Tissue-specific and environmental regulation of ascorbate accumulation in the cactus <i>Nopalea cochenillifera</i>

Cacti are xerophytic plants characterized by water-storing cladodes, thick cuticles, and CAM photosynthesis, enabling high productivity under harsh conditions. They accumulate ascorbate (AsA) at levels comparable to those of leafy vegetables, potentially contributing to stress tolerance and nutritional value. However, the regulation of AsA accumulation in cacti remains poorly understood. Here, we used the dwarf prickly pear cactus Nopalea cochenillifera to investigate the tissue-specific distribution and environmental responses of AsA. AsA preferentially accumulated in the cortex, exhibited light-dependent increases, and was maintained or even increased under high-light, drought, and low-temperature stress conditions. Supplementation experiments with AsA and its precursors suggest the presence of multiple biosynthetic pathways and inter-cladode transport mechanisms. These results provide insights into mechanisms specific to the cactus N. cochenillifera for maintaining AsA homeostasis under adverse environmental conditions. This study provides the first evidence of tissue-specific and stress-responsive regulation of AsA metabolism in cactus cladodes.