Plant synthetic biology has incredible promise to produce many important natural products and therapies both cost effectively and sustainably. The CU-Boulder team aims to genetically engineer soybeans (Glycine max) as a cost effective method to produce precursors of the chemotherapeutic drug Paclitaxel. Paclitaxel is currently expensive for patients and manufacturing methods struggle to produce necessary yields sufficiently and sustainably. By producing Paclitaxel in soybeans, the CU-Boulder team hopes to provide a sustainable and relatively inexpensive method of producing this essential chemotherapeutic. To accomplish this, the CU-Boulder team is introducing enzymes of the Paclitaxel biosynthesis pathway from the yew tree into soybeans. We are the first iGEM team to employ soybeans as a synthetic biology chassis. Soybeans are farmed efficiently and have high potential as a synthetic biology chassis for green manufacturing. This solution has the potential to be applied to many other unsustainable manufacturing problems such as the antimalarial drug artemisinin found in minute quantities of the sweet wormwood plant. One problem with this solution is the legitimate concern that engineered soybean crops could contaminate neighboring fields with pollen. Our team is proposing to tackle this problem by engineering soybeans with a unique biocontainment safety feature.
The CU-Boulder team is engineering soybeans to produce flowers that remain closed (cleistogamous), ensuring self-fertilization and safe biocontainment of the genetically engineered crop. Soybeans represent an entirely new organism for the iGEM competition, and we propose to make this chassis safer with a robust and ethical biocontainment system for the biopharming industry.
Our goal is for the engineered soybeans to completely biocontain their pollen to prevent outcrossing with neighboring fields. Luckily, there are special varieties of soybeans that grow in high latitudes which are naturally cleistogamous. Our engineering challenge is to design soybeans that will grow in latitudes where soybeans are commonly farmed yet are also cleistogamous. Null alleles of two Phytochrome A genes have been demonstrated to be responsible for the closed (CL) flower phenotype of the northern Japanese soybean cultivars 2,4. We are designing RNAi knockdown constructs of both Phytochrome A genes that express specifically in soybean flowers. By introducing this construct into a commonly farmed cultivar of soybeans, we plan to build a soybean plant that can be widely farmed while mimicking the closed flowers of the northern Japan cultivars. A biosafe version of soybeans could help promote biopharming on a wider scale beyond iGEM.
You may notice that herbicide resistance, a common method used to select for correctly transformed plants, is not included in our BioBrick Parts Collection. Instead, our final engineered plasmids are designed to use RUBY, a clearly visible plant marker first described by He et al. 20201. RUBY teaches plants that have been correctly transformed with modified genes how to turn red like beets and swiss chard. Our choice of reporter genes prevents the unnecessary use of additional and potentially hazardous herbicides and reduces our chemical lab waste.