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Background : Lycoris radiata belongs to the Amaryllidaceae family and is a bulbous plant native to South Korea, China, and Japan. Galantamine, a representative alkaloid of Amaryllidaceae plants, including L. radiata, exhibits selective and dominant acetylcholinesterase inhibition. In this study, transcriptome analysis of L. radiata was performed.
Methods and Results : Genes for galantamine biosynthesis were used to design primers for qRT-PCR. Quantitative RT-PCR was performed with LrActin as a reference gene for normalization. The RT-PCR results reveal the expression of LrPAL A and LrC4H at an early stage in the pathway. Interestingly, the expression of these genes was significantly higher in roots. However, the expression levels of LrNNR and LrN4OMT, which are closely involved in galantamine biosynthesis, were significantly higher in bulbs than leaves and roots. The expression levels of LrPAL B, LrTYDC, LrCYP98A3 and LrCYP76T were not significantly different among the different parts of the plants tested. HPLC analysis confirmed the presence of galantamine in all the organs, including the root (0.53 ± 0.07 ㎎/g dry weight), bulb (0.27 ± 0.04 ㎎/g dry weight), and leaf (0.75 ± 0.09 ㎎/g dry weight). The galantamine level in the bulb was 1.42 and 2.78 times higher than that in the root and leaf, respectively. The results of qRT-PCR for the eight galantamine genes revealed relatively high levels of genes expressed early, including LrPAL A, LrPAL B, LrC4H, and LrTYDC in the roots. However, in the bulbs, the levels of LrNNR and LrN4OMT were higher, which are crucial for galantamine biosynthesis. It also explains why bulbs contain high amounts of galantamine, which is likely due to the increased expression of LrNNR and LrN4OMT and the high levels of LrCYP96T, although the genes expressed early were expressed at high levels in the root.
Conclusion : Transcript data of plants grown in a growth chamber revealed high expression levels of LrNNR and LrN4OMT genes that are closely involved in galantamine biosynthesis, and, as expected, we observed higher amounts of galantamine in the bulbs than in the root and leaves.
