ROS-Activated Ion Channels in Plants: Biophysical Characteristics, Physiological Functions and Molecular Nature

Abstract

Ion channels activated by reactive oxygen species (ROS) have been found in the plasma membrane of charophyte Nitella flixilis, dicotyledon Arabidopsis thaliana, Pyrus pyrifolia and Pisum sativum, and the monocotyledon Lilium longiflorum. Their activities have been reported in charophyte giant internodes, root trichoblasts and atrichoblasts, pollen tubes, and guard cells. Hydrogen peroxide and hydroxyl radicals are major activating species for these channels. Plant ROS-activated ion channels include inwardly-rectifying, outwardly-rectifying, and voltage-independent groups. The inwardly-rectifying ROS-activated ion channels mediate Ca2+-influx for growth and development in roots and pollen tubes. The outwardly-rectifying group facilitates K+ efflux for the regulation of osmotic pressure in guard cells, induction of programmed cell death, and autophagy in roots. The voltage-independent group mediates both Ca2+ influx and K+ efflux. Most studies suggest that ROS-activated channels are non-selective cation channels. Single-channel studies revealed activation of 14.5-pS Ca2+ influx and 16-pS K+ efflux unitary conductances in response to ROS. The molecular nature of ROS-activated Ca2+ influx channels remains poorly understood, although annexins and cyclic nucleotide-gated channels have been proposed for this role. The ROS-activated K+ channels have recently been identified as products of Stellar K+ Outward Rectifier (SKOR) and Guard cell Outwardly Rectifying K+ channel (GORK) genes.

Phosphate Starvation Alters Abiotic-Stress-Induced Cytosolic Free Calcium Increases in Roots

“…Abiotic stress has been shown previously to cause an increase in root ROS accumulation, with NADPH oxidases implicated in their generation (Foreman et al, 2003;Demidchik et al, 2009). However, the activity of NADPH oxidases is usually linked to amplification of a [Ca 2+ ] cyt increase through activation of Ca 2+ influx across the plasma membrane (Foreman et al, 2003;Demidchik et al, 2009;Laohavisit et al, 2012;Demidchik, 2018). This is seemingly at odds with the loss of the second eATP-induced [Ca 2+ ] cyt increase under Pi starvation, and the paradigm of the ROS/Ca 2+ hub in signaling may not hold under Pi deprivation or in general conditions of high baseline ROS.…”

Role of Ca2+ in Mediating Plant Responses to Extracellular ATP and ADP

“…This provides a direct link between the kinase activity of P2K1 and the production of the second messenger, ROS, apparently without the need for an intermediate step of increased [Ca 2+ ] cyt . There are ROS-activated Ca 2+ channels in plants [ 30 ], so the influx of Ca 2+ across the plasma membrane induced by eATP could be a downstream effect of an earlier-induced increase in ROS. An early report implicated Arabidopsis annexin, AnnAt1, as playing a key role in this induced Ca 2+ influx in root epidermal cells [ 31 ].…”

Coping With Water Shortage: An Update on the Role of K+, Cl-, and Water Membrane Transport Mechanisms on Drought Resistance

“…WD is rapidly sensed by plant cells and significant advances in the identification of sensing mechanisms have been made in the last years. Reactive oxygen species and Ca +2 signaling enter the scene very early and allow shaping and propagation of the signal (Demidchik, 2018). When WD takes place at the soil level, a root-to-shoot transmission of the WD signal seems to be mediated to some extent by sulfate which precedes abscisic acid (ABA) synthesis in leaf tissues (Ernst et al, 2010;Malcheska et al, 2017;Batool et al, 2018).…”