Inouhe M, Ito R, Ito S, Sasada N, Tohoyama H, Joho M
Department of Biology and Earth Science, Faculty of Science, Ehime University, Matsuyama, Ehime, 790-8577, Japan.
Plant Physiol. 2000 Jul;123(3):1029-36. doi: 10.1104/pp.123.3.1029.
Suspension-cultured cells of azuki bean (Vigna angularis) as well as the original root tissues were hypersensitive to Cd (<10 microM). Repeated subculturings with a sublethal level of Cd (1-10 microM) did not affect the subsequent response of cells to inhibitory levels of Cd (10-100 microM). The azuki bean cells challenged to Cd did not contain phytochelatin (PC) peptides, unlike tomato (Lycopersicon esculentum) cells that have a substantial tolerance to Cd (>100 microM). Both of the cell suspensions contained a similar level of reduced glutathione (GSH) when grown in the absence of Cd. Externally applied GSH to azuki bean cells recovered neither Cd tolerance nor PC synthesis of the cells. Furthermore, enzyme assays in vitro revealed that the protein extracts of azuki bean cells had no activity converting GSH to PCs, unlike tomato. These results suggest that azuki bean cells are lacking in the PC synthase activity per se, hence being Cd hypersensitive. We concluded that the PC synthase has an important role in Cd tolerance of suspension-cultured cells.
赤豆（Vigna angularis）的悬浮培养细胞以及原始根组织对镉（<10微摩尔）高度敏感。用亚致死水平的镉（1 - 10微摩尔）进行反复传代培养，并不影响细胞随后对抑制水平镉（10 - 100微摩尔）的反应。与对镉具有显著耐受性（>100微摩尔）的番茄（Lycopersicon esculentum）细胞不同，受到镉挑战的赤豆细胞不含植物螯合肽（PC）。在无镉条件下生长时，两种细胞悬浮液中的还原型谷胱甘肽（GSH）水平相似。向赤豆细胞外部施加GSH既不能恢复细胞对镉的耐受性，也不能恢复细胞的PC合成。此外，体外酶分析表明，与番茄不同，赤豆细胞的蛋白质提取物没有将GSH转化为PC的活性。这些结果表明，赤豆细胞本身缺乏PC合酶活性，因此对镉高度敏感。我们得出结论，PC合酶在悬浮培养细胞对镉的耐受性中起重要作用。
