Compatible solutes reduce ROS‐induced potassium efflux in Arabidopsis roots

Abstract

Reactive oxygen species (ROS) are known to be primarily responsible for the impairment of cellular function under numerous abiotic and biotic stress conditions. In this paper, using non-invasive microelectrode ion flux measuring (MIFE) system, we show that the application of a hydroxyl radical (OH • )-generating Cu 2+ /ascorbate (Cu/a) mixture to Arabidopsis roots results in a massive, dose-dependent efflux of K + from epidermal cells in the elongation zone. Pharmacological experiments suggest that both outwardrectifying K + channels and non-selective cation channels (NSCCs) mediate such effluxes. Low (5 mM) concentrations of compatible solutes (glycine betaine, proline, mannitol, trehalose or myo-inositol) significantly reduces OH • -induced K + efflux, similar to our previous reports for NaCl-induced K + efflux. Importantly, a significant reduction in K + efflux was found using osmolytes with no reported free radical scavenging activity, as well as those for which a role in free radical scavenging has been demonstrated. This indicates that compatible solutes must play other (regulatory) roles, in addition to free radical scavenging, in mitigating the damaging effects of oxidative stress.

Foliar Spray of Proline Enhanced the Photosynthetic Efficiency and Antioxidant System in Brassica juncea

“…Exogenous application of proline reduces cellular ROS level indicating its free radical scavenging potential (Cuin and Shabala, 2007), which also confers enhanced activity of antioxidant enzymes, i.e., CAT, POX, and SOD (Hoque et al, 2007;Ahmed et al, 2010). Similar inferences have been observed in the present study where exogenous proline application enhanced the activity of these antioxidant enzymes (Fig.…”

“…4A-C), which was more in 'Varuna' and lesser in 'RH-30'. This is further confirmed by the findings of Cuin and Shabala (2007), Ashraf and Foolad (2007) and Wani et al (2012) where proline increased activities of these enzymes by acting at the level of transcription and/or translation.…”

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

“…The largest amino acid increase was for Orn (5.83-fold in the apex; Table I). Physiologically relevant concentrations of Orn have been shown to result in an increased stress-induced K + efflux from roots (Cuin and Shabala, 2007), which could explain the poor K + retention ability in the root apex reported in this study.…”

Glycinebetaine improves salt tolerance in vinal (Prosopis ruscifolia Griesbach) seedlings

“…Thus, the involvement of compatible solutes in ROS signaling and the regulation of membrane transport in planta remain to be shown. Recently, Cuin and Shabala (2007) found that low (5 mM) concentrations of compatible solutes (glycine betaine, proline, mannitol, trehalose or myo-inositol) significantly reduces OH…”

“…Glycinebetaine (GB) appears to play an important role in the response of plant cells to a variety of stresses (Sakamoto and Murata, 2002). Current research efforts are focused on the elucidation of the mechanisms by which GB protects the cellular machinery in vivo and how, as a result, it enhances the tolerance of whole plants to environmental stress (Cuin and Shabala, 2007). In a previous work (Meloni et al, 2004), we found that an increase in endogenous GB levels may be important for osmotic adjustment in Prosopis alba under salinity stress.…”