Format: ORAL

John C. Cushman1

1Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV 89557-330, USA

The global climate crisis is rapidly increasing major crop losses around the world due to increased intensity and duration of drought events. Therefore, novel strategies are needed to create more climate-resilient crops. Remarkable progress has been made in advancing our understanding of the functional genomics of crassulacean acid metabolism (CAM) in the last decade. Dozens of CAM plant genomes have now been sequenced including obligate CAM species such as Kalancho fedtschenkoi, facultative CAM species such as Mesembryanthemum crystallinum, and important crops such as Agave, Ananas, Hylocereus, and Opuntia. Well-annotated genomes along with extensive transcriptomic, proteomic, and metabolomic datasets and associated co-expression and transcriptional regulatory networks provide a strong foundation for understanding the biochemical and regulatory frameworks that underpin the diel and circadian operation of CAM. Detailed time-resolved transcriptome profiling analysis in the facultative CAM plant M. crystallinum has revealed hundreds of genes with putative CAM-associated functions that provide the building blocks for creating synthetic versions of CAM in the C3 photosynthesis model Arabidopsis thaliana. We have built different gene circuits to recreate synthetic versions of the carboxylation, decarboxylation, and core diel carboxylation + decarboxylation modules of CAM. The carboxylation module increased CO2 assimilation, nocturnal malate accumulation, and plant biomass whereas the decarboxylation module improved water-use efficiency. Combining the carboxylation and decarboxylation modules resulted in increased CO2 assimilation, nocturnal malate accumulation, plant biomass, and improved water-use efficiency. Design and implementation of new iterations of the SynCAM design cycle (SynCAM 2.0) also target soybean, a major crop that suffers large economic losses due to damage from drought events. CAM functions optimally within succulent leaves so the benefits of tissue succulence engineering will also be discussed.