Chloroplasts are a major advantage to doing synthetic biology in plants. They produce starch and some amino acids as well as hosting photosynthesis, all fully separated from other cellular functions going on in the rest of the cell. Synthetic biology approaches could turn them into individualised micro-factories inside plant cells, synthesising whatever compound you fancy without poisoning the cell and with almost no risk of any transgenes escaping into other plants.
Stable plastid transformation was first achieved in tobacco in 1990. Since then, chloroplast transformation has been successful in many plant species – a 2009 review by Huan-Hyan Wang et al. (JGG 36:387) contains a nice table summarizing the methods used in each species. Plastid-based biosynthesis of biopharmaceuticals has been researched for years, but synthetic biology technologies make it possible to consider moving beyond synthesis of antigens and relatively simple molecules (for examples see Daniell et al. 2009, Trends in Plant Sci 14:669) to more complex structures.
In today’s highlighted paper, Nielson et al. successfully built the P450-dependant dhurrin pathway into tobacco chloroplast cells. This in itself does not have a major benefit to science, as dhurrin has no real value, but as a proof of concept this is worthy of note. The three-step biosynthesis of dhurrin from L-tyrosine is normally based on the endoplasmic reticulum, and its rate is limited by low concentrations of NADPH. By building the pathway in a chloroplast, the authors have proven not only the feasibility of chloroplast pathway engineering, but also the potential of using reducing power from photosynthesis to run biosynthesis pathways.
For more information about chloroplast engineering, this 2011 paper reviews chloroplast transformation markers and this paper is another example of pathway engineering in chloroplasts.
More generally, to find out about synthetic biology approaches please register for our Synthetic Biology meeting, which aims to introduce synthetic biology to plant scientists. It is £250 for academics, and includes overnight accommodation and meals – there is a reduced rate for students and post-docs.
Highlighted paper: Agnieszka Zygadlo Nielsen, Bibi Ziersen, Kenneth Jensen, Lærke Münter Lassen, Carl Erik Olsen, Birger Lindberg Møller, and Poul Erik Jensen (2013) Redirecting Photosynthetic Reducing Power toward Bioactive Natural Product Synthesis. ACS Synthetic Biology DOI: 10.1021/sb300128r
Image credit: Martin Bahmann, via Wikimedia Commons.
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