Regulation of intracellular pH during anoxia in rice coleoptiles in acidic and near neutral conditions.
Regulation of intracellular pH during anoxia in rice coleoptiles in acidic and near neutral conditions.
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DOI：
10.1093/jxb/erp090
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发表时间：
2009
影响因子：
6.9
通讯作者：
Colmer TD
中科院分区：
文献类型：
--
作者：
Kulichikhin KY;Greenway H;Byrne L;Colmer TD
水稻胚芽鞘以耐缺氧而闻名，经过低氧预处理、切除、“治愈”，然后暴露于缺氧和 pH 3.5 的组合中。假定的酸负荷通过 K+ 向培养基的净流出来证实，同时培养基中 H+ 的净减少，大概主要是由于 H+ 的流入。然而，胚芽鞘在缺氧和 pH 3.5 的组合下存活了至少 90 小时，甚至在缺氧固有的能量危机因向胚芽鞘提供 2.5 mM 而不是 50 mM 葡萄糖而加剧时存活了至少 40 小时。即使在含有 2.5 mM 葡萄糖的胚芽鞘中，在重新通气开始后 4 小时，Cl- 的累积比率也达到了 6，这意味着质膜完整性要么在缺氧期间得以维持，要么在返回通气条件后迅速恢复。使用体内 31P 核磁共振波谱法在基础灌注介质中使用 50 mM 葡萄糖测量细胞质 pH 值和液泡 pH 值。缺氧60小时后，外部pH突然从6.5降至3.5，但细胞质pH仅在前2小时内从7.35降至7.2，然后在接下来的16小时内保持稳定。在 pH 为 3.5 的前 3 小时内，液泡 pH 从 5.7 降至 5.25，然后稳定。在 pH 3.5 下 18 小时后，细胞质 pH 和液泡 pH 的初始值迅速恢复，在维持缺氧的同时返回到 pH 6.5 后，以及随后返回充气溶液后。总之，暴露于缺氧和 pH 3.5 的组合下的水稻胚芽鞘保留了 pH 调节和细胞区室，即使在暴露于 pH 3.5 所施加的酸负荷期间，也表现出对缺氧的耐受性。
Rice coleoptiles, renowned for anoxia tolerance, were hypoxically pretreated, excised, ‘healed’, and then exposed to a combination of anoxia and pH 3.5. The putative acid load was confirmed by net effluxes of K+ to the medium, with concurrent net decreases of H+ in the medium, presumably mainly due to H+ influx. Yet the coleoptiles survived the combination of anoxia and pH 3.5 for at least 90 h, and even for at least 40 h when the energy crisis, inherent to anoxia, had been aggravated by supplying the coleoptiles with 2.5 mM rather than 50 mM glucose. Even in the case of coleoptiles with 2.5 mM glucose, an accumulation ratio of 6 for Cl– was attained at 4 h after the start of re-aeration, implying plasma membrane integrity was either maintained during anoxia, or rapidly restored after a return to aerated conditions. Cytoplasmic pH and vacuolar pH were measured using in vivo 31P nuclear magnetic resonance spectroscopy with 50 mM glucose in the basal perfusion medium. After 60 h in anoxia, external pH was suddenly decreased from 6.5 to 3.5, but cytoplasmic pH only decreased from 7.35 to 7.2 during the first 2 h and then remained steady for the next 16 h. During the first 3 h at pH 3.5, vacuolar pH decreased from 5.7 to 5.25 and then stabilized. After 18 h at pH 3.5, the initial values of cytoplasmic pH and vacuolar pH were rapidly restored, both upon a return to pH 6.5 while maintaining anoxia and after subsequent return to aerated solution. Summing up, rice coleoptiles exposed to a combination of anoxia and pH 3.5 retained pH regulation and cellular compartmentation, demonstrating tolerance to anoxia even during the acid load imposed by exposure to pH 3.5.
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