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

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.