van der Veen R, Heimovaara-Dijkstra S, Wang M
Center for Phytotechnology Leiden University/Netherlands Organisation for Applied Scientific Research, Wassenaarseweg 64, 2333 AL Leiden, the Netherlands.
Plant Physiol. 1992 Oct;100(2):699-705. doi: 10.1104/pp.100.2.699.
We investigated whether intracellular pH (pH(i)) is a causal mediator in abscisic acid (ABA)-induced gene expression. We measured the change in pH(i) by a "null-point" method during stimulation of barley (Hordeum vulgare cv Himalaya) aleurone protoplasts with ABA and found that ABA induces an increase in pH(i) from 7.11 to 7.30 within 45 min after stimulation. This increase is inhibited by plasma membrane H(+)-ATPase inhibitors, which induce a decrease in pH(i), both in the presence and absence of ABA. This ABA-induced pH(i) increase precedes the expression of RAB-16 mRNA, as measured by northern analysis. ABA-induced pH(i) changes can be bypassed or clamped by addition of either the weak acids 5,5-dimethyl-2,4-oxazolidinedione and propionic acid, which decrease the pH(i), or the weak bases methylamine and ammonia, which increase the pH(i). Artificial pH(i) increases or decreases induced by weak bases or weak acids, respectively, do not induce RAB-16 mRNA expression. Clamping of the pH(i) at a high value with methylamine or ammonia treatment affected the ABA-induced increase of RAB-16 mRNA only slightly. However, inhibition of the ABA-induced pH(i) increase with weak acid or proton pump inhibitor treatments strongly inhibited the ABA-induced RAB-16 mRNA expression. We conclude that, although the ABA-induced the pH(i) increase is correlated with and even precedes the induction of RAB-16 mRNA expression and is an essential component of the transduction pathway leading from the hormone to gene expression, it is not sufficient to cause such expression.
我们研究了细胞内pH值（pH(i)）是否是脱落酸（ABA）诱导基因表达的因果介导因子。在用ABA刺激大麦（Hordeum vulgare cv Himalaya）糊粉层原生质体的过程中，我们通过“零点”法测量了pH(i)的变化，发现ABA在刺激后45分钟内可使pH(i)从7.11升高至7.30。质膜H(+) - ATP酶抑制剂可抑制这种升高，无论有无ABA存在，该抑制剂都会使pH(i)降低。如通过Northern分析所测，这种ABA诱导的pH(i)升高先于RAB - 16 mRNA的表达。添加弱酸5,5 - 二甲基 - 2,4 - 恶唑烷二酮和丙酸（可降低pH(i)）或弱碱甲胺和氨（可升高pH(i)），可绕过或钳制ABA诱导的pH(i)变化。分别由弱碱或弱酸诱导的人工pH(i)升高或降低，均不会诱导RAB - 16 mRNA表达。用甲胺或氨处理将pH(i)钳制在较高值时，对ABA诱导的RAB - 16 mRNA增加仅有轻微影响。然而，用弱酸或质子泵抑制剂处理抑制ABA诱导的pH(i)升高，会强烈抑制ABA诱导的RAB - 16 mRNA表达。我们得出结论，尽管ABA诱导的pH(i)升高与RAB - 16 mRNA表达的诱导相关甚至先于该诱导，并且是从激素到基因表达的转导途径的重要组成部分，但它并不足以导致这种表达。
