A role for the vacuole in auxin-mediated control of cytosolic pH by Vicia mesophyll and guard cells
A role for the vacuole in auxin-mediated control of cytosolic pH by Vicia mesophyll and guard cells
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DOI：
10.1046/j.1365-313x.1998.00013.x
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发表时间：
1998-01-01
期刊：
影响因子：
7.2
通讯作者：
Blatt, MR
中科院分区：
文献类型：
--
作者：
Frohnmeyer, H;Grabov, A;Blatt, MR
长期以来，人们一直在讨论细胞质 pH (pH(i)) 在植物激素信号传导和运输控制中的作用。然而，虽然 pH(i) 的变化是植物细胞中激素刺激的常见结果，并有助于激素诱发的离子通道控制，但这些变化的起源仍然未知。为了检查液泡膜和液泡区室在这些事件中的可能作用，在存在生长素的情况下，在用弱酸加载胞质 H+ 的过程中，测量了来自蚕豆叶肉和保卫细胞的液泡和空泡原生质体的 pH(i)。在 Percoll 梯度上超速离心后获得了空泡原生质体，并记录了两种原生质体的 pH(i)。空泡和疏散！使用荧光比显微光度法和 pH 敏感染料 BCECF 制备制剂。外部pH测量表明，与空泡原生质体相比，空泡原生质体中的净H+分泌率大约增加两倍，并且表明空泡原生质体在生长素存在下保留了H+分泌的特征性刺激。 BCECF 荧光记录给出的静息 pH(i) 值接近 7.5，排空对此参数没有显着影响。 10μM浓度的生长素1-萘乙酸和3-吲哚酰乙酸，而不是非活性（抗生长素）类似物2-萘乙酸，在液泡原生质体中引起0.1-0.2单位的pH（i）可逆降低。然而，在 12 项疏散原生质体实验中，除其中一项外，生长素处理均未能引起 pH(i) 的变化。面对通过向浴中添加 Na+-丁酸盐所施加的酸性 pH(i) 负载，排空似乎还降低了原生质体的瞬时、动态 H+ 缓冲能力。这些结果暗示液泡膜或液泡区室参与短期 pH(i) 稳态以及植物细胞中激素诱发的 H+ 信号传导的产生；它们也符合这样的观点：pH(i) 本身的降低并不是生长素刺激 H+ 分泌的主要决定因素。
A role for cytosolic pH (pH(i)) in hormonal signalling and transport control in plants has long been mooted. Yet, while changes in pH(i) are a common consequence of hormonal stimuli in plant cells and contribute to hormonally evoked ion channel control, the origins of these changes remain unknown. To examine a possible role for the tonoplast and vacuolar compartment in these events, pH(i) was measured in the presence of auxins and during cytosolic H+ loading with weak acid in vacuolate and evacuolate protoplasts, both from mesophyll and guard cells of Vicia faba L. Evacuolate protoplasts were obtained following ultracentrifugation on Percoll gradients, and pH(i) of single protoplasts was recorded in both vacuolate and evacuolate! preparations using fluorescence ratio microphotometry and the pH-sensitive dye BCECF. External pH measurements indicated a roughly twofold increase in the rate of net H+ secretion in evacuolate compared with vacuolate protoplasts, and showed that evacuolate protoplasts retained the characteristic stimulation of H+ secretion in the presence of auxin. BCECF fluorescence recording gave resting pH(i) values near 7.5, and evacuolation had no significant effect on this parameter. Reversible decreases of 0.1-0.2 units in pH(i) were evoked in vacuolate protoplasts by 10 mu M concentrations of the auxins 1-naphthalene acetic acid and 3-indoyl-acetic acid, and not by the inactive (anti-auxin) analogue 2-naphthalene-acetic acid. However, auxin treatments failed to evoke a change in pH(i) in all but one of 12 experiments with evacuolate protoplasts. Evacuolation also appeared to reduce the transient, dynamic H+ buffering capacity of the protoplasts in the face of acid pH(i) loads imposed by adding Na+-butyrate to the bath. These results implicate the tonoplast or vacuolar compartment in short-term pH(i) homeostasis and generation of hormonally evoked H+ signalling in plant cells; they also conform with the view that the decrease in pH(i) per se is not a primary determinant in the stimulation of H+ secretion by auxin.