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

在植物细胞无机离子代谢中，液泡是最重要的细胞器之一。液泡通常作为细胞质离子稳态的离子库和缓冲器。对于这些功能，液泡膜离子转运系统起着重要的作用。本研究从生理学到分子生物学的角度，从不同营养条件下培养的大麦植株和日本红树林植物悬浮培养细胞中分离出液泡膜，试图全面分析液泡膜在植物细胞有机离子代谢中的作用。我们用特异性抑制剂巴弗洛霉素测定了液泡膜的ATP酶和H^+泵活性。我们发现腺嘌呤核苷酸和无机磷酸盐是液泡膜H^+-ATP酶的调节剂。我们发现，光诱导的液泡酸化的初始波动可以用液泡膜H^+ -ATPase活性的变化与胞质腺苷酸水平的变化成比例来解释。在澳大利亚，Smith博士和我（Mimura博士）用分离的Charainternodal细胞测量了Pi跨质膜运输和液泡Pilevel之间的关系。通过在培养液中加入不同浓度的磷，我们首次成功地控制了节间运输和液泡中的磷水平。质膜的磷吸收活性的变化独立的细胞质和液泡磷池。我们现在正试图测量Pi在细胞液泡膜中的运输活性。

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.