Abstract
Cultured rice-plant cells treated with N-cyanomethyl-2-chloro-isonicotinamide (NCI) and supplied with blast fungus hyphal component (BFHC) augmentated phenylalanine ammonia-lyase (PAL) more than those given BFHC alone. Enhancement of phosphatidylinositol (PI) metabolism and increase of ethylene production preceded increase of PAL activity. The enhancement of PI metabolism and the increase of ethylene production always occurred earlier in NCI-pretreated, stimulated cells than in NCI-nonpretreated, stimulated cells. Ethylene was produced in large amount from [U-14C] glutamic acid in the stimulated cells but only in trace amount from L-[U-14C] methionine, which suggested that the glutamic acid pathway mainly contributed to ethylene biosynthesis in the cells. Augmentation of PAL activity by BFHC was inhibited by the specific calmodulin inhibitor W-7, and Ca2+-binding proteins such as calmoduline appeared to mediate biosignal transduction from membrane receptors to cellular effector systems. The rate of PAL-activity inhibition by W-7 was compensated to one half in the NCI-pretreated cells. These results suggest that NCI accelerate the operation of biosignal transduction in an early stage of elicitation process and promote PAL activation in the stimulated cells.
