Chloroplast Biotechnology - Reengineering Photosynthetic Organelles

The 2015 Gordon Research Conference on Chloroplast Biotechnology will present cutting-edge research by an international group of scientists interested in experimental approaches to probe chloroplast structure and function and to exploit plastome engineering for biotechnological applications. The meeting is particularly timely in bringing together a growing community of scientists combining fundamental studies on chloroplast molecular biology with applications in agriculture, industrial biotechnology and healthcare. Covered at the meeting will be microalgae as well as land plants.

The topics will include organelle genome evolution, revealing structural diversity that may guide the design of synthetic organelle genomes. Speakers will provide an update on all aspects of chloroplast gene expression, including the transcription machinery, mRNA processing, mRNA editing and mRNA degradation, mRNA translation and protein processing, assembly and turnover. Emphasis will be on the role of small regulatory RNAs and the function of nuclear-encoded, organelle-targeted RNA-binding proteins, the functions of which are largely unknown.

Applications will include engineering plastid-encoded genes to improve plant productivity and boost biofuel production. Introduction of novel biosynthetic pathways in the plastid genome through engineering of polycistronic operons will be part of the program. Production of vaccines, industrial enzymes, and human therapeutic proteins in chloroplasts will also be discussed. Plastid engineering is routine in tobacco, tomato, potato, lettuce, cabbage and soybean, but thus far has not been successful in many other species, including monocots. Technical advances needed to extend to new crops and development of new regulated expression systems will be part of the program.

Plastids, best known as chloroplasts when specialized for photosynthesis, are plant cellular organelles with a relatively small genome (ptDNA; 120-230-kb in size) that is present in up to thousands of copies per cell. Genetically stable transplastomic plants are obtained by modification of a plastid genome by homologous recombination, followed by replication of the transformed ptDNA and gradual dilution of wild type genome copies under selection in cultured cells, and plant regeneration. Generally recognized benefits of plastid engineering are: the potential for high-level protein expression from plastid transgenes; the potential for expression of multiple genes in operons; and transgene containment in crops in which only the maternal parent inherits plastids, thereby preventing transgene flow via pollen. Plastid transformation today is applied to problems in four general areas: (1) expression of recombinant proteins for industrial and pharmaceutical applications; (2) engineering the plastid genome to improve plant productivity; (3) engineering novel pathways into chloroplasts; (4) engineering novel agronomic traits into chloroplasts for gene stacking and transgene containment.

Plastid transformation in Chlamydomonas was achieved in 1988, followed by transformation of the plastid genome in tobacco in 1990. As of today, despite the outstanding promise of this technology, no transplastomic crop is grown commercially. Nevertheless, a number of biotechnology companies are interested in its possible application. The conference, because of its relatively small size, will provide an excellent opportunity for information exchange for researchers from public research institutions as well as the biotechnology industries. It is hoped that this interaction will spawn new ideas, research strategies and ultimately commercial products.