Engineering CAM Photosynthetic Machinery into C3 Arabidopsis -Mesembryanthemum crystallinum

Crassulacean acid metabolism (CAM) is an adaptation that reduced water loss through stomata by shifting the diel rhythm of CO₂ fixation from day to night, which results in improved water-use efficiency. Introducing the CAM pathway into C₃ plants is expected to confer improved WUE in order to allow plants to withstand long episodes of drought or perhaps even expand crop production into semi-arid regions. The introduction of the CAM pathway into C₃ plants such as Arabidopsis thaliana will likely require several important tasks: (i) the proper temporal and mesophyll expression patterns of multiple C₄ enzymes in order to reconstitute CAM photosynthetic machinery; (ii) an increased mesophyll cell size in order to produce and store malate in the vacuoles in mesophyll cells; (iii) an effective multiple gene assembly strategy for large number of gene cassettes; and (iv) strategies to overcome heterochromatin-mediated gene silencing and reduced mRNA expression of downstream genes in cis-acting modules of gene sets to prevent transgene silencing and ensure stable expression of CAM pathway enzymes. This study will summarize current progress achieved to date for defining the genetic and anatomical requirements for CAM biodesign such as succulent engineering and multi-gene assembly strategies for stable and optimal expression of CAM genes in C₃ Arabidopsis.