Cell-type-specific expression of genes encoding subunits of plant mitochindrail ATP synthase and their coordiantion

植物线粒体F_1-ATP酶由α、β、γ、δ、δ ′和γ 6个亚基组成。除了由线粒体基因组编码的α以外的亚单位由核基因编码。我们从甘薯（Ipomoea batatas）或其近缘野生种（Ipomoea trifida）中分离了sigma'和sigma'亚基的核基因，并测定了它们的核苷酸序列。与sigma亚基类似，这些亚基由基因组中的多个基因编码。sigma'亚基的核基因含有一个内含子，这两个基因的外显子几乎完全相同。另一方面，来自两个基因的σ亚基的外显子的核苷酸序列彼此仅81.6%相同。我们构建了融合基因，其中来自δ亚基的两个核基因的启动子片段（已被预先表征）与GUS编码序列融合。这些融合基因在所有检查的器官中均表现出组成型表达。对融合基因表达的组织化学检测表明，融合基因在富含植物细胞的叶和茎的韧皮部组织中表达最强。两个融合基因在根中的表达水平差异显著。此外，在烟草转化细胞悬浮培养过程中，两种启动子的融合基因表达量也有显著差异。这些结果表明，F_1 ATP酶核亚基的多个基因受到不同的调控。

F_1-ATPase of plant mitochondria is composed of six subunits of alpha, beta, gamma, delta, delta', and epsilon. Subunits other than alpha, that is encoded by mitochondrial genome, are encoded by nuclear genes. We have isolated nuclear genes for sigma' and epsilon subunits from sweet potato(Ipomoea batatas) or closely related wild specied (Ipomoea trifida), and determined their nucleotide sequences. Similar the the sigma subunit, these subunits were encoded by multiple genes in the genome. Nuclear genes for the sigma' subunit contained one intron, and exons of these two genes were almost identical to each other. On the other hand, nucleotide sequences of exons from two genes for the sigma subunit were only 81.6% identical to each other. We constructed fusion genes in which promoter fragments from two nuclear genes for the delta subunits, that had been characterixed proviously, were fused to the GUS coding sequence. These fusion genes showed constitutive expression in all of the organs examined. Histochemical examination of expression of fusion genes revealed tha their expression was most strong in phloem tissues of leaves and stems that contain mitochondria-enriched compoanion cells. Between the two fusion genes, the level of expression in roots differed significantly. Futhermore, expression of the fusion gene during the growth of transformed cells of tobacco in suspension culture was also significantly different between the two promoters. These results suggested that multiple genes for nuclear subunits of F_1 ATPase are regulated differently.