The fou2 mutation in the major vacuolar cation channel TPC1 confers tolerance to inhibitory luminal calcium
The fou2 mutation in the major vacuolar cation channel TPC1 confers tolerance to inhibitory luminal calcium
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DOI：
10.1111/j.1365-313x.2009.03820.x
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发表时间：
2009-06-01
期刊：
影响因子：
7.2
通讯作者：
Hedrich, Rainer
中科院分区：
文献类型：
--
作者：
Beyhl, Diana;Hoertensteiner, Stefan;Hedrich, Rainer
TPC1基因编码的SV通道代表一种依赖于钙离子和电压的空泡阳离子通道。TPC1内的D454N点突变，命名为Fou2，即脂肪酸氧化上调2，导致应激激素茉莉酸的合成增加。由于创伤产生了钙信号，而细胞内的钙离子是SV通道功能所必需的，因此我们研究了这一主要的液泡阳离子通道与拟南芥叶肉液泡的钙依赖特性。在膜片钳测量中，野生型和Fou2 SV通道在胞浆钙敏感性和钙离子不通透性方面没有差异。当液泡Ca~(2+)浓度达到0.1-mM时，通过野生型TPC1的K+流通量减少甚至完全消失。然而，在这些条件下，污浊的蛋白质仍然活跃。因此，D454N似乎是钙离子识别位点的一部分。因此，SV通道突变体获得了对升高的管腔钙离子的耐受性。突变体Fou2的液泡Ca/K比是野生型植物的三倍，这似乎表明在SV通道活动消失和K+动态平衡被破坏之前，Fou2可以积累更高水平的液泡钙。因此，作为对伤害的响应，植物可能会产生强烈的液泡来源的胞质钙信号，从而导致茉莉酸的过量产生。
The SV channel encoded by the TPC1 gene represents a Ca2+- and voltage-dependent vacuolar cation channel. Point mutation D454N within TPC1, named fou2 for fatty acid oxygenation upregulated 2, results in increased synthesis of the stress hormone jasmonate. As wounding causes Ca2+ signals and cytosolic Ca2+ is required for SV channel function, we here studied the Ca2+-dependent properties of this major vacuolar cation channel with Arabidopsis thaliana mesophyll vacuoles. In patch clamp measurements, wild-type and fou2 SV channels did not exhibit differences in cytosolic Ca2+ sensitivity and Ca2+, impermeability. K+ fluxes through wild-type TPC1 were reduced or even completely faded away when vacuolar Ca2+ reached the 0.1-mm level. The foul protein under these conditions, however, remained active. Thus, D454N seems to be part of a luminal Ca2+ recognition site. Thereby the SV channel mutant gains tolerance towards elevated luminal Ca2+. A three-fold higher vacuolar Ca/K ratio in the fou2 mutant relative to wild-type plants seems to indicate that fou2 can accumulate higher levels of vacuolar Ca2+ before SV channel activity vanishes and K+ homeostasis is impaired. In response to wounding fou2 plants might thus elicit strong vacuole-derived cytosolic Ca2+ signals resulting in overproduction of jasmonate.