A plant Ca2+ pump, ACA2, relieves salt hypersensitivity in yeast -: Modulation of cytosolic calcium signature and activation of adaptive Na+ homeostasis
A plant Ca2+ pump, ACA2, relieves salt hypersensitivity in yeast -: Modulation of cytosolic calcium signature and activation of adaptive Na+ homeostasis
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DOI：
10.1074/jbc.m700766200
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发表时间：
2008-02-08
影响因子：
4.8
通讯作者：
Mathew, M. K.
中科院分区：
文献类型：
--
作者：
Anil, Veena S.;Rajkumar, Premraj;Mathew, M. K.
植物和酵母中的胁迫反应都利用钙介导的信号转导。酵母菌株K616没有钙泵，需要微摩尔的钙(2+)才能生长。K616能耐受渗透胁迫(750 mM山梨醇)和离子胁迫(300 MM KCl)，但不能耐高钠胁迫(300 MM NaC L)。内质网定位的拟南芥钙-ATPase ACA2的异源表达允许K616在盐胁迫下生长，即使在钙缺乏的介质中也是如此。所有的胁迫在野生型酵母K601中都产生了短暂的胞浆钙离子升高，而单独的氯化钠则导致了K616中胞浆钙离子的长期升高。ACA2转化子和K601在盐胁迫下的钙瞬变和存活率相似。然而，虽然K601主要通过泵出质膜来维持低细胞内Na+，但转化子将Na+隔离在内部细胞器中。这种隔离需要膜内Na+/H+-逆向转运蛋白NHX1的存在，除了在酸性pH条件下，NHX1在野生型酵母的耐盐性中不起重要作用。质膜Na+-ATPase ENA1只在K601中被强烈诱导，而NHX1在K601和ACA2转化子中都被强烈诱导。钙调蛋白激酶抑制剂KN62显著降低了ACA2转化子的耐盐性和NHX1的转录诱导。因此，植物膜内钙泵的异源表达导致细胞内钙离子的迅速耗尽，并激活了另一种生存盐分胁迫的机制。
Stress responses in both plants and yeast utilize calcium-mediated signaling. A yeast strain, K616, which lacks Ca2+ pumps, requires micromolar Ca(2+)for growth. In medium containing 100 mu M Ca2+, K616 can withstand osmotic stress (750 mM sorbitol) and ionic stress (300 mM KCl) but not hypersodic stress (300 mM NaCl). Heterologous expression of the endoplasmic reticulum-located Arabidopsis thaliana Ca2+-ATPase, ACA2, permits K616 to grow under NaCl stress even in Ca2+-depleted medium. All stresses tested generated transient elevation of cytosolic Ca2+ in wild type yeast, K601, whereas NaCl alone induced prolonged elevation of cytosolic Ca2+ in K616. Both the Ca2+ transient and survival of cultures subjected to NaCl stress was similar for the ACA2 transformant and K601. However, whereas K601 maintained low cytosolic Na+ predominantly by pumping it out across the plasma membrane, the transformant sequestered Na+ in internal organelles. This sequestration requires the presence of an endomembrane Na+/H+-antiporter, NHX1, which does not play a significant role in salt tolerance of wild type yeast except at acidic pH. Transcript levels of the plasma membrane Na+-ATPase, ENA1, were strongly induced only in K601, whereas NHX1 was strongly induced in both K601 and the ACA2 transformant. The calmodulin kinase inhibitor KN62 significantly reduced the salt tolerance of the ACA2 transformant and the transcriptional induction of NHX1. Thus, the heterologous expression of a plant endomembrane Ca2+ pump results in the rapid depletion of cytosolic Ca2+ and the activation of an alternate mechanism for surviving saline stress.