It is not all about sodium: revealing tissue specificity and signalling roles of potassium in plant responses to salt stress

Abstract

Background Salinity is a global issue threatening agricultural production systems across the globe. While the major focus of plant salinity stress tolerance research has been on sodium, the transport and physiological roles of K+ in plant salt stress response has received less attention. This review attempts to bridge this knowledge gap. Scope The major emphasis is on newly proposed K+ signalling roles and plant salt tolerance cell-and tissuespecificity. In addition to summarizing the importance of K+ retention for plant salt tolerance, we focus onaspects that were not the subject of previous reviews including (1) the importance of HAK/KUP family of transporters in K+ uptake in salt stressed plants and its possible linkage with Ca2+ and ROS signalling; (2) control of xylem K+ loading in salt stressed plants, control of phloem K+ recirculation in salt stressed plants and the potential importance of plant's ability to efficiently coordinate K+ signals between root and shoot;(3) the buffering capacity of the vacuolar K+ pool; and(4) mechanisms of restoring the basal cytosolic K+ levels by coordinated activity of tonoplast K+-permeable channels. Conclusions Overall, this review emphasises the need to fully understand the newly emerging roles of K+ and regulation of its transport for improving salinity stress tolerance in plants.

Vigour/tolerance trade‐off in cultivated sunflower (Helianthus annuus) response to salinity stress is linked to leaf elemental composition

“…Alternatively, decreasing leaf level K + and S concentrations could be indicative of a redistribution of these elements to the roots. Indeed, across seven crop species, maintenance of root K + concentrations has been shown to be negatively correlated with shoot K + concentration (Wu, Zhang, Giraldo, & Shabala, ), and root sulphur content in the form of sulpholipids has been linked to salt tolerance (Erdei, Stuiver, & Kuiper, ; Stuiver, Kuiper, Marschner, & Kylin, ). These results suggest K + and S to play a role in salinity tolerance, but likely not in the leaf.…”

Cation Specificity of Vacuolar NHX-Type Cation/H+ Antiporters

“…The experimental evidence strongly supports a role in Na + transport under saline conditions, but more recent functional studies also point to basic roles of vacuolar NHXs under nonsaline conditions that go beyond stress acclimation . In addition to the compartmentation of Na + in the vacuole, NHXs may contribute to salinity tolerance by favorably adjusting cellular K + homeostasis under saline conditions (Ma et al, 2017;Wu et al, 2018).…”

A rice really interesting new gene H2‐type E3 ligase, OsSIRH2‐14, enhances salinity tolerance via ubiquitin/26S proteasome‐mediated degradation of salt‐related proteins

“…Furthermore, ZmHKT2 Crispr mutants had significantly improved growth and a greater K + and lower Na + content than the WT plants under saline conditions (100‐mM NaCl solution‐saturated soil; Y. Gao et al, ). With the onset of salt stress, the plasma membrane potential is rapidly depolarized by the activation of voltage‐gated guard cell outward rectifying K + channels (GORKs) and ROS‐activated nonselective cation channels, resulting in K + efflux (Jayakannan, Bose, Babourina, Rengel, & Shabala, ; Wu, Zhang, Giraldo, & Shabala, ). Together, these data suggest that conditions of high salinity (200‐mM NaCl) with K + ‐starvation (normal watering) produce a high Na + influx by converting OsHKT2;1 to the Na + uniport mode in rice plants.…”

“…Gao et al, 2019). With the onset of salt stress, the plasma membrane potential is rapidly depolarized by the activation of voltage-gated guard cell outward rectifying K + channels (GORKs) and ROS-activated nonselective cation channels, resulting in K + efflux (Jayakannan, Bose, Babourina, Rengel, & Shabala, 2013;Wu, Zhang, Giraldo, & Shabala, 2018).…”