SYNTHESIS OF CHLOROPLAST HIGH-MOLECULAR-WEIGHT RIBOSOMAL RIBONUCLEIC-ACID IN SPINACH

Illuminated suspensions of chloroplasts isolated from young spinach leaves show incorporation of [3H]uridine into several species of RNA. One such RNA species of Mr 2.7 × 106 shows sequence homology with both the chloroplast 23‐S rRNA (Mr= 1.05 × 106) and 16‐S rRNA (Mr= 0.56 × 106), as judged by DNA/RNA competition hybridization. Leaves labelled in vivo with [32P]orthophosphate in the presence of chloramphenicol accumulate labelled RNAs of Mr 1.28 × 106, 0.71/0.75 × 106 and 0.47 × 106. The 1.28 × 106‐Mr RNA shows 80.5% sequence homology with the 1.05 × 106‐Mr rRNA and the 0.71/0.75 × 106‐Mr RNA mixture shows 76% sequence homology with the 0.56 × 106‐Mr rRNA. We conclude that the pathway of rRNA maturation in spinach chloroplasts is similar to that of Escherichia coli. Copyright © 1979, Wiley Blackwell. All rights reserved