Transcription study of the genes encoded in the region of the junction between the large single copy and the inverted repeat A of spinach chloroplast DNA.

The expression of the psbA, trnH-GUG and rps19' genes from spinach chloroplasts, coding respectively for the 32 kDa protein, the tRNA(His) (GUG), and the putative ribosomal protein CS19', has been studied by cloning, Northern hybridization and 3' and 5' S1 mapping experiments.It is demonstrated that the putative transcription termination signal of the psbA gene does not function as a rho-independent terminator of transcription in E. coli, whatever its orientation.Evidence is presented suggesting that, in spinach, the psbA and trnH-GUG genes are probably cotranscribed. The 3'-OH extremities of transcripts observed downstream from the putative psbA terminator are interpreted as resulting from processing of the psbA precursor.Using different approaches, it is shown that the rps19' gene, located on the other strand and overlapping the trnH-GUG gene, is not expressed.