Shen Hong, He Long Fei, Sasaki Takayuki, Yamamoto Yoko, Zheng Shao Jian, Ligaba Ayalew, Yan Xiao Long, Ahn Sung Ju, Yamaguchi Mineo, Sasakawa Hideo, Matsumoto Hideaki
Lab of Plant Nutritional Genetics and Root Biology Center, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, People's Republic of China.
Plant Physiol. 2005 May;138(1):287-96. doi: 10.1104/pp.104.058065. Epub 2005 Apr 15.
The aluminum (Al)-induced secretion of citrate has been regarded as an important mechanism for Al resistance in soybean (Glycine max). However, the mechanism of how Al induces citrate secretion remains unclear. In this study, we investigated the regulatory role of plasma membrane H+-ATPase on the Al-induced secretion of citrate from soybean roots. Experiments performed with plants grown in full nutrient solution showed that Al-induced activity of plasma membrane H+-ATPase paralleled secretion of citrate. Vanadate and fusicoccin, an inhibitor and an activator, respectively, of plasma membrane H+-ATPase, exerted inhibitory and stimulatory effects on the Al-induced secretion of citrate. Higher activity of plasma membrane H+-ATPase coincided with more citrate secretion in Al-resistant than Al-sensitive soybean cultivars. These results suggested that the effects of Al stress on citrate secretion were mediated via modulation of the activity of plasma membrane H+-ATPase. The relationship between the Al-induced secretion of citrate and the activity of plasma membrane H+-ATPase was further demonstrated by analysis of plasma membrane H+-ATPase transgenic Arabidopsis (Arabidopsis thaliana). When plants were grown on Murashige and Skoog medium containing 30 microM Al (9.1 microM Al3+ activity), transgenic plants exuded more citrate compared with wild-type Arabidopsis. Results from real-time reverse transcription-PCR and immunodetection analysis indicated that the increase of plasma membrane H+-ATPase activity by Al is caused by transcriptional and translational regulation. Furthermore, plasma membrane H+-ATPase activity and expression were higher in an Al-resistant cultivar than in an Al-sensitive cultivar. Al activated the threonine-oriented phosphorylation of plasma membrane H+-ATPase in a dose- and time-dependent manner. Taken together, our results demonstrated that up-regulation of plasma membrane H+-ATPase activity was associated with the secretion of citrate from soybean roots.
铝（Al）诱导的柠檬酸分泌被认为是大豆（Glycine max）耐铝性的重要机制。然而，铝如何诱导柠檬酸分泌的机制仍不清楚。在本研究中，我们研究了质膜H⁺-ATP酶对铝诱导的大豆根中柠檬酸分泌的调节作用。在完全营养液中生长的植物所进行的实验表明，铝诱导的质膜H⁺-ATP酶活性与柠檬酸分泌平行。钒酸盐和藤霉素分别作为质膜H⁺-ATP酶的抑制剂和激活剂，对铝诱导的柠檬酸分泌产生抑制和刺激作用。在耐铝大豆品种中，质膜H⁺-ATP酶活性较高与更多的柠檬酸分泌相一致，而在铝敏感品种中则不然。这些结果表明，铝胁迫对柠檬酸分泌的影响是通过调节质膜H⁺-ATP酶的活性介导的。通过对质膜H⁺-ATP酶转基因拟南芥（Arabidopsis thaliana）的分析，进一步证明了铝诱导的柠檬酸分泌与质膜H⁺-ATP酶活性之间的关系。当植物在含有30微摩尔铝（9.1微摩尔Al³⁺活性）的Murashige和Skoog培养基上生长时，转基因植物比野生型拟南芥分泌更多的柠檬酸。实时逆转录PCR和免疫检测分析结果表明，铝引起的质膜H⁺-ATP酶活性增加是由转录和翻译调控引起的。此外，耐铝品种中的质膜H⁺-ATP酶活性和表达高于铝敏感品种。铝以剂量和时间依赖性方式激活质膜H⁺-ATP酶的苏氨酸定向磷酸化。综上所述，我们的结果表明质膜H⁺-ATP酶活性的上调与大豆根中柠檬酸的分泌有关。
