Ca²⁺-permeable channels in the plant pathogen response

Abstract

Production of ROS and hypersensitive cell death are characteristic features of the induced pathogen resistance in plants. Since Ca²⁺-signals precede the pathogen-induced cell death we have analyzed Ca²⁺-signals and Ca²⁺-channels involved in the responses to pathogen attack and ROS. For this purpose, we used the Ca²⁺-reporter protein aequorin as well as the combined single-cell fluorescence imaging and patch clamp technique. Moreover, we compared Ca²⁺-channel activities in Arabidopsis wild type and the pathogen-resistant mutant, dnd1 (Yu et al., 1998). Cellular responses to ROS were significantly reduced in dnd1. Since DND1 was shown to encode the Ca²⁺-permeable and cyclic nucleotide-gated ion channel CNGC2 (Clough et al., 2000), this channel represents a possible candidate for H₂O₂-dependent Ca²⁺ entry via the plasma membrane. We therefore thoroughly examined this hypothesis and will present a model on how CNGC2 transmits cellular responses to reactive oxygen species, a step essential for the control of hypersensitive cell death.