Journal Article

Fungal Elicitor Induces Singlet Oxygen Generation, Ethylene Release and Saponin Synthesis in Cultured Cells of <i>Panax ginseng</i> C. A. Meyer

Xiaojie Xu, Xiangyang Hu, Steven J. Neill, Jianying Fang and Weiming Cai

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 6, pages 947-954
Published in print June 2005 | ISSN: 0032-0781
Published online June 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci103
Fungal Elicitor Induces Singlet Oxygen Generation, Ethylene Release and Saponin Synthesis in Cultured Cells of Panax ginseng C. A. Meyer

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Singlet oxygen is a high-energy molecular oxygen species. As one of the most active intermediates involved in chemical and biochemical reactions, singlet oxygen plays essential roles in plant responses to UV and strong light. Here, we report that Cle, an elicitor derived from fungal cell walls, induces the generation of singlet oxygen in cell cultures of ginseng, Panax ginseng. Cle treatment also triggers the activation of plasma membrane NADPH oxidase and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), subsequently leading to ethylene release and increased saponin synthesis, as shown by increased mRNA expression of squalene synthase (SQS) and squalene epoxidase (SQE), and accumulation of β-amyrin synthase (β-AS). Suppression of Cle-induced singlet oxygen generation or inhibition of ethylene production blocks saponin synthesis, whereas treatment of ginseng cells with ethylene or singlet oxygen induces the synthesis of saponin. Together, these results indicate that Cle-induced production of both singlet oxygen and ethylene is required for saponin synthesis, and that singlet oxygen may function upstream of ethylene during Cle-induced saponin synthesis.

Keywords: Colletotrichum lagenarium; Ethylene; Panax ginseng; Saponin; Singlet oxygen; ACC, 1-aminocyclopropane-1-carboxylic acid; ACO, ACC oxidase; Ado-Met, S-adenosylmethionine; AOA, aminooxyacetic acid; β-AS, β-amyrin synthase; AVG, aminovinylglycine; Cle, an elicitor extracted from cell walls of Colletotrichum lagenarium; cPTIO, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide; DPI, diphenylene iodonium; MCP, 1-metylcyclopropene; NO, nitric oxide; OA, okadaic acid; RB, rose bengal; RR, ruthenium red; SQE, squalene epoxidase; SQS, squalene synthase; µg glc equiv. ml–1, µg glucose equivalents ml–1

Journal Article.  5241 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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