Dehydration intensity modulates mitochondrial ultrastructure and redox homeostasis in the extremotolerant desert moss...

This study investigated the mitochondrial response mechanisms of Syntrichia caninervis Mitt., a desiccation-tolerant moss from the Chinese Gurbantunggut Desert, to dehydration-rehydration stress at the subcellular level under three dehydration intensities: rapid drying (RD), slow drying (SD), and air drying (AD). The results showed that the moss maintained the structural integrity of mitochondrial membranes across treatments, demonstrating remarkable phenotypic plasticity. Rapid dehydration caused a pronounced decline in mitochondrial membrane potential (ΔΨm) and distortion of cristae, relying primarily on emergency antioxidant responses involving superoxide dismutase (SOD) and ascorbate peroxidase (APX) to scavenge reactive oxygen species (ROS). In contrast, slow dehydration activated a "pre-adaptive" antioxidant strategy characterized by sustained peroxidase (POD) activation, accumulation of reduced glutathione (GSH), and upregulation of alternative oxidase (AOX) activity. Principal component analysis confirmed that APX, SOD, and AOX were key contributors to drought adaptation. This study is the first to reveal dual-track adaptive mechanisms in desiccation-tolerant plants mediated through mitochondrial ultrastructure, membrane potential dynamics, and redox homeostasis regulation, and provides new targets for improving drought resistance in crops.