阿拉伯芥CuZnSOD生理功能之研究

Abstract

超氧歧化?(Superoxide dismutase; SOD)是一群含金屬的酵素，依其所含金屬不同可分為三類：FeSOD、MnSOD及CuZnSOD，其功能是清除超氧自由基。阿拉伯芥之CuZnSOD至少有三個同功?，各分佈於細胞質、葉綠體及過氧化體。本論文利用基因轉殖技術將阿拉伯芥細胞質型CuZnSOD (CSD1)轉殖於阿拉伯芥植株，得到7株預期CuZnSOD活性提高之T1轉殖株（ACZ1系列），經蛋白質電泳分析SOD活性，這些轉殖株之CuZnSOD活性增加量並未如預期大量提高。另外CuZnSOD活性下降之T1轉殖株32株，其中8株是利用反轉譯股方式得到（ACZ1a系列）、其餘24株則是利用RNAi方式產生（ACZ1i系列），其CuZnSOD活性下降由0-78％不等。觀察野生型、轉殖株及CZ5（實驗室已有之轉殖株，含水稻細胞質型CuZnSOD, SOD總活性可提高約2.7倍），發現CuZnSOD活性下降之轉殖株（ACZ1i，ACZ1a）的果莢較短、種子數目較少。另外利用CuZnSOD活性不同之轉植株（ACZ1i系列、CZ5及野生型）進行凍害逆境處理（-3℃），測量其Fv/Fm可反應光合作用效率，做為凍害耐受性指標，處理前與處理後Fv/Fm變化值顯示提高阿拉伯芥葉片CuZnSOD活性可增加阿拉伯芥葉片對凍害耐受性。

Superoxide dismutase (SOD) is a metalloprotein and function as free radical scavenger. Depend on the bounded metal, SOD can be divided into FeSOD, CuZnSOD and MnSOD. There are three CuZnSOD isozymes in Arabidopsis thaliana and distribute in various location of cells, including cytosol, chloroplast and peroxisome. In order to determine the role of CuZnSOD in plant reproductive stage and freezing tolerance, we generated 7 overexpression (ACZ1) and 32 CuZnSOD reduction transformants by the Agrobacterium-mediated transformation method. Within these 32 transgenic plants, 8 are generated by antisense method (ACZ1a) and the other 24 are by RNAi method (ACZli). Comparing with the wild type, cytosolic CuZnSOD activities in ACZ1 transformants do not significantly increase. However, in ACZ1a and ACZli decrease 0-78%. The length of siliques and the seed number per siliques of ACZ1a and ACZli are shorter and fewer than these of wild type. To further observe the effect of the CuZnSOD activity in freezing tolerance, freezing treatment (-3℃) is imposed to wild type, ACZli and CZ5 plants. Photosynthesis efficiency showed by Fv/Fm value of each plant is taken as the freezing tolerance indicator. The result suggests that the higher CuZnSOD activity transformants have higher freezing tolerance.