Effect of race-specific elicitors of Cladosporium fulvum on the tomato plasma membrane Ca2+-ATPase

The response of plant cells to invading pathogens is regulated by fluctuations in cytosolic Ca2+ concentrations. These concentrations are regulated by Ca2+ influx, mediated by plasma membrane Ca2+ channels, and of Ca2+ efflux, regulated by the plasma membrane Ca2+-ATPase. The effect of race-specific elicitors on this Ca2+-ATPase was examined using elicitor-containing intercellular fluids prepared from infected tomato leaves inoculated with specific races of intercellular fluids from Cf-5-incompatible but not from Cf-5-compatible races of C.fulvum resulted in the inhibition of the Ca2+-ATPase. In vivo treatment of tomato cells with an elicitor from an incompatible race resulted in inhibition of the plasma membrane Ca2+-ATPase activity during the first 30 min following elicitation with recovery of activity evident between 45 min and 1 h after elicitation and fully restored after 1.5 h. This inhibition was seen in trypsin-treated membranes, indicating that the effect of the incompatible elicitors on the Ca2+-ATPase was independent from modifications on the self-inhibitory domain of the pump. (C) 1998 Academic Press.