Kobayashi Isao, Fujiwara Shoko, Saegusa Hirotaka, Inouhe Masahiro, Matsumoto Hiroko, Tsuzuki Mikio
School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
Mar Biotechnol (NY). 2006 Jan-Feb;8(1):94-101. doi: 10.1007/s10126-005-5092-3. Epub 2006 Jan 1.
In most photosynthetic organisms, inorganic arsenic taken up into the cells inhibits photosynthesis and cellular growth. In a green alga, Chlamydomonas reinhardtii, 0.5 mM arsenate inhibited photosynthesis almost completely within 30 min. However, in cells acclimated with a sublethal concentration (0.05 to 0.1 mM) of Cd, the inhibition of photosynthesis at 30 min after the addition of arsenate was relieved by more than 50%. The concentrations of arsenic incorporated into the cells were not significantly different between the Cd-acclimated and the non-acclimated cells. The Cd-acclimated cells accumulated Cd and synthesized phytochelatin (PC) peptides, which are known to play an important role in detoxification of heavy metals in plants. By the addition of an inhibitor of glutathione (an intermediate in the PC biosynthetic pathway) biosynthesis, buthionine sulfoximine, cells lost not only Cd tolerance but also arsenate tolerance. These results suggest that glutathione and/or PCs synthesized in Cd-acclimated cells are involved in mechanisms of arsenate tolerance.
在大多数光合生物中，细胞吸收的无机砷会抑制光合作用和细胞生长。在绿藻莱茵衣藻中，0.5 mM的砷酸盐在30分钟内几乎完全抑制了光合作用。然而，在用亚致死浓度（0.05至0.1 mM）的镉驯化的细胞中，添加砷酸盐30分钟后光合作用的抑制减轻了50%以上。镉驯化细胞和未驯化细胞中摄入的砷浓度没有显著差异。镉驯化细胞积累镉并合成植物螯合肽（PC），已知其在植物重金属解毒中起重要作用。通过添加谷胱甘肽（PC生物合成途径中的中间体）生物合成抑制剂丁硫氨酸亚砜胺，细胞不仅失去了对镉的耐受性，也失去了对砷酸盐的耐受性。这些结果表明，镉驯化细胞中合成的谷胱甘肽和/或PC参与了砷酸盐耐受机制。
