RESUMEN
Using confocal microscopy, X-ray microanalysis and the scanning ion-selective electrode technique, we investigated the signalling of H(2)O(2), cytosolic Ca(2+) ([Ca(2+)](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. H(2)O(2) levels, regulated upwards by salinity, contributed to ionic homeostasis, because H(2)O(2) restrictions by DPI or DMTU caused enhanced K(+) efflux and decreased Na(+)/H(+) antiport activity. NaCl induced a net Ca(2+) influx and a subsequent rise of [Ca(2+)](cyt), which is involved in H(2)O(2)-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 H(2)O(2) and [Ca(2+)](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 H(2)O(2) and Ca(2+), 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.
Asunto(s)
Señalización del Calcio , Membrana Celular/metabolismo , Citosol/metabolismo , Homeostasis , Peróxido de Hidrógeno/metabolismo , Populus/citología , Estrés Fisiológico/efectos de los fármacos , Amilorida/farmacología , Transporte Biológico/efectos de los fármacos , Señalización del Calcio/efectos de los fármacos , Citosol/efectos de los fármacos , Homeostasis/efectos de los fármacos , Peróxido de Hidrógeno/farmacología , Potenciales de la Membrana/efectos de los fármacos , Populus/efectos de los fármacos , Populus/metabolismo , Potasio/metabolismo , Protones , Protoplastos/citología , Protoplastos/efectos de los fármacos , Protoplastos/metabolismo , Sodio/metabolismo , Cloruro de Sodio/farmacología , Vanadatos/farmacologíaRESUMEN
The ability of a plant to maintain an ionic homeostasis is crucial in plant salt tolerance. Direct evidence based on data from the non-invasive measurement of ion fluxes would not only offer new insight about the function of the transporter but also provide a whole plant approach for dissecting salt adaptation mechanisms. Here, we review some reports using the ion-selective microelectrodes to characterize the net ion fluxes of tissues or cells.