Mitogen-activated protein kinases mediate the oxidative burst and saponin synthesis induced by chitosan in cell cultures of Panax ginseng.
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.
Hu
Xiangyang
X
Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Neill
Steven J
SJ
Fang
Jianying
J
Cai
Weiming
W
Tang
Zhangcheng
Z
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
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