AtNHX3 is a vacuolar K+/H+ antiporter required for low-potassium tolerance in Arabidopsis thaliana
AtNHX3 is a vacuolar K+/H+ antiporter required for low-potassium tolerance in Arabidopsis thaliana
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DOI：
10.1111/j.1365-3040.2010.02200.x
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发表时间：
2010-11-01
影响因子：
7.3
通讯作者：
Zhang, Hongxia
中科院分区：
文献类型：
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作者：
Liu, Hua;Tang, Renjie;Zhang, Hongxia
拟南芥中有三种液泡膜阳离子/H+反向转运蛋白AtNHX 1（At 5g 27150）、AtNHX 2（At 3g 05030）和AtNHX 5（At 1g 54370）。然而，AtNHX 3（At 5g 55470）的生理功能仍不清楚。本研究以T-DNA插入突变体和35 S驱动的AtNHX 3过表达拟南芥为材料，研究AtNHX 3的生理功能。RT-PCR分析表明AtNHX 3在萌发的种子、花和角果中高度表达。AtNHX 3：：YFP融合蛋白在烟草原生质体中的实验表明，AtNHX 3主要定位于液泡膜，少量定位于前液泡区室（PVC）和内质网（ER）。nhx 3缺失突变体的幼苗对K+缺乏条件非常敏感。AtNHX 3的表达补充了nhx 3幼苗对K+缺乏的敏感性。从过表达AtNHX 3的转基因植物中分离的液泡膜囊泡显示出比从野生型植物中分离的液泡膜囊泡显著更高的K+/H+交换速率。此外，nhx 3种子积累较少的K+和更多的Na+时，野生型和nhx 3生长在正常的生长条件下。结果表明，AtNHX 3基因编码一种K+/H+逆向转运蛋白，该蛋白在拟南芥萌发和幼苗早期发育过程中对低钾具有耐受性，并可能在拟南芥K+利用和离子稳态中发挥作用。
Three vacuolar cation/H+ antiporters, AtNHX1 (At5g27150), 2 (At3g05030) and 5 (At1g54370), have been characterized as functional Na+/H+ antiporters in Arabidopsis. However, the physiological functions of AtNHX3 (At5g55470) still remain unclear. In this study, the physiological functions of AtNHX3 were studied using T-DNA insertion mutant and 35S-driven AtNHX3 over-expression Arabidopsis plants. RT-PCR analyses revealed that AtNHX3 is highly expressed in germinating seeds, flowers and siliques. Experiments with AtNHX3::YFP fusion protein in tobacco protoplasts indicated that AtNHX3 is mainly localized to vacuolar membrane, with a minor localization to pre-vacuolar compartments (PVCs) and endoplasmic reticulum (ER). Seedlings of null nhx3 mutants were hypersensitive to K+-deficient conditions. Expression of AtNHX3 complemented the sensitivity to K+ deficiency in nhx3 seedlings. Tonoplast vesicles isolated from transgenic plants over-expressing AtNHX3 displayed significantly higher K+/H+ exchange rates than those isolated from wild-type plants. Furthermore, nhx3 seeds accumulated less K+ and more Na+ when both wild-type and nhx3 were grown under normal growth condition. The overall results indicate that AtNHX3 encodes a K+/H+ antiporter required for low-potassium tolerance during germination and early seedling development, and may function in K+ utilization and ion homeostasis in Arabidopsis.