Processing of mono-, di- and tricistronic transfer RNAs precursors in a spinach or pea chloroplast soluble extract.

Monomeric, dimeric and trimeric chloroplast tRNA precursors from Euglena gracilis were synthesized by Sp6, T7 or T3 RNA polymerases using an in vitro transcription system. The length of the 3' and 5' ends of these precursors was varied to facilitate the identification of processing intermediates, and to study the effect of the structure of the tRNA precursors on the processing reactions. All the tRNA precursors studied, independent of their structure, are processed to mature tRNAs in both spinach and pea chloroplast soluble extracts. 5'-and 3' endonucleases are involved in the cleavage of 5' and 3' ends of the pre-tRNAs. These two reactions are not ordered in vitro. Other enzymatic activities can be detected in the chloroplast soluble extract including exonucleases, and CCA-adding enzyme.