Structure and transcription of the spinach chloroplast rDNA leader region

Abstract

A cloned fragment of spinach cholorplast DNA carrying 140 bp of the 16S rRNA gene and 691 bp upstream this gene has been analysed by DNA sequencing, by in vitro transcription, by S1 mapping with chloroplast RNAs and purified 16S rRNA from 30S ribosomal subunits. A tRNA_Val gene has been located between the position 394 and 465. Crude chloroplast RNA polymerase has been purified by heparin sepharose chromatography of a 80 000 g supernatant from pure lysed spinach plastids and used to transcribe the cloned Bgl II-Pvu II DNA fragment. Four in vitro transcripts of about 830, 550, 350 and 260 bases were obtained whatever RNA polymerase used: the chloroplast or the E. coli enzyme. The transcripts of 550 and 260 bases are initiated by ATP.