H₂O₂ and cytosolic Ca²⁺ signals triggered by the PM H⁺‐coupled transport system mediate K⁺/Na⁺ homeostasis in NaCl‐stressed Populus euphratica cells

Abstract

Using confocal microscopy, X‐ray microanalysis and the scanning ion‐selective electrode technique, we investigated the signalling of H2O2, cytosolic Ca2+ ([Ca2+]cyt) and the PM H+‐coupled transport system in K+/Na+ homeostasis control in NaCl‐stressed calluses of Populus euphratica. An obvious Na+/H+ antiport was seen in salinized cells; however, NaCl stress caused a net K+ efflux, because of the salt‐induced membrane depolarization. H2O2 levels, regulated upwards by salinity, contributed to ionic homeostasis, because H2O2 restrictions by DPI or DMTU caused enhanced K+ efflux and decreased Na+/H+ antiport activity. NaCl induced a net Ca2+ influx and a subsequent rise of [Ca2+]cyt, which is involved in H2O2‐mediated K+/Na+ homeostasis in salinized P. euphratica cells. When callus cells were pretreated with inhibitors of the Na+/H+ antiport system, the NaCl‐induced elevation of H2O2 and [Ca2+]cyt was correspondingly restricted, leading to a greater K+ efflux and a more pronounced reduction in Na+/H+ antiport activity. Results suggest that the PM H+‐coupled transport system mediates H+ translocation and triggers the stress signalling of H2O2 and Ca2+, which results in a K+/Na+ homeostasis via mediations of K+ channels and the Na+/H+ antiport system in the PM of NaCl‐stressed cells. Accordingly, a salt stress signalling pathway of P. euphratica cells is proposed.

Salt-induced expression of genes related to Na+/K+ and ROS homeostasis in leaves of salt-resistant and salt-sensitive poplar species

“…It is interesting to note that ST salinity caused a significant increase of H 2 O 2 in P. euphratica (Fig. 2), indicating that H 2 O 2 acts as a stress signal to mediate plant stress adaptation (Sun et al 2010). Our microarray data show that the capacity to retain K ?…”

Mangrove root: adaptations and ecological importance

“…A common strategy involves the transport restriction of excess Na ? via inhibiting non-selective cation channels (NSCCs) in the root cells (Sun et al 2010). Moreover, halophytes can elevate the Na ?…”

Paxillus involutus Strains MAJ and NAU Mediate K+/Na+ Homeostasis in Ectomycorrhizal Populus × canescens under Sodium Chloride Stress

“…Salinized P. 3 canescens exhibited an enhanced capacity to maintain K + /Na + homeostasis in the presence of fungal colonization (strains MAJ and NAU). The maintenance of K + /Na + homeostasis is crucial for P. 3 canescens to tolerate saline conditions (Chen et al, 2001(Chen et al, , 2002a(Chen et al, , 2002b(Chen et al, , 2003Sun et al, 2009aSun et al, , 2009bSun et al, , 2010Chen and Polle, 2010). SEM-EDX microanalysis data indicate that the high K + /Na + ratio in mycorrhizal plants was the result of less Na + accumulation and K + reduction under NaCl stress than in NM plants (Fig.…”

“…Colonization with P. involutus strain MAJ reduces the buildup of Na + but enhances K + accumulation in the leaves of a salt-sensitive hybrid poplar, Populus 3 canescens (Langenfeld-Heyser et al, 2007, Luo et al, 2011. The maintenance of a high K + /Na + ratio is critical for salt tolerance in herbaceous plants (Shabala, 2000;Tester and Davenport, 2003;Chen et al, 2007;Shabala and Cuin, 2008) and woody species, including Populus species (Chen et al, 2001(Chen et al, , 2002a(Chen et al, , 2002b(Chen et al, , 2003Sun et al, 2009aSun et al, , 2009bSun et al, , 2010Sun et al, , 2012. At the cellular level, salinized plants avoid Na + toxicity in the cytosol by compartmentalizing Na + into the vacuole and excreting Na + into the external environment or the apoplast (Blumwald et al, 2000;Hasegawa et al, 2000;Zhu, 2001Zhu, , 2003Ottow et al, 2005;Apse and Blumwald, 2007;Munns and Tester, 2008;Chen and Polle, 2010).…”