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

点击翻译按钮获取中文摘要

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.