Zhaojian Wang1,2, Weimin Jiang3, Yingying Liu4, Xiaoxi Meng5, Xinglong Su1, Mengyang Cao1, Liping Wu1, Nianjun Yu1, Shihai Xing6,7,8, Daiyin Peng9,10,11. 1. College of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, China. 2. Institute of Traditional Chinese Medicine Resources Protection and Development, Anhui Academy of Chinese Medicine, Hefei, 230012, China. 3. Hunan Key Laboratory for Conservation and Utilization of Biological Resources in the Nanyue Mountainous Region, Hengyang Normal University, Hengyang, 421008, China. 4. College of Humanities and International Education Exchange, Anhui University of Chinese Medicine, Hefei, 230012, China. 5. Department of Horticultural Science, University of Minnesota, Minneapolis, MN, 55108, USA. 6. College of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, China. xshshihai@163.com. 7. Institute of Traditional Chinese Medicine Resources Protection and Development, Anhui Academy of Chinese Medicine, Hefei, 230012, China. xshshihai@163.com. 8. Anhui Province Key Laboratory of Research & Development of Chinese Medicine, Hefei, 230012, China. xshshihai@163.com. 9. College of Pharmacy, Anhui University of Chinese Medicine, Hefei, 230012, China. Pengdy@ahtcm.edu.cn. 10. Institute of Traditional Chinese Medicine Resources Protection and Development, Anhui Academy of Chinese Medicine, Hefei, 230012, China. Pengdy@ahtcm.edu.cn. 11. Synergetic Innovation Center of Anhui Authentic Chinese Medicine Quality Improvement, Hefei, 230038, China. Pengdy@ahtcm.edu.cn.
Abstract
BACKGROUND: Dendrobium officinale, an endangered Chinese herb, possesses extensive therapeutic effects and contains bioactive ingredients such as major polysaccharides, alkaloids, and minimal flavonoids. We first obtained the protocorm-like bodies (PLBs) of this plant through tissue culture in order to determine the distribution of the main secondary metabolites in each organelle and the PLBs. We then analyzed the correlation between gene expression level from comparative transcriptome sequencing and metabolite content in different organs to identify putative genes encoding enzymes involved in the biosynthesis of polysaccharides, alkaloids, and flavonoids. RESULTS: We used seeds as explants for protocorm induction and PLB propagation of D. officinale. The optimal medium formula for PLB propagation was 1/2 MS + α-NAA 0.5 mg·L- 1 + 6-BA 1.0 mg·L- 1 + 2, 4-D 1.5-2.0 mg·L- 1 + potato juice 100 g·L- 1. Stems, PLBs and leaves of D. officinale had the highest content of polysaccharides, alkaloids and flavonoids, respectively. Naringenin was only produced in stem; however, PLBs with high alkaloid content can replace other organs producing alkaloids. The hot water extraction method outperformed the ultrasound-assisted extraction method for extracting polysaccharides from D. officinale. A comparative transcriptome analysis of PLBs and leaves of D. officinale revealed differential expression of genes encoding enzymes involved in polysaccharide, alkaloid and flavonoid biosynthetic pathways. Putative genes encoding enzymes involved in these biosynthetic pathways were identified. Notably, we identified genes encoding the alkaloid biosynthesis enzymes strictosidine β-D-Glucosidase, geissoschizine synthase and vinorine synthase in D. officinale. CONCLUSIONS: The identification of candidate genes encoding enzymes involved in metabolite biosynthesis will help to explore and protect this endangered species and facilitate further analysis of the molecular mechanism of secondary metabolite biosynthesis in D. officinale.
BACKGROUND:Dendrobium officinale, an endangered Chinese herb, possesses extensive therapeutic effects and contains bioactive ingredients such as major polysaccharides, alkaloids, and minimal flavonoids. We first obtained the protocorm-like bodies (PLBs) of this plant through tissue culture in order to determine the distribution of the main secondary metabolites in each organelle and the PLBs. We then analyzed the correlation between gene expression level from comparative transcriptome sequencing and metabolite content in different organs to identify putative genes encoding enzymes involved in the biosynthesis of polysaccharides, alkaloids, and flavonoids. RESULTS: We used seeds as explants for protocorm induction and PLB propagation of D. officinale. The optimal medium formula for PLB propagation was 1/2 MS + α-NAA 0.5 mg·L- 1 + 6-BA 1.0 mg·L- 1 + 2, 4-D 1.5-2.0 mg·L- 1 + potato juice 100 g·L- 1. Stems, PLBs and leaves of D. officinale had the highest content of polysaccharides, alkaloids and flavonoids, respectively. Naringenin was only produced in stem; however, PLBs with high alkaloid content can replace other organs producing alkaloids. The hot water extraction method outperformed the ultrasound-assisted extraction method for extracting polysaccharides from D. officinale. A comparative transcriptome analysis of PLBs and leaves of D. officinale revealed differential expression of genes encoding enzymes involved in polysaccharide, alkaloid and flavonoid biosynthetic pathways. Putative genes encoding enzymes involved in these biosynthetic pathways were identified. Notably, we identified genes encoding the alkaloid biosynthesis enzymes strictosidine β-D-Glucosidase, geissoschizine synthase and vinorine synthase in D. officinale. CONCLUSIONS: The identification of candidate genes encoding enzymes involved in metabolite biosynthesis will help to explore and protect this endangered species and facilitate further analysis of the molecular mechanism of secondary metabolite biosynthesis in D. officinale.
Authors: Tzi Bun Ng; Jingyi Liu; Jack Ho Wong; Xiujuan Ye; Stephen Cho Wing Sze; Yao Tong; Kalin Yanbo Zhang Journal: Appl Microbiol Biotechnol Date: 2012-02-10 Impact factor: 4.813