Comparative genomics analysis of drought response between obligate CAM and C3 photosynthesis plants

Crassulacean acid metabolism (CAM) plants exhibit elevated drought and heat tolerance compared to C-3 and C-4 plants through an inverted pattern of day/night stomatal closure and opening for CO2 assimilation. However, the molecular responses to water-deficit conditions remain unclear in obligate CAM species. In this study, we pre-sented genome-wide transcription sequencing analysis using leaf samples of an obligate CAM species Kalanchoe & BULL; fedtschenkoi under moderate and severe drought treatments at two-time points of dawn (2-h before the start of light period) and dusk (2-h before the dark period). Differentially expressed genes were identified in response to environmental drought stress and a whole genome wide co-expression network was created as well. We found that the expression of CAM-related genes was not regulated by drought stimuli in K. fedtschenkoi. Our comparative analysis revealed that CAM species (K. fedtschenkoi) and C-3 species (Arabidopsis thaliana, Populus deltoides 'WV94') share some common transcriptional changes in genes involved in multiple biological processes in response to drought stress, including ABA signaling and biosynthesis of secondary metabolites.