Zhou Ying, Cai Hongmei, Xiao Jinghua, Li Xianghua, Zhang Qifa, Lian Xingming
National Center of Plant Gene Research, Huazhong Agricultural University, Wuhan, China.
Theor Appl Genet. 2009 May;118(7):1381-90. doi: 10.1007/s00122-009-0988-3. Epub 2009 Mar 4.
Aspartate aminotransferase (AAT) is a key enzyme in the synthesis of amino acids. It plays an important role in regulating carbon and nitrogen metabolism in almost all organisms. In this study, we over-expressed in rice separately all three AAT genes from rice (OsAAT1~3) and one AAT gene from Escherichia coli (EcAAT). Over-expression was driven by the CaMV 35S promoter and constructs were introduced into rice by Agrobacterium tumefaciens-mediated transformation. Compared with control plants, the transformants showed significantly increased leaf AAT activity and greater seed amino acid and protein contents. No other phenotypic changes were observed. The total leaf AAT activities in plants over-expressing OsAAT1, OsAAT2, and EcAAT were 26.6, 23.6, and 19.6 A min(-1) mg(-1) FW (A: units of activity, defined as increase of absorbency per min per mg; FW: fresh weight), which were significantly higher than that in the wild-type control (17.7 A min(-1) mg(-1) FW). The amino acid content in seeds of transgenic plants over-expressing OsAAT1, OsAAT2, and EcAAT was 119.36, 115.36, and 113.72 mg g(-1), respectively, which were 16.1, 12.0, and 5.4% higher, respectively, than that in the control plants. The transgenic plants over-expressing OsAAT1, OsAAT2, and EcAAT had significantly higher protein contents (increased 22.2, 21.1, and 11.1%, respectively) than wild-type plants. No significant changes were found in leaf AAT activity, seed amino acid content or protein content in OsAAT3 over-expressed plants. The expression patterns of the three OsAAT genes and their different functions are also discussed.
天冬氨酸转氨酶（AAT）是氨基酸合成中的关键酶。它在几乎所有生物体的碳和氮代谢调节中发挥着重要作用。在本研究中，我们分别在水稻中过表达了来自水稻的所有三个AAT基因（OsAAT1~3）和来自大肠杆菌的一个AAT基因（EcAAT）。过表达由CaMV 35S启动子驱动，并通过根癌农杆菌介导的转化将构建体导入水稻。与对照植株相比，转基因植株的叶片AAT活性显著增加，种子氨基酸和蛋白质含量更高。未观察到其他表型变化。过表达OsAAT1、OsAAT2和EcAAT的植株叶片总AAT活性分别为每毫克鲜重26.6、23.6和19.6 A分钟-1（A：活性单位，定义为每分钟每毫克吸光度的增加；FW：鲜重），显著高于野生型对照（17.7 A分钟-1毫克-1 FW）。过表达OsAAT1、OsAAT2和EcAAT的转基因植株种子中的氨基酸含量分别为119.36、115.36和113.72毫克克-1，分别比对照植株高16.1%、12.0%和5.4%。过表达OsAAT1、OsAAT2和EcAAT的转基因植株的蛋白质含量显著高于野生型植株（分别增加22.2%、21.1%和11.1%）。过表达OsAAT3的植株叶片AAT活性、种子氨基酸含量或蛋白质含量未发现显著变化。还讨论了三个OsAAT基因及其不同功能的表达模式。
