title: Mitogen-activated protein kinases mediate the oxidative burst and saponin synthesis induced by chitosan in cell cultures of Panax ginseng.
abstract: Chitosan (CHN) specially induced the activities of 39 kD and 42 kD protein kinases in ginseng cells, which could be suppressed by an inhibitor of mitogen-activated protein kinase (MAPK) pathway, PD98059. The immunoprecipitation (IP) using MAPK antibody or kinase assay in vitro also showed that CHN-induced 42 kD and 39 kD protein kinases belonged to the MAPK family. PD98059 suppressed CHN-induced transcriptions of ginseng squalene synthase and ginseng squalene epoxidase genes (gss and gse), CHN-induced accumulation of beta-Amyrin synthase (beta-AS) and synthesis of saponin. These results showed that CHN-induced activities of MAPKs were necessary for the CHN-induced saponin synthesis. EGTA and LaCl3 suppressed CHN-induced 39 kD and 42 kD MAPK activities. Ruthenium red (RR) could suppress CHN-induced 39 kD activity. All of them suppressed CHN-induced saponin synthesis. These results indicated that CHN-induced increment of cytosolic calcium was necessary for CHN-induced saponin synthesis. PD98059 also suppressed CHN-induced oxidative burst (including the increment of activity of plasma membrane NADPH oxidase and production of H2O2), but diphenylene iodonium (DPI), dimethylthiourea (DMTU) and 2,5-dihydroxycinnamic acid methyl ester (DHC) could not suppress CHN-induced MAPK activities, which indicated that MAPK was possibly function upstream of CHN-induced oxidative burst.
authors.affiliation: Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Hu
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Neill
authors.forename: Jianying
authors.initials: J
authors.lastname: Fang
authors.forename: Weiming
authors.initials: W
authors.lastname: Cai
authors.forename: Zhangcheng
authors.initials: Z
authors.lastname: Tang
mesh_terms: D002460:Cell Line; D048271:Chitosan / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D008970:Molecular Weight; D019255:NADPH Oxidases / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D005894:Panax / Q000187:drug effects* / Q000378:metabolism*; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D016897:Respiratory Burst / Q000187:drug effects*; D012503:Saponins / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D010940:Plant Proteins; D012503:Saponins; D010769:Phosphothreonine; D010768:Phosphoserine; D048271:Chitosan; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D020928:Mitogen-Activated Protein Kinases