Transcriptomic Characterization and Co-expression Network Analysis of Hippophae rhamnoides subsp. sinensis (Chinese Seabuckthorn) in Response to Drought Stress

Ecological restoration in arid regions is severely limited by water scarcity. Chinese seabuckthorn, an important economic tree species in arid and semi-arid areas, exhibits strong drought resistance. In this study, physiological indices such as plasma membrane permeability (PMP), proline, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activity, soluble sugars (SS), and soluble proteins (SP) increased under drought stress and declined after rehydration. Relative water content (RWC) decreased under drought conditions but recovered rapidly after rewatering, while chlorophyll content continued to decline. RNA sequencing (RNA-seq) identified 10,829 differentially expressed genes (DEGs) between drought-treated and control groups. KEGG pathway analysis revealed that phytohormone signaling, starch and sucrose metabolism, and photosynthesis were core pathways involved in drought response. Pathways related to terpene, flavonoid, and other secondary metabolite biosynthesis were also enriched. Weighted gene co-expression network analysis (WGCNA) identified 16 hub genes associated with drought tolerance. Ten candidate genes were selected for qPCR validation, which confirmed the RNA-seq results. These findings provide important insights into the physiological and molecular mechanisms of drought resistance in Chinese seabuckthorn.