Physiological and Transcriptome Analysis of Polygonatum Cyrtonema Under Continuous Drought Stress

Against the backdrop of global warming and the increasingly uneven distribution of water resources, drought has emerged as a critical abiotic stressor limiting the growth and quality formation of medicinal plants. In this study, Polygonatum Cyrtonema was subjected to a continuous drought treatment experiment by withholding water for 5, 10, and 20 days, alongside a well-watered control (CK), to preliminarily investigate its physiological responses and transcriptomic alterations under water-deficit conditions. Physiological measurements revealed that prolonged drought stress significantly increased the concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in leaves, accompanied by elevated in superoxide dismutase (SOD) and peroxidase (POD) activities, as well as increased chlorophyll content. RNA-seq analysis identified a substantial number of differentially expressed genes (DEGs), with 11,835, 12,110, and 11,416 DEGs in the D5, D10, and D20 vs. CK comparisons, respectively, including 6133 shared core DEGs. KEGG enrichment analysis indicated that these DEGs were primarily involved in starch and sucrose metabolism, phenylpropanoid biosynthesis, and plant hormone signal transduction. Weighted gene co-expression network analysis (WGCNA) identified a specific gene module (black module) containing 1681 genes that was highly positively correlated with drought duration (r = 0.95). Protein–protein interaction (PPI) network analysis of this module highlighted several candidate hub genes, including WRKY33 (BMK_Unigene_251623), EDA39(BMK_Unigene_034545), OHP (BMK_Unigene_221621), and RD20 (BMK_Unigene_149641). Furthermore, genes within the black module were significantly enriched in metabolic pathways such as anthocyanin, phenylpropanoid, and isoflavonoid biosynthesis, as well as phenylalanine, tyrosine, tryptophan, arginine, and proline metabolism. RT-qPCR validation confirmed the expression patterns of these candidate genes, supporting the reliability of the transcriptomic data. Collectively, these findings provide transcriptomic insights into the continuous drought response in P. cyrtonema, and identify candidate genes and pathways for future functional validation and stress-resilience improvement in this species.