Abstract
Some nuclear tRNA genes from Eucarya and Archaea contain introns. Pre-tRNA introns are cleaved by the successive reaction of three enzymes: an endonuclease (Sen), an tRNA ligase (tRL) and a 2'-phosphotransferase (Pt). In plants, only two kinds of nuclear tRNA genes for tRNATyr and tRNAMet are interrupted by introns. Using a GFP reporter fused with genes encoding the subunits of plant Sen (Sen1 and Sen2), tRL and Pt from rice or Arabidopsis, the subcellular location of these splicing proteins was examined. Transient expression of these fusion genes in the onion cells or bean guard cells showed that both Sen proteins are mainly located in the nucleus, but mitochondrial location was also observed. Surprisingly, the same assay revealed that tRL and Pt mainly located in the chloroplast (plastid). These results suggest the possibilities not only of cytosolic tRNA splicing in plants but also of unknown function(s) of splicing enzymes in chloroplast.
