title: Cloning and functional analysis of two sterol-C24-methyltransferase 1 (SMT1) genes from Paris polyphylla.
abstract: The biosynthetic pathways of phytosterols and steroidal saponins are located in two adjacent branches which share cycloartenol as substrate. The rate-limiting enzyme S-adenosyl-L-methionine-sterol-C24-methyltransferase 1 (SMT1) facilitates the metabolic flux toward phytosterols. It catalyzes the methylation of the cycloartenol in the side chain of the C24-alkyl group, to generate 24(28)-methylene cycloartenol. In this study, we obtained two full-length sequences of SMT1 genes from Pari polyphylla, designated PpSMT1-1 and PpSMT1-2. The full-length cDNA of PpSMT1-1 was 1369 bp long with an open reading frame (ORF) of 1038 bp, while the PpSMT1-2 had a length of 1222 bp, with a 1005 bp ORF. Bioinformatics analysis confirmed that the two cloned SMTs belong to the SMT1 family. The predicted function was further validated by performing in vitro enzymatic reactions, and the results showed that PpSMT1-1 encodes a cycloartenol-C24-methyltransferase, which catalyzes the conversion of cycloartenol to 24-methylene cycloartenol, whereas PpSMT1-2 lacked this catalytic activity. The tissue expression patterns of the two SMTs revealed differential expression in different organs of Paris polyphylla plants of different developmental stage and age. These results lay the foundation for detailed genetic studies of the biosynthetic pathways of steroid compounds, which constitute the main class of active substances found in P. polyphylla.
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Guan
authors.affiliation: b Institute of Chinese Materia Medica, Chinese Academy of Chinese Medical Sciences , Beijing 100700 , China.
authors.forename: Ping
authors.initials: P
authors.lastname: Su
authors.affiliation: b Institute of Chinese Materia Medica, Chinese Academy of Chinese Medical Sciences , Beijing 100700 , China.
authors.forename: Yu-Jun
authors.initials: YJ
authors.lastname: Zhao
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Xia-Nan
authors.initials: XN
authors.lastname: Zhang
authors.affiliation: c Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology , Chinese Academy of Sciences , Tianjin 300308 , China.
authors.forename: Zhu-Bo
authors.initials: ZB
authors.lastname: Dai
authors.affiliation: b Institute of Chinese Materia Medica, Chinese Academy of Chinese Medical Sciences , Beijing 100700 , China.
authors.forename: Juan
authors.initials: J
authors.lastname: Guo
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Yu-Ru
authors.initials: YR
authors.lastname: Tong
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Tian-Yuan
authors.initials: TY
authors.lastname: Hu
authors.affiliation: d School of Pharmaceutical Sciences, Guizhou University , Guiyang 550025 , China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yin
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Lin-Hui
authors.initials: LH
authors.lastname: Gao
authors.affiliation: a School of Traditional Chinese Medicine, Capital Medical University , Beijing 100069 , China.
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.affiliation: b Institute of Chinese Materia Medica, Chinese Academy of Chinese Medical Sciences , Beijing 100700 , China.
authors.forename: Lu-Qi
authors.initials: LQ
authors.lastname: Huang
mesh_terms: D001483:Base Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D004365:Drugs, Chinese Herbal; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D000070556:Melanthiaceae / Q000201:enzymology* / Q000235:genetics*; D008780:Methyltransferases / Q000235:genetics*; D008958:Models, Molecular; D015394:Molecular Structure; D016366:Open Reading Frames; D010840:Phytosterols / Q000378:metabolism; D014315:Triterpenes / Q000378:metabolism
chemical_list: D018744:DNA, Plant; D004365:Drugs, Chinese Herbal; D007527:Isoenzymes; D010840:Phytosterols; D014315:Triterpenes; D008780:Methyltransferases; C022670:delta 24-sterol methyltransferase; C100089:cycloartenol
keywords: Bioinformatics analysis; Paris polyphylla; cycloartenol-C24-methyltransferase; enzymatic reaction; expression pattern; steroid compound