Suppression of pisatin production and ATPase activity in pea plasma membranes by orthovanadate, verapamil and a suppressor from mycosphaerella pinodes

A pea pathogen, Mycosphaerella pinodes, secretes both an elicitor and a suppressor for the accumulation of pisatin, a major phytoalexin of pea, into the spore germination fluid. The effects of the elicitor and the suppressor on the ATPase activity in pea plasma membranes was examined. The ATPase was sensitive to orthovanadate and dicyclohexylcarbodiimide but insensitive to nitrate and azide; it was unaffected by the elicitor but was markedly inhibited by the suppressor (50μg.ml^-1, bovine serum albumin equivalents) or verapamil (1OOμM). The accumulation of pisatin induced by the elicitor was delayed for 3 to 6 h in the presence of orthovanadate or verapamil to an extent similar to that in the presence of the suppressor. The relationship between the inhibition of plasma membrane ATPase activity and the suppression of the active defense reaction that involves the production of pisatin in the pea plant is discussed.