Ossa, P. | Search bioRxiv

bioRxiv2024

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

plant biology↗

bioRxiv2022

Transcriptomic analysis of the C3-CAM transition in Cistanthe longiscapa, a drought tolerant plant in the Atacama Desert

One of the most outstanding plant species during the blooming of the Atacama Desert is the annual plant Cistanthe longiscapa. This plant can perform CAM photosynthesis, but the ecophysiological and molecular mechanisms that this plant uses to withstand the extreme conditions it inhabits in the field are unknown. Morphological and ecophysiological traits were studied and leaf samples at dawn/dusk times were collected from three sites distributed across an increasing south to north arid gradient, to evaluate CAM expression and transcriptomic differences, and search for links between photosynthetic path and abiotic response. Plants from the different sites presented significant differences in nocturnal leaf acid accumulation, isotopic carbon ratio ({delta}13C), succulence and other four traits that clearly indicated a spectrum of CAM photosynthesis intensity that correlated with aridity intensity. The differential gene expression analysis among Dawn vs Dusk between sampling sites showed higher gene expression in the arid northern site (3991 v/s 2293) with activation of regulatory processes associated with abscisic acid and circadian rhythm. The analysis highlights clear ecophysiological differences and the requirement of a strong rewiring of the gene expression to allow a transition from a weak into a strong CAM in C. longiscapa.

plant biology↗