Abstract
Only two nuclear genes encoding tRNATyr and tRNAMet-e are interrupted by introns in higher plants. Pre-tRNA splicing requires the concerted action of three enzymes, i.e., endonuclease (Sen), tRNA ligase (RL) and 2'-phosphotransferase (Pt), in yeast cells and plants. We have investigated the subcellular localization of these enzymes. The results showed that the enzymes are all localized predominantly in the nucleus. RL and Pt, both containing chloroplast transit signals at the N-termini, were also targeted to the chloroplasts. Because eukaryotic nuclear tRNA splicing system is completely different from the splicing in the plant organelles, RL and Pt may play a special role in these compartments. In order to investigate a role of RL in plants, we have constructed Ti plasmid vectors to express functional and mutated RL in nucleus and chloroplast or exclusively in chloroplast in the plant cells, respectively. Transgenic rice plants over-expressing these genes independently are being produced to explore its effect on plant phenotype and repair of chloroplastic tRNAs under stress conditions.
