Multiple signalling pathways mediate fungal elicitor-induced beta-thujaplicin biosynthesis in Cupressus lusitanica cell cultures.
The biosynthesis of a phytoalexin, beta-thujaplicin, in Cupressus lusitanica cell cultures can be stimulated by a yeast elicitor, H(2)O(2), or methyl jasmonate. Lipoxygenase activity was also stimulated by these treatments, suggesting that the oxidative burst and jasmonate pathway may mediate the elicitor-induced accumulation of beta-thujaplicin. The elicitor signalling pathway involved in beta-thujaplicin induction was further investigated using pharmacological and biochemical approaches. Treatment of the cells with calcium ionophore A23187 alone stimulated the production of beta-thujaplicin. A23187 also enhanced the elicitor-induced production of beta-thujaplicin. EGTA, LaCl(3), and verapamil pretreatments partially blocked A23187- or yeast elicitor-induced accumulation of beta-thujaplicin. These results suggest that Ca(2+) influx is required for elicitor-induced production of beta-thujaplicin. Treatment of cell cultures with mastoparan, melittin or cholera toxin alone or in combination with the elicitor stimulated the production of beta-thujaplicin or enhanced the elicitor-induced production of beta-thujaplicin. The G-protein inhibitor suramin inhibited the elicitor-induced production of beta-thujaplicin, suggesting that receptor-coupled G-proteins are likely to be involved in the elicitor-induced biosynthesis of beta-thujaplicin. Indeed, both GTP-binding activity and GTPase activity of the plasma membrane were stimulated by elicitor, and suramin and cholera toxin affected G-protein activities. In addition, all inhibitors of G-proteins and Ca(2+) flux suppressed elicitor-induced increases in lipoxygenase activity whereas activators of G-proteins and the Ca(2+) signalling pathway increased lipoxygenase activity. These observations suggest that Ca(2+) and G-proteins may mediate elicitor signals to the jasmonate pathway, and the jasmonate signalling pathway may then lead to the production of beta-thujaplicin.
Zhao
Jian
J
Laboratory of Forest Biochemistry, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan. jzhao@ksu.edu
Sakai
Kokki
K
D000085:Acetates / Q000494:pharmacology; D000001:Calcimycin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D029781:Cupressus / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology; D003517:Cyclopentanes / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005658:Fungi / Q000254:growth & development*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D007811:Lanthanum / Q000494:pharmacology; D008084:Lipoxygenase / Q000096:biosynthesis; D039821:Monoterpenes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054883:Oxylipins; D010455:Peptides; D010937:Plant Growth Regulators / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013498:Suramin / Q000494:pharmacology; D014334:Tropolone / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology; D014862:Wasp Venoms / Q000494:pharmacology
D000085:Acetates; D003517:Cyclopentanes; D036341:Intercellular Signaling Peptides and Proteins; D039821:Monoterpenes; D054883:Oxylipins; D010455:Peptides; D010937:Plant Growth Regulators; D014862:Wasp Venoms; C028521:lanthanum chloride; D000001:Calcimycin; D004533:Egtazic Acid; D013498:Suramin; D007811:Lanthanum; C037500:mastoparan; D014334:Tropolone; C072239:methyl jasmonate; D002772:Cholera Toxin; D006861:Hydrogen Peroxide; D014700:Verapamil; D008084:Lipoxygenase; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D002118:Calcium; C009479:beta-thujaplicin