超氧阴离子通过提高[Ca^(2+)]cyt调节保卫细胞K+通道和气孔运动

SUPEROXIDE ANION REGULATES THE K^+ CHANNEL ACTIVITY AND STOMATAL MOVEMENT BY INCREASING GUARD CELL CYTOSOLIC FREE CALCIUM IN Vicia faba L

氧化信号参与了许多生理过程的调控。用膜片钳和激光共聚焦显微镜,采用可以产生O2·的甲基紫精处理蚕豆(ViciafabaL)保卫细胞,测定了O2·对气孔运动调节过程中胞质Ca2+离子浓度和细胞质膜K+通道活性的变化,结果表明甲基紫精可以促进气孔的关闭,乙二醇四乙酸酯(Ethylene glycol bis(2-aminoethyl)tetra-acetic acid, EGTA)、抗坏血酸(Ascorbic acid, AsA)和过氧化物酶(Catalase, CAT)可以消除小于10-5 mol/L 甲基紫精对气孔运动的影响;10-7 和10-5 mol/L的甲基紫精可使保卫细胞胞质Ca2+浓度有不同程度提高,并伴随有钙震荡。蚕豆气孔保卫细胞质膜内向K+通道可被胞外甲基紫精抑制,而这种抑制和[Ca2+]cyt有关。推测甲基紫精产生的O2·对蚕豆气孔运动的调节,主要是通过O2·诱导的胞内游离Ca2+浓度的升高,从而抑制了通过保卫细胞质膜K+内向电流。

It is well known that the activated oxygen species, acting as signaling molecules, regulate various biological processes. Here using an epidermal strip bioassay, Laser Scanning Confocal Microscope and patch clamp technique. The first evidence that superoxide anion involves in K+ channel activity and stomatal closure was provided by increasing the guard cell cytosolic free calcium (cyt) in Vicia faba. The results indicate that 10-3~10-7 mol/L methyl viologen, which could generate superoxide anion, induce stomatal closure and inhibit stomatal opening. The effect of lower concentration(10-5~ 10-7 mol/L)methyl viologen-induced stomatal closure can be abolished partly by 2 mmol/L EGTA(chelator of Ca2+)?ascorbic acid and catalase. The cyt of guard cells was increased by 10 -7mol/L of methyl viologen. In addition, the inward K+ channel current in plasma membrane of guard cell was decreased after 15 min by adding 10 -7mol/L of methyl viologen. However, the decrease of K+ current induced by superoxide anion was blocked by adding 2 mmol/L EGTA, implying the inhibition of K+ channel activity resulting from Ca2+ signaling. This suggests that the mechanism of superoxide anion induced stomatal closure is mainly due to inhibition the K+ channel activity, which Ca2+ signal invoveld.