Regulation of H+ extrusion and cytoplasmic pH in maize root tips acclimated to a low-oxygen environment

被引:46
作者
Xia, JH [1 ]
Roberts, JKM [1 ]
机构
[1] UNIV CALIF RIVERSIDE, DEPT BIOCHEM, RIVERSIDE, CA 92521 USA
关键词
D O I
10.1104/pp.111.1.227
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
We tested the hypothesis that H+ extrusion contributes to cytoplasmic pH regulation and tolerance of anoxia in maize (Zea mays) root tips. We studied root tips of whole seedlings that were acclimated to a low-oxygen environment by pretreatment in 3% (v/v) O-2. Acclimated root tips characteristically regulate cytoplasmic pH near neutrality and survive prolonged anoxia, whereas nonacclimated tips undergo severe cytoplasmic acidosis and die much more quickly. We show that the plasma membrane H+-ATPase can operate under anoxia and that net H+ extrusion increases when cytoplasmic pH falls. However, at an external pH near 6.0, H+ extrusion contributes little to cytoplasmic pH regulation. At more acidic external pH values, net H+ flux into root tips increases dramatically, leading to a decrease in cytoplasmic pH and reduced tolerance of anoxia. We present evidence that, under these conditions, H+ pumps are activated to partly offset acidosis due to H+ influx and, thereby, contribute to cytoplasmic pH regulation and tolerance of anoxia. The regulation of H+ extrusion under anoxia is discussed with respect to the acclimation response and mechanisms of intracellular pH regulation in aerobic plant cells.
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收藏
页码:227 / 233
页数:7
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