13The circadian clock drives time-specific gene expression, allowing for associated 14 biological processes to be active during certain times of the 24 h day. Crassulacean acid 15 metabolism (CAM) photosynthetic plants represent an interesting case of circadian regulation of 16 gene expression as CO 2 fixation and stomatal movement in CAM plants display strong circadian 17 dynamics. The molecular mechanisms behind how the circadian clock enabled these 18 physiological differences is not well understood. Therefore, we set out to investigate whether 19 core circadian elements in CAM plants were re-phased during evolution, or whether networks of 20 phase-specific genes were simply connected to different core elements. We utilized a new metric 21 for identifying candidate core genes of a periodic gene network and then applied the Local Edge 22Machine (LEM) algorithm to infer regulatory relationships between the candidate core clock 23 genes and orthologs of known core clock genes in K. fedtschenkoi. We also used LEM to identify 24 stomata-related gene targets for K. fedtschenkoi core clock genes and constructed a subsequent 25 gene regulatory network. Our results provide new insights into the mechanism of circadian 26 control of CAM-related genes in K. fedtschenkoi, facilitating the engineering of CAM machinery 27 into non-CAM plants for sustainable crop production in water-limited environments.