Regulation of Stomatal Movement Using Synthetic Biology Approach

Crassulacean acid metabolism (CAM) enhances plant water-use efficiency and drought tolerance by reducing transpirational water loss through stomatal closure during the day when the temperature is higher and stomatal opening during the night when the temperature is lower. Engineering CAM into C₃ plants has the potential to sustain production of food, feed, fiber, and biofuel in hotter and drier climates. A key task of CAM-into-C₃ engineering is to inverse the stomatal behavior of C₃ plants, in which stomata are open during the day and closed at night. Stomatal movement depends on the transport of inorganic ions and organic metabolites across guard cell membranes. The transporters are regulated by various signaling pathways such as abscisic acid (ABA), blue light, CO₂ and Ca²⁺ signaling pathways. Based on the newly-sequenced genome of Kalanchoe laxiflora (an obligate CAM species with a genome size of ~250Mb), we identified some candidate genes involved in regulation of stomatal movement in CAM plants. We designed and assembled the several genetic circuits of ‘CAM-like stomatal movement’ using synthetic biology approaches, and transferred them into three target C₃ species (i.e., Arabidopsis, tobacco, poplar) via Agrobacterium-mediated transformation. The effects of these genetic circuits on stomatal movement in the transgenic plants will provide useful information for optimizing the strategy of CAM-into-C₃ engineering. Also, success of this research could facilitate future efforts to engineer other multi-gene traits through synthetic biology approaches.