Study Of Magnesium And Hydrogen Peroxide Effect On Slow Vacuolar Ion Channel In Radish By Patch-Clamp

The slow vacuolar (SV) channel was the first tonoplast channel to be characterized. The channel is ubiquitous in most higher plants and it is an essential element in most cells. SV channel has a strong calcium dependence, and the SV current would increase with the increase of free cytoscolic Ca2+ concentration. Since Mg2+ and Ca2+ belong to the same main group and cytosolic Ca2+ can activative SV channel, can cytosolic Mg2+ activative it? Some people think that Mg2+ can activative SV channel; others hold the view that Mg2+ cannot instead of Ca2+ activate SV channel. In this paper, we give voice to this matter.As we added 4 mmol/L EGTA to the bath solution, the SV channel inactivation and nearly no any current was recorded. In the presence of 4 mmol/L EGTA, even 10 mmol/L Mg2+ could not activate SV currents. However, when Ca2+ was added to the bath solution, SV channel current was activated again, which suggesting mat cytosolic Ca2+ could activate SV channel reversibility and cytosolic Mg2+ could not. Further studied demonstrated that cytosolic Mg2+ reduced the SV currents in a concentration-dependent manner. The data were fitted by a Hill equation with a K, of 1.94±0.11 mmol/L and a Hill conefficient of 1.92±0.18 indicates two Mg2+ binding sites per SV channel. These results support strongly the view that Mg2+ can block many channels and it has antagonistic action to Ca2+.Reactive oxygen species (ROS) has been shown to exert various biological effects in both animals and plants. It can react with various cellular targets, damage DNA and proteins, result in lipid peroxidation and cell dysfunction. The action mechanism of ROS at cell level is still unclear. Here we report the first evidence that H2O2 regulated the activation of ion channel in the tonoplast of high plants. Using the patch-clamp techniques, we have demonstrated mat in tonoplast from the taproot of the Radish, H2O2, added at the cytosolic side of the vacuole, reduced the current carried by SV channel in a concentration-dependent, time-dependent and voltage-dependent manner. Added ROS scavenger ascorbic acid cannot eliminate the effects of H2O2. Furthermore, luminal H2O2 at low concentration lead to SV current increase drastically. These results suggested that H2O2 at the both sides of tonoplast is involved in the regulation of SV channel. This will provide an important basis at channel level for the researching further the effects of H2O2 on physiological activities of plants.