STUDIES ON THE ROLE OF VACUOLES IN ION METABOLISMS IN PLANT.

在植物细胞的无机离子代谢中，液泡是最重要的细胞器之一。液泡通常是细胞质离子动态平衡的离子储存库和缓冲器。在这些功能中，液泡膜离子转运系统发挥着重要作用。本研究试图从生理学和分子生物学的角度全面分析液泡在植物细胞有机离子代谢中的作用。Dietz博士和Mimura博士从日本红树林植物悬浮培养细胞和不同营养条件下培养的大麦植株中分离出液泡膜。我们用特异性抑制剂巴菲罗星测定了液泡膜的ATPase和H~+泵活性。我们发现腺嘌呤核苷酸和无机磷酸是液泡膜H^+-ATPase的调节因子。我们发现，光诱导的液泡酸化最初的波动可以用液泡膜H~+-ATPase活性比例的变化和细胞质内腺核苷酸水平的变化来解释。此外，我们注意到氧化还原条件也可能是环境中的控制因素之一。在澳大利亚，Smith博士和I(Dr.Mimura)使用分离的Charanode细胞测量了PI跨质膜运输和液泡Pilevel之间的关系。通过在含有不同浓度PI的培养液中培养节间细胞，我们首次成功地独立地控制了细胞的转运和液泡液中的PI水平。质膜的PI吸收活性不受细胞质和液泡型PI池的影响。我们现在正试图测量细胞内跨液泡膜的PI转运活动。

In inorganic ion metabolisms in plant cells, vacuole is one of the most important organelles. The vacuole is usually working as ion reservoir and buffer for the cytoplasmic ion homeostasis. For these functions, the tonoplast ion transport systems are playing important roles . In the present project, we tried to totally analyze the role of the vacuole in organic ion metabolisms in plant cells by means of physiology to molecular biology.Dr.Dietz and I (Dr.Mimura) isolated the tonoplast from barley plants which were cultured under different nutrient conditions and suspension cultured cells of mangrove plant in Japan. We have measured the ATPase and H^+-pumping activities of the tonoplast using the specific in hibitor ; Bafilomycin. We have found that the adenine nucleotides and the norganic phosphate are working as regulators of the tonoplast H^+-ATPase. We showed that the initial fluctuation of the light-induced vacuolar acidification could be explained by the changes in the tonoplast H^+ -ATPase activity proportion al to the changes in the cytoplasmic adeninenucleotide levels. Furth ermore, we noticed that the redox conditions might be also working as one of controlling factors in situ.In Australia, Dr.Smith and I (Dr.Mimura) measured the relation ship between Pi transport across the plasma membrane and the vacuolar Pilevel usint isolated Charainternodal cells. By incubating internodal cells in media Gaving different concentrations of Pi, we first succeeded to control the Pitransport and the vacuolar Pi levelindependently. The Pi uptake activity of the plasma membrane changed independent of both the cytoplasmic and the vacuolar Pi pools. We are now trying to measure the Pi transport activity across the tonoplast in the cell.