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。液泡通常作为离子储存库和细胞质离子平衡的缓冲剂。在这些功能中，质体离子转运系统起着重要的作用。本课题试图从生理学到分子生物学的角度全面分析液泡在植物细胞无机离子代谢中的作用。去年，我们测量了分离的大麦叶肉液泡的Pi吸收量。遗憾的是，大麦液泡对π的吸收活性并不高。因此，我们尝试测定玫瑰花悬浮培养细胞的Pi摄取活性。已知这些细胞在质膜和张力质体中具有高的Pi摄取活性。与大麦一样，花楸液泡也表现出ATP和PPi依赖的Pi摄取。Pi摄取呈线性增加，直至孔外Pi 20 mM。Bafilomycin;一种特异性的张力质体H +- atp酶抑制剂也能抑制张力质体对Pi的摄取。所有这些数据都表明Pi可能是在膜电位的驱动下通过细胞质转运的。由于胞浆H^+- atp酶是一个重要因素，我们进一步分析胞浆H^+- atp酶的氧化还原控制。我们还使用分离的Chara节间细胞测量了Pi在质膜上的传输网络与tonoplst之间的关系。

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 f or 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 inorganic ion metabolisms in plant cells by means of physiology to molecular biology.Last year, we have measured Pi uptake of isolated barley mesophyll vacuoles. Unfortunately, Pi uptake activity of barley vacuole is not high. Thus, we have tried to measure the Pi uptake activity of suspension cultured cells of Catharanthus roseus. These cells are known to have high activities of Pi uptake in both the plasma membrane and the tonoplast. As well as barley, Catharanthus vacuoles showed both ATP and PPi dependent Pi uptake. Pi uptake lineally increased until 20 mM extravacuolar Pi. Bafilomycin ; a specific inhibitor of the tonoplast H^+-ATPase also inhibited Pi uptake across the tonoplast. All these data suggested that Pi might be transported across the tonoplast driven by the membrane potential. Since the tonoplast H^+-ATPase is an important factor, we further analyzed the redox control of the tonoplast H^+-ATPase.We are also measuring the relationship between Pi transport network across the plasma membrane and the tonoplst using isolated Chara internodal cells.