Multi-Level Transcriptomic and Physiological Responses of to Different Light Intensities Reveal a Moderate-Light Adaptation Strategy.

OBJECTIVES

Light intensity is a critical environmental factor regulating plant growth, development, and stress adaptation. However, the physiological and molecular mechanisms underlying light responses in , a valuable alpine medicinal plant, remain poorly understood. This study aimed to elucidate the adaptive strategies of under different light intensities through integrated physiological and transcriptomic analyses.

METHODS

Two-year-old plants were exposed to three controlled light regimes (790, 620, and 450 lx). Leaf anatomical traits were assessed via histological sectioning and microscopic imaging. Antioxidant enzyme activities (CAT, POD, and SOD), membrane lipid peroxidation (MDA content), osmoregulatory substances, and carbon metabolites were quantified using standard biochemical assays. Transcriptomic profiling was conducted using Illumina RNA-seq, with differentially expressed genes (DEGs) identified through DESeq2 and functionally annotated via GO and KEGG enrichment analyses.

RESULTS

Moderate light (620 lx) promoted optimal leaf structure by enhancing palisade tissue development and epidermal thickening, while reducing membrane lipid peroxidation. Antioxidant defense capacity was elevated through higher CAT, POD, and SOD activities, alongside increased accumulation of soluble proteins, sugars, and starch. Transcriptomic analysis revealed DEGs enriched in photosynthesis, monoterpenoid biosynthesis, hormone signaling, and glutathione metabolism pathways. Key positive regulators ( and ) were upregulated, whereas negative regulators ( and ) were suppressed, collectively facilitating chloroplast development and photomorphogenesis. Trend analysis indicated a "down-up" gene expression pattern, with early suppression of stress-responsive genes followed by activation of photosynthetic and metabolic processes.

CONCLUSIONS

employs a coordinated, multi-level adaptation strategy under moderate light (620 lx), integrating leaf structural optimization, enhanced antioxidant defense, and dynamic transcriptomic reprogramming to maintain energy balance, redox homeostasis, and photomorphogenic flexibility. These findings provide a theoretical foundation for optimizing artificial cultivation and light management of alpine medicinal plants.