Metabolic Profiling of Primary Metabolites and Galantamine Biosynthesis in Wounded Lycoris radiata Callus

Abstract

Plants are continuously exposed to abiotic and biotic factors that lead to wounding stress. Different plants exhibit diverse defense mechanisms through which various important metabolites are synthesized. Humans can exploit these mechanisms to improve the efficacy of existing drugs and to develop new ones. Most previous studies have focused on the effects of wounding stress on the different plant parts, such as leaves, stems, and roots. To date, however, no study has investigated the accumulation of primary and galantamine content following the exposure of a callus to wounding stress. Therefore, in the present study, we exposed Lycoris radiata calli to wounding stress and assessed the expression levels of several genes involved in metabolic pathways at various time points (0, 3, 6, 12, 24, 48, 72, and 96 h of exposure). Furthermore, we quantify the primary and galantamine content using gas chromatography–time-of-flight mass spectrometry and the high-performance liquid chromatography qRT-PCR analysis of eight galantamine pathway genes (LrPAL-2, LrPAL-3, LrC4H-2, LrC3H, LrTYDC2, LrN4OMT, LrNNR, and LrCYP96T) revealed that seven genes, except LrN4OMT, were significantly expressed following exposure to wounding stress. Galantamine contents of calli after 3, 6, 12, 24, 48, 72, and 96 h of exposure were respectively 2.5, 2.5, 3.5, 3.5, 5.0, 5.0, and 8.5 times higher than that after 0 h of exposure. Furthermore, a total of 48 hydrophilic metabolites were detected in the 0 h exposed callus and 96 h exposed callus using GC-TOFMS. In particular, a strong positive correlation between galantamine and initial precursors, such as phenylalanine and tyrosine, was observed.