Positive selection and heat-response transcriptomes reveal adaptive features of the Brassicaceae desert model, Anastatica hierochuntica

Plant adaptation to a desert environment and its endemic heat stress is poorly understood at the molecular level. The naturally heat-tolerant Brassicaceae species Anastatica hierochuntica is an ideal extremophyte model to identify genetic adaptations that have evolved to allow plants to tolerate heat stress and thrive in deserts. We generated an A. hierochuntica reference transcriptome and identified extremophyte adaptations by comparing Arabidopsis thaliana and A. hierochuntica transcriptome responses to heat, and detecting positively selected genes in A. hierochuntica. The two species exhibit similar transcriptome adjustment in response to heat and the A. hierochuntica transcriptome does not exist in a constitutive heat 'stress-ready' state. Furthermore, the A. hierochuntica global transcriptome as well as heat-responsive orthologs, display a lower basal and higher heat-induced expression than in A. thaliana. Genes positively selected in multiple extremophytes are associated with stomatal opening, nutrient acquisition, and UV-B induced DNA repair while those unique to A. hierochuntica are consistent with its photoperiod-insensitive, early-flowering phenotype. We suggest that evolution of a flexible transcriptome confers the ability to quickly react to extreme diurnal temperature fluctuations characteristic of a desert environment while positive selection of genes involved in stress tolerance and early flowering could facilitate an opportunistic desert lifestyle.

Automated summary

This study investigates the genetic adaptations of the heat-tolerant Brassicaceae species Anastatica hierochuntica to desert environments. By comparing the responses to heat stress in the transcriptomes of A. hierochuntica and Arabidopsis thaliana, the research identifies extremophyte adaptations. The study finds that A. hierochuntica exhibits similar transcriptome adjustments to heat as A. thaliana, but with a lower basal expression and higher heat-induced expression. Positively selected genes in A. hierochuntica are associated with stomatal opening, nutrient acquisition, UV-B induced DNA repair, and its unique photoperiod-insensitive, early-flowering phenotype. The study suggests that the evolution of a flexible transcriptome allows plants to quickly respond to extreme temperature fluctuations, while positive selection of stress tolerance and early flowering genes facilitates an opportunistic desert lifestyle.