechnology. The polymer polyaspartate is used to substitute polycarboxylates. It can be isolated from the bacterial storage protein cyanophycin, composed of L-Aspartat and L-Arginin. Cyanophycin is produced via non-ribosomal protein biosynthesis by a cyanophycin synthetase. Potato tubers are particularly suitable for the production of biopolymers since they allow a cost effective manufacture as a byproduct of starch. To produce cyanophycin in plants, three different cyanophycin synthetase genes (Berg et al. 2000) were expressed constitutively in tobacco and potato plants. Only one of the three synthetases produced cyanophycin in plants with up to 0.1 % polymer in dry weight (dw). Granula containing cyanophycin were detected by electron microscopy in different transgenic lines in leaves and for potato also in tubers. Unfortunately the transgenic tobacco and potato lines exhibited different stress symptoms like reduced growth, variegated leaves and early flower induction (Neumann et al. 2005). To increase polymer synthesis, the functional cyanophycin synthetase gene was fused to different transit peptide sequences for import into chloroplasts. In transgenic tobacco and potato lines cyanophycin content increased up to 3 % in dw. Additionally, these plants did not exhibit any phenotypic damage but a slightly thicker cell wall. The reduction of polymer synthesis to potato tubers results in very small tubers with a polymer content up to 2 % in dw. Up to now, the highest cyanophycin content was observed by a tuber specific production in plastids without phenotypical changes.

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