Elevated CO2 primes drought resistance in mulberry via multi-omics reprogramming of carbon and redox metabolism

Abstract

Drought stress severely constrains the growth and productivity of woody perennials. While elevated CO2 (ECO2) can mitigate drought stress, the systemic mechanisms underlying this synergy remain largely unexplored in horticultural species. Here, we integrated physiological assays with transcriptomic, proteomic, and metabolomic analyses to investigate how ECO2 (710 ppm/760 ppm) enhances drought resistance in mulberry (Morus alba L.), an economically important tree crop. We found that ECO2 sustains photosynthetic capacity and improves water-use efficiency by 21% under drought. Multi-omics profiling revealed that ECO2 orchestrates a metabolic shift from stress endurance to proactive defense by: (1) enhancing glycolytic and TCA cycle flux to ensure energy and carbon skeleton supply; (2) activating the phenylpropanoid pathway and elevating key antioxidant enzymes (SOD, POD, APX, GR), collectively reducing H2O2 and MDA by 26% and 18%, respectively; and (3) fine-tuning osmotic balance through coordinated proline and GABA shunt metablism. Crucially, ECO2 stabilizes key antioxidant proteins post-transcriptionally and redirects carbon toward structural defenses like lignin and coumarins precursors. Our study unveils a CO2-driven metablic priming strategy that enhances drought resilence in mulberry, providing novel insights and biomarker candidates for breeding climate-resilient horticultural crops.