Arabidopsis V-ATPase activity at the tonoplast is required for efficient nutrient storage but not for sodium accumulation
Arabidopsis V-ATPase activity at the tonoplast is required for efficient nutrient storage but not for sodium accumulation
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DOI：
10.1073/pnas.0913035107
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发表时间：
2010-02-16
影响因子：
11.1
通讯作者：
Schumacher, Karin
中科院分区：
文献类型：
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作者：
Krebs, Melanie;Beyhl, Diana;Schumacher, Karin
高等植物作为食物和能量的主要来源，其生产力与它们缓冲必需离子和有毒离子浓度变化的能力有关。液泡H+- atp酶（V-ATPase）和液泡H+-焦磷酸酶（V-PPase）这两个质子泵为细胞膜的转运提供能量；然而，它们的功能关系和对离子储存和解毒的相对贡献尚不清楚。我们已经确定了一个拟南芥突变体，其中液泡运输的激活完全依赖于V-PPase的活性。vha-a2 vha-a3双突变体缺乏膜整合v - atp酶亚基VHA-a的两个张力质体定位异构体，是有活力的，但表现出依赖于白昼长度的生长迟缓。突变体vha-a2的硝酸盐含量降低，而硝酸盐同化增加，表明液泡硝酸盐储存是主要的生长限制因素。锌是一种必需的微量营养素，浓度过高时有毒，并通过液泡Zn2+/H+-反port系统解毒。因此，双突变体对锌的耐受性降低。以同样的方式，液泡Na+/H+-反端口系统被认为是从细胞质溶胶中去除钠的系统的重要组成部分。出乎意料的是，vha-a2 vha-a3双突变体的耐盐性和积累并未受到影响。相反，反式高尔基网络/早期核内体（TGN/EE）中v - atp酶活性的降低导致盐敏感性增加。综上所述，我们的研究结果表明，在配子体和胚胎发育过程中，张力体上的V-PPase活性是充足的，而在营养和生殖生长过程中，张力体上的V-ATPase活性限制了营养物质的储存，而不是钠耐受性。
The productivity of higher plants as a major source of food and energy is linked to their ability to buffer changes in the concentrations of essential and toxic ions. Transport across the tonoplast is energized by two proton pumps, the vacuolar H+-ATPase (V-ATPase) and the vacuolar H+-pyrophosphatase (V-PPase); however, their functional relation and relative contributions to ion storage and detoxification are unclear. We have identified an Arabidopsis mutant in which energization of vacuolar transport solely relies on the activity of the V-PPase. The vha-a2 vha-a3 double mutant, which lacks the two tonoplast-localized isoforms of the membrane-integral V-ATPase subunit VHA-a, is viable but shows day-length-dependent growth retardation. Nitrate content is reduced whereas nitrate assimilation is increased in the vha-a2 vha-a3 mutant, indicating that vacuolar nitrate storage represents a major growth-limiting factor. Zinc is an essential micronutrient that is toxic at excess concentrations and is detoxified via a vacuolar Zn2+/H+-antiport system. Accordingly, the double mutant shows reduced zinc tolerance. In the same way the vacuolar Na+/H+-antiport system is assumed to be an important component of the system that removes sodium from the cytosol. Unexpectedly, salt tolerance and accumulation are not affected in the vha-a2 vha-a3 double mutant. In contrast, reduction of V-ATPase activity in the trans-Golgi network/early endosome (TGN/EE) leads to increased salt sensitivity. Taken together, our results show that during gametophyte and embryo development V-PPase activity at the tonoplast is sufficient whereas tonoplast V-ATPase activity is limiting for nutrient storage but not for sodium tolerance during vegetative and reproductive growth.