Chloroplast protein translocon components atToc159 and atToc33 are not essential for chloroplast biogenesis in guard cells and root cells.
Chloroplast protein translocon components atToc159 and atToc33 are not essential for chloroplast biogenesis in guard cells and root cells.
复制标题
叶绿体蛋白易位子成分 atToc159 和 atToc33 对于保卫细胞和根细胞中的叶绿体生物发生不是必需的。
作者：
Tien;Hsou
蛋白质进入叶绿体是由位于叶绿体被膜上的蛋白质输入装置介导的。以往的研究结果表明，拟南芥中可能存在多个输入复合体。为了进一步了解这种多样性的性质，我们分析了拟南芥ppi1和ppi2突变体，它们分别是atToc33和atToc159易位蛋白的零突变体。在ppi2突变体中，保卫细胞中的叶绿体中仍含有淀粉颗粒和类囊体膜，而叶肉细胞中的叶绿体与叶肉细胞中的叶绿体不同。两个突变体的根叶绿体形态与野生型相似。经过长时间的光照处理，突变体和野生型的根质体分化为叶绿体。酶活性测定表明，叶绿体中的一种酶活性仅在叶中降低，而在根中没有。这些结果表明，ppi1和ppi2突变体都具有功能根和保卫细胞体。因此，我们认为进口复合体是细胞类型特异性的，而不是底物或叶绿体特异性的。
Protein import into chloroplasts is mediated by a protein import apparatus located in the chloroplast envelope. Previous results indicate that there may be multiple import complexes in Arabidopsis. To gain further insight into the nature of this multiplicity, we analyzed the Arabidopsis ppi1 and ppi2 mutants, which are null mutants of the atToc33 and atToc159 translocon proteins, respectively. In the ppi2 mutant, in contrast to the extremely defective plastids in mesophyll cells, chloroplasts in guard cells still contained starch granules and thylakoid membranes. The morphology of root plastids in both mutants was similar to that in wild type. After prolonged light treatments, root plastids of both mutants and the wild type differentiated into chloroplasts. Enzymatic assays indicated that the activity of a plastid enzyme was reduced only in leaves but not in roots. These results indicated that both the ppi1 and ppi2 mutants had functional root and guard cell plastids. Therefore, we propose that import complexes are cell type specific rather than substrate or plastid specific.