Physiological and molecular mechanism analysis of Cyclocodon lancifolius seedlings in response to varying degrees of drought stress

Abstract Background Cyclocodon lancifolius is an increasingly valued dual-purpose medicinal-edible plant resource in contemporary society. Owing to the coincidence of its rapid seedling growth phase with the season characterized by frequent droughts, water-deficit stress severely compromises seedling development and biomass accumulation under field cultivation. Nevertheless, the Physiological and molecular mechanisms underlying drought stress perception, signal transduction and adaptive responses in C. lancifolius seedlings remain virtually uncharacterized. Consequently, an integrated dual-omics approach combing transcriptomics and metabolomics is imperative to initially dissect the drought-responsive regulatory networks, thereby providing a foundational framework for elucidating the complete signal transduction cascades that govern drought adaptation in this species. Results Seven-month-old C. lancifolius seedlings were subjected to three treatments: control (C), moderately drought (MD), and severely drought (SD). Drought stress inhibited the growth and development, and photosynthesis of C. lancifolius seedlings, significantly reducing Tr, P N, Ci, Gs, LCP, and CE in photosynthetic characteristics. Drought stress also modulated other physiological and biochemical characteristics, including reduced relative water content (RWC), leaf biomass, and chlorophyll content, which affect membrane lipid peroxidation and osmotic adjustment by increasing electrolyte permeability, malondialdehyde (MDA), and proline content. Concurrently, antioxidant enzymes such as peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) were activated to scavenge excess reactive oxygen species (ROS). Transcriptome analysis showed that drought stress induced more downregulated genes than upregulated genes in C. lancifolius seedlings. Metabolomics analysis revealed that there were more upregulated metabolites than downregulated metabolites. Combined transcriptomic and metabolomic analyses highlighted the crucial roles of starch and sucrose metabolism, glutathione metabolism, phenylpropanoid biosynthesis and flavonoid biosynthesis in drought tolerance of C. lancifolius seedlings, and explore the synthetic pathway of luteolin and caffeoylquinic acid. It was discovered that certain drought conditions promoted the caffeoylquinic acid accumulation and reduced the content of luteolin. Conclusions The study provides the first expressed genome resource for C. lancifolius, a novel medicinal and edible plant. Integrated transcriptomic and metabolomic data collectively reveal the critical molecular regulatory network underlying drought stress response in C. lancifolius. Thus, these findings lay the foundation for molecular breeding of drought-resistant varieties for C. lancifolius and other medicinal plants.