Widely targeted metabolomic and transcriptomic analyses of the effects of blue polarized light and ordinary light on Dendrobium officinale.

Dendrobium officinale, an orchid native to China, benefits the stomach, moistens the lungs, and enhances immunity. Light affects the synthesis of functional metabolites in D. officinale. The luminescence mechanism of polarized light differs from that of ordinary light sources and has different effects on plants. In this study, different light treatments-white (W), blue (B), and blue polarized (BP) light-were applied to D. officinale. In comparison to ordinary light sources, blue polarized light significantly altered the stem color, making it reddish. RNA-seq and targeted metabolomics analysis were used to investigate the mechanisms underlying the effects of the different light treatments on D. officinale. The results revealed that 2448, 2065, and 2763 genes and 1190, 812, and 958 metabolites were differentially expressed in the BP-B, BP-W and W-B comparisons, respectively. GO and KEGG analyses of the DEGs revealed that the most significant differences between D. officinale under polarized light and ordinary light sources were in pathways related to microtubules, UDP-glycosyltransferase activity and microtubule binding. Metabolome analysis revealed that the expression of melanoside A, 1-methyl-L-histidine, and rhapontigenin 3'-O-glucoside were the SCMs most strongly affected by blue polarized light. The use of bidirectional orthogonal partial least squares analysis revealed a significant transcriptome-metabolome correlation in the BP-W and BP-B comparisons. Joint analysis of DEGs and SCMs revealed significant differences between polarized and ordinary light sources, mainly in terms of plant hormone signal transduction, zeatin biosynthesis, phenylpropanoid biosynthesis, and flavonoid biosynthesis. These results highlight that blue polarized light enhances flavonoid and phenylpropanoid metabolism, offering a strategy for improved secondary metabolite yield in D. officinale cultivation.