Post‐transcriptional regulation of GORK channels by superoxide anion contributes to increases in outward‐rectifying K⁺ currents

Abstract

SummaryIon fluxes are ubiquitous processes in the plant and animal kingdoms, controlled by finetuned regulations of ion channel activity. Yet the mechanism that cells employ to achieve the modification of ion homeostasis at the molecular level still remains unclear. This is especially true when it comes to the mechanisms that lead to cell death.In this study, Arabidopsis thaliana cells were exposed to ozone (O 3 ). Ion flux variations were analyzed by electrophysiological measurements and their transcriptional regulation by RT-PCR. Reactive oxygen species (ROS) generation was quantified by luminescence techniques and caspase-like activities were investigated by laser confocal microscopy.We highlighted the delayed activation of K + outward-rectifying currents after an O 3 -induced oxidative stress leading to programmed cell death (PCD). Caspase-like activities are detected under O 3 exposure and could be decreased by K + channel blocker. Molecular experiments revealed that the sustained activation of K + outward current could be the result of an unexpected O ÁÀ 2 post-transcriptional regulation of the guard cell outward-rectifying K + (GORK) channels. This consists of a likely new mode of regulating the processing of the GORK mRNA, in a ROS-dependent manner, to allow sustained K + effluxes during PCD. These data provide new mechanistic insights into K + channel regulation during an oxidative stress response.

Ozone sensing and early signaling in plants: An outline from the cloud

“…Delayed activation of K + outward-rectifying currents was recently evidenced after O 3 -induced oxidative stress leading to programmed cell death (Tran et al, 2013). Thus a new, ROSdependent way of K + channel regulation during oxidative stress was highlighted: molecular experiments revealed that the sustained activation of K + outward currents could follow the unexpected post-transcriptional regulation of guard cell outwardrectifying K + (GORK) channels by O À 2 (Tran et al, 2013).…”

Reactive Oxygen Species-Dependent Nitric Oxide Production Contributes to Hydrogen-Promoted Stomatal Closure in Arabidopsis

“…Expression profiles revealed that this gene is up-regulated upon the onset of drought, salinity, and cold stress and ABA exposure (Becker et al, 2003;Tran et al, 2013). Reverse genetic evidence further showed that GORK plays an important role in the control of stomatal movements and allows the plant to reduce transpirational water loss significantly (Hosy et al, 2003) and participates in the regulation of salinity tolerance by preventing salt-induced K + loss (Jayakannan et al, 2013).…”

Ozone-induced caspase-like activities are dependent on early ion channel regulations and ROS generation inArabidopsis thalianacells

“…[1][2][3] This consist in an oxidative dependent controlled cell death process involving cell shrinkage due to an early activation of anion channel 1 and a delayed activation of K + outward currents, 2 but also to early events like Ca 2+ influx or singlet oxygen production possibly linked to mitochondrial dysfunction. 1 Here we provide evidence that most of these early events act downstream of caspase-like activities as recently demonstrated for K + channel activation.…”