Suppression of camptothecin biosynthetic genes results in metabolic modification of secondary products in hairy roots of Ophiorrhiza pumila.
Camptothecin is a monoterpenoid indole alkaloid that exhibits anti-tumor activity. In Ophiorrhiza pumila, production of camptothecin and its related alkaloids was high in the hairy roots, but not in the cell suspension culture derived from hairy roots. To identify the intermediates in camptothecin biosynthesis, expression of genes encoding tryptophan decarboxylase (TDC) and secologanin synthase (SLS), the two enzymes catalyzing the early steps in camptothecin biosynthesis, were suppressed in the hairy roots of O. pumila by RNA interference (RNAi), and metabolite changes were investigated. In most TDC- and SLS-suppressed lines, accumulation of camptothecin and related alkaloids, strictosidine, strictosamide, pumiloside, and deoxypumiloside was reduced. The accumulation levels of secologanin exhibited a strong negative correlation with the expression level of TDC, and that of loganin exhibited a negative correlation with the expression level of SLS. Some hairy root-specific chromatographic peaks detected by liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR-MS) exhibited positive or negative correlation with TDC expression, suggesting their possible involvement in camptothecin biosynthesis.
Graduate School of Pharmaceutical Sciences, Chiba University, Chuo-ku, Chiba, Japan.
Takashi
T
Asano
Kanae
K
Kobayashi
Emi
E
Kashihara
Hiroshi
H
Sudo
Ryosuke
R
Sasaki
Yoko
Y
Iijima
Koh
K
Aoki
Daisuke
D
Shibata
Kazuki
K
Saito
Mami
M
Yamazaki
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000235:genetics / Q000378:metabolism; D055162:Biocatalysis; D002166:Camptothecin / Q000096:biosynthesis* / Q000737:chemistry; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000378:metabolism*; D034622:RNA Interference; D019666:Rubiaceae / Q000201:enzymology / Q000378:metabolism*
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; C404963:secologanin synthase; D044925:Oxidoreductases Acting on CH-CH Group Donors; D001142:Aromatic-L-Amino-Acid Decarboxylases; D002166:Camptothecin