Pea chloroplast tRNALys (UUU) gene: transcription and analysis of an intron-containing gene

The pea chloroplast trnK gene which encodes tRNALys (UUU) was sequenced. TrnK is located 210 bp upstream from the promoter of psbA and immediately downstream from the 3′-end of rbcL. The gene is transcribed from the same DNA strand as psbA and rbcL. A 2447 bp intron with class II features is located in the trnK anticodon loop. The intron contains a 506 amino acid open reading frame which could encode an RNA maturase. The primary transcript of trnK is 2.9 kb long; its 5′-end was identified as a site of transcription initiation by in vitro transcription experiments. The 5′-terminus is adjacent to DNA sequences previously identified as transcription promoter elements. The most abundant trnK transcript is 2.5 kb long with termini corresponding to the 5′ and 3′ ends of the trnK exons. Intron specific RNAs were not detected. This suggests that RNA processing which produces tRNALys leads to rapid degradation of intron sequences.