Integrated Analysis of Transcriptome and Metabolome Profiles in Astragslus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao Seedlings Under Drought Stress

<b>Background:</b><i>Astragalus membranaceus</i> is a traditional Chinese medicinal herb with significant pharmacological value. Drought stress adversely affects its biomass accumulation and medicinal quality. <b>Methods:</b> In this study, we performed physiological profiling, transcriptomics, and metabolomics analyses on <i>A. membranaceus</i> (Fisch.) Bge. var. <i>mongholicus</i> (Bge.) Hsiao seedlings to elucidate the response mechanisms in both aboveground and root tissues under varying drought stress intensities (Control, CK; Light Drought LD; Moderate Drought MD; Severe Drought SD). <b>Results:</b> Our findings indicate that LD primarily activated antioxidant enzymes, whereas severe stress led to the dominance of osmotic adjustment. Compared with CK, drought treatments resulted in 2987 differentially expressed genes (DEGs; 1674 up-regulated and 1313 down-regulated) and 921 differentially accumulated metabolites (DAMs)-562 in positive ionization mode (224 up, 338 down) and 359 in negative ionization mode (166 up, 193 down). Both gene expression and metabolite accumulation exhibited pronounced stress intensity-dependent patterns, suggesting that <i>A. mongholicus</i> initiates a broad, gene activation-led "active coping" strategy and mobilizes increasingly extensive metabolic pathways as drought intensifies. <b>Conclusions:</b> Integrated transcriptomic and metabolomic analyses revealed a tissue-specific "shoot-root partitioned coordination" mechanism: aboveground tissues activated a glutathione metabolism-centered "antioxidant-osmotic adjustment" defense, while root tissues reconfigured amino acid metabolism to maintain energy supply and signaling. This synergistic coordination represents a core adaptive strategy of <i>A. mongholicus</i> under drought conditions. Our study provides deeper insights into the drought resistance mechanisms of <i>Astragalus</i> and offers valuable references for breeding drought-tolerant varieties of <i>Astragalus</i> and other medicinal plants.