Heat priming enhances cross-tolerance to subsequent drought stress in Haloxylon ammodendron seedlings via transcriptional reprogramming and metabolic adjustment

The results demonstrated that heat priming (37 °C for 12 h) significantly improved seedling survival under drought stress (simulated with 480 mmol·L⁻¹ sorbitol) and reduced cell mortality. Physiological analyses revealed that heat priming increased the activities of antioxidant enzymes (SOD, POD, and CAT) and the accumulation of proline and chlorophyll, albeit with aggravated membrane lipid peroxidation (elevated MDA content). Transcriptomic profiling revealed 909 heat-priming-specific differentially expressed genes (DEGs), which were predominantly enriched in plant‒pathogen interactions, the MAPK signaling pathway, and phenylpropanoid biosynthesis. Key genes such as WRKY24 and MAPK3 potentially mediate cross-regulation to reinforce stress memory. Furthermore, heat priming suppressed drought-induced excessive lignin accumulation, suggesting that cell wall remodeling contributes to drought tolerance. CONCLUSIONS : Collectively, heat priming activates oxidative defense, signal transduction, and metabolic reprogramming, thereby increasing cross-tolerance to secondary drought stress in H. ammodendron seedlings. These findings provide theoretical insights into its ecological adaptation and stress resistance.