Effects of elicitor and suppressor from a pea pathogen, Mycosphaerella pinodes, on Pl etabolism in pea plasma membrane were examined in vitro. The elicitor induced rapid phosphorylation of phosphatidylinositols as well as production of lysophospholipid in plasma membranes, but these responses were severely inhibited by the suppressor. These results indicate that a membrane-associated phospholipase A is regulated coordinately by fungal signals, together with Pl metabolism, and that it may participate in signal transduction pathways leading to defense responses. To evaluate a possible rote of phospholipase A activation in induction of a pea defense response, the effect of free fatty acid on induction of a phytoalexin accumulation was also examined. When pea leaves were treated with linoleic- or linolenic acid, most commonly released in plant cells by phospholipase A, the accumulation of pisatin was induced even in the absence of the elicitor. It is, therefore, conceivable that free fatty acid(s) released from plasma membrane is also implicated in the early stage of elicitor-signal transduction in pea.
pea(Pisum sativum L.)
polyphosphoinositide metabolism(Pl metabolism)