Glover K E, Spencer D F, Gray M W
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada.
J Biol Chem. 2001 Jan 5;276(1):639-48. doi: 10.1074/jbc.M007708200.
Despite its large size (200-2400 kilobase pairs), the mitochondrial genome of angiosperms does not encode the minimal set of tRNAs required to support mitochondrial protein synthesis. Here we report the identification of cytosolic-like tRNAs in wheat mitochondria using a method involving quantitative hybridization to distinguish among three tRNA classes: (i) those encoded by mitochondrial DNA (mtDNA) and localized in mitochondria, (ii) those encoded by nuclear DNA and located in the cytosol, and (iii) those encoded by nuclear DNA and found in both the cytosol and mitochondria. The latter class comprises tRNA species that are considered to be imported into mitochondria to compensate for the deficiency of mtDNA-encoded tRNAs. In a comprehensive survey of the wheat mitochondrial tRNA population, we identified 14 such imported tRNAs, the structural characterization of which is presented here. These imported tRNAs complement 16 mtDNA-encoded tRNAs, for a total of at least 30 distinct tRNA species in wheat mitochondria. Considering differences in the set of mtDNA-encoded and imported tRNAs in the mitochondria of various land plants, the import system must be able to adapt relatively rapidly over evolutionary time with regard to the particular cytosolic-like tRNAs that are brought into mitochondria.
尽管被子植物的线粒体基因组很大（200 - 2400千碱基对），但其并不编码支持线粒体蛋白质合成所需的最小tRNA集合。在此，我们报告了利用一种涉及定量杂交的方法在小麦线粒体中鉴定出类似胞质的tRNA，该方法可区分三类tRNA：（i）由线粒体DNA（mtDNA）编码并定位于线粒体中的tRNA；（ii）由核DNA编码并位于胞质溶胶中的tRNA；（iii）由核DNA编码且在胞质溶胶和线粒体中均存在的tRNA。后一类包含被认为导入线粒体以补偿mtDNA编码tRNA不足的tRNA种类。在对小麦线粒体tRNA群体的全面调查中，我们鉴定出了14种此类导入的tRNA，本文展示了其结构特征。这些导入的tRNA补充了16种由mtDNA编码的tRNA，使得小麦线粒体中总共至少有30种不同的tRNA种类。考虑到不同陆地植物线粒体中mtDNA编码和导入的tRNA集合存在差异，在进化过程中，导入系统必须能够相对快速地适应导入线粒体的特定类似胞质的tRNA。
