Root Plasma Membrane Transporters Controlling K+/Na+ Homeostasis in Salt-Stressed Barley

Abstract

Plant salinity tolerance is a polygenic trait with contributions from genetic, developmental, and physiological interactions, in addition to interactions between the plant and its environment. In this study, we show that in salt-tolerant genotypes of barley (Hordeum vulgare), multiple mechanisms are well combined to withstand saline conditions. These mechanisms include: (1) better control of membrane voltage so retaining a more negative membrane potential; (2) intrinsically higher H 1 pump activity; (3) better ability of root cells to pump Na 1 from the cytosol to the external medium; and (4) higher sensitivity to supplemental Ca 21 . At the same time, no significant difference was found between contrasting cultivars in their unidirectional 22 Na 1 influx or in the density and voltage dependence of depolarization-activated outward-rectifying K 1 channels. Overall, our results are consistent with the idea of the cytosolic K 1 -to-Na 1 ratio being a key determinant of plant salinity tolerance, and suggest multiple pathways of controlling that important feature in salt-tolerant plants. Intracellular K1 /Na 1 homeostasis is crucial for cell metabolism and is considered to be a key component of salinity tolerance in plants (Niu et al

Cell-Type-Specific H+-ATPase Activity in Root Tissues Enables K+ Retention and Mediates Acclimation of Barley (Hordeum vulgare) to Salinity Stress

“…Intrinsically higher H + -ATPase activity is essential to prevent this shift and to fuel the active K + uptake via H + -coupled cotransport. Strong positive correlation between H + -ATPase activity and salinity stress tolerance has been reported for several species , including barley (Chen et al, 2007). Here, we show that this can also explain the differential K + retention (and overall salinity stress sensitivity) between apical and mature root tissues (Fig.…”

“…After removing the root debris, released protoplasts were washed by a solution applied for patch-clamp assays (see below), and those attached for the bottom were used for further experiments. Protoplasts with a whole-cell capacitance of 5 to 10 pF (of epidermal origin; for justification, see Chen et al, 2007) were used in the experiments. Measurements were made by means of an Axopatch 200A patch-clamp amplifier (Axon Instruments).…”

Acclimation improves salt stress tolerance in Zea mays plants

“…transition to programmed cell death; Shabala et al, 2007;Shabala and Pottosin, 2014). For this reason, a strong correlation between plant's K + retention ability and salt tolerance has been observed in both root (Chen et al, 2007;Cuin et al, 2008;Smethurst et al, 2008) and leaf (Wu et al, 2013) tissues in several species. Another key determinant of salinity tolerance is Na + exclusion from the cytosol.…”

“…Net K + , Na + and H + fluxes were measured using the non-invasive microelectrode ion flux estimation (MIFE) technique (UTas Innovation Ltd, Hobart, Tasmania) as described elsewhere (Chen et al, 2007;Bose et al, 2014). The electrode travel range was 100 m, between 50 and 150 m from the root surface.…”

“…One of the hallmarks of detrimental effects of salinity at the tissue level is K + efflux from plant roots Cuin et al, 2012;Wu et al, 2013) via both depolarization-activated outward-rectifying K + (KOR; Chen et al, 2007) and ROS-activated non-selective cation (NSCC; Bose et al, 2014) channels. This efflux disturbs cytosolic K + homeostasis (Cuin et al, 2003), with major implications to cell metabolism and its fate (e.g.…”