Abstract
Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca(2+) and K(+) channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K(+) channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H(2)O(2). We show that H(2)O(2) rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H(2)O(2) and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H(2)O(2)-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys(168) located within the S3 α-helix of the voltage sensor complex, to be essential for sensitivity to H(2)O(2). The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys(168) as a critical target for H(2)O(2), and implicate ROS-mediated control of the K(+) channel in regulating mineral nutrient partitioning within the plant.
Highlights
Among others (3), and in plants they are essential for development (4) and stress signaling, including drought (5, 6) and defense against pathogens (7)
Reactive oxygen species (ROS) affect non-selective cation channels during Fucus development (10); they regulate Ca2ϩ channels and Ca2ϩ-based signaling (5) as well as voltage-sensitive Kϩ channels of guard cells (11) that are important for stomatal movement; they contribute in responses to drought and pathogen defense (12); and they have been implicated in targeting Kϩ efflux during programmed cell death (13)
We report that Kϩ current through the heterologously expressed SKOR is modulated by H2O2, thereby identifying the Kϩ channel as a potential target for ROS, and we show that a single Cys within the voltage sensor complex is essential for its ROS sen
Summary
Among others (3), and in plants they are essential for development (4) and stress signaling, including drought (5, 6) and defense against pathogens (7). For development and signaling in plants, the activities of membrane ion channels are essential, often including their regulation by ROS. ROS affect non-selective cation channels during Fucus development (10); they regulate Ca2ϩ channels and Ca2ϩ-based signaling (5) as well as voltage-sensitive Kϩ channels of guard cells (11) that are important for stomatal movement; they contribute in responses to drought and pathogen defense (12); and they have been implicated in targeting Kϩ efflux during programmed cell death (13). SKOR is one of two Kϩ channels found in Arabidopsis thaliana that rectify strongly outward, thereby mediating Kϩ efflux from the cell It is expressed within the xylem parenchyma of the root where it facilitates Kϩ loading into the xylem (14), thereby contributing directly to Kϩ homeostasis and indirectly, through charge balance, to the transport of other solutes throughout the plant (12, 15). This Cys and adjacent sequences form a motif that shows extensive conservation among outward-rectifying Kvlike Kϩ channels, but only from land plants, suggesting that the motif may represent an important regulatory target specialized for the habit of plants in dry environments
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
