Hallouin Matthieu, Ghelis Thanos, Brault Mathias, Bardat Françoise, Cornel Daniel, Miginiac Emile, Rona Jean-Pierre, Sotta Bruno, Jeannette Emmanuelle
Physiologie Cellulaire et Moléculaire des Plantes, Unité Mixte de Recherche Centre National de la Recherche Scientifique 7632, case 156, Université Pierre et Marie Curie (Paris VI), 4 place Jussieu, 75252 Paris cedex 05, France.
Plant Physiol. 2002 Sep;130(1):265-72. doi: 10.1104/pp.004168.
Abscisic acid (ABA) plays a key role in the control of stomatal aperture by regulating ion channel activities and water exchanges across the plasma membrane of guard cells. Changes in cytoplasmic calcium content and activation of anion and outward-rectifying K(+) channels are among the earliest cellular responses to ABA in guard cells. In Arabidopsis suspension cells, we have demonstrated that outer plasmalemma perception of ABA triggered similar early events. Furthermore, a Ca(2+) influx and the activation of anion channels are part of the ABA-signaling pathway leading to the specific expression of RAB18. Here, we determine whether phospholipases are involved in ABA-induced RAB18 expression. Phospholipase C is not implicated in this ABA pathway. Using a transphosphatidylation reaction, we show that ABA plasmalemma perception results in a transient stimulation of phospholipase D (PLD) activity, which is necessary for RAB18 expression. Further experiments showed that PLD activation was unlikely to be regulated by heterotrimeric G proteins. We also observed that ABA-dependent stimulation of PLD was necessary for the activation of plasma anion current. However, when ABA activation of plasma anion channels was inhibited, the ABA-dependent activation of PLD was unchanged. Thus, we conclude that in Arabidopsis suspension cells, ABA stimulation of PLD acts upstream from anion channels in the transduction pathway leading to RAB18 expression.
脱落酸（ABA）通过调节离子通道活性和保卫细胞质膜上的水分交换，在气孔孔径控制中起关键作用。细胞质钙含量的变化以及阴离子和外向整流钾通道的激活是保卫细胞对ABA最早的细胞反应之一。在拟南芥悬浮细胞中，我们已经证明质膜外侧对ABA的感知会引发类似的早期事件。此外，钙内流和阴离子通道的激活是导致RAB18特异性表达的ABA信号通路的一部分。在此，我们确定磷脂酶是否参与ABA诱导的RAB18表达。磷脂酶C不参与此ABA途径。通过转磷脂酰化反应，我们表明质膜对ABA的感知会导致磷脂酶D（PLD）活性的短暂刺激，这是RAB18表达所必需的。进一步的实验表明，PLD的激活不太可能受异源三聚体G蛋白调节。我们还观察到，ABA对PLD的刺激是质膜阴离子电流激活所必需的。然而，当ABA对质膜阴离子通道的激活受到抑制时，ABA对PLD的依赖性激活没有变化。因此，我们得出结论，在拟南芥悬浮细胞中，ABA对PLD的刺激在导致RAB18表达的转导途径中作用于阴离子通道的上游。
