Exposure to a natural nitric oxide donor negatively affects the potential influx of rubidium in potassium-starved Arabidopsis plants

Abstract

Nitric oxide (NO) and potassium (K+) exert a profound influence on the acclimation of plants to multiple stress conditions. A recent report indicated that exogenous addition of an NO donor causes, under conditions of adequate K+ supply, a detrimental effect on K+ status. It remains unknown whether an exogenous NO source could negatively affect the potential capture of this element when plants are faced with a K+ shortage. In this work we offer evidence that, under conditions of K+-deprivation, the addition of the naturally occurring NO donor, S-nitrosoglutathione (GSNO), diminishes the potential inward transport of the K+-analogue rubidium (Rb+) from diluted Rb+ concentrations in Arabidopsis thaliana. Studies with the akt1-2 mutant, lacking the AKT1 inward-rectifier K+-channel involved in K+-uptake, unveiled that the effect of GSNO on Rb+-influx involves a non-AKT1 component. In addition, exposure to the NO-donor led to down-regulation of transcripts coding for the AtHAK5 K+-transporter, a major component of the K+-transport machinery in K+-deprived plants. Moreover, studies with the hak5 mutant showed that GSNO could either stimulate Rb+-uptake or does not lead to a significant effect on Rb+-uptake relative to –K+ and to –K+ in the presence of decayed GSNO, respectively, thus indicating that the presence of AtHAK5 is required for GSNO exerting an inhibitory effect.