Regulation of expression of genes coding for subunits of plant mitochondrial F1-ATPase

双子叶植物线粒体F1-ATP酶由6个亚基组成，除α亚基由线粒体基因编码外，其余均由核基因编码。我们先前已经通过纯化和cDNA克隆鉴定了甘薯线粒体的γ、δ、δ ′和γ ′四个小亚基中的每一个与其他生物体的F1-ATPase亚基的对应关系。本研究首次从植物来源中分离到甘薯线粒体F1-ATPase亚基的核基因。对于每个亚基，鉴定并分离出多个核基因，它们在外显子部分具有高度的序列同源性。δ亚基的两个基因DAM 1和DAM 2的5 '上游区域含有另一个基因中不存在的两个插入序列。将这两个基因的5 '上游区域与GUS融合基因在转化的烟草细胞和转基因烟草植株中表达，结果表明这两个基因都是活跃转录的基因。但两个GUS融合基因的表达水平和表达模式不同。虽然DAM 1基因中Ins-1插入序列的缺失显着提高了转化细胞中的表达水平，但它对转基因烟草植株中的表达没有表现出任何明显的影响。DAM 2-GUS融合基因在转基因植物根中的高水平表达可能是由于DAM 2基因远上游区域存在Ins-2序列或其他独特序列。

Mitochondrial F1-ATPase from dicotyledonous plants constitutes of 6 subunits and they are encoded by nuclear genes except for the alpha subunit which is encoded by the mitochondrial gene. We have previously identified correspondence of each of the four minor subunits of gamma, delta, delta'and epsilon from sweet potato mitochondria to subunits of F1-ATPase from other organisms by purification and cDNA cloning. In this research project, we could isolate nuclear genes for minor subunits of sweet potato mitochondrial F1-ATPase for the first time from the plant origin. For each of the subunts, multiple nuclear genes were identified and isolated, which shared high degree of sequence homology in the exon parts. The 5'-upstream regions of two genes for the delta subunit, DAM1 and DAM2, contained two insersion sequences that are absent in the other gene. Both of the GUS fusion genes with the 5'-upstream regions of these two genes were expressed in transformed tobacco cells and in transgenic tobacco plants, the results suggesting that both genes are actively transcribed genes. However, the level of GUS expression and the pattern of gene expression were different between the two GUS fusion genes. Although deletion of the Ins-1 insersion sequence in the DAM1 gene significantly enhanced the level of expression in transformed cells, it did not show any obvious effects on the expression in transgenic tobacco plants. The high-level expression of the DAM2-GUS fusion gene in roots of transgenic plants seemed to be due to the presence of Ins-2 sequence or other unique sequence in the far upstream region of the DAM2 gene.