Photosynthetic and Genetic Adaptations Underpinning the Resilience of Cistanthe longiscapa in the Atacama Desert

O_LIThe Atacama Desert is one of the most hostile environments for life. However, the plant species Cistanthe longiscapa (C. longiscapa) completes its life cycle in the Atacama Desert after sporadic rainfall. C_LIO_LIPhysiological analyses under controlled environmental conditions revealed superior photosynthetic performance, better light acclimation mechanisms, and larger accumulation of photosystem II in C. longiscapa compared to its mesophilic sister species. C_LIO_LIC. longiscapa shows evolutionary expansions in gene families related to DNA repair, photosynthesis, and protein homeostasis. In addition, we observed substantial gene duplication and polymorphic variations between coastal and inland populations in the Atacama Desert. Finally, our assembled mitochondrial genome provides genetic information for all DNA-containing compartments of C. longiscapa. C_LIO_LIDiurnal oscillations of malic acid and time-resolved transcriptome analyses of plants harvested in the Atacama Desert indicate that C. longiscapa engages in CAM metabolism. We observed significant differences in transcripts encoding plastid-localized proteins, including those involved in carbon metabolism, light harvesting, and photoprotection, highlighting the critical role of chloroplasts in the adaptation of C. longiscapa to the Atacama Desert. C_LIO_LIOur study provides physiological and genetic evidence for the adaptations of C. longiscapa and advances our understanding of how plants can cope with extreme environmental conditions. C_LI