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

Abstract

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 (?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.

Mechanisms of flower coloring and eco-evolutionary implications of massive blooming events in the Atacama Desert

“…For instance, unlike anthocyanins, the color of betalains is stable between pH = 3-7 (Strack et al, 2003). This may provide advantages for species like C. longiscapa, which upon experiencing water stress switch the mode of carbon assimilation from C3 to Crassulacean acid metabolism (CAM), shifting from a relatively stable vacuolar pH to large diurnal pH fluctuations (Winter and Holtum, 2014;Jain and Gould, 2015;Ossa et al, 2022). Having stable pigments under such fluctuating conditions would ensure their functionality in a harsh, hyperarid environment such as the Atacama Desert (Jain and Gould, 2015).…”