University Wuerzburg, Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs Platz 2, D-97082 Wuerzburg, Germany.
Proc Natl Acad Sci U S A. 2009 Dec 15;106(50):21425-30. doi: 10.1073/pnas.0912021106. Epub 2009 Dec 2.
In response to drought stress the phytohormone ABA (abscisic acid) induces stomatal closure and, therein, activates guard cell anion channels in a calcium-dependent as well as-independent manner. Two key components of the ABA signaling pathway are the protein kinase OST1 (open stomata 1) and the protein phosphatase ABI1 (ABA insensitive 1). The recently identified guard cell anion channel SLAC1 appeared to be the key ion channel in this signaling pathway but remained electrically silent when expressed heterologously. Using split YFP assays, we identified OST1 as an interaction partner of SLAC1 and ABI1. Upon coexpression of SLAC1 with OST1 in Xenopus oocytes, SLAC1-related anion currents appeared similar to those observed in guard cells. Integration of ABI1 into the SLAC1/OST1 complex, however, prevented SLAC1 activation. Our studies demonstrate that SLAC1 represents the slow, deactivating, weak voltage-dependent anion channel of guard cells controlled by phosphorylation/dephosphorylation.
在应对干旱胁迫时，植物激素 ABA（脱落酸）会诱导气孔关闭，并以钙依赖和非依赖的方式激活保卫细胞质膜阴离子通道。ABA 信号通路的两个关键组成部分是蛋白激酶 OST1（开放气孔 1）和蛋白磷酸酶 ABI1（ABA 不敏感 1）。最近发现的保卫细胞质膜阴离子通道 SLAC1 似乎是该信号通路中的关键离子通道，但在异源表达时仍保持电沉默。通过分裂 YFP 测定，我们鉴定出 OST1 是 SLAC1 和 ABI1 的相互作用伙伴。在爪蟾卵母细胞中共表达 SLAC1 和 OST1 后，SLAC1 相关的阴离子电流类似于在保卫细胞中观察到的电流。然而，将 ABI1 整合到 SLAC1/OST1 复合物中会阻止 SLAC1 的激活。我们的研究表明，SLAC1 代表由磷酸化/去磷酸化控制的、具有慢失活特性的、电压依赖性的、弱的保卫细胞质膜阴离子通道。
