Regulation of tobacco lipoxygenase by methyl jasmonate and fatty acids

Lipoxygenase (LOX) activity and gene expression have been described previou sly to be induced in tobacco by fungal infection and elicitor treatment. We now report that LOX activity is induced in tobacco cell suspensions by tre atment with methyl jasmonate (MeJa). This compound had no effect on the in vitro activity of tobacco LOX. Induction of LOX activity is a dose-dependen t response with a maximum around 890 mu M MeJa. Linolenic acid, the precurs or for jasmonate synthesis, also induces LOX activity. When applied togethe r with fungal elicitor, linolenic acid drastically increases and prolongs t he induction of LOX activity. LOX activity and gene expression in elicited tobacco cells are partially inhibited by pretreatment with eicosatetraynoic acid (ETYA), a potent inhibitor of tobacco LOX in vitro. The induction by methyl jasmonate, in contrast, was not inhibited by ETYA pretreatment. Thes e data suggest that induction of LOX gene expression and activity upon elic itation are regulated at least partially by LOX products. (C) Academie des Sciences / Elsevier, Paris.