Gualberto J M, Lamattina L, Bonnard G, Weil J H, Grienenberger J M
Institut de Biologie Moléculaire des Plantes du CNRS, Université Louis Pasteur, Strasbourg, France.
Nature. 1989 Oct 19;341(6243):660-2. doi: 10.1038/341660a0.
RNA editing is a process that results in the production of a messenger RNA with nucleotide sequences that differ from those of the template DNA, and provides another mechanism for modulating gene expression. The phenomenon was initially described in the mitochondria of protozoa. Here we report that RNA editing is also required for the correct expression of plant mitochondrial genes. It has previously been proposed that in plant mitochondria there is a departure from the universal genetic code, with CGG specifying tryptophan instead of arginine. This was because CGG codons are often found in plant mitochondrial genes at positions corresponding to those encoding conserved tryptophans in other organisms. We have now found, however, wheat mitochondrial gene sequences containing C residues that are edited to U residues in the corresponding mRNA sequences. In this way, CGG codons can be changed to UGG codons in the mRNA so that tryptophan may be encoded according to the universal genetic code. Furthermore, for each codon modification resulting from a C----U conversion that we studied, we found a corresponding change in the amino acid that was encoded. RNA editing in wheat mitochondria can thus maintain genetic information at the RNA level and as a result contribute to the conservation of mitochondrial protein sequences among plants.
RNA编辑是一个产生信使RNA的过程，其核苷酸序列不同于模板DNA的核苷酸序列，并提供了另一种调节基因表达的机制。这种现象最初是在原生动物的线粒体中被描述的。在此我们报告，RNA编辑对于植物线粒体基因的正确表达也是必需的。此前曾有人提出，在植物线粒体中存在对通用遗传密码的偏离，即CGG编码色氨酸而非精氨酸。这是因为CGG密码子在植物线粒体基因中常常出现在与其他生物体中编码保守色氨酸的密码子相对应的位置。然而，我们现在发现，小麦线粒体基因序列中的C残基在相应的mRNA序列中被编辑为U残基。通过这种方式，mRNA中的CGG密码子可以变为UGG密码子，从而使色氨酸能够按照通用遗传密码进行编码。此外，对于我们研究的每一个由C到U转换导致的密码子修饰，我们都发现了所编码氨基酸的相应变化。因此，小麦线粒体中的RNA编辑能够在RNA水平上维持遗传信息，并进而有助于植物间线粒体蛋白质序列的保守性。
