Investigation of novel function of plant nuclear tRNA splicing enzymes that are localized in organelle

植物核基因编码tRNA^&lt；Tyr&gt；和tRNA^&lt；Met-e&gt；被内含子打断。前体tRNAs的剪接发生在细胞核内。然而，参与tRNA 5‘-和3’-一半连接的tRNA连接酶也定位于叶绿体中。为了评估tRNA连接酶对叶绿体tRNAs的修复作用的可能性，显性负性烟草突变体tRNA连接酶基因在连接酶区域发生氨基酸替换而过表达。野生型和突变型植物都受到氧化胁迫，并从这些植物中提取总tRNA。使用特定的tRNA探针进行Northern分析，确定细胞质和叶绿体中完整的和切割的tRNA的比例。结果表明，在10 mM H_2O_2条件下，胞质tRNAs被切割，但野生型和突变型植物叶绿体tRNAs的完整/降解比率没有显著差异。

Plant nuclear genes encoding tRNA^<Tyr> and tRNA^<Met-e> are interrupted by introns. Splicing of precursor tRNAs is occurred in nucleus. However, tRNA ligase involved in ligation of 5'- and 3'- half of tRNA is localized in chloroplast as well. In order to evaluate the possibility that tRNA ligase plays as a role of repair on chloroplast tRNAs, dominant-negative tobacco mutant where a mutated tRNA ligase gene with amino acid substitution in the ligase domain is over-expressed. Wild-type and mutant plants were both subjected to oxidative stress and total tRNAs were extracted from these plants. Ratios of intact to cleaved tRNAs from cytoplasm and chloroplast were determined with northern analysis using specific tRNA probes. Results showed that several of cytosolic tRNAs are cleaved with the condition of 10mM H_2O_2, but there no significant difference of ratios of intact to degrading chloroplast tRNAs between wild-type and mutated plants.