<i>Cistanthe longiscapa</i> exhibits ecophysiological and molecular adaptations to the arid environments of the Atacama Desert

Understanding how plants survive extreme conditions is essential to breeding resilient crops. Cistanthe longiscapa, which flourishes in the Atacama Desert, provides a rare glimpse into plant resilience. To uncover the genetic basis of its stress tolerance, we investigated the ecophysiological and transcriptomic responses of C. longiscapa from 3 sites with low but different precipitation levels. Ecophysiological analyses were performed on samples collected in the field at dusk and dawn, which are crucial stages in crassulacean acid metabolism (CAM), a water-efficient type of photosynthesis. Additional transcriptomic analysis allowed us to evaluate CAM intensity in C. longiscapa and identify changes in the molecular signature of these plants. Our results show that C. longiscapa displays considerable ecophysiological trait response variation across the 3 sites, including variations in markers such as nocturnal acid accumulation, isotopic carbon ratio, and succulence, among others. Analysis of gene expression patterns revealed differences among plants exhibiting varying intensities of CAM photosynthesis and identified key molecular signatures associated with their ecological strategies. Additionally, genes related to stress responses, plastid activities, and circadian rhythm show contrasting expression levels between strong and weak CAM plants, and this expression profile is shared with other CAM plants under stress. Our findings demonstrate that C. longiscapa is a valuable resource for identifying genes involved in the transition between different CAM intensities. This may lead to the discovery of genes that enhance plant tolerance to stressful environments.