RECEPTOR-MEDIATED ACTIVATION OF A PLANT CA2-PERMEABLE ION-CHANNEL INVOLVED IN PATHOGEN DEFENSE()

Pathogen recognition at the plant cell surface typically results in th e initiation of a multicomponent defense response. Transient influx of Ca2+ across the plasma membrane is postulated to be part of the signa ling chain leading to pathogen resistance, Patch-clamp analysis of par sley protoplasts revealed a novel Ca2+-permeable, La3+- sensitive plas ma membrane ion channel of large conductance (309 pS in 240 mM CaCl2), At an extracellular Ca2+ concentration of 1 mM, which is representati ve of the plant cell apoplast, unitary channel conductance was determi ned to be 80 pS, This ion channel (LEAC, for large conductance elicito r-activated ion channel) is reversibly activated upon treatment of par sley protoplasts with an oligopeptide elicitor derived from a cell wal l protein of Phytophthora sojae, Structural features of the elicitor f ound previously to be essential for receptor binding, induction of def ense-related gene expression, and phytoalexin formation are identical to those required for activation of LEAC, Thus, receptor-mediated stim ulation of this channel appears to be causally involved in the signali ng cascade triggering pathogen defense in parsley.