Transcriptomic and Metabolomic Analysis of CAM in Ice Plant

Crassulacean acid metabolism (CAM) is a water-use efficient photosynthetic adaptation found in more than 6% of vascular plant species.  This adaptation is distinguished by the temporal separation of primary C₄ and secondary C₃ carboxylation reactions to reduce daytime water loss.  To investigate the underlying orchestration of transcriptional networks controlling the temporal separation of these competing carboxylation reactions and their associated metabolic demands, transcriptomic and metabolomic analyses were conducted on the facultative CAM ice plant, Mesembryanthemum crystallinum.  These omic technologies revealed diel and circadian changes in transcript and metabolite abundance patterns in ice plants performing C₃ and CAM (induced by water-deficit stress) over a 72 h time course.  Key differences in transcripts and metabolites were identified between the C₃ and CAM states that are involved in CAM adaptation and possibly their role in the regulation of CAM by the circadian clock.  Other pivotal omic results and candidate CAM transcription factors to elucidate clock-controlled regulatory networks operating in mesophyll cells will be discussed.